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综合运用岩石学、矿物学和元素地球化学等方法,对柴达木盆地北缘冷湖五号构造带中新统上干柴沟组碎屑岩的成岩作用、形成环境和物质来源等进行了系统研究。发现上干柴沟组碎屑岩颗粒间主要以点—线接触为主,颗粒间云母等塑性岩屑被挤压变形,说明经历过较强的压实作用。黏土矿物含量较高,平均达到了22.74%,主要以伊利石、绿泥石及伊/蒙混层为主。碳酸盐胶结物类型主要以方解石为主,仅含有少量白云石。碳酸盐胶结物的碳氧同位素含量测定表明,碳同位素(δ13C)值分布范围在-6.88‰~-3.8‰之间,平均为-5.39‰;氧同位素(δ18 O)值分布范围在-12.74‰~-6.98‰之间,平均为-10.18‰;根据碳氧同位素含量推算古盐度Z值分布范围为107.65~114.89,平均值为111.34;碳酸盐沉淀温度分布范围为52.34~88.93℃,平均值为72.08℃。结合对主量元素、微量元素及有机碳含量等地球化学元素的综合分析,冷湖五号构造带中新统上干柴沟组储集岩目前所处的成岩阶段主要为早成岩阶段B期至中成岩阶段A期,在沉积时期气候稳定且温暖湿润。
Using the methods of petrology, mineralogy and elemental geochemistry, the diagenesis, formation environment and material source of clastic rocks in the Upper Ganchaigou Formation of the Miocene in the Lenghu No.5 tectonic zone on the northern margin of the Qaidam Basin were studied system Research. It is found that the clastic rocks in the Upper Ganchaigou Formation mainly consist of point-line contact, and the plastic cuttings such as intergranular mica are squeezed and deformed, indicating that they have undergone strong compaction. Clay mineral content is higher, with an average of 22.74%, mainly in illite, chlorite and Iraq / mixed layer. Carbonate cements are mainly calcite-based, containing only a small amount of dolomite. Carbon and oxygen isotopic compositions of carbonate cements show that the distribution of δ13C value ranges from -6.88 ‰ to -3.8 ‰, with an average of -5.39 ‰, and the δ18O values range from -12.74 ‰ ~ -6.98 ‰, with an average of -10.18 ‰. According to the content of carbon and oxygen isotopes, the distribution of Z value of ancient salinity ranged from 107.65 to 114.89 with an average value of 111.34. The carbonate precipitation temperature ranged from 52.34 to 88.93 ℃, The average is 72.08 ° C. Based on the comprehensive analysis of the major elements, trace elements and organic carbon, the diagenetic stages of the Miocene Shanggan Chaigou Formation reservoir in the Lenghu No.5 structural belt are mainly composed of the early diagenetic stage B To the middle diagenetic stage A, during the deposition period the climate is stable and warm and humid.