海底热液活动与富有机质烃源岩发育的关系 ——以黔西北地区下寒武统牛蹄塘组为例

为明确海底热液活动对黔西北地区下寒武统牛蹄塘组黑色页岩有机质富集的影响,在综合中外热液成矿研究成果的基础上,结合沉积地球化学与有机地球化学的测试资料,重点研究了海底热液活动特征元素与烃源岩有机质丰度的相关关系;通过2组沉积环境相似但受热液活动影响明显不同的剖面样品对比,对当时的古生产力和氧化还原环境进行了恢复。距离热液喷口较近的温水村剖面受到热液活动的影响强烈,特征元素大量富集;而较远的毛捭村剖面由底部到顶部受到热液活动的影响明显减弱。在恢复古海洋生产力中发现非陆源Ba(热液成因与生物成因总和)含量与有机碳含量有很好的相关关系,证明热液活动确实参与了海洋中生物的生命活动,从而认为热液活动可以为海洋生物的发育提供物质基础并提高古生产力。随着底层还原—酸性的热液流体的注入,在大环境为还原环境的情况下更加深了牛蹄塘组底部的缺氧程度,改善了有机质保存条件。热液活动为黔西北地区下寒武统牛蹄塘组黑色页岩提供了必要的物质基础和保存条件,有利于形成富有机质的优质烃源岩。

Hydrothermal activities on the seafloor and evidence of organic- rich source rock from the lower Cambrian Niutitang formation, northwestern Guizhou

Black shales of the lower Cambrian Niutitang formation in the northwestern Guizhou are widespread. The research results about hydrothermal mineralization at home and abroad have been applied into the study of organic-rich black shales. The correlation between hydrothermal characteristic elements and organic matter abundance was analyzed through the sedimentary geochemistry and organic geochemistry test data. Two sets of samples from similar sedimentary environments but different in hydrothermal activities were selected. Ancient productivity and redox environment have been restored. It is proved that hydrothermal activity can provide material basis for the development of marine organisms and increase the paleoproductivity. It will also increase the degree of hypoxia in the anoxic environment and improved organic matter preservation conditions. Overall, favorable conditions can be provided for the development of the source rock.