层间氧化带砂岩型铀矿床的高精度磁测定位技术研究     

刘祜  刘章月  柯丹  腰善丛 《铀矿地质》2009,25(5):296-302

对鄂尔多斯盆地东北部3片测区进行地面高精度磁测试验研究成果显示,层间氧化带砂岩型铀矿找矿目的层中的氧化带大致对应于磁异常的正值区,还原带大致对应于磁异常的负值区,而氧化一还原过渡带大致对应于磁异常从正值向负值过渡的零值区附近,显示高精度磁测对层间氧化带砂岩型铀矿定位的有效性。  相似文献   

新疆索尔库都克铜钼矿床稀土元素地球化学特征及成矿作用示踪     

赵路通  王京彬  王玉往  刘文华  丁汝褔  李浩  龙灵利  石煜  孙志远 《大地构造与成矿学》2017,41(6)

索尔库都克矽卡岩型铜钼矿床位于新疆东准噶尔北缘,矿区发育早、晚两期矽卡岩并分别伴有成矿作用。两期矽卡岩在产出特征、矿物组合及成矿过程方面均有明显区别,其中与早期矽卡岩有关的成矿金属元素为Fe-Cu-Mo组合,与晚期矽卡岩有关的成矿金属元素为Cu-Mo-Zn组合。本文对索尔库都克铜钼矿床的矽卡岩单矿物、安山质围岩、矿石及与成矿有关的脉岩进行了稀土元素测试分析。结果表明早期矽卡岩成矿过程与安山质围岩关系密切,成矿环境经历了由进化变质阶段的弱还原-弱氧化条件→氧化物阶段的弱还原环境→退化变质早阶段氧化环境→退化变质中晚阶段弱氧化-还原环境的变化过程,铁质可能主要来自于围岩;晚期矽卡岩成矿过程中成矿环境经历了由进化变质阶段的氧化环境→退化变质阶段的弱氧化-弱还原环境→石英-硫化物阶段的弱还原-还原环境→石英-方解石阶段还原环境的变化过程。虽然在具体的成矿过程方面有明显的区别,但在早、晚两期矽卡岩各自的主成矿阶段均经历了由氧化环境向还原环境转变的过程,这种转变为大量金属硫化物的形成创造了良好的条件,是导致矿质沉淀的重要机制。  相似文献   

Geochemical-focusing of manganese in lake sediments — An indicator of deep-water oxygen conditions   总被引：1，自引：0，他引：1  

Tobias Schaller  Bernhard Wehrli 《Aquatic Geochemistry》1996,2(4):359-378

The lateral distributions of Mn concentrations in the sediments of two Swiss lakes under varying oxygen conditions have been determined. The comparison of Mn distribution patterns with oxygen in the deep-water provides strong evidence for a geochemical-focusing effect, which is driven by the redox cycle of manganese. Conditions essential for this process to occur are anoxic sediments in contact with oxic deep-water. Average sedimentary manganese concentrations determined for different water-depth ranges are directly proportional to the area of shallower sediments. This result indicates that geochemical-focusing of manganese in lake sediments is a promising proxy indicator for the reconstruction of oxygen conditions during deposition.  相似文献   

微生物对某些岩土工程性质的影响   总被引：14，自引：0，他引：14  

周芳琴  王银善 《岩土力学》1997,18(2):17-22

探讨了由于环境因素变化诱发的物理化学和生物化学变化对岩土工程性质的影响，着重研究了有机质和微生物引起的氧化还原作用对起胶结作用的游离氧化铁赋存状态转化的影响。强调指出，这种影响可能导致岩土工程的安全问题。  相似文献   

