Ore‐forming Ages and Sulfur Isotope Study of Hydrothermal Deposits in Kamchatka,Russia

In Kamchatka, Central Koryak, Central Kamchatka and East Kamchatka metallogenic belts are distributed from northwest to southeast. K–Ar age, sulfur isotopic composition of sulfide minerals, and bulk chemical compositions of ores were analyzed for 13 ore deposits including hydrothermal gold‐silver and base metal, in order to elucidate the geological time periods of ore formation, relationship to regional volcanic belts, type of mineralization, and origin of sulfur in sulfides. The dating yielded ore‐forming ages of 41 Ma for the Ametistovoe deposit in the Central Koryak, 17.1 Ma for the Zolotoe deposit and 6.9 Ma for the Aginskoe deposit in the Central Kamchatka, and 7.4 Ma for the Porozhistoe deposit and 5.1 Ma for the Vilyuchinskoe deposit in the East Kamchatka metallogenic belt. The data combined with previous data of ore‐forming ages indicate that the time periods of ore formation in these metallogenic belts become young towards the southeast. The averaged δ³⁴S_CDT of sulfides are ?2.8‰ for the Ametistovoe deposit in Central Koryak, ?1.8‰ to +2.0‰ (av. ?0.1‰) for the Zolotoe, Aginskoe, Baranievskoe and Ozernovskoe deposits in Central Kamchatka, and ?0.7 to +3.8‰ (av. +1.7‰) for Bolshe‐Bannoe, Kumroch, Vilyuchinskoe, Bystrinskoe, Asachinskoe, Rodnikovoe, and Mutnovskoe deposits in East Kamchatka. The negative δ³⁴S_CDT value from the Ametistovoe deposit in Central Koryak is ascribed to the contamination of ³²S‐enriched sedimentary sulfur in the Ukelayat‐Lesnaya River trough of basement rock. Comparison of the sulfur isotope compositions of the mineral deposits shows similarity between the Central Koryak and Magadan metallogenic belts, and East Kamchatka and Kuril Islands belts. The Central Kamchatka belt is intermediate between these two groups in term of sulfur isotopic composition.     

Metal contents of recent thermal waters, mineral precipitates and hydrothermal alteration in active geothermal fields, Kamchatka

All the Kamchatkan recent hydrothermal systems are restricted to two volcanic zones, Central Kamchatka of Late Miocene-Pliocene age and East Kamchatka, where several active volcanoes are located. Solutions from active hydrothermal systems commonly contain elements, including As, Sb, Hg, Li, Rb, Cs, B, Cu, Pb, Zn, Ag, Au,Sr and Ba, with the first seven predominating. Higher abundances of ore elements occur in active hydrothermal systems with solutions of sodium chloride composition. Those are the Kireunskaya, Dvukhyurtochnaya and Apapelskaya systems in the Central Kamchatka volcanic zone and the Uzon hydrothermal system in the East Kamchatka volcanic zone. The hydrothermal systems are restricted to structures having very long histories of evolution and which are characterized by contrasting types of magmatism. At present chemical precipitates and altered rocks with higher abundances of As, Sb and trace amounts of Au, Ag, Cu, Ph and Zn are forming in the discharge zones of these hydrothermal systems. Large zones of alterations (alunitic quartzites^* and argillites) with high abundances of As, Sb, Hg, Cu, Pb, Ga and Zr occur in the Central Kamchatka volcanic zone. Here zones of mineralization (cinnabar, realgar, stibnite, orpiment, pyrite, chalcopyrite, sphalerite, galena) occur also; native gold, native silver and gudmundite occur rarely.In the recent Uzon caldera hydrothermal system, As-Sb-Hg mineralization with bitumen and oils is now forming. The ore deposit is zoned, with the most abundant ore minerals being realgar, uzonite, alacranite, stibnite and pyrite. Cinnabar, orpiment, marcasite and native mercury occur occasionally, and single grains of native gold, native silver and native copper are present. At present a total of 7000 t As, 350 t Sb and 200 t Hg have been deposited in the mineralization zone at geochemical boundaries. The general geological and geochemical data suggest that at depth the As-Sb-Hg mineralization may change to gold-silver mineralization.     

