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东昆仑浪麦滩地区A型花岗岩年代学、地球化学特征及其地质意义
投稿时间:2020-10-28  修订日期:2020-12-14  点此下载全文
引用本文:
DOI:10.19762/j.cnki.dizhixuebao.2021115
摘要点击次数: 106
全文下载次数: 108
作者单位地址
李金超 中国地质调查局西安地质调查中心 西安市友谊东路438号
国显正 中国地质调查局西安地质调查中心 合肥工业大学 资源与环境工程学院,合肥,230009
孔会磊 中国地质调查局西安地质调查中心 
姚学钢 中国地质调查局西安地质调查中心 
贾群子 中国地质调查局西安地质调查中心 
基金项目:中国地质调查局项目(编号 DD20190143,DD20160013)、第二次青藏高原综合科学考察研究项目(编号2019QZKK0801)
中文摘要:东昆仑造山带出露大面积的花岗岩,是研究岩浆活动的天然实验室,晚三叠世A型花岗岩为该区构造演化提供了新的约束。本文通过对东昆仑浪麦滩地区出露的正长花岗岩开展岩相学、锆石U-Pb定年、Hf同位素及地球化学研究,以期限定其形成时代,探讨岩石成因,并为区域构造岩浆演化提供依据。正长花岗岩由正长石、条纹长石、斜长石、石英和少量黑云母等矿物组成。LA-ICP-MS锆石U-Pb年龄为231.5±1.7Ma,形成于晚三叠世。岩石地球化学具有高硅富铝特征,SiO2含量介于72.36%~74.58%,Al2O3含量介于12.76%~12.89%之间,相对富钾贫钠,K2O、Na2O含量分别在4.43%~4.96%,4.0%~4.25%之间,低MgO、TiO2,富集Rb、K等大离子亲石元素,强烈亏损Ba、Nb、Ta、P、Ti等高场强元素,具有明显的负铕异常(δEu=0.04~0.08),表明为A型花岗岩。Mg#介于0.4~0.43之间,εHf(t)值介于+2.05~+7.53之间,二阶段Hf模式年龄TDM2介于782~1132Ma,指示源区有幔源岩浆物质的参与。综合分析表明,在后碰撞伸展背景下由于幔源岩浆底侵,新生地壳部分熔融并混入幔源物质,最终形成浪麦滩地区A型花岗岩。
中文关键词:正长花岗岩  锆石U-Pb定年  地球化学  Lu-Hf 同位素  东昆仑
 
Geochronology, geochemical characteristics and geological significance of A-type granite from the Langmaitan area, East Kunlun
Author NameAffiliationAddress
LI Jinchao Xi’an Center of Geological Survey,CGS,MLR Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposit,Xi’an 西安市友谊东路438号
GUO Xianzheng Xi’an Center of Geological Survey,CGS,MLR Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposit,Xi’an 合肥工业大学 资源与环境工程学院,合肥,230009
KONG Huilei Xi’an Center of Geological Survey,CGS,MLR Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposit,Xi’an 
YAO Xuegang Xi’an Center of Geological Survey,CGS,MLR Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposit,Xi’an 
JIA Qunzi Xi’an Center of Geological Survey,CGS,MLR Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposit,Xi’an 
Abstract:East Kunlun distributed large areas of intermediate-acid intrusive rocks, providing a natural laboratory for the study of magmatism, and the Late Triassic A-type granites provided new constraints for the tectonic evolution in this area. In this paper, we present a detailed investigation of zircon U-Pb dating, whole rock geochemistry and Hf isotopes of Langmaitan syenogranite in the eastern segment of East Kunlun, in order to identify the chronology and petrogenesis of rocks, and provide a basis data for the evolution of regional tectonics. Syenogranite consists mainly of orthoclase, perthite, plagioclase, quartz, and a small amount of biotite. The zircon U-Pb dating yields an age of 231.5±1.7 Ma, indicating its emplacement in Late Triassic. The syenogranite is geochemically characterized by high SiO2 (72.36%~74.58%) and rich Al2O3 (12.76%~12.89%); relatively rich in K2O (7.52%~7.89%), but poor in Na2O (4.0%~4.25%), low MgO and TiO2; enriched in large ion lithophilic elements Rb, K, etc, depleted high field strength elements such as Ba, Nb, Ta, P, Ti, significantly negative europium anomalies (δEu = 0.04~0.08), these characteristics indicate that they are A-type granites. Mg# is between 0.4 and 0.43, the εHf(t) value is between +2.05 and +7.53, and TDM2 ages between 782 and 1132 Ma, indicating that the syenogranite involvement of mantle components in petrogenesis. Based on the comprehensive regional geology and the characteristics, the Langmaitan A-type granite formed by partial melting of juvenile crust and mixed with mantle-derived materials in post-collision extensional environment.
keywords:Syenogranite  Zircon U-Pb dating  Geochemistry  Lu-Hf isotopes  East Kunlun
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