层间氧化带型砂岩铀矿床地浸过程的热力学研究：以伊犁盆地512铀矿床为例   总被引：4，自引：2，他引：2  

李德平  王保群等 《地质论评》2002,48(6):642-650

伊梨盆地512层间氧化带型砂岩铀矿床是中国第一个工业化规模开发的地浸铀矿床,作者简要地介绍了其地质特征和地浸开发工艺,并利用较新的Gibbs自由能和平衡常数数据,对该矿床地浸处理中铀的地球化学行为进行了定量研究。首先,通过标准电动势（E^o）,氧化-还原电位（Eh）的计算和分析,阐明了H2O2、硝酸盐、大气中自由氧都能提升溶液的Eh值,从而加速矿物相U^4 的氧化溶解,为了节约地浸氧化剂成本,对于U^4 /U^6 比值不太高的矿床来说,建议充分利用大气中自由氧化氧化剂,然后,通过化学平衡计算,推导出了地下水和硫酸浸出液中铀存在形式的计算公式,计算结果表明：（1）512铀矿床矿体所赋存的含矿层地下水中,铀主要以碳酸铀酰类络合物形式存在,并且以UO2（CO3)^4-3和UO2（CO3）^2-2形式为主,并随着pH从7.31升高到8.20,UO2CO3从3.80%降低到0.06%,UO2（CO3）^2-2从21.91%降低到3.12%,而UO2（CO3）^4-3则从74.28%升高到96.82%,（2）512铀矿床硫酸浸出液中,铀主要以硫酸铀酰类络合物形式存在,其中,UO2SO4占63.28%～ 63.86%,UO2(SO4)^2-2占16.55%～21.36%,UO^2 2占15.04%～19.62%,从推导出的计算公式可以看出,硫酸浸出液中铀的存在形式随溶液pH、总SO^2-4含量的变化而变化,并呈非线性关系,为了提高离子交换树脂的吸附性能,可利用文中推导出的公式进行计算,以使调节溶浸液的pH和总SO^2-4含量,从而达到浸出液中铀存在形式的最佳比例关系,最后,因热力学数据对化学反应平衡计算的影响呈指数关系,在进行热力学数据计算时,必须采用较新、较准确的数据。  相似文献   

Mantle Redox State Evolution in Eastern China and Its Implications     

LI Jianping  WANG Jian Guangzhou Institute of Geochemistry  Chinese Academy of Sciences  Guangzhou Liu Shuchun Zhu Xiling 《《地质学报》英文版》2002,76(2):238-248

Using the secondary spinel standard, the authors have precisely measured the Fe3+/∑ Fe values of spinels in mantle xenoliths from Cenozoic basalts in eastern China, and estimated the oxygen fugacities recorded by 63 mantle xenoliths through olivine-orthopyroxene-spinel oxygen barometry. The results indicate that the oxygen fugacities of the lithospheric mantle in eastern China are higher in the south than in the north. Among them, the oxygen fugacity of the North China craton lithospheric mantle is the lowest, similar to that of the oceanic mantle, while that of Northeast and South China are the same as that of the global continental mantle. The variations of mantle redox state in eastern China are mainly controlled by the C-O-H fluids derived from the asthenospheric mantle. According to the mantle oxidation state, it can be concluded that the C-O-H fluids in the lithospheric mantle of eastern China consist mainly of CO2 and minor H2O, but CH4-rich fluids should come from the asthenosphere where the ox  相似文献   

Molecular biomarker record of paleooceanographic environment in the East China Sea during the last 35000 years   总被引：2，自引：0，他引：2  

孟宪伟  杜德文  刘炎光  刘振夏 《中国科学D辑(英文版)》2002,45(2):184-192

By reference of the δ¹⁸O and δ¹³C isotopic compositions of G.sacculifer and accelerator mass spectrometry (AMS)¹⁴C dates, the U _K ³⁷ , ∑C _– ²¹ /∑C _+- ²² and Pr/Pn in core DGKS9603 have been used to characterize the changes of paleooceanographic environment occurring in the East China Sea (ECS) during the last 35000 years. The stratigraphic records of these proxies have shown that during the last 35 ka the Okinawa Trough has gone through 7 stronger cold-climate events (C₁–C₇) and 9 terrigenous matter-decreasing events (e₂–e₉), of which, the C₁ corresponds to the cold episode occurring in the middle late Holocene, C₂–C₄ and C₇ correspond to the H₁–H₄ events, respectively. e₁ and e₃–e₈ correspond to the decrease of sea surface temperature (SST), respectively. The terrigenous inputs increased when Heinrich events occurred. Climate colding resulted in the decrease of terrigenous matter transported by rivers, and the increase of that transported by winter monsoon. Heinrich events are closely related to East Asia monsoon. During the Last Glacial Maximum (LGM, 15.5–25.8 Cal ka BP), reduction environment fluctuated strongly, bringing forth three stronger reduction events (R₁–R₃) and one weaker reduction event (O), of which, R₁–R₃ correspond to the decrease of SST and increase of terrigenous nutrient and O corresponds to the decrease of terrigenous nutrient. The fluctuation of reduction condition must be related to the change of sea surface productivity.  相似文献   

