【摘要】 富有机质黑色页岩的形成长期以来被认为是缺氧沉积环境的证据,并被作为全球缺氧事件的标志。塔里木盆地下寒武统底部黑色页岩的岩石学特征说明其沉积在受陆源有一定影响的陆棚环境中。矿物学研究表明,硫均以硫酸盐状态存在,没有见到黄铁矿,说明其形成在硫酸盐还原带以上。黑色页岩中结核状氟磷灰石的存在以及剖面底部结核状磷块岩的出现,表明了一种与现代热带太平洋东海岸和阿拉伯海相类似的广泛发育上升洋流的大陆边缘沉积环境。黑色页岩的地球化学特征中,Re和Mo的高度富集、高的Re/Mo比以及含有一定量的Mn,Cd和U的相对富集以及低的Cd/U比等,这些特点均支持了黑色页岩沉积于次氧化条件的认识。更多还原

【Abstract】 Black shales have been considered as a sign of anoxic depositional environments and anoxic e-vents for a long time. The petrologic characteristics of black shales in Lower Cambrian from northern Tarim Basin show that the black shales were deposited on a shelf affected by the terrigenous sources to some extent. The study of mineralogy indicates that the sulfur occurs in sulfates, such as gypsum and barite, instead of in sulfide, such as pyrite, suggesting that the black shales were deposited in the environment above the sulfate reduction zone. The occurrence of nodular fluorapatite aggregates in the black shales and nodular phosphorites at the bottom of the black shale section shows that they were deposited in such a continental margin environment that the upwelling was developed widely as those along contemporary eastern tropical Pacific and Arabian Sea. The enrichment of Re, Mo, Cd and U, high Re/Mo and low Cd/U ratios in the black shales are all consistent with the suboxic depositional setting.更多还原