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51.
Solubility of Anhydrite, CaSO4, in NaCl-H2O Solutions at High Pressures and Temperatures: Applications to Fluid-Rock Interaction 总被引:1,自引:0,他引:1
Anhydrite solubility in H2ONaCl solutions was measuredat 614 kbar, 600800°C and NaCl mole fractions(XNaCl) of 00·3 in pistoncylinder apparatus.Solubilities were determined by weight changes of natural anhydritein perforated Pt envelopes confined with fluid in larger Ptcapsules. In initially pure H2O at 10 kbar and 800°C, CaSO4concentration is low (0·03 molal), though much largerthan at the same temperature and 1 kbar. Hematite-buffered experimentsshowed slightly lower solubilities than unbuffered runs. CaSO4solubility increases enormously with NaCl activity: at 800°Cand 10 kbar and XNaCl of 0·3, CaSO4 molality is 200 timeshigher than with pure H2O. Whereas CaSO4 solubility in pureH2O decreases with rising T at low T and P, the high-P resultsshow that anhydrite solubility increases with T at constantP at all XNaCl investigated. The effects of salinity and temperatureare so great at 10 kbar that critical mixing between sulfate-richhydrosaline melts and aqueous salt solutions is probable at900°C at XNaCl 0·3. Recent experimental evidencethat volatile-laden magmas crystallizing in the deep crust mayevolve concentrated salt solutions could, in light of the presentwork, have important implications regarding such diverse processesas Mount Pinatubo-type S-rich volcanism, high-f O2 regionalmetamorphism, and emplacement of porphyry CuMo ore bodies,where anhydritehematite alteration and fluid inclusionsreveal the action of very oxidized saline solutions rich insulfur. KEY WORDS: anhydrite; sulfur; solubility; metamorphic brines; granulites 相似文献
52.
ROBERT S. DIETZ 《Meteoritics & planetary science》1966,3(1):27-29
Abstract Shatter cones have been discovered in two residual boulders in the central uplift eye of the Middlesboro structure, Kentucky. This finding gives additional support to the interpretation of Englund and Roen (1962) that this is probably an astrobleme, i.e., an ancient meteorite impact scar. 相似文献
53.
54.
The early Ordovician trilobite Angelina sedgwickii has hitherto been known only from stretched and squeezed specimens from North Wales. As a classic example of a deformed fossil, it has featured not only in palaeontological but also in structural geology textbooks, and various methodologies have been employed to attempt to restore it to its original shape. Recently discovered specimens from Shropshire, although flattened, are not sheared and preserve the original bilateral symmetry, affording for the first time an opportunity to find out what this trilobite might really have looked like. 相似文献
55.
ROBERT W. DUCK JOHN McM ANUS 《Boreas: An International Journal of Quaternary Research》1984,13(2):89-93
Scdimentological studies of a small ice-contact proglacial lake at Briksdal. southwest Norway, have led to the discovery of two types of tubular traces developed on the surfaces of material collected in sediment traps. The traces are described and attributed, with certainty, to the burrowing activities of chironomid midge larvae. 相似文献
56.
HEAMAN LARRY M.; CREASER ROBERT A.; COOKENBOO HARRISON O.; CHACKO TOM 《Journal of Petrology》2006,47(4):821-858
The Jericho kimberlites are part of a small Jurassic kimberlitecluster in the northern Slave craton, Canada. A variety of datingtechniques were applied to constrain the nature and age of twoJericho kimberlites, JD-1 (170·2 ± 4·3Ma RbSr phlogopite megacrysts, 172·8 ±0·7 Ma UPb eclogite rutile, 178 ± 5 MaUPb eclogite zircon lower intercept) and JD-3 (173 ±2 Ma RbSr phlogopite megacryst; 176·6 ±3·2 Ma UPb perovskite), and all yielded identicalresults within analytical uncertainty. As there is no discernibledifference in the radiometric ages obtained for these two pipes,the composite RbSr phlogopite megacryst date of 173·1± 1·3 Ma is interpreted as the best estimate forthe emplacement age of both Jericho pipes. The initial Sr isotopecomposition of 0·7053 ± 0·0003 derivedfrom phlogopite megacrysts overlaps the range (0·70430·7084)previously reported for Jericho whole-rocks. These strontiumisotope data, combined with the radiogenic initial 206Pb/204Pbratio of 18·99 ± 0·33 obtained in thisstudy, indicate that the Jericho kimberlites are isotopicallysimilar to Group 1 kimberlites as defined in southern Africa.The Jericho kimberlites are an important new source of mantlexenoliths that hold clues to the nature of the Slave cratonsubcontinental mantle. A high proportion (30%) of the Jerichomantle xenolith population consists of various eclogite typesincluding a small number (23%) of apatite-, diamond-,kyanite- and zircon-bearing eclogites. The most striking aspectof the Jericho zircon-bearing eclogite xenoliths is their peculiargeochemistry. Reconstructed whole-rock compositions indicatethat they were derived from protoliths with high FeO, Al2O3and Na2O contents, reflected in the high-FeO (22·627·5wt %) nature of garnet and the high-Na2O (8·479·44wt %) and