LUO Hou-yong1,2,3,4, LIU Wen-hui3,4, WANG Wan-chun1, TENGER3,4, FAN Ming3,4, HAN Yuan-hong1,2
1. Key Laboratory of Petroleum Resource Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000, China;
2. University of Chinese Academy of Sciences, Beijing 100049, China;
3. SINOPEC Key Laboratory of Petroleum Accumulation Mechanisms, Wuxi 214151, China;
4. Wuxi Institute of Petroleum Geology, SINOPEC, Wuxi 214151, China
Abstract: We carried out mineralogical analyses to understand the causes of anhydrite-pyrite-calcite veins in the black shales of the Ordovician Wufeng formation, Pengshui area, Sichuan Basin. It is shown that anhydrites are remnants of the original anhydrite dissolution, pyrite develops in both parallel sides with a symmetrical distribution, and its crystal size and integrity are constantly changing from center to edge, and calcite crystals are secondary euhedral. These features indicate that the black shale occurred TSR in the past. Anhydrite dissolution could provide the required sulfate ions, organic matter and the product of black shale evolution could provide reducing agent, hydrogen sulfide formed from TSR and iron could generate pyrite which distributes along the veins, and calcite precipitation was mainly due to ore fluids. All of these broaden the scope of occurring hydrocarbon fluids TSR in the high evolutionary stage, prove that TSR could develop widely in geological conditions, and enhance understanding of formations of oil and gas in marine strata.
Keywords: anhydrite pyrite calcite Wufeng formation thermochemical sulfate reduction
*Corresponding Author, E-Mail: whliu.syky@sinopec.com
Bulletin of Mineralogy, Petrology and Geochemistry Vol. 34, No.2, 2015, page 330-333
