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碳硅泥岩型铀矿床是我国铀矿地质工作者建立的铀矿床类型，是我国四大铀矿工业类型之一。桂西地区是我国华南地区一个重要的碳硅泥岩型铀矿床产出区域，包括大新（373）铀矿床等多个典型铀矿床（点）。研究辉绿岩与矿床成因的联系，对重新认识矿床成因有重要意义。本文在对桂西大新-钦甲地区碳硅泥岩型铀矿床和辉绿岩脉野外地质研究的基础上，系统研究了辉绿岩的地质特征、岩石学、地球化学特征以及其中锆石的U-Pb同位素年代学特征，在此基础上，探讨了辉绿岩的成岩与碳硅泥岩型铀矿床成矿间的关系。元素地球化学特征显示Rb、U、Th、Ba等大离子亲石元素的含量都高于MORB值，高场强元素Ta、Nb、Zr、Hf等均相对于MORB有所富集，而HREE元素中等亏损，表明本区辉绿岩属于富集地幔特征的板内碱性玄武岩系列（WPB），属于华南陆内伸展构造背景下软流圈上涌导致富集岩石圈地幔部分熔融形成的铁镁质岩浆发生侵位的产物。辉绿岩脉3个样品的锆石LA-ICP-MS U-Pb年龄为86.7±0.9Ma、89.05±0.96Ma、91.6±8.3Ma，表明形成于晚白垩纪早期，与华南地区与中基性岩脉有关的铀矿床成矿时代具有较好的对应关系，也与华南地区广泛分布的中生代基性岩脉时代一致，对应于华南白垩纪构造应力场中四次重要的拉张活动时代中的一期。辉绿岩脉锆石特征指示了辉绿岩成岩过程对矿源层中铀的活化所产生的重要作用以及成岩与成矿之间的热动力联系；结合元素地球化学、矿床成矿年龄和辉绿岩锆石U-Pb同位素年龄研究结果表明，区内铀矿床具有多期成矿特点，即'沉积期铀预富集、辉绿岩作用下二次预富集、后期热液再次富集成矿'，可能是该类型矿床成矿作用的重要形式。

An eco-environmental geochemical investigation was carried out in and around the Dexing mining area to determine the concentrations of heavy metals in the surface water, sediments, soils and plants. The main objective of this study is to assess the environmental situation and evaluate the transferring of heavy metals from mining activities into the food chain. Some samples of water, sediment, topsoil and plant were collected along the Lean River in the Dexing mining area. The total concentrations of Cu, Pb, Zn, Cd, and As were determined by AAS, and Hg was analyzed by cold-vapor AAS. Some indices such as ‘contamination degree’, ‘geoaccumulation index’, and ‘biological absorption coefficient’ were used to assess eco-environmental quality. The investigation indicated a highly localized distribution pattern closely associated with the two pollution sources along the Le' an, River bank: one is strong acidity and a large amount of Cu in the drainage from the Dexing Cu mining area; and the other is the high concentrations of Pb and Zn in the effluents released from many smelters and mining, processing and extracting activities in the riparian zone. Results from the investigated localities indicated, at least in part, that some problems associated with environmental quality deterioration should be solved in the future.

Analyses of fluid-inclusion leachates from ore deposits show that Na/Br ratios are within the range of 75–358 and Cl/Br 67–394, respectively, and this variation trend coincides with the seawater evaporation trajectory on the basis of the Na/Br and Cl/Br ratios. The average Cl/Br and Na/Br ratios of mineralizing fluids are 185 and 173 respectively, which are very close to the ratios (120 and 233 ) of the residual evaporated seawater past the point of halite precipitation. It is suggested that the original mineralizing brine was derived from highly evaporated seawater with a high salinity. However, the inclusion fluids have absolute Na values of 69.9-2606.2 mmol kg-1 and Cl values of 106.7-1995.5 mmol kg-1. Most of the values are much less than those of seawater: Na, 485 mmol kg-1 and Cl, 566 mmol kg-1, respectively; the salinity measured from fluid inclusions of the deposits ranges from 2.47 wt% to 15.78 wt% NaCl equiv. The mineralizing brine has been diluted. The δ18O and δD values of ore-forming fluids vary from −8. 21% to 9. 51% and from −40. 3% to −94.3%, respectively. The δD values of meteoric water in this region varied from −80% to −100% during the Jurassic. This evidenced that the ore-forming fluids are the mixture of seawater and meteoric water. Highly evaporated seawater was responsible for leaching and extracting Pb, Zn and Fe, and mixed with and diluted by descending meteoric water, which resulted in the formation of ores.

