The effect of temperature and food density on survival and growth of Menidia peninsulae larvae (Pisces: Atherinidae)

Day of hatch tidewater silversides, Menidia peninsulae, were stocked at 5 fish per liter in 3 1 of seawater at 30‰ and raised for 16 days at 20°, 25° and 30 °C. Food organisms (Brachionus sp. or Artemia nauplii) were maintained at 500, 1,000, 5,000 or 10,000 organisms per 1. The influence of food density on growth of larval M. peninsulae was temperature dependent. At 20 °C, there was no difference in final size of fish based on food densities. But at 25° and 30 °C there was an increase in final body size as food density increased. There were no significant differences in survival among food densities in tests at 20°, 25° or 30 °C. However, for any given temperature and food density, the number of survivors in a replicate affected the final size attained. Optimal culture condition for larval M. peninsulae, considering both survival and growth was determined to be 5,000 food organisms per 1 at 25 °C.     

Upper temperature tolerance of spot,Leiostomus xanthurus,from the cape Fear River estuary,North Carolina

The temperature tolerance and resistance times of postlarval (<25 mm SL) and small juvenile spot,Leiostomus xanthurus, from the Cape Fear Estuary, North Carolina were tested in the laboratory. Critical thermal maximum techniques were used to determine first equilibrium loss (FEL) and critical thermal maximum (CTM) end points and thermal shock methods were used to determine 96-h upper incipient lethal temperatures (LT₅₀). Acclimation temperatures ranged from 10 to 35°C and acclimation salinities were 10, 20 and 30‰. A quadratics model was fit to the CTM and FEL data; r² values were 0.924 and 0.928 respectively. Acclimation salinity, estimated weight, acclimation salinity by acclimation temperature interaction and acclimation temperature by estimated weight interaction were the significant components of the CTM model. Predicted CTM values ranged from 30°C at 10 °C and 30‰ acclimation to just over 40°C at 30 °C and 30‰ acclimation. Acclimation temperature, acclimation temperature squared, estimated weight and acclimation temperatures by estimated weight interaction were the significant components of the FEL model. Predicted FEL values ranged from around 28°C at 10°C and 10‰ acclimation to about 39°C at 30°C and 30‰ acclimation. The 96-h LT₅₀ values of spot acclimated to 20‰ increased linearly with acclimation temperature to 25°C. From about 25 to 35°C, LT₅₀ values increased very little with acclimation temperature. The ultimate upper incipient lethal temperature of postlarval and small juvenile spot was estimated at 35.2°C. Increased salinity increased resistance time but decreased LT₅₀ estimates. Thermal shock tests were better for predicting the effects of thermal addition than were CTM tests.     

Reconstructed summer temperature in the northern Rocky Mountains wilderness, USA

Ring widths from whitebark pine (Pinus albicaulis Englem.) and subalpine larch (Larix lyallii Parl.) collected at three high-elevation sites were used to develop tree-growth chronologies to reconstruct summer temperature anomalies. A step-wise multiple regression procedure was used to screen potential predictor variables to generate a transfer function capable of skillfully reconstructing summer temperature. The resulting regression model explained approximately 38% of the adjusted variance in the instrumental temperature record. The fidelity of the reconstruction was verified using product mean and sign tests, both of which suggested significant predictive power in the reconstructions (p < 0.05). Reduction of error (RE) and coefficient of efficiency (CE) measures were both positive, indicating the reconstruction contained useful climate information. Cool periods often coincided with reduced solar activity and/or periods of increased volcanic activity. Differences between this reconstruction and others encompassing a broader geographic scale highlight the importance of developing local reconstructions of climate variability, particularly when used in conjunction with ecological data sets that describe the occurrence of fires or insect epidemics. Mixed and divergent climate-response relationships were evident in the whitebark pine chronologies and suggest subalpine larch may be a more useful species than whitebark pine to target for the development of temperature reconstructions in this region.     

