新疆东准噶尔贝勒库都克锡矿床成矿时代及成矿作用  

Ore-forming Age and Ore-formation of the Beilekuduke tin deposit in East Junggar,Xinjiang

作　　者：杨富全[1] 毛景文[1] 闫升好[1] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037

出　　处：《地质论评》2008年第5期626-640,共15页Geological Review

基　　金：国家重点基础研究发展计划项目(编号2007CB411302);国土资源大调查项目(编号1212010561506);国家自然科学基金(编号40672065)的成果。

摘　　要：贝勒库都克锡矿床赋存于正长花岗岩中,矿化类型主要为蚀变花岗岩型、云英岩型和石英脉型。对云英岩型锡矿石中的白云母进行了^(40)Ar-^(39)Ar年龄测定,获得坪年龄为306.8±2.4 Ma～309.7±2.4 Ma,与正长花岗岩306±5 Ma在误差范围内一致。这组坪年龄不仅精确地反应出成矿的时间限制,而且表明了正长花岗岩与锡成矿的密切关系。锡矿石中石英流体包裹体划分为NaCl—H_2O型和NaCl—H_2O—CO_2—CH_4型。成矿温度主要集中在160～250℃和280～390℃,峰值在210℃和330℃,流体盐度为1.22%～7.86% NaCl_(eq),流体密度为0.55～0.96g/cm^3。锡矿石中石英的δD_(SMOW)介于—128‰～—95‰,δ^(18)O_(SMOW)值介于9.6‰～14.1‰,δ^(18)O_H_2_O值为1.56～8.09‰,表明成矿流体主要为岩浆水,混合少量大气降水。物理化学条件改变、水—岩交换作用及CO_2—CH_4和NaCl—H_2O的不混溶作用在锡成矿过程中起着重要作用。The Beilekuduke tin deposit occurs in syenogranite. According to mineral association and their occurrence, type of mineralization can be classified into three types： （1） altered granite type; （2） greisen type; and （3） quartz vein type. 40 Ar/30 Ar dating was performed on muscovite from greisen-type tin ore, which yielded two plateau ages of 306.8 ＋ 2.4 Ma and 309. 7 ＋ 2.4 Ma. Two plateau ages are coincident with the age of （306 ＋ 5） Ma from Beilekuduke syenogranite pluton in error range. These plateau age data not only accurately reflect the timing of ore formation but also indicate the close relation between syenogranite and tin ore. Two types of fluid inclusions, namely NaCl-H2O and NaCl-H2O-CO2-CH4 types, have been recognized in quartz from tin ore. Homogenization temperatures of fluid inclusions in tin ore-forming stage mainly vary from 160 to 250 ℃and 280 to 390 ℃, with two peaks temperature of 210 ℃ and 330 ℃. Salinity ranges from 1. 22% to 7.86% NaCl eq. Ore fluid densities range from 0.55 to 0.96g/cm^3. The δ^18OSMOW values of quartz from ore range from 9. 6‰ to 14. 1‰, with corresponding δ^18OH2O values of 1. 56‰ to 8. 09‰, and 8D values of fluid inclusions of between -128‰ and -95‰. The combined isotopic data imply that the ore-forming fluids of the Beilekuduke tin deposit were mainly derived from magmatic fluids, with some minor contributions from meteoric water. Changes in physieo-ehemical conditions and water - rock exchange and immiscibility of CO2-CH, and NaCl-H2O in hydrothermal fluids are inferred to have played important roles in the ore-forming process of the Beilekuduke tin deposit.

关 键 词：AR-AR年龄 流体包裹体 稳定同位素 锡矿床 贝勒库都克 新疆 

分 类 号：P618.44[天文地球—矿床学]