【作者】 郑文宝；

【导师】 陈毓川；

【作者基本信息】 成都理工大学 ， 矿物学、岩石学、矿床学， 2012， 博士

【摘要】 西藏冈底斯成矿带是目前青藏高原勘查与研究程度最高、发现矿床及设立整装勘查区最多、查明矿产资源储量最大的构造-岩浆岩带。甲玛铜多金属矿是冈底斯成矿带中东段第一个勘查程度最高、拥有多种成矿元素与矿体类型、已正式投入生产并为藏区带来了经济效益的超大型斑岩-矽卡岩型矿床。通过对矿床控矿条件、成矿模式、找矿模型、找矿标志等方面的研究达到为矿区外围及区域找矿指明方向之目的，本文在长达6年的野外地质调查和全面梳理前人工作基础上，采用了现代矿床学研究方法，结合了多学科知识，应用了先进的测试方法和技术，得到了以下认识：1、矿区地层主要包括林布宗组（K1l）砂板岩、角岩与多底沟组（J3d）灰岩、大理岩。林布宗组除了为上部石榴子石矽卡岩和角岩矿石的形成提供了部分成矿物质和容矿空间外，还为矽卡岩铜多金属矿体的形成提供了重要的岩性圈闭条件；多底沟组为矽卡岩的形成提供了必须的钙质来源。矿区岩浆岩主要有五类，以高钾钙碱性岩为主，形成于后碰撞造山环境；岩浆混合作用明显，基性单元主要为辉长质岩浆；岩浆岩侵位次序大致为：石英闪长玢岩→花岗斑岩→二长花岗斑岩→花岗闪长斑岩，其中石英闪长玢岩与铜矿化有关，而二长花岗斑岩与钼矿化关系密切；UST结构、石英斑晶的溶蚀现象以及熔融-流体混合包裹体的发现均为岩浆-热液的过渡提供了证据。推覆构造控制着矽卡岩主矿体的产出，滑覆构造控制了矿区东部矽卡岩小矿体的产出。2、对矿床地质特征进行了详细的研究，包括：①提出甲玛矿床主要是由产于上覆林布宗组角岩中铜钼矿体、产于中部层间构造带与斑岩接触带矽卡岩中的铜多金属矿体、产于深部隐伏斑岩中钼（铜）矿体与产于外围构造破碎带中的独立金矿体构成的“四位一体”式斑岩-矽卡岩矿床；②矽卡岩矿石以稠密浸染状、团块状、脉状构造产出为主，角岩与斑岩矿石中主要的构造为浸染-细脉状，矿石结构均以交代作用和固溶体分离作用形成为主；③主要的矿石矿物包括黄铜矿、斑铜矿、辉钼矿、辉铜矿、黝铜矿、方铅矿、闪锌矿、自然金等，脉石矿物以矽卡岩矿物（包含石榴子石、辉石、硅灰石等）和石英为主，含少量硬石膏、方解石、萤石等；④完善了矽卡岩中金属矿物与成矿元素的分带模式：由岩体中心向外到中部至矽卡岩前缘与大理岩接触带，矽卡岩中矿石矿物组合对应的成矿元素分带为Mo+Cu±Au±Ag→Cu±Mo±Au±Ag→Pb+Zn+Cu±Au±Ag±Mo→Au±Ag±Cu；⑤建立了矽卡岩矿物组合及其成分的分带模型：整体上，硅灰石矽卡岩相对于石榴子石矽卡岩与辉石矽卡岩较独立，主要分布在近岩体接触带及中部带垂向上的中下部至大理岩接触部位；而石榴子石、辉石矽卡岩由近岩体接触带→中部带→远部带的矽卡岩前缘，石榴子石/辉石比值从大于10:1→约5:1→约2:1；石榴子石颜色及成分由红-棕色钙铁榴石（Ad＞80）→棕-黄色钙铁石榴子石（Ad50-80）→墨绿色-淡黄色钙铝榴石（Gr＞50）；⑥划分了甲玛斑岩矿床的蚀变分带，岩株（枝）中以钾、硅化为主，岩体上方角岩中出现中心泥化带向外围过渡为绢英岩化带至外围青磐岩化带的圈层分布特征；⑦总结了三个矿化期次，其中气水-热液矿化期又包括早期矽卡岩-硅酸盐阶段、晚期退化蚀变阶段、石英-铜硫化物阶段、石英-铜钼硫化物阶段、石英-铜铅锌硫化物阶段以及石英-金成矿阶段。3、对本次划分出的四种矿体类型都进行了详细的地球化学研究。一方面针对矽卡岩形成及矿化过程中出现的矽卡岩化大理岩、石榴子石为主的无矿矽卡岩、硅灰石为主的无矿矽卡岩、石榴子石为主的含矿矽卡岩与硅灰石为主的含矿矽卡岩分别进行了常量元素、微量元素及稀土元素特征研究，整体分析了蚀变过程与矿化过程中的元素地球化学行为，为矽卡岩成矿作用过程及矿床成因的研究提供了依据；另一方面对ZK4504孔含金石英闪长玢岩与矿区其他钻孔中不含金石英闪长玢岩进行了地球化学特征对比研究，提出晚期热液金矿化主要形成于斑岩系统外围构造破碎带中，受温度、压力控制，而与围岩性质关系不密切。4、矿床中主要金属硫化物与硫酸盐中硫同位素组成具有高度均一性，中值处于零附近，显示了硫的岩浆来源特征；矿石铅同位素组成中²⁰⁶Pb/²⁰⁴Pb一般为18‰～19‰，²⁰⁷Pb/²⁰⁴Pb为15.4‰～15.8‰，²⁰⁸Pb/²⁰⁴Pb为38.4‰～39‰，与矿区斑岩全岩铅同位素组成特征一致，铅同位素表现出造山带以及与岩浆作用有关的壳幔混合铅来源特点，介于雅鲁藏布江蛇绿岩和喜马拉雅片麻岩和花岗岩的铅同位素组成之间，与拉萨地体岩浆岩的铅同位素组成一致；对比了不同成因矿床中矿石硅同位素的组成特征，证实甲玛矽卡岩的硅同位素组成与矿区岩浆岩完全一致，而与典型喷流矿床中喷流岩相差较远；氢、氧同位素的研究证实了甲玛成矿系统中流体起源于岩浆热液，晚期有大气降水的参与，结合不同成矿阶段流体包裹体盐度-温度的变化特征，提出了甲玛成矿流体的演化模式。5、进行了矿床年代学的研究，测得甲玛矿床成岩成矿年龄分别为16Ma±和15Ma±，这一重要地质事实否定了晚侏罗世至早白垩喷流沉积成矿的矿床成因观点，支持了斑岩-矽卡岩成矿的认识。6、在对矿床进行全面地质、地球化学特征研究的基础上，将甲玛矿床与国内外典型斑岩-矽卡岩矿床进行了类比研究，分析了彼此之间的异同点。据此，本文认为岩浆活动为成矿提供了成矿物质来源，构造提供了矿体的定位空间，岩性为矿体形成提供了良好的圈闭，岩浆-构造-岩性圈闭的耦合作用，形成了甲玛超大型矿床。并提出了矿床成矿流体侧向逃逸、垂向逃逸的成矿动力学机制，从而为在不同空间位置寻找不同类型矿体指明了方向，建立了矿床成矿模式；在此基础上，综合勘查地球物理、勘查地球化学等信息，建立了较新颖的斑岩铜矿元素分带找矿模型与传统的地质-地球物理-地球化学找矿模型，并结合矿区外围的找矿实践，初步证实了找矿模型的实用性。7、总之，基于甲玛矿床“四位一体”的找矿勘查模式，通过长达4年多近350个钻孔的验证，不仅实现了矽卡岩矿体的找矿突破，同时在0线～40线上部发现了产于角岩中的铜钼矿体，在深部还发现了产于二长花岗斑岩与石英闪长玢岩中的斑岩钼（铜）矿体。已经控制和探明矿床铜资源量超过600万吨，钼资源量超过60万吨，铅锌资源量超过50万吨，伴生金超过140吨，伴生银超过8000吨，当量铜资源量达1500万吨以上。甲玛铜多金属矿成为西藏第一大斑岩-矽卡岩型矿床，取得了重大找矿突破。更多还原

