摘要:基于砂岩碎屑组成、古流向恢复、全岩地球化学分析并结合已报道岩相古地理等研究成果的综合分析，探讨川西南晚三叠世瑞替期须家河组的物源体系、沉积记录及其形成的构造背景。砂岩碎屑组成分析结果显示，峨眉川主地区须家河组砂岩成分成熟度较低，组分与已报道的须家河组砂岩组分相似，物质以再旋回造山带来源为主；古流向测试数据统计显示须家河组主要接受来自东至东北部和东南部的物源，少量接受来自西南部和西北部的物源；地球化学主量元素及风化指数显示峨眉川主须家河组形成于构造活动背景下以被动大陆边缘和活动大陆边缘为主的沉积环境，物源成分成熟度较低；微量和稀土元素分析提示须家河组来源于长英质碎屑且含有较多古老沉积组分的加入，其球粒陨石标准化配分模式、原始地幔标准化微量元素模式与上地壳配分形式具有高度相似性，且物源主要与再旋回的扬子西南攀西—滇黔地区太古代—二叠纪变质岩、秦岭造山带前中生界变质岩和沉积岩、江南雪峰造山带西段的新元古代沉积有关，少量来自康滇古陆新元古代—元古代变质岩和龙门山周缘三叠纪沉积岩。结合须家河组已报道的岩相古地理数据，表明川西南峨眉地区晚三叠世瑞替期须家河组物源主要来自东南部的江南雪峰构造带和北部的秦岭造山带，少量来源于西南部的康滇古陆和西北部的龙门山构造带，川西南峨眉地区形成了主要受江南雪峰构造带、秦岭造山带为主控制的须家河组海陆交互相—陆相沉积盆地。
关键词: 晚三叠世须家河组/
物源分析/
地球化学/
构造意义
Abstract:In this paper, sandstone petrology, paleocurrents, whole geochemistry and published lithofacies palaeogeography data are integrated to investigate the provenance of Late Triassic Rhaetian strata from the E’mei region, SW China. Based on this, the main conclusions are listed as follows：The detrital components of sandstone from E’mei Chuanzhu section in southwestern Sichuan suggests that the Late Triassic Rhaetian sediments in E’mei region had a low mature components and multiple sources came from the recycling orogenic belts. Statistical data for paleocurrents exhibit that the sediments of Xujiahe Formation mainly came from eastern-southeastern and northeastern Sichuan, sparingly from the southwestern and northwestern Sichuan. Geochemical characteristics of sandstones from Xujiahe Formation show low maturity of major elements and reflect the Xujiahe Formation deposited under the tectonic settings of passive and active continental margin, and are similar ratios of relative trace and rare elements to the recycled sediments sourced mainly from Pre-Triassic meta-sediments of Panxi and Dianqian regions in Yangtze Craton, Jiangnan-Xuefeng thrust belt, Pre-Mesozoic metamorphic and sedimentary rocks of Qinling orogen, Neoproterozoic metamorphic rocks of Khamdian paleoland and Triassic sediments of Longmenshan thrust belt. Combined with the sandstone petrology, paleocurrents, geochemistry and published palaeogeography data, we propose that the Late Triassic Rhaetian sedimentary rocks of Xujiahe Formation in E’mei region shed mainly from Jiangnan-Xuefeng thrust belt and Qinling orogen, and sporadically from Khamdian paleoland and Longmenshan thrust belt. The Southwest Sichuan formed a marine and continental alternative depositional and terrestrial basin mainly controlled by Jiangnan-Xuefeng thrust belt and Qinling orogen during the Xujiahe Period in the Later Triassic.
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