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中文摘要：
本文通过对鄂尔多斯盆地南部的物源区大地构造性质、沉积格局及古水流等的综合分析,并结合砂岩组分,轻、重矿物及微量元素等资料,对盆地南部晚三叠世物源进行了深入分析,旨在阐明古物源与沉积体系的空间配置,确定物源的差异演化过程及发展趋势。研究表明,盆地南部晚三叠世沉积物源主要为太古生界深变质的结晶片岩、片麻岩及震旦亚界和古生界的浅海相碎屑岩及碳酸盐岩。在物源分异的影响下,不同的沉积体系分布区轻、重矿物组分特征明显不同。在镇原—泾川地区砂岩碎屑中石英含量相对较高,岩屑主要为沉积岩屑,向东南部铜川—耀县一带,长石含量逐渐增加,岩屑中火成岩和变质岩岩屑也增加。盆地南部重矿物主要为锆石、电气石及石榴石为主的组合,其分布受到了沉积水系的控制,形成了西南部的环县—庆阳—泾川一带、南部的长武—宁县一带、东南部的黄陵—铜川地区和东北部富县—延安一带的4个重矿物集中分布区,分别对应于不同的古水系及沉积物扩散区。在REE配分模式上,富县—延安地区延长组地球化学特征及配分模式曲线与盆地东北缘太古代及早元古代变质岩一致,二者有较大的亲缘关系;镇泾地区和盆地西南缘变质岩REE分配模式基本一致。
英文摘要：
The source rocks of the Late Triassic in the southern Ordos basin are mainly the Archaean highly metamorphosed schists and gneisses,and the Sinian to Paleozoic shallow marine clastic rocks and carbonates.Affected by different sources,the light and heavy mineral assemblages have different features in various areas of a sedimentation system.In the western Zhenyuan- Jingchuan area,quartz content of sandstone is relatively high,and the lithic debris is mainly the sedimentary rocks.To the southeast,in the Tongchuan-Yaoxian area,feldspar and debris of igneous and metamorphic rocks are gradually increased.In the southern region of the basin,the heavy mineral assemblage is of zircon＋tourmaline＋garnet type,controlled by sedimentation channel net.There are mainly four distribution areas in heavy mineral association：the Huanxian-Zhenyuan-Jingchuan area in the west is characterized by garnet＋zircon＋tourmaline＋leucoxene assemblage;the Changwu-Ningxian area in the south is characterized by zircon＋tourmaline＋leucoxene＋garnet assemblage;the Huangling-Tongchuan area in the southeast is characterized by garnet＋zircon＋leucoxene assemblage;and the Fuxian-Yan, an area in the northeast is characterized by garnet ＋zircon＋magnetite assemblage.They respectively correspond to their own ancestral rivers and sedimentary diffusion areas.In the Fuxian-Yan, an area,the REE patterns and geochemical characteristics of theYanchang Formation are nearly similar with the Archean and Early Proterozoic metamorphic rocks to the northeast of the basin.In the Zhenyuan-Jingchuan area,the REE patterns of the Yanchang Formation sandstones are nearly similar to the metamorphic rocks to the southwest of the basin.This is certainly genetically related.Consequently,it can be inferred that the structural evolution process of the southwestern and northeastern areas of the basin was different.
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