2016年2期

秭归五龙地区五峰组-龙马溪组黑色岩系地球化学特征及其页岩气地质意义

发布时间:2016-09-05阅读次数:

【期数】2016-2

【作者】危 凯,陈孝红,周 鹏,张保民

【机构】中国地质调查局武汉地质调查中心,武汉 430205

【关键词】秭归;五龙;五峰组—龙马溪组;黑色岩系;微量元素;页岩气

【中文摘要】对湖北秭归县五龙剖面五峰组-龙马溪组下段黑色岩系的微量元素和有机碳含量进行了系统采样分析,结果表明,U/Th、Ni/Co、V/Cr 和V/Sc比值等判别指标能够很好的响应各时期氧化还原条件和海平面的变化,对奥陶系-志留系界线附近的地层缺失也有明显的指示作用。另外,U/Th、Ni/Co、V/Cr和V/Sc比值与TOC值之间表现出良好的正相关关系,表明这些古环境判别指标在一定程度上可用来指示五峰组和龙马溪组的有机碳含量变化。通过对五龙剖面及周边地区富有机质页岩厚度、TOC值和含气性的对比分析,推断五龙地区和西侧的鼓锣坪地区、东侧的九畹溪地区构成隆凹相间的格局,这一认识对区域内的页岩气有利目标区预测具有一定的指导意义。

【英文摘要】Trace elements and TOC of black shale in Wufeng – Longmaxi Formation from Wulong section in Zigui County, Hubei Province, are analyzed. The results show that the U/Th, Ni/Co, V/Cr and V/Sc ratios can indicate the variation of redox conditions and sea level, as well as the strata loss at Ordovician-Silurian boundary. In addition, the notable positive correlations between U/Th, Ni/Co, V/Cr, V/Sc ratios and TOC values suggest that these redox-sensitive indexs can indicate the TOC variation of Wufeng – Longmaxi Formation. By comparing the consecutive thickness of organic-rich shale, TOC values and gas-bearing of Wulong section and its adjacent region, we suggest that there exists a paleogeographic framework with alternating uplifts and depressions in Wulong, Guluoping and Jiuwanxi area. The conclusion may be of significance to predict the potential development area of shale gas in the region.

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