ALBERT

Notes: Analysis of the precision of the illite ‘crystallinity’technique shows that machine errors are 〈5%, while intra- and inter-sample errors are variable but are up to 12% and 14%, respectively (1σ). Consideration of this error analysis shows that the isocryst approach, which involves close contouring (e.g. 0.03 Δ2°) of illite ‘crystallinity’data, has a very low degree of confidence (〈0.5) and thus is not regarded as statistically valid. If contouring is to be undertaken with a high degree of confidence (〉0.8) it is necessary that contours should be at intervals of 0.1 ΔΘ2°, which is equivalent to subdivision of the anchizone into upper and lower units. Where previous interpretations have relied upon an isocryst method of contouring at less than 0.1 ΔΘ2° the conclusions must be regarded as unsubstantiated.Centrifuge separation of clay fractions (based on a Stokes’law application) gives separations in which a significant, but variable, percentage of grains have long axes greater than the size calculated. For the typical 〈2-μm fraction utilized, some 20% of grains lie in the 2–4-μm range, although the proportion is not believed to have a significant effect upon ‘crystallinity’values. The formula is applicable for grain-sizes down to 0.5 μm. Illite ‘crystallinity’values on samples prepared by an ultrasonic disaggregation method show a small increase on those prepared by ball mill crushing. The differences are minimal at the epi/anchizone level but increase to some 10% at the anchizone/diagenetic level. The effect on grade determinations is again thought to be minimal and indicates that concern over unsuitability of the ultrasonic disaggregation method is unfounded.

Notes: The amphibolite facies Puolankajärvi Formation (PjF) occupies the western margin of the Early Proterozoic Kainuu Schist Belt (KSB) of northern Finland. The lower and middle parts of the PjF consist of turbiditic psammites and pelites and tempestitic semipelites. This report concentrates on the pelitic lithologies which include quartz–two-mica–plagioclase schists with variable amounts of garnet, staurolite, andalusite and biotite porphyroblasts as well as sillimanite and cordierite segregations.The KSB forms a major north–south-trending synclinorium between two Archaean blocks. It contains both autochthonous and allochthonous units and is cut by faults and shear zones. The PjF lies on the western side of the KSB and is probably allochthonous. The formation has undergone six major deformation phases (D1, D2, D3a, D3b, D4 and D5). During D3a-D5 the maximum principal stress (σ1) changed in a clockwise direction from south-west to north-east. Between D2 and D3 the intermediate principal stress (σ2) changed from horizontal to vertical and the interval between D2 and D3 marks a transition from thrust to strike-slip tectonics.Relict structures in the porphyroblasts indicate the following mineral growth–deformation evolution in the PjF. (1) Throughout the PjF there was a successive crystallization of garnet (syn-D1), poryphyroblastic biotite (inter-D3/4) and staurolite (inter-D3/4) during the pre-D4 stage. (2) A syn-D4-inter-D4/5 crystallization of kyanite, sillimanite (fibrolite), porphyroblastic tourmaline, magnetite, rutile, cordierite and muscovite–biotite–plagioclase pseudomorphs after staurolite was most localized at and near D4 shear zones. (3) A syn- to post-D5 generation of andalusite, ilmenohematite and sheet silicates after staurolite and after cordierite occurred near D5 faults.The evolution outlined here permits the relative dating of the PjF parageneses, which is used in the second part of the study (Tuisku & Laajoki, 1990), and, together with the knowledge of the pressure–temperature conditions during various growth events, makes it possible to compile pressure–temperature–deformation paths for the PjF.

Notes: Within the Çokkul synform, Caledonian metamorphic rocks of the Middle Köli Nappe Complex (MKNC) are in low-angle fault contact with the basement mylonites derived from the Precambrian Tysfjord granite-gneiss. In the synform, the MKNC is composed of four fault-bounded nappes each of which has a distinct tectonic stratigraphy composed of amphibolite-facies metamorphosed pelitic and psammitic schists with minor lensoidal bodies of mafic and ultramafic rocks.Pelitic rocks from the three structurally lowest nappes contain the low-variance AFM mineral assemblages gar + bio + staur and staur + ky + bio with mu + qtz + ilm, whereas staur and ky are absent from the highest nappe, the Kallakvare nappe. AFM mineral assemblages in the three lowest nappes indicate peak metamorphic temperatures of 610–660°C and peak pressures in excess of 600 MPa. Mineral assemblages from the Kallakvare nappe are not as diagnostic of metamorphic grade. However, rocks from that nappe contain coexisting plagioclases from both sides of the peristerite gap, suggesting lower-grade peak P–T conditions than those of the structurally lower nappes. In addition, biotite from the lower nappes is more Ti-rich than biotite from the Kallakvare nappe. However, gar–bio–mu–plag and gar–bio–ky–plag–qtz thermobarometry suggests that all four nappes equilibrated at approximately 525 ± 25°C and 700 ± 100 MPa.Gibbs method thermodynamic modelling of garnet zoning profiles suggests that the lower three nappes followed clockwise P–T paths that involved heating and compression to a metamorphic peak of approximately 575–625°C, 800 MPa followed by cooling and decompression to 525°C, 700 MPa. P–T paths calculated for the Kallakvare nappe show decompression and minor heating to a peak T of 500–525°C. In the lower nappes, staur and ky grew during the heating phase not seen by the highest nappe. The outer parts of the paths from all four nappes are approximately parallel, possibly recording the emplacement of the Kallakvare nappe onto the already stacked lower three nappes at some time following the metamorphic peak. These P–T paths suggest that the sole fault of the Kallakvare nappe is a normal fault. Garnet zonation thus appears to record a previously unrecognized phase of uplift and tectonic thinning of the MKNC. This event appears to be restricted to the MKNC and to have occurred prior to the emplacement of the MKNC onto the Tysfjord granite-gneiss basement of Baltoscandia under greenschist-facies conditions. It may have been responsible for the uplift and cooling of the MKNC from 25–30 km amphibolite-facies conditions prior to its emplacement onto Baltoscandia under 15–20 km greenschist-facies conditions.The deformation zone associated with this normal fault is relatively narrow, generally less than 1 m thick. If this is typical of other detachment faults in the metamorphic infrastructure of the Scandinavian Caledonides, they may be relatively common, but not often recognized due to the detailed study needed to document them.

Notes: Numerical models of the progressive evolution of pelitic schists in the NCMnKFMASH system with the assemblage garnet + biotite + chlorite ± staurolite + plagioclase + muscovite + quartz + H2O are presented with the goal of predicting compositional changes in garnet and plagioclase along different P-T paths. The numerical models support several conclusions that should prove useful for interpreting the P-T paths of natural parageneses: (i) Garnet may grow along P-T vectors ranging from heating with decompression to cooling with compression. P-T paths deduced from garnet zoning that are inconsistent with these growth vectors are self-contradictory. (ii) There is a systematic relation between garnet and plagioclase composition and growth such that for most P-T paths, garnet growth requires plagioclase consumption. Furthermore, mass balance in a closed system requires that as plagioclase is consumed the remaining plagioclase becomes increasingly albitic. Inclusions of plagioclase in the core of garnet should be more anorthitic than those near the rim and zoned matrix plagioclase should have rims that are more albitic than the cores. Complex plagioclase textures may arise from the local variability of growth and precipitation kinetics. (iii) A decrease of Fe/(Fe + Mg) in a garnet zoning profile is a reliable indicator of increasing temperature for the assemblage modelled. However, there is no single reliable ΔP monitor and inferences about ΔP can only be made by considering plagioclase and garnet together. (iv) Consumption of garnet during the production of staurolite removes material from the outer shell of a garnet and may make recovery of peak metamorphic compositions and P-T conditions impossible. Low ‘peak’temperatures typically recorded by staurolite-bearing assemblages may reflect this phenomenon. (v) Diffusional homogenization of garnet affects the computed P-T path and results in a clockwise rotation of the computed P-T vector relative to the true P-T path.

Notes: The equilibrium thermodynamics of the reaction:And the equilibrium constant is composed of activities formulated using ideal mixing on sites. Consideration is given to the evaluation of uncertainties in pressures calculated using the geobarometer. Preliminary testing suggests that the geobarometer has considerable potential. Much wider testing is now required.

Notes: Abstract. Pink piemontite-spessartine-bearing and grey-green spessartine-bearing manganiferous quartzose schists derived from siliceous pelagites, and green quartzofeldspathic schists, are described from the greenschist facies of the Haast Schist terrane, near Arrow Junction, western Otago. Electron microprobe data are reported for sphene, spessartine-rich garnet, manganoan epidote, piemontite, tourmaline, phengitic muscovite, chlorite, albite, haematite, rutile, manganoan calcite and chalcopyrite.Metamorphism occurred at about 6.4kbar, 400°C. Xco2 was above the quartz-rutile-calcite-sphene buffer (Xco2± 0.02) throughout the recorded metamorphic history of the piemontite schists. It dropped from above to below this critical buffering value in a spessartine-rich schist and it was close to or below the buffering value in the quartzofeldspathic schists. Production of piemontite required high fO2, believed to be inherited from MnOx in the parent pelagite. Substantial loss of O2 (e.g. minimum of 0.19% by weight in one rock) during diagenesis and/or metamorphism is inferred. In the grey-green schists this inhibited piemontite formation. Slight loss of O2 and Ca2+ accompanied minor late-stage replacement of piemontite by second generation spessartine. Observed zoning and mineral replacements indicate rise of temperature, drop in pressure, or invasion by solutions of lower fO2 and XCO2 equilibrated with surrounding schists.The detailed chemistry of the minerals studied correlates with available Mn and with bulk-rock (Fe3+ x 100)/(Fe2++ Fe3+). The oxidation ratio ranges from 24 in average green quartzofeldspathic schist, through 78 in average grey-green manganiferous quartzose schist, to almost 100 in some piemontite-bearing schists. As Fe2+ gives way to Fe3+, Mg/Fe ratios tend to rise in chlorite, phengite, tourmaline, spessartine, and calcite, Mn increases and Ti decreases in haematite, Mn increases in spessartine and calcite, and Fe increases in rutile. Available divalent cations are depleted relative to Al; chlorite is more aluminous, and phengite more paragonitic than in typical Haast schists.

Notes: Field, petrographic and microprobe investigations of metaclastic rocks, calcareous schists, marbles, chloritic calcareous meta-volcanic units and schists/paragneisses which crop out along the eastern portion of the Central East-West Cross Island Highway in Taiwan demonstrate that metamorphic intensity gradually increases eastward. The lower greenschist facies Slate Formation on the W contains completely recrystallized, pure albitic plagioclase, but at least some of the white micas (± chlorites) probably represent relict detrital flakes. Neo-blastic biotite and epidote occur sporadically in the Pihou(?) Formation, and increase dramatically eastward; concomitantly the abundance of carbonaceous matter decreases to zero in the eastern Tailuko zone, and the amount of chlorite + white mica diminishes somewhat. Epidote becomes more aluminous at higher metamorphic grade. Eastward, phengites change progressively to more muscovitic compositions as the proportion of biotite increases.A close approach to chemical equilibrium for the pre-Cenozoic, complexly deformed metamorphic basement assemblages is suggested by regular, systematic, major and minor element partitioning between analysed coexisting phases. Fractionation is less pronounced on the E, reflecting higher temperatures. Estimated physical conditions of recrystallization with αH2O and αCO2 moderate, are: T 〉 325 ± 75°C, P 〉 3 kbar (W); T 〉 425 ± 75°C, P 〉 4kbar(E).The gradual eastward increase in metamorphic intensity from the Slate Formation through the Pihou(?) Formation and the three Tailuko zones, as well as the relict precursor textures in the pre-Cenozoic layered basement rocks indicate that the observed paragenetic sequence could represent a synchronous Neogene recrystallization event, probably accompanying the Plio-Pleistocene collision of the Asiatic continental margin and the Luzon (Coastal Range) andesitic arc.

Notes: The structure, microstructure and petrology of a small area close to the village of Bard in Val d'Aosta (Italy) has been studied in detail. The area lies across the contact between the Gneiss Minuti (GM) and the Eclogitic Micaschist (EMS) Complexes of the Lower element of the Sesia portion of the Sesia-Lanzo Zone (Western Alps). Both complexes have undergone high-pressure metamorphism, but the metamorphic assemblages indicate a sudden increase in pressure in going across the contact from the GM to the EMS. Therefore, we interpret the contact as a thrust dividing the lower element of the Sesia into two sub-elements. This interpretation is supported by structural evidence.The early Alpine (90-70 Ma) metamorphic history is best preserved in the EMS and is one of increasing pressure associated with thrusting. The maximum P/T recorded in the EMS is 〉1500 MPa (〉15kbar) and 550°C and in the GM is 〈 1500-1300 MPa (〈 15-13 kbar) and 500-550°C. We suggest that the rocks were probably in an active Benioff zone during this time.From then on the histories of the GM and EMS are the same. Deformation continued and the thrust and thrust slices were folded during decreasing pressure. We interpret the first postthrusting deformation in terms of uplift associated with continued shortening of the crust and underplating after the Benioff zone had become inactive and a new Benioff zone had developed further to the north-west.A still later deformation and the Lepontine metamorphism (38 Ma) are related to continued uplift. Much of this deformation is characterized by structures indicative of vertical shortening and lateral spreading as the mountains rose above the general level of the surface.

