鄂尔多斯盆地南部延长组时代划分及长7~3对印支Ⅰ幕的响应

发布时间：2018-05-01 19:22

本文选题：鄂尔多斯盆地 + 延长组　；参考：《地球科学》2017年09期

【摘要】：鄂尔多斯盆地延长组地层时代划分存在较大分歧,即延长组地层时代是否包含中三叠世以及中、上三叠统界线的确定,而长73地层的归属是其关键.针对争议采集了盆地南部何2井长73底部凝灰岩(H2-2)和长73中上部凝灰岩(H2-1)样品,对H2-2进行了锆石LA-ICP-MS U-Pb年代学和岩相学研究,对H2-1进行了岩相学和地球化学特征分析.结果表明:岩浆锆石的206Pb/238 U加权年龄为239.8±2.0Ma,属于中三叠世拉丁期,构造活动对应印支I幕;凝灰岩来源于大陆花岗岩环境,与西秦岭地区的构造环境一致.结合前人研究成果,认为延长组地层跨中、晚三叠世,长73地层属于延长组第2段并划归到中三叠统,其顶部(即"张家滩页岩"顶部)为中、上三叠统的分界.印支I幕构造岩浆活动在盆地发育了延长组长7油层组及凝灰岩等事件沉积,西秦岭地区的花岗质岩浆活动与长73凝灰岩在年龄、分布厚度、岩石组成和构造环境上均具耦合性,长73凝灰岩有可能来自西秦岭的岩浆活动.
[Abstract]:There are great differences in stratigraphic epoch division of Yanchang formation in Ordos Basin, that is, whether the stratigraphic age of Yanchang formation includes the middle Triassic and the determination of the boundary of middle and upper Triassic, and the attribution of Chang73 formation is the key. In view of the controversy, samples of tuff H2-2 at the bottom of Chang73 and H2-1 in middle and upper part of Chang73 are collected, zircon LA-ICP-MS U-Pb chronology and lithofacies of H2-2 are studied, and lithofacies and geochemistry characteristics of H2-1 are analyzed. The results show that the 206Pb/238 U weighted age of magmatic zircon is 239.8 卤2.0 Ma, which belongs to the Middle Triassic Latin epoch, the tectonic activity corresponds to the Indosinian I episode, and the tuff originates from the continental granite environment, which is consistent with the tectonic environment in the West Qinling area. Combined with the previous research results, it is considered that the Yanchang formation belongs to the second member of the Yanchang formation in the middle, late Triassic and the Chang73 formation belongs to the middle Triassic, and the top of the formation belongs to the middle and upper Triassic, the top of which is the top of the Zhangjiatan Shale. Indosinian tectonic magmatism developed Yanchang 7 formation and tuff deposits in the basin. The granitic magmatism and Chang73 tuff in the West Qinling region are of age and distribution thickness. The rock composition and tectonic environment are both coupled, and Chang73 tuff may originate from magmatic activities in the West Qinling Mountains.
【作者单位】：中国矿业大学地球科学与测绘工程学院;中国地质调查局西安地质调查中心;
【基金】：国家自然科学基金(No.41202104) 中国地质调查局矿产资源调查评价项目(Nos.121201011000150014,12120113040300)
【分类号】：P535

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