Mining and smelting activities are the main causes for the increasing pollution of heavy metals in soil, water body and stream sediment. An environmental geochemical investigation was carried out in and around the Panzhihua mining and smelting area to determine the extent of chemical contamination in soil and sediment. The main objective of this study was to investigate the environmental geochemistry of Ti, V, Cr, Mn, Cu, Pb, Zn and As in soil and sediment and to assess the degree of pollution in the study area. The data of heavy metal concentrations reveal that soils and sediments in the area have been slightly contaminated. Geochemical maps of Igeo of each heavy metal show that the contaminated sites are located in V-Timagnetite sloping and smelting, gangues dam. The pollution sources of the selected elements come mainly from dusts resultant from mining activities and other three-waste-effluents. The area needs to be monitored regularly for trace metal, especially heavy metal enrichment.

In the Tuoshi oilfield, located in the Cenozoic Jianghan Basin of southeastern China, there have been found hydrocarbon reservoirs hosted in lacustrine sandstones of the Eogene Xingouzui Formation. The main diagenetic features identified in these sandstones include the dissolution of detrital K-feldspar and albite grains, the precipitation of quartz as overgrowths and/or cements, and the precipitation and/or transformation of clay minerals. These diagenetic features were interpreted to have occurred in early, intermediate and late stages, based on the burial depth. The kinetics of fluid-mineral reactions and the concentrations of aqueous species at each stage of diagenesis were simulated numerically for these lacustrine sandstones, using a quasi-stationary state approximation that incorporates simultaneous chemical reactions in a time-space continuum. During the early diagenetic stage, pore fluid was weakly acidic, which resulted in dissolution of K-feldspar and albite and, therefore, led to the release of K+, Na+, Al3+ and SiO2(aq) into the diagenetic fluid. The increased K+, Na+, Al3+ and SiO2(aq) concentrations in the diagenetic fluid caused the precipitation of quartz, kaolinite and illite. At the beginning of the intermediate diagenetic stage the concentration of H+ was built up due to the decomposition of organic matter, which was responsible for further dissolution of K-feldspar and albite and precipitation of quartz, kaolinite, and illite. During the late diagenetic stage, the pore fluid was weakly alkaline, K-feldspar became stable and was precipitated with quartz and clay minerals. When the burial depth was greater than 3000 m, the pore fluids became supersaturated with respect to albite, but undersaturated with respect to quartz, resulting in the precipitation of albite and the dissolution of quartz. The diagenetic reactions forecasted in the numerical modeling closely matched the diagenetic features identified by petrographic examination, and therefore, can help us to gain a better understanding of the diagenetic processes and associated porosity evolution in sandstone reservoirs.

A total of 31 topsoil samples were systematically collected from the Panzhihua mining area including steel smelting, coal mining, urban and rural districts. A normalization procedure was adopted to establish the environmental geochemical baseline models for this area. By using the above baseline models, the regional geochemical baseline values of As, Cr, Cu, Ni, Pb and Zn were determined. On the basis of the baselines, the enrichment factors were used to analyze the mechanism of trace metal pollution in topsoil from anthropogenic sources, and the results showed that the serious trace metal pollution is caused by human activities in coal mine, iron mine, smelting factory, tailing dam and other industrial districts in the Panzhihua area.

Quartz was studied with respect to its silicon isotopic composition and cathodoluminescence in micro-fine disseminated gold deposits in SW Guizhou and NW Guangxi. The results showed that quartz in wall rocks, ores and that in association with hydrothermal silicification are distinctive in silicon isotopes and cathodoluminescence characters. Quartz in association with primary silicification is non-luminescent while that in wall rocks and associated with secondary silicification exhibits striking luminescence. Based on the dynamic fractionation of silicon isotopes, it is suggested that the mineralization was accompanied by rapid transport of a primary siliceous fluid along the major deep fault system into subordinate faults before ore components deposited in favorable strata via penetration and metasomatism. Therefore, a deep origin is implicit for gold deposits of this type.

This study focuses on the thermodynamics of diagenetic fluid from the Eogene Xingouzui Formation which represents the most important reservoir in Field Oil T in the Jianghan Basin. The measured homogenization temperatures (110–139 °C) of fluid inclusions in diagenetic minerals fell within the range of 67 –155 °C at the middle diagenetic stage. The pressure of diagenetic fluid is estimated at 10.2 –56 MPa. The activity of ions in the fluid shows a tendency of Ca2+ > Mg2+ > Na+ > K+ > Fe3+ > Fe2+ for cations, and HCO 3 − > SO 4 2− > F− > Cl− > CO 3 2− for anions. For the gaseous facies, there is a tendency of CO2> CO> H2S> CH4> H2. According to the thermodynamic calculations, the pH and Eh of the fluid are 5.86–6.47 and −0.73–−0.64V, respectively. As a result of the interaction between such a diagenetic fluid and minerals in the sediments, feldspars were dissolved or alterated by other minerals. The clay mineral kaolinite was instable and hence was replaced by illite and chloritoid.