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1.
The partitioning of copper and molybdenum between silicate melts and aqueous fluids has been determined at 750°C, and 1.4 Kb. The experiments were conducted in a 12 inch ID, rapid quench, cold seal pressure vessel. The aqueous and glass phase run products were analyzed by atomic absorption spectrophotometry and ion microprobe, respectively. The vapor/melt partition coefficient for copper, DvlCu, defined as the ratio of the concentrations of copper in the vapor to copper in the melt was found to be DvlCu = (9.1 ± 2.5)mvCl at NNO up to at least 4.5 moles of chlorine per kg of solution. The partition coefficient for molybdenum is equal to 2.5 ± 1.6 at NNO and QFM; its value is independent of the fluorine concentration of the melt up to at least 1.7 wt. percent fluorine, and of the chlorine concentration up to at least 4.5 moles of chlorine per kg of solution. Copper is probably present in the univalent state in both the silicate melt and in the associated aqueous phase at NNO; the most important aqueous complex of copper is probably CuCl0. Molybdenum is probably present in the aqueous phase as one or more molybdate species.  相似文献   

2.
3.
Twenty-six new high precision 87Sr86Srratio determinations and existing analyses are used to discuss the strontium isotopic composition of the Upper Cretaceous ophiolitic rocks of the Troodos Massif, Cyprus. Relative to initial magmatic 87Sr86Sr ratios (0.70338 ± 0.00010 to 0.70365 ± 0.00005), the hydrothermally metamorphosed pillow lavas and dyke complex have been contaminated by isotopically heavier strontium.This observation confirms the hypothesis that hydrothermal metamorphism was a consequence of sea water-rock interaction, since sea water was the only readily accessible reservoir of isotopically heavier strontium. The fact that metagabbros and altered trondhjemites were also Sr isotopically contaminated shows that sea water penetrated approximately 2 km into the oceanic crust represented by the ophiolitic sequence.The amount of Sr isotopic contamination requires that the bulk sea water: rock ratio was at least ~15:1 and shows that water-rock interaction occurred in a flow system. The degree of oxidation decreases with increasing depth. This shows that the vertical component of fluid flow was downward. The absolute bulk water/rock ratio (for water at S.T.P.), as estimated from the oxidation profile, may have been as large as ~3 × 103:1 —a large figure which independently confirms that rocks showing strong δ18O shifts have interacted with large volumes of water.The sites of discharge of the hot fluid, which must have come out of the system, are identified as the cupriferous pyrite ore deposits. This process of mass transfer corresponds to hydrothermal convection in a permeable medium with an open upper boundary surface.  相似文献   

4.
Numerical modeling of the terrestrial oxygen budget based on the revised δ13Ccarb record by Veizeret al. (1980) has shown that total photosynthetic oxygen has varied between ±7% and ±10% of its average reservoir size (~3.2 × 1022 g) during the last 800 myr as a result of oscillations of the sedimentary reservoir of organic carbon. Calculated curves of oxygen evolution display a distinct minimum in the Early Paleozoic framed by two maxima in the Latest Proterozoic and the Mesozoic. The sympathetic relationship observed between the curves of total oxygen evolution and respective functions for the partial reservoir of sulfate-bound oxygen suggests that the O2 required for an additional conversion of sulfide to sulfate was most probably provided by excess burial of organic carbon, the results of the modeling thus adding credence to current interpretations proposed for the negative correlation between the secular 13C12C and 34S32S trends.  相似文献   