high-Al2O3 (13·1214·33 wt %)character of the clinopyroxene. These eclogite whole-rock compositionsare highly enriched in high field strength elements (HFSE) suchas Nb (1331134 ppm), Ta (528 ppm), Zr (17794934ppm) and Hf (2364 ppm). This HFSE enrichment is linkedto growth of large (up to 2 mm) zircon and niobian rutile crystals(up to 3 modal %) near the time of eclogite metamorphism. Thediamond-bearing eclogites on the other hand are characterizedby high-MgO (19·621·3 wt %) garnet andultralow-Na2O (0·441·50 wt %) clinopyroxene.Paleotemperature estimates indicate that both the zircon- anddiamond-bearing eclogites have similar equilibration temperaturesof 9501020°C and 9901030°C, respectively,corresponding to mantle depths of 150180 km. Integrationof petrographic, whole-rock and mineral geochemistry, geochronologyand isotope tracer techniques indicates that the Jericho zircon-bearingeclogite xenoliths have had a complex history involving Paleoproterozoicmetamorphism, thermal perturbations, and two or more episodesof Precambrian mantle metasomatism. The oldest metasomatic event(Type 1) occurred near the time of Paleoproterozoic metamorphism(1·8 Ga) and is responsible for the extreme HFSE enrichmentand growth of zircon and high-niobian rutile. A second thermalperturbation and concomitant carbonatite metasomatism (Type2) is responsible for significant apatite growth in some xenolithsand profound light rare earth element enrichment. Type 2 metasomatismoccurred in the period 1·01·3 Ga and isrecorded by relatively consistent whole-rock eclogite modelNd ages and secondary UPb zircon upper intercept dates.These eclogite xenoliths were derived from a variety of protoliths,some of which could represent metasomatized pieces of oceaniccrust, possibly linked to east-dipping subduction beneath theSlave craton during construction of the 1·881·84Ga Great Bear continental arc. Others, including the diamond-bearingeclogites, could be cumulates from mafic or ultramafic sillcomplexes that intruded the Slave lithospheric mantle at depthsof about 150180 km. KEY WORDS: zircon- and diamond-bearing eclogites; Jericho kimberlite, geochronology; Precambrian metasomatism, northern Slave Craton 相似文献
57.
Laurent REMUSAT Corentin Le GUILLOU Jean‐Noël ROUZAUD Laurent BINET Sylvie DERENNE François ROBERT 《Meteoritics & planetary science》2008,43(7):1099-1111
Abstract— Kainsaz CO3 insoluble organic matter (IOM) was studied using Curie point pyrolysis, electronic paramagnetic resonance (EPR), and high‐resolution transmission electron microscopy (HRTEM) to determine the effect of thermal metamorphism on molecular chondritic fingerprints. Pyrolysis released a very low amount of products that consist of one‐ and two‐ring aromatic units with methyl, dimethyl, and ethyl substituents. Moreover, Kainsaz IOM contains two orders of magnitude fewer radicals than Orgueil, Murchison, and Tagish Lake IOM. In addition, no diradicaloids were found in Kainsaz, although they are thought to constitute a specific signature for weakly organized extraterrestrial organic compounds in contrast to terrestrial ones. HRTEM reveals a very heterogeneous structure, with microporous disordered carbon, mesoporous graphitic carbons and graphite. Graphitization likely occurs and explains the differences between Kainsaz and CI or CM IOM. Heating stress experienced by Kainsaz IOM, on the parent body and/or prior its accretion, is likely responsible for the differences in molecular and structural organizations compared with those of CI and CM IOM. 相似文献
58.
Turbulence structure in stably stratified boundary layers isexperimentally investigated by using a thermally stratified wind tunnel. Astably stratified flow is created by heating the wind tunnel airflow to atemperature of about 50 °C and by cooling the test-section floor to asurface temperature of about 3 °C. In order to study the effect ofbuoyancy on turbulent boundary layers for a wide range of stability, thevelocity and temperature fluctuations are measured simultaneously at adownwind position of 23.5 m from the tunnel entrance, where the boundarylayer is fully developed. The Reynolds number, Re, ranges from 3.14× 104 to 1.27 × 105, and the bulk Richardson number, Ri,ranges from 0 to 1.33. Stable stratification rapidly suppresses thefluctuations of streamwise velocity and temperature as well as the verticalvelocity fluctuation. Momentum and heat fluxes are also significantlydecreased with increasing stability and become nearly zero in the lowest partof the boundary layer with strong stability. The vertical profiles ofturbulence quantities exhibit different behaviour in three distinct stabilityregimes, the neutral flows, the stratified flows with weak stability(Ri = 0.12, 0.20) and those with strong stability (Ri= 0.39,0.47, 1.33). Of these, the two regimes of stratified flows clearly showdifferent vertical profiles of the local gradient Richardson number Ri,separated by the critical Richardson number Ri cr of about 0.25. Moreover,turbulence quantities in stable conditions are well correlated with Ri. 相似文献
59.
