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51.
拉拉铜矿黄铁矿微量元素地球化学特征及其成因意义 总被引:6,自引:0,他引:6
四川会理拉拉铜矿床是我国著名大型富铜矿床,针对该矿床中黄铁矿的微量元素、稀土元素地球化学分析表明:拉拉铜矿经历了早期火山喷发成岩成矿和晚期变质成岩成矿作用.条带状矿石中的黄铁矿Co/Ni比值集中于4.92~79.2之间,落入火山成因黄铁矿区,稀土元素分布具有Eu正异常和轻稀土富集的特征,反映矿床具有伴随河口群火山喷流沉积成岩过程的同生沉积成矿作用.脉状矿石中的黄铁矿Co/Ni比值集中于1.10~3.45,落在热液成因黄铁矿区,稀土元素较河口群岩石及其他典型块状硫化物矿床矿石稀土元素更加富集轻稀土元素,稀土含量变化范围更大,显著的负Eu异常,则又说明,矿床形成的主要成矿作用是伴随新元古代晋宁运动而发生的大规模的变质作用. 相似文献
52.
通过对塔东地区古城4井上寒武统和中、上奥陶统碳酸盐岩围岩及充填物的碳、氧、锶同位素地球化学和流体包裹体成分的对比研究表明,充填于中、上奥陶统和上寒武统的流体分属于2个不同来源的流体体系。充填于中、上奥陶统灰岩裂缝中方解石脉的w(87Sr)/w(86Sr)介于0.7084~0.7088,它与早奥陶世海水的w(87Sr)/w(86Sr)相近;流体体系为CH4-H2O体系;充填物与围岩间具有明显的碳、氧同位素差异,表明上部流体体系中的流体来自于奥陶系地层本身。上寒武统白云岩裂缝中方解石脉的w(87Sr)/w(86Sr)为0.7138,明显地高于同时代海水的锶同位素值;流体体系为CO2-H2O体系;下部流体体系中的流体为外来富锶流体。上、下流体体系间互不连通暗示着上寒武统地层具有相对较好的保存条件。 相似文献
53.
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55.
The characteristics and sources of natural gases from Ordovician weathered crust reservoirs in the Central Gas Field in the Ordos Basin 总被引:2,自引:2,他引:0
Xianqing Li Guoyi Hu Jian Li Dujie Hou Peng Dong Zhihong Song Yunfeng Yang 《中国地球化学学报》2008,27(2):109-120
The Central Gas Field is a famous large-sized gas field in the Ordos Basin of China. However, identification of main gas sources of the Ordovician reservoirs in this gas field remains puzzling. On the basis of a lot of geochemical data and geological research on natural gases, the characteristics and sources of natural gases from Ordovician weathered crust reservoirs in the Central Gas Field in the Ordos Basin were studied. The results indicated that natural gases from Ordovician weathered crust reservoirs in the Central Gas Field in the Ordos Basin have similar chemical and isotopic compositions to highly mature and over-mature dry gases. Both coal-derived gases and oil-type gases coexist in the Central Gas Field in the Ordos Basin. The former was derived mainly from Carboniferous-Permian coal measures and the latter from Lower Paleozoic marine carbonates. It is suggested that coal-derived gases occur in the eastern part of the Central Gas Field while oil-type gases may be produced mainly in the northern, western and southern parts of the Central Gas Field in the Ordos Basin. 相似文献
56.
Hang Li Dahua Li Tangfu Xiao Libin He Zengping Ning Jialong Sun Changsheng Zhu Yan Shuang 《中国地球化学学报》2008,27(1):21-27
The Jinding Pb-Zn deposit in Yunnan Province is the representative of a Cd-enriched area and mining activities lead to the release of Cd into the hypergenic ecosystem, resulting in Cd pollution. The concentrations of Cd vary greatly from one type to another type of rocks in the mining district. In the host rock, Cd concentrations range from 50×10^-6 to 650×10^-6 with an average of 310×10^-6. In primary ores, Cd concentrations range from 14×10^-6 to 2800×10^-6 with an average of 767×10^-6. However, in oxidized ores, Cd concentrations are highest, varying within the range of 110×10^-6 to 8200×10^-6 , averaging 1661×10^-6. It is shown that the oxidized ores are the main carder and environmental source of Cd. Leaching test showed that Pb/Zn ores are easy to oxidize and thereafter release Cd and other harmful elements. These leached elements in the leachate may be precipitated rapidly in the order of Zn〉Pb〉Cd. As for the concentration distribution of Cd in the Bijiang River, it is estimated to be 15.7 μg/L Cd in water, 49.3 mg/L in suspended substances, and 203.7 mg/L in sediments. The average value of Cd in soil from the polluted area is 83.0 mg/kg. Natural weathering of Cd-rich rocks and minerals imposes a potential environmental risk on the aquatic ecosystem of the Bijiang catchment. 相似文献
57.
