Oxygen and Carbon Isotopic Composition of Carbonate Rocks of the Permian Qixia Formation, Sichuan Basin: Thermal Effects of Emeishan Basalt

Earth Sciences Research Journal

Keke, Huang¹  Yijiang, Zhong¹  Xiaoning, Li¹  Zuowei, Hu¹ 

[1] Laboratory of Oil and Gas Reservoir Geology and Exploitation, China$$Chengdu University of Technology, China$$

关键词: Sichuan Basin;    Qixia Formation;    Carbon and Oxygen Isotopic Composition;    Thermal Effect.;   

DOI  :  10.15446/esrj.v20n1.52403

学科分类：天文学(综合)

来源: Universidad Nacional de Colombia * Departamento de Geociencias

【 摘 要 】

The late Permian thermal events related to Emeishan Basalt has made a great impact on the underlying carbonate rock properties in the western margin of the Yangtze Platform. In this paper, we investigate the carbon and oxygen isotopic composition of the Qixia Formation carbonates from two sections: the Qiaoting Section in the northeastern part of the Sichuan Basin and the Changjianggou Section at the northwestern edge of the Basin. The data reveal that: (i) Samples from Qiaoting section show a relatively narrow range of δ¹³C and δ¹⁸O, varying from 2.7‰ to 5.2‰ with an average of 4.2‰, and -3.8‰ to -7.8‰ with an average of -5.4‰, respectively. In contrast, Samples from Changjianggou section exhibit larger magnitude of variation in δ¹³C and δ¹⁸O, ranging from -1‰ to 3.8‰ with an average of 1.5‰, and -2.1 to -9.2‰, with an average of -6.0‰ respectively; (ii) δ¹³C and δ¹⁸O records in carbonates from Qiaoting section are similar to those of Middle Permian seawater whereas carbonates from the Changjianggou section are depleted in ¹³C and ¹⁸O compared to contemporary seawater; (iii) On the basis of combined petrographic and paleo-heat flow evidence, the lower carbon and oxygen isotopic composition of the carbonates from the Changjianggou section are interpreted to be the results of thermal effects of Emeishan Basalt because of its proximity to the eruption center of the basalt. The high temperature reduced the δ¹⁸O values of the carbonates and forced the organic matter to mature at an early stage, thus producing ¹³C-enriched carbon dioxide to participate in the formation of carbonates.

【 授权许可】

Unknown