Notes: In the Boi Massif of Western Timor the Mutis Complex, which is equivalent to the Lolotoi Complex of East Timor, is composed of two lithostratigraphical components: various basement schists and gneisses; and the dismembered remnants of an ophiolite. Cordierite-bearing pelitic schists and gneisses carry an early mineral assemblage of biotite + garnet + plagioclase + Al-silicate, but contain no prograde muscovite; sillimanite occurs in a textural mode which suggests that it replaced and pseudomorphed kyanite at an early stage and some specimens of pelitic schist contain tiny kyanite relics in plagioclase. Textural relations between, and mineral chemistries of, ferro-magnesian phases in these pelitic chists and gneisses suggest that two discontinuous reactions and additional continuous compositional changes have been overstepped, possibly with concomitant anatexis, as a result of decrease in Pload during high temperature metamorphism. The simplified reactions are: garnet and/or biotite + sillimanite + quartz + cordierite + hercynite + ilmenite + excess components. P-T conditions during the development of the early mineral assemblage in the pelitic gneisses are estimated to have been P + 10 kbar and T 〉 750°C, based upon the plagioclase-garnet-Al-silicate-quartz geobarometer and the garnet-biotite geothermometer. P-T conditions during the subsequent development of cordierite-bearing mineral assemblages in the pelitic gneisses are estimated to have been P + 5 kbar and T + 700°C with XH2O 〈 0.5, based upon the Fe content of cordierite occurring in the assemblage quartz + plagioclase + sillimanite + biotite + garnet + cordierite coexisting with melt.Final equilibration between some of the phases suggests that conditions dropped to P 〉 2.3 kbar and T 〉 600°C. A similar exhumation P-T path is suggested for the pelitic schists with early metamorphic conditions of P 〉 6.2 kbar and T 〉 745°C and subsequent development of cordierite under conditions in the range P = 3-4 kbar and T = 600-700°C. The tectonic implications of these P-T estimates are discussed and it is concluded that the P-T path followed by these rocks was caused by decompression during rifting and synmetamorphic ophiolite emplacement resulting from processes during the initiation and development of a convergent plate junction located in Southeast Asia during late Jurassic to Cretaceous time.

Notes: Plagioclase compositions vary from An0.1–2.5 to An32 with increasing grade in chlorite zone to oligoclase zone quartzofeldspathic schists, Franz Josef-Fox Glacier area, Southern Alps, New Zealand. This change is interrupted by the peristerite composition gap in rocks transitional between greenschist and amphibolite facies grade. Oligoclase (An20-24) and albite (An0.1–0.5) are found in biotite zone schists below the garnet isograd. With increasing grade, the plagioclase compositions outline the peristerite gap, which is asymmetric and narrows to compositions of An12 and An6 near the top of the garnet zone. In any one sample, oligoclase is the stable mineral in mica-rich layers above the garnet isograd, whereas albite and oligoclase exist in apparent textural equilibrium in adjacent quartz-plagioclase layers. The initial appearance of oligoclase in both layers results from the breakdown of epidote and possibly sphene. Carbonate is restricted to the quartz-plagioclase rich layers and probably accounts for the more sodic composition of oligoclase in these layers. The formation of more Ca-rich albite and more Na-rich oligoclase near the upper limit of the garnet zone coincides with the disappearance of carbonate and closure of the peristerite gap. Garnet appears to have only a localized effect on Ca-enrichment of plagioclase in mica-rich layers within the garnet zone. The Na-content of white mica increases sympathetically with increasing Ca-content of oligoclase and metamorphic grade.Comparison of the peristerite gap in the Franz Josef-Fox Glacier schists and schists of the same bulk composition in the Haast River area, 80 km to the S, indicates that oligoclase appears and epidote disappears at lower temperatures, and that the composition gap between coexisting albite and oligoclase is narrower in the Franz Josef-Fox Glacier area. It is suggested that a higher thermal gradient (38-40°C/km) and variations in Si/Al ordering during growth of the plagioclases between the two areas may account for these differences. In the Alpine schists the peristerite gap exists over a temperature and pressure interval of about 370-515°C and 5.5-7 kbar (550-700 MPa) PH2O.

Notes: A complete prograde P–T path, defined by 10 calculated P–T fields in succession, is recognized from metapelites by using geothermobarometry on garnet-bearing assemblages with microstructural control. Overstacking of several tectonic units during an early Variscan continental collision explains the complex prograde P–T history. Isostatic uplift and deformation controlled the retrograde P–T path.Deformation with changing character acted continuously during all stages of the evolution of the Austroalpine basement complex. After the intrusion of Caledonian granitoids, metapelites and magmatic rocks suffered a shearing deformation D1–D2, which produced sheath folds as well as the main foliation S2. Spessartine-rich first-generation garnets, situated in microlithons enclosed by S2, record the onset of shearing under increasing high-pressure–low-temperature conditions (7 kbar/380°C). Geothermobarometry on second-generation garnets which have been rotated during growth indicates isothermal decompression from 9 kbar to 5 kbar/500°C and subsequent recompression/heating during continuing shearing. This is explained by overthrusting of a tectonic unit (unit 2) from NE to SW upon the micaschist unit (unit 1), followed by isostatic uplift and further overstocking of a third unit (unit 3). The resulting Pmax of 12 kbar at 650°C and further increasing temperatures up to 680°C accompanied by decompression have been calculated using a third generation of garnets. These high-pressure–high-temperature conditions may explain the occurrence of eclogitic metabasites in adjacent regions.Staurolite and kyanite first appeared under decreasing pressures at the last stage of prograde P–T evolution. Shortening deformation D3 and simultaneous growth of typical amphibolite facies minerals (staurolite 2, kyanite 2, sillimanite, andalusite) occurred during the retrograde path. A final step of Variscan evolution was marked by an oppositely directed shearing D4 (at T 〉 300°C and P 〉 3 kbar), possibly indicating backthrusting or extension.Apart from acid intrusions, no signs of a previous Caledonian thermotectonic history were found in the area to the south of the Defereggen–Antholz–Vals Line.

Notes: Olivine-plagioclase coronas in metagabbros from the Adirondack Mountains, New York (USA) are spatially well-organized reaction textures consisting most commonly of sequential layers of orthopyroxene, clinopyroxene, plagioclase, and garnet; the textures are characteristic of diffusion-controlled reaction kinetics. Although similar coronas have been interpreted by previous workers in terms of an isochemical steady-state diffusion model, petrographical relations and material-balance calculations establish that coronas in the Adirondack metagabbros cannot be treated as isochemical and do not form in a single-stage steady-state process; instead they evolve through time in a complex open-system reaction.In this study, the isochemical diffusion model is modified to account for elemental fluxes across the outer boundaries of the coronal reaction band, thereby approximating the open-system behaviour of the coronas. The sequence and relative proportions of product minerals calculated by the open-system steady-state model correspond closely to those observed in coronas of the Adirondacks, over a wide range of values for the relative diffusivities of chemical components involved in the reaction, regardless of the particular method used to determine material balance in the reaction texture.Despite this correspondence, petrographical evidence for successive replacement of coronal product layers reveals that the Adirondack coronas evolved through one or more transient states, rather than forming in a single-stage steady-state process. There is no evidence that the successive replacement of coronal product layers resulted from changes in pressure or temperature, but there is petrographical evidence that these changes resulted from modification of the composition of reactant plagioclase as the corona-forming reaction proceeded. This is confirmed by the fact that the evolution of the coronas over time can be replicated with the open-system diffusion model by simulating the effect of the gradual exhaustion of plagioclase as a source of the Ca and Si components required for reaction. These simulations suggest that successive stages in the evolution of the coronas are characterized by these product sequences: (i) orthopyroxene-clinopyroxene-plagioclase-garnet; (ii) orthopyroxene-clinopyroxene-garnet; and (iii) orthopyroxene-garnet. All of these stages, and the transitions between them, are observed petrographically. Coronas in Adirondack metagabbros appear, therefore, to have originated in a complex, open-system, diffusion-controlled reaction in which the product assemblages changed as the reaction progressed.

Notes: Pseudotachylite veins have been found in the mylonite zone of the Hidaka metamorphic belt, Hokkaido, northern Japan. They are associated with faults with WNW-ESE to ENE-WSW or NE-SW trends which make a conjugate set, cutting foliations of the host mylonitic rocks with high obliquity. The mylonitic rocks comprise greenschist facies to prehnite-pumpellyite facies mineral assemblages. The mode of occurrence of the pseudotachylite veins indicates that they were generated on surfaces of the faults and were intruded as injection veins along microfractures in the host rocks during brittle deformation in near-surface environments. An analysis of the deformational and metamorphic history of the Hidaka Main Zone suggests that the ambient rock temperature was 200–300° C immediately before the formation of the Hidaka pseudotachylite.Three textural types of veins are distinguished: cryptocrystalline, microcrystalline and glassy. The cryptocrystalline or glassy type often occupies the marginal zones of the microcrystalline-type veins. The microcrystalline type is largely made up of quench microlites of orthopyroxene, clinopyroxene, biotite, plagioclase and opaque minerals with small amounts of amphibole microlites. The interstices of these microlites are occupied by glassy and/or cryptocrystalline materials. The presence of microlites and glasses in the pseudotachylite veins suggests that the pseudotachylites are the products of rapid cooling of silicate melts at depths of less than 5 km.The bulk chemical composition of the pseudotachylite veins is characterized by low SiO2 and a high water content and is very close to that of the host mylonitic rocks. This indicates that the pseudotachylite was formed by virtual total melting of the host rocks with sufficient hydrous mineral phases. Local chemical variation in the glassy parts of the pseudotachylite veins may be due to either crystallization of quench microlites or the disequilibrium nature of melting of mineral fragments and incomplete mixing of the melts. Pyroxene microlites show a crystallization trend from hypersthene through pigeonite to subcalcic augite with unusually high Al contents. The presence of pigeonite and high-Al pyroxene microlites, of hornblende and biotite microlites and rare plagioclase microlites may indicate the high temperature and high water content of the melt which formed the pseudotachylite veins. The melt temperatures were estimated to be up to 1100° C using a two-pyroxene geothermometer. Using published data relating water solubilities in high-temperature andesitic magmas to pressure, a depth estimate of about 4 km is inferred for the Hidaka pseudotachylites.Evidence derived from pseudotachylites in the Hidaka metamorphic belt supports the conclusion that pseudotachylite is formed by frictional melting along fault surfaces at shallow depths from rocks containing hydrous minerals.

Notes: The higher grade metamorphic zonation of the Sambagawa (= Sanbagawa) belt is established for the first time for the whole area of central Shikoku. As discontinuous reactions to define the isograd are absent, the metamorphic grade is primarily determined by the Mg-Fe partitioning between garnet and chlorite along representative traverses. However, for regional mapping, mineralogical features of the pelitic schists, such as using mineral assemblages of more than divariant equilibrium, the modal garnet to chlorite ratio, and the optical properties of chlorite, are employed as auxiliary criteria.The presence of the highest grade mineral zone in the middle of the structural level is confirmed, but its spatial distribution is far more complex than hitherto accepted. Thermal axes are now confirmed at three different structural levels. A model is presented in which the stacking of thrust sheets of different grade took place while metamorphic reactions were in progress. Thermal readjustment brought a continuous metamorphic temperature gradient across and within the thrust sheets. Tectonic blocks of metagabbro and ultramafic rock were emplaced synchronously with thinning and subsequently also re-equilibrated. Local anomalies of metamorphic grade, represented by mixing of schists of different metamorphic grade, exist, but they are due to a later stage event.

Notes: Low-pressure metamorphic facies (i.e. high T/P ratios) are widespread in a wide range of tectonic settings. Explanations offered for the occurrence of these facies include extensional and/or magmatic models. However, these fail to explain that the low-P facies metamorphism is commonly coeval with a phase of pervasive crustal thickening, with T/P ratios increasing during, or slightly lagging behind, the thickening. We propose an alternative explanation based on the approximate synchroneity of crustal thickening and erosion (thinning) of the mantle lithosphere.