金厂峪金矿床围岩蚀变特征与矿床成因

为了更深入地理解金厂峪金矿床成矿作用,对该金矿床内蚀变围岩的矿物组合、成分及其变化进行了较详细的研究.蚀变带质量平衡分析表明Al₂O₃、MnO、P₂O₅等组分具不活动性.由蚀变围岩向钠长石英脉,在蚀变岩中元素无明显变化.钠长石英脉体的形成与围岩蚀变有关,但两者成因并不相同.金厂峪金矿床的形成可能与深源流体有关     

电子探针在蚀变矿物晕研究中的应用

本文选择3种成因的微晶岩石,用电子探针直接在光薄片上进行常规全岩成分分析的实验,并将实验结果与化学分析结果作对比,说明用电子探针粗束斑缓慢移动样品和用细束斑面积扫描两种方法,对某些岩石进行化学成分分析的可行性。作者还采用上述方法,对湘西沃溪Au-Sb-W矿床蚀变矿物晕进行矿物—地球化学微剖面研究,揭示了有关热液矿床围岩蚀变作用过程中元素迁移的规律、岩石退色的机理,提供了矿床成因的信息。     

福建永泰无岩坑钼矿地质特征及成因探讨

永泰无岩坑钼矿体贮存于成矿母岩燕山晚期中粗粒含黑云母花岗岩边缘相细晶质花岗岩硅化褪色蚀变带中,储矿构造主要为花岗岩岩体顶部的内接触带即岩凸构造,以及区域性北西向断裂的次级裂隙。矿床成因属岩浆期后热液充填型。     

辽宁省本溪县杨家堡子金矿地质特征及成因浅析

本溪县杨家堡子金矿赋存于早古生代奥陶系马家沟组及寒武系凤山组内,矿体主要围岩为变质程度轻微的碎屑沉积岩及碳酸盐岩,矿体受断裂构造控制,金矿物及载金矿物——黄(褐)铁矿均呈稀疏浸染状分布,金成矿与燕山期二长花岗岩关系密切,具有"卡林型"金矿床地质特征。认为杨家堡子金矿是与早古生代寒武系、奥陶系地层、岩性、岩相(变质相)、断裂构造及燕山期岩浆活动有成因联系的金矿床,对矿体的矿物组合进行分析,初步确定矿化成因应属低温热液型金矿床。     

甘肃西成铅锌矿田控矿相模式雏议

控矿相是控制矿床形成的沉积相,控矿相可以是单独的一个相,或者是相的组合。西成铅锌矿的控矿相就是一种相的组合。本文除概略介绍控矿相、控矿相组合的特点、分类和分布外,还模拟了一个西成铅锌矿田控矿相的综合模式,供讨论和参考。不妥之处,敬希指正。     

粤北大沟谷式金矿地质特征及成因探讨

大沟谷金矿是我国首次发现的赋存于韧-脆性剪切带内碎裂钠长石岩中的新类型金矿床。金矿化与钠长石化、黄铁矿化和碎裂岩化有关。矿体受韧-脆性剪切带、钠长石比、黄铁矿化,加里东期低绿片岩相变质岩的共同控制。矿石矿物组合以自然金-金属硫化物-架状硅酸盐为主的组合类型,并伴有碳酸盐。矿床属于在韧一脆性剪切作用下,与含金量较高的震旦系乐昌峡群变质岩形成、演化有成因联系的蚀变、重熔、交代中高温动力热液改造型金矿床。     

Mineralogical Zonation of Wall-Rock Alteration in Jiaodong Gold Province, North China

ＭＩＮＩＮＧＨＩＳＴＯＲＹＧｅｏｇｒａｐｈｉｃａｌｙｔｈｅＪｉａｏｄｏｎｇｇｏｌｄｐｒｏｖｉｎｃｅｃｏｖｅｒｓａｌｍｏｓｔｔｈｅｗｈｏｌｅＳｈａｎｄｏｎｇｏｒＪｉａｏｄｏｎｇＰｅｎｉｎｓｕｌａ,ｔｈｅｅａｓｔｅｒｎｈａｌｆｏｆｔｈｅＳｈａｎｄｏｎｇＰ...     

