兴蒙造山带东部中生代斑岩型钼矿成矿系统的岩浆流体作用与成矿研究

发布时间：2018-01-20 02:37

本文关键词： 岩浆流体作用斑岩型钼矿中生代兴蒙造山带东部　出处：《吉林大学》2016年博士论文　论文类型：学位论文

【摘要】：研究区处于中亚造山带东段,是一个经历了古亚洲洋闭合、蒙古-鄂霍茨克洋、太平洋以及新生代深断裂等多次叠合作用的构造-岩浆-成矿区,是我国继秦岭钼矿带之后的又一钼矿资源基地。据统计目前已勘探的超大型钼矿床4个,大型及以上钼矿床20余,中小型钼矿床70余个,资源量700余万吨,成矿类型主要为斑岩型;其成矿时代主要发生在中生代,存在多期多阶段成矿特征,且发育强度不同;为了深入揭示研究区不同阶段流体、岩浆作用以及地球动力学过程对成矿的制约,我们开展了研究区中生代不同期次斑岩型钼矿的地质、流体包裹体、元素及同位素地球化学和年代学的研究;总结区域成矿规律,为深部找矿提供科学依据。建立了成岩成矿地质模型,取得的主要进展与成果如下:区内中生代斑岩型钼成矿作用划分为2期5个阶段:印支期早中三叠世(245-235Ma)和晚三叠世(209-200Ma),燕山期早中侏罗世(189-167Ma)、晚侏罗-早白垩世早期(151-125Ma)和早白垩世晚期(116-110Ma);其中早中侏罗世和晚侏罗-早白垩世矿化作用最强;早中侏罗世钼矿化作用主要分布在小兴安岭-张广才岭成矿带;晚侏罗-早白垩世早期钼矿床主要分布在大兴安岭地区;通过对兴蒙造山带东部已有斑岩型钼矿床资料的分析,研究区斑岩型钼矿矿石类型多为浸染型、脉型、细脉浸染型及角砾岩型;矿石组构包括自形-半自形-它形结构、叶片状-鳞片状-菊花状结构以及交代结构;构造包括细脉状-脉状-网脉状构造以及浸染状-细脉浸染状-团块状构造;蚀变分带性明显,大规模成矿作用与钾化、硅化及绢英岩化关系密切;流体包裹体特征表明:研究区斑岩型钼矿床成矿流体在早期高温阶段存在临界高盐流体;成矿阶段具有明显的中高温高盐和低盐流体共生的现象;在成矿晚阶段以中低盐度流体包裹体为主;整个流体演化过程经历高温气相、中高温流体不混溶或沸腾作用过程。普遍发育气液两相和含子矿物三相包裹体,成矿过程中普遍有co2参与,主成矿阶段温度较高(250℃,普遍大于300℃);不同时代气相组成存在着明显的差异,三叠纪钼矿床以普遍发育富co2包裹体为特征,而早中侏罗世包裹体气相组成中则普遍含有ch4成分;此外晚侏罗-早白垩世早期则既存在富co2又存在贫co2体系,而早白垩世晚期包裹体气相组成以h2o为主;成矿物质来源较为复杂,壳幔物质均有参与;早三叠世钼矿床成矿斑岩为二长花岗斑岩-花岗斑岩组合,属高钾钙碱性系列、准铝质-过铝质岩石系列,岩浆源于古老的陆壳基底的部分熔融或岩浆起源于新生下地壳部分熔融,并受到老的陆壳混染;晚三叠世铜钼矿床成矿斑岩主要为花岗闪长斑岩,属高钾钙碱性系列、过铝质岩石,岩浆形成于俯冲洋壳的部分熔融;早中侏罗世钼矿床成矿斑岩主要为似斑状二长花岗岩-二长花岗斑岩和少量的花岗闪长斑岩组合,属于钾玄岩系列-高钾钙碱性系列、准铝质-过铝质岩石,起源于加厚的下地壳部分熔融;晚侏罗-早白垩世早期钼矿床与成矿关系密切的岩石为二长花岗斑岩和花岗斑岩组合,属高钾钙碱性系列-钾玄岩系列、准铝质-过铝质,起源于中新元古代亏损地幔增生的年轻下地壳物质或老的下地壳的部分熔融;早白垩世晚期钼矿床与成矿关系密切的岩石为花岗闪长斑岩和少量的花岗斑岩,属钙碱性系列、钠质、过铝质岩石,起源于年轻的底侵下地壳。不同期次钼矿床形成于不同的构造环境,早中三叠世钼矿主要形成于华北板块与西伯利亚板块碰撞造山背景下的伸展环境;晚三叠世铜钼矿床形成于俯冲的陆缘弧环境;早中侏罗世钼矿床的形成与太平洋板块的俯冲关系密切,少数(乌奴格吐山)受蒙古-鄂霍茨克洋闭合后陆陆碰撞体系的影响;晚侏罗-早白垩世早期钼矿床经历了古亚洲洋构造域向滨西太平洋构造域的转换,区域发生陆内伸展与岩石圈大规模减薄作用;而早白垩世晚期成矿作用应形成于伊泽奈崎板块俯冲作用之后的构造折返期相关联的陆缘弧环境;斑岩钼(铜)矿常分布在偏挤压的陆缘弧和大陆碰撞造山带环境,基底多为古老的陆壳或年轻的陆壳、洋壳,而斑岩钼矿多出现在偏伸展的板块俯冲-弧后-造山后环境,基底可以为新生的陆壳或残余洋壳;两组或多组断裂交汇部位为成矿有利部位,同时隐爆角砾岩发育的地段为良好的容矿导矿部位。早中三叠世华北地台和西伯利亚板块发生碰撞,在碰撞过程中使得下地壳加厚,加厚的下地壳发生部分熔融,形成了大兴安岭中南段-西拉沐伦河早中三叠世钼矿化作用;而早中侏罗世太平洋板块的俯冲作用使得兴蒙造山带岩石圈(大陆)加厚,加厚的岩石圈加速了壳幔物质相互作用的速度,使得吉黑东部发生大规模的钼矿化作用,这也是早中侏罗世岩浆多具有壳幔混合源特征的主要原因;而在大兴安岭北段西侧受蒙古-鄂霍茨克洋闭合后陆陆碰撞体系的影响形成了乌奴格吐山铜钼矿的形成;随着俯冲作用的进行岩石圈逐渐加厚,进入晚侏罗-早白垩世早期,构造环境由挤压转变为伸展环境,岩石圈开始拆沉减薄,拆沉过程中软流圈物质上涌,加速了下部地壳的部分熔融速度,形成了大兴安岭地区大规模的晚侏罗-早白垩世早期的钼矿化作用;早白垩世晚期在古太平洋板块(Izanagi)俯冲作用之后的构造折返期,次生岩石圈地幔经部分熔融产生类埃达克质岩石,经结晶分异作用形成铜(金)矿化,上侵过程中与下地壳重熔岩浆混合形成钼矿化。
[Abstract]:The study area in the eastern section of the Central Asian orogenic belt, is an experienced closure of the paleo Asian Ocean, the Mongolia Okhotsk ocean, Pacific tectonic and Cenozoic deep fault several superimposed effect of magmatic metallogenic zone, is our country after Qinling Mountains and a molybdenum ore belt of molybdenum resource base. According to statistics at present large molybdenum deposit has been the exploration of 4 and above, more than 20 large molybdenum deposits, small and medium sized molybdenum deposit of more than 70, the amount of resources of more than 700 tons, ore types are mainly porphyry type; metallogenic epoch mainly occurred in the Mesozoic, there are characteristics of multi-stage mineralization stage, and the development of different intensity; in order to reveal the different the study area of fluid, restricting the magmatism and the earth dynamics process of mineralization, we carried out geological research in different stages of Mesozoic porphyry molybdenum deposit, fluid inclusion study, element and isotope geochemistry and geochronology; summary Metallogenic regularity for the deep ore prospecting and provide scientific basis. The diagenetic and metallogenic geological model, the main results obtained are as follows: the Mesozoic porphyry