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东秦岭神林花岗岩的锆石U-Pb定年、地球化学特征及构造背景
投稿时间:2020-10-22  修订日期:2021-05-31  点此下载全文
引用本文:梁涛,卢仁,刘小丽.2021.东秦岭神林花岗岩的锆石U-Pb定年、地球化学特征及构造背景[J].地质论评,67(5):1245-1262,[DOI]:.
LIANG Tao,LU Ren,LIU Xiaoli.2021.Zircon U-Pb age,geochemical features of the Shenlin granite,eastern Qinling Orogenic Belt,and its implications for tectonic settings[J].Geological Review,67(5):1245-1262.
DOI:10.16509/j.georeview.2021.06.051
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作者单位E-mail
梁涛 1)河南省有色金属地质勘查总院郑州450052
2)河南省有色金属深部找矿勘查技术研究重点实验室郑州450052 
liang20010212@126.com 
卢仁 1)河南省有色金属地质勘查总院郑州450052
2)河南省有色金属深部找矿勘查技术研究重点实验室郑州450052 
 
刘小丽 1)河南省有色金属地质勘查总院郑州450052
2)河南省有色金属深部找矿勘查技术研究重点实验室郑州450052 
 
基金项目:本文为国家自然科学基金资助项目(编号:U1504405)、河南省国土资源厅科技攻关项目(编号:2016-08和2014-06)的成果
中文摘要:神林花岗岩能够为反演东秦岭燕山期区域构造演化提供新的制约。它的主体岩性为斑状黑云母二长花岗岩,其锆石LA-ICP-MS U-Pb同位素定年结果为130.6±0.7 Ma。神林花岗岩样品具有高硅富碱和贫镁低钙的特征,属于高钾钙碱性系列,以准铝质—弱过铝质为主。它们富集大离子亲石元素(如Rb、Th和K)和亏损高场强元素(如Nb、Ta和Ti),具有轻稀土富集、重稀土亏损的特征,其(La/Yb)N范围为17.6~22.2,δEu值为0.59~0.72。在LaN—(La/Yb)N图解中,神林花岗岩样品显示正相关关系,表明是源区组成和部分熔融作用控制其成分变异。神林花岗岩样品显示了高Sr、低Y和Yb的特征,Sr/Y值为24.3~37.9,属于高锶低钇中酸性岩(adakite,有人音译为埃达克岩)。神林花岗岩形成于加厚大陆下地壳的部分熔融,其源区深度大于50km,部分熔融源区残余相包括石榴子石、金红石和角闪石,无或者少量的斜长石。神林花岗岩锆石具有轻稀土亏损、重稀土富集、Ce正异常的特征,锆石的形成温度介于624~701 ℃之间,重稀土元素分配系数与年龄的变化特征表明神林花岗岩经历了深部岩浆/流体的注入与混合,这与暗色微粒包体所揭示的神林花岗岩深部成岩过程相吻合。混合活化后的岩浆/流体体系沿区域深大断裂上侵,在其次级断裂带内的断裂交汇处就位成岩。神林花岗岩形成于东秦岭陆(板)内造山阶段,是约131 Ma区域岩石圈拆沉作用的岩浆响应。
中文关键词:神林花岗岩  U-Pb定年  锆石稀土元素  岩浆混合  岩石圈拆沉  东秦岭
 
Zircon U-Pb age,geochemical features of the Shenlin granite,eastern Qinling Orogenic Belt,and its implications for tectonic settings
NameInstitution
LIANG Tao1)General Institute of Non-ferrous Metals Geological Exploration of Henan Province,Zhengzhou,450052;2)Key Laboratory of Deep Ore-prospecting technology Research for Non-ferrous Metals of Henan Province,Zhengzhou,450052
LU Ren1)General Institute of Non-ferrous Metals Geological Exploration of Henan Province,Zhengzhou,450052;2)Key Laboratory of Deep Ore-prospecting technology Research for Non-ferrous Metals of Henan Province,Zhengzhou,450052
LIU Xiaoli1)General Institute of Non-ferrous Metals Geological Exploration of Henan Province,Zhengzhou,450052;2)Key Laboratory of Deep Ore-prospecting technology Research for Non-ferrous Metals of Henan Province,Zhengzhou,450052
Abstract:The Shenlin granite is located in the eastern Qinling Orogenic Belt,which emplaced in Yanshanian.The Shenlin granite provides us an opportunity to revealing the tectonic evolution history in the eastern Qinling Orogenic Belt during Yanshanian.Methods: Based on detailed field observations of the Shenlin granite in the eastern Qinling Orogenic Belt,we have studied the petrology,geochemistry and chronology of the Shenlin granite.The petrogenesis and deep tectonic implications of the Shenlin granite was discussed.Results:The zircon LA-ICP-MS U-Pb dating was used to constrain the formation age of the Shenlin granite.The 27 of 30 zircon spots of the Shenlin granite yield a n(206Pb)/n(238U) age of 130.6±0.7 Ma (MSWD=2.1).The Shenlin granite are characterized by higher in SiO2 and alkali,and lower in MgO and CaO contents.The Shenlin granite belong to high-K calc-alkaline series in the SiO2—K2O diagram, and metaluminous to weakly peraluminous with A/CNK ratios of 0.99~1.03. The Shenlin granite samples are enriched in large ion lithophile elements (e.g.,Rb,Th and K) and depleted in high field-strength elements (e.g.,Nb,Ta and Ti).In chondrite-normalized rare earth element (REE) patterns,the Shenlin granite samples exhibit light rare earth element (LREE) enrichment and heavy rare earth element (HREE) depletion with δEu values of 0.59~0.72.The linear trend of the Shenlin granite samples in LaN—(La/Yb)N diagram has suggested that the compositional change is controlled mainly by source and degree of partial melting.The Shenlin granite samples are with high Sr,and low Y and Yb contents,with the Sr/Y ratios of 24.3~37. 9 that is indicative of adakite affinity.The Shenlin granite is originated from partial melting of the thickened lower crust with thickness > 50 km,and its residual phases include garnet, rutile and amphibolite,and minor plagioclase.In chondrite-normalized REE patterns of zircons,the characteristics of LREE-depleted,HREE- enriched with Ce positive anomaly are shown, and the zircon formation temperatures are calculated from 624℃ to 701℃. The variation of HREE partition coefficients with ages in the zircon/melts system of the Shenlin granite indicates that it has experienced injection,mixing and activation of the magma/fluids,which is consistent with mafic microgranular enclave in this intrusion.The activated magma/fluids system were intruded along the regional huge fault, and emplacement and consolidation formed the Shenlin granite took place at the fault intersection in the secondary faults.Conclusions:The Early Cretaceous Shenlin granite belongs to adakite,which originated from partial melting of the thickened lower crust with a thickness of > 50 km.It was intruded during intracontinental (intraplate) orogenesis in the eastern Qinling Orogenic Belt,which was triggered by regional lithosphere delamination.
keywords:Shenlin granite,U-Pb isotopic dating,REE of zircon,magma mixing  lithosphere delamination  eastern Qinling Orogenic Belt
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