新元古代扬子克拉通TSM盆地原型分析

以TSM盆地原型分析理论为指导,基于大量野外露头、最新钻井和地球物理资料,结合前人研究成果,对扬子克拉通新元古代的盆地原型进行了恢复。研究认为受控于从青白口纪会聚到南华-震旦纪离散两大不同板块构造环境和体制转变下的4个时期演化影响,扬子克拉通新元古代经历了4个阶段的盆地原型演变,分别为①青白口纪早期(ca.1000~820 Ma),扬子西缘、北缘及内部的弧后扩张盆地,扬子东南缘的弧后前陆盆地;②青白口纪晚期(ca.820~720 Ma),扬子西缘、北缘的弧后扩张盆地,扬子东南缘和内部的拉张断陷盆地;③南华纪时期(720~635 Ma),扬子东南缘、西缘、北缘和内部的裂谷盆地;④震旦纪时期(635~541 Ma),川中、万源-达州及鄂西-渝东的克拉通台内裂陷盆地,扬子北缘和东南缘的离散陆缘坳陷盆地。综合分析提出南华纪裂谷盆地、震旦纪台内裂陷盆地和离散陆缘坳陷盆地是最有利于烃源岩发育的盆地原型。陕南-川东北、湘黔渝临区、鄂西和川中地区是扬子烃源岩最有利发育区,也是今后扬子深层-超深层常规天然气与非常规页岩气勘查重点区域。

TSM prototype basins on the Neoproterozoic Yangtze Craton

TSM basin analysis of Neoproterozoic prototype basins on Yangtze Craton, South China were studied using a large number of field outcrop sections, latest drilling data, and numerous previous studies. Controlled by the Qingbaikou convergent continental margin to the Nanhua-Sinian divergent continental margin, four phases of basin evolution are identified in the Neoproterozoic Yangtze Craton: a) the early Qingbaikou period(ca. 1 000-820 Ma), with back-arc spreading basins on the western and northern Yangtze margins and the interior, and a retro-arc foreland basin on the southeastern Yangtze margin; b) the late Qingbaikou period (ca.820-720 Ma), with back-arc spreading basins on the western and northern Yangtze margins and extensional down-faulted basins on the southeastern Yangtze margin and the interior of the carton; c) the Nanhua period (ca.720-635 Ma), with rift basins on the southeastern, western, and northern Yangtze margins and the interior; and d) the Sinian period (ca. 635-541 Ma), with intracratonic rift basins in the interior of Yangtze Craton (i.e. the central Sichuan, the Wanyuan-Dazhou and the west Hubei-east Chongqing area) and divergent marginal subsidence basins on the southeastern and northern Yangtze margins. The Nanhua rift basins and the Sinian divergent marginal subsidence and intracratonic rift basins were most conducive to source rock formation. The southern Shaanxi, northeastern Sichuan, western Hubei, central Sichuan and the adjacent area of Hunan, Guizhou and Chongqing are the most favorable areas of the Neoproterozoic source rocks in the Yangtze Craton. They are also considered to be favorable regions for deep natural gas exploration on the Yangtze Craton.