Multi-Origin of Dolomite in Lower Ordovician Tongzi Formation of Sichuan Basin, Western China

被引：0
|
作者：
Liu Z. [1 ,2 ]
Xing F. [1 ,2 ]
Hu H. [1 ,2 ]
Chen X. [1 ,2 ]
机构：
[1] State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu
[2] Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu
来源：
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | 2021年 / 46卷 / 02期
关键词：
Dolomitization mechanism; Lower Ordovician; Petroleum geology; Sichuan Basin; Tongzi Formation; Upper Yangtze region;
D O I：
10.3799/dqkx.2020.026
中图分类号：
学科分类号：
摘要：
The origin of dolomite in Tongzi Formation of Lower Ordovician in Sichuan Basin has been studied less, and there are various models, and no consensus has been reached. Through the system's core observation, thin slice identification, geochemical analysis and other methods, dolomite-related rock types such as dolomite, granular dolomite and quartz dolomite and dolomitic quartz sandstone are identified in the Tongzi Formation of the Sichuan Basin. Geochemical analysis reveals different geochemical characteristics and different dolomitization mechanisms of different types of dolomite. MgO and CaO values of grain dolomite show obvious positive correlation, with relatively high δ18OPDB value, δ13CPDB value, Sr value and higher Mg/Ca ratio, and lower Fe and Mn values, which is considered to be the cause of dolomite evaporation pump dolomitization. Class A containing quartz dolomite and dolomitic quartz sandstone has similar geochemical characteristics to grain dolomite, and also formed in the quasi-simultaneous period of dolomitization. The MgO and CaO contents of the granular dolomite show a weak negative correlation. The δ13CPDB value and the δ18OPDB value are basically consistent with the distribution range of seawater carbon and oxygen isotope values. The Sr content is relatively high, which is considered to be the cause of reflux infiltration of dolomitization. Class B containing quartz dolomite and dolomitic quartz sandstone develops only in the local area near the provenance, and the contents of MgO and CaO are positively correlated. The δ13CPDB value and the δ18OPDB value show a significant negative bias. Compared with other two types of dolomite, Class B has higher Al2O3, Fe, Mn contents and relatively lower Sr content, and are affected by the mixing of terrestrial debris. In summary, it is believed that it is the dolomitization of mixed water. The Tongzi Formation in the Sichuan Basin has coexistence characteristics of three types of dolomitization, and the mechanism of the Upper Cambrian dolomitization is inherited. © 2021, Editorial Department of Earth Science. All right reserved.
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页码：583 / 599
页数：16
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