相山矿田沙洲铀矿床围岩蚀变地球化学特征

江西相山铀矿田沙洲铀矿床的矿体严格受断裂控制,围岩蚀变分带非常明显。对沙洲铀矿床围岩蚀变的地球化学特征进行的研究表明,沙洲矿床从矿石到围岩的化学成分具有明显的变化,这些化学成分的变化与蚀变过程中物质的带入带出是密切相关的。通过对全部样品进行R型聚类分析,确定矿床成矿元素组合为U、W、HREE、Th、Zn、Zr、Mo、Pb,这些元素可作为铀成矿预测标志。研究成果在一定程度上充实和丰富了沙洲铀矿床的成因认识。      

Application of Chlorite Geothermometry to Hydrothermal Alteration in Toyoha Geothermal System, Southwestern Hokkaido, Japan

In this study, we applied chemical geothermometers to the estimation of formation temperatures of chlorites from various types of hydrothermally altered rocks in the Toyoha geothermal field, using core samples from six drill holes (TH-2 to TH-7) together with wasted ore samples from Toyoha vein-type ore deposit. Based on the preliminary examination of mineral assemblages by X-ray powder diffraction and optical microscopy, hydrothermal alteration observed through the drill holes was classified into four types of alteration zones: propylitic, mixed-layer minerals, kaolin minerals, and ore mineralized zones. The mineral assemblage of the ore mineralized zone observed through TH-2, TH-4, and TH-6 is similar to those of Toyoha ore veins reported previously. The Fe³⁺/ΣFe ratios of chlorites were determined by X-ray photoelectron spectroscopy (XPS), in addition to the usual microprobe analyses. The ratios ranged from 0.20–0.26 for chlorites from the propylitic alteration zone and from 0.13 to 0.17 for those from the ore mineralized zone associated with sulfide minerals. After correcting the Fe³⁺ contents in the octahedral sites of chlorite structures, we obtained acceptable temperatures of the chlorite formation by application of geothermometers, for instance, a similar range of 150–300°C for chlorites from either the propylitic zone or the ore mineralized zone developed through TH-2, TH-4, and TH-6. Chlorites from the ore mineralized zone proximal to the Toyoha deposit are characterized by high Fe and Mn contents compared to the propylitic chlorites, which is similar to the Toyoha vein-filling chlorites; the formation temperatures were close to both the homogenization temperatures of fluid inclusions and the present subsurface temperatures measured through drill holes. Chlorites from the Toyoha ore veins, however, gave slightly higher formation temperatures (180–350°C) than those of chlorites from the ore mineralized zone in the drill cores. This suggests that several types of hydrothermal alteration occurred at different stages in the Toyoha geothermal field and the composition of product chlorite was controlled not only by the temperature but also the composition of fluid related to the formation. Reliable estimation of temperature for the chlorite formation provides basic information on evaluating correctly other physicochemical conditions prevalent at the formation.     

南沙群岛“危险地带”腹地珊瑚礁的地貌与现代沉积特征

南沙群岛中央水道及南华水道两侧的珊瑚礁,大部分为环礁,分属开放型、半开放型、准封闭型、封闭型和台礁化型,反映了环礁向灰砂岛演变的不同阶段。每个环礁,从礁前斜坡向礁坪至潟湖,可相应划分出3种沉积相和细分9种沉积带。礁顶是全新世中期以来形成发育的。     