Hydrothermal alteration of organic matter in sediments of the Northeastern Pacific Ocean: Part 2. Escanaba Trough,Gorda Ridge

Samples from the Ocean Drilling Program Leg 169 in Escanaba Trough, Gorda Ridge, NE Pacific Ocean, were analyzed to study maturation by accelerated diagenesis and/or by catagenesis of the sedimentary organic matter to hydrothermal petroleum. At Site 1038 the hydrothermal petroleums have migrated after generation to shallower horizons. The n-alkane maturation was indicated by the strong even C number preference (i.e., CPI <1.0) as in the case of Middle Valley. All samples contained admixed organic matter of terrigenous and marine components as indicated by the distributions of the biomarkers. The biological precursors were catagenetically altered to their equivalent mature compounds. The presence of high molecular weight PAHs in some sediment sections at Site 1038 reflected the high temperature alteration and reworking of organic matter into mature hydrothermal petroleum. At Site 1037, the reference hole in the Escanaba Trough, the n-alkanes with a strong predominance of odd C number homologs reflected immature non-marine lipid components essentially throughout the hole. Maturation of organic matter was only observed below 450 mbsf with n-alkanes showing a CPI <1.0. The strong even C number predominance in those intervals was attributed to initial maturation by high heat flow during the early rifting process.     

Groundwater flow system as an archive of palaeotemperature: Noble gas, radiocarbon, stable isotope and geochemical study in the Pannonian Basin, Hungary

To establish the increase in temperature and the time span of the transition between the Late Glacial Maximum (LGM) and the Holocene, the noble gas content, ¹⁸O, ²H, ¹³C δ values, ³H and ¹⁴C activity and chemistry were studied in a groundwater flow system in Quaternary sediments in Hungary. The study area is a sub-basin of the Pannonian Basin, where the C isotope ratios are not influenced by carbonate reactions along the flow path, because the only water-rock interaction is ion exchange. The δ¹⁸O and δ²H values indicate a cold infiltration period, followed by warming, and, finally, warm temperature conditions. The noble gas data show that the average infiltration temperature was 3.3 °C in the cold, 12.9 °C in the warm, and intermediate in the transitional stage. Using the noble gas temperatures, geochemical batch modelling was performed to simulate the chemical processes. Based on the geochemical model, δ¹³C and ¹⁴C₀ (initial radiocarbon activity) in the recharging water were calculated. Transport modelling was used to simulate the distribution of chemical components, δ¹⁸O, δ²H and ¹⁴C₀, along the flow path. It was found that the main processes determining the chemical composition of the groundwater were dissolution/precipitation of calcite and dolomite during infiltration near the surface, and ion exchange along the flow path. In the recharge area the δ¹³C and ¹⁴C₀ were controlled by dissolution and precipitation of carbonate minerals, C speciation, and fractionation processes. All these processes were influenced by the recharge temperature. NGTs calculated from the dissolved noble gas concentrations showed an average of 3.3 °C for cold, and 12.9 °C for warm infiltration, i.e. for the LGM and for the Holocene. The temperature difference was thus 9.1 ± 0.8 °C, which is one of the largest degree of warming detected by noble gases so far. The alkalinity indicates that carbonate reactions were unimportant along the flow path. Owing to the temperature dependence of the equilibrium constants, temperature conditions during infiltration have to be taken into consideration in radiocarbon age calculation. Dispersive transport along the flow path modified the chemical and isotopic composition of infiltrated water. The contribution of the old pore water, which was free of the ¹⁴C isotope, resulted in uncertainties in radiocarbon age determination. It was concluded that determination of the radiocarbon age or mean residence time requires detailed knowledge of the hydraulic conditions of groundwater.     

Chemical exchange during hydrothermal alteration of basalt by seawater—II. Experimental results for Fe,Mn, and sulfur species

