上扬子西南盐源盆地早三叠世物源体系及构造意义

发布时间：2019-05-18 19:08

【摘要】：晚古生代末期至早中生代期间,上扬子西部边缘地区经历了峨眉山大火成岩省构造岩浆热事件和与古特提斯洋闭合相关的三江造山带形成事件,导致康滇古陆两侧形成了独特的盆山格局和沉积模式.由于目前人们对盐源盆地早三叠世青天堡组的物源与构造背景了解不多,故以盐源、盐塘剖面为代表,对青天堡组碎屑岩进行了砂岩组分、全岩地球化学和碎屑锆石年代学分析.结果显示,盐源盆地下三叠统青天堡组物源来自于近源搬运的火山岩,青天堡组与峨眉山大火成岩省的高钛玄武岩具有一致的元素组合配分模式,青天堡组锆石谐和加权平均年龄为261±16Ma,与峨眉山大火成岩省形成的地幔柱活动时期一致.上述结果表明早三叠世盐源盆地青天堡组物源为其东侧的峨眉山大火成岩省,扬子西部三江造山带可能并没有为盐源盆地提供物源,上扬子西南边缘地区早三叠世时期仍然为被动大陆边缘沉积.
[Abstract]:From the end of the late Paleozoic to the early Mesozoic, the western margin of the Upper Yangtze experienced tectonic magmatic thermal events in Emeishan fire diagenetic province and the formation of the Sanjiang orogenic belt related to the closure of the ancient Tethys Ocean. As a result, a unique basin-mountain pattern and sedimentary model were formed on both sides of the Kangdian ancient continent. At present, little is known about the provenance and tectonic background of the early Triassic Qingtianbao formation in the Yanyuan Basin, so the sandstone components of the clastic rocks of the Qingtianbao formation are carried out, represented by the salt source and Yantang section. Whole rock geochemistry and clastic zircon chronological analysis. The results show that the provenance of the Qingtianpu formation of the Lower Triassic in the Yanyuan Basin comes from the volcanic rocks transported by the near source, and the Qingtianbao formation has the same element assemblage distribution model as that of the high titanium basalt in Emeishan igneous province. The harmonic and weighted average age of zircon in Qingtianbao formation is 261 卤16 Ma, which is consistent with the active period of mantle plume formed in Emei Mountain igneous province. The above results show that the provenance of Qingtianbao formation in early Triassic Yanyuan Basin is Emeishan igneous diagenetic province on the east side of Qingtianbao formation, and the Sanjiang orogenic belt in western Yangtze may not provide provenance for Yanyuan basin. The early Triassic in the southwest margin of the Upper Yangtze was still a passive continental margin deposit.
【作者单位】：浙江大学地球科学学院;教育部含油气盆地构造研究中心;
【基金】：国家科技重大专项项目(Nos.2016ZX05008-001,2016ZX05003-001)
【分类号】：P534.51

【相似文献】