【作者】 王焕；

【导师】 唐菊兴；

【作者基本信息】 中国地质科学院 ， 矿产普查与勘探， 2011， 硕士

【摘要】 西藏甲玛铜多金属矿床是冈底斯成矿带上最典型、独特的斑岩-矽卡岩型铜多金属矿床,其铜、钼、铅锌及伴生金、银资源量均已达大型-超大型规模。因此,开展详细的矿石学、矿物学研究不仅对于甲玛矿床,甚至对冈底斯这一具世界级规模的铜、铅、锌、铁、金、银等多金属成矿带上类似矿床的研究意义重大。本文在充分收集整理、分析总结前人资料和研究成果的基础上,立足于大量的野外工作,通过3万米的岩矿心地质编录,1000张野外照片,253件光薄片鉴定,500点电子探针分析及10件单矿物测试,取得了如下进展和创新：划分了矿体类型,基本查明了矿石组构和矿石物质组成。矿床主要由产于矽卡岩中的铜钼铅锌金银多金属矿体、产于角岩中的钼(铜)多金属矿体及产于深部隐伏斑岩中的铝(铜)矿体组成。矿石构造主要为岩浆热液形成的矿石构造,包括浸染状构造、块状构造、细脉-网脉状构造等；矿石结构主要为交代结构、结晶结构、固溶体分离结构等。矿床中矿物种类约60种,鉴定出金属矿物包括斑铜矿、黄铜矿、辉钼矿、黝铜矿、方铅矿、闪锌矿、辉铜矿、蓝辉铜矿、铜蓝、蓝铜矿、孔雀石、自然金、自然银及硫盐矿物等,非金属矿物主要为石榴子石(钙铁榴石、钙铝榴石)、硅灰石、透辉石、透闪石、绿帘石等矽卡岩矿物,其次为石英、长石、方解石、黑云母、绢云母、绿泥石、硬石膏、萤石、高岭石等。矿床形成经过岩浆期、矽卡岩期、热液期和表生期四个成矿期次,其中热液期又分为铜钼硫化物阶段、铜硫化物-硫盐矿物阶段、铜铅锌硫化物阶段及金成矿阶段等四个成矿阶段,每个成矿阶段典型矿物组合特征具有明显的从高温组合到低温组合的趋势。查明了矿物类型及成分特征。矽卡岩矿物为一套钙铁榴石-钙铝榴石-透辉石-硅灰石组合,属于典型的钙矽卡岩组合,形成温度为450℃-700℃的高温条件。金属矿物中发育斑铜矿-黄铜矿、斑铜矿-辉铜矿、斑铜矿-硫铋铜矿等互为主客晶的乳滴状、格子状、叶片状固溶体分离结构,这些含铜矿物形成的固溶体分离结构指示成矿温度主要为中-高温(475℃-225℃)。上述温度条件表明,矿床形成并非热水喷流沉积所能形成,而是与岩浆作用有不可或缺的成因联系。石榴子石、透辉石、硅灰石、斑铜矿、黄铜矿、辉钼矿等矿物的电子探针分析表明：石榴子石暗色带相对于浅色带普遍具有SiO2、TiO2、Al2O3含量偏低,而TFeO含量偏高的成分变化特点,且暗色带Mn、Ti含量高于浅色带,反映了石榴子石在形成过程中物理化学环境有所改变；矿床中辉石类型主要为透辉石,其Mn/Fe比值除2个较高(1.18和0.80)外,其余变化范围为0.17～0.50,指示甲玛矿床矿化类型属于多金属矿床；斑铜矿颜色的差异是由固溶体析出成分的不同、Fe含量的高低及斑铜矿形成温度高低所致,Fe含量由低-高变化过程中斑铜矿反射色显示出蓝紫色-锖紫色-棕红色的变化趋势；花岗斑岩中产出的黄铜矿其Ag和Zn含量普遍高于产在角岩和矽卡岩中黄铜矿Ag和Zn的含量,而角岩中黄铜矿Au的含量略高于矽卡岩和花岗斑岩中黄铜矿的Au含量。论文通过对前人氢-氧、硫、铅同位素分析资料的综合整理,分析了成矿流体和成矿物质的来源,结合项目组对于矿床成矿时代、成矿流体演化等方面的相关研究,对甲玛矿床成因进行了较为深入的阐述,认为矿床形成与中新世浅成岩浆作用有关,矿床类型为斑岩-矽卡岩型。更多还原

