川陕交界地区刘家坪花岗岩年代学、地球化学特征及构造意义  

Geochronological and Geochemical Study on Liujiaping Granite in the Border Area between Sichuan and Shaanxi Province and Its Tectonic Significance

作　　者：胡安新[1] 孙丰月[1] 王英德[1] 刘金龙[1] 张亮[1] 李良[1] 

机构地区：[1]吉林大学地球科学学院,吉林长春130061

出　　处：《西北地质》2014年第2期30-40,共11页Northwestern Geology

基　　金：陕西盛安矿业开发有限公司陕西省宁强县鸡头山-小燕子沟金矿床矿化富集规律及成矿预测研究(2013220101000019)

摘　　要：对川陕交界地区刘家坪花岗岩岩体进行了系统的锆石U-Pb年代学和地球化学研究,重点讨论了岩体的成因及其构造意义。测试结果显示,刘家坪花岗岩加权平均年龄值为825.9±7.8Ma,属新元古代中期;岩石低K富Na,显示硅过饱和,w（SiO2）%平均为75.32,并伴有过Al质特征;稀土元素丰度较低,∑REE为（182.13～243.76）×10-6,平均为197.29×10-6,显示LREE富集、HREE相对亏损的特征,稀土元素球粒陨石配分模式图表现为右倾＂海鸥＂型,并且具有明显的Eu负异常（δEu平均为0.57）;微量元素中Nb/Ta、Rb/Sr的结果及Mg#值综合显示岩浆来源主要为下地壳物质的部分熔融。岩石具有A型花岗岩特征,形成于碰撞期后的伸展构造背景,据此推测碧口地块与扬子地块在825Ma之前曾发生碰撞造山作用。两者的拼合模式为从北东到南西的剪刀式拼合。The Liujiaping granite intrusion is located in Sichuan-Shaanxi border area.The study of the zircon U-Pb geochronology and the geochemistry of the granite aim at discussing its formation and tectonic significance.The results show that the crystallization age of the granite is825.9±7.8Ma,which belongs to the mid-Neoproterozoic.The geochemistry analysis shows that the intrusion is low in potassium and rich in sodium and silica（with the average SiO2being 75.32%）,with peraluminous characteristics.The abundance of the∑REE varies in the range of（182.13-243.76）×10-6,with 197.29×10-6 on average,which shows an enrichment of the LREE and a depletion of the HREE.Chondrite-normalized REE patterns are of the right sea-gull oblique type with theδEu being 0.57,showing a significant negative Eu anomaly.The results of the Nb/Ta,Rb/Sr and Mg#show that the magmatic rocks of this region originated from the partial melting of the lower crust.With the characteristics of A type granites,the rock formed in the post-collision extensional tectonic setting,which indicates a collision had occurred between the Eastern Bikou terrane and the Yangtze block before 825Ma.The jointing mode of the two blocks is scissors joint from northeast to southwest.

关 键 词：川陕交界 地球化学 新元古代 A型花岗岩 剪刀式拼合 

分 类 号：P595[天文地球—地球化学]