5.
The reaction between hydrous iron oxides and aqueous sulfide species was studied at estuarine conditions of pH, total sulfide, and ionic strength to determine the kinetics and formation mechanism of the initial iron sulfide. Total, dissolved and acid extractable sulfide, thiosulfate, sulfate, and elemental sulfur were determined by spectrophotometric methods. Polysulfides, S42? and S52?, were determined from ultraviolet absorbance measurements and equilibrium calculations, while product hydroxyl ion was determined from pH measurements and solution buffer capacity.Elemental sulfur, as free and polysulfide sulfur, was 86% of the sulfide oxidation products; the remainder was thiosulfate. Rate expressions for the reduction and precipitation reactions were determined from analysis of electron balance and acid extractable iron monosulfide vs time, respectively, by the initial rate method. The rate of iron reduction in moles/liter/minute was given by d(reduction Fe)dt = kSt0.5(J+)0.5 AFeOOH1 where St was the total dissolved sulfide concentration, (H+) the hydrogen ion activity, both in moles/ liter; and AFeOOH the goethite specific surface area in square meters/liter. The rate constant, k, was 0.017 ± 0.002m?2 min?1. The rate of reduction was apparently determined by the rate of dissolution of the surface layer of ferrous hydroxide. The rate expression for the precipitation reaction was d(FeS)dt = kSt1(H+)1 AFeOOH1 where d(FeS)dt was the rate of precipitation of acid extractable iron monosulfide in moles/liter/minute, and k = 82 ± 18 mol?1l2m?2 min?1.A model is proposed with the following steps: protonation of goethite surface layer; exchange of bisulfide for hydroxide in the mobile layer; reduction of surface ferric ions of goethite by dissolved bisulfide species which produces ferrous hydroxide surface layer elemental sulfur and thiosulfate; dissolution of surface layer of ferrous hydroxide; and precipitation of dissolved ferrous specie and aqueous bisulfide ion.  相似文献   

6.
The South Mountain batholith of southwestern Nova Scotia is a large, peraluminous, granodiorite-granite complex which intrudes mainly greenschist facies metasediments of the Cambro-Ordovician Meguma Group. Using Rb-Sr isochrons constructed from whole rocks and mineral separates, the present study shows a variation in age and initial ratios of the intrusive phases of the batholith as follows: biotite granodiorite (371.8 ± 2.2 Ma, (87Sr86Sr)i ranges from 0.7076 ± 0.0003 to 0.7090 ± 0.0003, with the average = 0.7081); adamellite (364.3 ± 1.3 Ma, (87Sr86Sr)i = 0.70942 ± 35); porphyry (361.2 ± 1.4 Ma, (87Sr86Sr)i = 0.71021 ± 119); using λ87Rb = 1.42 × 10?11yr?1.A suite of Meguma country rock samples showed a variation of 87Sr86Sr = 0.7113?0.7177 at the time of intrusion of the batholith. A number of xenoliths of this material occurring in the marginal granodiorite had partially equilibrated isotopically with the granodiorite at a higher 87Sr86Sr ratio than elsewhere in the granodiorites. This evidence demonstrates that isotopic (and probably some accompanying bulk chemical) contamination by the Meguma rocks has been an important factor in determining the ultimate chemical composition and mineralogy of the South Mountain batholith.The (87Sr86Sr)372 = 0.7081 of the early granodiorites indicates that the parent magma of the South Mountain batholith was derived from a source unlike the Meguma Group. The precise nature of the source region cannot be determined by Rb-Sr work unless the degree of contamination with Megumalike material is known.  相似文献   

7.
The 26Al, light rare gas and major and minor element contents of Al-rich and poor samples separated from Allende. Bereba and Junivas have been measured. The production rate of 21Ne from Al (21PAl) is (1.9 ± 0.6) × 21PSi and 2221PAl = 1.4 ± 0.4. The 3He, 21Ne and 38Ar exposure ages of the eucritic pyroxenes agree suggesting complete cosmogenic gas retention. The eucritic feldspars have lost virtually all 3He and most radiogenic 4He. The equation 26Al = 0.42 ± 0.41 Mg + 2.74 ± 0.21 Si + 4.92 ± 0.51 Al + 1.33 S + 0.24 Ca + 0.03 Fe reproduces within 15% our 26Al measurements and the average values measured in ordinary chondrites without recourse to unusual cosmic-ray effects.  相似文献   

