埃迪卡拉纪-寒武纪转折期风化作用-来自扬子地台（贵州）深水盆地沉积响应及地球化学约束

Ediacaran-Cambrian (E-C) occurrs on a large scale global weathering, which has a the coupling relationship on time and space with biological Global large-scale chemical weathering occurred during the Ediacaran-Cambrian (E-C) transition, which coupled temo-spatially with biological and oceanic evolutions as well as metallic super- enrichment in seawater. The Yangtze craton, notably in the Guizhou area accommodated the continuous deep basina deoposition, becoming a favourable area to conduct the study on continental weathering and effects on oceanic changes. The project takes the E-C continuous basinal deposits of chert and black shale as the target.Integrated with stratigraphy and high resolution sequence stratigraphy,with multiple geochemical approaches, particularly Mg and Os isotope geochemistry, Ge/Si ratio.This project aims to establish the high-resolution time stratigraphic-sedimentary framework and correlation scheme of basinal Ediacaran-Cambrian successions, to evaluate the coeval provenance component, weathering intensity of delivering sediments and dissolved matters deriving from the hinterlands, and potential influences on the abnormal enrichment of some elements and environmental effects in the marine basin during the E-C transition.

埃迪卡拉纪-寒武纪（E-C）全球发生了大规模风化作用，其与生物演化、金属异常富集及古海洋演化之间存在时间和空间上的耦合关系。扬子地台尤其是贵州地区，埃迪卡拉纪-寒武纪过渡地层在深水盆地内沉积连续，是良好的研究过渡时期大陆风化作用的区域。本项目以贵州深水盆地E-C连续硅质岩和黑色页岩为对象，结合已有该区域年代地层学、岩石地层学、生物地层学已有成果，建立斜坡相带和盆地相带留茶坡组沉积岩石学对比格架。通过主微量（Ge\Si值）、稀土地球化学、Mg、Os同位素等地球化学方法，对深水相沉积剖面风化强度示踪，定量计算陆源风化对于深水沉积物的输入通量。为进一步探究埃迪卡拉纪-寒武纪转折期深海的元素异常及古海洋环境突变提供新的手段。

埃迪卡拉纪-寒武纪（E-C）全球发生了大规模风化作用，其与生物演化、金属异常富集及古海洋演化之间存在时间和空间上的耦合关系。本项目以贵州过渡斜坡和深水盆地E-C连续硅质岩和黑色页岩为对象，结合已有该区域年代地层学、岩石地层学、生物地层学已有成果，斜坡相-盆地相留茶坡组顶部富重晶石黑色页岩和其下覆陡山沱组顶部黑色页岩的Re-Os等时线年龄（分别为520.2 ± 6.1 Ma和561.7 ± 8.5 Ma）将留茶坡组的沉积年龄限定在550 Ma与520Ma之间。同时，获得的初始187Os/188Os比值（分别为0.902 ± 0.048和0.740 ± 0.042）显示，留茶坡组顶部和陡山沱组顶部沉积期间皆存在海底热液的参与，但留茶坡组顶部沉积时期大陆风化作用可能较陡山沱组顶部增强。贵州铜仁坝黄剖面留茶坡组层状硅质岩和湖南张家界柑子坪剖面留茶坡组穹隆状硅质岩的主量、微量元素和稀土元素以及Ge/Si特征显示，这两类硅质岩均为海底热液成因。其中层状硅质岩形成于盆地内部，受陆源输入的影响；而穹窿状硅质岩的形成与台地边缘同生断裂带的海底热液喷流相关。斜坡相镁同位素组成特征显示，δ26Mg值从陡山沱组、留茶坡组向寒武系牛蹄塘组底部呈逐渐增大趋势，且留茶坡组硅质岩顶部和牛蹄塘组黑色页岩底部的δ26Mg值较大，也指示自埃迪卡拉纪到寒武纪风化作用逐渐增强，在埃迪卡拉纪―寒武纪转折期较为强烈。整体来看，E-C转折期大陆风化作用强度的变化，会造成海洋地球化学性质的波动，从而控制黑色岩系的有机质丰度及其中微量元素的异常富集程度。本项目的研究结果能促进埃迪卡拉纪-寒武纪转折期大陆风化作用变化、古海洋环境演变及元素异常富集的理解。