ALBERT

Notizen: Granulites exposed in the Reinbolt Hills, East Antarctica, are part of the extensive Late Proterozoic granulite complex of East Antarctica, which includes the Rauer Group to the east and the northern Prince Charles Mountains to the west. The deformation history includes three pervasive deformation phases. No chemical or mineralogical distinction between these phases has been detected and this is interpreted to be the result of complete re-equilibration at the end of the third deformation phase. Two late deformation phases post-date the metamorphism and record a medium-temperature cooling path. A short segment of the P–T path of these rocks was inferred from mineral reactions that occurred during these late deformation phases. The path passes from 800°C, 7 kbar to 690°C, 5 kbar, indicating strong decompression, which is typical of a thrust-dominated crustal thickening followed by rapid erosion or extensional collapse.

Notizen: Mafic granulite, garnet amphibolite and charnockite occur in the southwest Swedish part of the Baltic Shield. This part is generally considered to be the continuation of the Grenville collisional belt in Canada. The area with granulite facies rocks, the Southwest Swedish Granulite Region (SGR), is considerably larger than previously thought. The SGR is bounded to the east and west by two major tectonic zones. The first quantitative age data and P–T determinations for the high-grade metamorphism in the SGR are presented.Conventional geothermobarometry was applied to mafic granulites from five localities. The estimated P–T conditions for the peak of metamorphism range from 705°C and 8.1 kbar at Hallandsås in the south, to 770°C and 10.5 kbar at Ullared in the north (medium- to high-P granulite facies conditions). Sm–Nd geochronology on minerals from the mafic granulites at Hallandsås and Ullared give late Sveconorwegian (Grenville) ages of 907 ± 12 and 916 ± 11 Ma for the high-grade metamorphism, which is considerably younger than previously thought.Our results stress the hitherto underestimated importance of the late Sveconorwegian high-grade metamorphism in the southwestern part of the Baltic Shield.

Notizen: Dark hornblende + garnet-rich, quartz-absent metagabbro boudins from the Seguin subdomain, Ontario Grenville Province, are transected by anastomosing light-coloured veins rich in orthopyroxene, clinopyroxene, plagioclase and sometimes quartz. The veins vary in texture from fine-grained diffuse veins and patches that overprint the metagabbro, to coarse tonalitic leucosomes with sharp borders. The diffuse veins and patches are suggestive of channellized subsolidus dehydration of the metagabbro, while the tonalitic leucosomes are suggestive of local internally-derived anatexis. All vein types grade smoothly into each other, with the tonalitic leucosomes being the latest.Relative to the host metagabbro, the veins have higher Si, Na, Ba & Sr, lower Fe, Mg, Ca & Ti, and similar Al. The coarser veins are enriched in K. Plagioclase becomes steadily enriched in Na in the transition from host metagabbro (An47) to the veins (An35), and in the coarsest veins it is antiperthitic. Differences in composition of the other minerals between host metagabbro and vein are minor. Pressure–temperature estimates are scattered, but indicate a minimum temperature during vein formation of 700°C at about 8 kbar.Mass balance constraints indicate that the veins formed from the metagabbro in an open system. The transecting veins are interpreted to represent pathways of Si + Na + Ba + Sr ± K ± Al-enriched, low aH2O fluids that metasomatized the host metagabbro to form the anhydrous veins. An initial period of localized solid-state dehydration of the metagabbro, represented by the diffuse veins, was followed by a transition to localized anatexis, represented by the tonalitic leucosomes. The change to anatexis may have been due to the addition of K to the infiltrating fluid. The source and delivery mechanism of the fluids is unknown.

Notizen: Eclogite facies mineral assemblages are variably preserved in mafic and ultramafic rocks within the Western Gneiss Region (WGR) of Norway. Mineralogical and microstructural data indicate that some Mg–Cr-rich, Alpine-type peridotites have had a complex metamorphic history. The metamorphic evolution of these rocks has been described in terms of a seven-stage evolutionary model; each stage is characterized by a specific mineral assemblage. Stages II and III both comprise garnet-bearing mineral assemblages. Garnet-bearing assemblages are also present in Fe–Ti-rich peridotites which commonly occur as layers in mafic complexes. Sm–Nd isotopic results are reported for mineral and whole rock samples from both of these types of peridotites and related rocks.The partitioning of Sm and Nd between coexisting garnet and clinopyroxene is used to assess chemical equilibrium. One sample of Mg–Cr-type peridotite shows non-disturbed partitioning of Sm and Nd between Stage II garnet and clinopyroxene pairs and yields a garnet–clinopyroxene–whole-rock date of 1703 ± 29 Ma (I= 0.51069, MSWD = 0.04). This is the best estimate for the age of the Stage II high-P assemblage. Other Stage II garnet–clinopyroxene pairs reflect later disturbance of the Sm–Nd system and yield dates in the range 1303 to 1040 Ma. These dates may not have any geological significance. Stage III garnet–clinopyroxene pairs typically have equilibrated Sm–Nd partitioning and two samples yield dates of 437 ± 58 and 511 ± 18 Ma. This suggests that equilibration of the Stage III high-P assemblage is related to the Caledonian orogeny and is more or less contemporaneous with high-P metamorphism of ‘country-rock’eclogites in the surrounding gneisses. The Sm–Nd mineral data for the Fe–Ti-rich garnet peridotites and for a superferrian eclogite, which occurs as a dyke within the Gurskebotn Mg–Cr-type peridotite, are consistent with a Palaeozoic high-P metamorphism.Finally a synoptic P–T–t path is proposed for the Mg–Cr-type peridotites which is consistent with the petrological and geochronological data.

Notizen: Compositional zoning in biotite–garnet pairs in metamorphic rocks from eastern Finland has been studied. The Mg profiles in the garnet side of biotite–garnet crystal pairs have been interpreted by means of Lasaga's theory (geospeedometry). However, the binary interdiffusion equations are first reformulated by starting from a ternary system and using the lattice fixed frame of reference. This frame of reference gives the fluxes directly by means of the numbers of diffusing ions, which helps to check the 1-dimensionality of the analysis assumed in Lasaga's theory. It is also shown that the recently argued effect of the third cation Ca is negligible in our samples. We were able to investigate satisfactory profiles in three samples from different areas. The values for the cooling rate are a few degrees per million years if the diffusion data obtained by Freer are adopted. The cooling rates are in agreement with recent estimates based on the K–Ar ages on biotite in the same areas.

Notizen: In the Caledonide orogen of northern Sweden, the Seve Nappe Complex is dominated by rift facies sedimentary and mafic rocks derived from the Late Proterozoic Baltoscandian miogeocline and offshore-continent–Iapetus transition. Metamorphic breaks and structural inversions characterize the nappe complex. Within the Sarek Mountains, the Sarektjåkkå Nappe is composed of c. 600-Ma-old dolerites with subordinate screens of sedimentary rocks. These lithological elements preserve parageneses which record contact metamorphism at shallow crustal levels. The Sarektjåkkå Nappe is situated between eclogite-bearing nappes (Mikka and Tsäkkok nappes) which underwent high-P metamorphism at c. 500 Ma during westward subduction of the Baltoscandian margin. 40Ar/39Ar mineral ages of c. 520–500 Ma are recorded by hornblende within variably foliated amphibolite derived from mafic dyke protoliths within the Sarektjåkkå Nappe. Plateau ages of 500 Ma are displayed by muscovite within the basal thrust of the nappe and are consistent with metamorphic evidence which indicates that the nappe escaped crustal depression as a result of detachment at an early stage of subduction. Cooling ages recorded by hornblende from variably retrogressed eclogites in the entire region are in the range of c. 510–490 Ma and suggest that imbrication of the subducting miogeocline was followed by differential exhumation of the various imbricate sheets. Hornblende cooling ages of 470–460 Ma are recorded from massive dyke protoliths within the Sarektjåkkå Nappe. These are similar to ages reported from the Seve Nappe Complex in the central Scandinavian Caledonides. Probably these date imbrication and uplift related to Early Ordovician arrival of outboard terranes (e.g. island-arc sequences represented by structurally lower horizons of the Köli Nappes).Metamorphic contrasts and the distinct grouping of mineral cooling ages suggest that the various Seve structural units are themselves internally imbricated, and were individually tectonically uplifted through argon closure temperatures during assembly of the Seve Nappe Complex. The cooling ages of 520–500 Ma recorded within Seve terranes and along terrane boundaries of the Sarek Mountains provide evidence of significant accretionary activity in the northern Scandinavian Caledonides in the Late Cambrian–Early Ordovician.

Notizen: Abstract Aegirine–jadeite clinopyroxene (〉60 mol% jadeite) locally occurs within blueschists of the ‘Lower Allochthon’exposed in the Trás-os-Montes region of northern Portugal. Peak conditions attained during blueschist facies metamorphism are estimated to have been c. 420° C and 〉11 kbar. Porphyroblastic white mica (paragonite/phengite) within the blueschist assemblage records a 36Ar/40Ar versus 39Ar/40Ar isotope correlation age of 329.4 ± 1.6 Ma. In view of the relatively low-T nature of the metamorphism, the c. 330-Ma age is interpreted to date closely the high-P recrystallization. This tectonothermal activity is interpreted to have resulted from structural emplacement of a previously assembled crystalline nappe complex (‘Upper Allochthon/Ophiolite Nappe’) onto Iberian protoliths of the Lower Allochthon during terminal stages of the Hercynian orogeny.

Notizen: Abstract Standard petrographic, microthermometric and Raman spectroscopic analyses of fluid inclusions from the metamorphosed massive sulphide deposits at Ducktown, Tennessee, indicate that fluids with a wide range of compositions in the C–O–H–N–S–salt system were involved in the syn- to post-metamorphic history of these deposits. Primary fluid inclusions from peak metamorphic clinopyroxene contain low-salinity, H2O–CH4 fluids and calcite, quartz and pyrrhotite daughter crystals. Many of these inclusions exhibit morphologies resembling those produced in laboratory experiments in which confining pressures significantly exceed the internal pressures of the inclusions. Secondary inclusions in metamorphic quartz from veins, pods, and host matrix record a complex uplift history involving a variety of fluids in the C–O–H–N–salt system. Early fluids were generated by local devolatilization reactions while later fluids were derived externally.Isochores calculated for secondary inclusions in addition to the chronology of trapping and morphological features of primary and secondary fluid inclusions suggest an uplift path which was concave toward the temperature axis over the P–T range 6–3 kbar and 550–225° C. Immiscible H2O–CH4–N2–NaCl fluids were trapped under lithostatic to hydrostatic pressure conditions at 3–0.5 kbar and 215 ± 20° C. Entrapment occurred during Alleghanian thrusting, and the fluids may have been derived by tectonically driven expulsion of pore fluids and thermal maturation of organic material in lower-plate sedimentary rocks which are thought to underlie the deposits. Episodic fracturing and concomitant pressure decreases in upper-plate rocks, which host the ore bodies, would have allowed these fluids to move upward and become immiscible. Post-Alleghanian uplift appears to have been temperature-convex.Uplift rates of 0.10–0.05 mm year−1 from middle Ordovician to middle Silurian – late Devonian, and 0.07–0.12 mm year−1 from middle Silurian – late Devonian to late Permian are suggested by our uplift path and available geochronological data.

