【作者】 费光春；

【导师】 温春齐；

【作者基本信息】 成都理工大学 ， 矿物学、岩石学、矿床学， 2010， 博士

【摘要】 西藏扎雪—金达铅锌多金属矿成矿带内嘉黎县绒多乡—墨竹工卡县门巴乡—工布江达县金达镇的铜铅锌钼银金多金属矿集区是冈底斯东段近年来发现的重要成矿区域,洞中拉铅锌矿床是该成矿带内新发现的矿床,研究程度很低。本文以板块构造理论和碰撞造山带成矿理论为基础,系统的运用现代矿床学、地球化学理论和高精度的分析测试方法,通过对洞中拉铅锌矿床成矿作用的研究,取得以下创新成果与认识:1)矿体呈层状,似层状,透镜状,赋存于中二叠统洛巴堆组（P2l）灰岩（大理岩）、板岩中。矿石构造主要有块状构造、浸染状构造、细脉状构造、角砾状构造、条带状构造等;结构主要有半自形粒状结构、他形粒状结构、包含结构、共边结构、交代残余结构、固溶体分离结构等。金属矿物主要有黄铁矿、磁黄铁矿、黄铜矿、方铅矿,闪锌矿;次为蓝铜矿,斑铜矿等。脉石矿物有石英、长石、石榴子石、绿泥石、绿帘石、方解石等。2)成矿过程分为2个期,即热液成矿期和表生期。其中,热液成矿期又分三个阶段:磁黄铁矿黄铜矿阶段、闪锌矿方铅矿阶段和方解石阶段,热液成矿期是最主要的成矿期。3)查明了矿区辉绿玢岩和花岗斑岩的岩石地球化学特征。辉绿玢岩为拉斑玄武岩系列,主量元素以富Al₂O₃ （15.68%～17.61%）、低MgO（3.28%⁵.97%）、中等TiO₂（1.89%².87%）、贫K₂O（0.14%⁰.56%）、Na₂O> K₂O为特征;稀土元素总量相对较低,富集轻稀土元素（LREE/HREE=3.76⁴.37,平均4）,弱负Eu异常（δEu=0.58⁰.93,平均0.81）。微量元素以Nb、Ta、Hf等高场强元素相对富集而Ba、Sr、K等大离子亲石元素相对亏损为特征。花岗斑岩属过铝质钙碱性系列,具有地壳重熔型特点。4)铅同位素具有稳定铅的特点,主要来自上部地壳;硫同位素在频率直方图上呈明显的塔式分布,总硫同位素为4.7‰,可能主要源于深源（或岩浆）,次为壳源。稀有气体同位素表明流体具有壳幔混合源的特征。硫化物锶同位素研究表明主要来源于地壳。碳同位素研究表明,碳主要来自海相沉积碳酸盐岩的溶解作用。5)查明了流体包裹体的岩相学特征,温度、盐度、压力和成分,成矿流体的物理化学条件和成矿流体来源。包裹体类型以气液水包裹体为主,少量纯液相水包裹体和极少量气相包裹体。成矿流体具有中低温（均一温度126.83²40.31℃）低盐度（0.88⁴.94 wt%）低密度（0.83～0.95g/cm3）浅成（26.47⁶7.03 MPa）。流体气相成分以H₂O为主。液相离子成分中,主要以SO₄^2-, Cl^-, Na⁺为主;流体酸碱度（pH）值介于5.036～5.526之间;氧化还原电位（Eh）为0.1745～0.231。成矿流体的逸度lgfo₂、lgfco₂和lgfs₂从热液期成矿作用早阶段到晚阶段都具有降低的趋势。成矿溶液中硫的溶解类型以H₂S、HS^-还原硫形式占绝对优势,其次是S2-形式;碳的溶解类型以CO₂和H₂CO₃为主,其次为HCO₃^-。成矿流体主要来源于大气降水成因的循环地下热水。6)查明了铅锌的迁移沉淀机制。成矿流体中的总锌活度从磁黄铁矿黄铜矿阶段（Ⅰ阶段）到闪锌矿方铅矿阶段（Ⅱ阶段）到方解石阶段（Ⅲ阶段）显示为由高到低的变化规律;铅的总活度也表现出降低后升高的变化规律,但是整体各成矿阶段还是呈现降低的趋势。锌的络合物中,磁黄铁矿黄铜矿闪锌矿阶段锌主要以Zn（HS）₃^-和ZnS（H₂S）₂⁰形式存在,其次为ZnCl₃^-和ZnCl⁺形式;在闪锌矿方铅矿阶段,主要以ZnCl₃^-和ZnCl⁺形式存在;在闪锌矿方解石阶段（Ⅲ阶段）主要以Zn（HS）₃^-形式存在。铅的络合物中,磁黄铁矿黄铜矿闪锌矿阶段,主要以PbS（H₂S）₂⁰形式存在;在闪锌矿方铅矿阶段,主要以PbCl⁺和PbCl₃^-形式存在;在闪锌矿方解石阶段,络合物的活度很低,几乎为零。7)查明了成岩成矿年龄。矿区岩体为复式岩体,主岩浆期辉绿玢岩和花岗斑岩锆石SHRIMP年龄分别为117.1±1.0 Ma和124.4±1.9Ma,形成于燕山晚期。花岗斑岩和辉绿玢岩脉年龄介于38.47⁵3.35Ma之间,结合洞中拉-亚贵拉-沙让矿集区（4公里范围）内发现主碰撞期花岗岩体（沙让角闪石闪长岩体锆石SHRIMP U-Pb年龄为49.0±1.0Ma,含矿斑岩SHRIMP U-Pb年龄为53±1.0Ma,沙让花岗岩为55.0±0.53Ma,花岗斑岩为53.68±0.38Ma,石英斑岩为53.16±0.40Ma;亚贵拉石英斑岩为53 Ma）,形成于喜山早期。通过含矿石英脉Ar-Ar定年,获取了洞中拉铅锌矿的成矿年龄为42.2±1.7 Ma。首次提出洞中拉铅锌矿床为与燕山晚期和喜山早期岩浆活动有关的印-亚大陆主碰撞期作用（65⁴0Ma）而形成的矿床。8)通过对流体包裹体的物理化学条件的研究,基于大量的地质事实,结合大量的测试分析数据,并与各种类型的典型铅锌矿床对比,首次提出洞中拉铅锌矿床属于中低温热液型铅锌矿床。系统分析洞中拉铅锌矿床的成矿作用基础上,最终建立了洞中拉铅锌矿床的成矿模式。更多还原

