Genesis and Environment Characteristics of Dolomite-Hosted Quartz and Its Significance for Hydrocarbon Exploration,in Keping Area,Tarim Basin,China  

作　　者：邢凤存 李思田 

机构地区：[1]Institute of Sedimentary Geology,Chengdu University of Technology [2]State Key Laboratory of Oil/Gas Reservoir Geology and Exploitation [3]Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education,China University of Geosciences [4]School of Energy Resources,China University of Geosciences

出　　处：《Journal of Earth Science》2012年第4期476-489,共14页地球科学学刊（英文版）

基　　金：supported by the SINOPEC Forward Looking Project of China (No. YPH08114)

摘　　要：A great amount of quartz was found filling vugs of the dolomite strata of Upper Cambrian-Lower Ordovician in Keping （柯坪） outcrop area of Tarim basin, China, which is widely distributed with obvious impact on dolomite reservoirs. The quartz＇s genesis and environment were studied based on careful field observation and indoor comprehensive analysis. The abnormal high temperature of the primary saline aqueous inclusions of quartz minerals might reach as high as 578 °C, showing the characteristics of basin abnormal heat events. The quartz-rare earth element （REE） pattern is similar to those of the granite, diabase, and basalt of Permian in Tabei （塔北） area. According to the regional geological setting and quartz＇s distribution as well as its occurrence, the genesis of quartz is attributed to Permian magmatic activity-related hydrothermal liquid instead of the primary marine sedimentary genesis or regional metamorphic genesis. The 813C values of CO2 in the quartz inclusions range from -1.4‰ to -4.6‰, which might derive from the mantle, while 6180 of SiO2 indicates a hot fluid genesis of meteoric precipitation, which consists of the meteoric precipitation diagenetic setting of C and O isotopes in the dolomite host rocks and the low-medium salinity freshwater condition in the inclusions. REEs must have experienced clear differentiation, since the values of LREE/HREE are all over 1, clearly indicating the characteristic of enrichment of LREE and decrement of HREE. Ce has no obvious anomaly and Eu has clear negative anomalies, which suggests a reducing environment when the quartz crystallized. After the comprehensive analysis, we believe that quartz is a product ofsiliceous hydrothermal liquids in combination with meteoric precipitation under a reducing environment. Additionally, the precipitation hydrothermal fluid mixture might have also mixed thoroughly with the formation water and exchanged material with the host dolomites. The significance of siliceous hydrothermal fluids for dolomite reserA great amount of quartz was found filling vugs of the dolomite strata of Upper Cambrian-Lower Ordovician in Keping （柯坪） outcrop area of Tarim basin, China, which is widely distributed with obvious impact on dolomite reservoirs. The quartz＇s genesis and environment were studied based on careful field observation and indoor comprehensive analysis. The abnormal high temperature of the primary saline aqueous inclusions of quartz minerals might reach as high as 578 °C, showing the characteristics of basin abnormal heat events. The quartz-rare earth element （REE） pattern is similar to those of the granite, diabase, and basalt of Permian in Tabei （塔北） area. According to the regional geological setting and quartz＇s distribution as well as its occurrence, the genesis of quartz is attributed to Permian magmatic activity-related hydrothermal liquid instead of the primary marine sedimentary genesis or regional metamorphic genesis. The 813C values of CO2 in the quartz inclusions range from -1.4‰ to -4.6‰, which might derive from the mantle, while 6180 of SiO2 indicates a hot fluid genesis of meteoric precipitation, which consists of the meteoric precipitation diagenetic setting of C and O isotopes in the dolomite host rocks and the low-medium salinity freshwater condition in the inclusions. REEs must have experienced clear differentiation, since the values of LREE/HREE are all over 1, clearly indicating the characteristic of enrichment of LREE and decrement of HREE. Ce has no obvious anomaly and Eu has clear negative anomalies, which suggests a reducing environment when the quartz crystallized. After the comprehensive analysis, we believe that quartz is a product ofsiliceous hydrothermal liquids in combination with meteoric precipitation under a reducing environment. Additionally, the precipitation hydrothermal fluid mixture might have also mixed thoroughly with the formation water and exchanged material with the host dolomites. The significance of siliceous hydrothermal fluids for dolomite reser

关 键 词：GENESIS QUARTZ GEOCHEMISTRY hydrothermal fluid DOLOMITE Tarim basin. 

分 类 号：P618.13[天文地球—矿床学]