Calibrations for benthic foraminiferal Mg/Ca paleothermometry and the carbonate ion hypothesis     

H. Elderfield  J. Yu  P. Anand  T. Kiefer  B. Nyland   《Earth and Planetary Science Letters》2006,250(3-4):633-649

Benthic foraminiferal magnesium/calcium ratios were determined on one hundred and forty core-top samples from the Atlantic Ocean, the Norwegian Sea, the Indian Ocean, the Arabian Sea and the Pacific Ocean, mostly at sites with bottom water temperatures below 5 °C. Mg/Ca ratios are consistently lower, by  0.2 mmol/mol, in samples cleaned using oxidative and reductive steps than using oxidative cleaning. Differences between Cibicidoides species have been identified: Mg/Ca of Cibicidoides robertsonianus > Cibicidoides kullenbergi > Cibicidoides wuellerstorfi. Comparison with bottom water temperatures support observations of lowered Mg/Ca of C. wuellerstorfi at temperature below  3 °C compared with values predicted by published calibrations and from other Cibicidoides species. Hydrographic data shows that carbonate ion saturation (Δ[CO₃²⁻]) decreases rapidly below this temperature. An empirical sensitivity of Δ[CO₃²⁻] on Mg/Ca has been established for C. wuellerstorfi of 0.0086 ± 0.0006 mmol/mol/μmol/kg. A novel application using modern temperatures and Last Glacial Maximum temperatures derived via pore fluid modelling supports a carbonate ion saturation state effect on Mg incorporation. This may significantly affect calculated δ¹⁸O_seawater obtained from foraminiferal δ¹⁸O and Mg/Ca temperature.  相似文献   

Distribution of ionospheric O~ ion in synchronous altitude region     

史建魁  刘振兴  ZHANG T.L  郭兼善  张满莲  尚社平  罗熙贵 《中国科学D辑(英文版)》2003,46(10)

Since ions originating from the ionosphere were discovered in the magnetosphere in the be-ginning of 1970s[1], it is gradually confirmed that the ionosphere is a source of magnetospheric ion (the other source is solar wind). Research result on ionospheric…  相似文献   

Deep melting and sodic metasomatism underneath the highly oblique-spreading Lena Trough (Arctic Ocean)     

Eric Hellebrand  Jonathan E Snow 《Earth and Planetary Science Letters》2003,216(3):283-299

Abyssal peridotites collected along the highly oblique-spreading Lena Trough north of Greenland and Spitsbergen have mineral compositions that are similar to residual abyssal peridotites, except for high sodium concentrations in clinopyroxene (cpx). Most samples are lherzolites with light rare earth element (REE)-depleted cpx trace element patterns, but significantly fractionated middle to heavy REE ratios at relatively high heavy REE concentrations. Such characteristics can only be explained by initial melting of a garnet peridotite followed by low degrees of melting in the stability field of spinel peridotite. The residual garnet signature requires either a high potential temperature of the upwelling mantle, or elevated solidus-lowering water contents. The limited spinel field melting suggests a deep cessation of melt extraction, possibly because of the presence of a thick lithospheric cap. This is consistent with the extremely low effective spreading rate and the vicinity to a passive continental margin, which allow conductive cooling to reach deeper levels than commonly estimated for faster mid-ocean ridges. High sodium concentrations in cpx are neither explainable by melt refertilization, nor by a simple diffusion mechanism. The efficient fractionation of sodium from the light REE requires post-melting metasomatism, which is typically restricted to the subcontinental lithosphere. This might imply that the Lena Trough peridotites represent unroofed subcontinental mantle, from which no melt was extracted during the opening of the Lena Trough. It is more likely that sodic metasomatism occurred after partial melting underneath the Lena Trough, and that such an enrichment process is responsible for elevated sodium concentrations in abyssal peridotites elsewhere. Sodium in cpx of residual peridotites can therefore not serve as an indicator of partial melting or melt refertilization.  相似文献   

热液中银、铅、锌共生分异的实验研究   总被引：4，自引：1，他引：4  

尚林波  樊文苓  邓海琳 《矿物学报》2003,23(1):31-36

对NaCl—HCl—H2O体系中银、铅、锌氯络合物稳定性进行实验研究，结果表明：热液中银、铅、锌氯络合物的稳定性受体系温度、pH、Eh以及组分浓度的控制。相同温度下，H^ 、Cl^-浓度降低，还原硫增加，均使络合物趋于不稳定，发生不同程度的沉淀分异。当t=300℃,[Cl^-]=0.24mol/L,pH＝6．86时，铅氯络合物的沉淀量达55％，锌氯络合物的沉淀量超过92％。热液体系中硫化物的存在，对银的影响最大，溶液中的银氯络合物几乎沉淀完全，浓度可降至检测限以下。而铅和锌的氯络合物相对稳定。热力学计算表明：溶液中的银是以硫化银或自然银的形式沉淀析出。因此，还原硫的存在是导致热液体系中银与铅锌发生分异的重要因素。  相似文献   

