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周淑敏,王庆飞,李龚健. 2018. 滇西腾冲地块梁河晚三叠世正长花岗岩地球化学、锆石U-Pb年代学及其地质意义. 岩石学报, 34(5): 1359-1375
滇西腾冲地块梁河晚三叠世正长花岗岩地球化学、锆石U-Pb年代学及其地质意义
作者单位E-mail
周淑敏 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083
青海大学地质工程系, 西宁 810016 
 
王庆飞 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083 wqf@cugb.edu.cn 
李龚健 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083  
基金项目:本文受国家重点基础研究发展计划"973"项目(2015CB452606)和国家重点研发计划(2016YFC0600307)联合资助.
摘要:
      本文对出露腾冲地块梁河正长花岗岩进行了全岩元素地球化学、锆石U-Pb年代学和Hf同位素组成研究,旨在揭示正长花岗岩的侵位年龄、成因类型、源区性质及其构造环境。锆石U-Pb LA-ICP-MS定年表明,正长花岗岩形成年龄为~218Ma,表明该花岗岩体形成时代属于晚三叠世。地球化学特征研究表明,正长花岗岩具有高硅(SiO2=70.28%~74.49%)、富碱(K2O+Na2O=6.81%~8.71%)、过铝质(A/CNK=1.00~1.12)、高钾钙碱性特征。微量元素显示岩体富集轻稀土元素,大离子亲石元素(K、Rb),亏损高场强元素(Nb、Ta、P、Ti、Ba、Sr、Eu)。大部分样品轻重稀土强烈分异(LREE/HREE=6.07~13.8)。综合样品的地球化学数据及矿物组合特征,判断该岩体为S型花岗岩,源区岩石主要为砂屑岩。锆石εHft)值(-10.74~-4.14),二阶段模式年龄(tDMC)为1.5~1.9Ga,表明其源于古老地壳熔融。岩石具有相对低的锆饱和温度,平均为~655℃,说明其没有幔源岩浆的加入。本文研究结果表明,梁河晚三叠世正长花岗岩可能形成于后碰撞伸展背景下的古老地壳熔融。
英文摘要:
      This paper conducts the research about the bulk geochemistry, zircon U-Pb chronology and Hf isotopic compositions on syenogranite in the Tengchong block of the Lianghe area. This paper aims to reveal the emplacement age, petrogenetic type, nature of source rocks and tectonic environment. Zircon U-Pb LA-ICP-MS dating shows that the formation age of syenogranite is ~218Ma. This indicates that syenogranite's formation age belongs to the Late Triassic. Geochemical characteristics indicate that syenogranite has characteristics of high silicon (SiO2=70.28%~74.49%), rich alkali (K2O+Na2O=6.81%~8.71%) belonging to prealuminous (A/CNK=1.00~1.12) and high kalium calc alkaline. Trace elements show that rock mass is enriched in light rare earth elements (LREES), large ion lithophile elements (LILES) (K, Rb), and depleted of high field strength elements (HFSEs) (Nb, Ta, P, Ti, Ba, Sr and Eu). Most of the light rare earth element were powerfully differentiated (LREE/HREE=6.07~13.8). Therefore, all the characteristics recognize that the rock mass belongs to S-type granite, and rocks in this source region mainly are clastic rock. The value of zircon εHf(t) is (-10.74~-4.14), The second stage Hf model age (tDMC)range from 1.5Ga to 1.9Ga. These data indicate that Triassic syenogranites derived from the ancient crust melting. Rock has relatively low zirconium saturation temperature, average ~655℃. It shows that no mantle-derived magma is added. The results indicate that Late Triassic syenogranites from Lianghe probably formed by the melting of ancient crustal materials in extensional setting of post-collision.
关键词:正长花岗岩  地球化学  锆石U-Pb年代学  锆石Hf同位素  梁河  滇西
投稿时间:2017-12-20  修订日期:2018-03-28
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