Fresh mid-ocean ridge basalts of varying crystallinity and an andesite were reacted with seawater and with a Na-K-Ca-Cl solution at 200–500°C and 500–1000 bar in sealed gold capsules. $\text{Water}\text{rock}$ mass ratios of one to three were used and durations ranged from two to twenty months. The concentrations of Fe, Mn, and reduced and oxidized sulfur species in solution reached steady state in most of the experiments at 400–500°C, but not in those at 200–300°. The concentrations of Fe and Mn were a few ppm at 200–300° and increased greatly with temperature between 300 and 500°. The low values at 200–300° are probably related to the uptake of Fe and Mn by smectite at the in situ pH, which was slightly acid at 200° and slightly alkaline at 300°. The quench pH values decreased with increasing temperature above 300°. The only reliable data for the concentration of Zn in solution were obtained at 400°, where values 1–2 ppm were found. Copper was extensively leached from basalt and andesite and was deposited as part of a Cu-Au alloy in the capsule walls or, in some experiments, as chalcopyrite.Reduced sulfur was readily leached from basalt into solution, and was also produced by the reduction of seawater sulfate by ferrous iron derived from the basalts. The proportion of seawater sulfate which was reduced in the experiments with a $\text{water}\text{rock}$ ratio of one varied from 5–10% at 300°C to > 95% at 500°. The rate of sulfate reduction depended on the run temperature, on the crystallinity and initial sulfur content of the rocks used as starting materials, and on the $\text{water}\text{rock}$ ratio. The final concentration of reduced sulfur in solution increased greatly with temperature, and generally exceeded that of Fe on a molal basis.The oxide-sulfide assemblages produced in the experiments resemble those in the basalt-seawater geothermal system at Reykjanes, Iceland, and in hydrothermally altered basalts and gabbros from the oceanic crust; they include pyrite, pyrrhotite. chalcopyrite, hematite, and probably magnetite. The particular assemblage varied systematically with the temperature, rock type, and crystallinity of each run. Anhydrite precipitated in all experiments with seawater, at all temperatures from 200–500°C. However, its persistence to the end of the runs was apparently metastable, as it should have reacted with the final solutions to produce pyrite or pyrrhotite.     

Partition of Sr,Ba, Ca,Y, Eu2+, Eu3+, and other REE between plagioclase feldspar and magmatic liquid: an experimental study

Plagioclase feldspar/magmatic liquid partition coefficients for Sr, Ba, Ca, Y, Eu²⁺, Eu³⁺ and other REE have been determined experimentally at 1 atm total pressure in the temperature range 1150–1400°C. Natural and synthetic melts representative of basaltic and andesitic bulk compositions were used, crystallizing plagioclase feldspar in the composition range An₃₅–An₈₅. Partition coefficients for Sr are greater than unity at all geologically reasonable temperatures, and for Ba are less than unity above approximately 1060°C. Both are strongly dependent upon temperature. Partition coefficients for the trivalent REE are relatively insensitive to temperature. At fixed temperature they decrease monotonically from La to Lu. The partition of Eu is a strong function of oxygen fugacity. Under extreme reducing conditions D_Eu approaches the value of D_Sr.     

Geochemistry, age, and petrogenesis of rocks from the Garevka metamorphic complex, Yenisey Ridge

The mineralogical, petrological, geochemical and geochronological data on the Garevka metamorphic complex (GMC) of the Yenisey Ridge were used to evaluate the age, nature, and provenance of their protoliths. The evolution of the GMC occurred in two stages with different ages, thermodynamic regimes, and metamorphic field gradients. The final emplacement of granitoids was marked by high-pressure (HP) amphibolite facies regional metamorphism (970 Ma). At the second stage, these rocks experienced Late Riphean (900–870 Ma) retrograde epidote-amphibolite facies metamorphism accompanied by the formation of blastomylonitic complexes within narrow zones of brittle-ductile deformation. The metamorphism of migmatites (850 Ma) is coeval with the collisional medium-pressure metamorphism of the kyanite-sillimanite type. The GMC is different from the other rock complexes of the Yenisey Ridge in the presence of rapakivi-type granites. The geochemistry of these rocks, which is characterized by stronger enrichment in K₂O, FeO, Y, Th, U, Zr, Hf, Nb, Ta, and REE relative to the other mineral assemblages of the GMC, is typical of anorogenic (A-type) within-plate granites. Among other distinctive features of these rocks are the strong iron enrichment of the melanocratic minerals, the presence of ilmenite as the sole Fe-Ti oxide, and crystallization from higher temperature (T = 825°C vs. T = 750°C) water-poor magmas under reducing conditions below the FMQ buffer. Significant variations in the geochemical and petrological characteristics of the GMC rocks suggest that they could not be derived from a single source. The main volume of the high-K rocks varying in composition from A-type to S-type granites was generated by melting of mixed mantlecrustal sources. The products of melting of the Late Archean-Early Proterozoic infracrustal gneisses of the Siberian Craton could be a possible source for the least oxidized rocks.     