molybdenum mineralization is divided into 5 stages: the 2 stage of Indosinian Early Triassic in three (245-235Ma) and three late Triassic (209-200Ma), Yanshan during the early and middle Jurassic (189-167Ma), late Jurassic Early Cretaceous (151-125Ma) and early Cretaceous (116-110Ma); the early Jurassic and late Jurassic Early Cretaceous mineralization in the strongest; early Middle Jurassic molybdenum mineralization is mainly distributed in the Xingan mountains - Zhang Guangcai Ling metallogenic belt; Late Jurassic Early Cretaceous Mo mineral deposits are mainly distributed in the Greater Khingan Range area; through the analysis of the data of the eastern xing'an-mongolian orogenic belt has porphyry molybdenum deposit, porphyry molybdenum ore research area type is disseminated, vein type, veinlet disseminated type and breccia type; ore fabric including self Shape - subhedral anhedral structure, leaf shaped scaly - Chrysanthemum structure and metasomatic structure; structure including veinlet stockwork structure, veinlet disseminated veinlet - smallmassive; alteration zonation obviously, mineralization and potassium, silicification and Juan Yingyan relationship close; show the characteristics of fluid inclusions: ore-forming fluid of porphyry molybdenum deposit in study area are critical in the early stage of high temperature and high salinity fluid; ore-forming stage has obvious in high temperature and high salt and low salt fluid symbiosis; with low salinity fluid inclusions in the late stage; the fluid evolution of high temperature gas phase. In the high temperature fluid immiscibility or boiling process. Common development of gas-liquid two-phase and halite bearing three-phase inclusions and metallogenic process in general CO2 participate in the main mineralization stage, high temperature (250 DEG C, generally higher than 300 DEG C); different age of gas The phase composition has the obvious difference, the Triassic molybdenum deposits generally developed to CO2 rich inclusions, and early Middle Jurassic inclusions in the phase composition generally contains CH4 components; in the late Jurassic Early Cretaceous early is rich CO2 and poor in CO2 system, and the early Cretaceous phase composition in inclusions H2O; source of ore-forming material is complex, crust and mantle were involved; Three Early Triassic molybdenum metallogenic porphyry two granite porphyry granite porphyry, belongs to high potassium calc alkaline series, metaluminous peraluminous series, magma derived from the continental basement of the ancient magma originated from partial melting or new partial melting of lower crust, and by the old Lu Kehun staining; three late Triassic metallogenic porphyry copper molybdenum deposit is mainly granodiorite porphyry, belongs to high potassium calc alkaline series, peraluminous rocks, magma formed in the partial melting of subducted oceanic crust; early The Middle Jurassic porphyry molybdenum deposit mineralization is mainly porphyritic granite two - two granite porphyry and small granodiorite porphyry, belonging to shoshonite series high potassium calc alkaline series, metaluminous peraluminous rocks originated from partial melting of lower crust thickening; Late Jurassic Early Cretaceous early relationship between molybdenum deposit closely related to rock two long granite porphyry and granite porphyry, belongs to high potassium calc alkaline series shoshonite series, metaluminous peraluminous, originated in the Neoproterozoic depleted mantle hyperplasia young lower crust or old lower crust partial