Notes: In the Proterozoic Mary Kathleen Fold Belt, northern Australia, infiltration of large volumes of externally derived fluid occurred synchronously with regional amphibolite-facies metamorphism and deformation. This paper develops a model of structurally controlled fluid migration by comparing the distribution of fossil fluid pathways with the inferred stress and strain patterns during the deformation. Intense fluid flow was localized within strong, relatively brittle meta-intrusive bodies, and in discrete, veined, brecciated and altered zones around their margins. In metasediments folded in a ductile manner outside these areas, fluid infiltration was negligible. The direct correlation between structural styles and the magnitude of veining and metasomatism suggests control of permeability enhancement, and hence fluid flow, by deformation. Finite difference modelling of a strong body in a weaker matrix has been used to evaluate the variation of stresses during the deformation, from which it is clear that stress and strain heterogeneities have systematically influenced the development and maintenance of metamorphic fluid pathways. Particular regions in which mean stress may be significantly lower than the average lithostatic pressures include the ‘strain shadow’zones adjacent to the strong bodies, other dilatant zones around the bodies, and the bodies themselves. This geometry is favourable not only for localized brittle deformation under amphilobite facies conditions, but also for focused fluid flow in the low mean stress regions, as evidenced by the abundance of veins. Fluid access through these metamorphic aquifers occurred during tensile failure episodes, with particularly large dilations and decimetre-scale veining in areas of strain incompatibility. It appears likely that fluid circulated many times through the Fold Belt, with flow concentrated in the metamorphic aquifers. A model is developed that explains both the structurally focused fluid flow and the postulated multi-pass recirculation by dilatancy pumping, the ‘pump engines’comprising the low mean stress zones.

Notes: An Early Palaeozoic (Ordovician ?) metamudstone sequence near Wojcieszow, Kaczawa Mts, Western Sudetes, Poland, contains numerous metabasite sills, up to 50 m thick. These subvolcanic rocks are of within-plate alkali basalt type. Primary igneous phases in the metabasites, clinopyroxene (salite) and kaersutite, are veined and partly replaced by complex metamorphic mineral assemblages. Particularly, the kaersutite is corroded and rimmed by zoned sodic, sodic–calcic and calcic amphiboles. The matrix is composed of actinolite, pycnochlorite, albite (An ≤ 0.5%), epidote (Ps 27–33), titanite, calcite, opaques and, occasionally, biotite, phengite and stilpnomelane.The sodic amphiboles are glaucophane to crossite in composition with NaB from 1.9 to 1.6. They are rimmed successively by sodic–calcic and calcic amphiboles with compositions ranging from magnesioferri-winchite to actinolite. No compositions between NaB= 0.92 and NaB= 1.56 have been ascertained.The textures may be interpreted as representing a greenschist facies overprint on an earlier blueschist (or blueschist–greenschist transitional) assemblage. The presence of glaucophane and no traces of a jadeitic pyroxene + quartz association indicate pressures between 6 and 12 kbar during the high-pressure episode. Temperature is difficult to assess in this metamorphic event. The replacement of glaucophane by actinolite + chlorite + albite, with associated epidote, allows restriction of the upper pressure limit of the greenschist recrystallization to 〈8 kbar, between 350 and 450°C. The mineral assemblage representing the greenschist episode suggests the P–T conditions of the high-pressure part of the chlorite or lower biotite zone. The latest metamorphic recrystallization, under the greenschist facies, may have taken place in the Viséan.

Notes: Using the experimental data on Fe–Mg exchange between orthopyroxene and biotite of Fonarev & Konilov (1986), an orthopyroxene–biotite geothermometer is developed. The thermometer is corrected for mixing of Ti and Al in octahedral sites in biotite and also for non-ideal mixing of Fe and Mg in orthopyroxene. The thermometer is applied to several amphibolite–granulite transition facies and granulite facies rocks and also to mantle xenoliths. It yields consistent results in rocks of widely varying bulk composition, and highly magnesian mantle xenoliths. This thermometer removes the difficulty of estimating temperature in garnet-free rocks in high-grade terrains and also provides independent estimates of temperature in garnet-bearing assemblages.

Notes: The Omeo Metamorphic Complex forms the southern end of the Wagga Metamorphic Belt, which is the main locus of Palaeozoic low-pressure metamorphism in the Lachlan Fold Belt, south-eastern Australia. It comprises metamorphosed Ordovician quartz-rich turbidites originally derived from Precambrian cratonic rocks. Prograde regional metamorphism occurred in the early Silurian, very soon after sedimentation had ceased. The sequence of metamorphic zones, with increasing grade, is: chlorite, biotite, cordierite, andalusite–K-feldspar and sillimanite–K-feldspar. Migmatites occur in the sillimanite–K-feldspar zone, but large bodies of S-type granite were derived from rocks underlying the exposed Ordovician sequence. P and T estimates for the highest grade rocks are T= 700°C and P= 3.5 kbar, indicating a very high P–T gradient of 65°C/km.The high heat flow during prograde metamorphism probably resulted from a combination of a thermal anomaly persisting from a pre-metamorphic back-arc basin environment, and intrusion of hot, mantle-derived magmas into the lower and middle crust.Regional retrograde metamorphism coincided with a general reheating of the crust in the Siluro-Devonian, accompanied by intrusion of many I-type plutons and resetting of the K–Ar dates of some earlier plutons. The Omeo Metamorphic Complex was exposed to erosion at this time.

Notes: The Narryer Gneiss Complex of the Yilgarn Block is a key segment of the Western Australian Precambrian Shield. It is a regional granulite facies terrain comprised of predominantly quartzo-feldspathic gneisses derived from granitic intrusions c. 3.6–3.4 Ga old. Granulite facies metamorphism occurred c. 3.3 Ga ago, and conditions of 750–850°C and 7–10 kbar are estimated for the Mukalo Creek Area (MCA) near Errabiddy in the north. The P–T path of the MCA has been derived from metamorphic assemblages in younger rocks that intruded the gneisses during at least three subsequent events, and this path is supported by reaction coronas in the older gneisses. There is no evidence for uplift immediately following peak metamorphism of the MCA, and a period of isobaric cooling is inferred from the pressures recorded in younger rocks. Pressures and temperatures estimated from metadolerites, which intruded the older gneisses during ‘granite–greenstone’tectonism at about 2.6 Ga and during early Proterozoic thrusting show that the Errabiddy area remained in the lower crust, although it was probably reheated during the younger events. Isothermal uplift to upper crustal levels occurred at c. 1.6 Ga ago, and was followed by further deformation and patchy retrogression of high-grade assemblages. The effects of younger deformation, cooling and reheating can be discerned in the older gneisses, but as there has been no pervasive deformation or rehydration, the minerals and microstructures formed during early Archaean granulite facies metamorphism for the most part are retained.The MCA remained in the lower crust for about 1700 Ma following peak metamorphism and some event unrelated to the original metamorphism was required to exhume it. Uplift occurred during development of the Capricorn Orogen, when some 30–35 km were added to the crust beneath the Errabiddy area. The recognition of early Proterozoic thrusting, plus crustal thickening, suggests that the Capricorn Orogen is a belt of regional compression which resulted from convergence of the Yilgarn and Pilbara Cratons.

Notes: We present, as a progress report, a revised and much enlarged version of the thermodynamic dataset given earlier (Holland & Powell, 1985). This new set includes data for 123 mineral and fluid end-members made consistent with over 200 P–T–XCO2–fO2 phase equilibrium experiments. Several improvements and advances have been made, in addition to the increased coverage of mineral phases: the data are now presented in three groups ranked according to reliability; a large number of iron-bearing phases has been included through experimental and, in some cases, natural Fe:Mg partitioning data; H2O and CO2 contents of cordierites are accounted for with the solution model of Kurepin (1985); simple Landau theory is used to model lambda anomalies in heat capacity and the Al/Si order–disorder behaviour in some silicates, and Tschermak-substituted end-members have been derived for iron and magnesium end-members of chlorite, talc, muscovite, biotite, pyroxene and amphibole.For the subset of data which overlap those of Berman (1988), it is encouraging to find both (1) very substantial agreement between the two sets of thermodynamic data and (2) that the two sets reproduce the phase equilibrium experimental brackets to a very similar degree of accuracy. The main differences in the two datasets involve size (123 as compared to 67 end-members), the methods used in data reduction (least squares as compared to linear programming), and the provision for estimation of uncertainties with this dataset. For calculations on mineral assemblages in rocks, we aim to maximize the information available from the dataset, by combining the equilibria from all the reactions which can be written between the end-members in the minerals. For phase diagram calculations, we calculate the compositions of complex solid solutions (together with P and T) involved in invariant, univariant and divariant assemblages. Moreover we strongly believe in attempting to assess the probable uncertainties in calculated equilibria and hence provide a framework for performing simple error propagation in all calculations in thermocalc, the computer program we offer for an effective use of the dataset and the calculation methods we advocate.

Notes: In a granulite-facies spinel-bearing quartzite, corundum, orthopyroxene and sapphirine (and rarely cordierite and sillimanite) form partial rims separating spinel from quartz. Textures indicate the reactions:spinel + quartz = orthopyroxene + corundum, andspinel + quartz = orthopyroxene + sapphirine.Thus, corundum and sapphirine are produced by reactions involving quartz. The low Al-content of the orthopyroxene (0.5–2.8 wt %) and low values for Mg–Fe distribution coefficient for spinel–sapphirine and spinel–orthopyroxene reflect low-temperature conditions during formation of the reaction products. Absence of zoning in spinel and a constant Mg–Fe distribution coefficient for spinel–sapphirine and spinel–orthopyroxene, over a compositional range, indicate Mg–Fe equilibration. It is suggested that stable reactions such as spinel + quartz = cordierite or spinel + quartz = garnet + sillimanite were over-stepped and that metastable reactions give rise to the anomalous juxtaposition of corundum + quartz.

Notes: The paragenetic relationships between sillimanite, andalusite, kyanite, chlorite, cordierite, biotite, garnet and staurolite in the Early Proterozoic Puolankajärvi Formation (PjF), together with mineral compositions, are used to construct a partial petrogenetic grid for metapelites with significant Mn content (MnO = 0.1–0.5%) by adding a six-phase invariant point over the garnet-absent invariant point for Mn-free AMF-phases.The grid and textural relations of the PjF are used to construct part of the P–T–deformation path for the PjF. Relatively short deformation pulses and associated flow of oxidizing fluid along shear zones were responsible for the paragenetic and compositional changes during cooling and decompression at 600–500°C and 6.0–2.5 kbar. Oxidation led to decreased Fe2+ and further stressed the importance of Mn (increased Mn/divalent cations).A tectonothermal evolution of the Kainuu Schist Belt is presented which includes crustal thinning and steepening of a previously established thermal gradient. This was followed by thrusting and folding of the isotherms into a thermal antiform on the western side of the belt.

Notes: The alkalic Scituate Granite was emplaced into crystalline sequences within the New England Esmond–Dedham terrane in the Late Devonian (c. 370 Ma). Variably recrystallized amphibole (iron-rich, hastingsite–hastingsitic hornblende) from four variably deformed samples of the pluton record south-westerly younging 40Ar/39Ar plateau ages ranging between 276 and 263 Ma. These are interpreted to date diachronous cooling through temperatures appropriate for intracrystalline retention of argon following late Palaeozoic orogenic activity. Iron-rich biotite concentrates from the samples record only slightly younger ages, and therefore suggest relatively rapid post-metamorphic cooling. The 40Ar/39Ar ages indicate that the late Palaeozoic tectonothermal overprint was much more regionally pervasive than was previously considered. The apparent timing of this activity is similar to previous estimates for the chronology of high-grade metamorphism throughout the adjacent Hope Valley terrane and for phases of ductile movement on the intervening Lake Char–Honey Hill fault system.