Notizen: Abstract Metapelites in the Altavista area, southwest Virginia Piedmont, USA, underwent allochemical hydrothermal retrograde metamorphism in synmetamorphic shear zones. The metapelites of the Evington Group were metamorphosed in a prograde sequence of chlorite, staurolite, and sillimanite zones. Garnet–biotite geothermometry and phase relations support eastward increasing metamorphic grade, ranging from 570° C in the staurolite zone to 650° C in the sillimanite zone at c. 5.8 kbar. Sillimanite-zone rocks later underwent progressive retrogression around shear zones which acted as fluid conduits. Retrograde assemblages are successively zoned around the shear zones with staurolite-, chloritoid- and kyanite-bearing assemblages. The shear zones commonly contain kyanite or tourmaline veins. Applicable phase equilibria indicate that retrogression occurred during isobaric cooling through c. 200–270° C. Rock compositional changes with retrogression occurred in steps: SiO2 was gained in the early stages of the retrogression but lost in the late stages; Al2O3, K2O, and H2O were increasingly gained through the sequence; CaO was increasingly lost. Addition of H2O and decreasing temperatures resulted in new ferromagnesian minerals (staurolite, chloritoid, chlorite) and changes in H2O, SiO2, Al2O3, K2O, and CaO contents produced muscovite and sodic plagioclase.Subsequent to prograde metamorphism, deeply derived fluids migrated upwards along shear zones, providing fluid and energy for the retrograde reactions. The sheared rocks underwent fluid infiltration with fluid fluxes of 1.8 × 107–4.3 × 107 cm3/cm2 corresponding to minimum estimated fluid-to-rock ratios of 7.5–21 as a function of position within the shear zone. Fluid flow was from high to low temperature early and low to high temperature later in the retrogression.

Notizen: Abstract Mafic phyllosilicates in metabasites affected by low-grade regional metamorphism from Wales and eastern North Greenland show variations in their structure and chemistry. These variations are related to four mineral zones in these metabasites, which are recognized on the presence/absence of various key calc-silicate minerals and also actinolite. Zones 1 and 2 equate with the zeolite facies, zone 3 with the prehnite–pumpellyite facies (or prehnite–actinolite facies in rocks with appropriate bulk rock composition) and zone 4 with the greenschist facies. Whilst variations in Fe/(Fe + Mg) in chlorite correlate closely with Fe/(Fe + Mg) ratios in the whole-rock, other chemical variations are clearly unrelated to whole-rock compositions. Contents of Aliv are seen to increase systematically in samples from zone 1 through to zone 4, which relate to an increase in temperature. Calibration of alteration temperatures, calculated using the chlorite geothermometer (based on Aliv contents) developed for meta-andesites in the Los Azufres geothermal system (Mexico), against x values (an estimate of the proportion of chlorite to swelling component in the mafic phyllosilicates) shows a decrease in the swelling component in passing from zone 1 to zone 4, i.e. with an increase in temperature. Calculated temperatures compare favourably with published stability estimates for the various key calc-silicates and actinolite. These data indicate that the chlorite geothermometer, although developed for meta-andesites from a hydrothermal system, does show a correlation with temperatures estimated from calc-silicate assemblages in metabasites affected by low-grade metamorphism developed on a regional scale.

Notizen: Abstract Regional metamorphism in the external Variscides of southwest England varied from diagenetic level to greenschist facies. There is a fundamental difference in the metamorphic character between the northern and southern regions of the area. In the north, M1 metamorphism is of a sedimentary burial character associated with high heat flow, whilst to the south it is related to tectonic burial during thrust thickening processes, with lower geothermal gradients. This pattern appears to be related to the character of basin development and its subsequent tectonic evolution. The northern region has features that accord with a diastathermal (extensional) origin for the very low-grade metamorphism whilst in the southern region the very low-grade metamorphism is linked to thrusting as a consequence of Variscan compression. The Tintagel High-Strain Zone presents an anomaly in this regional pattern where an M2 metamorphic phase is attributed to localized D2 thrust stacking along the southern margin of the Culm Basin.There is no extensive overprint of the regional metamorphic pattern by the contact aureoles surrounding the granite plutons of the region. However, there is a noticeable coincidence between the areas of regional epizone grade and the extent of the geophysically defined subsurface limit of the granite batholith (excluding the North Devon area). This link is attributed largely to the late-stage structural up-doming of the higher grade areas over the roof of the batholith.

Notizen: High Temperature Metamorphism and Crustal Anatexis. Edited by J. R. Ashworth & M. Brown. The Mineralogical Society Series The Al2SiO5 Polymorphs. By Derrill M. Kerrick. Reviews in Mineralogy

Notizen: Abstract Evaluation of two commonly used microstructural criteria for determining the origin of inclusions, namely the existence of a host–inclusion orientation relationship and continuity between inclusions and matrix, using two specific examples of inclusions of tschermakite in actinolitic hornblende, shows that these criteria can be difficult to implement and if not applied carefully will give contradictory results. Consequently, it may be difficult to establish the origins of inclusions; petrographic studies should therefore clearly state the criteria used for interpretation of host–inclusion relationships and how these criteria were implemented.

Notizen: Abstract Syn-metamorphic re-imbrication of the internal part of thrust belts can result in distinct pressure–temperature–time–deformation (P–T–t–d) pathways for different structural–metamorphic domains. In the early Proterozoic Cape Smith Thrust Belt (Canada), an external (piggyback-sequence thrusting) domain is characterized by thermal peak metamorphism occurring after deformation. In contrast, thermal peak metamorphism in an internal domain occurred during re-imbrication by out-of-sequence thrusting. The interactions of tectonic and thermal processes have been studied using three methods: (i) qualitative evaluation of the timing between mineral growth and deformation; (ii) analytical P–T paths from growth-zoned garnet porphyroblasts; and (iii) numerical modelling of vertical heat conduction. Derived P–T–t–d pathways suggest that uplift in the external domain resulted in part from erosion and isostatic unloading. In contrast, paths for the internal domain indicate that the out-of-sequence portion of the thrust belt may have experienced faster unroofing relative to the external domain. This is attributed to thickening by out-of-sequence thrusting and possibly to extensional faulting at (now eroded) higher structural levels. Observations on the timing of metamorphism, coupled with numerical modelling, suggest that the thermal peak metamorphism documented in the external domain is a consequence of the emplacement of the out-of-sequence thrusts stack in the internal portion of the thrust belt.

Notizen: Abstract CO2-bearing fluid inclusions in strongly lineated but weakly foliated late Precambrian gneisses within the Hope Valley Shear zone of Connecticut and Rhode Island are of mixed composition (Xco2± 0.1; 7 wt% NaCl equivalent) and variable density (0.59–0.86 g/ml) and occur mainly as isolated inclusions. Also present are dilute (3 wt% NaCl equivalent) aqueous inclusions which occur on healed fractures related to greenschist facies retrograde metamorphism. Isochores for dense isolated CO2-bearing inclusions indicate pressures of 7.5–9 kbar at 500–600° C, the estimated temperature conditions of peak metamorphism. Published 40Ar/39Ar hornblende plateau age spectra indicate cooling through about 500° C at 265 ± 5 Ma. Isochores for low-density CO2-bearing inclusions and aqueous inclusions intersect at the conditions of retrograde metamorphism (325–400° C) and indicate pressures of 3–4 kbar. Published 40Ar/39Ar biotite plateau ages indicate cooling through about 300° C at 250 ± 5 Ma. These data define a P–T uplift curve for the region which is convex towards the temperature axis and indicate uplift rates between 0.4 and 3.3 mm/year in Permian time. Exhumation of basement gneisses was coeval with normal (west-down) motion along the regional basement–cover contact (Honey Hill–Lake Char–Willimantic fault system), and is interpreted as due to post-orogenic extensional collapse of the Alleghanian orogeny.

Notizen: Abstract The Proterozoic low-pressure, high-temperature (LPHT) terrane of the Reynolds Range occurs in a 130-km-long, NW-trending belt in the central part of the Arunta Block, central Australia. The Reynolds Range has been affected by two mid-Proterozoic tectonic cycles, DI and DII, associated with two metamorphic events, MI and MII. DI–MI effects are restricted to the older of two sedimentary successions, the Lander Rock beds, which are separated from the younger Reynolds Range Group by an angular unconformity. The dominant structural–metamorphic features formed during DII–MII affected both sedimentary successions and the various granites that intruded them, and reworked most DI–MI effects. The DII deformation history can be subdivided into one prograde, two peak, and one retrograde stage. Average P–T calculations in the southeastern half of the range indicate a peak-metamorphic pressure of 4.1 ± 0.3 kbar. Because the calculated values are derived from the same stratigraphic level corresponding to the base of the Reynolds Range Group, which is exposed throughout the area, it is likely that pressures were similar in the entire range. In fact, however, the peak-metamorphic temperature shows a dramatic increase from greenschist facies (c. 400° C) in the northwest to granulite facies (740 ± 60° C) in the southeast, indicating that MII was associated with anomalously high heat flows. The P–T path is anticlockwise, with isobaric cooling from the metamorphic peak indicated by corona textures. However, the evidence of a prograde increase in pressure is indirect and based on the compressional nature of the structures. Peak-metamorphic mineral assemblages and retrograde mineral assemblages in amphibolite facies shear zones show the same metamorphic zonation, suggesting they formed in response to the same thermal event. If this is true, the implication is that a thermal perturbation external to the crust was maintained for a considerable period of time (110 Ma, based on zircon dating). As it is not clear whether Proterozoic, asthenosphere-active, thermal perturbations operated for this long, the alternative interpretation must be considered, namely that the peak-metamorphic events are separate from the shear zone event associated with reheating of the area.

