| 豫西济源盆地中三叠世-中侏罗世碎屑锆石年代学及其对秦岭造山带造山过程的启示 |
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| 引用本文： | 杨文涛,杨江海,汪校锋,杜远生.豫西济源盆地中三叠世-中侏罗世碎屑锆石年代学及其对秦岭造山带造山过程的启示[J].地球科学,2012,37(3):489-500. |
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| 作者姓名： | 杨文涛 杨江海 汪校锋 杜远生 |
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| 作者单位： | 中国地质大学生物地质与环境地质国家重点实验室, 湖北武汉 430074 |
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| 基金项目： | 国家自然科学基金40921062河南1∶5万古城(I49E006016)、段村(I49E007016)、观音堂(I49E008015)、渑池县(I49E008016)幅区域地质调查项目1212011120766 |
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| 摘 要： | 豫西济源盆地位于秦岭造山带北部, 是三叠纪-侏罗纪秦岭造山带的同造山盆地.对济源盆地中三叠世-中侏罗世6个组的碎屑锆石样品进行了LA-ICP-MS的U-Pb年龄分析.结果表明, 碎屑锆石年龄主要分布于以下区间: 2.9~1.7 Ga、1.6~1.0 Ga、1.0~0.8 Ga、800~650 Ma、520~380 Ma、350~245 Ma和~220 Ma, 其中除了2.9~1.7 Ga的碎屑锆石主要来自于华北克拉通基底外, 其他几个年龄段的锆石则主要来自于秦岭造山带, 并且显示出随着地层年龄的逐渐变新, 碎屑锆石年龄有逐渐变老的趋势.在中三叠世-晚三叠世早期样品中, 主要年龄是350~245 Ma, 在晚三叠世晚期-中侏罗世早期样品中, 1.6~1.0 Ga、1.0~0.8 Ga、800~650 Ma和520~380 Ma则逐渐增多, 到了中侏罗世晚期, 1.6~1.0 Ga和520~380 Ma依然存在于样品中, 并且还发现了~220 Ma年龄.碎屑锆石年龄结构指示了秦岭造山带印支期经历了由年轻的盖层到较老的基底的去顶过程.并与合肥、黄石盆地的碎屑锆石数据对比发现, 早侏罗世时, 去顶强度东强西弱; 东部高压-超高压变质岩或晚三叠世岩体可能暴露于早侏罗世, 而西部则到了中侏罗世.
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| 关 键 词： | 济源盆地 秦岭造山带 碎屑锆石 物源分析 去顶样式 地质年代学 沉积学 |
| 收稿时间： | 2011-05-10 |
Geochronology from Middle Triassic to Middle Jurassic Detrital Zircons in Jiyuan Basin and Its Implications for the Qinling Orogen |
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| Abstract: | Jiyuan basin is located in the north of Qinling orogen and regarded as a Triassic-Jurassic synorogenic basin. This paper presents a great number of detrital zircon U-Pb ages for synorogenic sediments in age ranging from the Middle Triassic to Middle Jurassic in the Jiyuan basin. The results show seven major age groups at 2.9-1.7 Ga, 1.6-1.0 Ga, 1.0-0.8 Ga, 800-650 Ma, 520-380 Ma, 350-245 Ma and ~220 Ma. It is obvious that age group of 2.9-1.7 Ga is directly derived from the Precambrian basement of North China Craton whereas other groups are typical characteristics of the Qinling orogenic belt. An important observation is that the Qinling-sourced detrital zircons become older from the Middle Triassic to the Early Jurassic sedimentary sequences, which is characterized by the main age clusters at 350-245 Ma occurring in the T2-T31 strata while age groups at 1.6-1.0 Ga, 1.0-0.8 Ga, 800-650 Ma and 520-380 Ma increase successively in the T32-J21 samples. In addition, little grains of age groups at 1.6-1.0 Ga, 520-380 Ma and ~220 Ma are presented in the J22 sample. The above-mentioned findings indicate that unroofing pattern of Qinling orogenic belt developed by the denudation of sendiments from young covers to old basements in order, then to the Carnian plutons. Integrated with the data reported from Hefei and Huangshi basins, it is well established that the intensity of unroofing increased from the west to the east in the Early Jurassic, and the denudation timing of the ultra high pressure (UHP)-high pressure (HP) rocks or Carnian plutons changed successively from the Early Jurassic in the east to the Middle Jurassic in the west. |
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