河南省新县姚冲钼矿床成因机制研究

Study of formation mechanism from the Yaochong Mo deposit,Xinxian Country,Henan Province

在详细的野外地质工作基础上,通过含矿石英中的流体包裹体,矿石硫、铅同位素,含矿石英氢、氧同位素等研究,探讨姚冲钼矿床成矿物质来源和形成机制.显微观察表明流体包裹体可分为LH2O+VH2O两相水溶液包裹体(Ⅰ型)、LH2O+LCO2+VCO2三相水溶液包裹体(Ⅱ型)和含子矿物的LH2O+LCO2+VCO2+S四相水溶液包裹体(Ⅲ型)三种类型;流体包裹体均一温度介于190℃~384℃(含子晶介于322℃~513℃)之间,盐度介于1.62wt%~13.18wt%NaCl eq之间;流体包裹体激光拉曼组分分析显示:Ⅰ型包裹体主要为H2O并含有少量CO2,Ⅱ型和Ⅲ型包裹体主要为H2O和CO2;计算密度介于0.641~0.965g·cm-3之间,估算最大成矿深度约2km.矿石硫同位素δ34SV-CDT值介于-2.89‰^-0.30‰之间,均值为-1.78‰.矿石铅同位素206 Pb/204 Pb比值介于16.363~17.344之间,均值为16.757;207Pb/204Pb比值介于15.298~15.473之间,均值为15.368;208Pb/204Pb比值介于37.324~37.854之间,均值为37.539.含矿石英的δDSMOW值介于-79.80‰^-64.30‰之间,均值-70.20‰;δ18 OH2O值介于1.24‰~3.08‰之间,均值2.07‰.以上研究表明姚冲钼矿床形成于中高温浅成环境,成矿物质主要来源于下地壳溶融形成的岩浆,可能混有少量的地幔物质;成矿流体以岩浆水为主,混有大气降水,混合作用是矿床形成的主要机制.

Based on field geological investigation,we studied microthermometry and Micro-laser Raman microprobe compositions for fluid inclusions from the Yaochong Mo deposit,as well as sulfur and lead isotopic compositions for ores,hydrogen and oxygen isotopic compositions for ore-bearing quartz.This paper discusses that the ore-forming materials resource and formation mechanism for the Yaochong Mo deposit.The microscopic observation shows thatfluid inclusions are mainly consists of LH2O＋VH2Ofluid inclusions（typeⅠ）,LH2O＋LCO2＋VCO2fluid inclusions（typeⅡ）and LH2O＋LCO2＋VCO2＋S fluid inclusions（typeⅢ）.Microthermometry indicates that the homogenization temperatures range from 190 ℃to 384 ℃（daughter minerals-braring fluid inclusions range from 322 ℃ to 513 ℃）and their salinities range from 1.62 to 13.18wt% NaCl eq.Micro-laser Raman spectroscopy shows that the typeⅠfluid inclusions mainly consist H2 O and a small amount of CO2,type Ⅱ and type Ⅲ mainly contain H2 O and CO2.We conclude that fluid density varies from 0.641 to 0.965g·cm-3,and ore-forming depth is about 2km.Theδ34SV-CDT value of ores ranges from-2.89‰ to-0.30‰,with an average value of-1.78‰.206 Pb/204 Pb,207 Pb/204 Pb and208Pb/204 Pb ratios of ores range from 16.363 to 17.344,15.298 to 15.473 and 37.324 to 37.854,with the average value of 16.757,15.368 and 37.539,respectively.TheδDSMOW andδ18OH2Ovalues of the ore-bearing quartz are-79.80‰^-64.30‰（with an average value-70.20‰）,1.24‰ ~3.08‰（with an average value 2.07‰）,respectively.The synthetic analytical results indicate that the Yaochong Mo deposit is formed in superficial and middle-high temperature environment,ore-forming materials mainly came from the melting crust and may be contaminated by mantle substances.The ore-forming fluid mainly came from magmatic water and then was contaminated by meteoric water,which means the mixing effect is the main mechanism of ore deposit formation.