Towards pyrrhotite/magnetite geothermometry in low-grade metamorphic carbonates of the Tethyan Himalayas (Shiar Khola,Central Nepal)

In Mesozoic metacarbonates of the Tethyan Himalayas (Shiar Khola area, Central Nepal) two characteristic remanent magnetisations (ChRM₁ and ChRM₂) were identified by their unblocking temperature spectra. The ChRM₁ is carried by pyrrhotite (unblocking temperature: 270–360°C) and the ChRM₂ by magnetite (unblocking temperature spectra: 430–580°C). The temperature-related formation of pyrrhotite at the expense of primary magnetite during low-grade metamorphism in marly carbonates allows the determination of thermal gradients by the pyrrhotite/magnetite ratio. This new method can be used as a geothermometer for T≤300°C in low-grade metamorphic carbonates, where other methods are not available. This method is applied for the first time in the Tethyan Himalayas of Central Nepal.In the Shiar Khola valley, systematic variations in the ferrimagnetic content of the metacarbonates along an E–W profile were detected by the ratio of remanence intensity of pyrrhotite to magnetite, derived from natural remanent magnetisation (R_PYR/MAG) and saturation magnetisation (S_PYR/MAG). Over a stretch of 10 km the R_PYR/MAG and S_PYR/MAG increase from W to E from ~0.42 to ~0.91 and ~0.48 to ~1.0, respectively. Based on temperature estimates, the eastern part experienced upper anchizone–epizone (~250–300°C) conditions, while the western part underwent only diagenesis (~200°C). The temperature gradient and the temperature ranges suggested are consistent with the findings of the calcite twin lamellae geothermometry which is a non-magnetic method.     

Carbon isotopic disequilibrium in the shell of the freshwater mussel Elliptio complanata

Isotopic analyses of shell material from the freshwater mussel Elliptio complanata produced mean C concentrations that were depleted in ¹⁴C and ¹³C relative to the lake water DIC. Depleted C isotope values were attributed to the incorporation of ¹²C-enriched metabolic C into the shell. Microsampling of longitudinal sections of shell revealed a seasonal pattern in the δ¹³C values. The seasonal pattern matched predictions that DIC δ¹³C and metabolic rate determine the final shell δ¹³C concentration. The greatest depletion of δ¹³C occurred in the summer. Similar δ¹³C patterns in marine and freshwater mollusks probably record not only temperature fluctuations, upwelling events, and phytoplankton blooms as reported, but also the changes in metabolic activity brought on by such events.     

Crystal chemistry, cation ordering and thermoelastic behaviour of CoMgSiO4 olivine at high temperature as studied by in situ neutron powder diffraction

The thermal expansion, structural changes and the site partitioning of Co and Mg in synthetic CoMgSiO₄ olivine have been studied by in situ time-of-flight neutron powder diffraction as a function of temperature, between 25 and 1,000°C. Thermal expansion of the unit cell dimensions and volume are linear within this temperature range and give no indications of a phase transition, although the thermoelastic behaviour indicates a slight strain minimum around 700°C. Co²⁺ shows a strong preference for the M1 site throughout this temperature range with an oscillatory behaviour; it decreases slightly at about 300°C, climbing up to nearly its original value at around 800°C and then decreasing by about 30% at 1,000°C. This behaviour is in contrast with that of (Fe, Mg)₂SiO₄ olivine, in which the initial Fe²⁺ site preference for the M1 site switches to the M2 site beyond a cross-over temperature. The oscillatory site preference in (CoMg)-olivine as a function of temperature is reflected in the M–O polyhedral volume changes and M–O bond lengths, as well as, thermoelastic strain and atomic thermal displacement parameters. The imbalance between the increasing vibrational and decreasing configurational entropy contributions, together with covalent bonding effects rather than crystal field contributions, seem to drive the cation partitioning in (CoMg)-olivine.     

Salinity preferences in the stage I zoeae of three temperate zone fiddler crabs,genus Uca

Zoeae of three species of temperate zone fiddler crabs, Uca pugnax, U. minax, and U. pugilator, were reared in the laboratory. The zoeae of each species were placed individually in artificial salinity gradients and observed for specific salinity preferences. Each species of zoeae displayed a salinity preference that reflected the salinity patterns of the adult crabs of the same species. Zoeae of U. pugnax and U. pugilator, like the adult crabs, displayed a preference for higher salinities (i.e., 20.6‰±3.5 and 21.5‰±3.0, respectively). Zoeae of U. minax, like the adult crabs, displayed a preference for lower salinities (i.e., 9.8‰±2.9).     

