四川盆地晚三叠世碎屑组分对源区分析及印支运动的指示  

Upper Triassic Clastic Composition in Sichuan Basin,Southwest China:Implication for Provenance Analysis and the Indosinian Orogeny

作　　者：施振生[1] 杨威[1] 谢增业[1] 金惠[1] 谢武仁[1] 

机构地区：[1]中国石油勘探开发研究院廊坊分院,河北廊坊065007

出　　处：《地质学报》2010年第3期387-397,共11页Acta Geologica Sinica

基　　金：国家重点基础研究发展规划(973)项目课题(编号2007CB209503)资助的成果

摘　　要：沉积物源分析是认识盆山演化的重要途径。四川盆地上三叠统的砾岩碎屑、砂岩骨架颗粒、碎屑重矿物组分显示,晚三叠世存在5大物源,它们分布于龙门山北段-中段、大巴山、龙门山南段、盆地东南和盆地南部。碎屑物源总体以"再旋回造山带"和"大陆板块"类型为主,其中,龙门山北段-中段和龙门山南段以"再旋回造山带"类型为主,而盆地东南部和南部以"大陆板块"类型为主。"再旋回造山带"类型可细分为"混合造山带"及"碰撞造山和褶皱冲断带"两种类型,龙门山北段和龙门山南段均以"混合造山带"及"碰撞造山和褶皱冲断带"类型为特征。盆地物源分布存在阶段性特征:早期,龙门山北段-中段、大巴山物源规模较大,盆地东南和南部规模较小;晚期,盆地东南和南部规模增大,各方向呈均衡分布格局,这与周缘板块构造活动的阶段性有关。晚三叠世,龙门山北段由西北向东南方向挤压,构造活动强度总体具有弱-强-弱的演变趋势。须二期,龙门山北段逆冲-推覆开始形成,并暴露水面遭受剥蚀,向盆地提供物源;须四期为盆地最活跃期,龙门山北段进一步挤压抬升剥蚀,盆内沉积中心也由西北向东南迁移;须四期后,龙门山北段剥蚀区继续向东南推进,但构造活动强度渐趋和缓。Analysis of depositional provenances is an important approach to understand the history of basin-range evolution. Mineral compositions of Upper Triassic conglomerate clasts and sandstone framework grains and heavy minerals in Sichuan Basin suggest five depositional provenances, which are distributed around the north-central Longmenshan, south Dabashan, south Longmenshan, southeastern and southern Basin. The clastic depositional provenances are dominated by the recycled orogen zone and continental plate type, with the former in the middle, north, and south Longmenshan, and the latter in the south-east and the south Sichuan Basin. The recycled orogen can be subdivided into two types： mixed orogenic belt, and collision orogen and fold thrusting fault belt, with both occurring in north and south Longmenshan. The distribution of depositional provenances displays different stages. In the early stage, depositional provenances were distributed dominantly in the middle-south part of Longmenshan and Dabashan, with limited deposits from the south-east and south Sichuan Basin. In the late stage, the south-east and south Sichuan Basin provided much sediment increasingly, leading to balanced distribution of depositional provenances, and this may be related to periodic tectonic activities of circumferential plate. During Late Triassic, the north Longmenshan experienced an NW—SE compression and intensity of tectonic activities also experienced a change trend from weak and then strong to weak.During the member 2 sedimentary period of Upper Triassic, Longmenshan area began thrusting and overlapping, and then denuded after exposing groundwater, which provided substantive sediments to Sichuan Basin. The member 4 sedimentary period of Upper Triassic was characterized by intensive tectonic activity, which resulted in further compression-lifting-denudation of north Longmenshan. The depocenter of the basin migrated from northwest to southeast basin. Afterwards,the denudation of north Longmenshan advanced from NW to SE basin continua

关 键 词：四川盆地 上三叠统 碎屑组分 源区 印支运动 

分 类 号：P618.13[天文地球—矿床学]