滇西北羊拉矿区基性岩地球化学特征及构造意义  

Geochemical Characteristics and Tectonic Significance of Basic Rocks in the Yangla Ore District,Northwestern Yunnan Province

作　　者：朱俊[1] 李文昌 曾普胜[3,4] 尹光候 王彦斌[5] 王勇[6] 余海军 董涛 邓云清 罗诚 

机构地区：[1]昆明理工大学,昆明650093 [2]云南省地质调查局,昆明650051 [3]中国冶金地质总局矿产资源研究院,北京100025 [4]云南财经大学,昆明650221 [5]中国地质科学院地质研究所,北京100037 [6]东华理工大学,抚州344000 [7]云南迪庆矿业开发有限责任公司,香格里拉674400

出　　处：《地质与勘探》2010年第5期899-909,共11页Geology and Exploration

基　　金：国家科技支撑计划项目(编号:2006BAB01A07)资助

摘　　要：对滇西北金沙江带羊拉矿区的基性岩进行了系统的主量元素和微量元素研究,同时对比白茫雪山-拱卡路线上与蛇绿岩共生的玄武熔岩的地球化学性质,探讨羊拉矿区基性岩形成的地质构造背景。研究表明,矿区下石炭统贝吾组玄武岩与白茫雪山-拱卡玄武岩地球化学性质相似,具洋脊之特征,低K,Ti,轻重稀土元素分馏不明显,微量元素特征指示二者可能来自于较富集的源区,均为金沙江洋盆扩张的产物,属于缝合带的组成部分。矿区泥盆系地层内的辉绿岩脉斜交侵入围岩,晚于火山岩和洋盆沉积物的形成,辉绿岩脉稀土元素标准化曲线右倾,强不相容元素富集,Ta、Nb亏损,具大陆边缘岛弧性质,微量元素特征与大洋玄武岩和洋内岛弧玄武岩亦存在一定差异,推测辉绿岩脉可能形成于三叠纪金沙江带陆缘岛弧岩浆活动阶段,对于有的学者确定该区为洋内岛弧构造环境的认识在本次工作中没有得到验证。In order to study the tectonic settings of the Yangla ore district in the Jinshajiang zone,western Yunnan province,this work made a systematic geochemical analysis of major elements and trace elements for basic rocks from this ore district,and compared them with the geochemical properties of basalt lava coexisting with ophiolite in the route from the Baimang snow Mountains to Gongka.The result shows that the geochemical characteristics of basalt from Beiwu Formation in Lower Carboniferous of the Yangla ore district are similar to those from ophiolite units of the Baimang snow Mountains and Gongka,both being analogous to mid-ridge basalt,characterized by low K and Ti,and not obvious in fractionation between LREE and HREE.The trace elements indicate that they might originate from an enriched source,as the result of spreading of the ancient Jinshajiang ocean floor and presented as a part of the suture zone.The diabase dyke in the Yangla orefield,which intruded into the Devonian stratum,shows its epigenetic features.The normalized REE patterns of diabase are apparently inclined to right.The trace elements show enrichment in highly incompatible elements and depleted in Nb and Ta.These characteristics are similar to those of volcanic rocks in the epicontinental arc and different from basalt in ocean islands or intra-oceanic arcs.We infer that the diabase dyke were likely produced the Triassic magmatic activity of the epicontinental arc.This study does not support the previous conclusion that the Yangla district is situated in a tectonic setting of intra-ocean arcs.

关 键 词：羊拉矿区 基性岩 地球化学 构造环境 

分 类 号：P595[天文地球—地球化学]