【Abstract】 Jiama copper polymetallic deposit is a typical and unique porphyry-skarn type ore deposit in the Gangdise metallogenic belt of Tibet. The ore reserves of copper, molybdenum, lead and zinc and associated gold and silver have already reached large and super-large scale. Therefore, to carry out detailed research on the ore mineralogy and mineralogy, not only has an important significance to Jiama deposit, but also to those mineral deposits in Gangdise polymetallic metallogenic belt which have world-class scale of copper, lead, zinc, iron, gold and silver. After fully collecting, analyzing and summing the formers’ data and research results, moreover, lots of field work were completed, containing 30 thousand meters core geological logging,1000 pieces of field photos, appraisal of 253 pieces of polished section of the ore, electron microprobe analysis of 500 points, and testing of 10 pieces of single minerals, this paper has got some progress following.The types of ore-bodies have been classified and ore fabrics and component of ore mineral have been ascertained. The Jiama copper polymetallic deposit are mainly consisted of skarn-type Cu-Mo-Pb-Zn-Au-Ag polymetallic ore-body, hornfels-type Mo (Cu) polymetallic orebody and deeply buried porphyry-type molybdenum (copper) ore-body. The ores are dominated by ore structures produced by magmatic hydrothermal, including disseminated structure, massive structure, veinlets-stockwork structure; the ore textures are mainly metasomatic texture, crystalline texture, solid-solution separation texture, and so on. There are about 60 kinds of metallic minerals in the deposit, mainly containing bornite, chalcopyrite, molybdenite, tetrahedrite, galena, sphalerite, chalcocite, alpha chalcocite, covellite, azurite, malachite, natural gold, natural silver and sulfosalt minerals; non-metallic minerals including mainly garnet (andradite, grossular), wollastonite, diopside, tremolite, epidote and other skarn minerals, subordinately quartz, feldspar, calcite, biotite, sericite, chlorite, anhydrite, fluorite, kaolinite. This mineral deposit has experienced four mineralization periods of magmatic stage, skarn stage, hydrothermal stage and supergene stage, in which the hydrothermal stage can be divided into Cu-Mo sulfide phase, copper sulfide-sulphosalts mineral phase, Cu-Pb-Zn sulfide phase and gold mineralization phase, and the typical mineral assemblages in each mineralization phase have the obvious trend features of varying from high temperature to low temperature.The types of minerals and composition characteristics have been ascertained, also. In this ore deposit, the skarn minerals are a set of andradite-grossular-diopside-wollastonite assemblage, belonging to typical calcium skarn combination and forming in the medium-high temperature conditions of 450℃-700℃. The emulsion-like, lattice-like and leaf-shaped solid-solution separation textures are widely developed in the ores of this mineral deposit, in which bornite-chalcopyrite, bornite-chalcocite and bornite-wittichenite served as host and guest crystals each other. And the solid-solution separation textures formed by the copper-bearing minerals mentioned above have indicated that, the mineralization temperature are mainly medium-high temperature conditions(475℃-225℃). And the temperature mentioned above has suggested that, this ore deposit is not formed by hydrothermal sedimentary exhalative processes, but has indispensable genetic relationship with magmatism.Through systematic electron microprobe analyses on garnet, pyroxene, wollastonite, bornite, chalcopyrite, molybdenite and so on, this paper has made some conclusion. First, comparing with light zonation in garnets, the contents of SiO2, TiO2, Al2O3 are lower in dark zonation, while the contents of TFeO, Mn, Ti are higher. All of these phenomenon showed that the physic-chemical condition had been changed during the crystallization of garnets. Second, diopsides in Jiama ore pyroxene are mainly diopside and their ratios of Mn/Fe mainly varied from 0.17～0.50 except two tested points (with the ratios of 1.18 and 0.80). The characteristics of ratios of Mn/Fe have shown Jiama ore deposit was a typical polymetallic deposit. The color difference of bornite is caused by precipitation of solid-solution composition, Fe content and different formation temperature, and changes from the low content of to high content of Fe induced reflected colors varying from blue-purple to purple to brown red. Third, contents of Ag and zn in chalcopyrites occurred in granite-porphyry were higher than chalcopyrites occurred in hornfels and skarn. Whereas the content of Au in chalcopyrites occurred in hornfels was higher than those occurred in granite-porhpyry and skarn.The sources of ore-forming fluids and mineralization materials have been fully analyzed by comprehensivly summing up the formers’ analytical data about H-O-S-Pb isotopes. Through combining with the related researches about the mineralization age and the evolution of ore-forming fluids and so on which have been carried out by the project team, the genesis of Jiama ore deposit has been discussed deeply, and it is found that the formation of this ore deposit was closely related with miocene magmatism, and the genetic type of Jiama ore deposit belongs to porphyry-skarn type.更多还原