Notes: Aluminous reaction textures in orthoamphibole-bearing rocks from the Froland area, Bamble, south Norway, record the prograde pressure–temperature path of the high-grade Kongsbergian Orogeny (c. 1600–1500 Ma) and the low–mid amphibolite facies overprint during the Sveconorwegian Orogeny (c. 1100–1000 Ma). The rocks contain anthophyllite/gedrite, garnet, cordierite, biotite, quartz, andalusite, kyanite, Cr-rich staurolite, tourmaline, ilmenite, rutile and corundum in a variety of parageneses. The P–T path is deduced from petrographic observations, mineral chemistry and zoning, geothermometry and (N)FMASH equilibria. The results indicate the sequence of metamorphic stages outlined below. (a) An M1 phase characterized by the presence of strongly deformed andalusite, gedrite and tourmaline.(b) An M2 phase with the development of kyanite after andalusite and the growth of staurolite associated with strong Na–Al–Mg zoning in orthoamphibole, indicating an increase in pressure (4 8 kbar) and temperature (500° 650°C).(c) Pressure decrease at high P (6–7 kbar) and high T (600–700 °C) during M3a with the production of cordierite ° Corundum between kyanite, staurolite and orthoamphibole and cordierite growth between corundum and orthoamphibole.(d) Temperature increase to 740 ± 60 °C and 7 kbar; static growth of garnet (M3b) at the metamorphic climax (peak T). The heat supply necessary to explain the temperature increase between the M3a and M3b phases is correlated with synkinematic enderbitic–charnockitic and basic intrusions in the Arendal granulite facies terrain.(e) M3b metamorphic conditions were followed by an initial isobaric cooling path (early M4) and late-stage pressure decrease (late M4). Early M4 conditions of 6–7 kbar and 550–600 °C, assuming PH2O 〈 Ptotal are indicated by a retrograde talc–kyanite–quartz assemblage in late quartz–cordierite veins. Late M4 conditions of 3–4 kbar and 420–530 °C are inferred from a kyanite–andalusite–chlorite–quartz assemblage in vein-cordierite. The M1–M3 stages are interpreted as being the result of the same metamorphic P–T path, which was caused by both tectonic and magmatic thickening. A prolonged crustal residence time is proposed for the Bamble sector before uplift during the later stages of M4 occurred.

Notes: Instrumental settings for determination of illite/muscovite ‘crystallinity’(half-height width of the 10-Å X-ray diffraction peak) and the limits of the anchimetamorphic zone adopted by various authors fall into several groups.The variation in the limiting peak widths between the authors that have adopted Kubler's Neuchâtel boundary values of 0.42° and 0.25°Δ2θ can be interpreted in terms of variation in the instrumental settings. The choice of time constants higher than those given by the formula causes peak broadening; this effect is particularly marked at high scan rates. The peak broadening is by constant increments that are virtually independent of the absolute peak width.The differences between the Kubler (Neuchâtel)-derived limiting values and some other scales are appreciably greater than can be accounted for by these differences in instrumental settings: many of these scales are not equivalent. In particular, the limits adopted by Dunoyer de Segonzac (1969) and subsequent workers at Strasbourg are too broad; their anchizone represents a range of grades of metamorphism lower than that of Kubler, widely overlapping the latter's ‘diagenetic’zone. Those adopted by some other, mainly French, authors are too narrow.The limits of the anchizone should be calibrated by inter-laboratory standards, and the instrumental settings should be specified in full.

Notes: A combination of fluid inclusion, stable isotope and geochemical techniques has been used to study the nature of fluids present and their behaviour during Caledonian low-grade metamorphism of the Harlech Dome, north Wales. Fluid inclusion studies show that in most of the metasedimentary sequence the peak metamorphic fluid was an aqueous Na–K–Cl brine but in the graphitic Clogau Formation and in parts of the overlying Maentwrog Formation immiscible H2O-rich and CH4-rich fluids coexisted.Late-stage inclusions are of calcium-rich brine and a dilute aqueous fluid. The chemical composition of chlorite in metamorphic veins and rocks varies between different formations and quartz-oxygen isotopic compositions show considerable variation between different units. Both of these features are taken to indicate that there was little or no pervasive movement of fluid between different units at the peak of metamorphism. After the metamorphic peak there was focused flow of fluid upward through the sequence along fractures, in response to end-Caledonian uplift and unloading. Where the migrating fluid crossed the graphitic shales, interaction between the fluid and the shales gave rise to the formation of the auriferous veins of the Dolgellau Gold Belt. Subsequent to this mineralizing event there was widespread development of 18O-enriched calcites and micas.In the case of vein minerals it is possible that these crystallized directly from late-stage fluids at lower temperature than the quartz in the same veins. Alternatively, the original vein minerals may have re-equilibrated with later 18O-enriched or cooler fluid. In the case of muscovites in the rock matrix it is proposed that the isotopically heavy compositions are the result of re-equilibration of initially light grains with an introduced fluid, requiring considerable influx of fluid. This event may relate to either of two late-stage fluids observed as inclusions.

Notes: Sapphirine occurs in a 3-5 m wide zone between amphibole-lherzolite and garnetiferous metagabbro at Finero in the Ivrea Zone, NW Italian Alps. Layers consisting of plag + hb + sa + cpx + opx + sp + gt are interbanded with spinel pyroxenites, which may contain sapphirine replacing spinel. All minerals are very magnesian, with XMg between 0.78 and 0.92. Bulk rock analyses suggest that precursors to the sapphirine-bearing rocks were igneous cumulates of plagioclase + olivine + hornblende + spinel. Up to 16wt% CaO does not inhibit sapphirine formation and it is the unusually Mg-rich nature of the host rocks which allows sapphirine development. The early igneous assemblage was replaced by one of cpx + sa + hb +± plag at a pressure of 9 ± 1 kbar and temperatures of 900 ± 50°C. Subsequent rapid uplift caused the instability of gt, gt + hb, hb and sa + cpx to form opx + plag ± sp ± sa symplectites.

Notes: The Gran Paradiso basement complex of the French and Italian Alps is composed of metasediments, termed the gneiss minuti, and metabasic rocks, both of which are intruded by a late Hercynian granite. The Bonneval gneiss, which crops out at the western edge of the complex, is composed of highly deformed metasediments, volcanics and volcaniclastic rocks. Eclogites, now highly altered, occur in the metabasic rocks. Kyanite and blue-green amphibole are locally present in the gneiss minuti and aegirine plus riebeckite occur in the Bonneval gneiss. A moderately high pressure - low temperature metamorphic event of probable Alpine age occurred in the basement complex. This metamorphic event differs from that in the overlying Sesia unit and ophiolites of the Schistes lustrés nappe in being at lower pressures (below the ab = jd100+ qz transition) and post-dating the major (D2A) deformation. The origin of the metamorphism is discussed and interpreted as a probable consequence of the overlying nappe pile which was emplaced during the D2A event. Subsequent greenschist facies metamorphism in the basement complex is a consequence of thermal relaxation during uplift.

Notes: Abstract. A method for the quantitative analysis of the spatial relations of minerals is described. Dispersed distributions are formed by annealing and destroyed in post-tectonic migmatization. Aggregate distributions characterize solid-state differentiation, whereas leucosomes formed in systems of high fluid:rock ratio (in the examples studied, anatectic melts) show random distributions.Quantitative textural analysis can be used to indicate whether migmatization was post-tectonic or earlier, though caution is necessary if post-migmatite cooling is slow or if there is some minor deformation. More importantly, it can be used to discriminate melt-present from melt-absent leucosomes; this is exemplified by a suite of metamorphic and anatectic migmatites from the Scottish Caledonides.The textural evolution of anatexites with increasing melt percentage is traced. Initial feldspar porphyroblastesis occurs by Ostwald ripening via grain boundary melts; subsequently ophthalmites develop with fabrics and chemistry inherited from the palaeosome. At greater than 30% melt these inherited fabrics are wholly destroyed. Deformation prompts segregation into melanosome and leucosome; resultant leucosomes contain no inherited crystals. The scale of anatectic systems is fixed at the point at which segregation begins; ophthalmites provide evidence for melt and crystal transfer beyond original palaeosome boundaries. In contrast, metamorphic migmatites are necessarily small-scale systems because of diffusive constraints, and melanosomes are invariably produced.

Notes: The oligoclase-biotite zone of the Bessi area, central Shikoku is characterized by sodic plagioclase (XCa= 0.10–0.28)-bearing assemblages in pelitic schists, and represents the highest-grade zone of the Sanbagawa metamorphic terrain. Mineral assemblages in pelitic schists of this zone, all with quartz, sodic plagioclase, muscovite and clinozoisite (or zoisite), are garnet + biotite + chlorite + paragonite, garnet + biotite + hornblende + chlorite, and partial assemblages of these two types. Correlations between mineral compositions, mineral assemblages and mineral stability data assuming PH2O = Psolid suggests that metamorphic conditions of this zone are about 610 ± 25°C and 10 ± 1 kbar.Based upon a comparative study of mineralogy and chemistry of pelitic schists in the oligoclase-biotite zone of the Sanbagawa terrain with those in the New Caledonia omphacite zone as an example of a typical high-pressure type of metamorphic belt and with those in a generalized‘upper staurolite zone’as an example of a medium-pressure type of metamorphic belt, progressive assemblages within these three zones can be related by reactions such as:

Notes: An assemblage consisting of corundum, sapphirine, spinel, cordierite, garnet, biotite and bronzite is described from the Messina area of the Limpopo Mobile Belt, and consideration given to its petrogenesis. Various geothermometers and geobarometers have been applied in an attempt to determine the temperatures and pressures of metamorphism.A former coexistence of garnet and corundum is suggested to have developed during the earliest high pressure phase of the metamorphism, where temperatures exceeded 800°C and pressures as high as 10kbar may have been experienced. Subsequently, continuous retrograding reactions from medium pressure granulite facies at about 800°C and 8kbar towards amphibolite facies generated spinel, cordierite, sapphirine and possibly also bronzite. The most notable reaction was probably of the form: garnet + corundum = cordierite + sapphirine + spinel.

Notes: A review of currently available information relevant to the Basal Gneiss Complex (BGC) of Western South Norway, combined with the authors’own observations, leads to the following conclusions.1. Most of the BGC consists of Proterozoic crystalline rocks and probably subordinate Lower Palaeozoic cover.2. The last major deformation of these rocks was during the Caledonian orogeny and involved large-scale thrusting, recumbent folding and doming. The structural development of the BGC is closely tied in with that of the Caledonian allochthon.3. The whole eclogite-bearing part of the BGC has suffered a high pressure metamorphism with conditions of between 550°C, 12.5 kbar (Sunnfjord) and about 750°C, 20 kbar (Møre og Romsdal) at the metamorphic climax.4. This metamorphism was of Caledonian age, probably rather early in the Caledonian tectonic history of the BGC and is considered to have been a rather transient event.By setting these conclusions in a framework provided by geophysical evidence for the deep structure of the crust in southern Norway we have constructed a geotectonic model to explain the recorded metamorphic history of the BGC. It is suggested that considerable crustal thickening was caused by imbrication of the Baltic plate margin during continental collision with the Greenland plate. This resulted in high pressure metamorphism in the resulting nappe stack. Progradation of the suture caused underthrusting of the Baltic foreland below the eclogite-bearing terrain causing it to emerge at the Earth's surface, aided by tectonic stripping and erosion.Application of isostacy equations to the model shows that eclogites can be formed by in-situ metamorphism in crustal rocks and reappear at the land surface above a normal thickness of crust in a single orogenic episode of approximately 65-70 Ma duration.

Notes: Detailed geochronological, structural and petrological studies reveal that the geological evolution of the Field Islands area, East Antarctica, was substantially similar to that of the adjacent Archaean Napier Complex, though with notable differences in late and post Archaean times. These differences reflect the area's proximity to the Proterozoic Rayner Complex and consequent vulnerability to tectonic process involved in the formation of the latter. Distinctive structural features of the Field Islands are (1) consistent development of a discordant, pervasive S3 axial-plane foliation; (2) re-orientation of S3 axial planes to approximate to the subsequent E-W tectonic trend of the nearby Rayner Complex; (3) selective retrogression by a post-D3 static thermal overprint; and (4) relatively common development of retrogressive, E-W-trending, mylonitic shear zones.Peak metamorphic conditions in excess of 800°C at 900 ± 100 M Pa (9 kbar) were attained at one locality following, but probably close to the time of D2 folding. D3 took place in late Archaean times when metamorphic temperatures were about 650°C and pressures were about 600 MPa (6 kbar). Later, temperatures of 600 ± 50°C and pressures of 700 MPa (7kbar) were attained in an amphibolite-facies event, presumably associated with the widespread granulite to amphibolite-facies metamorphism and intense deformation involved in the formation of the Rayner Complex at about 1100 Ma. The area was subsequently subjected to near-isothermal uplift.Rb-Sr isotopic data indicate that the pervasive D3 fabric developed at about 2400–2500 Ma, and this age can be further refined to 2456+8-5 Ma by concordant zircon analyses from a syn-D3 pegmatite. All zircons were affected by only minor (〈7–10%) Pb loss and/or new zircon growth during the Rayner event at about 1100Ma. Thus the 450–850 μg/gU concentrations of these zircons were too low to cause sufficient lattice damage over the 1350 Ma (from 2450 Ma) for excessive Pb to be lost during the 1100 Ma event. The emplacement of pegmatite at 522 ± 10 Ma substantially changed the Rb-Sr systematics of the only analysed rock that developed a penetrative fabric during the 1100 Ma event. Monazite in this pegmatite contains an inherited Pb component, which probably resides in small opaque inclusions.A good correlation is found between Rb-Sr total-rock ages and rock fabric. U-Pb zircon intercepts with concordia also mostly correspond to known events. However, in one example a near perfect alignment of zircon analyses, probably developed by mixing of unrelated components, produced concordia intercepts that appear to have no direct geochronological significance.