【Abstract】 Dongzhongla deposit, located in the Zhaxue-Jinda lead-zinic mining area , Nyainqentanglha Range,Tibet,is the new founded lead-zinc polymetallic deposit and the degree research of geology in this area is low.In this paper,we use did works with the mineral deposit,geochemistry,plate tectonics, collision orogen theory, we gain the innovation achievements and judgements:1)The shape of the orebody is layered,stratoid,lens,located in the contact zone between limestone （griotte）and calcareous slate in Luobadui formation.The ore structure include massive,impregnation,vein,breccia and ribbon;the texture include euhedral crystal,subhedron,contained,coterminal,metasomatic relict,solid solution separated.The metallic minerals are pyrrhotite, pyrites,chalcopyrite,galena,sphalerite, azurite and bornite.The rocky mineral are quartz, feldspar,garnet,chlorite,epidote and calcite.2)The metallogenic process of Dongzhongla deposit are two stage,which are epithermal ore forming stage and supergene stage.When it terms to epithermal ore forming stage,we divide it to three period also,which are pyrrhotite-chalcopyrite period , galena-sphalerite period and calcite period.So, epithermal ore forming stage is the most important metallogenic period3)allgovite in Dong zhongla area belong to the alkali basalts series.The major elements of the allgovite are characterized by high Al₂O₃, intermddiate TiO₂,poor MgO and K₂O , and Na₂O> K₂O.The allgovite have high content of∑REE, a weak negative Eu anomaly or no Eu anomaly（δEu = 0.58⁰.93, with a mean of 0.81）,Chondrite-normalized REE diagrams show LREE-enriched patterns （LREE/HREE=3.76⁴.37,with a mean of 4）.traceelements are characterized by enrichments in HFSE（Nb、Ta、Hf and Th） and depletments in LILE（Ba、Sr and K）. They are similar to ocean island basalts（OIB）,the magmacontent were likely from enrichment mantl and have not experienced crustal contamination.The porphyry granite belong to peraluminous calc-alkaline series and the result of the crust crustal thicking melting.4)The lead-znic mineral are mainly from strata; Pb isotope belong to normal lead,and mainly from supracrust;the sulfur isotope is mainly from the magma.The nobel gas isotope shows the fluid is from crust and mantl;the sulfide strontium show that the fluid is from crust.The C is mainly from crust.5)There are three types of fluid inclusions in Dongzhongla deposit,mainly are gas-liquid fluid inclusions. The fluid belong to low and medium temperature,low sality,low density and formed in a low pressureand shallow environment. The gas compositions is dominated by H₂O,the liguid ion is SO42-,Cl-,Na+,belong to Cl--SO42--K+-Na+ hydrochemical type. The pH is weakly acidic, shows decreasing tendency in the different epithermal ore period ;The fugacity also shows decreasing tendency.The the ore fluids may have been derived from subsurface airsatutated water prodorminent.6)The total lead and zinic activity in the fluid have the law that,form pyrrhotite-chalcopyrite period,galena-sphalerite period and calcite period drop sharply.In the zinic complex compound,the Zn（HS）3- and ZnS（H₂S）20 prodorminent in pyrrhotite-chalcopyrite period; Zn（HS）3- prodorminent in galena-sphalerite period.In the lead complex compound, the PbS（H₂S）20 prodorminent in pyrrhotite-chalcopyrite period; PbCl+和PbCl3- prodorminent in the galena-sphalerite period.7)The magmatic body are complex massif.the porphyry granite Zircon SHRIMP U-Pb age is 124.4±1.9 Ma, and the allgovite Zircon SHRIMP U-Pb age is117.1±1.0 Ma, in late stage of Yanshan.And the dike age is from 38.47 to 53.35Ma（K-Ar）,in early Himalayan.The Laser microprobe 40Ar-39Ar geochronology of ore quartz age is 42.2±1.7 Ma,represent the metallogenic age.we firstly put forward that Dongzhongla lesd-zinic deposit were metallogenic during main Indian-Asian collision period（41⁶5Ma） with the magmatic movement in late Yanshan and early Himalayan.8)Based on the physical chemical condition of the fluid,systemly analyzing the metallgenesis ,and combined with the geological evidence and large testing data, contrast with the different typical type lead-zinic deposit,we conclude that the Dongzhongla lead-zinic deposit is low and medium temperature epithermal type ,and establish the collision metallogenic model.更多还原