ALBERT

Notes: Garnet-whole rock Sm-Nd data are presented for several samples from the Indian plate in the NW Himalaya. These dates, when combined with the P-T evolution of the Indian plate rocks, allow a thorough reconstruction of the prograde thermal evolution of this region (including the Nanga Parbat Haramosh Massif) during the early Cenozoic. Combining these data with Rb-Sr mineral separate ages, enables us to constrain the post-peak cooling history of this region of the Himalaya.The data presented here indicate that the upper structural levels of the cover rocks of the Nanga Parbat Haramosh Massif, and similar rocks in the Kaghan Valley to the south-west, were buried to pressures of c. 10 kbar and heated to temperatures of c. 650 °C at 46–41 Ma. The burial of the lower structural levels of the cover rocks of the Nanga Parbat Haramosh Massif, to similar depths but at higher temperatures of c. 700 °C, occurred slightly later at 40–36 Ma, synchronous with the imbrication and exhumation of the amphibolite- and eclogite-grade rocks of the Kaghan Valley. In contrast, the cover rocks of the Nanga Parbat Haramosh Massif were not imbricated or exhumed at this time, remaining buried beneath the Kohistan-Ladakh Island Arc until the syntaxis-forming event that occurred in the last 10 Myr. The timing of tectonic events in the north-western Himalaya differs from that experienced by the rocks of the Central Himalaya in that the earliest stage of burial in the NW Himalaya predates that of the Central Himalaya by c. 6 Myr. This difference may result from the diachronous nature of the Indo-Asian collision or may simply be a reflection of differing timing at different structural levels.

Notes: SHRIMP U–Pb dating and laser ablation ICP-MS trace element analyses of zircon from four eclogite samples from the north-western Dabie Mountains, central China, provide evidence for two eclogite facies metamorphic events. Three samples from the Huwan shear zone yield indistinguishable late Carboniferous metamorphic ages of 312 ± 5, 307 ± 4 and 311 ± 17 Ma, with a mean age of 309 ± 3 Ma. One sample from the Hong'an Group, 1 km south of the shear zone yields a late Triassic age of 232 ± 10 Ma, similar to the age of ultra-high pressure (UHP) metamorphism in the east Qinling–Dabie orogenic belt. REE and other trace element compositions of the zircon from two of the Huwan samples indicate metamorphic zircon growth in the presence of garnet but not plagioclase, namely in the eclogite facies, an interpretation supported by the presence of garnet, omphacite and phengite inclusions. Zircon also grew during later retrogression. Zircon cores from the Huwan shear zone have Ordovician to Devonian (440–350 Ma) ages, flat to steep heavy-REE patterns, negative Eu anomalies, and in some cases plagioclase inclusions, indicative of derivation from North China Block igneous and low pressure metamorphic source rocks. Cores from Hong'an Group zircon are Neoproterozoic (780–610 Ma), consistent with derivation from the South China Block. In the western Dabie Mountains, the first stage of the collision between the North and South China Blocks took place in the Carboniferous along a suture north of the Huwan shear zone. The major Triassic continent–continent collision occurred along a suture at the southern boundary of the shear zone. The first collision produced local eclogite facies metamorphism in the Huwan shear zone. The second produced widespread eclogite facies metamorphism throughout the Dabie Mountains–Sulu terrane and a lower grade overprint in the shear zone.

Notes: Sodic metapelites with jadeite, chloritoid, glaucophane and lawsonite form a coherent regional metamorphic sequence, several tens of square kilometres in size, and over a kilometre thick, in the Orhaneli region of northwest Turkey. The low-variance mineral assemblage in the sodic metapelites is quartz + phengite + jadeite + glaucophane + chloritoid + lawsonite. The associated metabasites are characterized by sodic amphibole + lawsonite ± garnet paragenesis. The stable coexistence of jadeite + chloritoid + glaucophane + lawsonite, not reported before, indicates metamorphic pressures of 24 ± 3 kbar and temperatures of 430 ± 30  °C for the peak blueschist facies conditions. These P–T conditions correspond to a geotherm of 5  °C km−1, one of the lowest recorded in continental crustal rocks. The low geotherm, and the known rate of convergence during the Cretaceous subduction suggest low shear stresses at the top of the downgoing continental slab.

Notes: SHRIMP U–Pb ages have been obtained for zircon in granitic gneisses from the aureole of the Rogaland anorthosite–norite intrusive complex, both from the ultrahigh temperature (UHT; 〉900 °C pigeonite-in) zone and from outside the hypersthene-in isograd. Magmatic and metamorphic segments of composite zircon were characterised on the basis of electron backscattered electron and cathodoluminescence images plus trace element analysis. A sample from outside the UHT zone has magmatic cores with an age of 1034 ± 7 Ma (2σ, n = 8) and 1052 ± 5 Ma (1σ, n = 1) overgrown by M1 metamorphic rims giving ages between 1020 ± 7 and 1007 ± 5 Ma. In contrast, samples from the UHT zone exhibit four major age groups: (1) magmatic cores yielding ages over 1500 Ma (2) magmatic cores giving ages of 1034 ± 13 Ma (2σ, n = 4) and 1056 ± 10 Ma (1σ, n = 1) (3) metamorphic overgrowths ranging in age between 1017 ± 6 Ma and 992 ± 7 Ma (1σ) corresponding to the regional M1 Sveconorwegian granulite facies metamorphism, and (4) overgrowths corresponding to M2 UHT contact metamorphism giving values of 922 ± 14 Ma (2σ, n = 6). Recrystallized areas in zircon from both areas define a further age group at 974 ± 13 Ma (2σ, n = 4). This study presents the first evidence from Rogaland for new growth of zircon resulting from UHT contact metamorphism. More importantly, it shows the survival of magmatic and regional metamorphic zircon relics in rocks that experienced a thermal overprint of c. 950 °C for at least 1 Myr. Magmatic and different metamorphic zones in the same zircon are sharply bounded and preserve original crystallization age information, a result inconsistent with some experimental data on Pb diffusion in zircon which predict measurable Pb diffusion under such conditions. The implication is that resetting of zircon ages by diffusion during M2 was negligible in these dry granulite facies rocks. Imaging and Th/U–Y systematics indicate that the main processes affecting zircon were dissolution-reprecipitation in a closed system and solid-state recrystallization during and soon after M1.

Notes: O, Sr and C isotopes from east-central Vermont are used to provide information on the timing and volume of metamorphic fluid flow. The results are then used to assess the evidence for redox transformations between C species. Oxygen profiles are homogenised on a metre scale; comparison with Sr isotopes suggest that O alteration may have occurred over a significantly larger timescale than that of Sr, possibly because O was modified during dewatering and diagenesis in addition to the high temperature alteration recorded by strontium. Sr isotope distributions are consistent with cross-layer fluid fluxes of 104−106 moles m−2; absolute values depend on the Sr fluid-rock distribution coefficient which is poorly known; however, reaction progress constraints suggest that fluxes were towards the lower end of this range. High δ13C values observed at lithological boundaries cannot be explained by volume loss or closed system processes and are taken to indicate reductive precipitation of graphite as a result of mixing between CO2 and CH4-bearing fluids. Mass balance calculations indicate that redox reactions occurring under metamorphic conditions convert a minimum of 10% of the CO2 released from limestones into graphite, thus providing a potentially important control on the average residence time of C within the crust with implications for C cycling models.

Notes: Prograde P–T paths recorded by the chemistry of minerals of subduction-related metamorphic rocks allow inference of tectonic processes at convergent margins. This paper elucidates the changing P–T conditions during garnet growth in pelitic schists of the Sambagawa metamorphic belt, which is a subduction related metamorphic belt in the south-western part of Japan. Three types of chemical zoning patterns were observed in garnet: Ca-rich normal zoning, Ca-poor normal zoning and intrasectoral zoning. Petrological studies indicate that normally-zoned garnet grains grew keeping surface chemical equilibrium with the matrix, in the stable mineral assemblage of garnet + muscovite + chlorite + plagioclase + paragonite + epidote + quartz ± biotite. Pressure and temperature histories were inversely calculated from the normally-zoned garnet in this assemblage, applying the differential thermodynamic method (Gibbs' method) with the latest available thermodynamic data set for minerals. The deduced P–T paths indicate slight increase of temperature with increasing pressure throughout garnet growth, having an average dP/dT of 0.4–0.5 GPa/100 °C. Garnet started growing at around 470 °C and 0.6 GPa to achieve the thermal and baric peak condition near the rim (520 °C, 0.9 GPa). The high-temperature condition at relatively low pressure (for subduction related metamorphism) suggests that heating occurred before or simultaneously with subduction.

Notes: The Schistes Lustrés (SL) suture zone occupies a key position in the Alpine chain between the high-pressure (HP) Brianconnais domain and the ultrahigh-pressure (UHP) Dora Maira massif, and reached subduction depths ranging from c. 40–65 km (Cottian Alps). In order to constrain the timing of HP metamorphism and subsequent exhumation, several phengite generations were differentiated, on the basis of habit, texture, paragenesis and chemistry, as belonging to the first or second exhumation episode, respectively, D2 or D3, or to earlier stages of the tectono-metamorphic evolution. Ten carefully selected samples showing D2, D3 (D2 + D3), or earlier (mostly peak temperature) phengite population(s) were subjected to laser probe 40Ar/39Ar analysis. The data support the results of the petrostructural study with two distinct age groups (crystallization ages) for D2 and D3 phengite, at 51–45 and 38–35 Ma, respectively. The data also reveal a coherent age cluster, at 62–55 Ma, for peak temperature phengite associated with chloritoid which were preserved in low strain domains. The age of the D3 event in the SL complex appears very similar to ages recently obtained for greenschist facies deformation on the border of most internal crystalline massifs. Exhumation rates of the order of 1–2 mm yr−1 are obtained for the SL complex, which are compatible with velocities documented for accretionary wedge settings. Similarly, cooling velocities are only moderate (c.5 °C Myr−1), which is at variance with recent estimates in the nearby UHP massifs.

Notes: Three periods of mineral growth and three generations of spiral-shaped inclusion trails have been distinguished within folded rocks of the Qinling-Dabie Orogen, China, using the development of three successive and differently trending sets of foliation intersection axes preserved in porphyroblasts (FIAs). This progression is revealed by the consistent relative sequence of changes in FIA trends from the core to rim of garnet porphyroblasts in samples with multiple FIAs. The first and second formed sets of FIAs trend oblique to the axial planes of macroscopic folds that dominate the outcrop pattern in this region. The porphyroblasts containing these FIAs grew prior to the development of the macroscopic folds, yet the FIAs do not change orientation across the fold hinges. The youngest formed FIAs (set 3) lie subparallel to the axial planes of these folds and the porphyroblasts containing these FIAs formed in part as the folds developed. The deformation associated with all three generations of spiral-shaped inclusion trails in garnet porphyroblasts involved the formation of subhorizontal and subvertical foliations against porphyroblast rims accompanied by periods of garnet growth; pervasive structures have not necessarily formed in the matrix away from the porphyroblasts. The macroscopic folds are heterogeneously strained from limb to limb, doubly plunging and have moderately dipping axial planes. The consistent orientation of Set 1 FIAs indicates that the development of spiral-shaped inclusion trails in porphyroblasts with FIAs belonging to Set 2 did not involve rotation of the previously formed porphyroblasts. The consistent orientation of Sets 1 and 2 FIAs indicate that the development of spiral-shaped inclusion trails in porphyroblasts with FIAs belonging to Set 3 did not involve rotation of the previously formed porphyroblasts during folding. This requires a fold mechanism of progressive bulk inhomogeneous shortening and demonstrates that spiral-shaped inclusion trails can form outside of shear zones.

Notes: The grain-scale spatial arrangement of melt in layer-parallel leucosomes in two anatectic rocks from two different contact aureoles located in central Maine, USA, is documented and used to constrain the controls on grain-scale melt localization. The spatial distribution of grain-scale melt is inferred from microstructural criteria for recognition of mineral pseudomorphs after melt and mineral grains of the solid matrix that hosted the melt. In both rocks, feldspar mimics the grain-scale distribution of melt, and quartz is the major constituent of the solid matrix. The feldspar pockets consist of individual feldspar grains or aggregates of feldspar grains that show cuspate outlines. They have low average width/length ratios (0.54 and 0.55, respectively), and are interstitial between more rounded and equant (width/length ratios 0.65 for both samples) quartz grains. In two dimensions, the feldspar pockets extend over distances equivalent to multiple quartz grain diameters, possibly forming a connected three-dimensional intergranular network. Both samples show similar mesoscopic structural elements and in both samples the feldspar pockets have a shape-preferred orientation. In one sample, feldspar inferred to replace melt is aligned subparallel to the shape-preferred orientation of quartz, indicating that pre- or syn-anatectic strain controlled the grain-scale distribution of melt. In the other sample, the preferred orientation of feldspar inferred to replace melt is different from the orientations of all other mesoscopic or microscopic structures in the rock, indicating that differential stress controlled grain-scale melt localization. This is probably facilitated by conditions of higher differential stress, which may have promoted microfracturing. Grain-scale melt distribution and inferred melt localization controls give insight into possible grain-scale deformation mechanisms in melt-bearing rocks. Application of these results to the interpretation of deep crustal anatectic rocks suggests that grain-scale melt distribution should be controlled primarily by pre- or syn-anatectic deformation. Feedback relations between melt localization and deformation are to be expected, with important implications for deformation and tectonic evolution of melt-bearing rocks.

Notes: A metamorphic field gradient has been investigated in the Moldanubian zone of the central European Variscides encompassing, from base to the top, a staurolite–kyanite zone, a muscovite–sillimanite zone, a K-feldspar–sillimanite zone, and a K-feldspar–cordierite zone, respectively. The observed reaction textures in the anatectic metapsammopelites of the higher grade zones are fully compatible with experimental data and petrogenetic grids that are based on fluid-absent melting reactions. From structural and microstructural observations it can be concluded that the boundary between the kyanite–staurolite zone and the muscovite- and K-feldspar–sillimanite zones coincides with an important switch in deformation mechanism(s). Besides minor syn-anatectic shearing (melt-enhanced deformation), microstructural criteria point (a) to a switch in deformation mechanism from rotation recrystallization (climb-accommodated dislocation creep) to prism slip and high-temperature (fast) grain boundary migration in quartz (b) to the activity of diffusion creep in quartz–feldspar layers, and (c) to accommodation of strain by intense shearing in fibrolite–biotite layers. It is suggested that any combination of these deformation mechanisms will profoundly affect the rheological characteristics of high-grade metamorphic rocks and significantly lower rock strength. Hence, the boundary between these zones marks a major rheological barrier in the investigated cross section and probably also in other low- to medium-pressure/high-temperature areas. At still higher metamorphic grades (K-feldspar-cordierite zone), where the rheologically critical melt percentage is reached, rock rheology is mainly governed by the melt and other deformation mechanisms are of minor importance. In the study area, the switch in deformation mechanism(s) is responsible for large-scale strain partitioning and concentration of deformation within the higher-temperature hanging wall during top-to-the-S thrusting, thus preserving a more complete petrostructural record within the rocks of the footwall including indications for a ?Devonian high- to medium-pressure/medium-temperature metamorphic event. Thrusting is accompanied by diapiric ascent of diatexites of the K-feldspar-cordierite zone and infolding of the footwall, suggesting local crustal overturn in this part of the Moldanubian zone.

