豫西大石门沟钼矿床成矿物质来源、流体包裹体特征及成矿机制

Sourceses of Ore,Features of Fluid Inclusions and Ore-forming Mechanism of the Dashimengou Molybdenum Deposit in Western Henan

豫西大石门沟钼矿床位于熊耳山东南麓,属典型隐爆角砾岩型斑岩矿床。成矿过程经历了早、中、晚阶段。成矿热液δ18O介于-2.12‰~5.23‰,δDV-SWOW介于-94.5‰^-65.7‰,流体主要来自岩浆。δ34S值-17.3‰^-0.74‰,硫源主要来自深部,混有壳源硫。δ13C在-5.3‰^-5.6‰,属岩浆来源碳同位素组成。矿床金属硫化物的206Pb/204Pb值在17.161~17.387之间,平均值17.242;207Pb/204Pb值在15.433~15.452之间,平均值15.444;208Pb/204Pb在37.420~37.508之间,平均值38.454,暗示铅主要来自深部。钼矿石∑REE为292.53×10-6~432.94×10-6,LREE/HREE值3.84~7.76,δEu值0.54~0.73,中等负铕异常,δCe为0.83~0.89,呈弱负铈异常,矿化蚀变岩与花岗岩具有一定的相似性。早阶段为LCO2型及LCO2+S型、少量VCO2型流体包裹体;中阶段流体包裹体有V-L型、V-L+S型包裹体;而晚阶段发育气液V-L型包裹体。三个阶段流体包裹体均一温度分别集中在(247~468)℃、(111~372)℃、(110~272)℃;盐度分别对应于11.64,6.75,6.12 wt%NaCl.eqv,随均一温度的降低而降低。钼矿床属隐爆角砾岩型斑岩钼矿床,马超营断裂的俯冲和地壳增厚,拆沉作用导致幔、壳岩浆上涌侵位,在印支期主要成矿阶段第一次隐爆,形成钼矿床的大概轮廓。在构造体制转换燕山早期再次隐爆,继承、叠加和改造印支期成矿,是临近燕山期岩浆岩和斑岩侵入在大石门沟钼矿的一种响应,两者组成了该区中生代成矿作用的完整旋回,构成秦岭钼(钨)、金、银、铅锌等金属矿带的一个晋宁、加里东、印支和燕山期的完整成矿系列。

DaShimengou molybdenum deposit in western of Henan is located in the southeast of Xiong＇er mountain,which is a typical breccia-type porphyry deposits.Mineralization process has gone through the early,middle and late stages.The δ^18 O of Ore-forming hydrothermal between-2.12‰ and 5.234‰,the δDv-swow between -94.50‰ and-65.7‰,and fluids mainly come from magmatic fluids.The value of δ^34S is between-17.3‰ and 0.74‰,the source of sulfur is mainly from the deep,and mixed with crustal sulfur.The δ^13C is at-5.3‰ to -5.6‰,belongs to carbon isotopic composition of magmatic origin.The ^206pb/^204pb of metal sulfide deposits is in 17.161 ～ 17.387 and mean is 17.242 ;^207 pb/^204pb is between 15.433 and 15.452,averaging 15.444 ;^20spb/^204pb is at 37.420 ～ 37.508,averaging 33.454,suggesting lead primarily comes from the deep.ΣREE of Molybdenum ore is 292.53 × 10^-6 ～432.94 × 10^-6,LREE/HREE is 3.84 ～ 7.76,δEu is 0.54 to 0.73,shows moderate to negative Eu anomaly,δCe is 0.83 to 0.89,shows weakly negative anomaly,mineralized altered rocks and granite have certain similarities.The early stage of Mineralization process is LCO2-type and LCO2 ＋ S-type、small VCO2 type fluid inclusions;fluid inclusions in phase have V-L-type and V-L ＋ S-type;but the late stage developments gas-liquid inclusions of VL-type.Homogenization The temperatures of fluid inclusions at the three stages are concentrated in the （247 ～ 468） ℃,（111 ～ 372） ℃,（110 ～ 272） ℃ ; salinity respectively correspond 11.64、6.75 and 6.12% wt% NaC1.eqv,decreases with uniform temperature decreases.Molybdenum deposit is a breccia-type porphyry molybdenum deposit,Machaoying fracture subduction and crustal thickening,delamination causes mantie、crust upwelling emplacement,the first hidden explisive in the main mineralization stage Indosinian forms an approximate ouline of molybdenum deposit.Molybdenum deposit in the main mineralization stage cryptoexplosions agin when the tectonic regine transfer into the early YanShan,inheritance,overlay and reforming Indosinian＇ s mineralization is a response of close to Yanshanian magmatic rocks and porphyry intrusive molybdenum deposit of the Dashimengou and both of them form a complete cycle of mineralization in Mesozolic and constitute a complete metallogenic series of the Qinling molybdenum,gold,silver,lead,zinc and other metal ore belt in Jinningian,Caledonian,Indosinian and Yanshanian.