东特提斯洋二叠纪硅质沉积事件研究

Based on latest researches on the opening to closing transitional period of eastern Paleo-Tethys, a series of geological and geochemistry methods such as field profile observation, rock thin section identifications, fluid inclusion analyses, elemental and isotopic analyses will be carried to investigate the typical Permian siliceous rocks outcrops in North China region, Lower Yangtze region and Upper Yangtze region. This project will present a thorough study of the distribution and evolution of silicates, geochemical characteristics and hydrothermal sedimentation characteristics of silicates on both sides of eastern Paleo-Tethys, also make clear the differences and similarities of sedimentary environment, diagenesis, genetic models, silica source of silicates in the eastern Tethys area, which takes aim at complementing the studies of global Permian Chert Event (PCE). The project will ascertain the developmental mechanism, kinematic and dynamic characteristics features of silica hydrothermal sedimentation system in Permian ocean basin, and figure out the characteristics of silica source region and the activity of Mid-ocean ridge in eastern Paleo-Tethys Ocean, which could provide key informations for reconstructing the paleo-environment of the eastern Paleo-Tethys Ocean during the important transitional period. By establishing the geochemistry modeling of hydrothermal silicates in different stages from silica resource region, silica migration region to silica deposition region,the project is designed to set up intrinsic relationships between Permian Chert Event and MOR evolution .

本项目以华北、上扬子、下扬子地区二叠系典型硅质岩沉积剖面为研究主线，以东特提斯洋东段由扩张到闭合转型阶段为研究背景，通过野外剖面观测、薄片鉴定、流体包裹体分析、元素及同位素分析等一系列地质、地球化学方法，深入研究东特提洋南北两岸二叠系硅质岩时空展布、地球化学特征及热水沉积作用特征，确立东特提斯地区硅质岩在沉积环境、成岩作用、成因类型、硅质来源方面的统一性与差异性，补充全球二叠纪硅质沉积事件研究；明确大洋盆地二叠纪硅质热水发育机理、硅质运移的运动学和动力学特征，阐明硅质岩源区性质，探讨东特提斯洋东段洋盆演化及洋中脊活动性，对东特提斯洋转型期的古海洋演化提出约束条件；建立热水沉积硅质岩在硅质源区、运移区到沉积区等不同阶段的地球化学模型，厘定硅质沉积事件与洋中脊演化的响应、耦合关系。

本项目以华北、华南多个二叠系典型硅质岩剖面为研究主线，以东特提斯洋东段由扩张到闭合转型阶段为研究背景，展开了华北、华南地区二叠纪硅质岩的分布与成因研究，探讨了多个二叠纪典型硅质岩剖面的岩石学、矿物学、地球化学特征，明确了硅质岩的时空展布、沉积环境、成因类型及硅质来源。针对生物成因层状硅质岩-泥岩的旋回地层学展开研究，对下扬子巢湖地区中二叠统孤峰组放射虫硅质岩-泥岩韵律层进行天文调谐，发现千年尺度的米兰科维奇信号，揭示硅质岩中的古气候记录。针对硅质岩对地质事件的沉积响应机制应展开研究，综合东特提斯洋大陆边缘盆地二叠纪硅质岩成因分布特征，揭示了硅质沉积对同时期古地理、古构造、古海洋演化的沉积响应机制。本项目综合探讨古特提斯洋东部边缘海盆地内硅质岩成因及其所记录的地质信息，明确了古特提斯洋硅质富集与泛大洋硅质岩沉积响应机制的异同。