Notes: This paper presents the results of numerical modelling to investigate the regional occurrence of prehnite-bearing metamorphic rocks at shallow levels in subduction zones. The modelling assumes a simple geometrical configuration in which the thermal structure in a prism is controlled by boundary conditions at the top and base of the prism. It is expected that the predominant metamorphic facies in a prism will change with decreasing age of the descending slab. The results of thermal modelling show that the facies boundary between pumpellyite–actinolite and prehnite–actinolite facies (including prehnite–pumpellyite facies) overlaps with an array of P–T conditions in the prism when the age of a descending slab is younger than 10 Myr. This implies that the change of the predominant metamorphic facies from pumpellyite–actinolite to prehnite–actinolite facies will switch drastically. The critical age of the switch depends on subduction parameters. In particular, the critical age of the descending slab is 〈5 Myr in the case of no shear heating, with a subduction rate of v=75–200 mm y−1 and subduction angle of θ=5–15°. For shear heating (constant shear stress=30 MPa) with a subduction rate of v=75 mm y−1 and subduction angle of θ=10° the critical age is 7 Myr. To test this switching behaviour in the development of prehnite–actinolite facies in the prism, petrologic data from the Cretaceous Shimanto Accretionary Complex (CSAC) in Kyushu, Japan were compiled. The regional occurrence and mineral assemblages of prehnite-bearing metamorphic rocks suggest that the most of CSAC was metamorphosed under prehnite–actinolite facies. This conclusion is consistent with subduction of a young, hot slab, as has been proposed based on other geological observations. This suggests that the regional extent of the prehnite–actinolite facies metamorphic rocks may be a unique evidence for the subduction of a young, hot slab.

Notes: Fluid compositions and bedding-scale patterns of fluid flow during contact metamorphism of the Weeks Formation in the Notch Peak aureole, Utah, were determined from mineralogy and stable isotope compositions. The Weeks Formation contains calc-silicate and nearly pure carbonate layers that are interbedded on centimetre to decimetre scales. The prograde metamorphic sequence is characterized by the appearance of phlogopite, diopside, and wollastonite. By accounting for the solution properties of Fe, it is shown that the tremolite stability field was very narrow and perhaps absent in the prograde sequence. Unshifted oxygen and carbon isotopic ratios in calcite and silicate minerals at all grades, except above the wollastonite isograd, show that there was little to no infiltration of disequilibrium fluids. The fluid composition is poorly constrained, but X(CO2)fluid must have been 〉0.1, as indicated by the absence of talc, and has probably increased with progress of decarbonation reactions.The occurrence of scapolite and oxidation of graphite in calc-silicate beds of the upper diopside zone provide the first evidence for limited infiltration of external aqueous fluids. Significantly larger amounts of aqueous fluid infiltrated the wollastonite zone. The aqueous fluids are recorded by the presence of vesuvianite, large decreases in δ18O values of silicate minerals from c. 16‰ in the diopside zone to c. 10‰ in the wollastonite zone, and extensive oxidation of graphite. The carbonate beds interacted with the fluids only along margins where graphite was destroyed, calcite coarsened, and isotopic ratios shifted.The wollastonite isograd represents a boundary between a high aqueous fluid-flux region on its higher-grade side and a low fluid-flux region on its lower-grade side. Preferential flow of aqueous fluids within the wollastonite zone was promoted by permeability created by the wollastonite-forming reaction and the natural tendency of fluids to flow upward and down-temperature near the intrusion-wall rock contact.

Notes: Cordierite H2O and CO2 volatile saturation surfaces derived from recent experimental studies are presented for P–T conditions relevant to high-grade metamorphism and used to evaluate fluid conditions attending partial melting and granulite formation. The volatile saturation surfaces and saturation isopleths for both H2O and CO2 in cordierite are strongly pressure dependent. In contrast, the uptake of H2O by cordierite in equilibrium with melts formed through biotite dehydration melting, controlled by the distribution of H2O between granitic melt and cordierite, Dw[Dw = wt% H2O (melt)/wt% H2O(Crd)], is mainly temperature dependent. Dw = 2.5–6.0 for the H2O contents (0.4–1.6 wt percentage) typical of cordierite formed through biotite dehydration melting at 3–7 kbar and 725–900 °C. This range in Dw causes a 15–30% relative decrease in the total wt% of melt produced from pelites. Cordierite in S-type granites are H2O-rich (1.3–1.9 wt%) and close to or saturated in total volatiles, signifying equilibration with crystallizing melts that achieved saturation in H2O. In contrast, the lower H2O contents (0.6–1.2 wt percentage) preserved in cordierite from many granulite and contact migmatite terranes are consistent with fluid-absent conditions during anatexis. In several cases, including the Cooma migmatites and Broken Hill granulites, the cordierite volatile compositions yield aH2O values (0.15–0.4) and melt H2O contents (2.2–4.4 wt%) compatible with model dehydration melting reactions. In contrast, H2O leakage is indicated for cordierite from Prydz Bay, Antarctica that preserve H2O contents (0.5–0.3 wt%) which are significantly less than those required (1.0–0.8 wt%) for equilibrium with melt at conditions of 6 kbar and 860 °C. The CO2 contents of cordierite in migmatites range from negligible (〈 0.1 wt%) to high (0.5–1.0 wt%), and bear no simple relationship to preserved cordierite H2O contents and aH2O. In most cases the cordierite volatile contents yield total calculated fluid activities (aH2O + aCO2) that are significantly less than those required for fluid saturation at the P–T conditions of their formation. Whether this reflects fluid absence, dilution of H2O and CO2 by other components, or leakage of H2O from cordierite is an issue that must be evaluated on a case-by-case basis.

Notes: Chemically zoned porphyroblasts in metamorphic rocks indicate that diffusional processes could not maintain equilibrium conditions on a grain scale during porphyroblast growth or establish it afterwards. An effect of this inability to maintain equilibrium is the progressive removal of elements forming garnet cores from any metamorphic reaction that occurs at the porphyroblast boundaries or in the matrix of the rock. To examine this effect on mineral assemblages, the Bence–Albee matrix correction was applied to X-ray intensity maps collected using eclogite samples from northern New Caledonia in order to determine the chemical composition of all parts of the sample. The manipulation of these element maps allows a quantitative analysis of the fractionation of the bulk rock composition between garnet cores and the matrix. A series of calculated equilibrium-volume compositions represents the change in matrix chemistry with progressive elemental fractionation as a consequence of prograde garnet growth under high-P conditions. Pressure–temperature pseudosections are calculated for these compositions, in the CaO–Na2O–FeO–MgO–Al2O3–SiO2–H2O system. Assemblages, modal proportions and mineral textures observed in the New Caledonian eclogites can be closely modelled by progressively ‘removing’ elements forming garnet cores from the bulk rock composition. The pseudosections demonstrate how chemical fractionation effects the peak metamorphic assemblage, prograde textures and the development of retrograde assemblages.

Notes: Quartz–sillimanite segregations, quartz–albite lithologies (Ab95–98), and Kiruna-type low-Ti iron-oxide deposits are associated with late- to post-tectonic (c. 1055 Ma) leucogranites of Lyon Mountain Gneiss (LMG) in the Adirondack Mountains, New York State. Most recent interpretations of these controversial features, which are global in occurrence, favour hydrothermal origins in agreement with results presented here.Field relations document that quartz–sillimanite veins and nodules cut, and therefore post-date, emplacement of host LMG leucogranites. Veins occur in oriented fracture networks, and aligned trains of nodules are interpreted as disrupted early veins. Late dykes of leucogranite cut veins and nodules demonstrating formation prior to terminal magmatism. Veins and nodules consist of sillimanite surrounded by quartz that commonly embays wall-rock feldspar indicating leaching of Na and K from LMG feldspar by acidic hydrothermal fluids. Subsequent, and repeated, ductile flow disrupted earlier veins into nodular fragments but produced little grain shape fabric.Geochemical and petrographic studies of quartz–albite rock indicate that it formed through metasomatic replacement (albitization) of LMG microperthite by sodic hydrothermal fluids that resulted in diagnostic checkerboard albite. Low-Ti iron-oxide ores are commonly associated with the quartz–albite sub-unit, and it is proposed that hydrothermal fluids related to albitization transported Fe as well. The regional extent of sodic alteration suggests large quantities of surface-derived hydrothermal fluids. Fluid inclusion and oxygen isotope data are consistent with high temperature, regionally extensive fluids consisting primarily of evolved surface-derived brines enriched in Na and Cl. Quartz–sillimanite veins and nodules, which are significantly more localised phenomena and require acidic fluids, were most likely formed from local magmatic fluids in the crystallizing carapaces of LMG plutons.

Notes: Rocks of the Snake Creek Anticline are mainly pelitic schists, psammitic schists and quartzites that were metamorphosed during multiple high-T/low-P events extending from D1 to D5, with the metamorphic peak occurring late to post-D3. Albitites are widespread, but are concentrated in five areas. They are typically fine- to medium-grained, and consist of albite, with or without combinations of quartz, biotite, staurolite, cordierite, garnet, andalusite, sillimanite, kyanite, gedrite and tourmaline. From the presence or absence of albite inclusions in porphyroblasts, the albitites are interpreted as forming early in the D3 event as a result of infiltration of external fluids. Psammitic schists and quartzites were preferentially altered, but pelitic schists were also albitized in localities where the alteration was more extreme, with the replacement of muscovite total and the replacement of quartz and biotite variable. Structural controls on albitization include fracturing and syn-D3 shear zones in fold hinges. Biotite schists with abundant porphyroblasts (combinations of staurolite, garnet, andalusite and cordierite) occur adjacent to albitites, and it is argued that they formed by the addition of Fe and Mg sourced from the albitites. In several albitite-rich areas, cordierite grew early in D3 and was partly or entirely replaced during or after D3 by combinations of biotite, andalusite, tourmaline, staurolite and sillimanite. A postulated P–T–d path involved an increase in pressure (with or without a decrease in temperature) subsequent to early D3 albitization, followed by an increase in temperature up to the metamorphic peak (late D3 to early D4. The metamorphism was contemporary in part with the emplacement of the Williams Batholith (c. 1550–1500 Ma), which probably supplied the Na-rich fluids.

Notes: Andalusite–staurolite–biotite hornfels metamorphosed beneath the mafic layered rocks of the Bushveld Complex, South Africa, preserves a detailed record of the relative timing of porphyroblast growth and metamorphic reactions. The sequence inferred from microstructures shows considerable overlap of the period of growth of porphyroblasts of staurolite, cordierite, biotite and andalusite, and the persistence over a similar interval of the reactant porphyroblastic phase chloritoid. This is inconsistent with calculations of equilibrium phase relations, and implies that disequilibrium processes controlled the prograde reaction sequence, despite the slow heating rates involved (1 °C per 10 000 yr). The early appearance of cordierite by a metastable reaction and its subsequent disappearance indicates that delayed nucleation of porphyroblastic phases, rather than simply sluggish reaction, is required to account for the sequence of growth. The predicted reactions for the first appearance of andalusite and staurolite have low entropy of reaction, and do not occur until they have been overtaken in terms of reaction affinity by high-entropy devolatilisation reactions involving the breakdown of chlorite. Once the porphyroblasts have nucleated, metastable chloritoid-breakdown reactions also contribute to their growth. The implied magnitude of the critical overstepping for andalusite nucleation is around 5 kJ mole−1 (equivalent to 40 °C for the chlorite-breakdown reaction), and that for other phases is expected to decrease in the order andalusite〉staurolite〉cordierite. Coupling between nucleation rate, crystal growth rates and the resulting grain size distribution suggests that the rate constants of natural reactions are at least an order of magnitude lower than those measured in the laboratory. Pseudomorphs after chloritoid and cordierite conserve volume but not Al or other species of low mobility, suggesting a breakdown mechanism controlled by an interface process such as the slow dissolution of the refractory porphyroblast phase, rather than by a transport step.

Notes: Fe-rich metapelitic granulites of the Musgrave Block, central Australia, contain several symplectic and coronal reaction textures that post-date a peak S2 metamorphic assemblage involving garnet, sillimanite, spinel, ilmenite, K-feldspar and quartz. The earliest reaction textures involve spinel- and quartz-bearing symplectites that enclose garnet and to a lesser extent sillimanite. The symplectic spinel and quartz are in places separated by later garnet and/or sillimanite coronas. The metamorphic effects of a later, D3, event are restricted to zones of moderate to high strain where a metamorphic assemblage of garnet, sillimanite, K-feldspar, magnetite, ilmenite, quartz and biotite is preserved. Quantitative mineral equilibria calculations in the system K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3 (KFMASHTO) using Thermocalc 3.0 and the accompanying internally consistent dataset provide important constraints on the influence of TiO2 and Fe2O3 on biotite-bearing and spinel-bearing equilibria, respectively. Biotite-bearing equilibria are shifted to higher temperatures and spinel-bearing equilibria to higher pressures and lower temperatures in comparison to the equivalent equilibria in K2O–FeO–MgO–Al2O3–SiO2–H2O (KFMASH). The sequence of reaction textures involving spinel is consistent with a D2 P–T path that involved a small amount of decompression followed predominantly by cooling within a single mineral assemblage stability field. Thus, the reaction textures reflect changes in modal proportions within an equilibrium assemblage rather than the crossing of a univariant reaction. The D3 metamorphic assemblage is consistent with lower temperatures than those inferred for D2.

Notes: In the contact aureole of the Oligocene granodiorite of Cima di Vila, granitic pegmatites of Variscan age were strongly deformed during eo-Alpine regional metamorphism, with local development of ultramylonites. In the ultramylonite matrix, consisting of quartz, plagioclase, muscovite and biotite, microstructures show grain growth of quartz within quartz ribbons, and development of decussate arrangements of mica. These features indicate that dynamic recrystallization related to mylonite development was followed by extensive static growth during contact metamorphism. K-feldspar porphyroclasts up to 1.5 cm are mantled by myrmekite that forms a continuous corona with thickness of about 1 mm. In both XZ and YZ sections, myrmekite tubules are undeformed, and symmetrically distributed in the corona, and oligoclase-andesine hosts have random crystallographic orientation. Myrmekite development has been modelled from the P–T–t evolution of the ultramylonites, assuming that the development of the ultramylonites occurred during eo-Alpine metamorphism at c. 450 °C, 7.5 kbar, followed by contact metamorphism at c. 530 °C, 2.75 kbar. Phase diagram pseudosections calculated from the measured bulk composition of granitic pegmatite protolith indicate that the equilibrium assemblage changes from Qtz–Phe–Ab ± Zo ± Cpx ± Kfs during the ultramylonite stage to Qtz–Pl(An30–40)–Ms–Kfs–Bt(Ann55) during the contact metamorphic stage. The thermodynamic prediction of increasing plagioclase mode and anorthite content, change of white mica composition and growth of biotite, occurring during the end of the heating path, are in agreement with the observed microstructures and analysed phase compositions of ultramylonites. Along with microstructural evidence, this supports the model that K-feldspar replacement by myrmekite took place under static conditions, and was coeval with the static growth accompanying contact metamorphism. Myrmekite associated with muscovite can develop under prograde (up-temperature) conditions in granites involved in polymetamorphism.

Notes: Crustal thermal regimes are sensitive to both the amount and distribution of heat producing elements (HPEs). Since a significant proportion of the crustal complement of HPEs is contained within granites, granite generation and emplacement should lead to significant long-term changes in the thermal structure of the crust. Using HPE concentrations appropriate to representative Australian Proterozoic granites we show that granite segregation leads to changes in the temperature field of the crust of up to c. 50 °C, producing long-term cooling in the source regions and heating at emplacement levels, relative to the pre-granite conductive thermal regime. Because of the intimate connection between thermal regime and lithospheric strength, granite-assisted redistribution of HPEs is likely to be fundamental to cratonisation.

