南秦岭微陆块是秦岭造山带的重要构造单元,为了探讨南秦岭中生代断陷盆地的物质来源,本文选取凤太地区下白垩统东河群田家坝组复成分砾岩、周家湾组凝灰质砂岩为研究对象,对其中的碎屑锆石进行了LA-ICP-MS锆石U-Pb同位素测年,获得2组各40个有效年龄.结果明显可以分为5个年龄峰,范围分别是:2595～2771Ma、1 215～1 916 Ma、749～1 142 Ma、424～576 Ma、218～306 Ma,分别对应Kenor、Columbia、Rodinia、Gondwana、Pangaea等5次超大陆事件.通过对测年数据进行分析,结合区域地质资料,认为北秦岭增生造山带和华北板块为南秦岭中生代盆地提供了大部分的物源,扬子板块次之,北祁连造山带和西秦岭北缘构造带也有一定的贡献.%The South Qinling microcontinent is one of the important tectonic units of the Qinling orogenic belt.In order to study the provenance of sediments in Mesozoic graben basin in South Qinling,the authors conducted LAICP-MS zircon U-Pb isotopic dating on polymictic conglomerate of Tianjiaba Formation and tuff sandstone of Zhoujiawan Formation of Lower Cretaceous in Fengtai area.Two groups of dating data were obtained,which have 40 effective ages respectively.The results show that the zircon ages have five age peaks with ranges of 2 595 ～ 2 771 Ma,1 215 ～ 1 916 Ma,749 ～ 1 142 Ma,424 ～ 576 Ma and 218 ～ 306 Ma,which correspond respectively to Kenor,Columbia,Rodinia,Gondwana and Pangaea supercontinent events.Based on zircon dating analyses and combined with the regional geological data,it is concluded that the North Qinling accretion-type orogen and the North China plate provided the dominant clastic materials for the Mesozoic basin in South Qinling,followed by the Yangtze plate.The North Qilian orogenic belt and the northern margin of West Qinling orogenic belt also contributed to the provenance of sediments in the Mesozoic basin of South Qinling.
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