Effect of Rapid Thermal Cooling on Mechanical Rock Properties

Laboratory tests have been conducted to investigate the effects of rapid thermal cooling on various rock specimens including igneous, sedimentary, and metamorphic rocks. At first, various types of thermal loading were conducted: heating up to 100, 200, and 300 °C, followed by rapid cooling with a fan. In addition, multiple cyclic thermal cooling (10, 15 and 20 cycles) with a maximum temperature of only 100 °C was conducted. Experiments included edge notched disc (END) tests to determine the Mode I fracture toughness, Brazilian disc tests to determine tensile strength, seismic tests to determine P-wave velocity, and porosity tests leading to meaningful results. Even though only small changes of temperature (rapid cooling from 100 °C to room temperature) were applied, the results showed that crack growth occurred in some rock types (granite, diabase with ore veins, and KVS) while crack healing occurred in other rock types (diabase without ore veins, quartzite, and skarn). To better understand the results, 3D transient thermo-mechanical analysis was conducted using the ANSYS program. The results indicated that there was a thin region near the outside of the specimen where large tensile stresses occur and microcracking would be expected, and that there was a large area in the middle of the specimen where lower magnitude compressive stresses occur and crack closure would be expected. It was found that the more heterogeneous and more coarse-grained rock types are more likely to exhibit crack growth, while less heterogeneous and more fine-grained rocks are more likely to exhibit crack healing.     

Biotransformation of amide using Bacillus sp.: isolation strategy, strain characteristics and enzyme immobilization

Amidase hydrolases/acyltransferases are of considerable industrial interest due to potential applications in the production of useful hydroxamic acids. The test strain, capable of acetamide degradation, was isolated by an enrichment technique with acetamide as sole source of nitrogen. Based on morphology, physiological tests and biochemical tests, this isolate was identified as Bacillus sp. and on the basis of 16S Ribosomal ribonucleic acid sequence, a phylogenetic tree was drawn and was identified as Bacillus megaterium. Resting cells containing active acyltransferase enzyme were prepared and immobilized in the gel beads of sodium alginate, agar, polyacrylamide and polyvinyl alcohol?Calginate. The beads were tested for acyltransferase using Iron (III) chloride reagents at 55°C and were found to be affected by substrate concentration, type of buffer, buffer pH and reaction temperature. These factors were optimized using sodium alginate immobilized beads. This study proved useful in understanding the technique of immobilization of acyltransferase enzyme, its operational stability and its importance in the synthesis of hydroxamic acid.     

Carbon and hydrogen isotope fractionation associated with the aerobic microbial oxidation of methane, ethane, propane and butane

Carbon isotope fractionation factors associated with the aerobic consumption of methane (C1), ethane (C2), propane (C3), and n-butane (C4) were determined from incubations of marine sediment collected from the Coal Oil Point hydrocarbon seep field, located offshore Santa Barbara, CA. Hydrogen isotope fractionation factors for C1, C2 and C3 were determined concurrently. Fresh sediment samples from two seep areas were each slurried with sea water and treated with C1, C2, C3 or C4, or with mixtures of all four gases. Triplicate samples were incubated aerobically at 15 °C, and the stable isotope composition and headspace levels of C1-C4 were monitored over the course of the experiment. Oxidation was observed for all C1-C4 gases, with an apparent preference for C3 and C4 over C1 and C2 in the mixed-gas treatments. Fractionation factors were calculated using a Rayleigh model by comparing the δ¹³C and δD of the residual C1-C4 gases to their headspace levels. Carbon isotope fractionation factors (reported in ε or (α-1) × 1000 notation) were consistent between seep areas and were −26.5‰ ± 3.9 for C1, −8.0‰ ± 1.7 for C2, −4.8‰ ± 0.9 for C3 and −2.9‰ ± 0.9 for C4. Fractionation factors determined from mixed gas incubations were similar to those determined from individual gas incubations, though greater variability was observed during C1 consumption. In the case of C1 and C3 consumption, carbon isotope fractionation appears to decrease as substrate becomes limiting. Hydrogen isotope fractionation factors determined from the two seep areas differed for C1 oxidation but were similar for C2 and C3. Hydrogen isotope fractionation factors ranged from −319.9‰ to −156.4‰ for C1 incubations, and averaged −61.9‰ ± 8.3 for C2 incubations and −15.1‰ ± 1.9 for C3 incubations. The fractionation factors presented here may be applied to estimate the extent of C1-C4 oxidation in natural gas samples, and should prove useful in further studying the microbial oxidation of these compounds in the natural environment.     