Notes: Coupled thermal-mechanical models are used to investigate interactions between metamorphism, deformation and exhumation in large convergent orogens, and the implications of coupling and feedback between these processes for observed structural and metamorphic styles. The models involve subduction of suborogenic mantle lithosphere, large amounts of convergence (≥ 450 km) at 1 cm yr−1, and a slope-dependent erosion rate. The model crust is layered with respect to thermal and rheological properties — the upper crust (0–20 km) follows a wet quartzite flow law, with heat production of 2.0 μW m−3, and the lower crust (20–35 km) follows a modified dry diabase flow law, with heat production of 0.75 μW m−3. After 45 Myr, the model orogens develop crustal thicknesses of the order of 60 km, with lower crustal temperatures in excess of 700 °C. In some models, an additional increment of weakening is introduced so that the effective viscosity decreases to 1019 Pa.s at 700 °C in the upper crust and 900 °C in the lower crust. In these models, a narrow zone of outward channel flow develops at the base of the weak upper crustal layer where T≥600 °C. The channel flow zone is characterised by a reversal in velocity direction on the pro-side of the system, and is driven by a depth-dependent pressure gradient that is facilitated by the development of a temperature-dependent low viscosity horizon in the mid-crust. Different exhumation styles produce contrasting effects on models with channel flow zones. Post-convergent crustal extension leads to thinning in the orogenic core and a corresponding zone of shortening and thrust-related exhumation on the flanks. Velocities in the pro-side channel flow zone are enhanced but the channel itself is not exhumed. In contrast, exhumation resulting from erosion that is focused on the pro-side flank of the plateau leads to ‘ductile extrusion’ of the channel flow zone. The exhumed channel displays apparent normal-sense offset at its upper boundary, reverse-sense offset at its lower boundary, and an ‘inverted’ metamorphic sequence across the zone. The different styles of exhumation produce contrasting peak grade profiles across the model surfaces. However, P–T–t paths in both cases are loops where Pmax precedes Tmax, typical of regional metamorphism; individual paths are not diagnostic of either the thickening or the exhumation mechanism. Possible natural examples of the channel flow zones produced in these models include the Main Central Thrust zone of the Himalayas and the Muskoka domain of the western Grenville orogen.

Notes: Mid-crustal Archean pelitic granulites in the Vredefort Dome experienced a static, low-P granulite facies overprint associated with the formation of the dome by meteorite impact at 2.02 Ga. Heating and exhumation were virtually instantaneous, with the main source of heat being provided by energy released from nonadiabatic decay of the impact shock wave. Maximum temperatures within a radius of a few kilometres of the centre of the structure exceeded 900 °C and locally even exceeded 1350 °C. This led to comprehensive melting of the precursor Archean granulite assemblages (Grt + Bt + Qtz + Pl + Ksp ± Crd ± Opx ± Sil) followed by peritectic crystallization of aluminous alkali feldspar+Crd + Spl ± Crn ± Sil parageneses and the segregation of small, evolved, biotite leucogranite bodies. However, at a distance of c. 6 km from the centre pre-impact rock features are largely preserved, although partial replacement of garnet by symplectitic coronas of Crd + Opx ± Spl ± Pl and biotite by orthopyroxene indicate that peak temperatures approached 775 ± 50 °C. Thin interstitial moats of K-feldspar are closely associated with the orthopyroxene coronas; they are interpreted as the remnants of low-proportion partial melts generated by biotite breakdown. Both the textures and mineral compositional data support reduced equilibration volumes in these rocks, which reflect rapid isobaric cooling following shock heating and exhumation. The high temperatures and strong lateral thermal gradient are consistent with the modelled impact-induced isotherm pattern for a 200–300 km diameter impact crater.

Notes: The transformation from smectite to chlorite has been interpreted as involving either a disequilibrium chlorite/smectite mixed-layering sequence, or an equilibrated discontinuous sequence involving smectite–corrensite–chlorite. Here, analysis of the smectite to chlorite transition in different geothermal systems leads us to propose that the transformation proceeds via three contrasting reaction pathways involving (i) a continuous mixed-layer chlorite/smectite series; (ii) a discontinuous smectite–corrensite–chlorite series and (iii) a direct smectite to chlorite transition. Such contrasting pathways are not in accord with an equilibrium mineral reaction series, suggesting that these pathways record kinetically controlled reaction progress. In the geothermal systems reviewed the style of reaction pathway and degree of reaction progress is closely correlated with intensity of recrystallization, and not to differences in thermal gradients or clay grain size. This suggests a kinetic effect linked to variation in fluid/rock ratios and/or a contrast between advective or diffusive fluid transport. The mode of fluid transport provides a means by which the rates of dissolution/nucleation/growth can control the reaction style and the reaction progress of the smectite to chlorite transition. Slow rates of growth are linked to the first reaction pathway involving mixed-layering, while increasing rates of growth, relative to nucleation, promote the generation of more ordered structures and ultimately lead to the direct smectite to chlorite transition, representative of the third pathway.

Notes: The Cooma Complex of the Lachlan Fold Belt, south-eastern Australia, is characterised by a large (c. 10 km wide) low-P, high-T metamorphic aureole surrounding a small (3 × 6 km) granite pluton. The aureole extends northward to envelop the eastern lobe of the Murrumbidgee Batholith and progressively narrows to a kilometre wide hornfelsic aureole some 50 km north of Cooma. At its northern extremity, the batholith has intruded its own volcanic cover. These regional relations suggest that the Murrumbidgee Batholith is gently tilted to the north, with the Cooma Complex representing the aureole beneath the batholith.Two main deformation events, D3 and D5, affected the aureole. The inner, high-grade migmatitic domain contains upright F5 folds defined by a composite, transposed S3/S0 fabric and S3/S0 concordant leucosomes. The folded stromatic migmatites define the western limb of a F5 synform, with its axis located in the batholith. Lenses and sheets of the Murrumbidgee Batholith intruded along S3 but also preserve S3 as a strong, solid-state foliation. S3 and the granite sheets but are also folded by F5, outlining a fanning positive flower structure. These relations indicate that most of the batholith was emplaced before and during D3, but intrusion persisted until early syn-D5.Formation of the Cooma Granodiorite occurred post-D3 to early syn-D5, after formation of the wide metamorphic aureole during early syn-D3 to early syn-D5. The Murrumbidgee Batholith was emplaced between pre-D3 to early syn-D5, synchronous with the formation of the Cooma Complex. The structural and metamorphic relations indicate that the Murrumbidgee Batholith was the ultimate heat source responsible for the Cooma Metamorphic Complex.D3 structures and metamorphic isograds are subparallel to the batholith margin for over 50 km. This concordance probably extends vertically, suggesting that the isograds also fan outward from the batholith margin. This implies an inverted metamorphic sequence focused on the Murrumbidgee Batholith, although the base has been almost completely removed by erosion in the Cooma Complex. The field evidence at Cooma, combined with previous thermal modelling results, suggest that extensive LPHT metamorphic terranes may represent regional metamorphic aureoles developed beneath high-level granitic batholiths.

Notes: This Special Issue is in celebration of the career contribution of Ron Vernon. It arises from the ‘Ron Vernon Symposium’, which was held as part of the 15th Australian Geological Convention in Sydney in 2000. To date Ron has published more than one hundred scientific papers, several books and contributed widely to international conferences. He is the doyen in the multidisciplinary field of microstructures, which spans petrology and structural geology. However, Ron's range is phenomenal, and he has contributed to many aspects of metamorphism, magmatism and rock deformation. He has drawn on data from his work in these areas to contribute widely to understanding thermal regimes, crustal evolution and tectonics, as exemplified by his ideas about HTLP metamorphism and emplacement of granites. Ron has followed the scientific method in his work; it has led him to many innovative interpretations, some of which undermined established dogma. By example, Ron has been a positive role model for the younger generation. However, for the older generation, he has been something of a bête noire! The papers in this Special Issue cover the range from low- to high-grade metamorphism, from metasomatism to melting, from microstructures to tectonics, and from fieldwork to experiments. It is our hope that in reading them you will take time to think about what has been achieved in the past 40 years, and use this as motivation for what remains to be done.

Notes: Many migmatites and granulites preserve evidence of a clockwise P–T evolution involving decompression (decrease in P) while close to the thermal peak. The extent of post-thermal peak reaction is influenced by several factors, including: (1) the P–T path in relation to invariants in the system and the Clapeyron slopes of the equilibria; (2) the rate of cooling; and (3) the availability of fluid (H2O-rich volatile phase or melt) for fluid-consuming reactions. Reaction may occur between products of a prograde (increasing T) fluid-generating reaction as the same equilibrium is re-crossed in the retrograde (decreasing T) sense. In general, reaction reversal or ‘back reaction’ requires the P–T path to approximate isobaric heating and cooling, without significant decompression, and evolved fluid to remain within the equilibration volume. The larger the decompression segment in the P–T evolution, the more chance there is of crossing different reactions along the retrograde segment from those crossed along the prograde segment. For common pelite compositions, we may generalize by considering three pressure regimes separated by the [Spl, Ms, H2O] invariant in KFMASH (approximately 9 kbar) and the intersection of muscovite breakdown with the H2O-rich volatile phase-saturated solidus (approximately 4 kbar). Reaction reversal cannot occur along P–T paths that traverse around one of these points, but may occur along P–T paths confined to one of the three regimes in between. Additionally, above the solidus, melt segregation and loss potentially change the composition of the equilibration volume; and, the size of the equilibration volume shrinks with decreasing T. Since the proportion of melt to residue in the equilibration volume may change with decreasing size, the composition of the equilibration volume may change throughout the supra-solidus part of the retrograde segment of the P–T evolution. If melt has been lost from the equilibration volume, reaction reversal may not be possible or may be only partial; indeed, the common preservation of close-to-peak mineral assemblages in migmatite and granulite demonstrates that extensive reaction with melt is uncommon, which implies melt isolation or loss prior to crossing potential melt-consuming reactions. Water dissolved in melt is transported through the crust to be exsolved on crystallization at the solidus appropriate to the intrinsic a(H2O). This recycled water causes retrogression at subsolidus conditions. Consideration of the evidence for supra-solidus decompression-dehydration reactions, and review of microstructures that have proven controversial, such as corona and related microstructures, selvage microstructures and ‘late’ muscovite, leads to the conclusion that there is more than one way for these microstructures to form and reminds us that we should always consider multiple working hypotheses!

Notes: The reaction muscovite+cordierite→biotite+Al2SiO5 +quartz+H2O is of considerable importance in the low pressure metamorphism of pelitic rocks: (1) its operation is implied in the widespread assemblage Ms + Crd +And± Sil + Bt + Qtz, a common mineral assemblage in contact aureoles and low pressure regional terranes; (2) it is potentially an important equilibrium for pressure estimation in low pressure assemblages lacking garnet; and (3) it has been used to distinguish between clockwise and anticlockwise P–T paths in low pressure metamorphic settings. Experiments and thermodynamic databases provide conflicting constraints on the slope and position of the reaction, with most thermodynamic databases predicting a positive slope for the reaction. Evidence from mineral assemblages and microtextures from a large number of natural prograde sequences, in particular contact aureoles, is most consistent with a negative slope (andalusite and/or sillimanite occurs upgrade of, and may show evidence for replacement of, cordierite). Mineral compositional trends as a function of grade are variable but taken as a whole are more consistent with a negative slope than a positive slope. Thermodynamic modelling of reaction 1 and associated equilibria results in a low pressure metapelitic petrogenetic grid in the system K2O–FeO–MgO–Al2O3–SiO2–H2O (KFMASH) which satisfies most of the natural and experimental constraints. Contouring of the Fe–Mg divariant interval represented by reaction 1 allows for pressure estimation in garnet-absent andalusite+cordierite-bearing schists and hornfelses. The revised topology of reaction 1 allows for improved analysis of P–T paths from mineral assemblage sequences and microtextures in the same rocks.

Notes: An evaluation was made of the development of two experimental plots where restoration of dominant riparian plant species was conducted in December 1991 along two semiarid Mediterranean summer-dry watercourses. An overall comparison was made of the vegetation structure, species cover, floral composition, and species richness of the plots restored using vegetation from nearby undisturbed plots along the same watercourse. The monitoring was performed in October 1993, October 1995, September 1997, and October 1999. In the restored zones previously rooted cuttings of the species most representative of these communities were planted, using the undisturbed zones as vegetation models. Climatological conditions (particularly the rainfall regime during the planting period) substantially favored the success of the planting establishment. The results show that a simple planting technique accompanied by monitoring during the first year is adequate to achieve success in establishment of planting species. It is necessary to take precautions against herbivory of small plants of Chamaerops humilis, Ficus carica, and Retama sphaerocarpa. The planting itself causes some disturbance in the soil that may alter the species composition, giving an advantage to ruderal species over others. More time is needed to attain coverage, frequency, and species composition comparable with that of undisturbed zones.

Notes: Exotic species have become increasingly significant management problems in parks and reserves and frequently complicate restoration projects. At the same time there may be circumstances in which their removal may have unforeseen negative consequences or their use in restoration is desirable. We review the types of effects exotic species may have that are important during restoration and suggest research that could increase our ability to set realistic management goals. Their control and use may be controversial; therefore we advocate consideration of exotic species in the greater context of community structure and succession and emphasize areas where ecological research could bring insight to management dilemmas surrounding exotic species and restoration. For example, an understanding of the potential transience of exotics in a site and the role particular exotics might play in changing processes that influence the course of succession is essential to setting removal priorities and realistic management goals. Likewise, a greater understanding of the ecological role of introduced species might help to reduce controversy surrounding their purposeful use in restoration. Here we link generalizations emerging from the invasion ecology literature with practical restoration concerns, including circumstances when it is practical to use exotic species in restoration.

Notes: Pine forests of southeastern United States have been burned primarily in the dormant season to accomplish silvicultural objectives, but with increased emphasis on ecosystem restoration fires are now prescribed in other seasons. We observed fire behavior during both growing season and dormant season prescribed fires in shortleaf pine (Pinus echinata) stands managed as pine–grassland communities for the endangered Red-cockaded Woodpecker (Picoides borealis). Fuel beds for dormant season fires were characterized by lower amounts of live fuels, higher amounts of 1-hr time lag fuel and a greater total fuel load than growing season fires. Fuel consumption and percent of the total fuels consumed was greater in dormant season fires than in growing season fires. Fireline intensity, heat per unit area, reaction intensity, and rate of spread were greater in dormant season fires than in growing season fires. Lower fire intensity in growing season fires was possibly a function of lower amounts of 1-hr time lag fuels, higher amounts of live herbaceous fuels, and possibly a less porous fuel bed. Additionally, growing season fires had lower heat per unit area and reaction intensity and slower rates of spread. The Keetch-Byram drought index (KBDI) did not provide a good index for potential fire behavior on our drought-prone sandy loam soils. KBDI during growing season fires averaged over four times greater than during dormant season fires, but fire intensity was greater in dormant season fires. Low KBDI values may be misleading and give a false sense of security for dormant season fire prescriptions on sandy loam soils because the duff layer may dry more quickly as a result of inherent low water holding capacity. High KBDI values may result in prescribed burns being canceled because of conditions that are erroneously perceived to be outside the prescription window. We caution against over-reliance on KBDI as a determining factor for conducting prescribed burns on areas with sandy or sandy loam soils.

