甘肃厂坝铅锌矿床黄铁矿流体包裹体 He-Ar 同位素体系

摘要

稀有气体是一种研究成矿古流体来源的灵敏示踪剂，其同位素组成对揭示成矿流体来源、成因和演化等信息意义重大。甘肃厂坝铅锌矿成矿流体来源方面的研究至今仍存争议，本研究通过对该矿床黄铁矿流体包裹体 He-Ar 同位素组成特征的分析，结合研究区具体的矿床地质背景，对其成矿流体来源进行了探讨。主要结果表明：3He/4He 值为0.0137~0.0758 Ra，说明成矿流体具有壳源特征；40Ar/36Ar 值的平均比值为438.78，高于大气饱和水的 Ar 同位素特征值（40Ar/36Ar=295.5），说明成流体中有壳源放射性成因的40Ar 加入；成矿流体中相对低的40Ar*（%）值和40Ar*/4He 比值，表明大气饱和水曾参与了成矿作用，且有部分成矿流体捕获了围岩中高放射成因的4He。上述结果从稀有气体同位素角度为厂坝铅锌矿成矿流体来源提供了证据，说明厂坝铅锌矿成矿流体是泥盆纪喷流沉积作用和印支—燕山早期构造改造成矿作用的综合产物。%The research about the Changba lead-zinc deposit has owned a wide concerns,especially in the undetermined sources of ore-forming fluids.The study mainly discussed the sources of ore-forming fluids according to analyze helium and argon isotopes compositions of fluid inclusions in pyrite from the Changba lead-zinc deposits.The results show that 3He/4He ratios are range from 0.0137 to 0.0758 Ra,which indicates that the ore-forming fluids were crust-derived fluids.The average of 40Ar/36Ar ratios is 438.78,which is higher than that of the air saturated water(295.5),indicated that radiogenic Ar in crust joined in ore-forming fluids.The low ratios of 40Ar*(%)and 40Ar*/4He showed that the air saturated water involved in the ore-forming process,and part of ore-f luids captured higher radiogenic 4He in surrounding rock.It is concluded that the ore-forming fluids of Changba lead-zinc deposit is formed by a comprehensive action of sedmentary-exhalative metallization in Devonian and tectonic alteration Indo-early Yanshan.