南秦岭山柞地区晚侏罗世-早白垩世斑岩-矽卡岩型铜（钼）矿床深部地质过程与成矿作用研究

Compared with the Mesozoic porphyry Mo deposits in Qinling Orogenic Belt, the Late Jurassic-Early Cretaceous porphyry-skarn Cu(Mo) deposits have unique Cu mineralization feature in Shan-Zha area, South Qinling. However, the metallogenic magmatism, mineralization mechanism and deep geological processes of the deposits are lack of systematic research, which seriously restrict the research of why Qinling Orogenic Belt lacks of porphyry Cu deposit. So in order to provide a comprehensive recognition on these issues, we choose Xiaohekou skarn Cu deposit and Lengshuigou porphyry-skarn Cu(Mo) deposit as research objects. Based on systematic field geological observation, we will conduct detailed microstructure observations on various minerals, and use the EPMA text the major elements and volatile components of magmatic and altered minerals, analyze the trace elements and Sr, Nd, S isotopes of magma apatite, hydrothermal apatite, plagioclase and sulfide via LA-(MC)-ICP-MS. We also plan use LA-ICP-MS text the components of fluid inclusion. Combining with whole-rock geochemistry and ore-forming fluid, we will debate the source and evolution of metallogenic magma, and discuss the variation of fO2, volatiles and ore-forming fluid during the ore-forming processes and their controlling factors for the migration and precipitation of metallogenic elements. Based on these results, we detailedly describe the influence of deep geological process for the porphyry-skarn Cu(Mo) mineralization, and bulid the metallogenic model of those deposits. Moreover, the research also provide theoretical basis for further exploration in Qinling Orogenic Belt.

南秦岭山柞地区晚侏罗世-早白垩世斑岩-矽卡岩型铜（钼）矿床以独特的铜矿化而不同于秦岭造山带中生代斑岩型钼矿化，但成矿岩浆、成矿机制与深部地质过程始终缺乏深入研究，严重制约了秦岭造山带缺乏斑岩型铜矿缘由的研究。因此，本申请以冷水沟和小河口斑岩-矽卡岩型铜（钼）矿床为研究对象，基于详实的野外地质和室内显微结构观察，利用EPMA对不同产状的岩浆矿物和热液蚀变矿物进行主量元素和挥发分测试，利用LA-(MC)-ICP-MS对岩浆和热液磷灰石、斜长石及硫化物等开展原位微量元素和Sr、Nd、S同位素研究，对流体包裹体进行原位成分分析，辅以全岩地球化学和成矿流体研究，揭示成矿岩浆的源区和深部演化过程，精细刻画氧逸度、挥发分及成矿流体在成矿过程中的变化及对成矿元素迁移、沉淀的控制作用，探讨岩浆深部地质过程对浅部斑岩-矽卡岩型铜（钼）成矿作用的影响，建立成矿模型，为区域矿产勘查提供理论依据。

通过对山柞地区晚中生代成矿岩体和非成矿岩体的岩石学、矿物（磷灰石、锆石和斜长石）微区成分及原位Sr同位素研究，显示两者均起源新元古代新生下地壳的部分熔融，但成矿岩体中有地幔物质的加入，并且地幔物质为成矿作用提供了挥发份、水及成矿物质，并增强了成矿岩浆系统的氧逸度。因此，认为陆内斑岩成矿系统中岩浆源区加入的地幔物质对成矿具有至关重要的作用。山柞地区早白垩世闪长质脉岩的研究显示其起源于新元古代增厚下地壳的部分熔融，形成于早白垩世构造体制由挤压向伸展转变环境，而这种构造体制的转变为区域内斑岩型铜（钼）矿床的形成提供了有利的构造环境。山柞地区晚三叠世杨木沟斑岩钼矿成矿岩体和英安岩的研究，显示南秦岭晚三叠世斑岩型钼矿形成于扬子板块与华北板块碰撞后伸展阶段，晚三叠世含矿岩体起源于中-新元古代新生地壳的熔融。综合对比南秦岭晚三叠世斑岩钼矿和晚侏罗世-早白垩世矽卡岩-斑岩型铜（钼）矿成矿岩体特征，南秦岭中-新元古代具有弧特征的新生地壳对中生代铜、钼成矿作用具有重要意义。对山柞地区晚中生代池沟斑岩铜矿的蚀变和矿化脉系特征进行系统总结，划分出四种流体包裹体类型：气液两相水成包裹体、含子晶矿物的多相包裹体、富CO2包裹体和单相包裹体，均一温度在125-575oC之间，盐度在3-64wt%NaCl之间，流体演化过程发生了相分离，石英氢氧同位素和次生磷灰石、绿帘石的原位Sr同位素显示成矿流体由岩浆流体主编转变为岩浆流体+大气降水。原位硫同位素显示成矿物质为岩浆起源。冷水沟矿区斑岩-矽卡岩型铜钼矿体和构造蚀变岩型金矿体精细的年代学研究显示铜钼矿化和金矿化均形成于~144Ma，结合构造蚀变与成矿流体特征，说明铜钼矿体和金矿体是同一成矿作用的产物，与区域内晚侏罗世-早白垩世岩浆岩具有密切的成因联系，表明南秦岭地区存在晚侏罗世-早白垩世金矿成矿作用，对区域铜钼金矿勘查工作具有重要指示意义。