Notes: We describe the changes in the floral assemblage in a salt marsh after reconnection to estuarine tidal inundation. The Elk River marsh in Grays Harbor, Washington was opened to tidal flushing in 1987 after being diked for approximately 70 years. The freshwater pasture assemblage dominated by Phalarais arundinacea (reed canary grass) converted to low salt marsh vegetation within 5 years, with the major flux in species occurring between years 1 and 4. The system continued to develop through the 11-year post-breach monitoring period, although change after year 6 was slower than in previous years. The assemblage resembles a low salt marsh community dominated by Distichlis spicata (salt grass) and Salicornia virginica (pickleweed). Because of subsidence of the system during the period of breaching, the restored system remains substantially different from the Deschamsia cespitosa (tufted hairgrass)-dominated reference marsh. Use of a similarity index to compare between years and also between reference and restored marshes in the same year revealed that similarity in floral composition between year 0 and subsequent years decreased with time. However, there was a period of dramatic dissimilarity during years 1 to 3 when the system was rapidly changing from a freshwater to estuarine condition. Similarity values between the reference and restored system generally increased with time. Somewhat surprisingly the reference marsh showed considerable between-year variation in similarity, which indicated substantial year-to-year variability in species composition. Based on accretion rate data from previous studies we predict that full recovery of the system would take between 75 and 150 years.

Notes: For an estuarine restoration project to be successful it must reverse anthropogenic effects and restore lost ecosystem functions. Restoration projects that aim to rehabilitate endangered species populations make project success even more important, because if misjudged damage to already weakened populations may result. Determining project success depends on our ability to assess the functional state or “performance” and the trajectory of ecosystem development. Mature system structure is often the desired “end point” of restoration and is assumed to provide maximum benefit for target species; however, few studies have measured linkages between structure and function and possible benefits available from early recovery stages. The Salmon River estuary, Oregon, U.S.A., offers a unique opportunity to simultaneously evaluate several estuarine restoration projects and the response of the marsh community while making comparisons with a concurring undiked portion of the estuary. Dikes installed in three locations in the estuary during the early 1960s were removed in 1978, 1987, and 1996, creating a “space-for-time substitution” chronosequence. Analysis of the marsh community responses enables us to use the development state of the three recovering marshes to determine a trajectory of estuarine recovery over 23 years and to make comparisons with a reference marsh. We assessed the rate and pattern of juvenile salmon habitat development in terms of fish density, available prey resources, and diet composition of wild juvenile Oncorhynchus tshawytscha (chinook salmon). Results from the outmigration of 1998 and 1999 show differences in fish densities, prey resources, and diet composition among the four sites. Peaks in chinook salmon densities were greatest in the reference site in 1998 and in the youngest (1996) site in 1999. The 1996 marsh had higher densities of chironomids (insects; average 864/m2) and lower densities of amphipods (crustaceans; average 8/m3) when compared with the other sites. Fauna differences were reflected in the diets of juvenile chinook with those occupying the 1978 and 1996 marshes based on insects (especially chironomids), whereas those from the 1987 and reference marshes were based on crustaceans (especially amphipods). Tracking the development of recovering emergent marsh ecosystems in the Salmon River estuary reveals significant fish and invertebrate response in the first 2 to 3 years after marsh restoration. This pulse of productivity in newly restored systems is part of the trajectory of development and indicates some level of early functionality and the efficacy of restoring estuarine marshes for juvenile salmon habitat. However, to truly know the benefits consumers experience in recovering systems requires further analysis that we will present in forthcoming publications.

Notes: Salt marshes continue to degrade in the United States due to indirect human impacts arising from tidal restrictions. Roads or berms with inadequate provision for tidal flow hinder ecosystem functions and interfere with self-maintenance of habitat, because interactions among vegetation, soil, and hydrology within tidally restricted marshes prevent them from responding to sea level rise. Prediction of the tidal range that is expected after restoration relative to the current geomorphology is crucial for successful restoration of salt marsh habitat. Both insufficient (due to restriction) and excessive (due to subsidence and sea level rise) tidal flooding can lead to loss of salt marshes. We developed and applied the Marsh Response to Hydrological Modifications model as a predictive tool to forecast the success of management scenarios for restoring full tides to previously restricted areas. We present an overview of a computer simulation tool that evaluates potential culvert installations with output of expected tidal ranges, water discharges, and flood potentials. For three New England tidal marshes we show species distributions of plants for tidally restricted and nonrestricted areas. Elevation ranges of species are used for short-term (〈5 years) predictions of changes to salt marsh habitat after tidal restoration. In addition, elevation changes of the marsh substrate measured at these sites are extrapolated to predict long-term (〉5 years) changes in marsh geomorphology under restored tidal regimes. The resultant tidal regime should be designed to provide habitat requirements for salt marsh plants. At sites with substantial elevation losses a balance must be struck that stimulates elevation increases by improving sediment fluxes into marshes while establishing flooding regimes appropriate to sustain the desired plants.

Notes: Assessing the response of salt marshes to tidal restoration relies on comparisons of ecosystem attributes between restored and reference marshes. Although this approach provides an objective basis for judging project success, inferences can be constrained if the high variability of natural marshes masks differences in sampled attributes between restored and reference sites. Furthermore, such assessments are usually focused on a small number of restoration projects in a local area, limiting the ability to address questions regarding the effectiveness of restoration within a broad region. We developed a hierarchical approach to evaluate the performance of tidal restorations at local and regional scales throughout the Gulf of Maine. The cornerstone of the approach is a standard protocol for monitoring restored and reference salt marshes throughout the region. The monitoring protocol was developed by consensus among nearly 50 restoration scientists and practitioners. The protocol is based on a suite of core structural measures that can be applied to any tidal restoration project. The protocol also includes additional functional measures for application to specific projects. Consistent use of the standard protocol to monitor local projects will enable pooling information for regional assessments. Ultimately, it will be possible to establish a range of reference conditions characterizing natural tidal wetlands in the region and to compare performance curves between populations of restored and reference marshes for assessing regional restoration effectiveness.

Notes: Since 1972 over 940 ha (2,300 ac) of leveed former salt marsh sites around San Francisco Bay have been restored to tidal action, purposely or through natural processes. The evolution of these sites can inform predictions of rates of marshplain evolution and establishment of tidal channel systems. A review of the history of 15 re-flooded sites ranging in size from 18 to 220 ha (45 to 550 ac) and in age from 2 to 29 years indicates that marshplain vegetation with more than 50% cover was established at nine of the sites within 4 to 20 years. The remaining six sites aged 2 to approximately 20 years continue to be less than 50% vegetated. The evolution of these sites is consistent with the following simple conceptual model of the physical evolution of restored tidal marshes in subsided breached sites. Initially, deposition of estuarine sediment builds up mudflats that allow vegetation establishment once elevations are high enough for vegetation to survive. Sites that are initially lower in the tidal frame take longer to vegetate than those that are initially higher. Three factors appear to retard the time frame for vegetation establishment: limited estuarine suspended sediment supply, erosion of deposited estuarine muds by internally generated wind waves, and restricted tidal exchange. These factors affect evolution more significantly in larger sites. The comparatively short time frame for vegetation colonization and marshplain evolution experienced in earlier, smaller, and/or less subsided breached levee restorations may not necessarily be replicable by simple levee breaching on larger subsided restoration sites now being planned. Our review of the 15 sites also indicates that the formation of tidal channels within the marshes is greatly dependent on whether and how high the site was filled before breaching. Filled sites at high intertidal elevations (above approximately 0.3 m below mean higher high water) can vegetate quickly but after several decades may show little development of tidal channels.

Notes: In November 1994 dikes were breached around Spencer Island, restoring tidal inundation and connections to the Snohomish River estuary, Washington. Approximately 23.7 ha (58.5 ac) of palustrine wetlands previously dominated by Phalaris arundinacea (reed canarygrass) now experience diurnal tides and are in the process of transition to a freshwater tidal system. It was expected that brackish water would accompany the return of tidal influence to the site, but post-project monitoring has revealed little evidence of salinity. Pre- and post-project monitoring of changes in habitat function included aerial photography, vegetation and fish sampling, and benthic prey studies. To date site changes include (1) die back of pre-project vegetation, development of tidal mudflat, and emergent wetland habitats, with recruitment of vegetation typical of freshwater tidal wetlands; (2) presence of juvenile coho, chum, and chinook salmon that feed on invertebrate prey typical of the site; (3) presence of three distinct benthic invertebrate assemblages in the project area; and (4) some invasion by Lythrum salicaria (purple loosestrife). The unexpected freshwater conditions, the lack of published information about tidal oligohaline marshes in the Pacific Northwest, the use of the site by endangered salmonid species, and the invasion by an undesired plant species underscore the importance of long-term monitoring at the site.

Notes: Empirical hydraulic geometry relationships for tidal marsh channels are a practical geomorphically based design tool that can assist in the planning of tidal wetland restoration projects. This study provides hydraulic geometry relationships for predicting the depth, width, and cross-sectional area of mature tidal channels as functions of contributing marsh area or tidal prism. The relationships are based on data from San Francisco Bay coastal salt marshes ranging in size from 2 to 5,700 ha. These hydraulic geometry relationships refine and expand on earlier relationships. Relationships for mature marshes can be used to predict the direction and rate of evolution of a channel in an immature or perturbed marsh system. Channel evolution data for three youthful tidal channels, ages 4 to 13 years, suggest that the channels are converging on their predicted equilibrium morphology. Two channels are eroding in response to significant increases in upstream tidal prism. They have enlarged first by deepening, in one case after 13 years to beyond the predicted equilibrium depth, and then widening through slumping of the channel banks. The third channel, a new one forming in a depositional mudflat, is converging on its equilibrium morphology after 13 years but will likely take several decades to equilibrate.

Notes: Intertidal restoration through realignment of flood defenses has become an important component of the U.K. coastal and estuarine management strategy. Although experimentation with recent deliberate breaches is in progress, the long-term prognosis for salt marsh restoration can be investigated at a number of sites around Essex, southeast England where salt marshes have been reactivated (unmanaged restoration) by storm events over past centuries. These historically reactivated marshes possess higher creek densities than their natural marsh counterparts. Both geomorphology and sedimentology determine the hydrology of natural and restored salt marshes. Elevation relative to the tidal frame is known to be the primary determinant of vegetation colonization and succession. Yet vegetation surveys and geotechnical analysis at a natural marsh, where areas with good drainage exist in close proximity to areas of locally hindered drainage at the same elevation, revealed a significant inverse relationship between water saturation in the root zone and the abundance of Atriplex portulacoides, normally the physiognomic dominant on upper salt marsh in the region. Elsewhere in Essex natural and restored marshes are typified by very high sediment water contents, and this is reflected in low abundance of A. portulacoides. After a century of reestablishment no significant difference could be discerned between the vegetation composition of the storm-reactivated marshes and their natural marsh counterparts. We conclude that vegetation composition may be restored within a century of dike breaching, but this vegetation does not provide a reliable indicator of ecological functions related to creek structure.

Notes: Floristic composition and soil characteristics (moisture, pH, nutrient contents) in abandoned upland rice paddies of different ages were analyzed to clarify the regenerative aspects of succession as a tool for habitat restoration. The study sites represented five seral stages: newly abandoned paddy fields; successional paddy fields abandoned for 3, 7, and 10 years; and a 50-year-old Alnus japonica forest. A vegetation sere was apparent in changes of dominant plant species in the order Alopecurus aequalis var. amurensis (annual grass), Aneilema keisak (annual forb), Juncus effusus var. decipiens (rush), Salix koriyanagi (willow), and Alnus japonica (alder) communities. These temporal stages resemble the spatial zonation of vegetation in local riparian floodplain ecosystems, indicating a hydrosere, with soil moisture decreasing over time. Age distributions and life forms of the dominant plant species support a “tolerance” model of secondary succession, in which the established species persist into later successional stages. Persistence of earlier colonizers led to a net cumulative increase in species richness and a more even distribution of species cover with increasing field age. Between 10 and 50 years, vegetation stabilizes as an alder community. Soil moisture content decreased steadily with paddy field age after an initial rise immediately after their abandonment, whereas pools of organic matter, N, P, K, Ca, and Mg, increased with field age. The pace and direction of recovery of native vegetation and natural soil properties in these abandoned rice paddies resembled classic old field succession, a form of secondary succession that often serves as a template for guiding restoration efforts. Active intervention, in particular dismantling artificial levees, could accelerate the recovery process, but natural habitat recovery generally appears sufficiently robust to achieve “passive” restoration of this rare community without intervention.

Notes: A comparative analysis of soils and vegetation from cultivated areas reseeded to native grasses and native prairies that have not been cultivated was conducted to evaluate restoration of southern mixed prairie of the Great Plains over the past 30 to 50 years. Restored sites were within large tracts of native prairie and part of long-term grazing intensity treatments (heavy, moderate, and ungrazed), allowing evaluation of the effects of grazing intensity on prairie restoration. Our objective was to evaluate restored and native sites subjected to heavy and moderate grazing regimes to determine if soil nutrients from reseeded cultivated land recovered after 30 years of management similar to the surrounding prairie and to identify the interactive influence of different levels of grazing and history of cultivation on plant functional group composition and soils in mixed prairies. For this mixed prairie, soil nitrogen and soil carbon on previously cultivated sites was 30 to 40% lower than in uncultivated native prairies, indicating that soils from restored sites have not recovered over the past 30 to 50 years. In addition, it appears that grazing alters the extent of recovery of these grassland soils as indicated by the significant interaction between grazing intensity and cultivation history for soil nitrogen and soil carbon. Management of livestock grazing is likely a critical factor in determining the potential restoration of mixed prairies. Heavy grazing on restored prairies reduces the rate of soil nutrient and organic matter accumulation. These effects are largely due to changes in composition (reduced tallgrasses), reduced litter accumulation, and high cover of bare ground in heavily grazed restored prairies. However, it is evident from this study that regardless of grazing intensity, restoration of native prairie soils requires many decades and possibly external inputs to adequately restore organic matter, soil carbon, and soil nitrogen.

Notes: Regeneration and expansion of Aristida beyrichiana and Aristida stricta (wiregrass) populations in remaining fire-maintained Pinus palustris (longleaf pine) stands of the southeastern United States has become an objective of land managers. Although growing-season fire is required for successful wiregrass seed production, studies examining naturally occurring wiregrass seedling dynamics are few. This study investigates how seedling survivorship is affected by season of burn, seedling size, time since germination, and proximity to adult plants. Restoration at this research site was begun in 1992 with the planting of containerized longleaf pine and wiregrass seedlings. Study plots were established in November 1997 after a growing-season prescribed fire (June 1996) that resulted in successful seed production and seedling recruitment. Burn treatment plots included (1) no burn (control), (2) fire in the dormant season of the first year after germination (March 1998), (3) fire in the growing season of the first year after germination (August 1998), and (4) fire in the growing season of the second year after germination (July 1999). Seedling mortality increased with growing season burning and close proximity to planted adults. Natural seedling recruitment continued into the second year after initial seed-drop in all plots, which verifies that wiregrass seed banking occurs for a minimum of 2 years after seed drop. Where wiregrass management objectives include population expansion, seedling recruits should be allowed 1 to 2 years post-germination without growing season fire for successful establishment.

