西藏甲玛斑岩矿床系统黑云母标型特征及其地质意义

发布时间：2018-06-27 02:09

  本文选题：黑云母标型特征 + 角岩斑岩成矿　； 参考：《成都理工大学》2015年硕士论文

【摘要】：甲玛矿床位于西藏冈底斯成矿带东段,是公益性与商业性勘查结合取得的重要成果。目前铜资源量超过700万吨,共伴生钼、铅、锌、金、银资源量均达到大型以上规模。甲玛矿床是由斑岩钼铜矿体、矽卡岩铜多金属矿体、角岩铜钼矿体以及破碎带中独立金矿体构成的“四位一体”典型斑岩成矿系统产物。本文在充分收集整理矿区地质资料和前人研究成果的基础上,立足于矿区最新的勘查成果,通过详细的地质调查和钻孔地质编录等,采用岩、矿石光薄片显微鉴定、电子探针分析等系统研究矿区黑云母特征。详细厘定了甲玛铜多金属矿床的黑云母的成因类型,主要由两类黑云母组成,一类是原生黑云母,属于成矿前黑云母;另一类是岩浆-热液形成的热液黑云母,属于成矿期黑云母。岩体中的原生黑云母为岩浆黑云母,热液黑云母为热液交代黑云母和热液新生黑云母。角岩中原生黑云母为角岩化热变质过程中形成的黑云母,分为斑点状黑云母和条带状黑云母;热液黑云母:岩浆在热液分异过程中形成于角岩内部或裂隙中的热液黑云母,按照典型的共生矿物组合,可分为4类:A类:黑云母细脉;B类:石英+黑云母脉;C类:石英+黑云母+绿泥石脉;D类:石英+黑云母+钠长石脉。研究了两类黑云母的地球化学性状。原生黑云母和热液黑云母落于黑云母分类图中富镁黑云母和金云母区域,岩体中的黑云母偏向于富镁黑云母,具有富镁特征。角岩中,与原生黑云母相比,热液黑云母中Mg含量的升高,Cu含量升高,Fe含量降低,Fe2+和Fe3+分异程度增大;岩体中,与原生黑云母相比,热液黑云母具有Ti O23%,Al2O315%,低钛高铝的特征,Fe含量降低,Mg含量的升高,Cu含量升高。五类热液黑云母化学成分没有明显的差别,D类热液黑云母TFe O含量较其他热液黑云母较低,岩体中的热液黑云母TFe O含量较其他热液黑云母偏高。确定了2类黑云母形成的物理化学条件。花岗斑岩中原生黑云母的结晶温度变化在730~750℃,logf O2变化范围是-11.5~-13.0。花岗斑岩属于造山带钙碱性岩系,具壳幔混源的成因特点。与原生黑云母相比,角岩中热液黑云母Fe2+/(Fe2++Mg2+)比值均一程度低,且Fe3+/Fe2+比值相对含量显著升高,甚至部分热液黑云母不含Fe2+,指示岩浆-热液流体体系逐渐向氧化态过渡,有利于斑岩铜矿的形成。探讨了两类黑云母的形成与矿化的关系。相比原生黑云母,Cu更趋于富集于热液黑云母;而Mo元素在原生黑云母和热液黑云母中普遍存在,并不具有选择性赋存的特征。对于热液黑云母所在的岩矿石样品,矿化作用的强度与黑云母中Cu含量呈正相关。
[Abstract]:Jiama deposit is located in the eastern section of the Gangdis metallogenic belt in Tibet, which is an important result of the combination of public welfare and commercial exploration. At present, the amount of copper resources is more than 7 million tons, and the associated molybdenum, lead, zinc, gold and silver resources have reached large scale. Jiama deposit is a typical porphyry ore-forming system composed of porphyry molybdenum copper ore body, skarn copper polymetallic body, hornstone copper-molybdenum ore body and independent gold ore body in broken zone. On the basis of fully collecting and arranging geological data of mining area and previous research results, based on the latest exploration results of mining area, through detailed geological investigation and geological cataloguing of boreholes, this paper adopts microscopic identification of light and thin sections of rocks and ores. The characteristics of biotite in mining area were studied by electron probe analysis (EPMA). The genetic types of biotite in Jiama copper polymetallic deposit are determined in detail, which are mainly composed of two types of biotite, one is primary biotite, which belongs to pre-metallogenic biotite, and the other is hydrothermal biotite formed by magmatic hydrothermal solution. It belongs to biotite in metallogenic period. The primary biotite in the rock mass is magmatic biotite, hydrothermal biotite is hydrothermal metasomorphic biotite and hydrothermal neo-biotite. Proto-biotite in hornstone is biotite formed during hornstone thermal metamorphism, which is divided into spotted biotite and striped biotite; hydrothermal biotite: hydrothermal biotite formed in the interior or fissure of hornstone during hydrothermal differentiation. According to the typical symbiotic mineral assemblage, it can be divided into 4 groups: category A: biotite vein type B: quartz biotite vein type C: quartz biotite chlorite vein type D: quartz biotite albite vein. The geochemical properties of two classes of biotite were studied. The primary biotite and hydrothermal biotite fall in the magnesium-rich biotite and phlogopite area in the classification map of biotite. The biotite in the rock mass tends to be rich in magnesium-rich biotite and has the characteristics of magnesium-rich. In hornstone, compared with primary biotite, the increase of mg content in hydrothermal biotite and the increase of Cu content decrease the differentiation degree of Fe _ 2 and Fe _ 3, and in the rock mass, compared with that of primary biotite, the difference of Fe _ 2 and Fe _ 3 increases. Hot liquid biotite has TIO _ (23) and Al _ 2O _ 3 _ (15). The characteristic Fe content of low titanium and high aluminum content decreases the increase of mg content and the increase of Cu content. There is no obvious difference in the chemical composition of the five kinds of hydrothermal biotite. The TFeO content of D type hydrothermal biotite is lower than that of other hydrothermal biotite, and the TFeO content of hydrothermal biotite in rock mass is higher than that of other hydrothermal biotite. The physical and chemical conditions for the formation of two classes of biotite were determined. The crystallization temperature of protobiotite in granitic porphyry varies in the range of -11.5 ~ 13.0 at 750 鈩，

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