两种质谱仪在辉钼矿铼-锇年龄测定中的应用比较     

梁树平  屈文俊  杜安道  杨刚  陈江峰 《岩矿测试》2004,23(4):268-272

对同一地区但Re、Os含量不同的一组辉钼矿样品,分别采用电感耦合等离子体质谱(ICP-MS)和负离子热表面电离质谱(NTIMS)对其Re-Os年龄进行了测定比较。结果表明,该组样品的平均Re-Os模式年龄分别为(138.3±4.0)Ma和(141.0±3.6)Ma(2σ,n=9),采用ISOPLOT软件的模式1进行等时线计算,得到等时线年龄分别为(138.6±2.9)Ma(2σ,n=9)和(141.6±1.9)Ma(2σ,n=9),两者在目前水平下的误差范围内基本一致。另外,分别采用ICP-MS和NTIMS对辉钼矿Re-Os年龄国家一级标准物质GBW04435和GBW04436进行了测定,所得的结果吻合也较好。  相似文献   

宝石中常见过渡金属离子致色的理论解释   总被引：5，自引：0，他引：5  

罗红宇王春生  廖尚宜 《岩石矿物学杂志》2004,23(2):177-180

从晶体场理论或配位场理论出发，应用群论的方法，从理论上系统地解释了宝石中常见的因过渡金属离子在不同的配位场环境下而引起的能级分裂，并详细地阐述了这一理论分析的程序，最后列举实例并给予了理论解释。  相似文献   

直接酸溶法浸取硫铁矿烧渣中铁的实验研究   总被引：4，自引：0，他引：4  

郝艳玲  范福海 《岩石矿物学杂志》2004,23(3):279-281

对常压下用盐酸直接酸溶提取硫铁矿烧渣中的铁进行了实验研究，探讨了影响硫铁矿烧渣酸溶的因素。结果表明，影响铁溶出率的主要因素为液固比、反应时间和温度；当液固比为4．0mL／g、反应温度100℃时，高速搅拌反应2h后，铁的溶出率可达72％，浸取液经进一步处理可生产氯化铁系列产品，有较好的应用前景。  相似文献   

Geochemical Process of Gas Hydrate Formation in the Nankai Trough Based on Chloride and Isotopic Anomalies in Interstitial Water   总被引：2，自引：0，他引：2  

Hitoshi Tomaru    Ryo Matsumoto    Hailong Lu  Takashi Uchida 《Resource Geology》2004,54(1):45-51

Abstract: Interstitial water expelled from gas hydrate-bearing and -free sediments in the Nankai Trough are analyzed in terms of Cl-, SO₄²-, δ¹⁸O and δD. The baselines for the Cl- concentration and δ¹⁸O value are close to seawater values (530 mM and 0%), indicating that the interstitial water is of seawater origin. The δD values decrease with depth, implying isotopic exchange of hydrogen between upwelling biogenic methane depleted in D and interstitial water. The Cl- concentrations in gas hydrate-bearing sediments are anomalously low, while the δ¹⁸O and δD values are both high, suggesting that the water forming these gas hydrates was poor in Cl- and enriched in ¹⁸O and D during gas hydrate formation. Calculation of the gas hydrate saturations using Cl "and δ¹⁸O anomalies gives results of up to 80 % in sand, and shows that the δ¹⁸O baseline is not consistent with the Cl" baseline. The δ¹⁸O baseline increases by +1% in gas hydrate-free clay and silt. This is considered to be caused by clustering of water molecules after gas hydrate dissociation in response to the upward migration of the base of gas hydrate stability, as indicated by the presence of a double bottom-simulating reflector at this site. The water clusters enriched in ¹⁸O are responsible for the increase in the δ¹⁸O baseline with normal Cl". The abrupt shallowing of the base of gas hydrate stability may induce the dissociation of gas hydrates and the accumulation of gases in the new stability zone, representing a geological process that increases gas hydrate saturation.  相似文献   

Hydrogen Isotopes of Glassy and Phyllosilicate Spherules in Al Rais (CR) and Orgueil (CI) Chondrites     

Michael E.ZOLENSKY 《《地质学报》英文版》2004,78(5)

The hydroxyl in phyllosilicate minerals is the most common occurrence of water in primitive meteorites. Direct hydrogen isotopic analysis of this water component using an ion microprobe has been made in some glassy or phyllosilicate spherules from the Al Rais (CR) and Orgueil (CI) chondrites. The spherules from Al Rais show large deuterium excesses (δD = +200 -+800‰) relative to terrestrial standards, whereas deuterium-enrichments in the spherules from Orgueil are much smaller (δD = +40 - +130‰). The phyllosilicate spherules are products of  相似文献   

海盐氯循环对输送污染物致酸的缓冲作用   总被引：1，自引：0，他引：1  

姚小红  黄美元  高会旺  郝吉明 《大气科学》1998,22(6):913-918

着重研究海盐氯循环对输送污染物致酸的缓冲作用,通过对全球低污染点酸雨资料分析,初步结论是:海盐氯循环使经过海洋上空输送的致酸大气污染物转化为中性盐,这一机制缓冲了经过海洋上空输送的致酸前提物的酸性,使受体点降水中出现氯亏损、硫富集,并伴随有降水中氯亏损和H+离子浓度的负相关。在高氯亏损降水样品中,降水pH值一般大于5.0。硫同位素动力学分析表明,当降水pH值大于5.6氯亏损时,污染物在海洋上空输送过程中和海盐发生非均相反应的速率与其发生均相反应的速率接近。但这一机制仅适用沿海地区。  相似文献