Notes: The use of plantations to manage extensive tracks of deforested lands in the tropics is a conservation strategy that has recently received considerable attention. Plantation trees can promote seed dispersal by attracting dispersers and creating favorable site conditions, leading to increased germination and establishment of indigenous trees. Subsequently, plantation trees can be harvested for profit or left to senesce, leaving a native tree community. We evaluated the effect of vine, grass, and shrub cutting (weeding) over a 3-year period on regeneration of indigenous trees subsequent to the removal of plantation softwoods in Kibale National Park, Uganda. Counter to what would be expected if weeding released trees from competition, we found no difference in the total number of stems or in the stems greater than 10 cm diameter at breast height between control and weeded plots; there were more stems greater than 1 cm diameter at breast height in the control plots. For species found in both control and weeded plots, the maximum size of individuals did not differ. At the end of the study, 61 species were found in the control plots and 43 species were found in the weeded plots, and in both types of plots the three most abundant species were the same. The number of species and stems classified as early or middle successional species did not differ between weeded and control plots. The fact that weeding did not promote regeneration of indigenous trees after the removal of plantation trees illustrates the importance of evaluating and field-testing potential management options.

Notes: Controlled-release fertilization with two formulations, Forestcote 22-4-6 + Minors and Gromax 21-6-2 + Minors, and dolomitic lime were evaluated for their capacity to facilitate establishment and enhance nutrition of bareroot Jeffrey pine (Pinus jeffreyi Grev. & Balf.) on an acidic Sierra Nevada surface mine. All amendments were applied at outplanting to the backfill of augered planting holes, with a low rate of 8 g and a high rate of 16 g per seedling for the two fertilizer formulations, whereas a single rate of 30 g was used for lime. Liming induced excessive seedling mortality throughout the study, whereas both fertilizer formulations also reduced survival but only as an interactive effect with the lime amendment. Growth stimulation by the fertilizer applications was readily apparent after three growing seasons, with the response to the high rate surpassing that to the low rate and the response to the Forestcote formulation exceeding that to Gromax. Conversely, the lime amendment depressed seedling growth, and it is likely that a propensity to exacerbate the stress imposed by dry growing season soils through interference with water uptake accounts for the overall poor performance of the seedlings that received this amendment. Improved N and P nutrition, with the former likely the most critical, was largely responsible for the growth stimulation resulting from fertilization. However, this treatment also suppressed the absorption of certain micronutrients as well as that of Al, and the amelioration of potential phytotoxicities may have also contributed to the favorable performance of fertilized seedlings. Further evidence for this conclusion was supplied by base cation/metallic element molar ratios involving Al and Mn, which were frequently increased by fertilization. In contrast, the influence of the lime amendment on seedling nutrition was marginal, with positive responses too infrequent to improve seedling performance.

Notes: We examined the effects of presettlement forest restoration treatments on the nesting success of Western Bluebirds in ponderosa pine forests of northwestern Arizona, U.S.A. From 1998 to 2001 we monitored 97 active Western Bluebird nests, 41 in current-condition untreated forest and 56 in restoration-treated forest. We found no effect of restoration treatments on clutch size and little effect on the number of nestlings per nest. However, in treated forest stands number of fledglings per nest averaged 1.6 times greater, and probability of a nest surviving to successfully fledge at least one young was up to 4.2 times greater than in untreated forest. Probability of a nest succeeding averaged 0.39 ± 0.11 (SE) and 0.75 ± 0.06 from 1999 to 2001 in untreated and treated forests, respectively. In addition, in treated forest, average number of nests infested with the blowfly parasite Protocalliphora sialia was up to 4.3 times greater, and number of parasites per fledgling was up to 10.7 times greater than in untreated forest. Overall, the data suggest that in treated forest Western Bluebirds have a higher probability of successfully fledging young, but they are at greater risk of parasitic infestations, of which the ultimate effects on post-fledging survival are unknown.

Notes: Instream limestone sand application is used at many sites in Pennsylvania to neutralize acidic stream water resulting from acid deposition. However, questions remain about the effectiveness of limestone sand in the treatment of acid waters, such as reduced contact time at high flow, remobilization of aluminum, and adverse effects on macroinvertebrates. A 1-year evaluation of limestone sand application to Bear Run, an acidic stream in southwestern Pennsylvania, was begun in 1999. Another nearby acid stream, Linn Run, served as a control. Water quality during baseflow and episodic acidification events, along with fish and macroinvertebrates, were monitored to evaluate impacts of the sand application. Hydrogen ion (H+) concentration and total dissolved aluminum (TDA) were significantly reduced, and acid neutralizing capacity was significantly increased downstream of the limestone sand application compared with the upstream site on Bear Run. These parameters at the downstream sites were also different (∝〈inlineGraphic alt="leqslant R: less-than-or-eq, slant" extraInfo="nonStandardEntity" href="urn:x-wiley:10612971:REC1024:les" location="les.gif"/〉 0.10) from the comparable sites on the control stream. TDA and hydrogen ion concentrations were significantly decreased (∝〈inlineGraphic alt="leqslant R: less-than-or-eq, slant" extraInfo="nonStandardEntity" href="urn:x-wiley:10612971:REC1024:les" location="les.gif"/〉 0.10) compared with concentrations before the sand application to Bear Run but not on the control stream. No fish were present upstream of the sand application site, and only a few fish were found downstream at the mouth of Bear Run. Standing crop, number of taxa, and Shannon-Weaver diversity index values indicated that macroinvertebrate populations were negatively impacted 300 m downstream from the sand application and improved at the site 1,600 m downstream. Although water quality was improved on Bear Run, benefits to macroinvertebrates depended on downstream location, and fish populations did not show improvement.

Notes: We report on spontaneous and directed succession on a dry sandy landfill site of low fertility at Berlin-Malchow, Germany. Changes in species composition and cover were followed on unmown and mown permanent plots of 2 × 2 m size through 5 years of vegetation development. Species richness on unmown plots was relatively constant during the time of observation, with 20 to 25 species per 4 m2. Total cover of unmown plots continuously increased from approximately 10% in the first year to 80% in the fifth year. There are no clearly discernible sequential successional stages until present. The species composition includes species of all life forms, which colonized the site immediately after the initiation of the succession process representing the initial floristic composition type of vegetation development. However, perennial grasses and herbs gradually increased in cover up to approximately 40%. Woody plants were also present from the first year of succession and increased up to more than 20% cover in the fifth year, forming a shrub layer (〉0.5 m) after the second year. Mowing significantly increased species richness, which was evident from the third year onward. This effect was mainly due to the reduction of the tall perennial grass Calamagrostis epigejos. Solidago canadensis and woody species were also significantly affected (lower cover and height), whereas short perennial herbs like Plantago lanceolata and Trifolium repens benefited from mowing.

Notes: Froelichia floridana (cottonweed) occurs as a disjunct population along the Ohio River in southeastern Ohio. The anomalous occurrence of F. floridana in this area has led to its designation as a state endangered species and a management regime to maintain the habitat conditions in which it occurs. As part of this effort, a restoration site was established on public lands in 1984 from seed collected in areas threatened by development. This study seeks to determine the demographic characteristics of this species in the restored and non-restored managed sites to provide basic ecological information regarding life history parameters and to judge the effectiveness of the restoration. For two years (1997–1998) we collected information on seed bank abundance, field seed germination, plant survivorship, and seed production to create a stage-based transition matrix model. The model suggests that population growth and abundance as assayed by λ (rate of increase) are stable to declining and are similar between the restoration and natural sites. A reduction in competition had a positive effect on population growth. Elasticity analysis showed that plants germinating earlier in the spring and becoming established as an early cohort contributed a greater level of reproductive output than plants germinating in late spring. Lowered population growth for 1997 is attributed to a cooler and dryer than average early spring that delayed germination and subsequent seed production. Elasticity analysis also suggested that the presence of a persistent seed bank was crucial for long-term population maintenance and may allow for recovery in areas of low aboveground abundance through soil manipulation.

Notes: North American prairie remnants and restorations are normally managed with dormant-season prescribed fires. Growing-season fire is of interest because it suppresses dominant late-flowering grasses and forbs, thereby making available light and other resources used by subdominant grasses and forbs that comprise most prairie diversity. Here we report a twofold increase in mean frequency and richness of subdominant species after late-summer fire. Stimulation of subdominants was indiscriminate; richness of prairie and volunteer species increased in species that flowered in early, mid-, or late season. Early spring fire, the management tool used on this site until this experiment, had no effect on subdominant richness or frequency. Neither burn treatment affected reproductive tillering of the tallgrasses Sorghastrum nutans or Panicum virgatum. Flowering of Andropogon gerardii increased 4-fold after early-spring fires and 11-fold after late-summer fires. These preliminary results suggest that frequency and species richness of subdominants can be improved by late growing-season fire without compromising vigor of warm-season tallgrasses.

Notes: Oligohaline tidal channels (sloughs) in the Pacific Northwest were shown to have allometric form with respect to outlet width and depth, channel length, perimeter, and surface area. In contrast, an artificial slough, excavated to mitigate port improvements, did not conform to natural slough allometry, resulting in high retention of allochthonous inputs and sediment accumulation. Additionally, intertidal sedge habitat abundance was related to slough size for smaller sloughs, but larger sloughs did not fit this allometric pattern. This suggests that sedge habitat in large sloughs has been destroyed due to extensive log storage and transportation from the 1890s to the 1970s. Finally, the abundance of salmonid prey of terrestrial origin—aphids and adult flies—in slough surface waters was correlated with slough perimeter and, for aphids, with the amount of intertidal sedge habitat. An allometric perspective on landscape form and function has several implications for habitat restoration and mitigation: (1) Size-related constraints on replication for landscape-scale studies are loosened (e.g., rather than requiring reference sites that are similar in size to experimental sites, analysis of covariance can be used to control size effects); (2) physical processes, such as sedimentation and erosion, affect landscape form, whereas landscape form can affect ecological processes, so design of restoration or mitigation projects should conform to allometric patterns to maximize physical and ecological predictability; (3) landscape allometry may provide insight into undocumented human disturbances; and (4) allometric patterns suggest design goals and criteria for success.

Notes: Dennstaedtia punctilobula (hay-scented fern) can act as a native invasive species in forests in eastern North America where prolonged deer browsing occurs in stands with partially open overstory canopies. Ferns dominate the understory with a 60-cm tall canopy, with little regeneration of native tree species. It has been hypothesized that, once established, ferns may continue to inhibit tree regeneration after deer browsing has been reduced. To test this hypothesis, we documented the pattern of recovery of the tree seedling understory in plantations of Pinus strobus (white pine) and Pinus resinosa (red pine) on the Quabbin Reservation watershed protection forest in central Massachusetts, where after 40 years of intensive deer browsing the deer herd was rapidly reduced through controlled hunting. Dense fern understories occur on nearly 4,000 ha of the predominantly oak–pine forest. Three years after deer herd reduction, stands with the highest density fern cover (77% of plots with〉90% cover) had significantly fewer seedlings at least 30 cm in height, compared with stands with lower fern density, and those seedlings consisted almost entirely of Betula lenta (black birch) and white pine. Height growth analysis showed that black birch and white pine grew above the height of the fern canopy in 3 and 6 years, respectively. In contrast, two common species, Fraxinus americana (white ash) and Quercus rubra (red oak), grew beneath the dense fern cover for 5 years with height growth less than 5 cm/yr after the first year. A study of spring phenology indicated that the ability of black birch to grow through the fern canopy might have been due to its early leaf development in spring before the fern canopy was formed, in contrast to oak and ash with delayed leaf development. Thus, the ferns showed differential interference among species with seedling development after reduction of deer browse.

Notes: The reestablishment of riparian forest is often viewed as “best management practice” for restoring stream ecosystems to a quasi-natural state and preventing non-point source contaminants from entering them. We experimentally assessed seedling survivorship and growth of Quercus palustris (pin oak), Q. rubra (red oak), Q. alba (white oak), Betula nigra (river birch), and Acer rubrum (red maple) in response to root-stock type (bare root vs. containerized), herbivore protection (tree shelters), and weed control (herbicide, mowing, tree mats) over a 4-year period at two riparian sites near the Chester River in Maryland, U.S.A. We started with tree-stocking densities of 988/ha (400/ac) in the experimental plots and considered 50% survivorship (i.e., a density of 494/ha [200/ac] at crown closure) to be an “acceptable or minimum” target for riparian restoration. Results after four growing seasons show no significant difference in survivorship and growth between bare-root and containerized seedlings when averaged across all species and treatments. Overall survivorship and growth was significantly higher for sheltered versus unsheltered seedlings (49% and 77.6 cm vs. 12.1% and 3.6 cm, respectively) when averaged across all species and weed control treatments. Each of the five test species exhibited significantly higher 4-year growth with shelter protection when averaged across all other treatments, and all species but river birch had significantly higher survivorship in shelters during the period. Seedlings protected from weeds by herbicide exhibited significantly higher survivorship and growth than seedlings in all other weed-control treatments when averaged across all species and shelter treatments. The highest 4-year levels of survivorship/growth, when averaged across all species, was associated with seedlings protected by shelters and herbicide (88.8%/125.7cm) and by shelters and weed mats (57.5%/73.5 cm). Thus, only plots where seedlings were assisted by a combination of tree shelters and either herbicide or tree mats exhibited an “acceptable or minimum” rate of survivorship (i.e.,〉50%) for riparian forest restoration in the region. Moreover, the combined growth and survivorship data suggest that crown closure over most small streams in need of restoration in the region can be achieved most rapidly (i.e., 15 years or less) by protecting seedlings with tree shelters and controlling competing vegetation with herbicides.

Notes: The mining industry commonly seeds shrubs and grasses concurrently on coal-mined lands of northeastern Wyoming, but ecological interactions between seeded shrubs and grasses are not well documented. Artemisia tridentata Nutt. ssp. wyomingensis (Beetle and Young) (Wyoming big sagebrush) is the dominant pre-mining shrub on many Wyoming mine sites. Despite past failures to establish Wyoming big sagebrush, the Wyoming Department of Environmental Quality, Land Quality Division's rules and regulations require establishment of 1 shrub per m2 on 20% of post-mined land in Wyoming. A study was established at the Belle Ayr Coal Mine south of Gillette, Wyoming to evaluate the effects of sagebrush seeding rates and grass competition on Wyoming big sagebrush seedling density. Three sagebrush seeding rates (1, 2, and 4 kg pure live seed [pls]/ha; 350, 700, and 1,400 pls/m2, respectively) and seven cool-season perennial grass mixture seeding rates (0, 2, 4, 6, 8, 10, and 14 kg pls/ha; 0, 187, 374, 561, 750, 935, and 1,309 pls/m2, respectively) were applied during winter 1998–1999. Pascopyrum smithii (Rydb.) A. Love (western wheatgrass), Elymus lanceolatus (Scribner & J.G. Smith) Gould (thickspike wheatgrass), and Elymus trachycaulus (Link) Gould ex Shinners (slender wheatgrass) comprised the grass seed mix (equal seed numbers of each species). Sagebrush seedling density differed among sagebrush seeding rates but not among grass seeding rates. On all sampling dates in 1999 and 2000, sagebrush seedling density differed among sagebrush rates and was greatest at the 4 kg pls/ha sagebrush seeding rate. All sagebrush seeding rates provided densities of at least 1 shrub per m2 after two growing seasons. Grass density and production in 2000 suggest that adequate grass production (〈inlineGraphic alt="geqslant R: gt-or-equal, slanted" extraInfo="nonStandardEntity" href="urn:x-wiley:10612971:REC1025:ges" location="ges.gif"/〉75 g/m2) was achieved by seeding at 6 to 8 kg pls/ha. Within these grass seeding rates, four or more sagebrush seedlings per m2 were attained when sagebrush was seeded at 2 to 4 kg pls/ha. Use of these seeding rate combinations in mine reclamation can achieve Wyoming big sagebrush standards and reduce reseeding costs.