Abstract— The distribution of Li, Be, and B was studied by ion microprobe mass spectrometry in 36 chondrules from the Semarkona, Bishunpur, Allende, Clovis #1, and Hedjaz meteorites. Within a single chondrule, Li-Be-B concentrations can vary up to one order of magnitude. For example, in a chondrule from Hedjaz, concentrations range from 0.3 to 2.4 ppm for Li, from <0.001 to 0.17 ppm for Be, and from 0.4 to 5.5 ppm for B. Among chondrules from Semarkona and Bishunpur, clear crystal-mesostasis partitioning was observed in nine chondrules for Li, in nine chondrules for Be, and in three chondrules for B. The heterogeneities in the distribution of Li, Be, and B in chondrules from Semarkona and Bishunpur appear to be primary features that were inherited from the chondrules' precursors and not totally obscured during the chondrules' formation. A redistribution of B was nevertheless observed at the whole-rock scale for Allende (B-Al2O3 correlation) and Hedjaz (B–SiO2 correlation). At the scale of bulk chondrules, a robust correlation is observed for all studied meteorites between the B/Be and the B/Li ratios, which indicates that Li and Be are much less heterogeneously distributed in chondrites than B. Mean Li, Be, and B concentrations of chondrules ([Li] ? 0.83+0.86 ppm; [Be] ? 0.0430.027 ppm; [B] ? 0.89+3.71-0.72 ppm) are consistent with those of Orgueil ([Li] ? 1.49 ppm; [Be] ? 0.0249 ppm; [B] ? 0.87 ppm), but the mean Li/Be ratio of chondrules (24.5+6.5-9.1) is a factor of ~4 depleted relative to Orgueil (Li/Be ratio of ~78). Such a depletion is puzzling because no correlation between Li and Na or B has been found as would be expected to result from volatilization processes during chondrule melting and cooling. As a consequence, the exact abundance of solar system Li remains an open question. 相似文献
60.
MARIANNE V. MOORE MICHAEL L. PACE JOHN R. MATHER PETER S. MURDOCH ROBERT W. HOWARTH CAROL L. FOLT CELIA Y. CHEN HAROLD F. HEMOND PATRICIA A. FLEBBE CHARLES T. DRISCOLL 《水文研究》1997,11(8):925-947
Numerous freshwater ecosystems, dense concentrations of humans along the eastern seaboard, extensive forests and a history of intensive land use distinguish the New England/Mid-Atlantic Region. Human population densities are forecast to increase in portions of the region at the same time that climate is expected to be changing. Consequently, the effects of humans and climatic change are likely to affect freshwater ecosystems within the region interactively. The general climate, at present, is humid continental, and the region receives abundant precipitation. Climatic projections for a 2 × CO2 atmosphere, however, suggest warmer and drier conditions for much of this region. Annual temperature increases ranging from 3–5°C are projected, with the greatest increases occurring in autumn or winter. According to a water balance model, the projected increase in temperature will result in greater rates of evaporation and evapotranspiration. This could cause a 21 and 31% reduction in annual stream flow in the southern and northern sections of the region, respectively, with greatest reductions occurring in autumn and winter. The amount and duration of snow cover is also projected to decrease across the region, and summer convective thunderstorms are likely to decrease in frequency but increase in intensity. The dual effects of climate change and direct anthropogenic stress will most likely alter hydrological and biogeochemical processes, and, hence, the floral and faunal communities of the region's freshwater ecosystems. For example, the projected increase in evapotranspiration and evaporation could eliminate most bog ecosystems, and increases in water temperature may increase bioaccumulation, and possibly biomagnification, of organic and inorganic contaminants. Not all change may be adverse. For example, a decrease in runoff may reduce the intensity of ongoing estuarine eutrophication, and acidification of aquatic habitats during the spring snowmelt period may be ameliorated. Recommendations for future monitoring efforts include: (1) extending and improving data on the distribution, abundance and effect of anthropogenic stressors (non-point pollution) within the region; and (2) improving scientific knowledge regarding the contemporary distribution and abundance of aquatic species. Research recommendations include: (1) establishing a research centre(s) where field studies designed to understand interactions between freshwater ecosystems and climate change can be conducted; (2) projecting the future distribution, activities and direct effects of humans within the region; (3) developing mathematical analyses, experimental designs and aquatic indicators that distinguish between climatic and anthropogenic effects on aquatic systems; (4) developing and refining projections of climate variability such that the magnitude, frequency and seasonal timing of extreme events can be forecast; and (5) describing quantitatively the flux of materials (sediments, nutrients, metals) from watersheds characterized by a mosaic of land uses. © 1997 John Wiley & Sons, Ltd. 相似文献