矿物成因族的演化及其地质找矿信息

基于对胶东、晋北寒武纪变质岩系、超基性岩、基性岩、花岗岩类、火山岩类、硅铁建造铁矿、金矿蚀变带内 1 1个不同地质产状的 34个角闪石、 2 51个绿泥石、 60个黑云母单矿物的提纯 ,矿物的共生组合、物理性质、化学成分、X光衍射分析、热分析、红外吸收光谱分析、双矿物地质温度计、矿物压力计的测定 ,提出了角闪石、绿泥石、黑云母矿物成因族的地壳物质演化、成岩成矿作用、变质岩原岩恢复、地层对比、变质相、蚀变带的演化规律和地质找矿信息。     

略阳地区泥盆纪地层中3T型多硅白云母的成因机理及找矿意义

3T型多硅白云母是白云母的一个变种。它不但是变质相带中的标型矿物,也是特球构造和板块消亡带的特征矿物。略阳地区泥盆系中3T型多硅白云母的发现在我省属于首次。该矿物发现于略阳县的西部,产于泥盆纪地层中金矿体内。金矿赋存于蚀变细碧岩中,共生矿物有石英、白云石、绿泥石、铁方解石、黄铁矿等。矿体含金品位增高时,3T型多硅白云母含量同步增长,而且地层扭动也随之强烈。本文对3T型多硅白云母产生的地质环境、矿物学特征,形成机理以及与构造运动、板块活动的关系等方面进行了初步探讨。     

The early Cambrian Chahmir shale-hosted Zn–Pb deposit,Central Iran: an example of vent-proximal SEDEX mineralization

The Chahmir zinc–lead deposit (1.5 Mt @ 6 % Zn + 2 % Pb) in Central Iran is one among several sedimentary-exhalative Zn–Pb deposits in the Early Cambrian Zarigan–Chahmir basin (e.g., Koushk, Darreh-Dehu, and Zarigan). The deposit is hosted by carbonaceous, fine-grained black siltstones, and shales interlayered with volcaniclastic sandstone beds. It corresponds to the upper part of the Early Cambrian volcano-sedimentary sequence (ECVSS), which was deposited on the Posht-e-Badam Block during back-arc rifting of the continental margin of Central Iran. Based on crosscutting relationships, mineralogy, and texture of sulfide mineralization, four different facies can be distinguished: stockwork (feeder zone), massive ore, bedded ore, and distal facies (exhalites with barite). Silicification, carbonatization, sericitization, and chloritization are the main wall-rock alteration styles; alteration intensity increases toward the proximal feeder zone. Fluid inclusion microthermometry was carried out on quartz associated with sulfides of the massive ore. Homogenization temperatures are in the range of 170–226 °C, and salinity is around 9 wt% NaCl eq. The size distribution of pyrite framboids of the bedded ore facies suggests anoxic to locally suboxic event for the host basin. δ³⁴S_(V-CDT) values of pyrite, sphalerite, and galena range from +10.9 to +29.8?‰. The highest δ³⁴S values correspond to the bedded ore (+28.6 to +29.8?‰), and the lowest to the massive ore (+10.9 to +14.7?‰) and the feeder zone (+11.3 and +12.1?‰). The overall range of δ³⁴S is consistent with a sedimentary environment where sulfide sulfur was derived from two sources. One of them was corresponding to early ore-stage sulfides in bedded ore and distal facies, consistent with bacterial reduction from coeval seawater sulfate in a closed or semiclosed basin. However, the δ³⁴S values of late ore-stage sulfides, observed mainly in massive ore, interpreted as a hydrothermal sulfur component, leached from the lower part of the ECVSS. Sulfur isotopes, along with the sedimentological, textural, mineralogical, fluid inclusion, and geochemical characteristics of the Chahmir deposit are in agreement with a vent-proximal (Selwyn type) SEDEX ore deposit model.     

