上扬子地区下寒武统海相富有机质页岩形成环境与主控因素分析

Formation Environment and Controlling Factors of Organic-rich Shale of Lower Cambrian in Upper Yangtze Region

对上扬子地区下寒武统富有机质页岩发育主控因素的研究是进行该区页岩气勘探有利区预测的基础问题之一。通过对上扬子地区下寒武统黑色页岩典型露头剖面样品特征的分析,运用岩石、矿物、有机质特点、特征元素等指标对该区海相富有机质页岩在早寒武世时的古环境进行恢复,建立上扬子地区下寒武统海相富有机质页岩沉积环境判别综合表,认为该套黑色页岩在早寒武世是典型的缺氧环境。上扬子地区下寒武统富有机质页岩的发育是古构造、古气候和古海平面变化、古洋流及海底热液活动等因素综合作用的结果。建立了上扬子地区古海平面上升―上升洋流―热液活动―水体分层―缺氧环境的页岩发育模式,指出海底热液活动和上升洋流促进生物体的勃发,为富有机质页岩形成提供物质基础;海平面上升和上升洋流不仅造成水体分层,而且共同影响富有机质页岩的分布范围。

The research of controlling factors on organic-rich shale of Lower Cambrian in Upper Yangtze region is one of the basic questions for forecasting favorable shale gas exploration area. Through analyzing samples of typical organic-rich black shale outcrop profile in Upper Yangtze region, the Early Cambrian paleo-environment of marine organic-rich in Upper Yangtze region is restored and the depositional environment comprehensive dis- tinguished table is established using information from rocks, minerals, organic matter charactersics, feature elements. In Early Cambrian, the black shale is formed in a typical hypoxia. The Lower Cambrian black shale of Upper Yangtze region is a combined result of paleostrueture, paleoclimate, sea level changes, paleoocean currents and hydrothermal activity, and so on. The shale development model of sea level-ascending current- hydrothermal activity-stratified water bodies-hypoxia is built. Hydrothermal activity and ascending current pro- mote the organisms to thrive and provide the material basis for the formation of organic-rich shale. Rising sea level and ascending current not only lead to stratified water bodies, but also affect the distribution range of or- ganic-rich shale.