8.
A corundum-hibonite inclusion, BB-5, has been found in the Murchison carbonaceous chondrite. This is the first reported occurrence of corundum as a major phase in any refractory inclusion, even though this mineral is predicted by thermodynamic calculations to be the first condensate from a cooling gas of solar composition. Ion microprobe measurements of Mg isotopic compositions yield the unexpected result for such an early condensate that 26Mg excesses are small: δN26Mg = 7.0 ± 1.6%. for hibonite and 5.0 ± 4.8%. for corundum, despite very large 27Al24Mg ratios, 130 and 2.74 × 104, respectively. Within the errors, δN26Mg does not vary over this exceedingly large range of 27Al24Mg ratios. The extreme temperature required to melt this inclusion makes a liquid origin unlikely, except possibly by hypervelocity impact involving refractory bodies. If, instead, BB-5 is a direct gas-solid condensate, textural evidence implies that corundum formed first and later reacted to produce hibonite. In this model, BB-5's uniform enrichment in 26Mg must be a characteristic of the reservoir from which it condensed. Because severe difficulties are encountered in making such a reservoir by prior decay of 26Al, nebular heterogeneity in magnesium isotopic composition is a preferred explanation.  相似文献   

9.
Radioactivity measurements have shown evidence for long-lived 92Nb and 2.03 × 104yr 94Nb in natural niobium. The specific activity of 94Nb was observed to be 0.32 ± 0.03 dis/min. kg Nb and that of 92Nb to be 0.058 ± 0.035 dis/min. kg Nb. With t12 taken as ≈ 1.7 × 108yr, the isotopic abundance of 98Nb is 1.2 × 10?10 per cent.  相似文献   

10.
The sulfide and sulfate contents and their δ34S values were determined in Quaternary volcanic rocks from the Japanese Islands Arc. The total sulfur contents are much lower (less than 40 ppm) and the δ34S values are higher (+4.4 ± 2.1) than those of ocean-floor basalts (800 ± 100 ppm and +0.8 ± 0.5, respectively; Moore and Fabbi, 1971; Sakaiet al., 1982). Lateral variations of both sulfur content and δ34S values were observed in the four volcanic belts in Japan. In the Northeast Japan belt, the sulfur content (30 ± 10 ppm) of the rocks in the inner zone (the Japan Sea side) is 3 to 5 times that in the outer zone (the Pacific side), although the δ34S values of the two zones are almost the same (+4.3 ± 1.0). The δ34S values for the two belts in West Japan are on the average 2%. higher than those of East Japan.This study suggests that the primary magmas that formed the island arc volcanic rocks are initially depleted in sulfur (<120 ppm) and enriched in 34S (δ34S: +5 ~ +7) compared to ocean-floor tholeiitic basalts which formed at mantle under oceanic region. This indicates that the upper-mantle is heterogeneous in sulfur content and isotope composition.  相似文献   

11.
The concentrations of 238Pu, 239 + 240Pu, 241Am and 137Cs were determined in rain samples collected at Monaco in the course of 1978–1979. Based on these data, the annual deliveries of these radionuclides to the Mediterranean by rain are computed to be 0.18 ± 0.01 pCim?2 for 238Pu, 8.1 ± 0.1 pCim?2 for 239 + 240Pu, 0.58 ± 0.02 pCim?2 for 241Am and 351 ± 4 pCim?2 for 137Cs.Comparing the delivery data with the mixed layer inventories of 239 + 240Pu and 241Am in the Mediterranean, the upper limits of the mean residence time of these radionuclides in the mixed layer were estimated to be 12.3 yr for 239 + 240pu and 2.9 yr for 241Am. These values are consistent with the conclusion deduced from the vertical distribution pattern of these transuranic elements in the Mediterranean.Based on delivery values, the annual activity ratios for 238pu239 + 240Pu, 241Am239 + 240Pu and 239 + 240pu137Cs are found to be 0,022, 0.072 and 0.023 respectively. The 238pu239 + 240pu and 239 + 240Pu137Cs activity ratios vary within relatively narrow ranges with time, while a much wider variation was observed for the 241Am239 + 240Pu activity ratio. The cause of the wider variation of the 241Am239 + 240Pu ratio may be related to the difference in the mean age of fallout brought down in different seasons.  相似文献   