桃江锰矿锰帽形成的地球化学过程

桃江锰矿区发育有较完整的表生氧化剖面,根据不同深度矿石的结构构造,矿物组合及化学成分特征,将表生氧化剖面分成三个带：氧化矿石带,地渡矿石带和原生矿石带。桃江锰矿原生矿石矿物主要为含锰碳酸盐,表生富集作用包括两上地球化学过程;可溶杂质的溶解淋失作用和锰质的氧化残留作用。在过渡矿石带中,可溶性杂质发生大规模溶解迁移,锰质发生相对富集;氧化矿石带中,碳酸锰氧化成难溶的高价锰的氧化物,使锰质残留下来,形成     

峨眉山玄武岩与玄武岩铜矿成矿研究

峨眉山玄武岩在康滇地轴东缘(四川、云南、黔西)广泛分布。期间分布铜矿床(点)多处。将成因与玄武岩喷溢-沉积作用有关的铜矿统称为玄武岩铜矿。矿源岩(P_2β)是区域成矿的重要前提,其含矿岩性、产出地质特征、矿石、脉石矿物及围岩蚀变等都有其独特的特征。在云南,丽江式、小寨式铜矿具有找矿前景。决定其规模远景的控制条件是:矿源岩、矿源层、表生改造、储矿构造和氧化带保留程度五大因素。     

胶东西北部仓上金矿床上盘围岩蚀变和黄铁矿标型特征研究

上盘围岩是矿床钻探过程中首先遇到的围岩,研究其蚀变特征具有重要的找矿指导意义。对胶东西北部露天开采的仓上金矿床的详细研究表明,上盘围岩蚀变以绿泥石化为主,蚀变分带自远矿端到近矿端依次为方解石绿泥石化带、赤铁矿绿泥石化带、绿帘石化带和绢英岩化带。黄铁矿的形态、成分和热电性标型显示,成矿过程中上盘围岩提供了丰富的Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｐｂ、Ｚｎ和Ａｕ、Ｐｔ等。上盘围岩的近矿标志是绢英岩化增强,黄铁矿的｛１００｝＋｛２１０｝增多,Ｓ、Ｃｕ、Ｐｂ、Ｚｎ和Ａｕ、Ｐｔ增高,Ｓ／Ｆｅ离子比和ｗ（Ｃｏ＋Ｎｉ）／ｗ（Ａｓ＋Ｓｂ）降低,Ｐ型黄铁矿出现率增高,蚀变岩的金含量增高。     

东昆仑大干沟一带铜金锑矿特征及找矿意义

东昆仑地区处于中朝、塔里木-柴达木、扬子和印度板块的拼合部位,元古宙以来经历了多期次的裂解和拼合。该区以Au、Co、Cu、Pb、Zn、Hg、Sb、As元素组合为特征,其中多处已证实为矿致异常,共发现矿床、矿点等198处,初步显示了良好的找矿前景。目前在大干沟一带已发现铜多金属矿化带一条、金锑含矿构造蚀变带一条。矿化特征基本一致,均赋存于中三叠统闹仓坚沟组北西西向脆韧性剪切带内及两侧的灰白-烟灰色方解石石英脉内,且具有南侧金锑矿化、北侧铜多金属矿化的分带特征。      

兰坪金顶铅锌矿——陆相SEDEX型矿床

矿床形成于兰坪-云龙古新世湖盆东部,沘江同生断层西侧的次级坳陷。容矿岩系为古新统云龙组中、上段。中段为重力滑塌岩块及角砾岩相-构造活动型冲积扇相沉积;上段为河口砂坝相沉积。矿床两层结构明显:上部是化学沉积成矿系统;下部是补给成矿系统。两系统的矿体形态、矿石类型、结构构造、矿化及蚀变强弱均有显著差异。矿床显示SEDEX型(Sedimentary Exhalation喷气沉积的缩写)矿床特征。成矿物质系深源,硫来自硫酸盐经分解而产生的还原硫,成矿介质属混合水。矿床在有利的聚矿次级坳陷、导矿同生断层、有利矿化沉积岩相、上下屏蔽层圈闭及外来岩系掩埋等条件下耦合形成。属陆相SEDEX型铅锌矿床。