Geochemical Modelling as a Tool for Actinide Speciation during Anoxic Leaching Processes of Nuclear Fuel     

M. Amme 《Aquatic Geochemistry》2002,8(3):177-198

The behaviour of many radiotoxic elements, which are contained within spent nuclear fuel planned for direct disposal, is strongly dependent on the redox chemistry of the aqueous media present in the deep geological systems, where such disposal options are investigated. Especially actinide elements are known to be sensitive. The knowledge of the speciation of actinides in the case of a possible mobilisation by intruding groundwater is therefore crucial and part of the source term calculation of many countries' performance assessment procedures. In this study, the influence of redox conditions and complexant concentration in two selected groundwaters upon the species distribution of U and Pu is assessed by using the thermodynamic modeling code PHREEQC version 2.3. The modeled systems were derived from laboratory leaching experiments testing nuclear fuel dissolution. For the calculations, critically reviewed data for U and Pu complexation were used. The results show that under the conditions calculated, U and Pu are present mainly as U(VI) and Pu(IV). The presence of solid UO₂ substrate is supposed to change this distribution. The calculational use of different groundwaters as aqueous phase, implying a slightly different solution composition, affects U and Pu speciation: U species distribution is affected mainly by complexant concentration, Pu species are influenced by pH changes. A sensitivity study on Pu speciation is performed; constants changed within their confidence intervals were applied. The results are compared with experimental observations, and differences and possible expected effects during the dissolution of real, complex materials are discussed.  相似文献   

Effects of a diel oxygen cycle on nitrogen transformations and greenhouse gas emissions in a eutrophied subtropical stream   总被引：2，自引：0，他引：2  

John A. Harrison  Pamela A. Matson  Scott E. Fendorf 《Aquatic Sciences - Research Across Boundaries》2005,67(3):308-315

  相似文献   

Comparison of antimony behavior with arsenic under various soil redox conditions     

Satoshi Mitsunobu Teppei Harada Yoshio Takahashi 《中国地球化学学报》2006,25(B08):98-99

Antimony （Sb） is a toxic element and belongs to group 15 of the periodic table, under arsenic （As）. The geochemical behavior of Sb in the environment is still largely unknown. Since the behavior of Sb in the environment depends on its oxidation state, Sb analysis in environmental samples requires quantitative measurement of Sb （Ⅲ） and Sb （Ⅴ）. The aim of this study is the speciation of Sb in both solid and water phases to understand the reaction and dynamics of Sb in soil-water system. Accordingly, we employed X-ray absorption fine structure （XAFS） analysis to determine the Sb and As species in soil in laboratory and natural systems, while we also determined the oxidation states in soil water by the conventional HPLC-ICP-MS method. Natural soil and soil water samples containing Sb and As were collected around the Ichinokawa mine pithead, Ehime, Japan. To observe the species under various redox conditions, the soil and soil water samples were collected at four depths. Soil containing Sb and As were incubated for 7 days at 25℃ to observe their oxidation states under various redox condition by changing the total amount of water in the soil. Antimony K-edge XAFS spectra were measured at the beamline BL01B 1 at SPring-8 （Hyogo, Japan） and K-edge XAFS spectra of As, Fe, and Mn at the beamline BL12C in Photon Factory, KEK （Thukuba, Japan）. In the natural soil-water system, Sb was present exclusively as Sb （Ⅴ） over a wide redox range （from Eh=-140 to 360 mV; pH 8）, while As was present as a mixture of As （Ⅲ） and As （Ⅴ）. This trend was confirmed in the laboratory experiments. These results suggest that Sb （Ⅴ） is a very stable form in the environment and that Sb is oxidized under more oxic condition than As. Combining the results of Fe and Mn XAFS analyses and a positive correlation among Sb, As, and Fe abundances in the soil, the host phases of Sb and As in soil were Fe （Ⅲ） hydroxide. EXAFS analyses of Sb and As are also consistent with this fact. Under reducing conditions, the concentrations of As in the soil water increased whereas those of Sb decreased in both the natural and laboratory systems.  相似文献