新疆东准噶尔绿源金矿床成因研究：流体包裹体及氢、氧同位素制约

东准噶尔绿源金矿是近年来新发现的矿床,位于野马泉-琼河坝古生代岛弧带东段的琼河坝矿集区。矿体主要产于上石炭统巴塔玛依内山组中酸性火山岩中,呈似层状、条带状、透镜状,多受断裂构造控制。流体成矿作用可分为4个阶段:石英-黄铁矿阶段、石英(玉髓)-金-黄铁矿阶段、石英-金-多金属硫化物阶段、石英-碳酸盐阶段,其中阶段2和阶段3为金主要成矿阶段。金属硫化物组合主要为黄铁矿-毒砂-闪锌矿-黄铜矿±银金矿组合。文章从流体包裹体和H、O同位素研究入手,对该矿床成矿流体和矿床成因进行探讨。流体包裹体岩相学特征显示,本矿床热液矿物中流体包裹体存在3种类型:富液相气液两相水溶液包裹体(V+L型)、富气相气液两相水溶液包裹体(V型)和纯液相水溶液包裹体(L型)。其中,V+L型包裹体数量最多,各阶段热液矿物中均有发育;V型包裹体数量最少;L型包裹体数量较少。显微测温结果显示:绿源金矿床石英中流体包裹体均一温度介于115~349℃之间,盐度集中于0.7%~8.8%NaCl eqv.之间,密度介于0.66~0.98g/cm~3之间;从阶段2至阶段4,流体均一温度从268~322℃,经181~300℃,降为115~176℃。这些都表明绿源金矿床成矿流体具有低温、低盐度、低密度的特征,与典型浅成低温热液型金矿成矿流体特征相似。对成矿压力和深度的估算表明,其成矿压力为(73~335)×10~5Pa(均值203×10~5Pa),成矿深度为0.24~1.12km(均值0.68km),显示出浅成热液矿床的特征。流体包裹体激光拉曼探针分析显示,各阶段包裹体成分类似,气相成分和液相成分主要为H_2O。成矿流体氢、氧同位素组成分别为δD_(H_2O)=-108.8‰~-129.0‰、δ~(18) O_(H_2O)=-7.2‰~4.6‰,表明成矿流体具有多来源,以大气降水为主的特征。综合矿床地质特征和成矿流体研究,认为流体不混溶作用可能是绿源金矿床的重要成矿机制,该矿床应属浅成低温热液型金矿床。     

Gold Grade and Tonnage Models of the Gold Deposits, China

Abstract: The gold grade and tonnage modelling is applied to some types of the gold deposits in China, including placer, Archaean lode, slate belt, Carlin, volcanogenic, skarn and Shandong Peninsula, among others. The Shandong Peninsula type denotes the gold deposit, which was formed in an intensely reshaped Archaean greenstone belt. The modelling results show: (1) the Archaean lode gold deposits of China are similar to the Homestake type in gold grades. (2) The Chinese slate belt type gold deposits are marked by moderately lower gold grades but considerably larger ore volumes than the similar type elsewhere. (3) The Carlin style gold deposits of China are identified by higher Au grades but evidently smaller sizes in comparison with their counterparts in western North America. (4) The volcanogenic (continental) style is similar to Sado epithermal veins in gold grade‐tonnage models and general characteristics while volcanogenic gold deposits of the oceanic subgroup contrast with Kuroko‐type deposits in the gold grade model. But the Chinese volcanogenic (oceanic) subtype (Palaeozoic age) shows similar higher gold grades to those of the Palaeozoic Kuroko‐type deposits elsewhere. (5) Porphyry and skarn gold deposits tend to have a large size but low grade. (6) Less than half of the Shandong Peninsula gold deposits are of ore volumes exceeding the 50th intercept of the relevant gold tonnage model, implying possible undiscovered gold deposits with a larger size in the peninsula. (7) In general, Chinese gold deposits of larger sizes tend to have lower gold grades in relation to gold grade models. (8) Gold grade‐tonnage models can be effectively influenced by how to include or exclude non‐economic gold resources in the modelling. Ore volumes of gold deposits actually to some extent depend on gold grades. Consequently, the way of including or excluding low‐grade values may effect a gold grade‐tonnage model and cause different interpretation of the modelling results. This is particularly true to the gold deposits, which generally show an inverse correlation between gold grade and tonnage.     

