西秦岭地区猪婆沟金矿成矿物质来源及矿床成因分析

Source of ore Forming Materials and Genesis of Zhupogou Gold Deposit in West Qinling Mountains

猪婆沟金矿位于西秦岭之北秦岭鸳鸯镇-关子镇蛇绿混杂岩带的反“S”形构造的转折端,金矿体赋存在早古生代李子园群中,矿体的产出受NW向和NE向韧性断裂及其次级构造控制,矿体形态为脉状。矿床热液期主成矿阶段石英中包裹体主要为气液两相包裹体、含子晶三相包裹体。含子晶三相包裹体的冰点温度为-4.8~-4.3℃;气液两相包裹体的冰点温度为-5.3~-0.1℃。该阶段含子晶三相包裹体的均一温度为141.3~198.6℃,平均为160.7℃;气液两相包裹体的均一温度为128.9~285.3℃,平均为174.1℃。成矿流体的均一温度值为130~170℃,峰值范围较宽。流体盐度为1.40~8.28%NaCleqv,平均为5.84%NaCleqv,具有中低温、低盐度特征;石英δ18OH2O值为-3.29‰~4.42‰,δD值为-110.1‰~-86.6‰,成矿流体来源于原生岩浆水,在岩浆分异成矿的过程中,大气降水的含量逐渐增多。主成矿阶段黄铁矿和毒砂δ34S值为10.7‰~11.5‰,矿物质分别来源于岩浆岩和地层;Pb同位素组成相似,主要来源于造山带铅,有部分上地壳铅和地幔铅加入,成矿物质来源于岩浆岩和地层两个端元,具有多期次特征。综合分析认为,猪婆沟金矿成因类型属沉积变质-岩浆期后热液叠加改造的构造蚀变岩型金矿床。

Zhupogou gold deposit is located at the turning end of the anti"s"shaped structure of the Yuanyang town Guanzi town Ophiolitic Melange belt in the north of the West Qinling Mountains.The gold deposit is hosted in the early Paleozoic Liziyuan group.The occurrence of the ore body is controlled by NW and NE trending ductile faults and their secondary structures,and the shape of the ore body is vein.The inclusions in quartz in the main metallogenic stage of the hydrothermal period of the deposit are mainly gas-liquid two-phase inclusions and three-phase inclusions containing daughter crystals.The freezing point temperature range of three-phase in-clusions containing daughter crystals is−4.8~−4.3℃;The freezing point temperature of gas-liquid two-phase inclusions ranges from−5.3 to−0.1℃.At this stage,the homogenization temperature of three-phase inclusions containing daughter crystals is in the range of 141.3~198.6℃,with an average of 160.7℃;The gas-liquid two-phase inclusions are in the range of 128.9~285.3℃,with an average of 174.1℃.The homogenization temper-ature of ore-forming fluid is 130~170℃,and the peak range is wide.Fluid salinity is 1.40%~8.28%Nacleqv,average 5.84%NaCleqv.It has the characteristics of medium low temperature and low salinity;quartzδ18OH2O is−3.29‰~4.42‰,δD is−110.1‰~−86.6‰,and the ore-forming fluid comes from primary magma water.In the process of magmatic differentiation and mineralization,the content of atmospheric precipitation gradually in-creases.Pyrite and arsenopyrite in the main metallogenic stageδ34S value is 10.7‰~11.5‰,and the minerals are derived from magmatic rocks and strata respectively;Pb isotopic composition is similar,mainly from the orogenic belt,with some upper crust lead and mantle lead added.The metallogenic material comes from the two end elements of magmatic rock and stratum.Comprehensive analysis shows that the genetic type of Zhupogou gold deposit belongs to the tectonic altered rock type gold deposit of sedimentary metamorphism post magmatic hydrothermal superimposition.