造山带内微陆块地壳的增生与再造过程:以额尔古纳地块为例
发布时间：2019-02-15 03:18
【摘要】：系统总结并分析了近年来获得的额尔古纳地块中生代花岗岩的年代学、地球化学和Hf同位素数据,以便从Hf同位素时空变异角度揭示额尔古纳地块陆壳增生及再造过程,为造山带地壳演化提供证据.基于花岗岩锆石U-Pb定年结果,额尔古纳地块中生代花岗质岩浆作用至少可划分五个阶段:早-中三叠世(249~237Ma)、晚三叠世(229~201Ma)、早-中侏罗世(199~171Ma)、晚侏罗世(155~149Ma)和早白垩世(145~125Ma).其中,前三个侵入阶段的花岗岩主要为I型花岗岩,而后两个阶段为A型花岗岩,反映中生代蒙古-鄂霍茨克大洋板块俯冲-碰撞-伸展过程导致额尔古纳地块陆壳由加厚向减薄变化的特征.中生代花岗岩中锆石Hf同位素分析结果表明,额尔古纳地块陆壳增生主要发生于中元古代及新元古代,并且这些中生代花岗岩具有随时代变新εHf(t)值逐渐升高、二阶段模式年龄(TDM2)逐渐下降的变化趋势,揭示额尔古纳地块中生代不同期次花岗质岩浆的产生经历了从古老陆壳物质熔融至新增生陆壳物质熔融的变化过程.此外,锆石Hf同位素组成在空间上还具有随纬度增加εHf(t)值逐渐下降、二阶段模式年龄(TDM2)逐渐升高的变化特征,显示出研究区深部陆壳物质组成中古老陆壳成分由南向北增多的趋势.而在同一纬度范围内,锆石Hf同位素组成也存在差异.这些结果表明额尔古纳地块深部陆壳在横向和垂向上均存在明显的不均一性.综合上述特征,本文提出了额尔古纳地块下部陆壳的结构模型.
[Abstract]:The geochronological, geochemical and Hf isotopic data of the Mesozoic granites in the Erguna massif obtained in recent years are systematically summarized and analyzed in order to reveal the process of crustal accretion and reconstruction in the Erguna block from the point of view of Hf isotopic temporal and spatial variation. Provide evidence for crustal evolution of orogenic belts. Based on the U-Pb dating of granite zircon, the Mesozoic granitic magmatism in the Erguna block can be divided into at least five stages: early and Middle Triassic (249~237Ma), late Triassic (229~201Ma), early and Middle Jurassic (199~171Ma). Late Jurassic (155~149Ma) and early Cretaceous (145~125Ma). Among them, the granites in the first three intrusive stages are mainly I-type granites, and the last two stages are A-type granites. The results show that the Mesozoic Mongolian-Okhotsk oceanic plate subducted collision-extensional process leads to the change from thickening to thinning of the Erguna block continental crust. The Hf isotopic analysis of zircon from Mesozoic granites shows that the continental crust accretion occurred mainly in Mesoproterozoic and Neoproterozoic, and these Mesozoic granites have gradually increased 蔚 Hf (t) value. The decreasing trend of the two-stage model age (TDM2) reveals that the generation of granitic magma in the Erguna massif experienced a process from the melting of the ancient continental crust to the melting of the newly formed continental crust. In addition, the Hf isotopic composition of zircon has the characteristics of decreasing 蔚 Hf (t) value and increasing TDM2 with the increase of latitude. It is shown that the composition of the ancient continental crust in the deep continental crust in the study area is increasing from south to north. In the same latitudes, the Hf isotopic compositions of zircon are also different. These results indicate that the deep continental crust of the Erguna block has obvious heterogeneity both horizontally and vertically. Based on the above characteristics, a structural model of the lower continental crust of the Erguna block is proposed.
【作者单位】： 吉林大学地球科学学院;
【基金】：国家重点研发计划项目(编号:2016YFC0600403) 国家自然科学基金项目(批准号:41330206)资助
【分类号】：P542
[Abstract]:The geochronological, geochemical and Hf isotopic data of the Mesozoic granites in the Erguna massif obtained in recent years are systematically summarized and analyzed in order to reveal the process of crustal accretion and reconstruction in the Erguna block from the point of view of Hf isotopic temporal and spatial variation. Provide evidence for crustal evolution of orogenic belts. Based on the U-Pb dating of granite zircon, the Mesozoic granitic magmatism in the Erguna block can be divided into at least five stages: early and Middle Triassic (249~237Ma), late Triassic (229~201Ma), early and Middle Jurassic (199~171Ma). Late Jurassic (155~149Ma) and early Cretaceous (145~125Ma). Among them, the granites in the first three intrusive stages are mainly I-type granites, and the last two stages are A-type granites. The results show that the Mesozoic Mongolian-Okhotsk oceanic plate subducted collision-extensional process leads to the change from thickening to thinning of the Erguna block continental crust. The Hf isotopic analysis of zircon from Mesozoic granites shows that the continental crust accretion occurred mainly in Mesoproterozoic and Neoproterozoic, and these Mesozoic granites have gradually increased 蔚 Hf (t) value. The decreasing trend of the two-stage model age (TDM2) reveals that the generation of granitic magma in the Erguna massif experienced a process from the melting of the ancient continental crust to the melting of the newly formed continental crust. In addition, the Hf isotopic composition of zircon has the characteristics of decreasing 蔚 Hf (t) value and increasing TDM2 with the increase of latitude. It is shown that the composition of the ancient continental crust in the deep continental crust in the study area is increasing from south to north. In the same latitudes, the Hf isotopic compositions of zircon are also different. These results indicate that the deep continental crust of the Erguna block has obvious heterogeneity both horizontally and vertically. Based on the above characteristics, a structural model of the lower continental crust of the Erguna block is proposed.
【作者单位】： 吉林大学地球科学学院;
【基金】：国家重点研发计划项目(编号:2016YFC0600403) 国家自然科学基金项目(批准号:41330206)资助
【分类号】：P542
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本文编号：2422907
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