| 鄂尔多斯盆地中北部直罗组砂岩地球化学、碎屑锆石U-Pb年龄对物源和构造背景的限定 |
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| 引用本文：杨桐旭,俞礽安,荣辉,李彤,朱强,司庆红,涂家润,彭胜龙.2024.鄂尔多斯盆地中北部直罗组砂岩地球化学、碎屑锆石U-Pb年龄对物源和构造背景的限定[J].地球学报,45(6):941-952. |
| DOI：10.3975/cagsb.2024.011603 |
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| 基金项目:中国地质调查局地质调查项目(编号: DD20230045)；内蒙古中西部重点铀矿勘查区块优选调查评价项目(编号: D20221678-5) |
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| 中文摘要:中侏罗统直罗组地层作为鄂尔多斯盆地的重要含铀层位, 其盆地中部的物源分析研究较为薄弱。本文采用岩石学、元素地球化学、碎屑锆石U-Pb测年等方法, 对盆地中部丁格当庙地区直罗组下段砂岩进行物源示踪, 并与盆缘进行对比分析。岩石学和地球化学结果显示, 研究区砂岩物质来源为上地壳。测年结果显示, 丁格当庙研究区直罗组下段砂岩样品锆石年龄总体呈现出300~200 Ma、2 100~1 500 Ma、 2 600~2 200 Ma三个年龄段, 前寒武的锆石主要来自大青山、乌拉山和阴山一带, 古生代晚期—中生代早期的锆石主要来自大青山地区。根据盆地东北部铀矿床和中部地区直罗组碎屑锆石对比研究, 认为直罗组沉积期印支期地质体已经出露地表, 但并未大面积裸露。结合区域沉积学特征, 分析认为鄂尔多斯盆地东北部至盆地中部的砂岩型铀矿属同一源头, 古水流方向及物源方向为由北向南, 沉积体系由辫状河沉积体系逐渐过渡到辫状河三角洲沉积体系。 |
| 中文关键词:鄂尔多斯盆地 直罗组 地球化学 碎屑锆石U-Pb年龄 物源 LA-ICP-MS |
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| Geochemistry of Sandstones and U-Pb Ages of Detrital Zircons in the Zhiluo Formation of the Central and Northern Ordos Basin, China: Constraints on Provenance and Tectonic Setting |
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| Abstract:The Middle Jurassic Zhiluo Formation, as an important uranium-bearing layer in the Ordos Basin, has received only relatively weak source analysis research in the central part of the basin. In this study, petrology, element geochemistry, detrital zircon U-Pb dating, and other methods are used to trace the source of sandstone in the lower member of the Zhiluo Formation in the Dinggedangmiao area in the central part of the basin and compare these results with those of the basin margin. The petrologic and geochemical results show that the sandstone in the research area was derived from the upper crust. The U-Pb dating results show that the ages of the zircons in the sandstone samples from the lower Zhiluo Formation in the Dinggedangmiao study area generally fall into the three age ranges of 300~200 Ma, 2 100~1 500 Ma, and 2 600~2 200 Ma. The Precambrian zircons are mainly from the Daqingshan, Wulashan, and Yinshan areas. The Late Paleozoic to Early Mesozoic zircons are mainly from the Daqingshan area. Based on a comparative study of zircon fragments in the uranium deposits in the northeast of the basin and the Zhiluo Formation in the central region, it is believed that the source geological bodies of the Zhiluo Formation were already exposed to the surface, but not extensively exposed, during the Indosinian sedimentary period. In combination with the regional sedimentologic characteristics, the analysis indicated that the sandstone-type uranium deposits extending from the northeast to the middle of the Ordos Basin have the same source, a north-to-south paleocurrent and provenance direction, and a sedimentary system that gradually changed from a braided river sedimentary system to a braided river delta sedimentary system. |
| keywords:Ordos Basin Zhiluo Formation geochemistry detrital zircon U-Pb age source rocks LA-ICP-MS |
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