【Abstract】 At present, Gangdese metallogenic belt is the largest tectonic-magmatite belts which makesthe highest level of prospecting and studying, discovering ore deposits, setting up the mostexploration zone and proving through investigation mineral resources reserves. Jiama copperpolymetallic ore deposit is the highest level of prospecting, possessing a variety of ore-formingelements and ore body types of porphyry-skarn deposit in middle east of Gangdese metallogenicbelt, which has investment in producing and taking economic benefit for Tibetan. Throughstudying on ore-controlling conditions, metallogenic model、prospecting model and explorationmarkers etc, all of them are to get a clearly prospecting direction in ore field and outside. Duringsix years based on geological field work and clearing up previous work, we adopting moderndeposit research method, combining with multidisciplinary knowledge, applying advanced testmethod and technology. At last, we obtaining some understandings as below：1. Ore field mainly comprise of Linbuzong formation sandy slate, hornfels and Duodigouformation limestone, marble. Linbuzong formation offer metallogenic materials and hoststructures for upper garnet skarn and hornfels, expect that it also offer lithology entrapmentconditions for copper polymetallic ore deposit; Duodigou formation took calcium for skarnforming. There are five types of magma in the ore field, and they are mainly high-K calc-alkaline,forming from post-collision orogenesis condition; magma migmatization is obvious, the base unitsmainly are gabbroic magma; the sequence of magma invasion is: quartz diorite porphyrite→granite porphyry→monzonite granite porphyry→granodiorite-porphyry, and Cu mineralizationhas close relation with quartz diorite porphyrite, while Mo mineralization has close relation withmonzonite granite-porphyry; UST structure, erosion of quartz phenocryst and melting-fluidmixing inclusion all offer evidence for magma-hydrothermal transition. Nappe structure controlthe occurrence of mother-lode and sliding structures control the squats occurrence in eastern orefield.2. Making a detailed study on geology of deposits, includes:①Putting forward Jiamadeposit is a “quaternity “type porphyry-skarn deposits which is mainly comprise of molybdenumore body bearing in upper Linzongbu formation, Cu polymetal ore body bearing in medi-interlayertectonic zone and porphyry contact zones, Cu-Mo ore body bearing in bathy-hidden porphyry andAu ore body bearing outside of structure fracture zone;②The skarn ore yield by dense disseminated structure, cloddy, vein structure, hornfels and porphyry ore structure mainly isdisseminated-stringer, and they forming because of metasomatism and solid solution segregation;③The mainly ore mineral are chalcopyrite, bornite, molybdenite, cyprite, tetrahedrite, galena,sphalerite and native gold etc. gangue mineral mainly are skarns mineral（Garnet, pyroxene,Wollastonite） and quartz, including a bit of anhydrite, calcite, fluorite etc;④Improvingore-forming elements banding pattern in skarn: From the centre to middle of rock mass till topre-margin of skarn and marble contact zones. Mineral assemblage in skarn homologousore-forming elements