内蒙古狼山地区侏罗系LA-ICP-MS碎屑锆石U-Pb定年及其物源意义

发布时间：2019-01-18 08:06

【摘要】：运用碎屑锆石LA-ICP-MS U-Pb测年和地球化学方法,对内蒙古狼山东升庙和义和久地区侏罗系石拐群物源进行了探讨。通过对111颗有效锆石年龄统计分析可知,年龄峰值以晚古生代(259~308Ma)为主,其次为古元古代(1.74~2.18Ga)和早古元古代—新太古代(2.39~2.58Ga)。晚古生代年龄与狼山大规模出露的海西期岩浆岩年龄一致,古元古代—新太古代年龄与狼山地区古元古代岩浆岩、孔兹岩带年龄分布特征相近。侏罗系砂岩稀土元素配分特征与海西期岩浆岩、乌拉山群、孔兹岩系相似。结合石拐群样品薄片和砾岩分析,认为侏罗系为近源沉积,其物源主要为狼山地区大规模海西期岩浆岩,其次来自河套地区孔兹岩带,狼山地区太古宙乌拉山群、古元古代岩浆岩和早—中三叠世岩浆岩可能提供了部分物源。另外,根据碎屑锆石最年轻年龄为243Ma(中三叠世),结合前人植物化石组合研究及狼山地区整体缺失三叠纪地层的特点,认为该套地层的时代应为早—中侏罗世。狼山地区侏罗系沉积物源模式为南北两侧为隆起物源区,主要物源为北侧狼山隆起,南侧河套隆起向北提供部分物源,不同地区物源存在一定差异。
[Abstract]:Based on the LA-ICP-MS U-Pb dating and geochemistry of detrital zircons, the source of Jurassic Shijiaodong Group in Dongsheng Miao, Langshan, Inner Mongolia was discussed. According to the age analysis of the available zircon, the peak age is mainly in the late Paleozoic (259~308Ma), followed by Gu Yuan (1.74~2.18Ga) and early Gu Yuan-NeoArchean (2.39~2.58Ga). The age of late Paleozoic age is the same as that of Hercynian magmatite, and the age distribution of Paleoproterozoic and NeoArchaean age is similar to that of Gu Yuan magmatic rock in Langshan area. The REE distribution characteristics of Jurassic sandstone are similar to that of Hercynian magmatic rocks, Wulashan group and Kongzi series. Based on the analysis of sample sheet and conglomerate of ShijiaoGroup, it is concluded that the Jurassic is a near-source sedimentary system, and its provenance mainly comes from the large-scale Hercynian magmatic rocks in the Langshan area, followed by the Kongzi rock belt in the Hetao area, and the Archean Ula Mountain Group in the Langshan area. Paleoproterozoic magmatic rocks and early-middle Triassic magmatic rocks may provide some provenances. In addition, according to the youngest age of the clastic zircon is 243Ma (Middle Triassic), combined with the study of the fossil assemblage of predecessors and the characteristics of the whole missing Triassic strata in Langshan area, it is concluded that the age of the strata should be the early and Middle Jurassic. The model of Jurassic sediment source in Langshan area is that the north and south sides are the provenance of uplift, the main provenance is the north side of Langshan uplift, and the south side of the uplift provides some provenances to the north, and there are some differences between different regions.
【作者单位】：西北大学地质学系;西北大学大陆动力学国家重点实验室;中石油东方地球物理公司研究院长庆分院;西安地质矿产勘查开发院;
【基金】：西北大学大陆动力学国家重点实验室科技部专项项目(编号:BJ08133-14BJ081334-2) 国家自然科学基金项目(批准号:4133031540902032) 国家科技油气重大专项项目(编号:2011ZX05023-001-002) 中国地质调查局项目(编号:12120114009201)
【分类号】：P534.52;P597.3

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