作　　者： ; ; ;

机构地区： 四川大学

出　　处： 《沉积学报》 2003年第2期191-197,共7页

摘　　要： 青藏高原是由若干条缝合带和其间所夹的沉积盆地构成 ,其中晚三叠世北羌塘盆地位于金沙江缝合带南缘 ,盆地的充填实体显示为南薄北厚 ,为楔形沉积体 ;在垂向上 ,以不整合面为界可将该套充填地层划分为两个构造层序 ,下部构造层序以复理石建造为特征 ,上部构造层序以磨拉石建造为特征 ,具有典型的前陆盆地充填序列 ;盆地具双物源和双古流向体制 ,沉降中心和沉积中心具有不一致 ,显示其为金沙江缝合带南侧的周缘前陆盆地 ,从而确定了晚三叠世北羌塘前陆盆地与金沙江缝合带的成因关系。在此基础上 ,结合在金沙江缝合带西段新发现和确定的蛇绿岩的最小年龄和碰撞型花岗岩的年龄 ,本文根据下部构造层序复理石的年龄、前缘隆起的形成年龄、冲断带隆升成为地貌高地的年龄、下部不整合面的时代和前缘隆起型碳酸岩缓坡的形成时间标定了金沙江缝合带碰撞事件的时代下限 ,根据上部构造层序磨拉石的年龄、上部不整合面的年龄、花岗岩和构造碎裂岩成为物源的年龄标定了金沙江缝合带碰撞事件的时代上限 ,表明金沙江缝合带初始碰撞事件为卡尼克期与诺利克期之间 。 Qinghai-Tibetan Plateau is composed of many sutures and basins. The late Triassic northern Qiangtang foreland basin system is peripheral foreland system in the front of Jinshajiang suture and can be divided into four tectonic units from north to south, including the Jinshajiang suture, Hoh Xil thrust belt, Qiangtang foreland basin and the forebulge (center uplift). The Late Triassic northern Qiangtang foreland basin is filled with more than 2500 m strata and can be divided into two tectonic sequences bounded by unconformities. In a transverse section there is wedge-shaped sedimentary body and the depocenter was located in north part of the basin . There were double paleocurrent and double provenances in the basin. Based on the youngest age of ophiolite, collision granite, Flysch, Molasss, carbonate ramp on forebulge and clast in sandstone and conglomerate, unconformity between Flysch facies and Molasse facies, it has been suggested that the time of the major collision between Qiangtang block and Euasian block is between Norian and Rhaetian.

关 键 词： 西藏 金沙江缝合带 晚三叠世 沉积盆地 羌塘盆地 碰撞作用 花岗岩 构造层序 磨拉石

领　　域： [天文地球] [天文地球] [天文地球] [天文地球]