12.
Small live individuals of Globigerinoides sacculifer which were cultured in the laboratory reached maturity and produced garnets. Fifty to ninety percent of their skeleton weight was deposited under controlled water temperature (14° to 30°C) and water isotopic composition, and a correction was made to account for the isotopic composition of the original skeleton using control groups.Comparison of. the actual growth temperatures with the calculated temperature based on paleotemperature equations for inorganic CaCO3 indicate that the foraminifera precipitate their CaCO3 in isotopic equilibrium. Comparison with equations developed for biogenic calcite give a similarly good fit. Linear regression with Craig's (1965) equation yields: t = ?0.07 + 1.01t? (r= 0.95) where t is the actual growth temperature and t? Is the calculated paleotemperature. The intercept and the slope of this linear equation show that the familiar paleotemperature equation developed originally for mollusca carbonate, is equally applicable for the planktonic foraminifer G. sacculifer.Second order regression of the culture temperature and the delta difference (δ18Oc ? δ18Ow) yield a correlation coefficient of r = 0.95: t? = 17.0 ? 4.52(δ18Oc ? δ18Ow) + 0.03(δ18Oc ? δ18Ow)2t?, δ18Oc and δ18Ow are the estimated temperature, the isotopic composition of the shell carbonate and the sea water respectively.A possible cause for nonequilibnum isotopic compositions reported earlier for living planktonic foraminifera is the improper combustion of the organic matter.  相似文献   

13.
Solution calorimetric measurements compared with solubility determinations from the literature for the same samples of gibbsite have provided a direct thermochemical cycle through which the Gibbs free energy of formation of [Al(OH)4 aq?] can be determined. The Gibbs free energy of formation of [Al(OH)4 aq?] at 298.15 K is ?1305 ± 1 kJ/mol. These heat-of-solution results show no significant difference in the thermodynamic properties of gibbsite particles in the range from 50 to 0.05 μm.The Gibbs free energies of formation at 298.15 K and 1 bar pressure of diaspore, boehmite and bayerite are ?9210 ± 5.0, ?918.4 ± 2.1 and ?1153 ± 2 kJ/mol based upon the Gibbs free energy of [A1(OH)4 aq?] calculated in this paper and the acceptance of ?1582.2 ± 1.3 and ?1154.9 ± 1.2 kJ/mol for the Gibbs free energy of formation of corundum and gibbsite, respectively.Values for the Gibbs free energy formation of [Al(OH)2 aq+] and [AlO2 aq?] were also calculated as ?914.2 ± 2.1 and ?830.9 ± 2.1 kJ/mol, respectively. The use of [AlC2 aq?] as a chemical species is discouraged.A revised Gibbs free energy of formation for [H4SiO4aq0] was recalculated from calorimetric data yielding a value of ?1307.5 ± 1.7 kJ/mol which is in good agreement with the results obtained from several solubility studies.Smoothed values for the thermodynamic functions CP0, (HT0 - H2980)T, (GT0 - H2980)T, ST0 - S00, ΔH?,2980 kaolinite are listed at integral temperatures between 298.15 and 800 K. The heat capacity of kaolinite at temperatures between 250 and 800 K may be calculated from the following equation: CP0 = 1430.26 ? 0.78850 T + 3.0340 × 10?4T2 ?1.85158 × 10?4T212 + 8.3341 × 106 T?2.The thermodynamic properties of most of the geologically important Al-bearing phases have been referenced to the same reference state for Al, namely gibbsite.  相似文献   

14.
For sulfates of Miocene evaporites in the Carpathian Foredeep, the waters of crystallization of gypsum (w.c.g.) have δD = ?38 to ?113%. and δ18O = 0 to ?11%. (SMOW). The δ34S and δ18O values of the sulfates are uniform and consistent with a marine origin. It is proposed that the original w.c.g. was equilibrated with marine water. Subsequently, it re-equilibrated towards very isotopically light water (δD ~ ?100%., δ18O ~ ?14%) during a glacial or postglacial period and is now trending towards current waters circulating through the deposits (δD ~ ?50%., δ18 ~ ?7%). The extent of reequilibration increased with decreasing crystal size.  相似文献   