Notes: The effects of intensive recreation impacts and restoration amendments on soil parameters were assessed at four campsites in the Eagle Cap Wilderness, northeastern Oregon. Sites (2,215- to 2,300-m elevation) are characterized by shallow granitic soils, an Abies lasiocarpa/Pinus albicaulis overstory, and a Vaccinium scoparium understory. In fall 1995, plots were established at four campsites on three subalpine lakes in which soils were scarified, compost amended, and planted to native species. In summer 1998, we sampled surface soils (0–15 cm) on undisturbed sites (between and under vegetation) and unamended and compost-amended campsite soils. Samples were analyzed for total organic C, total N, potentially mineralizable N (PMN), NH4, soil moisture, microbial biomass, basal 5-day respiration rates, and microbial community carbon utilization profiles. Unamended campsite soils had significantly lower levels of PMN, microbial biomass, basal respiration, and number of substrates metabolized in carbon utilization profiles. Compost addition elevated all these impacted parameters on campsite soils, although the increase in basal respiration rate was neither statistically significant nor sufficient to approach rates found underneath vegetation on undisturbed soils. Only the number of substrates metabolized in the carbon utilization profiles was significantly higher on compost-amended soils than on undisturbed soils. Levels of PMN indicate that campsite soils may lack sufficient N for rapid plant regeneration, whereas amended and undisturbed soils contained adequate quantities of available N. This work suggests that compost amendments can ameliorate impacts to soil chemistry and microbial populations caused by camping, without exceeding the N fertility found on undisturbed soils.

Notes: Black willow (Salix nigra) uses periodic flood events for dispersal of vegetative propagules, subjecting them to periods of soaking before their deposition along the streambank. It was hypothesized that this life history trait results in optimal conditions for willow growth and survival. To test this hypothesis, a greenhouse experiment was conducted using 1.2-m-long black willow cuttings (posts) with a basal diameter of 5 cm. Cuttings were subjected to three soaking treatments (0, 3, and 10 days) and then grown under four soil moisture regimes (control, drought, permanently flooded, and intermittently flooded). Growth, biomass, and survival were recorded. Results showed that soaking posts for 10 days was most beneficial in the control soil moisture regime, enhancing root, shoot, leaf, and total biomass production. Shoot abundance and growth were also enhanced by 10 days of soaking in the control and permanently flooded moisture regimes. Finally, survival increased significantly in control and drought moisture regimes in response to the 10-day soaking treatment. Results clearly demonstrated that soaking had significant effects on willow post success when evaluated across all soil moisture regimes. Posts subjected to the 10-day soaking treatment consistently had greatest growth and biomass and displayed a doubling of the survival rate. Therefore, soaking willow cuttings before planting is a simple, inexpensive technique that may be used to bolster streambank restoration success.

Notes: Prairies in the Pacific Northwest have been actively restored for over a decade. Competition from non-native woody and herbaceous species has been presumed to be a major cause for the failure of restoration projects. In this research, plugs of the native prairie bunchgrass, Festuca idahoensis Elmer var. roemeri (Pavlick), were grown from seed in a nursery and transplanted into a grassland site dominated by non-native pasture grasses. The growth of the plants was followed for three years, and biomass of all volunteer plants was measured. Before planting, five treatments were applied to the plots: removal of vegetation by burning, removal of vegetation by an herbicide-and-till procedure, soil impoverishment by removal of organic matter, fertilizer application, and compost mulch application. Initial growth of Idaho fescue plugs was greatest with fertilizer and compost mulch. Plants grown in mulched plots were also able to photosynthesize later into the dry summer season. After the first year, plots initially fertilized or composted had the lowest survival rate of Idaho fescue. Impoverished and herbicide-and-till plots had the greatest 3-year survival. Mulched plots supported the greatest weed growth after three years. Stressful environments give a competitive advantage to Idaho fescue in prairie restoration projects. As weedy species increase, growth and survival of Idaho fescue decreases.

Notes: Natural ecosystems globally are often subject to multiple human disturbances that are difficult to restore. A restoration experiment was done in an urban fragment of native coastal sage scrub vegetation in Riverside, California that has been subject to frequent fire, high anthropogenic nitrogen deposition, and invasion by Mediterranean annual weeds. Hand cultivation and grass-specific herbicide were both successful in controlling exotic annual grasses and promoting establishment of seeded coastal sage scrub vegetation. There was no native seedbank left at this site after some 30 years of conversion to annual grassland, and the only native plants that germinated were the seeded shrubs, with the exception of one native summer annual. The city green-waste mulch used in this study (C:N of 39:1) caused short-term N immobilization but did not result in decreased grass density or increased native shrub establishment. Seeding native shrubs was successful in a wet year in this Mediterranean-type climate but was unsuccessful in a dry year. An accidental spring fire did not burn first-year shrubs, although adjacent plots dominated by annual grass did burn. The shrubs continued to exclude exotic grasses into the second growing season, suggesting that successful shrub establishment may reduce the frequency of the fire return interval.

Notes: Connectivity has been an accepted goal in ecological restoration of wilderness areas for some time, but it is a relatively new approach in urban areas. The connectivity analysis presented here explores the numbers and patterns of corridors required to connect urban green spaces as part of an overall biodiversity conservation strategy. Green spaces in this study were weighted based on size and a habitat requirement of 0.5 ha for a hypothetical indicator species. Thirteen potential networks were evaluated using Gamma, Beta, and Cost Ratio indices. The study zone contained 54 green spaces (habitat nodes) with a combined area of 636.5 ha in a total urban area of approximately 2,600 ha. Several models (Travelling Salesman, Paul Revere, and Least Cost to User) were used to evaluate possible connections. These results indicated that at least 325 linkages are necessary to connect half of the nodes. Such large numbers of linkages are only feasible by enhancing the matrix of backyard habitat, planted boulevards, and utility rights-of way found in a city. Strengthening such networks should work well to support the biota protected in urban parks and wildlife refuges and the seasonal migrants that sometimes depend on urban habitats for their survival.

Notes: Numerical 3D simulations of the development of spiral inclusion trails in porphyroblasts were conducted in order to test the proposals that (a) 3D spiral geometry differs between the rotation and nonrotation end-member models of spiral formation proposed in the literature, and (b) 3D spiral geometry can be used as a criterion to distinguish between the two end-member models in rocks. Four principal differences are identified between the two sets of simulations: smoothness of spiral curvature; spacing of foliation planes; alignment of individual foliation planes either side of the sphere representing the porphyroblast; and spiral asymmetry with respect to matrix shear sense. Of these differences, only spiral asymmetry and possibly the alignment of individual foliation planes are diagnostic criteria for distinguishing between the end-member models. In the absence of a readily applied test to distinguish the end-member models, interpretation of spiral inclusion trails is problematic. It is necessary to determine complementary evidence to distinguish porphyroblast rotation or nonrotation during spiral formation.

Notes: Metasedimentary rocks generally contain carbonaceous material (CM) deriving from the evolution of organic matter originally present in the host sedimentary rock. During metamorphic processes, this organic matter is progressively transformed into graphite s.s. and the degree of organisation of CM is known as a reliable indicator of metamorphic grade. In this study, the degree of organisation of CM was systematically characterised by Raman microspectroscopy across several Mesozoic and Cenozoic reference metamorphic belts. This degree of organisation, including within-sample heterogeneity, was quantified by the relative area of the defect band (R2 ratio). The results from the Schistes Lustrés (Western Alps) and Sanbagawa (Japan) cross-sections show that (1) even through simple visual inspection, changes in the CM Raman spectrum appear sensitive to variations of metamorphic grade, (2) there is an excellent agreement between the R2 values calculated for the two sections when considering samples with an equivalent metamorphic grade, and (3) the evolution of the R2 ratio with metamorphic grade is controlled by temperature (T). Along the Tinos cross-section (Greece), which is characterised by a strong gradient of greenschist facies overprint on eclogite facies rocks, the R2 ratio is nearly constant. Consequently, the degree of organisation of CM is not affected by the retrogression and records peak metamorphic conditions. More generally, analysis of 54 samples representative of high-temperature, low-pressure to high-pressure, low-temperature metamorphic gradients shows that there is a linear correlation between the R2 ratio and the peak temperature [T(°C) = −445 R2 + 641], whatever the metamorphic gradient and, probably, the organic precursor. The Raman spectrum of CM can therefore be used as a geothermometer of the maximum temperature conditions reached during regional metamorphism. Temperature can be estimated to ± 50 °C in the range 330–650 °C. A few technical indications are given for optimal application.

Notes: Eclogite facies metatroctolites from a variety of Western Alps localities (Voltri, Monviso, Lanzo, Allalin, Zermat–Saas, etc.) that preserve textural evidence of their original form as bimineralic olivine-plagioclase rocks are considered in terms of calculated mineral equilibria in the system Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O (NCFMASH). Pseudosections, based on a new petrogenetic grid for NCFMASH presented here, are used to unravel the metamorphic history of the metatroctolites, considering the rocks to consist of different composition microdomains corresponding to the original olivine and plagioclase grains. On the basis that the preservation of the mineral assemblage in each microdomain will tend to be from where on a rock's P–T path the metamorphic fluid phase is used up via rehydration reactions, P–T pseudosections contoured for water content, and P–T path-MH2O (amount of water) pseudosections, are used to examine fluid behaviour in each microdomain. We show that the different microdomains are likely to preserve their mineral assemblages from different places on the P–T path. For the olivine microdomain, the diagnostic mineral assemblage is chloritoid + talc (+ garnet + omphacite). The preservation of this assemblage, in the light of the closed system P–T path-MH2O relationships, implies that the microdomain loses its metamorphic fluid as it starts to decompress, and, in the absence of subsequent hydration, the high pressure mineral assemblage is then preserved. In the plagioclase microdomain, the diagnostic assemblage is epidote (or zoisite) + kyanite + quartz suggesting a lower pressure (of about 2 GPa) than for the olivine microdomain. In the light of P–T path-MH2O relationships, development of this assemblage implies breakdown of lawsonite across the lawsonite breakdown reaction, regardless of the maximum pressure reached. It is likely that the plagioclase microdomain was mainly fluid-absent prior to lawsonite breakdown, only becoming fluid-present across the reaction, then immediately becoming fluid-absent again.

Notes: Dense, CO2-rich fluid inclusions hosted by plagioclases, An45 to An54, of the O.-v.-Gruber- Anorthosite body, central Dronning Maud Land, East Antarctica, contain varying amounts of small calcite, paragonite and pyrophyllite crystals detected by Raman microspectroscopy. These crystals are reaction products that have formed during cooling of the host and the original CO2-rich H2O-bearing enclosed fluid. Variable amounts of these reaction products illustrates that the reaction did not take place uniformly in all fluid inclusions, possibly due to differences in kinetics as caused by differences in shape and size, or due to compositional variation in the originally trapped fluid. The reaction albite + 2anorthite + 2H2O + 2CO2 = pyrophyllite + paragonite + 2calcite was thermodynamically modelled with consideration of different original fluid compositions. Although free H2O is not detectable in most fluid inclusions, the occurrence of OH-bearing sheet silicates indicates that the original fluid was not pure CO2, but contained significant amounts of H2O. Compared to an actual fluid inclusion it is obvious, that volume estimations of solid phases can be used as a starting point to reverse the retrograde reaction and recalculate the compositional and volumetrical properties of the original fluid. Isochores for an unmodified inclusion can thus be reconstructed, leading to a more realistic estimation of P–T conditions during earlier metamorphic stages or fluid capturing.

Notes: High-pressure basic granulites are widely distributed as enclaves and sheet-like blocks in the Huaian TTG gneiss terrane in the Sanggan area of the Central Zone of the North China craton. Four stages of the metamorphic history have been recognised in mineral assemblages based on inclusion, exsolution and reaction textures integrated with garnet zonation patterns as revealed by compositional maps and compositional profiles. The P–T conditions for each metamorphic stage were obtained using thermodynamically and experimentally calibrated geothermobarometers. The low-Ca core of growth-zoned garnet, along with inclusion minerals, defines a prograde assemblage (M1) of garnet + clinopyroxene + plagioclase + quartz, yielding 700 °C and 10 kbar. The peak of metamorphism at about 750–870 °C and 11–14.5 kbar (M2) is defined by high-Ca domains in garnet interiors and inclusion minerals of clinopyroxene, plagioclase and quartz. Kelyphites or coronas of orthopyroxene + plagioclase ± magnetite around garnet porphyroblasts indicate garnet breakdown reactions (M3) at conditions around 770–830 °C and 8.5–10.5 kbar. Garnet exsolution lamellae in clinopyroxene and kelyphites of amphibole + plagioclase around garnet formed during the cooling process at about 500–650 °C and 5.5–8 kbar (M4). These results help define a sequential P–T path containing prograde, near-isothermal decompression (ITD) and near-isobaric cooling (IBC) stages.The clockwise hybrid ITD and IBC P–T paths of the HP granulites in the Sanggan area imply a model of thickening followed by extension in a collisional environment. Furthermore, the relatively high-pressures (6–14.5 kbar) of the four metamorphic stages and the geometry of the P–T paths suggest that the HP granulites, together with their host Huaian TTG gneisses, represent the lower plate in a crust thickened during collision. The corresponding upper-plate might be the tectonically overlying Khondalite series, which was subjected to medium- to low-pressure (MP/LP: 7–4 kbar) granulite facies metamorphism with a clockwise P–T path including an ITD segment. Both the HP and the MP/LP granulite facies events occurred contemporaneously at c. 1.90–1.85 Ga in a collisional environment created by the assembly process of the North China craton.

Notes: An eclogite sample from the Grossgockner region of the Hohe Tauern, Austria contains garnet with a pronounced compositional discontinuity between a Mn-rich core and an Fe-rich rim. This jump in composition was caused by a garnet-consuming reaction followed by growth of the garnet rim + omphacite and marks the prograde transition from epidote–amphibolite to eclogite facies metamorphism. Garnet growth ended at peak metamorphic conditions of 570 °C, 17 kbar, but intracrystalline diffusion continued until about 450 °C, 4 kbar on the retrograde path. This garnet overgrowth texture represents a natural diffusion couple and a time span of 1 Myr was calculated from the diffusion profile developing out of the original sharp compositional step. For typical crustal densities, this time corresponds to a minimum average velocity in the range 4.6–7.4 cm yr−1 (for vertical movement), which is one of the fastest exhumation rates reported. The diffusion of all divalent cations of four profiles was modelled, both analytically and numerically. Both approaches gave comparable results, but the times computed for each element were always discrepant up to a factor of 2. Variations of diffusion coefficients within 2 in analytical calculations remedied this and gave consistent upper time limits. Numerical modelling does not require the simplifications introduced in the analytical approach. On the other hand, error propagation was computationally unfeasible with this method.

