鄂尔多斯盆地西南部三叠系延长组物源分析

Provenance analysis of the triassic extended group in the southwest of Ordos basin

为探讨鄂尔多斯盆地西南部三叠系延长组沉积物来源和沉积环境的变化,采集了陇县及周缘地区若干样品进行元素地球化学测试与分析。通过古流向、砂岩碎屑组分、轻重矿物组合、碎屑颗粒粒度等方面分析得出以下认识:鄂尔多斯盆地西南部延长组沉积物主要有北、东北、东南、南、西南和西北6个输入方向,其中东北、东南、西南为其主要物源输入方向。因受到秦祁造山带拼合的影响,延长组不同层段物源供给区存在差异。晚三叠世早期,研究区沉积物源主要来自盆地北部岩浆岩体和东北部杂岩;晚三叠世中期,沉积物源主要来自东北、东南两个方向,其次为西南向;晚三叠世晚期,沉积物源主要来自南、西南方向秦祁造山带。

In order to explore the source of sediments and changes in the sedimentary environment of the Triassic extended group in the southwest of the Ordos basin,several samples from Long County and surrounding areas were collected for elemental geochemical testing and analysis.Through the analysis of paleo-flow direction,sandstone clastic components,light and heavy mineral assemblages,and clastic particle size,the following conclusions are obtained:The sediments of the extended group in the southwest of the Ordos basin are mainly imported from the north,northeast,southeast,south,southwest and northwest.Direction,with northeast,southeast,and southwest as the main source input directions.Affected by the assembling of Qinqi orogenic belts,the source supply areas of different layers of the extended group are different.In the early Late Triassic,the sediment sources in the study area mainly came from the northern magmatic rock mass and the northeastern complex;in the middle of the Late Triassic,the sediment sources mainly came from the northeast and southeast directions,followed by the southwest direction;the Late Triassic In the late epoch,sediment sources mainly came from the Qinqi orogenic belt in the south and southwest.