Notes: Around Fiskefjord, southern West Greenland, Archaean amphibolite-facies, granulite-facies and retrograde orthogneisses occur in lithological and structural continuity with each other. The granulite-facies rocks here—and elsewhere in West Greenland—are surrounded by extensive areas of retrograde gneisses. Both the prograde and retrograde metamorphism took place in a major event of continental crust formation c. 3000 Ma ago, which gave rise to granulite-facies conditions in part of the rock complex exposed today. In the Fiskefjord area distributions of major and trace elements, as well as strontium and lead isotopes, show that the fades transformations were accompanied by pronounced metasomatism, and mineral chemistry indicates that the hydrous retrograde metamorphism took place under amphibolite-facies conditions and was gradual and incomplete. The metamorphic and metasomatic processes in the Fiskefjord area are believed to have been controlled by heat from continuous intracrustal injection of large masses of tonalitic magma, which caused gradual dehydration and partial melting, followed by liberation of aqueous fluids during crystallization of anatectic melts. These fluids partially retrograded previously dehydrated gneisses. In contrast, South Indian high-grade gneisses have mainly prograde amphibolite–granulite-facies transitions which are distinct and well preserved, later than penetrative deformation, and are likely to have been controlled by CO2 streaming. These amphibolite–granulite-facies transitions are reported to be near-isochemical. It is suggested that there are (at least) two different kinds of granulite-facies metamorphism: a near-isochemical prograde type in stabilized tectonic environments, perhaps controlled by influx of CO2 (e.g. in South India) and significantly post-dating original crust formation; and a fluid-deficient type with widespread anatexis, hydrous retrogression and metasomatism, which takes place during accretion of continental crust, and in which heat is the governing factor (e.g. in southern West Greenland).

Notes: Garnet lherzolite from the Lyonnais area (eastern French Massif Central) occurs as several lenses elongated within the regional foliation of garnet-biotite-sillimanite gneisses. Within the peridotites a mylonitic foliation can be observed which clearly is oblique to the regional foliation of the surrounding gneisses. Petrological and thermobarometric studies emphasize a tectonometamorphic re-equilibration for both crustal and mantle rocks characterized by a prograde metamorphic stage followed by retrograde evolution. During the burial stage, interpreted as lithospheric subduction, the peridotites underwent their mylonitic deformation, under high-pressure conditions (23–30 kbar). In contrast, the paragneisses have suffered their deformation during the retromorphic evolution under mesozonal conditions (6–8 kbar, 700°C). Our thermobarometric investigations allow us to interpret the granulitic/ultramafic association from the Monts du Lyonnais area as a lithospheric section buried into a Palaeozoic subduction zone, laminated during continental collision and uplifted by erosion processes.

Notes: Manganese-rich and manganese-poor iron formations which occur as thin layers in the Halaguru-Satnuru area, south of Kabbaldurga, Karnataka, India are chemically intermediate between the ‘Algoma’and ‘Lake Superior’types, but higher in their MnO and TiO2 contents. The rocks are of four petrographic varieties: (a) quartz-magnetite-orthopyroxene-clinopyroxene, (b) quartz-magnetite-orthopyroxene-clinopyroxene-garnet, (c) quartz-magnetite-clinopyroxene-garnet, and (d) quartz-magnetite-clinopyroxene-garnet-plagioclase.In the orthopyroxene-clinopyroxene pairs, Mn-Mg and Mn-Fe exchange is ideal irrespective of the MnSiO3 contents of orthopyroxenes (0.6–1.8 mol. % in Mn-poor and 15–25 mol. % in Mn-rich compositions). Mg-Fe exchange in the same pair is however non-ideal. Mn-Fe exchange in orthopyroxene-garnet pairs is ideal. The distribution patterns in the other binaries are inconclusive regarding ideality of exchange. Orthopyroxene-garnet and clinopyroxene-garnet geothermometers, modified for high spessartine contents, give temperatures of 800 ± 30° C. A modified version of the Harley (1984) geothermometer registers 740 ± 60° C, in agreement with the consensus temperature value.The equilibrium log ffo2 values in the iron formations, as calculated from the reaction 6FeSiO3+ O2= 2Fe3O4+ 6SiO2 are in the range of −14.2 to −15.5. Algebraic analysis of variations of fo2 with composition of phases indicates buffering of O2 in the rocks. The absence of grunerite in these assemblages is compatible with XH2O being less than 0.3 in the ambient fluid. Computations from volatile equilibria in the C-O-H system, however, predict high XH2O values (〉0.7) at ac= 1.0, implying that the activity of graphite must have been greatly reduced—this is in accordance with the absence of graphite in these rocks.

Notes: This paper describes the deformation and metamorphism recorded in the Zoovoorby staurolite schist, a sliver of pelitic supracrustal material in the 1.3–1.0 Ga eastern Namaqua Province, South Africa. The supracrustal Biesjepoort Group, of which the schist is a part, has undergone at least four phases of deformation (D1–D4). D1 and D2 are preserved in the pelitic schists; staurolite and garnet grew during D1, with staurolite growth persisting to the very earliest D2 crenulation. Andalusite, found in more Mg-rich schists, grew during D2, overprinting both S1 schistosity and S0 banding. S2 has been rotated both with respect to S1 (preserved as parallel orientated inclusion trails in garnet and staurolite) and with respect to its original orientation (preserved as open D2 crenulations in staurolite). Staurolite is dissolved against S2 in zones of progressive shear. The pseudomorphing of staurolite and andalusite by cordierite, and the preservation of relic grains of both minerals in a wide range of garnet–cordierite pelites throughout the eastern Namaqua Province infers that what is preserved fortuitously in the Zoovoorby locality is representative of the early metamorphic history of a much larger terrane. The high thermal gradients needed to attain estimated conditions of 540–550° C and 1.6–2.4 kbar require substantial heat input. Large amounts of foliated (syn-D2) granite amongst the supracrustal succession are inferred to be the result of delamination of a thickened crust at a destructive plate margin, generating an elevated thermal gradient during D1–D2 times.

Notes: Poikiloblastic index minerals in pelitic rocks from the Orrs Island–Harpswell Neck area of coastal Maine contain inclusion textures that indicate sequential growth of progressively higher grade metamorphic minerals during development of a near-vertical crenulation foliation. The sequence of zones in the field is garnet, staurolite, staurolite–andalusite, staurolite–sillimanite and sillimanite. Inclusion fabrics characteristic of different stages in crenulation cleavage development indicate that index minerals nucleated and grew sequentially: biotite began to grow before deformation, garnet began to grow during early stages of crenulation cleavage development, staurolite grew during intermediate stages, and andalusite grew relatively late, when transposition of the foliation was nearly complete. Muscovite pseudomorphs and sillimanite were mainly post-kinematic. The fact that metamorphic index minerals grew sequentially in individual rocks in the same order in which they appear across the field area indicates that the high temperature part of the pressure–temperature path was similar to the metamorphic field gradient.Metamorphism in the Orrs Island–Harpswell Neck area is consistent with the magmatic heating model that has been proposed for western Maine. Sequential development of index minerals in pelitic rocks in the Orrs Island–Harpswell Neck area apparently resulted from sequential nucleation after substantial overstepping of mineral-forming reactions. Once nucleation of an index mineral had taken place, initial growth was rapid and poikiloblasts preserved inclusion trails characteristic of the prevailing stage of crenulation cleavage development. Because nucleation of sillimanite may have required more overstepping of the andalusite–sillimanite reaction than nucleation at dehydration reactions, determination of metamorphic conditions for rapidly heated rocks such as these by comparison with a petrogenetic grid is problematic. Garnet zoning patterns in these rocks should reflect the fact that growth of garnet interiors occurred early during metamorphism in equilibrium with a low-grade assemblage. Only garnet rims would be expected to record the subsequent pressure–temperature path.

Notes: The Nordlandet peninsula (Akia terrane) and the Tasiusarsuaq terrane in southern West Greenland were metamorphosed to granulite facies at 3.0 and 2.8 Ga respectively. Temperatures of metamorphism are estimated using magnetite + ilmenite, garnet + orthopyroxene, garnet + clinopyroxene and garnet + biotite thermometers. Barometry has been carried out in the two terranes using eight different garnet barometers. A uniform set of activity models for all minerals, including the garnet activity model of Newton et al. (1986), is applied to each barometer in order to permit comparison. Pressure estimates using the different barometers are generally quite consistent (±1.5 kbar). Use of the Newton et al. (1986) garnet activity data results in pressures similar to those obtained using other garnet activity models.Peak metamorphic conditions on the Nordlandet peninsula are estimated to have been 800 ± 50°C, 7.9 ± 1.0 kbar. Values of logfO2 are estimated to have been 1.1 to 2.0 above the quartz + magnetite + fayalite buffer from assemblages of magnetite + ilmenite and quartz + magnetite + ferrosilite. Peak metamorphic conditions in the Tasiusarsuaq terrane are estimated to have been 780 ± 50°C, 8.9 ± 1.0 kbar. Estimates of fH2O and fCO2 using biotite, amphibile, grossular + anorthite and grossular + scapolite equilibria are low in both terranes. These results suggest that granulite metamorphism was fluid absent in both terranes, and that the metamorphism in the Akia terrane and possibly also in the Tasiusarsuaq terrane was initiated by the injection of large volumes of magma into the lower crust.

Notes: Garnet-biotite gneisses, some of which contain sillimanite or hornblende, are widespread within the Otter Lake terrain, a portion of the Grenville Province of the Canadian Shield. The metamorphic grade is upper amphibolite to, locally, lower granulite facies.The atomic ratio Fe2+/(Fe2++ Fe3+) in biotite ranges from 0.79 to 0.89 (ferrous iron determinations in 10 highly pure separates), with a mean of 0.86. Mg and Fe2+ atoms occupy 67–78% of the octahedral sites, the remainder are occupied by Fe3+, Ti, and Al, and some are vacant. Mg/(Mg + Fe2+), denoted X, in the analysed samples ranges from 0.32 to 0.65. Garnet contains 1–24% grossular, 1–12% spessartine and X ranges from 0.07 to 0.34.Compositional variation in biotite and garnet is examined in relation to three mineral equilibria:(I) biotite + sillimanite + quartz = garnet + K-feldspar + H2O;(II) pyrope + annite = almandine + phlogopite;(III) anorthite = grossular + sillimanite + quartz.Measurements of X (biotite) and X (garnet) are used to construct an illustrative model for equilibrium (I) which relates the observed variation in X to a temperature range of 70°C or a range in H2O activity of 0.6; the latter interpretation is preferred.In sillimanite-free gneisses, the distribution of Mg and Fe2+ between garnet (low in Ca and Mn) and biotite is adequately described by a distribution coefficient (KD) of 4.1 (equilibrium II). The observed increase in the distribution coefficient with increasing Ca in garnet is ln KD= 1.3 + 2.5 × 10−2 [Ca]where [Ca] = 100 Ca/(Mg + Fe2++ Mn + Ca). The distribution coefficient is apparently unaffected by the presence of up to 12% spessartine in garnet.In several specimens of garnet-sillimanite-plagioclase gneiss, the Ca contents of garnet and of plagioclase increase in unison, as required by equilibrium (III). The mean pressure calculated from these data (n= 17) is 5.9 kbar, and the 95% confidence limits are ±0.5 kbar.