Notizen: Abstract Finite difference models of Fe-Mg diffusion in garnet undergoing cooling from metamorphic peak conditions are used to infer the significance of temperatures calculated using garnet-biotite Fe-Mg exchange thermometry. For rocks cooled from high grades where the garnet was initially homogeneous, the calculated temperature (Tcalc) using garnet core and matrix biotite depends on the size of the garnet, the ratio of garnet to biotite in the rock (Vgarnet/Vbiotite) and the cooling rate. For garnets with radii of 1 mm and Vgarnet/Vbiotite〈1, Tcalc is 633, 700 and 777°C for cooling rates of 1, 10 and 100°C/Ma. For Vgarnet/Vbiotite= 1 and 4 and a cooling rate of 10° C/Ma, Tcalc is approximately 660 and 610° C, respectively. Smaller and larger garnets have lower and higher Tcalc, respectively. These results suggest that peak metamorphic temperatures may be reliably attained from rocks crystallized at conditions below Tcalc of the garnet core, provided that Vgarnet/Vbiotite is sufficiently small (〈0.1) and that the composition of the biotite at the metamorphic peak has not been altered during cooling.Numerical experiments on amphibolite facies garnets with nominal peak temperatures of 550–600° C generate a ‘well’in Fe/(Fe + Mg) near the rim during cooling. Maximum calculated temperatures for the assemblage garnet + chlorite + biotite + muscovite + plagioclase + quartz using the Fe/(Fe + Mg) at the bottom of the ‘well’with matrix biotite range from 23–43° C to 5–12° C below the peak metamorphic temperature for cooling rates of 1 and 100° C/Ma, respectively. Maximum calculated temperatures for the assemblage garnet + staurolite + biotite + muscovite + plagioclase + quartz are approximately 70° C below the peak metamorphic temperature and are not strongly dependent on cooling rate. The results of this study indicate that it may be very difficult to calculate peak metamorphic temperatures using garnet-biotite Fe-Mg exchange thermometry on amphibolite facies rocks (Tmax 〉 550° C) because the rim composition of the garnet, which is required to calculate the peak temperature, is that most easily destroyed by diffusion.

Notizen: The tectonic settings for the formation and evolution of regional granulite terranes and the lowermost continental crust can be deduced from pressure–temperature–time (P–T–time) paths and constrained by petrological and geophysical considerations. P–T conditions deduced for regional granulites require transient, average geothermal gradients of greater than 35°C km−1, implying minimum heat flow in excess of 100 mWm−2. Such high heat flow is probably caused by magmatic heating. Tectonic settings wherein such conditions are found include convergent plate margins, continental rifts, hot spots and at the margins of large, deep-seated batholiths. However, particular P–T–time paths do not allow specific tectonic settings to be distinguished at this time. Under different conditions, both clockwise, CW (Pmax attained before Tmax), and anticlockwise, ACW (Pmax attained slightly after Tmax), paths are possible in the same tectonic setting. Both CW and ACW end-member paths can yield nearly isobaric cooling, IBC, paths. Such cooling paths are clearly not an artefact of thermobarometry, but can be constrained by solid–solid and devolatilization equilibria and geophysical modelling.In terms of understanding the evolution of the deep crust, a potentially significant group of regional granulite terranes are those that show evidence for ACW-IBC paths. Such paths are the likely result of: (i) episodic igneous activity resulting in intrusions within all levels of the crust, (ii) thickening of the crust by magmatic underplating, (iii) slow uplift as a result of the formation of a deep, garnet-rich crustal root and (iv) excavation resulting from a later tectonic event unrelated to that resulting in the formation of the granulites. The later event might be triggered by the delamination of the garnet-rich, lowermost crust.

Notizen: Mafic garnet-bearing granulites from Sostrene Island, 150 km southwest of Davis Station on the coast of Prydz Bay, East Antarctica, exhibit two-stage symplectic coronas on garnet, formed after peak metamorphic conditions (M1). An outer corona of Opx (Mg66) + Pl (An94–97) + minor Hbl mantles a finer-grained inner corona of Opx (Mg67) + Pl (An95–96) + Spl (Mg36). Both symplectites contain minor ilmenite–magnetite intergrowths. The finer-grained symplectite also occurs along a fracture cleavage in the garnet.The outer corona originated during a second metamorphic event (M2) via the reaction Grt + Cpx (Hbl) + SiO2= Opx + Pl (1), whereas the inner corona formed later in response to decompression and minor deformation, resulting in the fracture cleavage in the garnet, according to the reaction Grt = Opx + Pl + Spl (2). The grossular content of the garent (XGrs= 0.168) is almost exactly that which is required for the stoichiometric breakdown by reaction (2) (calculated XGrs= 0.167). The mafic rocks are silica undersaturated, and the SiO2 for reaction (1) was most probably derived externally from the surrounding felsic gneisses.Preferred P–T estimates for M1 based on garnet core (Prp40Alm42Grs17Sps1)–matrix Opx–Cpx–Hbl pairs are c. 10 kbar at 980°C. The fine-grained symplectite formed post-peak M2 at c. 7 kbar and 850°C. The enclosing felsic gneisses yield pressure estimates of between 5 and 7 kbar, which compare with conditions of c. 6 kbar and 775°C in the nearby Bolingen Islands. These lower P–T estimates are considered to be representative of the widespread 1100-Ma metamorphic event recognized in outcrops along the Prydz Bay coast. The high-P, high-T estimates derived from the garnet relics provide evidence for an earlier, possibly Archaean, high-grade metamorphic event.

Notizen: Calc-silicate granulites from the Bolingen Islands, Prydz Bay, East Antarctica, exhibit a sequence of reaction textures that have been used to elucidate their retrograde P–T path. The highest temperature recorded in the calc-silicates is represented by the wollastonite- and scapolite-bearing assemblages which yield at least 760°C at 6 kbar based on experimental results. The calc-silicates have partially re-equilibrated at lower temperatures (down to 450°C) as evidenced by the successive reactions: (1) wollastonite + scapolite + calcite = garnet + CO2, (2) wollastonite + CO2= calcite + quartz, (3) wollastonite + plagioclase = garnet + quartz, (4) scapolite = plagioclase + calcite + quartz, (5) garnet + CO2+ H2O = epidote + calcite + quartz, and (6) clinopyroxene + CO2+ H2O = tremolite + calcite + quartz.The reaction sequence observed indicates that aCO2 was relatively low in the wollastonite-bearing rocks during peak metamorphic conditions, and may have been further lowered by local infiltration of H2O from the surrounding migmatitic gneisses on cooling. Fluid activities in the Bolingen calc-silicates were probably locally variable during the granulite facies metamorphism, and large-scale CO2 advection did not occur.A retrograde P–T path, from the sillimanite stability field (c. 760°C at 6 kbar) into the andalusite stability field (c. 450°C at 〈3 kbar), is suggested by the occurrence of secondary andalusite in an adjacent cordierite–sillimanite gneiss in which sillimanite occurs as inclusions in cordierite.

Notizen: Many high-temperature–low-pressure (high-T–low-P) metamorphic terranes show evidence for peak mineral growth during crustal thickening strain increments at pressures near the maximum attained during the heating–cooling cycle. Such terranes are not readily explained as the conductive response to crustal thickening since the resulting Moho temperatures would greatly exceed the crustal liquidus and because heating due to conductive equilibration on length scales appropriate to lithospheric-scale strains must greatly outlast the deformation. Consequently, high-T–low-P metamorphism may be generated during crustal thickening only when significant heat is advected within the crust, as for example may occur during the segregation of granitic melts. We show that without the addition of asthenospheric melts and at strain rates appropriate to continental deformation the conditions required for significant lower crustal melting during deformation are only likely to be attained if heat flow into the lower crust during crustal thickening is increased substantially, for example, by removing the mantle part of the lithosphere. A simple parameterization of lithospheric deformation involving the vertical strain on the scale of the crust, c, and the lithosphere, 1 respectively, allows the potential energy of the evolving orogen to be readily evaluated. Using this parameterization we show that an important isostatic consequence of the deformation geometries capable of generating such high-T–low-P metamorphism during crustal thickening (with c1) is an imposed upper limit to crustal thicknesses which is much lower than for homogeneous deformations (fc= f1) for the same initial lithospheric configuration.

Notizen: ‘Lower crustal’ suite xenoliths in basaltic and kimberlitic magmas are dominated by mafic granulites and may also include eclogites and garnet pyroxenites. Pressures of up to 25 kbar obtained from such xenoliths are well in excess of an upper value of c. 12 kbar for exposed granulite terranes. Palaeogeotherms constructed from xenoliths for the lower crust beneath the Phanerozoic fold belts of eastern Australia (SEA) and beneath the eastern margin of the Australian craton (EMAC) indicate two distinct thermal regimes. The two geotherms have similar form, with the EMAC curve displaced c. 150°C to lower temperatures. Reaction microstructures show the partial re-equilibration of primary igneous assemblages to granulite and eclogite assemblages and are interpreted to reflect the cooling from magmatic temperatures. Variations in mineral compositions and zoning are used to constrain further the history of several EMAC xenoliths to near-isobaric trajectories.Detailed graphical models are constructed to predict compositional changes for isobaric P–T paths (at 7, 14 & 21 kbar) to transform an SEA-type geotherm to a cratonic geotherm. The models show that for the assemblage grt + cpx ± ky + plag + qtz, the changes associated with falling temperature in Xgr, Xjd (increase) and Xan (decrease) will be greater at higher pressures. These results indicate that discernible zoning is more likely to be preserved in the higher pressure xenoliths. The zoning recorded in clinopyroxene from mafic granulite xenoliths over the pressure range c. 12–22 kbar suggests isobaric cooling of a large crustal thickness (30–35 km).An isobaric cooling path is consistent with magma accretion models for the transition of a crust–mantle boundary from an SEA-type geotherm to a cratonic geotherm. The coexistence of granulite and eclogite over the depth range 35–75 km beneath the EMAC indicates that the granulite to eclogite transition in the lower crust is controlled by P–T conditions, bulk chemistry and kinetic factors. At shallower crustal levels, typified by exposed granulite terranes, isobaric cooling may not result in the transition to eclogite.

Notizen: Isocon analysis has been applied to five sets of leucosome, mafic selvages and immediately adjacent mesosome in the migmatites from a 15-m outcrop in the Colorado Front Range. The results show: (i) mafic selvages formed from the adjacent mesosome by loss of felsic components and therefore the mesosomes are indeed palaeosomes or protoliths; (ii) the leucosomes did not form in a closed system from the palaeosome (in which case the material lost from the palaeosome during selvage formation would become the leucosome). The observed volumes and compositions of leucosomes require that the present leucosome must contain some material in addition to the felsic components lost from the selvages. The materials that must be added are leucotonalitic to granitic in composition, varying greatly in K/(Na + Ca) ratio. The trend in leucosome composition can be reproduced by assuming that a metasomatic exchange, KNa + Ca, modified originally leucotonalitic leucosomes to more K-rich compositions. These leucosomes most likely formed by injection of silicate melts accompanied, or followed, by metasomatism. The trend of leucosome compositions in this study reflects the general trend in the leucosome compositions which have been published from other areas, indicating that the proposed mechanism can be applicable to other regional migmatites.