zonation is Mo+Cu±Au±Ag→Cu±Mo±Au±Ag→Pb+Zn+Cu±Au±Ag±Mo→Au±Ag±Cu;⑤setting up zoning model of mineral assemblage and composition in skarn; as awhole, wollastonite skarn is rather independent relative to pyroxene skarn, it is mainly located inrock mass contact zones and middle-lower to marble contact zones on the vertical of centralsection. While garnet and pyroxene skarn located in rock mass contact zones→middle→remotezones front margin of skarn, Garnet/pyroxene＞10:1→about5:1→about2:1; Colour andcomposition of garnet is red-brown andradite（Ad＞80）→brown-yellow andradite（Ad50-80）→atrovirens-light yellow grossularite（Gr＞50）;⑥Dividing the alteration zoning of Jiamadeposit, rock plant includes elements mainly are K and Si. Above the hornfels appear argillizationzones-beresitization zones-propylitization zones that are located in nugget region, the transitionregion and the periphery;⑦Summing up three minerogenetic stages, among of them Gaswater-hydrothermal mineralization stage includes early stage skarn-silicate stage, late degradationaltered stage, quartz-copper sulfide stage, quartz-copper molybdenum sulfide stage, quartz-copperlead and zinc sulfide stage and quartz-gold-forming stages.3. A detailed geochemical study on the four ore body type which are classified at this time.On the one hand, a study was made on the formation of skarn and marble skarn duringmineralization process, garnet-based barren skarn, wollastonite-based non-ore skarnization,garnet-based ore skarn and mainly wollastonite-based skarn ore silicon in terms of major and traceelements and REE characteristics. An overall analysis of the geochemical behavior of elementsduring the alteration and mineralization process has been concluded to supporting the research onthe skarm mineralization process and reasons; on the other hand, the comparative study of thegeochemical characteristics has been made on the ZK4504other drillings which containing quartzdiorite porphyry and non-containing quartz diorite in the mining area. It is pointed out that the latehydrothermal gold mineralization was caused by external structure of the porphyry system,impacted by temperature and pressure control, but not closely related to the surrounding rock.4. The characteristics of sulfur magma source has been showed that sulfide in the major metalin the deposits and sulfur in the sulfate with a high degree of homogeneity, the value is near zero;isotopic composition of206Pb/204Pb, generally is18‰¹9‰;²⁰⁷Pb/²⁰⁴Pb is15.8‰to15.4‰;²⁰⁸Pb/²⁰⁴Pb is38.4‰to39‰, same as porphyry rock lead isotope compositions in the miningarea. The isotope composition of lead has the characteristic that is the orogenic belt andcrust-mantle mixing relating to magmatism. isotope show orogenic belt and magmatic activity andthe shell curtain mixed lead source characteristics the Pb isotopic composition between theYarlung Zangbo ophiolites and Himalayan gneiss and granite, and as same as the lead isotopecomposition in