melting; early Late Cretaceous molybdenum deposit and mineralization relationship close the rock is granodiorite porphyry and small granite porphyry belong to the calc alkaline series, sodic, peraluminous, originated from the lower crust underplating young. Different stages of molybdenum deposits formed in different tectonic environments, early Triassic in three Molybdenum is mainly formed in the North China plate and the Siberia plate collision under the background of extensional environment; the continental margin arc environment of Late Triassic three copper molybdenum deposit formed in the subduction of the early Middle Jurassic; formation of molybdenum deposits and the subduction of the Pacific plate is closely related to the minority (Wunugetushan) affected by the closure of the Mongolia Okhotsk ocean after the collision system; Late Jurassic Early Cretaceous molybdenum deposit experienced paleoasian domain to the Western circum Pacific tectonic domain, regional intracontinental extension and major lithospheric thinning effect; and the early Cretaceous mineralization should be formed after the Yuyizenai Qi subduction tectonic exhumation stage in continental margin the arc; porphyry molybdenum (copper) deposits are mainly distributed in partial extrusion of the continental margin arc and continental collision orogenic belt, the basement for the ancient continental crust or young continental crust and oceanic crust, and the porphyry molybdenum multi The emergence of environmental in the partial extensional plate subduction orogenic arc, continental crust or basement for residual oceanic crust new; two or more groups of fracture intersection is a mineralization favorable position, while the cryptoexplosive breccia development area as a good guide ore mine site. In three the Early Triassic of North China Taiwan and Siberia plate collision in the collision process of the crustal thickening, the occurrence of partial melting of the thickened lower crust, forming the Greater Khingan Range - South section of Xilamulun River in the Early Triassic three molybdenum mineralization; and the subduction of the Pacific plate makes the early Middle Jurassic Xing Meng orogenic lithosphere (continental) thickening, thickening the acceleration of the lithosphere crust mantle interaction speed, the Jilin Heilongjiang Eastern molybdenum mineralization in large scale, the main causes of crust and mantle source characteristics of Jurassic magma has this is early in; while in the north section of the West Xingan The affected side of the Mongolia Okhotsk ocean closed after the collision of the formation of the system has formed the Wunugetushan copper molybdenum ore; with the subduction of lithospheric thickening, into the late Jurassic Early Cretaceous, the tectonic environment changed from compression to extension environment, the beginning of lithosphere delamination and thinning, delamination process of soft coil material upwelling, accelerated partial melting velocity of lower crust, forming a large-scale late Jurassic Early Cretaceous in Greater Khingan Range molybdenum mineralization early; Early Cretaceous in the paleo Pacific plate (Izanagi) after the subduction tectonic exhumation stage, secondary lithospheric mantle by partial melting of adakitic rocks, by crystallization differentiation to form copper (gold) mineralization, intrusion process and lower crust remelting magma mixed to form molybdenum mineralization.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P618.65

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