豫西庙岭金矿地质特征及成矿作用研究

发布时间：2018-07-05 19:30

  本文选题：岩石地球化学 + 流体包裹体　； 参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：豫西庙岭金矿床位于熊耳山金多金属矿集区,是一构造蚀变岩型金矿床。该金矿床赋存于近南北向断裂中,矿化类型主要为微细浸染状黄铁矿化蚀变岩型,次为石英黄铁矿脉型和石英多金属硫化物脉型;围岩蚀变有钾长石化、硅化、绢云母化、黄铁绢英岩化、绿泥石化、绿帘石、萤石化、碳酸盐化。运用LA-ICP-MS锆石U-Pb测年、岩石地球化学、流体包裹体、同位素等手段,查明庙岭金矿区花岗斑岩的特征与成因、成矿流体的类型、性质、来源与演化、成矿物质的来源以及矿床成因。庙岭金矿床热液成矿过程可划分为四个成矿阶段:黄铁矿石英阶段(Ⅰ)、石英黄铁矿阶段(Ⅱ)、石英多金属硫化物阶段(Ⅲ)和石英碳酸盐阶段(Ⅳ)。矿区内白家凹花岗斑岩脉的LA-ICPMS锆石U-Pb年龄为157Ma,形成于晚侏罗世;岩石地球化学及同位素特征显示,花岗斑岩属高分异的I型花岗岩,是下地壳部分熔融的产物,形成于古太平洋板块向欧亚板块俯冲的弧后陆缘伸展环境;其成岩年龄比成矿年龄(117Ma)早40Ma左右,故推测花岗斑岩与金成矿作用无关。黄铁矿的稀土元素组成兼具燕山期花岗岩和赋矿围岩地层的稀土元素特征,显示庙岭金矿床成矿物质来源于太古界太华群,且萃取了部分地层物质;稀土元素具明显铕异常、而铈无明显异常,表明成矿流体具弱还原性;黄铁矿的微量元素特征总体上反映了黄铁矿的热液成因,与岩浆其后热液关系密切,同时后期演化过程中与围岩发生了交代作用。流体包裹体综合研究表明,成矿流体为岩浆流体,由早期的中温、中-低盐度、还原环境下的H2O-Na Cl-CO2体系,向晚期的低温、低盐度的H2O-Na Cl体系演化。C-H-O同位素组成表明,成矿流体可能来源于燕山期岩浆期后热液,到演化后期有大气降水的加入。Pb同位素组成显示庙岭金矿床成矿物质来自于下地壳,混入部分地幔物质。Au元素来自早白垩世岩石圈拆沉作用导致壳幔混源岩浆,在岩浆期后热液流体中以Au(HS)和HAu(HS)2形式迁移;流体的沸腾、混合以及与围岩地层的水-岩反应改变了成矿流体的物理化学环境,促使Au沉淀富集成矿。
[Abstract]:Miaoling gold deposit, located in Xiong'ershan gold polymetallic deposit, is a structural altered rock type gold deposit. The gold deposit occurs in the near north-south fault, and the mineralization type is mainly micro-disseminated pyrite altered rock type, followed by quartz pyrite vein type and quartz polymetallic sulphide vein type, and the wall rock alteration includes potassium feldspar, silicification, sericite, etc. Yellow sericite lithotization, green mud petrifaction, verdanite, fluorinization, carbonization. By means of LA-ICP-MS zircon U-Pb dating, geochemistry, fluid inclusions and isotopes, the characteristics and genesis of granitic porphyry, the types, properties, sources and evolution of ore-forming fluids in Miaoling gold deposit are investigated. The origin of the ore-forming materials and the genesis of the deposits. The hydrothermal metallogenic process of Miaoling gold deposit can be divided into four metallogenic stages: pyrite quartz stage (鈪，

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