15.
Eggwaters from the chambered cephalopod Nautilus are depleted in both 18O and deuterium relative to ambient seawater. Eggwaters from six other species, including the related chambered cephalopod Sepia, do not show such depletion. These observations indicate that the previously observed step towards more positive δ18O values in calcium carbonate laid down after Nautilus hatches, relative to carbonate precipitated prior to hatching, can be explained by equilibration of the carbonate with water in the egg before hatching and with seawater after hatching. The presence of an oxygen isotope difference between eggwater and seawater for Nautilus and its absence for Sepia suggest that hatching will be recorded in the δ18O values of shell carbonates for some but not all extinct and extant chambered cephalopods.The δ13C values of the organic fraction of the siphuncle in Nautilus do not show any consistent pattern with regard to the time of formation before or after hatching. This observation suggests that the minimum in δ13C values previously observed for calcium carbonate precipitated after Nautilus hatches is not caused by a change in food sources once the animal becomes free-swimming, as has been suggested.  相似文献   

16.
High precision mass spectrometric determination of calcium isotope ratios allows the 40K → 40Ca radioactive decay to be used for dating a much broader range of geologic materials than is suggested by previous work. 40Ca42Ca is used to monitor enrichments in 40Ca and can be measured to ±0.01% (2σ) using an exponential mass discrimination correction (Russell et al., 1978) and large ion currents. The earth's mantle has such a low KCa (~0.01) that it has retained “primordial” 40Ca42Ca = 151.016 ± 0.011 (normalized to 42Ca44Ca = 0.31221), as determined by measurements on two meteorites, pyroxene from an ultramafic nodule, metabasalt, and carbonatite. 40Ca42Ca ratios can be conveniently expressed relative to this value as ?Ca in units of 10?4. To test the method for age dating, a mineral isochron has been obtained on a sample of Pikes Peak granite, which has been shown to have concordant KAr, RbSr, and UPb ages. Plagioclase, K-feldspar, biotite, and whole rock yield an age of 1041 ± 32 m.y. (2σ) in agreement with previous age determinations (λK = 0.5543 b.y.?1, λβ?λK = 0.8952, 40K = 0.01167%). The initial 40Ca42Ca of 151.024 ± 0.016 (?Ca = +0.5 ± 1.0), indicates that assimilation of high K/Ca crust was insufficient to affect calcium isotopes. Measurements on two-mica granite from eastern Nevada indicate that the magma sources had K/Ca ≈ 1, similar to intermediate-composition crustal rocks. These results show that the KCa system can be used as a precise geochromometer for common felsic igneous and metamorphic rocks, and may prove applicable to sedimentary rocks containing authigenic K minerals. The relatively short half-life of 40K, the non-volatile daughter, and the fact that potassium and calcium are stoichiometric constituents of many minerals, make the KCa system complementary to other dating methods, and potentially applicable to a variety of geologic problems.  相似文献   

17.
18.
The geochemical history of Lake Lisan, the Pleistocene precursor of the Dead Sea, has been studied by geological, chemical and isotopic methods.Aragonite laminae from the Lisan Formation yielded (equivalent) Sr/Ca ratios in the range 0.5 × 10?2?1 × 10?2, Na/Ca ratios from 3.6 × 10?3 to 9.2 × 10?3, δ18OPDB values between 1.5 and 7%. and δ13CPDB from ?7.7 to 3.4%..The distribution coefficient of Na+ between aragonite and aqueous solutions, λANa, is experimentally shown to be very sensitive to salinity and nearly temperature independent. Thus, Na/Ca in aragonite serves as a paleosalinity indicator.Sr/Ca ratios and δ18O values in aragonite provide good long-term monitors of a lake's evolution. They show Lake Lisan to be well mixed, highly evaporated and saline. Except for a diluted surface layer, the salinity of the lake was half that of the present Dead Sea (15 vs 31%).Lake Lisan evolved from a small, yet deep, hypersaline Dead Sea-like, water body. This initial lake was rapidly filled-up to its highest stand by fresh waters and existed for about 40,000 yr before shrinking back to the present Dead Sea. The chemistry of Lake Lisan at its stable stand represented a material balance between a Jordan-like input, an original large mass of salts and a chemical removal of aragonite. The weighted average depth of Lake Lisan is calculated, on a geochemical basis, to have been at least 400, preferably 600 m.The oxygen isotopic composition of Lake Lisan water, which was higher by at least 3%. than that of the Dead Sea, was probably dictated by a higher rate of evaporation.Na/Ca ratios in aragonite, which correlate well with δ13C values, but change frequently in time, reflect the existence of a short lived upper water layer of varying salinity in Lake Lisan.  相似文献   

