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滇西凤庆地区箐头山花岗岩的特征——古特提斯洋碰撞汇聚向伸展转换的证据
投稿时间:2020-12-09  修订日期:2021-06-11  点此下载全文
引用本文:田素梅,刘军平,范振华,包佳凤,孙柏东,俞赛赢,吴嘉林,朱勋早,宋冬虎.2021.滇西凤庆地区箐头山花岗岩的特征——古特提斯洋碰撞汇聚向伸展转换的证据[J].地质论评,67(5):1280-1296,[DOI]:.
TIAN Sumei,LIU Junping,FAN Zhenhua,BAO Jiafeng,SUN Baidong,YU Saiying,WU Jialin,ZHU Xunzao,SONG Domghu.2021.Age and geochemical characteristics of Qingtoushan granite in Fengqing area,Western Yunnan——Transition evidences for collision convergence to extension of the Paleo-Tethys Ocean[J].Geological Review,67(5):1280-1296.
DOI:10.16509/j.georeview.2021.06.091
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作者单位E-mail
田素梅 1)云南省地质调查院昆明6502162)自然资源部三江成矿作用及资源勘查利用重点实验室昆明650051 313470364@qq.com 
刘军平 1)云南省地质调查院昆明6502162)自然资源部三江成矿作用及资源勘查利用重点实验室昆明650051  
范振华 3)山东省第一地质矿产勘查院济南250100 158524564@qq.com 
包佳凤 1)云南省地质调查院昆明650216  
孙柏东 1)云南省地质调查院昆明650216  
俞赛赢 1)云南省地质调查院昆明6502162)自然资源部三江成矿作用及资源勘查利用重点实验室昆明650051  
吴嘉林 1)云南省地质调查院昆明650216  
朱勋早 1)云南省地质调查院昆明650216  
宋冬虎 4)云南省国土规划设计院昆明650216  
基金项目:本文为国家自然科学基金地区基金资助项目(编号:420602005)、国家自然科学基金特提斯重大研究计划重点项目(编号:92055207)和西南三江有色金属资源基地调查项目(编号:DD20160016)子项目云南省1∶5万诗礼、犀牛街、大河、老家库、哨街幅区域地质矿产调查项目的成果
中文摘要:笔者等在野外调查的基础上,对出露于滇西临沧岩浆弧北部凤庆箐头山地区原1∶25万凤庆县幅划分的二叠纪糜棱岩化黑云二长花岗岩进行了系统的年代学、岩石学和地球化学研究。该花岗岩体中,锆石具典型的振荡环带,Th/U值均大于0.2,为岩浆成因,其 LA-ICP-MS U-Pb 年龄为 213±5 Ma, 应当为岩浆结晶年龄,表明该岩体形成于晚三叠世,而非前人认为的二叠纪。全岩主微量元素分析结果显示,箐头山花岗岩Na2O/K2O 值低,富Al2O3,铝饱和指数(A/NCK值)平均为1.18,属过铝质高钾钙碱性系列。稀土配分曲线右倾,具有轻稀土富集、重稀土弱亏损、负铕异常明显的特征 (δEu=0.36~0.50);富集大离子亲石元素Rb和K,亏损高场强元素Zr。在Rb—(Y+Nb)判别图解中,箐头山花岗岩投影点落入后碰撞花岗岩区,并具有明显向板内花岗岩转换的特征。结合区域地质资料,笔者等认为获得的213 Ma可能代表昌宁—孟连古特提斯洋闭合之后地壳由碰撞后造山向构造伸展转换的时限,为昌宁—孟连古特提斯洋碰撞后造山作用的结束提供时代约束。
中文关键词:锆石U-Pb测年  地球化学  昌宁—孟连结合带  弧—陆碰撞  箐头山花岗岩  凤庆
 
Age and geochemical characteristics of Qingtoushan granite in Fengqing area,Western Yunnan——Transition evidences for collision convergence to extension of the Paleo-Tethys Ocean
NameInstitution
TIAN Sumei1)Yunnan Institute of Geological Survey,Kunming,650216;2)Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,MNR,Kunming,650051
LIU Junping1)Yunnan Institute of Geological Survey,Kunming,650216;2)Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,MNR,Kunming,650051
FAN Zhenhua3)Institute of Geology and Mineral Resources of Shandong Province,Jinan,250100
BAO Jiafeng1)Yunnan Institute of Geological Survey,Kunming,650216;2)Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,MNR,Kunming,650051
SUN Baidong1)Yunnan Institute of Geological Survey,Kunming,650216
YU Saiying1)Yunnan Institute of Geological Survey,Kunming,650216;2)Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,MNR,Kunming,650051
WU Jialin1)Yunnan Institute of Geological Survey,Kunming,650216
ZHU Xunzao1)Yunnan Institute of Geological Survey,Kunming,650216
SONG Domghu4)Yunnan Institute of Land and Resources Planning and Design,Kunming,650216
Abstract:Geologists at home and abroad have done a lot of research on the evolution of the Paleo-Tethyan ocean in the Changning—Menglian suture zone,but there is still a lack of precise chronological constraints on the end time of post collisional orogeny after its closure.We study the emplacement age,genetic type and material source of Qingtoushan granite,located in the northern part of Lincang magmatic arc,in Fengqing area,western Yunnan Province,so as to constrain the post collisional orogeny after the closure of Changning—Menglian ocean basin.Methods: Combined with the results of 1∶50000 and 1∶250000 Regional Geological and Mineral Survey Projects in recent years,we studied the petrology,geochemistry and LA-ICP-MS zircon U-Pb dating of mylonitized biotite monzogranite exposed in the Qingtoushan area,providing evidence for the structural evolution of the Changning—Menglian suture zone.Results: The LA-ICP-MS zircon U-Pb dating of the Qingtoushan granite yielded a magma crystallization age of 213 ± 5 Ma (mswd = 3.4,n= 14),which is attribute to characteristics of typical oscillatory zoning,and Th / U ratios greater than 0.2.The granite belong to peraluminous high-K calc-alkaline series,with low Na2O / K2O ratio,rich in Al2O3,and the average Al saturation index A / NCK is 1.18.The REE distribution curves have the characteristics of right deviation LREE enrichment,weak depletion on HREE,and obviously negative anomacies of Eu (δEu = 0.36~0.50). The granites enriched lithophile elements Rb,K and the high field strength elements such as Zr depleted.In the Rb—(Y+Nb) discrimination diagrams of trace elements, the projection points fall into the post-COLG,which have the characteristics of obviously transformed to intraplate granite.Conclusions: The crystallization age of 213±5 Ma indicates that the Qingtoushan granite was formed in the Late Triassic rather than the Permian.It is the youngest acid magma with the dual properties of post collisional granite and intraplate granite discovered in the Lincang magmatic arc so far,suggesting that the Changning—Menglian suture zone has entered the intracontinental extension stage,and the tectonic environment at that time has changed from compressional collision to extensional one.This age may provide constraints on the end of post collisional orogeny after the closure of Changning—Menglian Paleo-Tethys ocean.
keywords:Zircon U-Pb dating  geochemistry  Changning—Menglian suture zone  arc—continent collision  Qingtoushan granite  Fengqing
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