大兴安岭中北段古中公路钼矿床形成时代与矿床成因

发布时间：2017-12-27 15:24

本文关键词：大兴安岭中北段古中公路钼矿床形成时代与矿床成因　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：古中公路钼矿床位于黑龙江省加格达奇市北约60km处,地处中亚造山带东段的大兴安岭中北部。钼矿体呈脉状产于中细粒二长花岗岩体之中。本文在收集分析区域和矿区资料的基础上,通过野外地质调研、室内测试及综合研究,查明古中公路的成矿地质条件、矿床地质特征、成矿物理化学条件。并结合相邻区域代表性钼矿床的综合对比研究,明确矿床成因及成岩成矿时代。除第四系外,矿区内出露的地层主要有下泥盆统—中泥盆统泥鳅河组,构造主要见有晚加里东—海西期和燕山晚期脆韧性断裂构造。矿区内侵入岩复杂,与钼矿化在时空及成因上密切相关的侵入岩为中细粒二长花岗岩。矿石中主要金属矿物为辉钼矿、黄铁矿、方铅矿、闪锌矿、黄铜矿、磁黄铁矿、白钨矿;非金属矿物包括石英、钾长石、斜长石、黑云母、绢云母、绿泥石等。矿石中金属矿物主要呈自形—半自形晶粒状结构、鳞片状结构、交代结构。主要构造为薄膜状、脉状构造、浸染状构造、细脉状构造。围岩蚀变发育钾化、硅化、黑云母化、绿泥石化、绿帘石化、绢云母化和碳酸盐化,其中硅化、钾化和黑云母化与钼矿化时空关系密切。根据古中公路钼矿床中不同脉体之间的穿切关系、矿石的结构和构造、矿物共生组合及交生关系以及围岩蚀变等特征,可将古中公路钼矿床划分为一个成矿期和三个成矿阶段,成矿阶段可划分为石英-钾长石、石英-辉钼矿-多金属硫化物及石英-方解石-黄铁矿三个阶段。其中,石英-辉钼矿-多金属硫化物阶段为主成矿阶段。流体包裹体研究表明:主成矿阶段石英矿物颗粒中主要发育气液两相包裹体,少量含子矿物三相包裹体和含CO2三相包裹体。不同类型包裹体的均一温度介于196.3~450℃之间,盐度可分为0.18%~12.62%和45.33%~53.26%两个不同区间,成矿流体为中高温、高盐度的NaCl-H2O-CO2体系,在主成矿阶段流体发生过流体不混溶作用,是钼元素富集沉淀的主要机制。同位素年代学研究表明,与成矿相关的中细粒二长花岗岩体的LA-ICP-MS锆石U-Pb同位素年龄为(146.3±2.5)Ma;2件辉钼矿样品的Re-Os同位素模式年龄分别为142.4±2.9Ma和142.3±2.0Ma,表明成岩成矿作用发生于晚侏罗世-早白垩世。辉钼矿中ω(Re)含量分别为11.894×10~（-6）和11.584×10~（-6）,揭示成矿物质来源主要为地壳来源。综合成矿地质条件、矿床地质特征及成矿流体特征认为,该矿床在成因上属斑岩型,形成于区域碰撞后伸展的构造背景。
[Abstract]:The ancient Middle highway molybdenum deposit is located in the north central part of Greater Khingan Range in the eastern section of the Central Asian orogenic belt, located at 60km, Jiagedaqi, Heilongjiang province. The molybdenum ore body is produced in the vein of the medium fine granitic two - long granitoid. Based on the collection and analysis of the data in the area and mining area, through the field geological investigation, indoor test and comprehensive research, we find out the metallogenic geological conditions, geological characteristics and metallogenic physical and chemical conditions of the middle ancient highway. Combined with the comprehensive comparative study of the representative molybdenum deposits in adjacent areas, the genesis of the deposit and the age of diagenesis and mineralization are clearly defined. Besides the quaternary system, the outcropping strata in the mining area mainly consist of the Lower Devonian Middle Devonian loach River group. The main structures are late Caledonian Hercynian and late Yanshan brittle ductile fault structures. Mine intrusive rock complex, and molybdenum mineralization in space and origin is closely related to the intrusive rocks in two fine-grained granite. The main metallic minerals in the ore are molybdenite, pyrite, galena, sphalerite, chalcopyrite, pyrrhotite and scheelite. Nonmetallic minerals include quartz, potash feldspar, Xie Changshi, biotite, sericite, chlorite and so on. Ore minerals are mainly euhedral and subhedral grain structure, flake structure, metasomatic structure. The main structure is thin film, pulse structure, disseminated structure and fine pulse structure. Wall rock alteration is developed by potash, silicification, biotite, chlorinization, epidote, sericite and carbonation, and silicification, potash and biotite are closely related to molybdenum mineralization. According to the ancient road in molybdenum deposits in different veins between the cut, ore structures and mineral assemblages and the relationship between students and the wall rock alteration characteristics, can be divided into the ancient road of molybdenum deposit in a metallogenic period and three mineralization stages, metallogenic stage can be divided into quartz - feldspar quartz molybdenite polymetallic sulfide quartz and calcite pyrite in three stages. Among them, quartz - molybdenite - polymetallic sulfide phase is the main stage of mineralization. Fluid inclusions research shows that: in the main metallogenic stage, there are mainly gas liquid two phase inclusions in quartz mineral particles, a few inclusions containing sub minerals and three-phase inclusions containing CO2. Between different types of inclusions, homogenization temperature between 196.3~450 DEG C, salinity can be divided into 0.18%~12.62% and 45.33%~53.26% two different interval, the ore-forming fluid is in high temperature and high salinity of the NaCl-H2O-CO2 system in the main mineralization stage fluid fluid immiscibility, molybdenum element enrichment precipitation mechanism. The study of isotope chronology shows that mineralization and related fine-grained granite two long LA-ICP-MS zircon U-Pb isotopic age (146.3 + 2.5) Ma; Re-Os isotope model age 2 molybdenite samples were 142.4 + 2.9Ma and 142.3 + 2.0Ma, shows that diagenesis and mineralization occurred in the late Jurassic and early cretaceous. The contents of omega (Re) in molybdenite are 11.894 * 10~ (-6) and 11.584 x 10~ (-6), respectively. It is revealed that the main source of the mineral formation is the source of the crust. Based on the comprehensive metallogenic geological conditions, geological characteristics and ore forming fluid characteristics, it is considered that the deposit belongs to porphyry type and formed in the tectonic setting of regional post collisional extension.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.65

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