中低温开放含硫水热体系中水岩淋滤实验研究

针对湘中湘西矿区的地质实际在１００￣３００℃,２０ＭＰａ压力条件下,对中低温开放含硫水热体系地层岩石中Ｓｂ、Ａｓ、Ｈｇ的多元素进行了淋滤实验研究。实验结果表明,随温度的升高,Ｓｂ和Ｈｇ的淋滤率增大;低温富硫热液有利于Ｓｂ和Ａｓ的活化迁移。同时,水岩比值、岩性以及岩石中元素的存在形式也是控制元素活化能力的重要因素。     

Au–Ag–Te Mineralization of the Low‐Sulfidation Epithermal Aginskoe Deposit,Central Kamchatka,Russia

Mineralogic studies of major ore minerals and fluid inclusion analysis in gangue quartz were carried out for the for the two largest veins, the Aginskoe and Surprise, in the Late Miocene Aginskoe Au–Ag–Te deposit in central Kamchatka, Russia. The veins consist of quartz–adularia–calcite gangue, which are hosted by Late Miocene andesitic and basaltic rocks of the Alnei Formation. The major ore minerals in these veins are native gold, altaite, petzite, hessite, calaverite, sphalerite, and chalcopyrite. Minor and trace minerals are pyrite, galena, and acanthine. Primary gold occurs as free grains, inclusions in sulfides, and constituent in tellurides. Secondary gold is present in form of native mustard gold that usually occur in Fe‐hydroxides and accumulates on the decomposed primary Au‐bearing tellurides such as calaverite, krennerite, and sylvanite. K–Ar dating on vein adularia yielded age of mineralization 7.1–6.9 Ma. Mineralization of the deposit is divided into barren massive quartz (stage I), Au–Ag–Te mineralization occurring in quartz‐adularia‐clays banded ore (Stage II), intensive brecciation (Stage III), post‐ore coarse amethyst (Stage IV), carbonate (Stage V), and supergene stages (Stage VI). In the supergene stage various secondary minerals, including rare bilibinskite, bogdanovite, bessmertnovite metallic alloys, secondary gold, and various oxides, formed under intensely oxidized conditions. Despite heavy oxidation of the ores in the deposit, Te and S fugacities are estimated as Stage II tellurides precipitated at the log f Te₂ values ?9 and at log fS₂ ?13 based on the chemical compositions of hypogene tellurides and sphalerite. Homogenization temperature of fluid inclusions in quartz broadly ranges from 200 to 300°C. Ore texture, fluid inclusions, gangue, and vein mineral assemblages indicate that the Aginskoe deposit is a low‐sulfidation (quartz–adularia–sericite) vein system.     

浅成低温热液金矿研究现状及其趋势

浅成低温热液金矿指产于陆相火山岩系中或相邻岩石中，形成温度低于３００℃，成矿流体是大气降水与岩浆热液形成的混合热液的一类金矿床。近几年对浅成低温热液金矿研究结果突破了浅成低温热液金矿只形成于中一新生代火山岩系中的概念，在石炭纪陆相火山岩中发现了浅成低温热液金矿。浅成低温热液矿床一般产于岛弧环境或大陆边缘环境中一酸性陆相火山夺系及相邻岩石中。根据矿物组合及蚀变特征，浅成低温热液矿床可分为高硫型、低硫     

冀北丰宁银(金)矿床地质、地球化学特征及成因

冀北丰宁银(金)矿床的成矿深度＜1 km,成矿温度＜300℃,成矿时间晚于次火山隐爆成岩作用1.0 Ma以上,是与隐爆作用有关的陆相次火山浅成低温热液型银多金属矿床.次火山隐爆作用只是一种构造动力因素,起到动力源和提供扩容空间的间接成矿作用,而直接的成矿环境为浅成低温水热流体的成矿演化体系.热液流体大致可分为两类:一是富含SiO2的热流体,存在于每次隐爆作用之中,起到胶结花岗质角砾的作用,并有少量金属硫化物(如黄铁矿等)沉淀;二是有大量地下水参与的含矿水热流体,形成于隐爆作用发生之后,此阶段的热液活动导致Au,Ag,Pb,Zn,Fe,Cu等金属及其化合物的富集与沉淀.     