Notizen: Three types of zircon occur in a complexly deformed and variably migmatized quartzofeldspathic gneiss from the Reynolds Range, central Australia. The oldest type is inherited from the granitic precursor of the gneiss, and is overgrown by a second group of zircon grains that formed during prograde, granulite facies metamorphism. Partial melting of the gneiss resulted in solution of both the inherited and metamorphic zircon. No new zircon growth accompanied crystallization of the partial melt, suggesting loss of zirconium–rich residual fluids. Hydrous, amphibolite facies retrogression of the gneiss and its migmatized variants during late shearing produced new, idiomorphic zircon in both the shear zone and its wall rocks.Important implications of this study are that (i) zircon has a tendency to dissolve if it comes into direct contact with a melt produced from anhydrous biotite breakdown in a quartzofeldspathic granulite, (ii) melt crystallization is not necessarily accompanied by zircon growth, and (iii) euhedral zircon can grow from a hydrous fluid phase under subsolidus, amphibolite facies conditions, e.g. within shear zones.

Notizen: The Sesia zone (Italian Western Alps) offers one of the best preserved examples of pre-Alpine basement reactivated, under eclogite facies conditions, during the Alpine orogenesis. A detailed mineralogical study of eclogitized acid and basic granulites, and related amphibolites, is presented. In these rare weak to undeformed rocks microstructural investigations allow three main metamorphic stages to be distinguished.(a) A medium- to low-P granulite stage giving rise to the development of orthopyroxene + garnet + plagioclase + brown amphibole + ilmenite ± biotite in basic granulites and garnet + K-feldspar + plagioclase + cordierite + sillimanite + biotite + ilmenite in acid granulites.(b) A post-granulite re-equilibration, associated with the development of shear zones, producing discrete amphibolitization of the basic granulites and widespread development of biotite + sillimanite + cordierite + spinel in the acid rocks.(c) An eo-Alpine eclogite stage giving rise to the crystallization of high-P and low-T assemblages.In an effort to quantify this evolution, independent well-calibrated thermobarometers were applied to basic and acid rocks. For the granulite event, P-T estimates are 7–9 kbar and 700–800° C, and for subsequent retrograde evolution, P-T was 4–5 kbar and 600° C. For the eo-Alpine eclogite metamorphism, pressure and temperature conditions were 14–16 kbar and 550° C.The inferred P-T path is consistent with an uplift of continental crust produced by crustal thinning prior to the subduction of the continental rocks. In the light of the available geochronological constraints we propose to relate the pre-Alpine granulite and post-granulite retrograde evolution to the Permo-Jurassic extensional regime. The complex granulite-eclogite transition is thus regarded as a record of the opening and of the closure of the Piedmont ocean.

Notizen: Abstract The Sambagawa metamorphic belt exposed in central Shikoku records a high-P–T metamorphic event. It is represented by the Oboke nappe and structurally overlying, internally imbricated, Besshi nappe complex. These major structural units are in ductile thrust contact. A melange is developed along a ductile internal tectonic contact within the Besshi nappe complex. Tectonic emplacement of a high-T enclave (Sebadani eclogite) in the melange zone resulted in the development of a contact metamorphic aureole within the host Sambagawa rocks. 36Ar/40Ar versus 39Ar/40Ar isotope correlation ages recorded by hornblende from the Sambagawa basic schists which surround the Sebadani enclave are 83.4 ± 0.3 Ma (within contact aureole) and 83.6 ± 0.5 Ma (outside aureole). 40Ar/39Ar plateau ages recorded by muscovite from the same samples are 87.9 ± 0.3 and 89.3 ± 0.4 Ma. Amphibole from the amphibolite within the Sebadani enclave records isotope correlation ages of 93.7 ± 1.1 and 96.5 ± 0.7 Ma (massive interior) and 84.6 ± 1.2 Ma (marginal shear zone). Amphibole within the massive amphibolite is significantly higher in XMg than that within the host Sambagawa basic schists. The older ages recorded by amphibole within the Sebadani enclave are interpreted to date cooling through somewhat higher closure temperatures than which characterize the more Fe-rich amphibole in surrounding schists. The younger amphibole age recorded within the marginal shear zone probably indicates that crystallization of amphibole continued until cooling through the relatively lower amphibole closure temperatures.These results, together with the previously published 40Ar/39Ar ages of the Sambagawa schists, suggest: (i) metamorphic culmination occurred in the Besshi nappe complex at c. 100–90 Ma; (ii) at c. 95 Ma the Besshi nappe complex was internally imbricated and tectonic enclaves were emplaced; (iii) at c. 85 Ma, the composite Besshi nappe was rapidly exhumed and tectonically emplaced over the Oboke nappe (which attained peak metamorphic conditions at c. 75 Ma); (iv) the Besshi and Oboke nappe complexes were further exhumed as a coherent tectonic unit and unconformably overlain by the Eocene Kuma Group at c. 50 Ma.

Notizen: Abstract Textural ‘unconformities’or truncations are common in porphyroblasts with complex inclusion trails. They reflect cycles of successive foliations that develop against competent porphyroblasts during orogenesis and are preserved by successive growth increments. Their truncational character results from shear and dissolution along a particular foliation generating a differentiated crenulation cleavage. The increment of porphyroblast growth that follows a textural ‘unconformity’may or may not mark a significant compositional change, depending on the amount of movement of the rock through P–T space between cleavage-forming events.Although historically interpreted to result from a significant metamorphic hiatus, most textural unconformities indicate that the reactions involved in the formation of these minerals are episodic during continuous prograde metamorphism, starting and stopping as a function of the stage of crenulation of the matrix foliation and the pattern of deformation partitioning. Such episodic reaction behaviour can only occur for multivariant reactions, or successive but different univariant reactions. The reason why garnet is the most common porphyroblast to exhibit evidence for episodic reactions is probably the fact that it grows by multivariant reactions over a much wider P–T range than most other common porphyroblast phases.Porphyroblast growth is micrometasomatic. It is episodic because a significant reduction of strain occurs within domains of progressive shortening each time continuous progressive shearing domains form on their margins. This stops microfracture development across the progressive shortening domains, thereby preventing rapid access and interaction of fluid, ions and complexes with porphyroblast boundaries. Shifting patterns of deformation partitioning and resulting small-scale juxtaposition of different compositional layers spreads the duration and location of multivariant reactions and causes differential timing of porphyroblast growth along a particular stratigraphic horizon. It may also locally preserve metastable metamorphic assemblages.In regionally metamorphosing/deforming pelites, near-simultaneous cessation of porphyroblast growth on all rims, once continuous differentiated progressive shearing domains have formed nearby, precludes fluid recirculation as a significant process for removal of material during cleavage development. Alternatively, diffusion of simple molecules and dissociated ions along actively shearing and micro-gaped phyllosilicates, with recomplexing in fluid-filled microfractures, readily explains the control of deformation partitioning on reaction site and reaction duration.

Notizen: Abstract The microstructure of quartz in metacherts of the Ryoke metamorphic belt in central Japan develops from polygonal, through duplex to irregular with increasing metamorphic grade. The polygonal microstructure is composed of small (mostly 90–160 μm), equant, equigranular, polygonal quartz grains, whereas the irregular microstructure is characterized by large (〉300 μm) grains with irregular grain boundaries. The duplex microstructure is a mixture of small polygonal and large irregular grains. The development of these microstructures is interpreted as being due to secondary recrystallization. The size of polygonal grains is greatly influenced by the presence of second-phase minerals, such as mica, whereas that of large irregular grains is unaffected by second-phase minerals. There seems to be a critical grain size for quartz to occur as polygonal aggregates: no polygonal aggregates occur in rocks with larger than the critical grain size. The size (about 140 μm) decreases slightly with increasing volume fraction of mica. The mean grain sizes of polygonal quartz (D) and coexisting mica (d) in the duplex microstructure are systematically related to the volume fraction of mica (f) by D= 0.728d(1/f)0.629.

Notizen: Abstract The Shyok Suture Zone separates rocks in the Asian plate from rocks in the Kohistan-Ladakh island arc. In Baltistan, this suture has been reactivated by the late ‘break-back’Main Karakorum Thrust (MKT). The P-T histories of metamorphic rocks both north and south of the MKT have been determined in an effort to place constraints on the tectonic history of this zone. The terranes north and south of the MKT have different, unrelated metamorphic histories. Rocks from the Kohistan-Ladakh island arc south of the MKT have undergone a static low-P (2–4 kbar, c. 500° C) thermal metamorphism. The P-T paths and metamorphic textures of these rocks are consistent with metamorphism due to emplacement of plutonic rocks into the island arc. This metamorphism pre-dates folding and deformation of these rocks. Rocks in the Karakorum Metamorphic Complex, north of the MKT, have experienced a complex deformational and metamorphic history. Prograde metamorphic isograds have been deformed by subsequent south-verging folding and by gneiss dome emplacement. However, decompression metamorphic reactions occurred during nappe emplacement. Higher pressure rocks are associated with higher level nappes, creating an inverted pressure metamorphic sequence (8–9-kbar rocks over 5–6-kbar rocks). There is little variation in temperature with structural level (550–625° C). These two different terranes have been juxtaposed after metamorphism by the late south-directed MKT.

Notizen: Abstract Ductile shearing in the core of the Tauern Window, Austria, transformed metagranodiorite into Si-undersaturated garnet-chlorite-staurolite schist at a depth of c. 35–40 km during the Alpine orogeny. Four distinct zones have been recognized extending from the wallrock into the centre of the shear zone: Zone I—unaltered metagranodiorite with subordinate amphibolite; Zone II—biotite-white mica-garnet schist; Zone III—biotite-phengite schist; Zone IV—quartz-absent, garnet-chlorite-staurolite schist with garnets up to 10 cm across. Whole-rock analyses show a dramatic decrease in SiO2 from 〉65 wt% in Zone I to 〈35 wt% in Zone IV; Ca, Na, and Sr also decrease across the shear zone, whereas Al, Ti, Fe, Mg, P, Cr, Ni, Zn, and Rb all increase towards Zone IV. Mass-balance calculations indicate that shearing was accompanied by up to 60% volume loss near the centre of the shear zone. Comparison of the Tauern Window samples with other shear zones in granitic hosts indicates that silica loss accompanied by gains in Mg, Fe, and Ti is typical for volume-loss shear zones, but is distinctly different from the element behaviour exhibited in shear zones that are thought to represent approximately isovolumetric behaviour. In the samples studied here, volume loss appears to have resulted from channellized fluid flow during shearing, producing time-integrated fluid fluxes of ± 108 cm3 cm−2 in Zone IV. This large volume of fluid may have originated, in part, from dehydration of flysch carried beneath the metagranodiorites during Eocene movement on the North Penninic subduction zone. Development of an inverted thermal gradient during subduction would have allowed the fluid to scavenge large amounts of silica from the shear zone during ascent and heating.

