Changes of Detrital Composition of Sandstones from the Nanhua System, Quruqtagh Area: Implications on their provenance and the evolution of basin

Key words: 
• Quruqtagh /
• Nanhua System /
• modal data on sandstones /
• transformation event /
• provenance /
• rift basin /
• evolution of the basin

Abstract: The Nanhua System in Quruqtagh area could record a synchronous volcanic-sedimentary events along the northern margin of the Tarim craton. The characteristics of the detrital components of Nanhua System sandstones from various sections indicate that sandstones from Bayisi Formation in different section have different detrital components. In Xishankou section, litharenites are the key components, in which the rock fragments are volcanic rocks and sedimentary rocks, obviously, indicating a recycled sedimentary provenance. Whereas, in Yigezitage section, the key components are arkoses and lithic arkoses, and the rock fragments are metamorphic rocks while there are lots of mineral inclusions in quartz, which all indicate a metamorphic provenance. Vertical variation of sandstone's detrital components recorded a transform event between the boundary of Bayisi Formation and Zhaobishan Formation(725 Ma±), which causes Zhaobihsan, Altungol and Tereeken Formation have a uniform sandstone component. Converted to a typical arkose composition those represent a basement uplift-transitional continental provenance. The detrital component of Nanhua System sandstones and temporal-spatial variation demonstrates a continental rift setting of Nanhua System at Quruqtagh area. Meanwhile, it also shows a successive provenance evolution from pre-rift sedimentary successions to transitional rift-shoulder to dissected rift-shoulder to transitional continental and craton interior. Consequently, the petrography of sandstones in Quruqtagh area records the early breakup of Quruqtagh-Mangar aulacogen.