Notes: Low-T, intermediate to high-P assemblages indicative of the prehnite–pumpellyite, greenschist and blueschist facies are preserved in mélange zones and slivers of oceanic crust within two major fault zones of the turbidite-dominated Lachlan Orogen. In one of these fault zones (Governor Fault Zone), blueschists occur as Franciscan-like blocks in a serpentinite/talc matrix that is interleaved with phyllites and slates, and structurally overlain by a fault slice or duplex of predominantly pillow basalt, chert, and turbidite. The blueschist metavolcanics are interpreted to have formed at 〈 450 °C and at a depth of approximately 21–27 km. The presence of blue amphibole in the blocks, rinds and matrix indicate that the metavolcanics were emplaced in the matrix prior to blueschist metamorphism. Blocks and matrix were partially exhumed, interleaved with tectonic slices of phyllite and slate, and subsequently folded at about 10–12 km depth, inferred from bo values of the dominant mica fabric in the phyllites and slates. Metamorphic P–T is highest in the structurally lowest slice (mélange zone) and lowest in the overlying ophiolitic fault slice, suggestive of an accretionary burial metamorphic pattern formed by underplating of the mélange. In the other fault zone (Heathcote Fault Zone), blueschists transitional to greenschist facies are interpreted to have formed at 〈 450 °C and at a depth of approximately 15–21 km. They occur as blocks in serpentinite/talc-matrix mélange and are also associated with fault slices of oceanic crust. Textural and mineralogical evidence suggests that the protoliths for the blueschists in both fault zones were boninitic pillow lavas. The metamorphic facies and patterns, and the structural and lithological associations, can be interpreted in terms of disruption of oceanic crust and overlying sediments during subduction, and formation of serpentinite-matrix mélange overprinted by blueschist metamorphism either prior to or during underplating of the mélange and duplex formation. The presence of blueschist metavolcanics indicate that these processes occurred at considerable depth. These interpretations have implications for the evolution of large-scale fault zones in noncollisional, convergent oceanic settings.

Notes: Regional variation in the P–T path of the Sambagawa metamorphic rocks, central Shikoku, Japan has been inferred from compositional zoning of metamorphic amphibole. Rocks constituting the northern part (Saruta River area) exhibit a hairpin type P–T path, where winchite/actinolite grew at the prograde stage, the peak metamorphism was recorded by the growth of barroisite to hornblende and sodic amphibole to winchite/actinolite grew at the retrograde stage. In the southern part (Asemi River area), rocks exhibit a clockwise type P–T path, where barroisite to hornblende core is rimmed by winchite to actinolite. The difference in P–T path could suggest a faster exhumation rate (i.e. more rapid decompression) in the southern than in the northern part. On the other hand, physical conditions of deformation during the exhumation stage have been independently inferred from microstructures in deformed quartz. Recrystallized quartz grains in rocks from the low-grade (chlorite and garnet) zones are much more stretched in the southern part (aspect ratio ≥ 4.0) than in the northern part (aspect ratio〈 4.0), indicating a higher strain rate in the former than in the latter. These facts may indicate that the exhumation and strain rates are correlated (i.e. the exhumation rate increases with increasing the strain rate). The difference in the exhumation rate inferred from amphibole zoning between the northern and southern parts could be explained by an extensional model involving normal faulting, where the lower plate can be exhumed faster than the upper plate due to the displacement along the fault. Furthermore, the model may explain the positive correlation between the exhumation and strain rates, because the lower plate tended to support more stress than the upper plate.

Notes: The loss of a metamorphic fluid via the partitioning of H2O into silicate melt at higher metamorphic grade implies that, in the absence of open system behaviour of melt, the amount of H2O contained within rocks remains constant at temperatures above the solidus. Thus, granulite facies rocks, composed of predominantly anhydrous minerals and a hydrous silicate melt should undergo considerable retrogression to hydrous upper amphibolite facies assemblages on cooling as the melt crystallizes and releases its H2O. The common occurrence of weakly retrogressed granulite facies assemblages is consistent with substantial melt loss from the majority of granulite facies rocks. Phase diagram modelling of the effects of melt loss in hypothetical aluminous and subaluminous metapelitic compositions shows that the amount of melt that has to be removed from a rock to preserve a granulite facies assemblage varies markedly with rock composition, the number of partial melt loss events and the P–T conditions at which melt loss occurs. In an aluminous metapelite, the removal of nearly all of the melt at temperatures above the breakdown of biotite is required for the preservation of the peak mineral assemblage. In contrast, the proportion of melt loss required to preserve peak assemblages in a subaluminous metapelite is close to half that required for the aluminous metapelite. Thus, if a given proportion of melt is removed from a sequence of metapelitic granulites of varying composition, the degree of preservation of the peak metamorphic assemblage may vary widely.

Notes: Mixing properties for muscovite–celadonite–ferroceladonite solid solutions are derived from combining available experimental phase equilibrium data with tabulated thermodynamic data for mineral end-members. When a partially ordered solution model is assumed, the enthalpy of mixing among the end-members muscovite–celadonite–ferroceladonite is nearly ideal, although the Gibbs energies of muscovite–celadonite and muscovite–ferroceladonite solutions are asymmetric due to an asymmetry in the entropy of mixing. Thermodynamic consistency is achieved for data on phengite compositions inassemblages with (a) pyrope+kyanite+quartz/coesite (b) almandine+kyanite+quartz/coesite (c)talc+kyanite+quartz/coesite and (d) garnet–phengite pairs equilibrated both experimentally at high temperatures and natural pairs from low-grade schists. The muscovite–paragonite solvus has been reanalysed using the asymmetric van Laar model, and the effects of the phengite substitution into muscovite have been quantitatively addressed in order to complete the simple thermodynamic mixing model for the solid solution among the mica end-members. Results are applied to a natural pyrope–coesite–phengite–talc rock from the Western Alps, and to investigate the conditions under which biotite-bearing mica schists transform to whiteschist-like biotite-absent assemblages for average pelite bulk compositions.

Notes: Three texturally distinct symplectites occur in mafic granofels of the Arthur River Complex at MtDaniel, Fiordland, New Zealand. These include symplectic intergrowths of clinopyroxene and kyanite, described here for the first time. Pods of mafic granofels occur within the contact aureole of the Early Cretaceous Western Fiordland Orthogneiss batholith. The pods have cores formed entirely of garnet and clinopyroxene, and rims of pseudomorphous coarse-grained symplectic intergrowths of hornblende and clinozoisite that reflect hydration at moderate to high-P. These hornfelsic rocks are enveloped by a hornblende–clinozoisite gneissic foliation (S1). Narrow garnet reaction zones, in which hornblende and clinozoisite are replaced by garnet–clinopyroxene assemblages, developed adjacent to fractures and veins that cut S1. Fine-grained symplectic intergrowths of (1) clinopyroxene and kyanite and (2) clinozoisite, quartz, kyanite and plagioclase form part of the garnet reaction zones and partially replace coarse-grained S1 hornblende and clinozoisite. The development of the garnet reaction zones and symplectites was promoted by dehydration most probably following cooling of the contact aureole. Maps of oxide weight percent and cation proportions, calculated by performing matrix corrections on maps of X-ray intensities, are used to study the microstructure of the symplectites.

Notes: Eclogite facies carbonate rocks have been discovered associated with the granulite–eclogite transitional rocks within Bergen Arc system, Caledonian Orogen of western Norway. The local occurrences of marbles and calc-silicates are found subparallel to the mafic eclogite facies shear zones on Holsnøy Island. Marbles contain the assemblage calcite (Ca0.99Sr0.01CO3), calcian strontianite (Ca0.18−0.44Sr0.53−0.84CO3), clinopyroxene (Jd7−32), epidote/allanite (Ps0−33), titanite, garnet (Alm52−56Grs28−33Pyp11−16), barite (Ba0.90−0.99Sr0.01−0.10SO4), celestine (Sr0.67−0.98Ba0.01−0.23Ca0.01−0.11SO4), and one apparently homogeneous grain of intermediate composition (Ba0.49Ca0.01Sr0.50SO4). Adjacent eclogites have clinopyroxene with similar jadeite contents (Jd14−34) and similar garnet (Alm51−60Grs26−36Pyp8−14) compositions. The marbles have high contents of Sr (9500–11000 p.p.m) and Y (115–130 p.p.m). However, low concentrations of some key trace elements (110–160 p.p.m. Ba and 〈5 p.p.m. Nb) appear to indicate that the marble is not a metamorphosed carbonatite. The 87Sr/86Sr ratios range from 0.7051 to 0.7059. Field and petrological relationships suggest that metasomatic reactions and fluids played a significant role in producing and/or modifying the marbles. The breakdown of scapolite in the granulite into carbonates and sulphates during eclogite facies metamorphism may have contributed to the metasomatic formation of the marbles along shear zones.Fluids involved during subduction are an important catalyst for metamorphism and are recognized to have played a critical role in the localized transformation from granulite to eclogite in the Holsnøy Island area. Thermobarometry indicates 640–690 °C and 18–20 kbar for adjacent eclogites and temperatures of 580–650 °C for the calc-silicates. The marble assemblages are consistent with fluid that is dominantly comprised of H2O (XCO2 〈 0.03) under high-pressure conditions. Phase equilibria of the marbles constrain the fO2 of the fluids and imply oxidizing conditions of the deep crustal fluids. At present the source of the fluids remains unresolved. The results provide additional insights into the variable and evolving nature of fluids related to subduction and high-pressure metamorphism.

Notes: We formulate an algorithm for the calculation of stable phase relations of a system with constrained bulk composition as a function of its environmental variables. The basis of this algorithm is the approximate representation of the free energy composition surfaces of solution phases by inscribed polyhedra. This representation leads to discretization of high variance phase fields into a continuous mesh of smaller polygonal fields within which the composition and physical properties of the phases are uniquely determined. The resulting phase diagram sections are useful for understanding the phase relations of complex metamorphic systems and for applications in which it is necessary to establish the variations in rock properties such as density, seismic velocities and volatile-content through a metamorphic cycle. The algorithm has been implemented within a computer program that is general with respect to both the choice of variables and the number of components and phases possible in a system, and is independent of the structure of the equations of state used to describe the phases of the system.

Notes: Migmatitic cordierite gneisses within the Achankovil Zone (AZ) of southern Pan-African India record melt-producing and subsequent melt-consuming mineral reactions. Early mineral assemblages Bt-Sil-Qtz and Bt-Sil-Spl, deduced from inclusion textures in garnet prophyroblasts, break down via successive dehydration melting reactions to high-T phase assemblages (e.g. Grt-Crd-Liq, Opx-Liq, Spl-Crd-Liq). Later back reactions between the restite and the in situ crystallizing melt resulted in thin cordierite coronas separating garnet from the leucosome, and partial resorption of garnet to Opx-Crd or Crd-Bt-Qtz symplectites. Leucosomes generally display a moderate (low-strain gneisses) to strong (high-strain gneisses) depletion of alkali feldspar attributed to mineral-melt back reactions partly controlled by the degree of melt segregation.Using a KFMASH partial petrogenetic grid that includes a melt phase, and qualitative pseudosections for microdomains of high and low Al/Si ratios, the successive phase assemblages and reaction textures are interpreted in terms of a clockwise P–T path culminating at about 6–7 kbar and 900–950 °C. This P–T path is consistent with, but more detailed than published results, which suggests that taking a melt phase into account is not only a valid, but also a useful approach. Comparing P–T data and lithological and isotopic data for the AZ with adjacent East Gondwana fragments, suggests the presence of a coherent metasedimentary unit exposed from southern Madagascar via South India (AZ) and Sri Lanka (Wanni Complex) to the Lützow–Holm Bay in Eastern Antarctica.

Notes: Fine grained rodingite-like rocks containing epidote, clinozoisite, garnet, chlorite, phengite and titanite occur within antigorite serpentinite boudins from the high-pressure metamorphic Maksyutovo Complex in the Southern Urals. Pseudomorphs after lawsonite, resorption of garnet by chlorite and phengite and stoichiometry suggest the reaction lawsonite + garnet + K-bearing fluid → clinozoisite + chlorite + phengite, and define a relic assemblage of lawsonite + garnet + chlorite + titanite ± epidote as well as a later post-lawsonite assemblage of clinozoisite + phengite + chlorite + titanite. The reaction lawsonite + titanite → clinozoisite + rutile + pyrophyllite + H2O delimits the maximum stability of former lawsonite + titanite to pressures 〉13 kbar. P–T conditions of 18–21 kbar/520–540 °C result, if the average chlorite, Mg-rich garnet rim and average epidote compositions are used as equilibrium compositions of the former lawsonite assemblage. These estimates indicate a similar depth of formation but lower temperatures to those recorded in nearby eclogites. The metamorphic conditions of the lawsonite assemblage are considerably higher than previously suggested and, together with published structural data, support a model in which a normal fault within the Maksyutovo complex acted as the major transport plane of eclogite exhumation.The maximum Si content of phengite and minimum Fe content in clinozoisite constrain the metamorphic conditions of the later pseudomorph assemblage to be 〉4.5 kbar and 〈440 °C. Rb–Sr isotopic dating of the pseudomorph assemblage results in a formation age of 339 ± 6 and 338 ± 5 Ma, respectively. These results support the recent exhumation models for this complex.

Notes: Exotic blocks of eclogite from distant localities along the Northern Serpentinite Melange of Cuba have comparable P–T histories that include high-pressure prograde sections (450–600 °C, 〉15 kbar) associated with subduction of oceanic lithosphere, and retrograde sections within the albite–epidote amphibolite facies (〈500 °C, 〈10 kbar) related to melange uplift. 40Ar/39Ar and Rb/Sr cooling ages (118–103 Ma) of one of the blocks indicate pre-Aptian subduction and Aptian–Albian uplift. Detailed X-ray imaging and profiling further reveals that minerals in these eclogite blocks (notably garnet and amphibole) display subtle but well defined oscillatory zoning that developed along the prograde trajectory of the rocks, previous to attainment of peak eclogitic conditions. The chemistry (e.g. coupled changes of Mg# and Mn in garnet, and of Si, Ti, Al and Na in amphibole) and geometry (euhedral to anhedral shapes) of the oscillations can be interpreted in terms of subtle fluctuations in P–T during the general prograde subduction-related metamorphic path. A (near-) equilibrium model is presented for the formation of oscillations at near peak conditions by means of recurrent dissolution-growth reaction processes. This model for near-peak conditions, and the chemical signatures of earlier oscillations (notably in amphibole), suggest that episodes of retrogression (upward movement?) affected parts of the subducting slab. It is proposed that these retrograde episodes record the tectonic rupture of the subducting slab and, probably, of the upper plate mantle, either due to the intrinsic dynamic behaviour of subduction systems or to the effects of the plate-tectonic rearrangement of the Caribbean region during the Early Cretaceous.

Notes: The relative timing of two discrete pulses of metamorphic fluid flow is constrained based on chemical zoning in several garnet crystals from Kvaløya, Troms, northern Norway. The garnet crystals measured 1–2 cm in diameter and were contained within c. 1.6 Ga, staurolite grade metasediments. Major element zoning indicates that garnet grew under normal prograde conditions in the garnet and/or staurolite zones.Timing constraints are based on comparisons between major and trace element chemical zoning, oxygen isotope (δ18O) zoning and deformational (inclusion trail) zoning in one of the garnet. We interpret at least two pulses of metamorphic fluid flow. The first pulse occurred during the syn-tectonic growth interval. The δ18O zoning was reversed relative to ‘normal’ prograde zoning and the δ18O maximum was located within the syn-tectonic growth zone, displaced 3–4 mm from the garnet core. The fluid might have been sourced in neighbouring calcareous pelites and may also have caused formation of an Y ring. The second (and subsequent) pulse(s) occurred during/after the post-tectonic growth interval. δ18O was locally increased at the garnet rim, particularly where the rim was sheared. The incomplete rim was also enriched in calcium. Transport of oxygen and calcium by metamorphic fluids is well documented. Transport of Y is both problematic and poorly understood, but might have been facilitated by complexing with F and/or CO2.

