上扬子会泽地区晚三叠世须家河组主要由辫状河-浅湖的砂岩和泥岩组成,交错层理校正恢复的物源主要来自东南方向.碎屑重矿物钛铁矿、锐钛矿、铬尖晶石和磁铁矿组合表明物源主要来自岩浆岩,部分为基性岩,且重矿物中发现大量碎屑电气石和锆石.运用电子探针成分分析和碎屑锆石LA-ICP-MS U-Pb测年方法,分别对须家河组砂岩中电气石和碎屑锆石进行测试分析.电气石化学成分显示主要为镁电气石和黑电气石,来自变质板岩和变质砂岩以及贫锂花岗岩类、伟晶岩和细晶岩.砂岩碎屑锆石U-Pb年龄谱分析表明,须家河组的物源主要来自257 ～ 362 Ma、420～492 Ma、782～876 Ma和1 690～2 176 Ma岩石.物源方向、重矿物以及电气石和碎屑锆石综合分析表明,须家河组物源主要来自滇黔桂古陆.其中,257～362 Ma的物源岩石主要为峨眉山玄武岩同期侵入岩;420～492 Ma来自东南源岩为花岗岩和砂岩,782 ～876 Ma主要为研究区周缘同期的花岗岩和砂岩,1 690 ～2 176 Ma物源也是源岩为岩浆岩的砂岩.与飞仙关组物源对比,须家河组物源区明显不同,可能与区域构造运动有关.同时,碎屑锆石指示古元古代发育岩浆作用,且存在古老的新太古代结晶基底.这些资料为上扬子构造演化提供了沉积学证据.%The Late Triassic Xujiahe Formation in Huize area,Upper Yangtze consists of braided river and shallow lacustrine sandstones and mudstones.The direction of provenance restored by cross bedding mainly comes from the southeast.The heavy mineral assemblages of ilmenite,anatase,chromian spinel and magnetite indicate that they can be provided by magmatic rocks and part of mafic rocks.In this paper,the tourmaline and detrital zircon in Xujiahe sandstone are respectively tested and analyzed by electron microprobe analysis and detrital zircon LA-ICP-MS U-Pb dating.The chemical compositions of tourmaline are mainly dravite and schorl.They are mainly from metapelites and metapsammites,and a small amount of Li-poor granitoids and associated pegmatites and aplites.The detrital zircon U-Pb age spectrum shows that the source rocks of Xujiahe Formation mainly come from 257 to 362 Ma,420 to 492 Ma,782 to 876 Ma and 1,690 to 2,176 Ma rocks.The paleocurrent direction,heavy mineral assemblages,tourmaline electronic microprobe analysis and detrital zircon dating show that the source was mainly from the Dianqiangui Oldland.The 257 to 362 Ma source rocks are mainly Emeishan basalt and intrusive rocks;420 to 492 Ma and 782 to 876 Ma ones are from granite and sandstones,and 1 690 to 2 176 Ma ones are from sandstones.Compared with the provenance of Feixianguan Formation,the source area of Xujiahe Formation is obviously different,which may be related to tectonic movement.Detrital zircon dating indicates that there existed Paleoproterozoic magmatism and Neoarchean crystalline basement.These data provide sedimentological evidence for tectonic evolution of the Upper Yangtze.
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