Notizen: Abstract High-P granulites contained in two allochthonous tectonic units were thrust southwards onto the northern margin of the Zimbabwe craton during the Pan-African Zambezi orogeny. In the lower sheet, the Masoso Metamorphic Suite contains mafic garnet granulite assemblages formed during a high-P-T metamorphic event, although the suite as a whole is predominantly granitic. The garnet granulites occur as relicts within narrow mafic layers characterized by migmatitic and mylonitic fabrics. The annealed mylonites represent surfaces of deep-crustal tectonic imbrication that formed immediately before the Pan-African orogeny. Gabbros which intruded the granulites after the main phase of migmatization have formed corona textures that document a low-P-T metamorphic event at mid-crustal levels. The style of deformation then changed and the Masoso Suite with its mylonitic layers was folded and thrusted southwards onto the Archaean Zimbabwe craton.

Notizen: Petrology of the Metamorphic Rocks, 2nd Edn. By R. Mason. Unwin HymanAtlas of Metamorphic Rocks and their Textures. By B. W. D. Yardley, W. S. Mackenzie and C. Guilford.

Notizen: Abstract We have used internally-consistent thermodynamic data to present calculated phase equilibria for the system Na2O-CaO-MgO-Al2O3-SiO2-H2O (NCMASH), in the range 0–500° C and 0.1–10 kbar, involving the phases anorthite, glaucophane, grossular, heulandite, jadeite, laumontite, lawsonite, paragonite, prehnite, pumpellyite, stilbite, tremolite, wairakite, zoisite with excess albite, clinochlore, quartz and pure water. Average activity terms derived from published mineral chemical data were included for clinochlore, glaucophane, prehnite, pumpellyite, tremolite, and zoisite. The new petrogenetic grid delineates stability fields and parageneses of common index minerals in zeolite, prehniteactinolite, prehnite-pumpellyite, pumpellyite-actinolite, blueschist and greenschist facies metabasites. The stability fields of mineral assemblages containing prehnite, pumpellyite, epidote, actinolite (+ albite + chlorite + quartz) were analysed in some detail, using activity data calculated from five specific samples. For example, the prehnite-actinolite facies covers a P-T field ranging from about 220 to 320° C at pressures below 4.5 kbar. The transition from the prehnite-actinolite and pumpellyite-actinolite to greenschist facies occurs at about 250–300° C at 1–3 kbar and at about 250–350° C at 3–8 kbar. P-T fields of individual facies overlap considerably due to variations in chemical composition.

Notizen: An inescapable consequence of the metamorphism of greenstone belt sequences is the release of a large volume of metamorphic fluid of low salinity with chemical characteristics controlled by the mineral assemblages involved in the devolatilization reactions. For mafic and ultramafic sequences, the composition of fluids released at upper greenschist to lower amphibolite facies conditions for the necessary relatively hot geotherm corresponds to those inferred for greenstone gold deposits (XCO2= 0.2–0.3). This result follows from the calculation of mineral equilibria in the model system CaO–MgO–FeO–Al2O3–SiO2–H2O–CO2, using a new, expanded, internally consistent dataset.Greenstone metamorphism cannot have involved much crustal over-thickening, because very shallow levels of greenstone belts are preserved. Such orogeny can be accounted for if compressive deformation of the crust is accompanied by thinning of the mantle lithosphere. In this case, the observed metamorphism, which was contemporaneous with deformation, is of the low-P high-T type. For this type of metamorphism, the metamorphic peak should have occurred earlier at deeper levels in the crust; i.e. the piezothermal array should be of the ‘deeper-earlier’type. However, at shallow crustal levels, the piezothermal array is likely to have been of ‘deeper-later’type, as a consequence of erosion. Thus, while the lower crust reached maximum temperatures, and partially melted to produce the observed granites, mid-crustal levels were releasing fluids prograde into shallow crustal levels that were already retrograde. We propose that these fluids are responsible for the gold mineralization. Thus, the contemporaneity of igneous activity and gold mineralization is a natural consequence of the thermal evolution, and does not mean that the mineralization has to be a consequence of igneous processes.Upward migration of metamorphic fluid, via appropriate structurally controlled pathways, will bring the fluid into contact with mineral assemblages that have equilibrated with a fluid with significantly lower XCO2. These assemblages are therefore grossly out of equilibrium with the fluid. In the case of infiltrated metabasic rocks, intense carbonation and sulphidation is predicted. If, as seems reasonable, gold is mobilized by the fluid generated by devolatilization, then the combination of processes proposed, most of which are an inevitable consequence of the metamorphism, leads to the formation of greenstone gold deposits predominantly from metamorphic fluids.

Notizen: An inverted metamorphic gradient is preserved in the western metamorphic belt near Juneau, Alaska. The western metamorphic belt is part of the Coast plutonic–metamorphic complex of western Canada and southeastern Alaska that developed as a result of tectonic overlap and/or compressional thickening of crustal rocks during collision of the Alexander and Stikine terranes. Detailed mapping of pelitic single-mineral isograds, systematic changes in mineral assemblages, and silicate geothermometry indicate that thermal peak metamorphic conditions increase structurally upward over a distance of about 8 km. Peak temperatures of metamorphism increase progressively from about 530 °C for the garnet zone to about 705 °C for the upper kyanite–biotite zone. Silicate geobarometry suggests that the thermal peak metamorphism occurred under pressures of 9–11 kbar. The metamorphic isograds are in general parallel to the tonalite sill that is regionally continuous along the east side of the western metamorphic belt, although truncation of the isograds north of Juneau indicates that the sill intrusion continued after the isograds were established. Our preferred interpretation of the cause of the inverted gradient is that it formed during compression of a thickened wedge of relatively wet and cool rocks in response to heat flow associated with the formation and emplacement of the tonalite sill magma. Garnet rim compositions and widespread growth of chlorite suggest partial re-equilibration of the schists under pressures of 5–6 kbar during uplift in response to final emplacement and crystallization of the tonalite sill. The combined results of this study with previous studies elsewhere in the western metamorphic belt indicate that high-T/high-P metamorphism associated with the collision of the Alexander and Stikine terranes was a long-lived event, extending from about 98 Ma to about 67 Ma.

Notizen: Phase relationships in the model mafic system and geothermobarometry allow discrimination of four main groups of high-P rocks in the nappes of the Western Alps: very high-P eclogite-facies (including kyanite eclogites and coesite-pyrope assemblages), eclogite-facies (paragonite-zoisite eclogites), high-T blueschist-facies (glaucophane-garnet ± lawsonite assemblages) and low-T blueschist-facies (glaucophane-lawsonite ± pumpellyite assemblages). The blueschist-facies-eclogite-facies transition is promoted chiefly by increasing T, low bulk XMg and relatively low μH2O. The variety of assemblages and the heterogeneous approach to equilibrium observed in the Alpine rocks are not only constrained by the intersection of the reaction surfaces in P-T-X space, but also by the effect and timing of the processes which control kinetics (i.e. pervasive deformation and fluid infiltration). The faster rate of dehydration reactions relative to hydration reactions along with the fact that different bulk compositions crossed the reaction curves at different temperatures (and times), all may have induced μH2O gradients and contributed to the heterogeneous distribution of deformation through a process of reaction-enhanced ductility. Also mass-transfer may have been an effective process in determining the type of high-P assemblage in particular rock volumes.As regards the P-T-t paths, only the post-climax histories are recorded well in the Alpine nappes. Post-eclogitic exhumation paths at decreasing temperatures characterize structurally higher nappes which were first subducted during the early-Alpine (Cretaceous) event. In contrast, more or less isothermal decompression paths characterize structurally deeper nappes formed by westward propagation of the underthrust surfaces during the early-Alpine event and the subsequent meso-Alpine (Palaeogene) collision between the ‘European’and ‘African’plates. In the Western Alps, prevalent eclogite-facies conditions were attained during the metamorphic climax of the early-Alpine subduction, while blueschist-facies recrystallization characterizes the early-Alpine exhumation of the eclogitized units and the subsequent intracontinental underthrusts linked to the meso-Alpine continental collision.

Notizen: The broad requirements of the geomorphologist for original mapping are reviewed. The extent to which aerial photogrammetry can meet these requirements is exemplified through typical approaches and mapping products in fluvial, coastal and glacial specialisms.

Notizen: As part of the measurements of desert terrain characteristics in the United Arab Emirates, made in support of a study of airborne radar, close range vertical stereophotographs of various natural surfaces were taken with a pair of Hasselblad MK70 metric cameras. The technique is described and the constraints imposed by the ground conditions and the need for rapid measurements are explained. Various terrain types are illustrated and the method is described whereby variables summarising surface roughness and surface slope were generated from profiles of the microrelief. From a more general discussion of current equipment and geomorphological applications of close range photogrammetry, it is concluded that this flexible technique is presently under utilised by field scientists.

Notizen: The French topographic database is a three dimensional database whose content is very near to that of the IGN 1:25 000 scale maps. It has a metric accuracy and is designed to have three aims (maps at scales of 1:25 000 and 1:50 000 and the topographic part of the cadastral map at 1:5000 scale, providing located structured data). The structure, including topology information, is described. The process of data capture is based on photogrammetry and field completion. Experiments concerned with revision are being made in order to define the methodology precisely.

Notizen: A mathematical model for pass processing of SPOT imagery is formulated. It is based on the fact that during one pass, the image data stream from each of the instruments in SPOT forms one single very long image. The geometry of this extended image can thus be rectified with as few control points as for only one scene if orbital constraints and attitude measurements are properly taken into consideration. SPOT imagery is, however, not available as this single long image, but only sectioned into scenes. This creates problems which are accounted for in the solution. The possibility of gaps in the sequence of scenes is also taken into consideration. Extrapolation over gaps is of special interest and, by investigating attitude variability, it is shown that extrapolation is successful over multiple scene gaps which is also verified in a real data test.

Notizen: Inner constraints, generalised matrix inverses and S-transformations are described in relation to least squares estimation of spatial positions. A simple example is used to illustrate some of the theory. The various roles and properties of covariance functions and matrices are presented with a discussion of their practical determination and use in least squares interpolation and collocation.