Notes: Pumpellyite from four-phase assemblages (pumpellyite + epidote + prehnite + chlorite; pumpellyite + epidote + actinolite + chlorite; pumpellyite + epidote + Na-amphibole + chlorite, together with common excess phases), considered to be low variance in a CaO-(MgO + FeO)-Al2O3-Fe2O3 (+Na2O + SiO2+ H2O) system, have been examined in areas which underwent metamorphism in the prehnite-pumpellyite, pumpellyite-actinolite and low-temperature blueschist facies respectively. The analysed mineral assemblages are compared for nearly constant (basaltic) chemical composition at varying metamorphic grade and for varying chemical composition (basic, intermediate, acidic) at constant metamorphic conditions (low-temperature blueschist facies).In the studied mineral assemblages, coexisting phases approached near chemical equilibrium. At constant (basaltic) bulk rock composition the MgO content of pumpellyite increases, and the XFe3+ of both pumpellyite and epidote decreases with increasing metamorphic grade, the Fe3+ being preferentially concentrated in epidote. Both pumpellyite and epidote compositions vary with the bulk rock composition at isofacial conditions; pumpellyite becomes progressively enriched in Fe and depleted in Mg from basic to intermediate and acidic bulk rock compositions. The compositional comparison of pumpellyites from high-variance (1–3 phases) assemblages in various bulk rock compositions (basic, intermediate, acidic rocks, greywackes, gabbros) shows that the compositional fields of both pumpellyite and epidote are wide and variable, broadly overlapping the compositional effects observed at varying metamorphic grade in low-variance assemblages.The intrinsic stability of both Fe- and Al-rich pumpellyites extends across the complete range of the considered metamorphic conditions. Element partitioning between coexisting phases is the main control on the mineral composition at different P-T conditions.

Notes: The Southern Brittany Migmatite Belt (SBMB), which evolved through the metamorphic peak between c. 400 Ma and c.. 370 Ma ago, consists of a heterogeneous suite of high-grade gneisses and anatectic migmatites, both metatexites and diatexites. Rare garnet-cordierite gneiss layers record evidence of an early prograde P-T path. In these rocks, growth-zoned garnet cores and a sequence of included mineral assemblages in garnet, from core to rim, of Qtz + Ilm + Ky, Pl + Ky + St + Rt + Bt and Pl + Sil + St + Rt + Bt constrain a prograde evolution during which the reactions Ilm + Ky + Qtz→ Aim + Rt, Ms + Chl→ St + Bt + Qtz + V and St + Qtz→ Grt + Sil + V were crossed. Parts of this prograde evolution are preserved as inclusion assemblages in garnet in all other rock types. In all rock types, garnet has reverse zoned rims, and garnet replacement by cordierite and/or biotite and plagioclase suggests the following reactions have occurred: Grt + Sil + Qtz→ Crd → Hc ± Ilm, Bt + Sil + Qtz → Crd ± Hc → Ilm → Kfs + V and (Na + Ca + K + Ti) + Grt → Bt + Pl + Qtz. Microstructural analysis of reaction textures in conjunction with a petrogenetic grid has enabled the construction of a tightly constrained ‘clockwise’P–T path for the SBMB. The high-temperature part of the path has a steep dT/dP slope characteristic of near isothermal decompression. It is proposed that the P-T path followed by the SBMB is the result of the inversion, by overthrusting, of a back-arc basin and that such a tectonic setting may be applicable to other high-temperature migmatite terranes. The near isothermal decompression is at least partly driven by the upward (diapiric) movement of the diatexite/anatectic granite core of the SBMB.

Notes: By collating age data based on the fossil age of the protoliths, radiometric dating of the metamorphic minerals, and sedimentary records of erosion at the earth's surface, the history of the Sanbagawa metamorphism can be summarized as follows. (1) The pre-metamorphic sedimentary rocks (Carboniferous-Jurassic + Early Cretaceous?) became mixed and formed a thickened packet in the vicinity of an ancient trench through a variety of subduction-related tectono-sedimentary processes, probably in Early Cretaceous time (c., 130-120 Ma). (2) The subducted protoliths underwent progressive metamorphism reaching a maximum depth of c. 30 km in late Early Cretaceous time (c. 116 ± 10 Ma). (3) The high-P/T metamorphic rocks began to rise toward the surface (during the interval 110-50 Ma) with minimum estimates for the average cooling rate around 9-12°C/Ma and an average uplift rate around 0.4-0.5 mm/year. (4) Finally, at some stage after reaching the erosional surface, the high-P/T metamorphic rocks were covered unconformably by the middle Eocene (c. 50-42 Ma) Kuma Group.On the basis of the present chronological summary of the Sanbagawa metamorphism, the areal extent of the Sanbagawa metamorphism is also discussed with respect to the weakly metamorphosed subduction-accretion complex of the next tectonic belt to the south, the Northern Chichibu belt.

Notes: The mineral assemblages of hematite-bearing basic schists in intermediate high-pressure metamorphism are temperature dependent. For assemblages with excess hematite, albite, muscovite and quartz, the paragenetic relations can be dealt with in terms of a four-component system, without omitting or grouping major components.In the Sanbagawa belt in central Shikoku, the dominant amphibole in the hematite-bearing basic schists changes from winchite, via crossite and barroisite to hornblende. The stability of amphibole is described chemographically within a pseudoternary system with another excess phase, epidote. Many amphiboles are chemically heterogeneous owing to retrograde reactions which produced low-T/P amphibole around the prograde amphibole. The examination of amphibole zoning makes it possible to draw a retrograde P-T trajectory which passes on the lower pressure side of the prograde one.

Notes: The dominant deformation mechanism during the Sambagawa metamorphism changes from brittle to ductile with increasing metamorphic temperature. The magnitude of plastic strains inferred from the shapes of deformed radiolaria in metachert increases sharply across the boundary between the epidote-pumpellyite-actinolite zone and the epidote-actinolite zone. The synmetamorphic crack density of metachert is an indicator of the contemporaneous brittle strain of rocks, and it decreases sharply as the grade reaches the epidote-actinolite zone. Hence, the ratio of the ductile strain to the brittle strain of metachert decreases rapidly across the transition to the epidote-actinolite zone of the Sambagawa metamorphic belt.The sharp change of the ductile strain magnitude also takes place at the epidote-actinolite grade in the Shimanto metamorphic belt of Japan, an example of the intermediate pressure facies series of metamorphism. It is concluded that the transition from brittle to ductile deformation takes place at about 300-400°C. and is independent of pressure of metamorphism.

Notes: Metamorphic mineral assemblages and textures from Early Palaeozoic continental margin rocks in north-western Newfoundland indicate that different structural levels have contrasting metamorphic histories. Rocks of the East Pond Metamorphic Suite, which represent the older, structurally lower level of the margin, experienced an early high-pressure–low-temperature stage of metamorphism (10–12 kbar minimum, 450–500°C) which produced eclogite in mafic dykes and phengite–garnet assemblages in pelites. This was overprinted by higher temperature–lower pressure amphibolite facies metamorphism (700–750°C, 7–9 kbar minimum) which produced complex symplectic textures in rocks of all compositions. Rocks of the Fleur de Lys Supergroup, which were deposited in the stratigraphically higher levels of the rifted margin, reached pressures of 7–8.5 kbar at about 450°C during the early stages of metamorphism, overprinted by assemblages which indicate maximum temperatures of 550–600°C at about 6.5 kbar. The metamorphic history of both units is interpreted to be the result of thermal relaxation following initial burial of a continental margin by overriding thrust sheets. Since there is no evidence that maximum pressures or temperatures within the Fleur de Lys Supergroup were ever as high as those reached in the East Pond Metamorphic Suite, these rocks may have followed parallel, ‘nested’P–T–t paths, with the more deeply buried East Pond Metamorphic Suite subjected to greater thermal relaxation effects. Quantitative modelling of P–T–t paths is not possible with the present data, owing to both large uncertainties in P–T estimates, and in the time of metamorphism.

Notes: Eclogites in the Tromsø area, northern Norway, are intimately associated with meta-supracrustals within the Uppermost Allochthon of the Scandinavian Caledonides (the Tromsø Nappe Complex). The whole sequence, which includes pelitic to semipelitic schists and gneisses, marbles and calc-silicate rocks, quartzofeldspathic gneisses, metabasites and ultramafites, has undergone three main deformational/metamorphic events (D1/M1, D2/M2 and D3/M3). Detailed structural, microtextural and mineral chemical studies have made it possible to construct separate P–T paths for these three events.Chemically zoned late syn- to post-D1 garnets with inclusions of Bt, Pl and Qtz in Ky-bearing metapelites indicate a prograde evolution from 636°C, 12.48 kbar to c. 720°C, 14–15 kbar. This latter result is in agreement with Grt–Cpx geothermometry and Grt–Cpx–Pl–Qtz geobarometry on eclogites and trondhjemitic to dioritic gneisses. Maximum pressures at c. 675°C probably reached 17–18 kbar based on Cpx–Pl–Qtz inclusions in eclogitic garnets, and Grt–Ky–Pl–Qtz and Jd–Ab–Qtz in trondhjemitic gneisses. Post-D1/pre-D2 decompressional breakdown of the high-P assemblages indicates a substantial drop in pressure at this stage. Inclusions and chemical zoning in syn- to post-D2 garnets from metapelites record a second episode of prograde metamorphism, from 552°C, 7.95 kbar, passing through a maximum pressure of 10.64 kbar at 644°C, with final equilibration at c. 665°C, 9–10 kbar. The corresponding apparently co-facial paragenesis Grt + Cpx + Pl + Qtz in metabasites yields c. 635°C, 8–10 kbar. In the metapelites post-D3, Grt in apparent equilibrium with Bt, Phe and Pl yield c. 630°C, 9 kbar. The D1/M1 and D2/M2 episodes are exclusively recorded in the Tromsø Nappe Complex and must thus pre-date the emplacement of this allochthonous unit on top of the underlying Lyngen Nappe, while the D3/M3 episode is common for the two units.A previously published Sm–Nd mineral isochron (Grt–Cpx–Am) on a partly retrograded and recrystallized ecologite of 598 ± 107 Ma represents either the timing of formation of the eclogites or the post-eclogite/pre-D2 decompression stage, while a Rb–Sr whole rock isochron of an apparently post-D1/pre-D2 granite of 433 ± 11 Ma is consistent with a K–Ar age of post-D1/pre-D2 amphiboles from a retrograded eclogite of 437 ± 16 Ma which most likely record cooling below the 475–500°C isotherm after the M3 metamorphism.

Notes: An occurrence of quartz-eclogite is described from the Inner Schieferhülle unit of the Pennine Basement Complex in the SE Tauern Window, Austria.Field relations strongly suggest a pre-Alpine age for the primary eclogitic mineral assemblage (garnet + omphacite + quartz + rutile). This implies that there was no connection between the formation of these eclogites and the late Cretaceous and Tertiary tectonic evolution of the Eastern Alps. The quartz-eclogite mineral assemblage crystallized under conditions of 620 ± 100°C and at pressures in excess of 12 kbar, and suffered amphibolitic overprinting of Alpine and possibly Hercynian age.A four-stage polymetamorphic history is proposed for the Inner Schieferhülle:

Notes: Mafic and ultramafic xenoliths in a basaltic cone at The Anakies in south-eastern Australia are geochemically equivalent to continental basaltic magmas and cumulates. The xenolith microstructures range from recognizably meta-igneous for intrusive rocks to granoblastic for garnet pyroxenites. Contact relationships between different rock types within some xenoliths suggest a complex petrogenesis of multiple intrusive, metamorphic and metasomatic events at the crust/mantle boundary during the evolution of south-eastern Australia. Unaltered spinel lher-zolite, typical of the uppermost eastern Australian mantle, is interleaved with or veined by the metamorphosed intrusive rocks of basaltic composition.Geothermobarometry calculations by a variety of methods show a concordance of equilibration temperatures ranging from 880°C to 980°C and pressures of 12 to 18 kbar (1200-1800 mPa). These physical conditions span the gabbro to granulite to eclogite transition boundaries. The water-vapour pressure during equilibration is estimated to be about 0.5% of the load pressure, using amphibole breakdown data. Large fluid inclusions of pure CO2 are abundant in the mineral phases in the xenoliths, and it is suggested that flux of CO2 from the mantle has been an important heat source and fluid medium during metamorphism of the mafic and ultramafic protoliths at the lower crust/upper mantle boundary.The calculated pressures and temperatures suggest that the south-eastern Australian crust has sustained a high geothermal gradient. In addition, the nature of the mineral assemblages and the contact relationships of granulitic rock with spinel lherzolite, characteristic of mantle material, suggest that the Moho is not a discrete feature in this region, but is represented by a transition zone approximately 20 km thick. These inferences are in agreement with geophysical data (including seismic, heat-flow and electrical resistivity data) determined for south-eastern Australia.Underplating at the crust/mantle boundary by continental basaltic magmas may be an important alternative or additional mechanism to the conventional andesite model for crustal accretion.

