塔里木盆地奥陶系碳酸盐岩碳氧同位素组成及流体来源讨论

奥陶系碳酸盐岩储层是塔中地区重要的油气产层．测定塔里木盆地奥陶系热液矿物（方解石、石膏、重晶石等）及围岩的碳氧同位素以及锶同位素，分析结果显示，热液溶蚀围岩后释放的CO2可能是形成方解石中特征氧同位素组成的主控因素；自生碳酸岩矿物的碳同位素组成反映其在成岩期至少有2种碳源，早期形成的碳酸盐岩与二叠纪富^13C的碳源相关，成岩早期至晚期的碳酸盐岩的沉淀或重结晶可能与由局部地质事件导致流体在沿裂缝系统运移时混合了有机质降解过程中产生的富^13C的CO2有关；^87Sr／^85Sr值（0．708-0．718）高于同期海水，说明是该区域的热液流体富。^87Sr值的特征．

C-O,Sr isotope composition of the carbonate in Ordovician in Tarim Basin and implication on fluid origin

Carbonate reservoir in Ordovician is an important hydrocarbon reservoir. Determining the carbon and oxy- gen isotopic rations of the hydrothermal minerals in Tarim Basin, and the result shows that, δ^18O value of calcite is negative , hence the main factor of the oxygen isotopic value due to the CO2 derived from the wallrock which was corroded by the hydrothermal fluid. The δ^13C value of the authigenic carbonate implying two carbon source during diagenesis, ^13C-rich carbon source are attributed to early carbonate in Permian, deposit or recrystallization during early to late stage authigenic carbonate formation related to ^12 C-rich CO2 produced by organic matter degradation as fluid going throw the fracture system; ^87 Sr/^86 Sr value（0. 708-0. 718） is higher than the seawater at the same stage, which implys the local hydrothermal fluid are in ^87 Sr-rich.