巴颜喀拉三叠纪沉积盆地岩相与古地理——以阿坝-若尔盖盆地为例

Sedimentary facies and palaeogeography of the Triassic sedimentary basins in the Bayan Har mountainous area:an example from the Aba-Zoige Basin,Sichuan

关键词:  海底扇浊积岩  三叠纪  巴颜喀拉

Key words:  submarine-fan turbidite  Triassic  Bayan Har

摘要:

以阿坝-若尔盖盆地岩相与古地理研究为例,并结合区域上有关资料。认为巴颜喀拉三叠纪沉积盆地发育有世界上罕见的巨型浊流沉积,主要由一套大陆斜坡浊积扇相组合与深海盆地相组合等构成。而斜坡浊积扇、深海盆地的形成与发展和海平面的下降期与上升期存在着对应关系,发育一系列叠复的浊积扇舌状体;浊流沉积物以陆源碎屑为主,伴有火山物质和碳酸盐岩的混合源型。物源主要来自北西侧与北侧的浅变质岩区;盆地属多阶段、多物源、不同构造性质相叠加的复合盆地。巴颜喀拉地区作为独立的微板块与东部扬子板块之间会聚、碰撞表现为扬子板块为俯冲,巴颜喀拉微板块为仰冲性质。新都桥组缺氧事件沉积物中具较广泛的微细浸染型金矿化,赋存于低密度浊流沉积的扇尾—深海盆地相内,而且也是现代砂金矿床的主要源区地层。

Abstract:

The Triassic sedimentary basins in the Bayan Har mountainous area with a total area of about 370,000 km² sandwiched between the Qinling-Qilian-Kunlun and Karakorurn microplates are bounded by the deep faults on the southern margin of the Kunlun uplift on the north,he Longmenshan-Jinpingshan deep faults on the southeast,Garze-Litang deep faults on the southwest, including Hoh Xil, Aba-Zoige, Xiaojin-Barkam, Yajiang and Jiulong basins. In the present paper,the emphasis will be on the Aba-Zoige Basin. Since the outcrops are scarce,much of the basin is now covered by the Quaternary marshes, and composed of the Lower Triassic Bocigou Formation,Middle Triassic Zagunao Formation and Upper Triassic Zhuwo and Xinduqiao Formations.