辽东桓仁地区中生代花岗岩锆石U-Pb年龄、Hf同位素特征及其地质意义
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本文为中国地质调查局地质调查项目“辽宁1/5万响水河子等两幅区域地质调查(编号DD20160049-9)”资助的成果


Zircon U-Pb ages,Hf isotope composition,and geochemical characteristics of Mesozoic granite in Huanren area, Eastern Liaoning
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  • 1)辽宁省地质矿产调查院有限责任公司,沈阳,110031    
  • 2)中国地质调查局海口海洋地质调查中心,海口,571127    
  • 1)辽宁省地质矿产调查院有限责任公司,沈阳,110031    
  • 1)辽宁省地质矿产调查院有限责任公司,沈阳,110031    
  • 1)辽宁省地质矿产调查院有限责任公司,沈阳,110031    
  • 1)辽宁省地质矿产调查院有限责任公司,沈阳,110031    
  • 1)辽宁省地质矿产调查院有限责任公司,沈阳,110031    
  • 1)辽宁省地质矿产调查院有限责任公司,沈阳,110031    
  • 1)Liaoning Survey Academy of Geology and Mineral Resources Investigation,Shenyang,110031    
  • 2)Haikou MarineGeological Survey Center, China Geological Survey, Haikou,571127    
  • 1)Liaoning Survey Academy of Geology and Mineral Resources Investigation,Shenyang,110031    
  • 1)Liaoning Survey Academy of Geology and Mineral Resources Investigation,Shenyang,110031    
  • 1)Liaoning Survey Academy of Geology and Mineral Resources Investigation,Shenyang,110031    
  • 1)Liaoning Survey Academy of Geology and Mineral Resources Investigation,Shenyang,110031    
  • 1)Liaoning Survey Academy of Geology and Mineral Resources Investigation,Shenyang,110031    
  • 1)Liaoning Survey Academy of Geology and Mineral Resources Investigation,Shenyang,110031    
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    摘要:

    本文对辽东桓仁地区出露的古城子二长花岗岩、业主沟碱长花岗岩开展岩石学、地球化学、锆石U-Pb年代学和Hf同位素研究。岩石学与地球化学特征表明古城子二长花岗岩和业主沟碱长花岗岩分别为准铝质-弱过铝质高分异I型花岗岩和准铝质-弱过铝质A型花岗岩。LA-ICP-MS锆石U-Pb定年结果显示,I型花岗岩成岩年龄为125.0±0.6 Ma, A型花岗岩成岩年龄为116.3±0.9 Ma,二者同为早白垩世岩浆活动的产物。两类花岗岩均富Rb、Th、U、K 和轻稀土,贫Ba、Sr、P、Ti,但二长花岗岩较碱长花岗岩,岩石Rb/Sr、Rb/Ba 比值低,K/Rb 比值高,并表现出更显著的铕负异常,指示两类花岗岩分异演化程度各不相同。两类花岗岩锆石Hf 同位素组成普遍具有较大的变化范围,二长花岗岩εHf(t)变化范围-22.20 ~ -16.02,碱长花岗岩εHf(t)变化范围-15.98 ~ -11.42, εHf(t)值变化范围较大,指示应有多种组分参与成岩过程。综合分析表明,显著的成岩时差及成分变异趋势指示两类花岗岩不可能为同一原始岩浆,两类花岗岩的形成均经历了幔源岩浆与其诱发地壳物质熔融产生的长英质岩浆在地壳深部混合,随后又经不同程度结晶分异的二阶段成岩过程。结合区域构造演化认为两类花岗岩的形成可能与早白垩世晚期太平洋板块向欧亚板块的俯冲和后缘拉张导致岩石圈伸展构造背景有关。

    Abstract:

    This paper conducted petrological, geochemical, zircon U-Pb chronology and Hf isotope studies on the Guchengzi monzogranite and the Yezhugou alkali-feldspar granite in the Huanren area of eastern Liaoning. The petrological and geochemical characteristics show that the Guchengzi monzogranite and the Yezhugou alkali-feldspar granite are respectively metaluminous-weakly peraluminous highly differentiated I-type granite and metaluminous-weakly peraluminous A-type granite. The zircon U-Pb dating results of LA-ICP-MS show that the age of I-type granite is 125.0±0.6 Ma and that of A-type granite is 116.3±0.9Ma, both are the products of Early Cretaceous magmatism. Both granites are enriched in Rb, Th, U, K, and light rare earths, and depleted in Ba, Sr, P, and Ti. However, compared with the alkali-feldspar granite, the monzogranite has lower Rb/Sr and Rb/Ba ratios and a higher K/Rb ratio, and exhibits a more significant negative Eu anomaly, indicating that the two types of granites have different degrees of differentiation and evolution. The zircon Hf isotope compositions of the two types of granites have a relatively large range of variation, with the εHf(t) variation range of -22.20 to -16.02 for diorite granite and -15.98 to -11.42 for alkali feldspar granite. The variation range of ε Hf (t) value is large, indicating that multiple components should be involved in the diagenetic process. The significant differences of diagenetic time and compositions indicate that the two kinds of granites could not have originated from the same primitive magma. The formation of both types of granites has undergone a two-stage diagenetic process in which mantle-derived magma mixed with felsic magma produced by melting crustal material in the deep crust, and followed by different extents of crystallization differentiation. Combined with regional tectonic evolution, the formation of the two types of granites may be related to the extensional tectonic setting of the lithospheric caused by the subduction of the Pacific Plate towards the Eurasian Plate and the extension of the trailing edge in the late Early Cretaceous.

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余超,杨玉伟,田毅,苏特,王广伟,杨新宇,鲍东明,张天元.2024.辽东桓仁地区中生代花岗岩锆石U-Pb年龄、Hf同位素特征及其地质意义[J].地质论评,70(6):2024060032,[DOI].
YU Chao, YANG Yuwei, TIAN Yi, SU Te, WANG Guangwei, YANG Xinyu, BAO Dongming, ZHANG Tianyuan.2024. Zircon U-Pb ages, Hf isotope composition, and geochemical characteristics of Mesozoic granite in Huanren area, Eastern Liaoning[J]. Geological Review,70(6):2024060032.

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  • 收稿日期:2024-07-28
  • 在线发布日期: 2024-12-19