Extensive organic-matter (OM) rich facies (black shales) occur in the Ordo-Silurian boundary successions in the Yangtze area, South China. To investigate the redox changes of the Yangtze Sea during the Ordo-Silurian transition, two OM sections (Wangjiawan in Yichang, Hubei Province, and Sanjiaguan in Zhangjiajie, Hunan Province) straddling the Ordo-Silurian boundary are studied. The measurements finished in this study include contents of the total organic carbon (TOC), pyrite sulphur, and different species of Fe, including dithionite-extractable Fe (FED), pyrite Fe (FeP), HCl-extractable Fe (FeH), and total Fe (FeT), in black shales, as well as other redox proxies, such as the SIC ratio, the ratio between highly reactive Fe (FeHR = FeD + FeP) and FeT, and the FeP/(FeP + FeH) ratio, known as the degree of pyritization (DOP). In the Wangjiawan section, the Middle Ashgill sediments have high FeHR/FeT ratios (0.20-0.77; avg. 0.45), high DOP values (0.21-0.72; avg. 0.54), and a relatively constant sulfur content independent of the organic carbon content. By the contrast, the mid-early Hirnantian deposits generally have low FeHR/FeT ratios (0.10-0.35; avg. 0.21), low DOP values (0.11- 0.40; avg. 0.28), and SIC values are clustering on the normal marine value (SIC = 0.36). The late Hirnantian and early Rhuddanian deposits, similar to those of the Middle Ashgill deposits, are characterized by high FeHR/FeT ratios (0.32-0.49; avg. 0.41), high DOP values (0.46-0.68; avg. 0.53) and fairly constant sulfur contents. These data suggest the occurrences of marine anoxia on the Yangtze Sea shelf during intervals of the Mid Ashgill, Late Hirnantian and Early Rhuddanian, and ventilated and oxygenated marine conditions during the mid-early Hirnantian time. The mid-early Hirnantian ventilated event was concomitant with the global glacial period, likely resulted from the glacio-eustatic sea-level fall and subsequent circulation of cold, dense oxygenated waters 相似文献
58.
大金山铅锌矿位于泰宁一政和北东东向铜多金属成矿带上,是该成矿带主要的矿种之一,也是闽北地区一个较有价值的矿床。矿床产于早元古代南山组上段,受燕山期北东东向构造控制,属中低温热液充填交代型矿床。 相似文献
59.
Elisa Sacchi Gian Maria Zuppi Luca Pizzino Fedora Quattrocchi Salvatore Lombardi 《Aquatic Geochemistry》2008,14(4):301-319
The EC funded Geochemical Seismic Zonation program (EEC GSZ Project 1996–1998) chose Sardinia as a low-seismicity site, in which the relationships between fluid geochemistry and seismo-tectonics
had to be investigated and results compared with outcomes from other selected high-seismicity sites. A first article, examining
the role of fault segmentation and seismic quiescence on the geochemical composition of groundwaters and gases, has already
been presented (Angelone et al. 2005). This article deals with environmental isotopes which, together with selected hydrochemical data, give hints on tectonically-related
fluid circulations. Four water-dominated hydrothermal systems were considered, all located along regional fault systems and
discharging groundwaters belonging to the Na–HCO3 and Na–Cl facies. In the considered systems, groundwater circulation takes place, principally, in the Palaeozoic Crystalline
Basement (PCB), with the exception of the Logudoro system, where hydrological circuits develop in the Mesozoic Carbonate Platform
(MCP). The high CO2 contents, the non-attainment of fluid-rock equilibrium and the large lithological variability prevent the construction of
a unique hydrogeological–geochemical conceptual model. In this case, stable isotopes provide a useful tool to describe the
origin of fluids and their subterranean movements. Stable isotopes of water, integrated with hydrochemical data, indicate
that fluids are derived from three main end members. The dominant component is a relatively recent local meteoric water; the
second one is marine water; and the third one is a fossil freshwater, depleted in heavy isotopes with respect to modern rains.
The latter end member entered the aquifer system in the past, when climatic conditions were greatly different from today.
At least two circulation systems can be recognised, namely a shallow cold system and a deep hydrothermal system, as well as
two distinct hydrological processes: (1) gravity-controlled descent of cold water towards greater depths and (2) convection
linked to a thermal gradient, causing deep fluids to rise up from the hydrothermal reservoir towards the surface. The highly
variable δ13CTDIC values suggest the presence of two distinct CO2 sources, namely, a biogenic one and a thermogenic one. The relation between the isotopic compositions of CO2 and He indicates an increased mantle signature in uprising CO2-rich fluids. 相似文献
60.
We propose a methodology, called multilevel local–global (MLLG) upscaling, for generating accurate upscaled models of permeabilities
or transmissibilities for flow simulation on adapted grids in heterogeneous subsurface formations. The method generates an
initial adapted grid based on the given fine-scale reservoir heterogeneity and potential flow paths. It then applies local–global
(LG) upscaling for permeability or transmissibility [7], along with adaptivity, in an iterative manner. In each iteration of MLLG, the grid can be adapted where needed to reduce
flow solver and upscaling errors. The adaptivity is controlled with a flow-based indicator. The iterative process is continued
until consistency between the global solve on the adapted grid and the local solves is obtained. While each application of
LG upscaling is also an iterative process, this inner iteration generally takes only one or two iterations to converge. Furthermore,
the number of outer iterations is bounded above, and hence, the computational costs of this approach are low. We design a
new flow-based weighting of transmissibility values in LG upscaling that significantly improves the accuracy of LG and MLLG
over traditional local transmissibility calculations. For highly heterogeneous (e.g., channelized) systems, the integration
of grid adaptivity and LG upscaling is shown to consistently provide more accurate coarse-scale models for global flow, relative
to reference fine-scale results, than do existing upscaling techniques applied to uniform grids of similar densities. Another
attractive property of the integration of upscaling and adaptivity is that process dependency is strongly reduced, that is,
the approach computes accurate global flow results also for flows driven by boundary conditions different from the generic
boundary conditions used to compute the upscaled parameters. The method is demonstrated on Cartesian cell-based anisotropic
refinement (CCAR) grids, but it can be applied to other adaptation strategies for structured grids and extended to unstructured
grids. 相似文献