四川雪宝顶钨锡铍矿床包裹体研究及其意义

发布时间：2018-06-25 14:03

  本文选题：钨锡铍矿床 + 成矿流体　； 参考：《成都理工大学》2015年硕士论文

【摘要】：雪宝顶钨锡铍矿床位于四川省平武县境内,是松潘-甘孜造山带和秦岭造山带内迄今发现的唯一的钨锡铍矿床。本文在前人研究的基础上,结合矿床地质特征,对流体包裹体进行了岩相学观察、显微测温、激光拉曼光谱分析及热力学计算等研究,对雪宝顶矿床成矿流体的性质、来源和成矿机理取得以下认识：中三叠统杂谷脑组(T2z1)下段为主要的赋矿地层,部分矿体产出于花岗岩体中及其围岩接触带中,矿体以脉状、网脉状产出,矿石矿物主要为绿柱石、白钨矿、锡石及少量的电气石、黄铜矿、黄铁矿、方铅矿、闪锌矿等。脉石矿物为石英、白云母、钾长石、萤石、钠长石、磷灰石等。矿石具有脉状构造、网脉状构造、块状构造和晶簇状构造,自形晶结构、伟晶结构、内部环带结构。矿床中发育的包裹体可分为三大类,为熔融包裹体、流体-熔融包裹体、流体包裹体,其中,流体包裹体又可分为气相H20包裹体、气液H2O包裹体,气相CO2包裹体、气液C02包裹体、富CO2相CO2-H2O包裹体、富H20相CO2-H2O包裹体六类,显示出成矿流体由岩浆演化分异而来的特征,流体包裹体组合则显示出不混溶的特征。本矿床气液H20包裹体的均一温度为167～255℃,盐度w(NaCl)为3.39%～6.59%,密度介于0.8g/cm3～1.0g/cm3之间。富CO2相CO2-H2O包裹体,均一温度范围234℃～267℃,平均值为250℃；均一压力范围124MPa～ 171MPa,平均值为153MPa；密度值变化范围是0.6781 g/cm3～0.7618g/cm3, CO2的摩尔分数变化范围为0.6349-0.7407。富H2O相CO2-H2O包裹体的完全均一温度范围是224℃～286℃,平均值为251℃；完全均一压力范围是122MPa～ 155MPa,平均值为144MPa；密度变化范围是0.9342g/cm3～0.9655g/cm3, CO2的摩尔分数变化范围为0.0962-0.1123。两种类型CO2-H2O包裹体的温压一致,它们是同时捕获的C02-低盐水相不混溶包裹体组。成矿流体具有低盐度、中高密度、富C02的性质。气液H20包裹体和气液C02包裹体联合求压法计算得到绿柱石形成温度为318℃,形成压力为147MPa；白钨矿形成温度为296℃,形成压力为101MPa。矿床的形成深度约为8.29Km～10.11Km,为高中温深成矿床。三叠纪扬子板块与华北板块发生碰撞事件,本区发生了强烈的构造岩浆活动,花岗岩浆在冷凝结晶过程中分异出的成矿流体向花岗岩体外部流动,当进入节理裂隙发育的花岗岩岩体与围岩(大理岩)的接触带时,由于压力的降低,发生CO2-H2O流体不混溶作用,导致矿质大量沉淀,这是本矿床的主要成因。
[Abstract]:Xuebao Ding tungsten tin beryllium deposit located in Pingwu County Sichuan Province is the only tungsten tin beryllium deposit found in Songpan-Ganzi orogenic belt and Qinling orogenic belt. On the basis of previous studies and combined with the geological characteristics of the deposit, the petrographic observation, micro-temperature measurement, laser Raman spectroscopy analysis and thermodynamic calculation of fluid inclusions are carried out in this paper to study the ore-forming fluid properties of Xuebao Ding deposit. The source and metallogenic mechanism are as follows: the lower part of the Middle Triassic Zagunao formation (T2z1) is the main ore-bearing strata, some orebodies occur in the granite body and its surrounding rock contact zone, and the orebodies are vein-like and net-vein. Ore minerals are mainly Beryl, scheelite, cassiterite and a small amount of tourmaline, chalcopyrite, pyrite, galena, sphalerite and so on. Gangue minerals are quartz, Muscovite, potassium feldspar, fluorite, albite, apatite, etc. The ore has vein structure, net vein structure, block structure and cluster structure, self-shaped crystal structure, pegmatite structure and inner ring structure. The inclusions developed in the deposit can be divided into three categories: melt inclusions, fluid-melt inclusions, fluid inclusions. Among them, fluid inclusions can be divided into gas-phase H20 inclusions, gas-liquid H2O inclusions, gas-phase CO2 inclusions. The gas-liquid CO2 inclusions, CO2 rich CO2-H2O inclusions and H20-rich CO2-H2O inclusions show that the ore-forming fluids come from the evolution of magma, while the fluid inclusions assemblage shows the characteristics of immiscibility. The homogenization temperature of gas-liquid H20 inclusions in the deposit is 167 ~ 255 鈩，

本文编号：2066243