19.
Eighteen basalts and some volcanic gases from the submarine and subaerial parts of Kilauea volcano were analyzed for the concentration and isotope ratios of sulfur. By means of a newly developed technique, sulfide and sulfate sulfur in the basalts were separately but simultaneously determined. The submarine basalt has 700 ± 100 ppm total sulfur with δ34SΣs of 0.7 ± 0.1 ‰. The sulfate/sulfide molar ratio ranges from 0.15 to 0.56 and the fractionation factor between sulfate and sulfide is +7.5 ± 1.5‰. On the other hand, the concentration and δ34SΣs values of the total sulfur in the subaerial basalt are reduced to 150 ± 50 ppm and ?0.8 ± 0.2‰, respectively. The sulfate to sulfide ratio and the fractionation factor between them are also smaller, 0.01 to 0.25 and +3.0‰, respectively. Chemical and isotopic evidence strongly suggests that sulfate and sulfide in the submarine basalt are in chemical and isotopic equilibria with each other at magmatic conditions. Their relative abundance and the isotope fractionation factors may be used to estimate the ?o2 and temperature of these basalts at the time of their extrusion onto the sea floor. The observed change in sulfur chemistry and isotopic ratios from the submarine to subaerial basalts can be interpreted as degassing of the SO2 from basalt thereby depleting sulfate and 34S in basalt.The volcanic sulfur gases, predominantly SO2, from the 1971 and 1974 fissures in Kilauea Crater have δ34S values of 0.8 to 0.9%., slightly heavier than the total sulfur in the submarine basalts and definitely heavier than the subaerial basalts, in accord with the above model. However, the δ34S value of sulfur gases (largely SO2) from Sulfur Bank is 8.0%., implying a secondary origin of the sulfur. The δ34S values of native sulfur deposits at various sites of Kilauea and Mauna Loa volcanos, sulfate ions of four deep wells and hydrogen sulfide from a geothermal well along the east rift zone are also reported. The high δ34S values (+5 to +6%.o) found for the hydrogen sulfide might be an indication of hot basaltseawater reaction beneath the east rift zone.  相似文献   

20.
The carbonato and hydrogencarbonato complexes of Mg2+ were investigated at 25 and 50° in solutions of the constant ClO4? molality (3 M) consisting preponderantly of NaClO4. The experimental data could be explained assuming the following equilibria: Mg2+ + CO2B + H2O ag MgHCO+3 + H+, log 1β1 = ?7.644 ± 0.017 (25°), ?7.462 ± 0.01 1 (50°), Mg2+ + 2 CO2g + 2 H2Oag Mg(HCO3)02 ± 2 H+, log 1β2 = ?15.00 ± 0.14 (25°), ?15.37 ± 0.39 (50°), Mg2+ + CO2g + H2Oag MgCO03 + 2 H+, log 1k1 = ?15.64 ± 0.06 (25°),?15.23 ± 0.02 (50°), with the assumption γMgCO30 = γMg(HCO3)02, ΔG0(I = 0) for the reaction MgCO03 + CO2g + H2O = Mg(HCO3)02 was estimated to be ?3.91 ± 0.86 and 0.6 ± 2.4 kJ/mol at 25 and 50°C, respectively. The abundance of carbonate linked Mg(II) species in fresh water systems is discussed.  相似文献   

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