the magmatic rocks from Lhasa block; comparing the characteristics of ore siliconisotope composition from the different deposits formed differently, it is confirmed that the siliconisotope composition of Jiama skarn is as exactly same as mine magmatic, but is far away from thetypical spray jet rocks. hydrogen and oxygen isotope study confirmed that the fluids originated from magmatic-hydrothermal ore-forming system in the Jiama, with the participation ofatmospheric precipitation in its late period, with inclusions in salinity-temperature variationJiama the evolution of the ore-forming fluid model with different mineralization stages of fluid.5. The study on the deposit chronology, it is concluded that the mineralization age of Jiamadeposit is±16Ma and15Ma±. This important geological fact negates view of the genesis ofsedimentary mineralization in the late Jurassic to early Cretaceous jet, and supports theunderstanding of the porphyry-skarn mineralization.6. On the basis of the research of the deposit geology and the geochemical characteristics,this paper has made a analogy research between Jiama deposits at laboratory and comparing withtypical porphyry-skarn deposits abroad, to analyze their similarities and differences. Accordingly,it is believed that the magmatism offer metallogenic material for mineralization, structure offerpositioning space for ore body, and the lithology provides a good trap for the formation of the orebody. The coupling effect of the magma-Construction-lithologic traps formed a very largedeposit of Jiama, besides, it made a deposit ore-forming fluid lateral escape and metallogenicdynamics vertical escape mechanism, so as to point out the direction to find different types of orebodies at different spatial location and to establish a metallogenic model; On this basis, combiningwith the integrated exploration geophysical, geochemical exploration, and other information, arelatively new element of porphyry copper zoning prospecting model and the traditionalgeological-geophysical-geochemical prospecting model have been established. Moreover,combined with the practice in prospecting mining area peripheral, initially, the paper confirmedthe practicality of prospecting model.7. In short, through the " quaternity " prospecting model, the drilling up to350in more thanfour years, not only the skarn mineralization prospecting has been achieved, on the0line to40line, the copper-molybdenum ore body produced in the hornsfels has been found, also found indepth porphyry molybdenum （copper） ore body. So far, found out copper resources is more than6million tons, molybdenum resource of over600thousand tons, Pb and Zn resources is more than500thousand tons, associated gold over140tons, associated silver over8000tons, the equivalentcapacity copper resources of over15million tons. Jiama copper polymetallic has beenbreakthrough in the prospecting, and became the largest porphyry-skarn-type deposit, in Tibet.更多还原