西藏山南努日铜钼钨矿床矽卡岩地球化学特征及成因  

Geochemical Characteristics and Origin of Skarn Rocks in the Nuri Cu-Mo-W Deposit,Southern Tibet

作　　者：陈雷[1,2] 秦克章[1] 李光明[1] 肖波[1,2] 李金祥[1] 江化寨 陈金标[3] 赵俊兴[1,2] 范新[1,2] 韩逢杰 黄树峰[3] 琚宜太[4] 

机构地区：[1]中国科学院地质与地球物理研究所矿产资源研究重点实验室,北京100029 [2]中国科学院研究生院,北京100039 [3]中国冶金地质总局第二地质勘查院,甫田351111 [4]中国冶金地质总局,北京100025

出　　处：《地质与勘探》2011年第1期78-88,共11页Geology and Exploration

基　　金：国家自然科学基金(编号:40772066);中国冶金地质总局"冈底斯东段南部矽卡岩-斑岩Cu-Au-Mo矿床成矿模式及成矿条件综合研究"项目联合资助

摘　　要：西藏山南地区努日Cu-W-Mo多金属矿床位于冈底斯火山-岩浆弧构造带东段南缘,属于冈底斯铜钼成矿带的南亚带,是新近探明的一个大型矽卡岩型的铜钨钼矿床,也是西藏冈底斯带首例钨矿床。对矿区内出露的矽卡岩、大理岩和灰岩的地球化学组成研究表明:在主量元素方面,Ca、Ti、Al、Mg、Mn、Fe及Si等元素在灰岩、大理岩和矽卡岩中发生了迁入迁出,各元素含量在三者之间呈线性变化;稀土元素方面,矽卡岩具有明显的LREE富集,HREE亏损特征,发育有较明显的Eu负异常;大理岩具有与矽卡岩相似的REE配分模式,说明两者在成因上具有一定联系。由矽卡岩中不同的稳定矿物组合及稀土配分模式中的Eu负异常,推测其形成于一种弱氧化、中高温的环境,这也与流体包裹体研究结果相一致。同时根据矿区内矽卡岩几乎不发育Ce的异常,说明形成矽卡岩的流体中没有海水的混合,主要来源于深部的岩浆,混染了大量的大气水。结合矿区内不同岩性的地球化学特征,强烈的轻、重稀土分异,明显的负Eu异常,且矿区内的矽卡岩与热水喷流系统具有显著差异,推测努日矿床是由岩浆热液流体的接触交代作用形成。The Nuri Cu-W-Mo deposit is a newly explored and proved large-scale deposit in southern Tibet.It lies in the southern margin of the eastern Gangdese volcanic-magma arc,and belongs to the southern subzone of the Gangdese Cu-Mo metallogenic belt.We chose the skarn,marble and limestone exposed in the ore district to conduct component analysis.The results show that the major elements（Ca,Ti,Al,Mg,Fe and Si）are transferring among marble,limestone and skarn rocks,and the content of the elements between these rocks exhibits a linear change.The skarn rocks are rich in LREE and deficit in HREE,and bear intense Eu negative anomalies.The marbles have the same REE distribution patterns as the skarn,so we conclude they may have some relation in petrogenesis.Based on the mineral assemblage and Eu negative anomalies in the REE distribution patterns,we infer the skarn rocks were formed in a weak oxidation,medium-high temperature environment,which is consistent with the conclusion from the study on fluid inclusions.Besides,the scarcely developed Ce anomalies in skarn rocks suggest that the fluids for skarn forming were mainly derived from magma,and mixed with a lot of meteoric water.Combined with the geochemical characteristics of different rocks,intense differentiation of LREE and HREE,Eu negative anomalies,and the fact that skarn rocks are different from the hydrothermal exhalative mineralization system,we infer that the Nuri deposit was formed by fluid metasomatism.

关 键 词：地球化学 Eu、Ce异常 接触交代 矽卡岩 努日 西藏 

分 类 号：P618.51[天文地球—矿床学]