Notizen: Longer sequences of attitude data for SPOT 1 were constructed by concatenation of the attitude information in several consecutive scenes in selected orbits. The attitude time series were used to estimate models for the attitude variogram functions. Explicit expressions for these models are given, which can be used in multi-scene adjustment of SPOT imagery.

Notizen: Interior orientation (the initial step in comparator-based photogrammetry) requires a set of known photo co-ordinates to act as reference points. Fiducials serve this purpose on large format, metric cameras, as do réseau targets on small format, semi-metric cameras. Most small format cameras, however, have neither fiducials nor a réseau plate. The aim of this study was to establish fiducials in a small standard camera (Pentax 645) so that its imagery could be used for photogrammetric computations. This paper describes two methods of establishing fiducials, followed by a comparison of their stability and suitability for photogrammetric purposes.

Notizen: Book review in this aricle:MAPPING AND SPATIAL MODELLING FOR NAVIGATION. Edited by L. F. PauINTRODUCTORY READINGS IN GEOGRAPHIC INFORMATION SYSTEMS. Edited by D. J. Peuquet and D. F. Marble.CAD-KARTOGRAPHIE: ANWENDUNGEN IN DER PRAXIS. Edited by M. Schilcher.INTERPRETING SPACE: GIS AND ARCHAEOLOGY. Edited by K. M. S. Allen, S. W. Green and E. B. W. Zubrow.AN ILLUSTRATED HISTORY OF THE RAF (BATTLE OF BRITAIN 50TH COMMEMORATIVE EDITION). By R. C. Nesbitt.RADAR EVALUATION HANDBOOK. By D. K. Barton, C. E. Cook, P. Hamilton (editors) and staff of ARNO Engineering, Inc.GEOGRAPHIC INFORMATION SYSTEMS: DEVELOPMENTS AND APPLICATIONS. Edited by L. Worrall.BAYESIAN INFERENCE WITH GEODETIC APPLICATIONS. By K.-R. Koch.3D IMAGING IN MEDICINE: ALGORITHMS, SYSTEMS, APPLICATIONS. Edited b K. H. Höhne, H. Fuchs and S. M. PizerREMOTE SENSING YEARBOOK 1990. Edited by A. P. Cracknell, L. W. B. Hayes and H. Wei Gen.GEOLOGICAL MAPS AND SECTIONS FOR CIVIL ENGINEERS. By P. R. Thomas.THE FIGURE OF THE EARTH: THEORETICAL GEODESY AND THE EARTH'S INTERIOR. By H. Moritz.THE ARCHITECTURE OF PETRA. British Academy Monographs in Archaeology I. By J. S. McKenzie.SOUND UNDERWATER IMAGES: A GUIDE TO THE GENERATON AND INTERPRETATION OF SIDE SCAN SONAR DATA. By J. P. Fish and H. A. Carr.

Notizen: This paper was presented at the 1990 Thompson Symposium. It distinguishes between geographical information systems (GIS) as a set of hardware and software tools and the institutional problems that arise when implementing GIS in an organisational environment. It examines issues such as data quality, that arise when treating information as a corporate resource, as well as the legal, economic and social constraints on the use of data.

Notizen: A case study at the Norwegian Institute of Land Inventory (NIJOS) demonstrates that photogrammetry is an effective method for collecting data for geographical information systems (GIS). The process of establishing a photogrammetric data capture system is explained with special attention devoted to financial and personnel considerations. It is argued that photogrammetric data capture is viable provided that a stereodigitiser is used in conjunction with a modular solution GIS.

Notizen: Many organisations are today working at establishing information systems and quite a few exist already. When it comes to geographical information systems (GIS), the geographical reference will soon be solved. All new mapping in Denmark is digital and in 1992–93 the country will have complete coverage. In addition, many public registers are already computerised. A lot of other information sources, like utility networks, are still to be converted.As these developments are in the hands of many different organisations, both private and governmental, this paper will deal with the efforts made to co-ordinate various activities in a strongly competitive world.As there is a distinct difference between large scale and small scale GIS activities, this paper will deal mainly with large scale GIS, as should be the case when considering GIS and photogrammetry.

Notizen: Co-ordinate measuring systems based on theodolites are increasingly being found in industrial environments. The paper explains the principles on which the technique is based, the system components and the factors which affect the accuracy that can be achieved. Finally some application areas are listed and a particular example from the aircraft industry is highlighted.

Notizen: The evolution of digital photogrammetry from analytical photogrammetry is outlined, partly by considering the methods employed, but with the main emphasis on mathematical and physical principles. A fundamental distinction is obvious from the nature of the primary information measurement data: the image co-ordinates with analytical photogrammetry and the digital image grey values with digital photogrammetry. For both techniques, appropriate Gauss-Markov evaluation procedures are compared. The relevant relationships between image space data and object space models are presented; radiometric considerations play a more important role than before. The evaluation of digital image grey value data is no longer based on digital image correlation. Instead, a new principle of image inversion has been introduced by directly back-projecting grey values of an image on to object space models. The numerical procedures of digital photogrammetry need some stabilisation by appropriate regularisation elements. The new concept of digital photogrammetry may be applied to imagery from almost any sensor.

Notizen: Book review in this aticle:THEORY AND APPLICATIONS OF OPTICAL REMOTE SENSING. Edited by G. ASRAR.TERRAIN MODELLING IN SURVEYING AND CIVIL ENGINEERING. Edited by G. Petrie and T. J. M. Kennie.THE FOUR FACES OF FOURCADE. By C. D. Storrar.WALES FROM THE AIR. Photographs by Aerofilms. Foreword by J. Morris. Captions by S. Acland.DEVELOPMENTS IN FOUR-DIMENSIONAL GEODESY. Selected papers of the Ron S. Mather Symposium on Four-Dimensional Geodesy, Sydney, Australia, March 28–31, 1989. Edited by F. K. Brunner and C. Rlzos.EUROPEAN SPACE DIRECTORY 1990. Fifth edition. Sponsored by Eurospace. Edited by D. Shjrvanian.REMOTE SENSING OF BIOSPHERE FUNCTIONING. Edited by R. J. Hobbs and H. A. Mooney.IMAGE CLARITY: HIGH-RESOLUTION PHOTOGRAPHY. By J. B. Williams.MAP PROJECTIONS: THEORY AND APPLICATIONS. By F. Pearson.KARTENNETZENTWURFSLEHRE: GRUNDLAGEN UND ANWENDUNGEN. By E. Kuntz.THE LIFE OF A PHOTOGRAPH. By L. E. Keefe and D. Inch.SUBMINIATURE PHOTOGRAPHY. By W. White.THE ASSOCIATION FOR GEOGRAPHIC INFORMATION YEARBOOK 1990. Edited by M. J. Foster and P. J. Shand.A GUIDE TO REMOTE SENSING: INTERPRETING IMAGES OF THE EARTH. By S. A. Drury.TASCHENBUCH ZUR FERNERKUNDUNG. Edited by F.-W. Strathmann.

Notizen: A method for axenic cultivation of epimastigote and metacyclic forms of Trypanosoma (Duttonella) vivax at 27°C in vitro is described. Iscove's medium was supplemented with specific concentrations of foetal bovine serum, L-proline, L-glutamine, hypoxanthine, adenosine, pyruvate, and 2-mercaptoethanol. Bloodstream form parasites rapidly transformed into epimastigote forms that grew as surface-adherent colonies in plastic culture flasks. Transformation of epimastigotes to metacyclic forms was first observed 9–12 days after initiation of cultures. Percentages of metacyclics varied: East African T. vivax ranged up to 40% and West African T. vivax ranged up to 24%. Subcultures were made at two-week intervals and maintained for several months. Transformation of bloodstream forms to epimastigotes depended on initial attachment to the bottom of culture flasks and the presence of L-proline. The number and maturity of metacyclic forms was influenced by the concentrations of foetal bovine serum, L-proline, L-glutamine, and 2-mercaptoethanol. Trypanosomes from cultures were cryopreserved, revived, and used to re-establish fresh axenic cultures. These results represent a significant advance in cultivation of T. vivax insect forms that should enable studies to be accomplished on metabolism, differentiation, and pharmacology of this parasitic protozoan, free from the influence of extraneous cells.

Notizen: We previously reported that phospholipase increases host cell penetration by Toxoplasma gondii. Here we show that calcium-dependent phospholipase A (PLA) activity is found in the supernatant of sonically disrupted T. gondii. When fractions of disrupted T. gondii were incubated with host cells, the release of fatty acids and lysolipids was detected. Fractions of sonically disrupted T. gondii with PLA activity increased T. gondii host cell penetration in a bioassay. In addition, a protein of approximately 20 kDa was detected by immunoblot of T. gondii antigens with horse antiserum to snake venom, the major antibody of which recognizes PLA2. Incubation of T. gondii with exogenous PLA2 resulted in increased solubility of a rhoptry protein. This protein, which we previously characterized as involved with enhanced parasite invasion of host cells and which is recognized by monoclonal antibody Tg49, was detected in increased amounts in supernatant fractions of extracellular parasites treated with PLA2. Whereas without PLA2 treatment, it is only slightly soluble under physiological conditions. This raises the possibility that PLA may be implicated in the release of rhoptry proteins.

Notizen: Riboflavin deficiency inhibits the growth of malaria parasites both in vitro and in vivo in infected animals and humans. Although the precise mechanisms underlying this inhibition are unknown, they may involve enhanced requirements for riboflavin by parasites. To investigate this possibility, the rate of uptake of [14C]riboflavin and the biosynthesis of FMN and FAD from riboflavin were studied in infected (5–8% parasitemia) and uninfected human erythrocytes. All cells were incubated for 0–3 h at 37° C in phosphate buffered saline containing MgCl2, glucose, and [14C]riboflavin (2.5–7.5 μM). At hourly intervals, samples were removed, centrifuged, washed twice with cold buffer, and lysed before counting the radioactivity. The rate of in vitro biosynthesis of FMN and FAD from riboflavin in erythrocytes was measured by ion exchange chromatography and reverse isotope dilution techniques. Results showed that the rate of riboflavin uptake and the biosynthesis of FMN and FAD were enhanced in erythrocytes with parasitemia as compared with results in unparasitized erythrocytes. Riboflavin uptake in erythrocytes was proportional to the extent of parasitemia and especially to percent of schizonts present in erythrocytes. These studies indicate that the requirement for riboflavin may be greater in the parasite than in the host erythrocyte. This increased riboflavin requirement may be due to rapid multiplication, higher metabolic rate, and extreme vulnerability to oxidative stress of malaria parasites compared with that of host erythrocytes. The differential requirement of riboflavin by the host and the malaria parasite may hold important potential for developing new strategies for malaria chemotherapy.

