西秦岭恰盖地区大草滩组碎屑锆石U-Pb年代学及物源分析
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1.中国地质调查局西安矿产资源调查中心;2.中国地质科学院矿产资源研究所;3.长庆油田分公司油气工艺研究院

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Detrital Zircon U–Pb Age and Provenance Analysis of Dacaotan Formation at Qiagai Area in the West Qinling Orogenic Belt
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1.Xi'2.'3.an Center of Mineral Resources Survey, China Geological Survey;4.Institute of Mineral Resources, CAGS;5.Oil and Gas Technology Research Institute of Changqing Oilfield Company, CNPC

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    摘要:

    大草滩组形成时代及物质来源尚有诸多争议,因此本文运用LA-ICP-MS锆石U-Pb同位素年代学方法,对西秦岭造山带恰盖地区大草滩组碎屑岩进行研究,探讨其形成时代进而推测物质来源。结果表明,碎屑锆石年龄数据可分为以下4组:①太古代-古元古代(2232~3258Ma);②中元古代(1018~1791Ma);③新元古代(544~999Ma);④早古生代(417~519Ma)。其中,早古生代(417~519Ma)的年龄数据所占比例最大,约占总体的39.6%,且呈现出最强烈的峰值年龄504.4Ma;其次是新元古代(544~999Ma)年龄组分,约占37.3%;其他两组年龄段所占比例则较少。初步物源分析认为,大草滩组沉积物质来源较复杂,具有明显的多元和多期次的特征。物质来源包括西秦岭造山带北缘、祁连造山带东段和华北板块基底三处,其中西秦岭造山带北缘和祁连造山带在加里东期洋壳持续俯冲大陆边缘形成的岩浆岩为主要物质来源。

    Abstract:

    There are many disputes about the the age and prowenance of Dacaotan Formation, With clastic rocks of the Upper Devonian Dacaotan Formation at Qiagai area in the West Qinling Orogenic belt as the study object, the authors used LA-ICP-MS zircon U-Pb isotope geochronological method to explore the age and prowenance of Dacaotan Formation. The results show that the detrital zircon ages can be divided into 4 groups: (1)The Archen-Paleoproterzoic(2232-3258Ma); (2)The Mesoproterzoic(1018-1791Ma); (3) The Neoproterzoic(544-999Ma); (4)The Early Paleozoic(417-519Ma). Among which, the Early Paleozoic(417-519Ma) ages data possess the largest proportion, accounting for about 39.6% of the total data. The lesser is the Neoproterzoic(544-999Ma) ages, about 37.3%. The other two groups ages possess a smaller proportion. Preliminary analysis show that, the provenance source of Dacaotan Formation were much more complicated and characterized by obvious diversity and periods, derived from northern margin of western Qinling orogenic belt, the eastern part of the Qilian orogenic belt and the basement of North China plate. The predominant part among them was the active magmatic arc produced by collision orogen, which come from the northern margin of western Qinling orogenic belt and Qilian orogenic belt during the Caledonian period.

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  • 收稿日期:2021-04-12
  • 最后修改日期:2022-01-08
  • 录用日期:2022-03-13
  • 在线发布日期: 2023-02-15
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