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西藏西部地区埃达克质侵入岩及铜金找矿意义
引用本文:蔡志勇,邱瑞照,熊小林,黄圭成,周肃,孟祥金.西藏西部地区埃达克质侵入岩及铜金找矿意义[J].大地构造与成矿学,2005,29(4):491-501.
作者姓名:蔡志勇  邱瑞照  熊小林  黄圭成  周肃  孟祥金
作者单位:1. 中国科学院广州地球化学研究所,广东,广州,510640;中国科学院研究生院,北京,100039;鄂西北地质矿产调查所,湖北,襄樊,441003
2. 宜昌地质矿产研究所,湖北,宜昌,443003
3. 中国科学院广州地球化学研究所,广东,广州,510640
基金项目:中国地质调查局资助项目,中国科学院知识创新工程项目
摘    要:本文报道的西藏西部地区中酸性侵入岩,其形成时代为11.8~25Ma,滞后于洋壳俯冲作用,具有高Si02(56.00%~70.62%)、Al2O3(14.23%~16.85%)、K2O(1.74%~4.33%)、Na2O(一般Na2O/K2O>1)、Sr(420~938μg/g),贫Y(7.16~16.0μg/g),低MgO和CaO,富集LILE元素及LREE,亏损HREE等特征,表现出与埃达克岩相似的地球化学特征。结合其形成时代和地质背景分析,其成因与俯冲洋壳熔融无关,而与藏北埃达克质火山岩及中国东部C型埃达克岩成因相似,符合加厚地壳熔融模型。文中指出西藏西部地区埃达克岩的厘定具有重要的地球动力学意义和铜金矿找矿意义。

关 键 词:西藏西部  埃达克岩  地球化学  成因  找矿意义
文章编号:1001-1552(2005)04-0491-11
收稿时间:2004-12-16
修稿时间:2005-03-28

THE ADAKITE- LIKE INTRUSIVE ROCKS CHARACTERISTICS OF WESTERN TIBET AND THEIR PROSPECTING SIGNIFICANCE
CAI Zhiyong,QIU Ruizhao,XIONG Xiaolin,HUANG Guicheng,ZHOU Su,MENG Xiangjin.THE ADAKITE- LIKE INTRUSIVE ROCKS CHARACTERISTICS OF WESTERN TIBET AND THEIR PROSPECTING SIGNIFICANCE[J].Geotectonica et Metallogenia,2005,29(4):491-501.
Authors:CAI Zhiyong  QIU Ruizhao  XIONG Xiaolin  HUANG Guicheng  ZHOU Su  MENG Xiangjin
Institution:1. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, GD 510640, China ; 2. Graduate School, Chinese Academy of Sciences, Beijing 100039, China; 3. Northwestern Hubei Survey of Geology and Mineral Resources, Xiangfan, HB 441003, China ; 4. Yichang Institute of Geology and Mineral Resources Research, Yichang , HB 443003, China
Abstract:The ages of intrusive rocks of western Tibet that occurred in the southern and middle Gangdese plutons with NW trends (between 88° longitudes and the western borders of China) are less than 25 Ma generally. Samples that were collected from the plutons, belonging to the series of continental alkaline magmatism, show the characteristics as follows: relatively high SiO2 (56.00%~70.6%), A12O3 ( 14.23%~ 16.85 %), K2O ( 1.74%~ 4.33%) and Na2O (Na2O/K2O>1, generally), high Sr (420~938 μg/g), low Y (7.16~16.0 μg/g). They show a REE pattern rich in light REE and abnormality in Eu (weak) and Sr (positive) compared to the standardized pattern. These geochemical characteristics are typical of adakite. In considering the geological setting and isotopic ages of the samples as less than 25 Ma and the crustal thickness of the Tibetan plateau as about 60 km at that time based on petrologic evidence, and by comparing with the characteristics of adakite-like rocks reported in the eastern Tibet and eastern China, it is suggested that the subducted oceanic crust slab was not involved in generating adakite magmas which formed these rocks. So they probably belong to C-type adakites, which were derived from continued magmatic underplating and thickening at the base of the crust. It is well-known that copper and gold deposits are closely related to adakite in China and abroad. Also it is reported that the occurrences of many copper deposits in and around the cotemporaneous adakite or adakite-like rocks in the eastern part of the Qinghai-Tibetan Plateau. Therefore, the discovery of the Cenozoic adakites in this paper have geological significance in dynamics showing continental plumb growth in Cenozoic, especially, in ore-prospecting of porphyry copper and gold deposits showing brilliant prospect potential in the western part of the Qinghai-Tibetan Plateau.
Keywords:West Tibet  adakite  characteristics  origin  prospecting significance
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