Climate and vegetation in Hokkaido, northern Japan, since the LGM: Pollen records from core GH02-1030 off Tokachi in the northwestern Pacific

Vegetation and climate since the LGM in eastern Hokkaido were investigated based on a pollen record from marine core GH02-1030 from off Tokachi in the northwestern Pacific. We also examined pollen spectra in surface samples from Sakhalin to compare and understand the climatic conditions of Hokkaido during the last glacial period. Vegetation in the Tokachi region in the LGM (22–17 ka) was an open boreal forest dominated by Picea and Larix. During the last deglaciation (17–10 ka), vegetation was characterized by abundant Betula. In the Kenbuchi Basin, central Hokkaido, a remarkable increase of Larix and Pinus occurred in the LGM and the last deglaciation, which was assigned as the “Kenbuchi Stadial.” Comparison of climatic data between the core GH02-1030 and that of Kenbuchi Basin demonstrates that variations in temperature and precipitation were larger in inland Hokkaido than in the maritime area of the Pacific coast. During the LGM in the Tokachi region, the August mean temperature was about 5 °C lower, and annual precipitation was about 40% lower than today. In the Kenbuchi Basin, central Hokkaido, the August mean temperature was about 8 °C lower, and annual precipitation was half that of today. During the last deglaciation, August mean temperatures were about 3 °C lower, and annual precipitation was about 30% lower than today in the Tokachi region. In the Kenbuchi Basin, August mean temperatures were about 5–8 °C lower, and annual precipitation was about 40–60% lower than today. Cold ocean water and a strengthened summer monsoon after 15 ka may have resulted in the formation of advection fogs, reduced summer temperatures, and a decrease in the seasonal temperature difference in the Tokachi district, which established favorable maritime conditions for Betula forests.     

Isotopic composition of a large photosymbiotic foraminifer: Evidence for hypersaline environments across the Great Australian Bight during the late Pleistocene

Analysis of carbon and oxygen isotopic compositions of large benthic foraminifera tests (Marginopora vertebralis) that lived in the Great Australian Bight during the late Pleistocene, reveal that the tests are enriched by 1 to 3‰ in both ¹⁸O and ¹³C relative to modern specimens from the same region. The intolerance of M. vertebralis for cool waters negates lower ocean water temperature as an explanation for such high δ¹⁸O values. The oxygen isotopic compositions are thus interpreted to reflect tests secreted in hypersaline waters of up to 56 ppt salinity, concentrated from seawater by evaporation. M. vertebralis thrives today in waters of similar salinity at Shark Bay, Western Australia. The Pleistocene sedimentary assemblage supports an interpretation that environments broadly similar to those in outer modern-day Shark Bay were wide spread across the Great Australian Bight during portions of marine isotope stages 2, 3 and 4. The high δ¹³C values of the Pleistocene M. vertebralis are interpreted to reflect enhanced photosynthetic activity that depletes dissolved carbonate in ¹²C in such shallow, saline settings. These hypersaline environments formed during periods of lower sea-level when shallow-waters (< 20 m depth) extended from the shoreline over ~ 100 km across what is currently a relatively deep shelf. This study indicates that shelf bathymetry was a critical determinant of past environments of deposition across the Great Australian Bight.     

The earliest Cambrian UHT metamorphism in the Qaidam block,western China: A record of the final assembly of Greater Gondwana?

