鄂尔多斯盆地镇原地区下白垩统砂岩型铀矿物源分析:来自锆石U-Pb年代学的约束OA

The Lower Cretaceous sandstone type uranium deposits are an important source of uranium resources in Ordos Basin with remarkable exploration achievements in recent years.Studying the coupling mechanism between provenance and uranium source helps to deepen the understanding of the metallogeny of Ordos Basin.In this paper,LA-ICP-MS zircon U-Pb dating(n=926)was performed on eight sandstone core samples from Lower Cretaceous in Zhenyuan area,southwestern margin of Ordos Basin.Using an area-normalized method for provenance analysis,the obtained U-Pb ages were compared as a whole with potential source areas,and the possible provenances were discussed for each stratigraphic horizon,aiming to analyze the sedimentary provenance evolution during the mineralization period of Lower Cretaceous sandstone-type uranium deposits in the southwestern margin of the Ordos Basin.Four major age peaks were identified:Precambrian(1.87-1.80 Ga,2.54-2.44 Ga)and Phanerozoic(359-278 Ma,467-431 Ma).The zircons generally exhibit features of magmatic origin and anatectic modification.Detailed provenance comparison indicates that Luohe Formation may have been derived from Qinling and Qilian orogenic belts;Huanhe Formation likely represents a mixed provenance of pre-enriched uranium and source areas from Qinling and Qilian orogenic belts;Luohandong Formation,characterized by typical aeolian deposits,may have originated from Alxa and Yinshan areas;Jingchuan Formation may share a similar provenance composition with Luohandong Formation.Ages older than 3.0 Ga may be related to Meso-to Paleoarchean crustal remnants in Alxa area.Lower Cretaceous as a whole exhibits a multi-source mixed signature,including both pre-enriched uranium in the ore-bearing target layers within the basin and abundant,stable provenance input from source areas.Its sedimentary input was mainly derived from four major provenance systems:Qilian Mountains,Qinling Mountains,Yinshan Mountains,and Alxa.