川东南-湘西地区志留系小河坝组砂岩微量元素地球化学特征及意义

砂岩岩石地球化学对沉积盆地形成时期构造背景的稳定与否有着较高的敏感度,已成为地质构造复杂地区研究的有效手段。采用电感耦合等离子体质谱(ICP-MS)测定了川东南-湘西地区志留系小河坝组37件砂岩样品的微量元素质量分数,应用w(V)/w(Ni)、w(V)/w(V+Ni)、w(Sr)/w(Ba)及w(V)/w(Sc)等特征微量元素比值及w(Zr)-w(Th)、w(La)-w(Sc)-w(Th)和w(Th)-w(Sc)-w(Zr)/10等多种沉积构造背景判别图解和多种参数交叉分析对研究区志留纪小河坝期砂岩的沉积环境及其源区构造背景进行了研究,结果表明:该区志留纪小河坝期总体上为缺氧的滞流浅海沉积环境,而靠近雪峰山隆起龙山县地区为贫氧环境。其源区沉积构造背景具有活动大陆边缘、大陆岛弧和被动大陆边缘的性质。

Signification and Characteristic of the Trace Element Ratios of the Sandstone in Silurian Xiaoheba Formation in Southeastern Sichuan Province and Western Hunan Province

Geochemistry of sandstones is hypersensitive to the stability of the structural evolution of the sedimentary basin, and so it has been an effective way to study the area with complicated background of geological structures. By ICP-MS, this paper detected the trace element contents of 37 sandstone samples collected from Silurian Xiaoheba Formation in southeastern Sichuan Province and western Hunan Province. It also studied the sedimentary environment and the tectonic setting of the source area of the sandstones in the formation by means of trace elements ratios such as V/Ni ,V/(V+Ni) , Sr/Ba and V/Sc as well as graphic interpretation of sedimentary structure background such as Zr-Th,La-Sc-Th and Th-Sc-Zr/10, and the cross-analysis of multiple parameters. The results showed that this area of Silurian Xiaoheba Formation generally was a detent shallow sea of hypoxia and the Longshan County area near the Xuefengshan uplift was in an oxygen-poor environment. While its source area structure background includes active continental margin , continental arcuate islands and passive continental margin.