Notizen: The complete small subunit rRNA gene sequences of the heterotrich Blepharisma americanum and the colpodid Colpoda inflata were determined to be 1719 and 1786 nucleotides respectively. the phylogeny produced by comparisons with other ciliates indicated that C. inflata is allied more closely with the nassophoreans and oligohymenophoreans than the spirotrichs. This is consistent with the placement of the colpodids in the Class Copodea. Blepharisma americanum was not grouped with the hypotrichs but instead was placed as the earliest branching ciliate. the distinct separation of B. americanum supports the elevation to class status given the heterotrichs based on morphological characters.

Notizen: Endosymbiotic methanogenic bacteria of three species of anaerobic ciliates (Plagiopyla frontata, Metopus conforms, and M. palaeformis) were inactivated with the specific methanogen inhibitor 2-bromoethanesulfonic acid. the absence of endosymbiont methanogens reduced growth rate and growth yield by about 30% in P. frontata and M. contortus, while no significant change in fitness was observed in M. palaeformis. In Plagiopyla the growth rate constant is not affected by an artificially increased pH2 neither in normal nor in methanogen-free ciliates. the energetic advantage conferred by endosymbiont methanogens in Plagiopyla and in Metopus contortus probably is due to excretion of organic material from the bacteria at the expense of bacterial reproduction. It is unlikely that the maintenance of a low pH2 within the cells due to H2-consumption by the bacteria is important to the ciliates.

Notizen: Feces from a juvenile specimen of the anteater Tamandua tetradactyla from Ponta de Pedras, Marajó, Pará, northern Brazil, contained three different coccidial oocysts: Eimeria tamanduae Lainson, 1968; E. corticulata Lainson & Shaw, 1990; and a third species previously unrecorded and described here as Eimeria marajoensis n. sp. Oocysts of the latter parasite are spherical to subspherical, 13.9 ± 1.5 times 13.4 ± 1.4 (11.1-16.5 times 11.1-16.5) μm, shape index (length/width) 1.0 (1.0-1.2). the oocyst wall is a single, Colorless layer about 0.6-1.0 μm thick with no striations or micropyle. There is no oocyst residuum, but a single, round, oval or irregularly shaped polar granule of about 0.75-2.5 μm is consistently present. the sporocysts are broadly ellipsoidal, 7.1 ± 0.7 ± 5.3 ± 0.6 (6.0-8.8 times 4.0-5.7) μm, shape index 1.3 (1.2-1.5), with a delicate wall bearing a minute stieda body. No sub-stieda body was visible. the sporocyst residuum consists of some 10-20 rounded granules, lying between the two slightly curved sporozoites which measure approximately 6.5 times 2.0 μm. Sporocyst refractile bodies were not discernablc.

Notizen: Exoerythrocytic forms of Plasmodium gallinaceum were cultured in vitro using salivary gland sporozoites extracted from experimentally infected Aedes fluviatilis mosquitoes. the host cells were macrophage precursors from chicken bone marrow. At various times after introduction of Sporozoites, the cultures were stained by Giemsa or by immunofluorescence assay (IFA) using anti-sporozoite-specific monoclonal antibodies (MAb). the time to complete parasite development in vitro was 50-70 h. By 70 h, ruptured segmenters and free merozoites were visible within the cells. Inoculation of normal chickens with infected cultures induced parasitemia after a pre-patent period of 10-11 days. In vitro young exoerythrocytic forms, late schizonts that include the matured segmenters, and free merozoites shared common antigens with the sporozoites as revealed by IFA using anti-sporozoite-specific MAbs. Our data indicate that macrophages support development of P. gallinaceum sporozoites and that the circumsporozoite proteins are present until Ac end of the primary exoerythrocytic schizogony.

Notizen: This past-presidential address considers the relationship between small-scale assembly and large-scale patterning in ciliates. Certain model examples of assembly-based patterning are reviewed, followed by the introduction of Williams and Honts' concept of “meta-assembly” as applied to the development of the oral apparatus. The major part of this review then explores two topics: the nature and origin of large-scale circumferential order, and the manner by which the large-scale order of cell directions influences the organization of membranelles of the oral apparatus. In this review, I summarize an existing formal description of large-scale positional order, allude to a more precise abstract theoretical model, and end with a brief discussion of the problem of searching for molecular mechanisms.

Notizen: Ellobiophrya conviva clasps tentacles of the bryozoan Bugula neritina with a ring-like structure formed from aboral extensions of its body that taper into two slender arms. The tips of the arms overlap and join to form a unique organelle, the bouton. Each arm contains a massive myoneme that splays out at the bouton. The bouton consists of the cupped tips of the arms and a cavity, which is filled with dense homogeneous material. Long digitations containing longitudinal microtubules at their periphery project from the inner surface of the tip of each arm into the cavity. Deep folds of pellicle with pores opening into their depths line the wall of the cavity. Conventional kinetosomes are not visible in the bouton, but circular or elliptical arrays of microtubules are found at the bases of digitations. The nonfunctional scopula of the adult is in a depression enclosed by pellicular folds. The bouton is distant from the scopula, but its fine structure somewhat resembles it, supporting Chatton and Lwoff's hypothesis that the cinctal arms carry parts of the scopula at their tips. The fine structure of the cinctum supports their suggestion that the cinctal arms are homologous to the spasmonemes of vorticellid peritrichs.

Notizen: Twenty monoclonal antibodies were produced against trophozoites of Entamoeba histolytica strains HK-9 and HM-1: IMSS. When reactivity to various enteric protozoa was examined by an indirect fluorescence antibody test, 15 of the monoclonal antibodies were strongly reactive with E. histolytica trophozoites. Species-specific antigens recognized by these monoclonal antibodies were located on the plasma membrane, nucleus, cytoplasm, and cytoskeletal structures of the trophozoites. Two of the remaining five monoclonals reacted strongly with trophozoites of the E. histolytica-like Laredo strain. The determinant antigen was located in the cytoplasm. The three remaining monoclonal antibodies were found to recognize cross-reactive antigens between E. histolytica and E. histolytica-like Laredo, E. hartmanni, E. coli, Dientamoeba fragilis, Giardia lamblia, and Trichomonas hominis. These three antibodies were also reactive with T. vaginalis

Notizen: . Macrostomal cell formation is blocked by the antibiotic cerulenin at levels of 15 μg/ml or higher. Inhibition can be reversed up to 4 h following cerulenin addition by washing and resuspending cells in new, noncerulenin-treated transforming principle. In these latter cases, additional time equal to the time spent in the inhibitor, is needed for cells to reach control values of transformation. Neither the addition of saturated or unsaturated fatty acids, cholesterol added alone or in combination with stearic acid, nor a mixture of lipids extracted from Tetrahymena vorax reversed the cerulenin effect. Radioisotope incorporation data showed while protein synthesis was reduced by the end of 1 h and tetrahymanol synthesis by the end of 2 h, little or no effect of this inhibitor occurred on RNA or fatty acid synthesis during these times. One interpretation of these results is that cerulenin, by preventing first protein synthesis and later tetrahymanol synthesis, interferes with synthesis and formation of membranes required for the microstome to macrostome transition.

Notizen: Microfilum lutjani n. g., n. sp. (Microsporida) was found on the gill filaments of Lutjanus fulgens (Teleost) inhabiting the coasts of Senegal. This microsporidium forms xenomas distinguished by the microvilli covering the plasma membrane. At all stages of development individuals have isolated nuclei and are in direct contact with the host cytoplasm. Merogony is binary and sporogony is tetrasporoblastic. the spore (4.75 times 2.60 μm)) is characterized by a manubrium inserted on a laterally offset anchoring disc and extending into a very short, noncoiled polar filament (no longer than 500 nm) in the form of a hook. This type of polar filament has not been described previously in the Microsporida.

Notizen: Geosim was identified as the cause of a distinct earthy/grassy odour detected in cultures of a free-living amoeba, Vannella species. Volatile components of cell lysates were isolated and concentrated by the Closed Loop Stripping method. Capillary, gas chromatography/mass spectrometry was used to identify odorous compounds. Bacterial symbionts observed in the cytoplasm of the amoebae may be responsible for production of the geosmin. This appears to be the first report of odorous compounds associated with a free-living protozoan and suggests that in some circumstances, Vannella sp. may contribute to taste and odour problems in drinking water.

Notizen: The literature on discriminant feeding by planktonic protozoans using geometric and nongeometric criteria is reviewed with emphasis on recent studies that indicate phagotrophic protists can use information other than particle size or shape to sort among potential prey. Sufficient data are available for ciliates, aplastidic microflagellates, and phagotrophic dinoflagellates. Numerous representative taxa of all three groups have chemosensory capabilities, either to specific chemicals or to prey exudates, that modify their motility patterns resulting in aggregation or dispersal. Representatives of all three groups also have specific prey preferences. These considerations imply, but do not prove, selectivity in feeding through use of chemical cues. Although prey geometry is clearly a first-order determinant of ingestion through passive mechanical selection, recent studies illustrate that planktonic ciliates and flagellates can use other criteria to discriminate among prey. the evidence clearly implicates use of chemical cues, most likely perceived through contact chemoreception. Filter feeders as well as raptors have such abilities indicating that feeding mechanisms per se do not imply limitations on feeding behavior. Evidence of considerable flexibility and complexity in chemoperceptive feeding suggests that we have only glimpsed the more detailed features of feeding behavior in aquatic protozoans.

Notizen: The study of microbial food webs is dominated by field measurements of microbial standing stocks and rate processes and to a lesser extent by laboratory studies. These approaches reflect the concerns of microbial ecologists to assess accurately the capabilities of microorganisms and to compare microbial processes to other ecosystem parameters. These approaches have led to enormous advances in understanding microbial food webs. Reconciling our expanding knowledge with general questions about the significance and representation of microbial food webs in ecosystem studies requires additional approaches including comparative studies and field experiments. Comparative studies, analyses of microbial stocks or rates across a wide range of ecosystems, lead to quantitative models of microbial processes. These models facilitate testing of hypotheses at a very general level, allow the comparison of different stocks or rate processes across a gradient of systems, and detect unusual situations or outlier systems. Field experimental manipulations offer the advantages of working with intact natural communities, of direct evaluation of results with statistical methods, and of testing important qualitative hypotheses. Both comparative and field manipulation studies have led to important advances in the study of microbial food webs and should be expanded.