The final assembly of Gondwana, known as the late Pan-African orogeny, is characterized by Ediacaran–early Cambrian ultrahigh temperature (UHT) metamorphism, which is widely identified within reconstructed East Gondwana. This distinctive feature likely provides a reliable criterion for identifying new Gondwanan terranes that lack paleo-geomagnetic data. Here we present zircon U–Pb geochronology and phase equilibria calculations for a variety of granulite types newly recognized from western Qaidam, China, which provide the first evidence that the Qaidam block, at least western Qaidam, experienced high-grade metamorphism in excess of 900 °C before/at 540–520 Ma. These UHT metamorphic rocks, similar to many well-known Pan-African UHT metamorphic terranes, is inferred to evolve along a clockwise P–T path that is usually related to collisional orogens. Comparison between new metamorphic zircon U–Pb ages from western Qaidam and the published age data from the UHT metamorphic terranes within East Gondwana suggests that the UHT metamorphic rocks found in western Qaidam similarly records the final assembly of Gondwana. Although the exact paleo-geographical location of the Qaidam block during the Gondwana period is unknown yet because of lacking paleo-geomagnetic data, new Pan-African UHT metamorphic record found in western Qaidam indicates, for the first time, that the Qaidam block is a Gondwanan terrane that split from this semi-supercontinent after the Pan-African orogeny.     

Oxygen isotope study of metamorphic rocks from the Ouégoa district,New Caledonia

48 minerals from 18 in situ metamorphic rocks (mostly metasediments) from the Ouégoa district have been studied. Particular emphasis was placed on obtaining isotopic data for quartz, calcite and muscovite but some pyroxenes and amphiboles were also examined. Data for Ouégoa rocks show they have tended to be isotopically homogenized by metamorphism and that the effect of increasing metamorphism is to progressively deplete the rocks of heavy C and O isotopes. These results indicate that during metamorphism the rocks isotopically exchanged through the medium of a widespread oxygen-carrying fluid phase. Tentatively assigned temperatures obtained from isotopic data for quartz-calcite and quartz-muscovite pairs, using the calibration curves of Epstein and Taylor (1967), indicate lawsonite in the Ouégoa schists to be stable over a temperature range of 250 to 400° C and epidote from ca. 380° to at least 550° C. Temperatures for metamorphic zones in Ouégoa blueschists closely parallel those obtained for Type III and IV glaucophane-bearing rocks from Ward Creek, California (Taylor and Coleman, 1968). The measured tectonic thickness of lawsonite-bearing schists has been used to calculate a lithostatic pressure increment of 2 Kb and geothermal gradient of 20° C per km for the lawsonite zone. Comparison of lithostatic pressure increment with total pressure increment estimated from the stability relations of lawsonite over the temperature range 250–400° C (3.5 Kb Nitsch, 1972) suggest P _total ≠ P _lithostatic and that that the pressure of the fluid phase may have exceeded lithostatic pressure.     

Seawater temperature proxies based on DSr, DMg, and DU from culture experiments using the branching coral Porites cylindrica

In order to investigate the incorporation of Sr, Mg, and U into coral skeletons and its temperature dependency, we performed a culture experiment in which specimens of the branching coral (Porites cylindrica) were grown for 1 month at three seawater temperatures (22, 26, and 30 °C). The results of this study showed that the linear extension rate of P. cylindrica has little effect on the skeletal Sr/Ca, Mg/Ca, and U/Ca ratios. The following temperature equations were derived: Sr/Ca (mmol/mol) = 10.214(±0.229) − 0.0642(±0.00897) × T (°C) (r² = 0.59, p < 0.05); Mg/Ca (mmol/mol) = 1.973(±0.302) + 0.1002(±0.0118) × T (°C) (r² = 0.67, p < 0.05); and U/Ca (μmol/mol) = 1.488(±0.0484) − 0.0212(±0.00189) × T (°C) (r² = 0.78, p < 0.05). We calculated the distribution coefficient (D) of Sr, Mg, and U relative to seawater temperature and compared the results with previous data from massive Porites corals. The seawater temperature proxies based on D calibrations of P. cylindrica established in this study are generally similar to those for massive Porites corals, despite a difference in the slope of D_U calibration. The calibration sensitivity of D_Sr, D_Mg, and D_U to seawater temperature change during the experiment was 0.64%/°C, 1.93%/°C, and 1.97%/°C, respectively. These results suggest that the skeletal Sr/Ca ratio (and possibly the Mg/Ca and/or U/Ca ratio) of the branching coral P. cylindrica can be used as a potential paleothermometer.