新疆鄯善县石英滩金矿床地质特征及控矿因素

通过对石英滩金矿床区域地质背景、矿体产出形态、矿石特征、成矿控制因素的研究，认为矿床成因类型应属浅成低温火山热液型金矿床。     

西天山吐拉苏-也里莫墩金成矿带简述

吐拉苏一也里莫墩矿带是西天山地区重要金矿成矿区.矿带内金矿赋存于晚古生代中期拉张(裂谷)环境下形成的早石炭世火山岩带内,金矿围岩为下石炭统大哈拉军山组陆相火山岩,成矿时代为早石炭世杜内-韦宪早期.矿带内金矿化可分为浅成低温热液系统(冰长石-绢云母型、硅化岩型)、斑岩型和沉积砾岩型.矿带内东、西两段控矿构造有差异:西部吐拉苏地区的阿希、京希开布拉克、伊尔曼得等金矿产于京希一阿希近南北向火山构造拗陷带内的火山机构构造系统(冰长石-绢云母型)和层间裂隙带(硅化岩型)中;东部也里莫墩地区的加特曼、铁列克特、小于赞等金矿床(点)产于吾拉斯台-郎布拉近东西向火山构造隆起带内的次火山穹丘构造系统中.     

高硫-低硫化浅成低温热液矿床的短波红外矿物分布特征及找矿模型——以西藏铁格隆南(荣那矿段)、斯弄多矿床为例

本文以铁格隆南(荣那矿段)高硫化浅成低温热液矿床和斯弄多低硫化浅成低温热液矿床为研究对象,运用短波红外技术快速厘定了上述两个矿床的蚀变矿物类型及组合特征,构建了基于短波红外勘查技术的找矿模型.研究发现:铁格隆南矿床(荣那矿段)的蚀变矿物垂向分带组合为:高岭石→高岭石+(地开石+明矾石)→高岭石+明矾石+(地开石)→高岭石+地开石+明矾石.由于高硫化浅成低温热液交代黄铁绢英岩化带的斑岩型矿体,致使上部矿石中还有少量交代残余的绢云母;斯弄多低硫化浅成低温热液矿床的蚀变矿物垂向分布为:白(绢)云母+(钠云母)→白(绢)云母+钠云母+(伊利石)→白(绢)云母+钠云母+蒙脱石+伊利石→白(绢)云母+钠白云母+蒙脱石+伊利石,其中顶部白(绢)云母是后期黑云母花岗斑岩蚀变所产生,本身与成矿无关;矿体主要赋存在伊利石+蒙脱石带,随着蒙脱石被伊利石化,矿体也逐渐尖灭.     

贵州低温热液型汞、锑、金矿床成矿谱系——以晴隆大厂、兴仁紫木凼和铜仁乱岩塘为例

贵州是我国低温热液型汞、锑、金矿的重要产区,但对其成矿时代一直存在不同看法.本次研究采用Sm-Nd同位素等时线法对晴隆大厂锑矿、兴仁紫木凼金矿和铜仁乱岩塘汞矿区的萤石、方解石分别进行了同位素年代学的研究,结果表明晴隆大厂锑矿中的方解石(Sm-Nd等时线年龄为148±13 Ma,钕初始值为0.512256)和萤石(Sm-Nd等时线年龄为142.3±7.9 Ma,钕初始值为0.512151)形成于晚侏罗世;紫木凼金矿中方解石(Sm-Nd等时线年龄为250±14 Ma,钕初始值为0.511909)形成于晚二叠世与早三叠世的过渡期;乱岩塘汞矿中的方解石(Sm-Nd等时线年龄为364±24 Ma,钕初始值为0.511517)则形成于晚泥盆世.结合前人其他资料,本文认为贵州的汞、锑、金矿床不是在燕山期一个时间段形成的,而是经历了从加里东期、海西-印支期到燕山早期和燕山晚期的复杂过程,从而形成了一个演化历史悠久的低温热液型成矿谱系.