Notes: Creation of pathways for melt to migrate from its source is the necessary first step for transport of magma to the upper crust. To test the role of different dehydration-melting reactions in the development of permeability during partial melting and deformation in the crust, we experimentally deformed two common crustal rock types. A muscovite-biotite metapelite and a biotite gneiss were deformed at conditions below, at and above their fluid-absent solidus. For the metapelite, temperatures ranged between 650 and 800 °C at Pc=700 MPa to investigate the muscovite-dehydration melting reaction. For the biotite gneiss, temperatures ranged between 850 and 950 °C at Pc=1000 MPa to explore biotite dehydration-melting under lower crustal conditions. Deformation for both sets of experiments was performed at the same strain rate (ε.) 1.37×10−5 s−1. In the presence of deformation, the positive ΔV and associated high dilational strain of the muscovite dehydration-melting reaction produces an increase in melt pore pressure with partial melting of the metapelite. In contrast, the biotite dehydration-melting reaction is not associated with a large dilational strain and during deformation and partial melting of the biotite gneiss melt pore pressure builds more gradually. Due to the different rates in pore pressure increase, melt-enhanced deformation microstructures reflect the different dehydration melting reactions themselves. Permeability development in the two rocks differs because grain boundaries control melt distribution to a greater extent in the gneiss. Muscovite-dehydration melting may develop melt pathways at low melt fractions due to a larger volume of melt, in comparison with biotite-dehydration melting, generated at the solidus. This may be a viable physical mechanism in which rapid melt segregation from a metapelitic source rock can occur. Alternatively, the results from the gneiss experiments suggest continual draining of biotite-derived magma from the lower crust with melt migration paths controlled by structural anisotropies in the protolith.

Notes: Observations of oriented SiO2 precipitates in omphacite from eclogite with tholeiitic basalt protolith bordering the Alpe Arami garnet peridotite massif, Ticino, Switzerland, and petrological studies of the eclogitic mineral assemblages, suggest that this rock was subjected to higher-pressure metamorphism than previously realized. We employed various calibrations of the Fe2+ − Mg exchange thermometer and calculations of equilibria with thermodynamic data, considering the calcium–Tschermak's component (CaAl2SiO6), of garnet-pyroxene pairs. From these calculations, it is concluded that the eclogitic lenses have recorded at least four stages of mineral growth corresponding to the following: Stage I (prograde) c. 2.4 GPa; 700 °C; Stage IIa (maximum recorded grade) c. 7.0 GPa; 1100 °C; Stage IIb (retrograde) c. 3.7 GPa; 900 °C; Stage III (retrograde) c. 2.1 GPa; 750 °C. Because of the preservation of Stage I, a relatively rapid subduction and exhumation of Alpe Arami eclogite is suggested. The exhumation path of the eclogitic rock is in good agreement with most exhumation paths inferred for the Alpe Arami garnet lherzolite proposed previously by several authors based upon a variety of different observations, although the eclogite and peridotite exhumation paths may diverge at depths greater than 120 km.

Notes: The Tenda crystalline massif (northern Corsica) is a fragment of the western Corsica basement involved in the Alpine orogeny. Rhyolite dykes crosscutting the gabbroic complex of Bocca di Tenda (southern sector of the Tenda crystalline massif) show an unusual metamorphic mineral assemblage, defined by jadeite-bearing (up to 46 mol percentage) aegirine, riebeckite, celadonite-rich phengite (Si=3.50–3.65 apfu), quartz, albite and K-feldspar. Jadeite-bearing aegirine and riebeckite mostly occur as coronas around jadeite-free aegirine and arfvedsonite, respectively, which both are relics of igneous origin. This metamorphic assemblage reflects the peralkaline compositions, which are characterised by anomalously high contents of SiO2 and Na2O, and negligible CaO and MgO. The evolved rocks of the gabbroic sequence (quartz-diorites to tonalites) and the surrounding granitoids are characterised by the development of riebeckite/ferroglaucophane, epidote, celadonite-rich phengite and albite, thus pointing to a metamorphic crystallization in the epidote-blueschist facies. In all the studied rocks, metamorphic reactions were controlled by fluid-assisted mass-transfer through grain boundaries and microfractures. The different mineral assemblages allow the peak P–T metamorphic conditions to be constrained to between 0.8 GPa/300 °C and 1.1 GPa/500 °C. These estimates attest to a geothermal gradient (dT/dP) of 10–13 °C km−1 and indicate that the Tenda crystalline massif was buried to a minimum depth of 27 km during the Alpine orogeny. The blueschist facies recrystallization in the Tenda crystalline massif has been related to the cessation of an eastward-dipping subduction event.

Notes: Growth rates of wollastonite reaction rims between quartz and calcite were experimentally determined at 0.1 and 1 GPa and temperatures from 850 to 1200 °C. Rim growth follows a parabolic rate law indicating that this reaction is diffusion-controlled. From the rate constants, the D′δ-values of the rate-limiting species were derived, i.e. the product of grain boundary diffusion coefficient D′ and the effective grain boundary width, δ. In dry runs at 0.1 GPa, wollastonite grew exclusively on quartz surfaces. From volume considerations it is inferred that (D′CaOδ)/(D′SiO2δ)≥1.33, and that SiO2 diffusion controls rim growth. D′SiO2δ increases from about 10−25 to 10−23 m3 s−1 as temperature increases from 850 to 1000 °C, yielding an apparent activation energy of 330±36 kJ mol−1. In runs at 1 GPa, performed in a piston-cylinder apparatus, there were always small amounts of water present. Here, wollastonite rims always overgrew calcite. Rims around calcite grains in quartz matrix are porous and their growth rates are controlled by a complex diffusion-advection mechanism. Rim growth on matrix calcite around quartz grains is controlled by grain boundary diffusion, but it is not clear whether CaO or SiO2 diffusion is rate-limiting. D′δ increases from about 10−21 to 10−20 m3 s−1 as temperature increases from 1100 to 1200 °C. D′SiO2δ or D′CaOδ in rims on calcite is c. 10 times larger than D′SiO2δ in dry rims at the same temperature. Growth structures of the experimentally produced rims are very similar to contact-metamorphic wollastonite rims between metachert bands and limestone in the Bufa del Diente aureole, Mexico, whereby noninfiltrated metacherts correspond to dry and brine-infiltrated metacherts to water-bearing experiments. However, the observed diffusivities were 4 to 5 orders of magnitude larger during contact-metamorphism as compared to our experimental results.

Notes: Grasslands dominated by Sporobolus wrightii (big sacaton) once covered riparian floodplains in southwestern United States and northern Sonora, Mexico but now occupy less than 5% of their historic range, mostly due to clearing for agriculture. Many agricultural fields have been abandoned because of changing land uses, and efforts are under way to restore native grassland habitat. Arbuscular mycorrhizal (AM) fungi are known to form associations with S. wrightii and can be a potential factor in grassland restoration efforts. The goal of this study was to determine the effects of mycorrhizal inoculation on S. wrightii during transplant production and in a restoration trial. Sporobolus wrightii was grown with and without AM fungi in 2.8-L tall pots and 150-mL nursery containers under greenhouse conditions for 8 weeks and then transplanted into an abandoned agricultural field. Plants were monitored for growth, survival, and mycorrhizal infection. Seedling emergence in the greenhouse was higher in pots with mycorrhizal inoculation, but inoculation had little effect on growth except more tillers were produced by pre-inoculated plants grown in the smaller containers. In the abandoned field, pre-inoculated plants had greater survival, basal diameter, and tiller and panicle production through the first two growing seasons. Plants started in smaller containers also had greater survival, height, basal diameter, and tiller production than those started in tall pots. Root colonization was detected in all plants by 2 months after transplanting but was not consistent throughout the experiment except for pre-inoculated plants started in the smaller containers. These results indicate that mycorrhizal inoculation can benefit restoration efforts in abandoned agriculture fields in semiarid regions.

Notes: To control shrubs, which are increasing in dominance in wetlands worldwide, winter burning may be an important tool, especially from the perspective of minimizing urban hazards. The goal of this project was to determine if winter burning was successful in reducing the dominance (mean percentage cover and maximum height) of Cornus sericea in sedge meadows in southern Wisconsin, where shrubs proliferated after cattle were excluded. Experimental burn and control plots were set up within sedge meadows, including an ungrazed “reference” site that had been little, if ever, grazed and a “historically grazed” site, a recovery site that had not been grazed by cattle since 1973. None of the dominant species including C. sericea was significantly affected by burning for either mean percentage cover or maximum height (analysis of variance: no burning × species interaction). Both mean percentage cover and maximum height were only weakly related to burning (28.1 and 14.3% of the variability contributed to the cumulative percentage of the coefficient of determination, respectively) at both sites based on non-metric multidimensional scaling analysis. Although species richness increased in burned plots in 1999 and 2000, no differences were apparent between pre-burned and unburned plots in 1997 and unburned plots in 1999 and 2000 (analysis of variance: year × burning interaction). After burning in the ungrazed site, herbaceous species appeared that had not been detected for decades, including Chelone glabra and Lathyrus palustris. Exotic species were present in both the ungrazed reference and recovery site. Although winter burning treatments did not reduce the dominance of woody shrub species in the site recovering from cattle grazing, burning was useful in stimulating the maintenance of species richness in the ungrazed sedge meadow.

Notes: In 1980 the State of Connecticut began a tidal marsh restoration program targeting systems degraded by tidal restrictions and impoundments. Such marshes become dominated by common reed grass (Phragmites australis) and cattail (Typha angustifolia and T. latifolia), with little ecological connection to Long Island Sound. The management and scientific hypothesis was that returning tidal action, reconnecting marshes to Long Island Sound, would set these systems on a recovery trajectory. Specific restoration targets (i.e., pre-disturbance conditions or particular reference marshes) were considered unrealistic. However, it was expected that with time restored tides would return ecological functions and attributes characteristic of fully functioning tidal salt marshes. Here we report results of this program at nine separate sites within six marsh systems along 110 km of Long Island Sound shoreline, with restoration times of 5 to 21 years. Biotic parameters assessed include vegetation, macroinvertebrates, and use by fish and birds. Abiotic factors studied were soil salinity, elevation and tidal flooding, and soil water table depth. Sites fell into two categories of vegetation recovery: slow, ca. 0.5%, or fast, more than 5% of total area per year. Although total cover and frequency of salt marsh angiosperms was positively related to soil salinity, and reed grass stand parameters negatively so, fast versus slow recovery rates could not be attributed to salinity. Instead, rates appear to reflect differences in tidal flooding. Rapid recovery was characterized by lower elevations, greater hydroperiods, and higher soil water tables. Recovery of other biotic attributes and functions does not necessarily parallel those for vegetation. At the longest studied system (rapid vegetation recovery) the high marsh snail Melampus bidentatus took two decades to reach densities comparable with a nearby reference marsh, whereas the amphipod Orchestia grillus was well established on a slow-recovery marsh, reed grass dominated after 9 years. Typical fish species assemblages were found in restoration site creeks and ditches within 5 years. Gut contents of fish in ditches and on the high marsh suggest that use of restored marsh as foraging areas may require up to 15 years to reach equivalence with reference sites. Bird species that specialize in salt marshes require appropriate vegetation; on the oldest restoration site, breeding populations comparable with reference marshland had become established after 15 years. Use of restoration sites by birds considered marsh generalists was initially high and was still nearly twice that of reference areas even after 20 years. Herons, egrets, and migratory shorebirds used restoration areas extensively. These results support our prediction that returning tides will set degraded marshes on trajectories that can bring essentially full restoration of ecological functions. This can occur within two decades, although reduced tidal action can delay restoration of some functions. With this success, Connecticut's Department of Environmental Protection established a dedicated Wetland Restoration Unit. As of 1999 tides have been restored at 57 separate sites along the Connecticut coast.

Notes: Tidal flow to salt marshes throughout the northeastern United States is often restricted by roads, dikes, impoundments, and inadequately sized culverts or bridge openings, resulting in altered ecological structure and function. In this study we evaluated the response of vegetation and nekton (fishes and decapod crustaceans) to restoration of full tidal flow to a portion of the Sachuest Point salt marsh, Middletown, Rhode Island. A before, after, control, impact study design was used, including evaluations of the tide-restricted marsh, the same marsh after reintroduction of tidal flow (i.e., tide-restored marsh), and an unrestricted control marsh. Before tidal restoration vegetation of the 3.7-ha tide-restricted marsh was dominated by Phragmites australis and was significantly different from the adjacent 6.3-ha Spartina-dominated unrestricted control marsh (analysis of similarities randomization test, p 〈 0.001). After one growing season vegetation of the tide-restored marsh had changed from its pre-restoration condition (analysis of similarities randomization test, p 〈 0.005). Although not similar to the unrestricted control marsh, Spartina patens and S. alterniflora abundance increased and abundance and height of Phragmites significantly declined, suggesting a convergence toward typical New England salt marsh vegetation. Before restoration shallow water habitat (creeks and pools) of the unrestricted control marsh supported a greater density of nekton compared with the tide-restricted marsh (analysis of variance, p 〈 0.001), but after one season of restored tidal flow nekton density was equivalent. A similar trend was documented for nekton species richness. Nekton density and species richness from marsh surface samples were similar between the tide-restored marsh and unrestricted control marsh. Fundulus heteroclitus and Palaemonetes pugio were the numerically dominant fish and decapod species in all sampled habitats. This study provides an example of a quantitative approach for assessing the response of vegetation and nekton to tidal restoration.

Notes: A growing number of studies have assessed the functional equivalency of restored and natural salt marshes. Several of these have explored the use of functional trajectories to track the increase in restored marsh function over time; however, these studies have disagreed as to the usefulness of such models in long-term predictions of restored marsh development. We compared indicators of four marsh functions (primary production, soil organic matter accumulation, sediment trapping, and maintenance of plant communities) in 6 restored and 11 reference (matched to restored marshes using principal components analysis) salt marshes in the Great Bay Estuary. The restored marshes were all constructed and planted on imported substrate and ranged in age from 1 to 14 years. We used marsh age in a space-for-time substitution to track constructed salt marsh development and explore the use of trajectories. A high degree of variability was observed among natural salt marsh sites, displaying the importance of carefully chosen reference sites. As expected, mean values for constructed site (n = 6) and reference site (n = 11) functions were significantly different. Using constructed marsh age as the independent variable and functional indicator values as dependent variables, nonlinear regression analyses produced several ecologically meaningful trajectories (r 2〉 0.9), demonstrating that the use of different-aged marshes can be a viable approach to developing functional trajectories. The trajectories illustrated that although indicators of some functions (primary production, sediment deposition, and plant species richness) may reach natural site values relatively quickly (〈10 years), others (soil organic matter content) will take longer.

Notes: Fiordland, New Zealand exposes the lower crustal root of an Early Cretaceous magmatic arc that now forms one of Earth's most extensive high-P granulite facies belts. The Arthur River Complex, a dioritic to gabbroic suite in northern Fiordland, is part of the root of the arc, and records an Early Cretaceous history of emplacement, tectonic burial, and high-P granulite facies metamorphism that accompanied partial melting of the crust. Late random intergrowths of kyanite, quartz and plagioclase partially pseudomorph minerals in the earlier high-T assemblages of the Arthur River Complex, indicating high-P cooling of an over thickened crustal root by c. 200 °C. The kyanite intergrowths are themselves partially pseudomorphed by paragonite, commonly in the presence of phengitic white mica. Biotite–plagioclase intergrowths that partially pseudomorph phengitic white mica and diopside–plagioclase intergrowths that partially pseudomorph jadeitic diopside, combined with published thermochronology results, are consistent with later rapid decompression. A short duration anticlockwise P–T path may be explained by the high-P juxtaposition of comparatively cool upper crustal rocks following their tectonic burial and under thrusting during the waning stages of Early Cretaceous orogenesis. This was then followed by the decompression giving the rapid exhumation within 20 Myr of peak metamorphism, as suggested by the isotopic data.