塔里木盆地西北缘下志留统沉积构造背景初探

A PRELIMINARY STUDY ON TECTONIC SETTING OF THE LOWER SILURIAN IN NW TARIM

塔里木盆地西北缘柯坪塔格组中段的浊积岩 (灰_ 灰绿色砂_ 泥岩 )时代属早志留世。 1 2个样品的岩石化学分析结果表明其形成的大地构造背景为被动大陆边缘 ,物源区性质函数判别图则指示了一个成熟大陆石英质物源区。

The samples were collected from middle part of the Kepingtag Formation in age of Early Silurian, outcropping to the west of Akesu, northwest margin of the Tarim Basin. The geochemical features of the samples of sandstone and siltstone indicated the tectonic setting being a passive continental margin, and the provenance being a quartziferous one of matured continent. Synthesized with other evidences, it was put forward that the Nantianshan Oceanic Basin opened in Late Precambrian, and the Lower Paleozoic sediments in northwest marginal area of the Tarim were deposited on its southern continental slope; the oceanic crust subducted northwards in Silurian, and the northwest margin of the Tarim Basin kept on a passive continental margin.