鄂尔多斯盆地北部中生代中晚期地层碎屑锆石U-Pb定年与物源示踪
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大陆动力学国家重点实验室,西北大学地质学系

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国家自然科学基金项目(面上项目,重点项目,重大项目)


Detrital Zircon U-Pb Dating of Middle-Late Mesozoic Strata in the Northern Ordos Basin: Implications for Tracing Sediment Sources
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State key Laboratory of Continental Dynamics,Department of Geology,Northwest University

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    摘要:

    本文采用LA-ICP-MS碎屑锆石原位微区测年方法,对鄂尔多斯盆地北部杭锦旗地区中侏罗统直罗组和下白垩统志丹群进行了砂岩碎屑锆石U-Pb年龄分布及其变化特征研究,统计和对比了前人对该区周缘岩体的同位素年代学结果,结合区域构造背景,系统地研究了盆地北部直罗组及志丹群地层物源及其演变。结果表明: ①4个直罗组样品和2个志丹群样品锆石年龄总体呈现出270~280Ma、320~340Ma、1800~2000Ma、2300~2500Ma 4个峰值年龄段,在志丹群样品中出现有少量230~240Ma锆石年龄;②杭锦旗地区上述砂岩的物源主要来自阴山、大青山—乌拉山的片麻岩、麻粒岩、孔兹岩以及形成于海西期的中酸性侵入岩,同时也有狼山地区岩体、集宁地区孔兹岩的一部分贡献;③1800~2000Ma、2300~2500Ma峰值年龄均为华北克拉通基底构造热事件的反映,270~280Ma、320~340Ma两个峰值年龄可能记录了早石炭世—中二叠世古亚洲洋向华北板块北缘的两次快速俯冲事件;④下白垩统志丹群样品中出现的230~240Ma的锆石,指示晚侏罗世的燕山运动在盆地北缘引起的强烈逆冲推覆造山作用使得印支期侵入岩被抬升至地表并遭受剥蚀,从而为研究区地层进一步增加了来自蚀源区印支期侵入岩的物源;⑤与中侏罗统直罗组样品相比,下白垩统志丹群样品在2300~2500Ma峰值测点所占比例明显增加,这可能是由于早白垩世时期盆地北部沉积边界较中侏罗世相对扩展,使来自阴山的物源比例增加。

    Abstract:

    The distribution of U-Pb ages and their variation features have been comprehensively studied using LA-ICP-MS in-situ isotopic dating of the detrital zircons from sandstones of Zhiluo Formation of the Middle Jurassic and Zhidan Group of the Early Cretaceous from the Hangjinqi area, Ordos basin. Based on the statistic and comparison of isotopic dating results for the plutons in and around this area by previous researchers, along with regional structural background, the provenance of Zhiluo Formation and Zhidan Group and their evolution was also addressed systematically. The main conclusions can be drawn as follows. (1) Zircons from four samples of Zhiluo Formation and two samples of Zhidan Group yielded four peak ages of 270~280 Ma, 320~340 Ma, 1800~2000 Ma, 2300~2500 Ma, with minor zircons from the Zhidan Group having age range from 230 Ma to 240 Ma only appear. (2) The sandstones in the Hangjinqi area mainly sourced from the gneisses, granulites, khondalite and the Hercynian intermediatefelsic intrusive rocks in Yinshan and DaqingshanWulashan, with minor from Langshan and the khondalite from the Jining area. (3) The two ages of 1800~2000 Ma and 2300~2500 Ma may reflect the tectonic thermal event at the basement of the North China Craton. The two age of 270~280 Ma and 320~340 Ma may record two fast subduction events of the PaleoAsian Ocean which occurred during Early Carboniferous to Middle Permian. (4) The 230~240 Ma zircon which appeared in the Zhidan Group indicates that the Indosinian intrusive rock was uplifted to the surface by intensive crustal overthrusting caused by the Yanshan movement in Late Jurassic in the northern margin of Ordos Basin, and denudation further increased provenance from the Indosinian intrusive rock for the study area. (5) Comparison with the samples from the midJurassic Zhiluo Formation shows that peak points of the samples from the lower Cretaceous Zhidan Group at 2300~2500 Ma significantly increase. This probably resulted from relative expansion of the sedimentary boundary in the northern margin of the basin in the Early Cretaceous, thus increasing provenance proportion from the Yinshan Terran.

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雷开宇,刘池洋,张龙,吴柏林,王建强,寸小妮,孙莉.2017.鄂尔多斯盆地北部中生代中晚期地层碎屑锆石U-Pb定年与物源示踪[J].地质学报,91(7):1522-1541.
LEI Kaiyu, LIU Chiyang, ZHANG Long, WU Bolin, WANG Jianqiang, CUN Xiaoni, SUN Li.2017. Detrital Zircon U-Pb Dating of Middle-Late Mesozoic Strata in the Northern Ordos Basin: Implications for Tracing Sediment Sources[J]. Acta Geologica Sinica,91(7):1522-1541.

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  • 收稿日期:2016-06-17
  • 最后修改日期:2016-12-06
  • 录用日期:2016-12-27
  • 在线发布日期: 2017-07-11
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