Notes: Magnesian metapelites of probable Archaean age from Forefinger Point, SW Enderby Land, East Antarctica, contain very-high-temperature granulite facies mineral assemblages, which include orthopyroxene (8–9.5 wt% Al2O3)–sillimanite ± garnet ± quartz ± K-feldspar, that formed at 10 ± 1.5 kbar and 950 ± 50°C. These assemblages are overprinted by symplectite and corona reaction textures involving sapphirine, orthopyroxene (6–7 wt% Al2O3), cordierite and sometimes spinel at the expense of porphyroblastic garnet or earlier orthopyroxene–sillimanite. These textures mainly pre-date the development of coarse biotite at the expense of initial mesoperthite, and the subsequent formation of orthopyroxene (4–6 wt% Al2O3)–cordierite–plagioclase rinds on late biotite.The early reaction textures indicate a period of near-isothermal decompression at temperatures above 900°C. Decompression from 10 ± 1.5 kbar to 7–8 kbar was succeeded by biotite formation at significantly lower temperatures (800–850°C) and further decompression to 4.5 ± 1 kbar at 700–800°C.The later parts of this P–T evolution can be ascribed to the overprinting and reworking of the Forefinger Point granulites by the Late-Proterozoic (c. 1000 Ma) Rayner Complex metamorphism, but the age and timing of the early high-temperature decompression is not known. It is speculated that this initial decompression is of Archaean age and therefore records thinning of the crust of the Napier Complex following crustal thickening by tectonic or magmatic mechanisms and preceding the generally wellpreserved post-deformational near-isobaric cooling history of this terrain.

Notes: Two fundamentally different scales of element mobility have been identified in the upper-amphibolite-facies Hunts Brook fault zone of south-central Connecticut, USA. Field relations, mineral chemistry, and 80 bulk rock analyses provide overwhelming evidence that the blastomylonitic schists and gneisses of the fault zone were derived from the enclosing granodioritic Rope Ferry orthogneiss. Two-sample mass balance calculations between the Rope Ferry Gneiss and fault rocks strongly suggest that the Rope Ferry Gneiss was segregated into biotite-rich schists and quartz–plagioclase-rich gneisses through the centimetre-scale transfer of Si, Al, Ca, Na, Ba, and Zr from schists to gneisses. Three- and four-sample mass balance calculations provide convincing evidence that Al, Ca, Na, and Ba were lost and Si and K gained by the entire fault zone. Both scales of metasomatism have been identified at two localities separated by 20 km, implying that the metasomatic processes were pervasive throughout the fault zone.From the mass balance calculations, an apparent disparity in K mobility arises. K appears to be gained by the entire fault zone, but is immobile during the centimetre-scale segregation. This is because mass balance calculations can only detect differential element mobility. Differential element mobility requires that the mechanism of metasomatism produces chemical potential gradients. Therefore, the identification of differentially mobile elements provides insight into the mechanisms of metasomatism. The immobility of K during segregation of schists and gneisses implies that the segregation was not achieved through the extraction of partial melt. However, the element mobility is reconcilable with deformation-driven metamorphic differentiation. The gains of Si and K and losses of Ca, Na, Al, and Ba for the entire fault zone are also inconsistent with the intrusion or extraction of partial melt, but may reflect the infiltration of a metasomatizing aqueous fluid.

Notes: INTRODUCTION TO METAMORPHIC TEXTURES AND MICROSTRUCTURES. By A. J. Barker. Blackie, Glasgow, 1989. ECLOGITE FACIES ROCKS. Edited by D. A. Carswell. Blackie, Glasgow, 1990. EVOLUTION OF METAMORPHIC BELTS. Edited by J. S. Daly, R. A. Cliff & B. W. D. Yardley. AN INTRODUCTION TO METAMORPHIC PETROLOGY. By B. W. D. Yardley.

Notes: The thermal structure of the Sambagawa belt, which is reflected by minerals produced during the highest temperature of metamorphism, generally is characterized by the occurrence of the highest grade schists in the middle of the structural pile. The origin of this structure has been analysed in the upper horizon of the Sambagawa schist sequence in Central Shikoku as an example for the structure of the whole belt. The upper horizon of the Sambagawa schist sequence in Central Shikoku consists of three nappes, the Saruta nappe II, the Saruta nappe I and the Fuyunose nappe in descending order of structural level. The Saruta nappe II shows a downward increase of metamorphic grade from the garnet zone, through the albite-biotite zone, to the oligoclase-biotite zone. The Saruta nappe I consists mainly of rocks in the albite-biotite zone and partly in the oligoclase-biotite zone, but the direction of the increase of metamorphic grade is not clear. The Fuyunose nappe shows an upward increase in metamorphic grade which changes from the glaucophane zone to the barroisite zone. It is concluded that the Saruta nappe II and Saruta nappe I were overturned and then mechanically coupled with the Fuyunose nappe. The Sambagawa metamorphic field, which is of the highest temperature phase of metamorphism, appears to have had an inverted thermal gradient and a thermal structure comparable with that expected in the deeper parts of a subduction complex.

Notes: Middle Eocene conglomerates which overlie the Sanbagawa metamorphic rocks contain clasts of metamorphic rock with isotope ages of 120-85 Ma, which fall within the age range reported from the Sanbagawa metamorphic rocks. They were derived from the chlorite to oligoclase zones of the Sanbagawa metamorphic belt. Clasts of garnet amphibolite and oligoclase-biotite schist show a mineral assemblage similar to the highest grade Sanbagawa schists. However, the metamorphic temperatures estimated by various mineralogical thermometers show that some of the clasts were formed at higher temperatures than the in situ Sanbagawa metamorphic rocks. Such higher grade rocks were at the surface by the Middle Eocene and for the most part they have been eroded away. Cretaceous and post-Cretaceous sediments overlie, or are in fault contact with, the Sanbagawa metamorphic rocks which suggests that rocks in the belt were uplifted and eroded from the latest Cretaceous to Middle Eocene time after strike-slip movement along the Median Tectonic Line. Since the Middle Eocene, the belt has experienced relatively slow uplift which was locally around 2 km in central Shikoku.

Notes: METPET is a package of three interactive microcomputer (IBM PC or compatible) programs. FILEMAN is a utility program to create, edit and print ‘composition files’, i.e. files containing the records of chemical compositions of minerals or rocks, expressed in terms of primary chemical components. PROJECT recalculates selected compositions in terms of new (secondary) components. It then projects these compositions onto a subspace defined by two, three or more of the secondary components, first giving a plot on the screen and then, if requested by the user, on a selected graphic device. REACT calculates a possible set of independent reactions between a set of phases, whether pure compounds or solutions. Any linear combination of the independent reactions can be calculated on request.

Notes: Metasediments in the southern Grossvenediger area (Tauern Window, Austria) were studied along a cross-section through rocks of increasing metamorphic grade from the margin of the Tauern Window in the south to the base of the Upper Schieferhülle, including the Eclogite Zone, in the north.In the southern part of the cross-section there is no evidence for a pre-late Alpine metamorphic history in the form of high-pressure relics or pseudomorphs. Mineral assemblages are characterized by the stability of tremolite + calcite, biotite + calcite and biotite + chlorite + calcite. In the northern part a more complete Alpine metamorphic evolution is preserved. Primary high-pressure assemblages are dolomite + quartz, tremolite + zoisite, zoisite + dolomite + quartz + phengite I and probably tremolite + dolomite + phengite I. Secondary, post-kinematic assemblages [tremolite + calcite, talc + calcite, phengite II + chlorite + calcite (+ quartz), biotite + chlorite + calcite, biotite + zoisite + calcite] formed as a result of the dominant late Alpine metamorphic overprint. The occurrence of biotite + zoisite + calcite is confined to the northernmost area and defines a biotite–zoisite–calcite isograd. P–T estimates based on standard thermobarometric techniques and on stability relationships of tremolite + calcite + dolomite + quartz and zoisite give consistent results. P–T conditions of the main Tertiary metamorphic overprint were 525° C, P= 7.5 ± 1 kbar in the northern part of the cross-section. The southern part was metamorphosed at lower temperatures of 430–470° C. The Si-content of phengites from this area is almost as high as that of phengites from the Eclogite Zone (Simax= 3.4 pfu). Pressures 〉 10 kbar at 420° C are suggested by phengite barometry according to Massone & Schreyer (1987). In the absence of high-pressure relics or pseudomorphs, these phengites, which lack late Alpine re-equilibration, are the only record that rocks of the southern part probably also experienced an early non-eclogitic high-pressure metamorphism.

Notes: Porphyroblasts of garnet and plagioclase in the Otago schists have not rotated relative to geographic coordinates during non-coaxial deformation that post-dates their growth. Inclusion trails in most of the porphyroblasts are oriented near-vertical and near-horizontal, and the strike of near-vertical inclusion trails is consistent over 3000 km2. Microstructural relationships indicate that the porphyroblasts grew in zones of progressive shortening strain, and that the sense of shear affecting the geometry of porphyroblast inclusion trails on the long limbs of folds is the same as the bulk sense of displacement of fold closures. This is contrary to the sense of shear inferred when porphyroblasts are interpreted as having rotated during folding.Several crenulation cleavage/fold models have previously been developed to accommodate the apparent sense of rotation of porphyroblasts that grew during folding. In the light of accumulating evidence that porphyroblasts do not generally rotate, the applicability of these models to deformed rocks is questionable.Whether or not porphyroblasts rotate depends on how deformation is partitioned. Lack of rotation requires that progressive shearing strain (rotational deformation) be partitioned around rigid heterogeneities, such as porphyroblasts, which occupy zones of progressive shortening or no strain (non-rotational deformation). Therefore, processes operating at the porphyroblast/matrix boundary are important considerations. Five qualitative models are presented that accommodate stress and strain energy at the boundary without rotating the porphyroblast: (a) a thin layer of fluid at the porphyroblast boundary; (2) grain-boundary sliding; (3) a locked porphyroblast/matrix boundary; (4) dissolution at the porphyroblast/matrix boundary, and (5) an ellipsoidal porphyroblast/shadow unit.

Notes: The Anmatjira Range and adjacent Reynolds Range, central Australia, comprise early Proterozoic metasediments and othogneisses that were affected by three, and possibly four, temporally distinct metamorphic events, M1–4, and deformation events, D1–4, in the period 1820–1590 Ma. The north-western portion of the range, around Mt Stafford, preserves the effects of ±1820 Ma M1-D1, and shows a spectacular lateral transition from muscovite + quartz-bearing schists to interlayered andalusite-bearing migmatites and two-pyroxene granofelses that reflect extremely low-pressure granulite facies conditions, over a distance of less than 10 km. Orthopyroxene + cordierite + garnet + K-feldspar + quartz-bearing gneisses occur at the highest grade, implying peak conditions of ±750°C and 2.5 ± 0.6 kbar. An anticlockwise P–T path for M1 is inferred from syn- to late-D1 sillimanite overprinting andalusite, petrogenetic grid considerations and quantitative estimates of metamorphic conditions for inferred overprinting assemblages. The effects of M1 have been variably overprinted to the south-east by a c. 1760 Ma M2–D2 event. Much of the central Anmatjira Range, around Ingellina Gap, comprises orthogneiss, deformed during D2, and metapelites that have M1 andalusite and K-feldspar overprinted by M2 sillimanite and muscovite. The south-eastern portion of the range, around Mt Weldon, comprises metasediments and orthogneisses that were completely recrystallized during M2–D2, with metapelitic gneisses characterized by spinel + sillimanite + K-feldspar + quartz-bearing assemblages that suggest peak M2 conditions of 〉750°C and 5.5 ± 1 kbar. Overprinting parageneses in metapelitic gneisses imply that D2 occurred during essentially isobaric cooling. A third granulite facies event, M3, affected rocks in the Reynolds Range, immediately to the south of the Anmatjira Range, at c. 1730 Ma. A possible fourth event, M4, with a minimum age of c. 1590 My affected both Ranges, but resulted in only minor overprinting of M1–3 assemblages. The superimposed effects of M1–4, mapped for the entire Anmatjira–Reynolds Range area, indicate that only minor or no dislocation of the regional geology occurred during any of the metamorphic and accompanying folding, events. Although the immediate cause of each of the metamorphic events involved advection, the ultimate causes were external to the metasediments and most probably external to the crust.