Notizen: Repeated exposure of trypanosomes in vitro or in vivo to low concentrations of the methylating agent 1,2-bis(methylsulfonyl)-1-methylhydrazine induces a series of moderately synchronous morphological and biochemical changes. Cell division halts and the long-slender bloodstream forms transform to short-stumpy forms via larger intermediate-stage cells which contain approximately double the normal G2 content of DNA. In common with naturally occurring short-stumpy trypanosomes, drug-induced short-stumpy forms do not infect rodents and when transferred to Cunningham's medium, transform to and replicate as procylics. Furthermore, these short-stumpy forms exhibit α-ketoglutarate supported motility and oxygen consumption, acquire the ability to reduce nitroblue tetrazolium (NADH diaphorase positivity) and appear to be in the G1 or G0 stage of the cell cycle based upon DNA content.

Notizen: Tomonts and their theront offspring of the hymenostomatid fish parasite Ichthyophthirius multifiliis were exposed to calcium levels from 0 to 0.8 mM Ca2+. The survival and reproductive rates of tomonts in the absence of extracellular calcium were not significantly different from rates of tomonts provided calcium. Theronts that developed in the absence of calcium, however, were not infective for Ictalurus punctatus even when the extracellular magnesium concentration was doubled. Theronts that developed in 0.10 mM Ca2+ were infective (0.77 trophonts/mm2 of pectoral fin) to essentially the same extent as theronts provided 0.33 mM Ca2+. Infectivity of those provided 0.8 mM Ca2+ was 1.79 trophonts/mm2 of fin, similar to that of theront controls. Theronts deprived of extracellular calcium as they developed contained significantly fewer secretory mucocysts than did theronts provided 0.1 to 0.8 mM Ca2+ although no significant differences among groups occurred with respect to abundance of crystalline or differentiating mucocysts. Theronts deprived of extracellular calcium also had swollen or enlarged mitochondria and abnormal crystalline mucocysts.

Notizen: Four types of anomalous conjugation were documented in Stylonychia mytilus. Type I pairs were formed between mates of different sizes. These pairs exhibited an abnormal site of fusion in at least one of the mates, and the mates might face each other ventrally throughout conjugation instead of the normal side-by-side position. Type I pairs underwent sexual nuclear development and proceeded with the first cortical reorganization as in normal conjugants. Type II involved pairing at the anterior ends of mates with ventral surfaces facing the same direction. These pairs also underwent sexual nuclear development. Hence, aberrant orientation of the mates, and also ectopic sites of cytoplasmic fusion, if extensive, would permit sexual development. Type III pairs were united ventral-to-ventral with their anterior-left sides at the adoral zone of membranelles, and remained as such throughout conjugation. In these pairs, nuclear and cortical events were typical of the asexual development of physiological reorganization. In Type IV pairs, one mate of the pair possessed a fission furrow and developed two sets of ciliature typical of binary fission, while the other mate might undergo physiological reorganization or binary fission. Type III and Type IV pairs thus reveal the asexual state of early conjugants, which can pursue either one of the two modes of asexual cortical reorganization; these cases reinforce the notion of overlap of asexual and sexual cycles during conjugation of hypotrichs. Spontaneous autogamy was documented for the first time for this genus. The autogamonts proceeded with nuclear development and with the first cortical reorganization. Some probably underwent second and third reorganizations, as in conjugants, but accompanied by abnormalities, particularly in the stages beyond fertilization. Post-autogamous clones were nonviable except for one dubious case.

Notizen: Leishmania major promastigotes were washed and resuspended in an iso-osmotic buffer. The rate of oxidation of 14C-labeled substrates was then measured as a function of osmolality. An acute decrease in osmolality (achieved by adding H2O to the cell suspension) caused an increase in the rates of 14CO2 production from [6-14C]glucose and, to a lesser extent, from [1, (3)-14C]glycerol. An acute increase in osmolality (achieved by adding NaCl, KCl, or mannitol) strongly inhibited the rates of 14CO2 production from [1-: 14C]alanine, [1-14C]glutamate, and [1, (3)-14C]glycerol. The rates of 14CO2 formation from [1-14C]laurate, [1-14C]acetate, and [2-14C]glucose (all of which form [1-14C]acetyl CoA prior to oxidation) were also inhibited, but less strongly, by increasing osmolality. These data suggest that with increasing osmolality there is an inhibition of mitochondrial oxidative capacity, which could facilitate the increase in alanine pool size that occurs in response to hyper-osmotic stress. Similarly, an increase in oxidative capacity would help prevent a rebuild up of the alanine pool after its rapid loss to the medium in response to hypo-osmotic stress.

Notizen: The developmental stages of a recently described microsporidian from the nucleus of hematopoietic cells of salmonid fish were found to be unique among the Microsporida. All observed stages, including meronts, sporonts, and spores were in direct contact with the host cell nucleus (principally hematopoietic cells) of chinook salmon (Oncorhynchus tshawytscha). There is no par-asitophorous vacuole and sporogony does not involve formation of a pansporoblastic membrane as with other members of the suborder Apansporoblastina. The extrusion apparatus differentiates prior to division of sporogonial plasmodia. The spores are ovoid (1 times 2 μm) and uninucleate, and possess a coiled polar tube with 8-12 turns. Developmental stages of the salmonid microsporidian are similar to those described for Enterocytozoon bieneusi as found in the intestinal mucosa of human AIDS patients. However, the intranuclear development, different cell types, and host infected clearly separate the salmonid and human parasites. Accordingly, the intranuclear parasite of salmonids is given the name Enterocytozoon salmonis n. sp. within the suborder Apansporoblastina.

Notizen: . Mirror-image symmetry doublets of the ciliate Stylonychia pustulata were obtained from the progenies of dividing cells in which cell division was inhibited by heat-shocks. In two components consisting of the doublet, the left (cell's) component possessed ciliary organelles arranged in almost the same pattern as in normal singlets, while the right one had surface organelles located in a mirror-image symmetry of those of the left component. In cell division of the doublet, two sets of ciliary primordia that were arranged in a mirror-image symmetry developed synchronously in both components. In about 80% of oral primordia (OP) of the right components, the arrangement of the membranellar bands became abnormal. In some cases, OP of the right component were occasionally separated into two longitudinal halves, each consisting of normal membranelles and inverted membranelles. A set of primordia of the paroral membranelles and fronto-ventro-transverse cirri was rarely derived from the basal bodies of the right half with a band of normal membranelles. As a result, a third component with the ciliary organelles normally arranged emerged on the right side of the original right component. The differentiation of membranelles and segmentation of the primordial streaks into cim proceeded from anterior to posterior. A cytoplasmic bulge with multiple right marginal cirral rows was frequently formed at the right margin of the doublet. The behavior in the separation of third and fourth streaks from a primordial streak of dorsal cirri was not mirror-image symmetrical in each component.

Notizen: . Major fatty acid components of Acanthamoeba castellanii lipids extracted after growth at 30°C include myristate, palmitate, stearate and the polyunsaturates linoleate, eicosadienoate, eicosatrienoate and arachidonate, with oleate as the sole major monounsaturated fatty acid. By comparison, growth at 15°C gave increased linoleate, eicosatrienoate and arachidonate, but decreased oleate and palmitate. When the growth temperature was shifted downwards from 30°C to 15°C, increased lipid unsaturation occurred over a period of 24 h; thus decreases of oleate and eicosadienoate were accompanied by increases in linoleate, eicosatrienoate, arachidonate and eicosapentaenoate. An upwards shift from 15°C to 30°C gave negligible alterations in fatty acid composition over a similar period. At 15°C organisms rapidly use [1-14C] acetate for de novo fatty acid synthesis; stearate is converted via oleate to further desaturation and chain elongation products. Similar short term experiments at 30°C indicate only de novo synthesis and Δ9-desaturation; synthesis of polyunsaturates was a much slower process. Rapid incorporation of [1-14C] oleate at 30°C was not accompanied by metabolic conversion over two hours, whereas at 15°C n-6 desaturation to linoleate was observed. Temperature shift of organisms from 15°C to 30°C in the presence of [1-14C] acetate revealed that over half of the fatty acids in newly-synthesised lipids were saturated, but the proportions of unsaturated fatty acids increased with time until the total polyenoate components reached 17% after 22 h. A shift of temperature in the reverse direction gave a corresponding figure of 60% for polyunsaturated fatty acids. These results emphasize the importance of n-6 desaturation in the low temperature adaptation of Acanthamoeba castellanii.

Notizen: . A survey for Babesia microti in rodents was conducted at six sites within Grand Teton National Park, Wyoming. Blood and spleen smears, hematocrits, and reticulocyte counts were made on all of the animals to evaluate parameters for the diagnosis of babesiosis. Ticks were removed for identification. Of 257 Microtus montanus, 103 were infected with B. microti. In addition, five of 12 Microtus pennsylvanicus and one of three Arvicola richardsoni were parasitized by B. microti. Peromyscus maniculatus (n = 40) were not infected. Concurrent infections by Hepatozoon sp., Trypanosoma sp., and the bacterium, Grahamella sp., were noted in blood smears from a number of M. montanus. Splenomegaly and reticulocytosis were significant parameters associated with babesiosis while decreased hematocrit was not. Ticks removed from the voles were identified as Ixodes eastoni and were the probable vectors of the B. microti.

Notizen: . Analysis of total DNA isolated from the Chrysophyte alga Ochromonas danica revealed, in addition to nuclear DNA, two genomes present as numerous copies per cell. The larger genome (˜120 kilobase pairs or kbp) is the plastid DNA, which is identified by its hybridization to plasmids containing sequences for the photosynthesis genes rbcL, psbA, and psbC. The smaller genome (40 kbp) is the mitochondrial genome as identified by its hybridization with plasmids containing gene sequences of plant cytochrome oxidase subunits I and II. Both the 120- and 40-kbp genomes contain genes for the small and large subunits of rDNA. The mitochondrial genome is linear with terminal inverted repeats of about 1.6 kbp. Two other morphologically similar species were examined, Ochromonas minuta and Poteriochromonas malhamensis. All three species have linear mitochondrial DNA of 40 kbp. Comparisons of endonuclease restriction-fragment patterns of the mitochondrial and chloroplast DNAs as well as those of their nuclear rDNA repeats failed to reveal any fragment shared by any two of the species. Likewise, no common fragment size was detected by hybridization with plasmids containing heterologous DNA or with total mitochondrial DNA of O. danica; these observations support the taxonomic assignment of these three organisms to different species. The Ochromonas mitochondrial genomes are the first identified in the chlorophyll a/c group of algae. Combining these results with electron microscopic observations of putative mitochondrial genomes reported for other chromophytes and published molecular studies of other algal groups suggests that all classes of eukaryote algae may have mitochondrial genomes 〈 100 kbp in size, more like other protistans than land plants.