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滇西澜沧岩群钠长浅粒岩锆石U?Pb测年、Hf同位素组成及构造意义
投稿时间:2019-03-12  修订日期:2019-08-06  点此下载全文
引用本文:
DOI:10.19762/j.cnki.dizhixuebao.2020038
摘要点击次数: 21
全文下载次数: 22
作者单位E-mail
韩文文 核工业二八〇研究所 252908089@qq.com 
彭智敏 中国地质调查局成都地质调查中心 pzm20022002@163.com 
张辑 核工业二八〇研究所  
关俊雷 中国地质调查局成都地质调查中心  
胡金锋 核工业二八〇研究所  
刘云鹤 核工业二八〇研究所  
基金项目:中国地质调查局工作项目(DD20160016、DD2016013639)资助的成果
中文摘要:内容:澜沧岩群位于滇西“三江”地区的昌宁―孟连结合带,是研究特提斯造山带重要组成部分。本文对双江地区出露的钠长浅粒岩进行锆石U?Pb定年、Hf同位素及岩石地球化学分析,讨论了岩石的成因和形成时代,以及大地构造演化。利用LA?ICP?MS对钠长浅粒岩中具有典型岩浆震荡环带的锆石U?Pb定年,获得了206Pb/238U加权平均年龄为476.5±1.6Ma,形成时代为早奥陶世(O1)。Hf 同位素原位分析获得锆石εHf(t)值为?5.6~?2.2,TDMc年龄为1591~1802Ma,表面源区物质形成于早元古代晚期―中元古早期古老地壳物质的部分熔融。岩石地球化学分析,钠长浅粒岩的原岩为花岗闪长岩,具有高硅SiO2=(67.89~68.91)%、富铝Al2O3=(14.48~15.14)%、高钾钙碱性过铝质S型花岗岩特征;轻稀土富集,整体呈“右”倾型;δEu值介于0.60~0.64之间,呈现强Eu负异常,表明斜长石从岩浆中结晶分离。分析认为,钠长浅粒岩的原岩应特为昌宁?孟连特提斯洋在弧?陆碰撞阶段形成的岛弧花岗岩,与奥陶纪惠民岩组火山岩具有相同的大地构造背景;随着特提斯洋俯冲消减进入陆内挤压阶段,岛弧花岗岩呈俯冲增生杂岩拼贴到昌宁―孟连结合带与临沧花岗岩带之间,组成了澜沧岩群构造岩片。
中文关键词:滇西双江地区  澜沧岩群  锆石U?Pb年龄  Hf同位素  昌宁?孟连结合带  岛弧花岗岩  
 
U-Pb dating of zircon and Hf Isotope Composition and Tectonic Significance of the albite-granulite of the Lancang Group in the Shuangjiang area of western Yunnan,China
Author NameAffiliationE-mail
Han Wenwen Institute No.280CNNC 252908089@qq.com 
Pen Zhimin Chengdu Institute of Geology &
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Mineral ResourcesChina Geological Survey 
pzm20022002@163.com 
Zhang Ji Institute No.280CNNC  
Guan Junlei Chengdu Institute of Geology &
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Mineral ResourcesChina Geological Survey 
 
Hu Jingfeng Institute No.280CNNC  
Liu Yunhe Institute No.280CNNC  
Abstract:The Lancang group, an important part of the Tethys orogenic belt, is located in the Changning?Menglian combined belts in the Sanjiang area of western Yunnan, China. In this paper, we conducted zircon U?Pb dating, Hf isotope and petrogeochemistry of albite-granulite, whose discussed the genesis, forming Age and geotectonic evolution of the rocks in the Shuangjiang area. The detrital zircons with strongly oscillatory zoning is typically magmatic origin from albite-granulite, which were employed for dating. U?Pb dating is 476.5±1.6Ma about weighted average of 206Pb/238U, which is Early Ordovician (O1).In situ analysis of Hf isotopes, the εHf(t) is ?5.6~?2.2 and the TDMc Age is (1591~1802) Ma, indicating that the materials in the source area were formed by partial melting of ancient crustal materials during from the terminal of Early-Proterozoic to the early of Middle-Proterozoic . According to petrogeochemical analysis, the original rock of albite-granulite is granitic diorite which are peraluminous S-type granite with High SiO2= (67.89~68.91) %, Aluminum-rich Al2O3= (14.48~15.14) % and High potassium calc-alkaline. The characteristics, enrichment in LREE, tilted the overall "right", δEu(0.60~0.64)and strong negative Eu, indicated that plagioclase crystallization have separated from magma.The analysis shows that the original rock of albite-granulite is island-arc granite, which formed in the continent-arc collision stage about Changning?Menglian Tethys, has the same tectonic background as the volcanic rocks of the Huimin formation in the Ordovician. As Tethys entered intracontinental subduction?grinding stage, the island-arc granite is a subduction accretionary complex, between the Changning?Menglian combined belts and the Lincang Batholith, forming tectonic sheet of the Lancang group.
keywords:Shuangjiang area of western Yunnan  The Lancang group  U?Pb dating  Hf isotope  Changning?Menglian combined belts  The island-arc granite
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