Notes: Abstract. In the Kamuikotan zone, central Hokkaido, Japan, two distinct types of metamorphic rocks are tectonically mixed up, along with a great quantity of ultramafic rocks; one type consists of high-pressure metamorphic rocks, and the other of low-pressure ones. The high-pressure metamorphic rocks are divided into two categories. (1) Prograde greenschist to glaucophaneschist facies rocks derived from mudstone, sandstone, limestone, a variety of basic rocks such as pillow and massive lavas, hyaloclastite and tuff, and radiolarian (Valanginian to Hauterivian) chert, among which the basic rocks and the chert, and occasionally the sandstone, occur as incoherent blocks (or inclusions) enveloped by mudstone. (2) Retrograde amphibolites with minor metachert and glaucophane-calcite rock, which are tectonic (or exotic) blocks enclosed within prograde mudstone or serpentinite, or separated from these prograde rocks by faults. The K-Ar ages of the prograde metamorphic rocks (72, 107 and 116 Ma on phengitic muscovites) are younger than those of the retrograde rocks (109, 132, 135 and 145 Ma on muscovites, and 120 Ma on hornblende). The low-pressure metamorphic rocks consist of the mafic members of an ophiolite sequence with a capping of radiolarian (Tithonian) chert with the metamorphic grade ranging from the zeolite facies, through the greenschist (partly, actinolite-calcic plagioclase) facies to the amphibolite (partly, hornblende-granulite) facies. The low-pressure metamorphism has a number of similarities with that described for‘ocean-floor’metamorphism. The tectonic evolution of such a mixed-up zone is discussed in relation to Mesozoic plate motion.

Notes: The rocks of the Scourian Complex have been intensively studied, but there is still no consensus as to the conditions of the granulite-facies metamorphism preserved in these rocks. Recent estimates of these conditions fall into two groups, one at 820-920°C and ca. 11 kbar and the second at ca. 1000°C and 〉12 kbar. Investigation of a variety of rocks shows that the recorded conditions vary with grain-size, with higher-grade conditions recorded by the cores of coarser (ca. 10 mm) crystals, and lower-grade conditions recorded by the rims of coarser grains and by finer grains. This observation suggests that re-equilibration during recovery of these rocks to the surface has been important which may account for the discrepancy in estimated P-T conditions. Revised estimates of the equilibration conditions of the Scourian Complex of T 〉 1000°C and P 〉 8.5 kbar are presented. The conditions suggested for the peak of metamorphism mean that the role of anatexis in the genesis of these rocks must be considered and the nature of the fluid phase thoroughly investigated.

Notes: Abstract. Plagioclase porphyroblasts from silvergrey schists belonging to the Nevado Filabride Complex in the Sierra Alhamilla (Betic Zone, SE Spain) are interpreted as having been formed preand synkinematically with respect to the second phase of deformation. Different types of inclusion patterns represent 'snap-shots’(high growth-rate/strain-rate ratio features) of the formation of a diffentiated crenulation cleavage during this second phase of deformation, by the processes of kinking, crenulation and associated differentiation.Regional considerations indicate an Alpine age for this tectono-metamorphic event, which can be explained by the‘hot emplacement’of the higher Nevado Filabride units. The observed structural evolution is not consistent with a pre-Alpine polyphase deformation history.

Notes: Evidence from rock microstructures, mass transfer and isotopic exchange indicates that substantial quantities of aqueous fluids are involved in low- and medium-grade regional metamorphism. Similar conclusions are drawn from many retrograde environments, whereas high-grade metamorphic fluids may be melt dominated. The mobile fluids play essential roles in metamorphic reactions, mass transport and deformation processes. These processes are linked by the mechanical consequences of metamorphic fluid pressures (Pf) generally being greater than or equal to the minimum principal compressive stress. Under such conditions metamorphic porosity comprises grain boundary tubules and bubbles together with continuously generated (and healed) microfractures. Deformation results in significant interconnected porosity and hence enhanced permeability. Lithologically and structurally controlled permeability variations may cause effective fluid channelling.Simple Rayleigh-Darcy modelling of a uniformly permeable, crustal slab shows that convective instability of metamorphic fluid is expected at the permeabilities suggested for the high Pf metamorphic conditions. Complex, large-scale convective cells operating in overpressured, but capped systems may provide a satisfactory explanation for the large fluid/rock ratios and extensive mass transport demonstrated for many low- and medium-grade metamorphic environments. Such large-scale fluid circulation may have important consequences for heat transfer in and the thermal evolution of metamorphic belts.

Notes: Hydrothermal synthesis of Fe-pum-pellyites was conducted using high pressure cold-seal apparatus and solid oxygen buffering techniques at temperatures between 250°C and 550°C and 2.0–9.1 kbar Pfluid. Fe-pumpellyites were synthesized from partially crystalline gel mixtures of compositions: 4CaO - 2.1Al2O3_1.5FeO - 0.3MgO - 6SiO2 (II) and 3CaO - 1.5 Al2O3 - 2.7FeO - 0.3MgO - 6SiO2 (III) in the presence of excess H2O at Pfluid of 5–9.1 Kbar, temperatures between 275°C and 325°C, and fO2 defined by the QFM and HM buffers; for both of these compositions (II and III), the condensed synthetic run products included minor 7Å chlorite ± garnet ± Fe-oxide. The cell dimensions and aggregate refractive index (a= 19.13(2)Å, b= 5.940(4)Å, c= 8.847(5)Å, ±= 97.37(6)±, and n= 1.702(2)) of the pum-pellyite synthesized from the bulk composition II mix are compatible with those of natural pumpellyites containing similar total Fe contents. Attempts at synthesizing Fe-pumpellyites from a Mg-free bulk composition were not successful; these results are consistent with the total absence of natural Mg-free pumpellyites.The higher temperature, higher oxygen fugacity assemblages of the equivalent bulk compositions (II and III) consist of epidote ± minor amounts of chlorite, garnet, quartz, hematite, and magnetite. The results of these synthesis experiments accord with the mineral parageneses observed in low-grade metabasites which imply that Fe-pumpellyites are replaced by epidote with increasing temperature and/or fO2 and that Fe3+ is preferentially partitioned into epidote with respect to coexisting pum-pellyite. In addition, these synthesis experiments indicate that Fe-bearing pumpellyites crystallize at and are stable to lower temperatures than more aluminous pumpellyites—a result also consistent with natural systems.

Notes: This review of digital image processing refers to the pioneer work of Helava and Hobrough which has influenced the most recent trends in photogrammetry. The author goes on to discuss aspects of digital image acquisition, storage and display, as well as digital photogrammetric procedures and systems.

Notes: Site procedures, instrumentation, analytical methods and accuracies achieved are described for the measurement of the deformation of a military steel bridge under load in a test gantry. Some remarks concerning the advantages and disadvantages of photogrammetry as a method of industrial measurement are made.

Notes: An account is given of the importance of photogrammetric techniques in industrial three dimensional problems and the way in which obtaining data in this environment differs from the more common applications. Possible system arrangements are discussed. The particular choice at Imperial College and the resulting system speed and accuracy are presented.

Notes: Lasertrace is a high accuracy measurement system for the remote, non-contact determination of position, velocity, or acceleration in two or three dimensions. It uses advanced two axis laser steering technology to locate and measure the angular position, from itself, of an identified point on an object under investigation. If the object subsequently moves, the steerable laser beam actually tracks the point providing updated position coordinates as it does so. An operating window of 40° in both axes guarantees system versatility in a wide range of applications.

Notes: Optical triangulation is used in the human visual system and surveying tacheometers to estimate distance. This method is now used in systems with solid state sensors which enable fast measurement of distance with sufficiently high accuracy for many applications. City University has built on past experience to develop the optical triangulation technique to gather data appertaining to cross sections or profiles of structures in the range 0.2 m to 20 m radius from the measurement axis. Results obtained using three prototypes are given.

Notes: The author, a research and development manager at Ordnance Survey, reviews current developments in photogrammetry including the automatic correlation of image points for aerial triangulation, digital photogrammetric map revision, mapping from SPOT imagery and progress in aerial photography.

Notes: This study of coastal air survey draws together the main characteristics of the coastal zone, scientific sites of interest, statutory spheres of responsibility, existing coastal photography and survey, and evidence of survey practices by many with responsibilities in these environments. In contrast to the surveyor/photogrammetrist steeped in survey techniques and map use, the majority of people who commission and use air photographs and photogrammetric mapping have very different backgrounds and interests and have widely differing objectives. They come largely from the disciplines of economics, planning, engineering, geography, biological sciences and accountancy. They, too, have their own view of the value of air survey and the analysis here of the trends in demand and use for such material suggests that these sources of information play only a minor and occasional part in their everyday work.

Notes: This paper presents all the stages involved in the procedure for the determination of the shape of a fuel assembly, which is an essential part of a nuclear power plant and can only be handled underwater. Phototriangulation is used to obtain orientation elements, taking into account light refracting surfaces. Stereomodels are then set up for analytical restitution and the shape parameters for the object can be obtained. The project is a typical example of high precision underwater photogrammetry.

Notes: Book review in this Article:PHOTOGRAMMETRY APPLIED TO SURVEYS OF MONUMENTS AND HISTORIC CENTRES. By M. Carbonnell. English translation by R. W. A. Dallas and K. V. Parker.ELECTRONIC DISTANCE MEASUREMENT. Third Edition. By J. M. Rüeger.RECONNAISSANCE, ASTRONOMY, REMOTE SENSING AND PHOTOGRAMMETRY. Edited b I Hirschberg.SATELLITE DATA: PROCESSING, ARCHIVING AND DISSEMINATION. Volume 1 Applications and Infrastructure. By D. R. Sloggett.SATELLITE DATA PROCESSING, ARCHIVING AND DISSEMINATION. Volume 2 Functions, Operational Principles and Design. By D. R. Sloggett.GPS: A GUIDE TO THE NEXT UTILITY. By J. Hurn.RADARGRAMMETRIC IMAGE PROCESSING. By F. W. Leberl.REMOTE SENSING OF SOILS AND VEGETATION IN THE USSR. By P. J. Curran, G. M. Foody, K. Ya. Kondratyev, V. V. Kozoderov and P. P. Fedchenko.ENGINEERING SURVEYING TECHNOLOGY. Edited by T. J. M. Kennie and G. Petrie.ACCURACY OF SPATIAL DATABASES. Edited b M. F. Goodchild and S. Gopal.CARTOGRAPHY PAST, PRESENT AND FUTURE A Festschrift for F. J. Ormeling. Edited by D. W. Rhind and D. R. F. Taylor.HIGH PRECISION NAVIGATION. Edited by K. Linkwitz and U. Hangleiter.INVENTORY OF WORLD TOPOGRAPHIC MAPPING. Volume 1 Western Europe, North America and Australasia. Compiled by R. Böhme.ADVANCED PHOTOGRAPHY. B M. Langford.PHOTOGRAMMÉTRIE ET SYSTÈMES D'INFORMATION DU TERRITOIRE. Directeur de la publication O. Kölbl.

Notes: Underwater photogrammetry is being used in the particularly hostile environment of the North Sea where it has been put into commercially viable operation. The authors discuss underwater photogrammetry related to other means of inspection of oil platforms. They also deal with operational experience of 35 mm and 70 mm cameras, camera calibration, the provision of control and photogrammetric observations and data analysis. The demand for underwater photogrammetry continues to grow.

Notes: This paper summarises the theoretical and practical development of’an analytical system for close range photogrammetry. The system uses the extended bundle method of phototriangulation and a sophisticated least squares algorithm. A description is given of computer software, and aspects of statistical testing and gross error detection are discussed in order to assess the accuracy potential. Applications of the system, for precise co-ordination of a target range and camera calibration are outlined.

Notes: A photogrammetric system that is suitable for shallow water detailed mapping at scales from 1:50 to 1:500 for coastal and harbour engineering projects is described. The results from tests using automatic 35 mm Canon cameras on an elevated platform to determine the accuracy of planimetric and depth co-ordinates are presented. The economic benefits of stereophotography through shallow water rather than underwater photography are discussed.

Notes: This paper reviews the growth in the use of photogrammetric techniques in architecture, principally in the United Kingdom, over the past ten years. The work of the various establishments involved in architectural photogrammetry is described and the results of a questionnaire, distributed within the architectural profession, are analysed. Some comparisons are made with developments elsewhere in Europe.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméOn examine dans cet article l'extension qu'a connue l'utilisation des méthodes photogrammétriques en architecture au cows des dix dernières années, principalement dans le Royaume-Uni. On y décrit les travaux des divers organismes impliqués dans la photogrammétrie architecturale et l'on y analyse les résultats d'un questionnaire diffusé au sein de la profession liée à l'architecture. On fournit enfin quelques comparaisons avec les développements constatés par ailleurs en Europe.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungIm Artikel wird über die zunehmende Anwendung photogrammetrischer Verfahren während der letzten 10 Jahre in der Architektur, insbesondere im Vereinigten Königreich, berichtet. Die Arbeit verschiedener Institutionen, die sich mit Architekturphotogrammetrie befassen, wird beschrieben, und es werden die Ergebnisse eines unter Architekten verteilten Fragebogens analysiert. Weiterhin werden Vergleiche zu Entwicklungen in anderen europäischen Ländern gezogen.