摘要: |
石膏是柴达木盆地油气圈闭的盖层之一。根据石膏层含量统计和石膏34SV-CDT分析,发现柴达木盆地古近系石膏主要分布于靠近阿尔金山的狮子沟凹陷和小梁山凹陷,石膏含量在垂向上具有旋回性。石膏的34SV-CDT值分布范围很大,为-23.3~71.4%,属国内外罕见。其原因是来自阿尔金山的硫酸盐34S值很低,而由盆缘向盆内随着还原环境的强化,细菌的分馏作用逐渐强烈,导致34SV-CDT值的巨大差异。石膏34SV-CDT值的主控因素为硫酸盐34SV-CDT初始值、硫酸盐补给速率和还原菌分馏作用的强度。形成石膏的硫酸盐来自阿尔金山,经由狮子沟凹陷进入盆地,然后向盆地其它方向扩散。 |
关键词: 柴达木盆地 石膏 硫同位素 古近系 |
DOI: |
附件 |
投稿时间:2019-05-05修订日期:2019-05-27 |
基金项目:中国石油天然气股份有限公司重大科技专项"柴达木盆地建设高原大油气田勘探开发关键技术研究与应用"(编号:2016E-01)和国家科技专项"柴达木复杂构造区油气成藏、关键勘探技术与新领域目标优选"(编号:2016ZX05003-006)联合资助 |
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Distrbution of gypsum and sulfur isotopes in the Palaeogene strata, western Qaidam Basin, Qinghai |
ZHENG Ximin1, YANG Liu1,2, YI Dinghong1, WANG Pu1 |
(1. Northwestern Branch, Research Institute of Petroleum Exploration and Development, CNPC, Lanzhou 730020, Gansu, China; 2. China University of Petroleum, Beijing 102249, China) |
Abstract: |
The gypsoliths occur as part of the cap rocks of the oil and gas traps in the Qaidam Basin, Qinghai. In the light of the statistics of gypsum contents and 34SV-CDT values, the gypsum in the Palaeogene strata mainly occurs in the Shizigou depression and Xiaoliangshan depression near the Altun Mountains. Vertically, the gypsum contents display the cyclic distribution. The 34SV-CDT values show a rarely wide range of -23.3% to 71.4%. The initial 34S values are very low in the Altun Mountains. The increase of the reducing conditions and the fractionation of bacteria towards the Qaidam Basin leads to the great differences in the 34SV-CDT values. The main controlling factors include the initial 34SV-CDT values, supply rates of sulfates, and intensity of bacteria fractionation. It follows that the sulfates are derived from the Altun Mountains, and then enter into the Qaidam Basin through the Shizigou depression. The results of research in this study may be helpful to the study of the gypsum distribution, sedimentary environments of the Palaeogene salt lakes, and sulfate origins in the study area. |
Key words: Qaidam Basin gypsum sulfur isotope Palaeogene |