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J. A. Saunders D. L. Unger G. D. Kamenov M. Fayek W. E. Hames W. C. Utterback 《Mineralium Deposita》2008,43(7):715-734
Epithermal deposits with bonanza Au–Ag veins in the northern Great Basin (NGB) are spatially and temporally associated with
Middle Miocene bimodal volcanism that was related to a mantle plume that has now migrated to the Yellowstone National Park
area. The Au–Ag deposits formed between 16.5 and 14 Ma, but exhibit different mineralogical compositions, the latter due to
the nature of the country rocks hosting the deposits. Where host rocks were primarily of meta-sedimentary or granitic origin,
adularia-rich gold mineralization formed. Where glassy rhyolitic country rocks host veins, colloidal silica textures and precious
metal–colloid aggregation textures resulted. Where basalts are the country rocks, clay-rich mineralization (with silica minerals,
adularia, and carbonate) developed. Oxygen isotope data from quartz (originally amorphous silica and gels) from super-high-grade
banded ores from the Sleeper deposit show that ore-forming solutions had δ
18O values up to 10‰ heavier than mid-Miocene meteoric water. The geochemical signature of the ores (including their Se-rich
nature) is interpreted here to reflect a mantle source for the “epithermal suite” elements (Au, Ag, Se, Te, As, Sb, Hg) and
that signature is preserved to shallow crustal levels because of the similar volatility and aqueous geochemical behavior of
the “epithermal suite” elements. A mantle source for the gold in the deposits is further supported by the Pb isotopic signature
of the gold ores. Apparently the host rocks control the mineralization style and gangue mineralogy of ores. However, all deposits
are considered to have derived precious metals and metalloids from mafic magmas related to the initial emergence of the Yellowstone
hotspot. Basalt-derived volatiles and metal(loid)s are inferred to have been absorbed by meteoric-water-dominated geothermal
systems heated by shallow rhyolitic magma chambers. Episodic discharge of volatiles and metal(loid)s from deep basaltic magmas
mixed with heated meteoric water to create precious metal ore-forming fluids. Colloidal nanoparticles of Au–Ag alloy (electrum),
naumannite (Ag2Se), silica, and adularia, likely nucleated at depth, traveled upward, and deposited where they grew large enough to aggregate
along vein walls. Silica and gold colloids have been reported in hot springs from Yellowstone National Park, suggesting that
such processes may continue to some extent to the present. However, it is possible that the initial development of the mantle
plume led to a major but short-lived “distillation” process which led to the mid-Miocene bonanza ore-forming event.
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| J. A. SaundersEmail: |
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西秦岭金龙山卡林型金矿床地质-地球化学及矿床成因研究 总被引：1，自引：0，他引：1
金龙山金矿床位于南秦岭造山带的复理石褶冲带中,赋矿围岩为碎屑岩-碳酸盐建造,矿化明显受地层岩性与韧-脆性构造发育程度的控制。矿床稀土元素地球化学研究表明,地层岩石、矿石和热液矿物的轻重稀土分异程度和特征参数基本一致,表明成矿流体应主要来自于赋矿地层。铅同位素研究表明,地层岩石、矿石和热液矿物均具有较高的放射性成因的铅同位素组成,且均落入南秦岭造山带的泥盆系范围内,暗示铅也主要来自赋矿地层。对前人已有的碳-氧-硫-氢同位素组成和流体包裹体数据综合分析表明,碳和氧应主要来自海相碳酸盐的溶解作用,硫主要来自海相硫酸盐的热化学还原反应;从成矿早阶段到晚阶段,成矿流体的δ18O及δD值向大气降水线＂漂移＂,指示成矿流体以盆地建造水和变质水为主,在晚阶段有大气降水加入。金龙山金矿床与卡林型金矿床的矿床地质-地球化学特征相似,应属于卡林型金矿床,其形成于秦岭造山带陆内造山作用过程中,多层次陆壳叠置加厚的地球动力学背景,是陆内碰撞造山作用的产物。 相似文献
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四川丹巴县独狼沟金矿床是扬子陆块西缘金成矿带上的一个大型金矿床。矿体呈较高品位、较厚单体石英脉充填于构造破碎带之间,呈透镜状、似层状和层状产出,受断层构造影响极为明显,具热液矿床特征。矿物学、锆石U-Pb测年成果和稀土元素及微量元素等方面研究显示矿床主要受两期热液成矿作用影响,早期热液成矿作用形成以磁黄铁矿、黄铁矿等高温热液矿物为主的金矿体,时限限定于184.2±1.1 Ma;晚期热液成矿作用则形成以黄铜矿、叶碲铋矿等中温热液矿物为主的金矿体,时限限定于156.5±4.3 Ma。成矿流体氢氧同位素组成表明其与该时期区域岩浆作用存在一定关联而与区域变质作用关系不密切。S同位素组成反映出其来源为深部来源的属性,在Pb同位素组成的研究中也对这一观点进行了验证。成矿流体被认为是来自交代岩石圈地幔,在早侏罗世软流圈上涌事件影响下交代岩石圈地幔中挥发分上涌并活化上覆地层中的金,从而形成富金成矿流体并沿区域性深大断裂上移就位于地壳岩石地层中成矿。成矿动力学机制与区域碰撞造山后由挤压向伸展转换的大地构造背景密切关联,认为独狼沟金矿床为典型造山型金矿床。 相似文献
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辽宁白云金矿床稳定同位素地球化学特征及矿床成因 总被引：1，自引：0，他引：1
白云金矿床是辽东地区的一个大型金矿床,其成矿物质来源及矿床成因一直存在争议。本文系统地研究了白云金矿床的氢、氧、硫和碳同位素地球化学特征。研究结果显示:成矿流体中δ~(18)OV-SMOW值变化范围为13.5‰15.9‰,δD_(V-SMOW)为-107‰-83‰,表明成矿流体以岩浆水为主;矿石中黄铁矿的δ~(34)S_(V-CDT)为-8.3‰2.9‰,以富轻硫和贫重硫为特征,与辽河群围岩中黄铁矿的硫同位素组成(δ~(34)S_(V-CDT)为7.0‰18.7‰)有明显差异;矿石中方解石的碳同位素δ~(13)C_(V-PDB)为-2.2‰-0.4‰,类似于火成碳酸岩或地幔包体来源的碳同位素特征,也与辽河群大理岩的碳同位素组成明显不同。成矿元素特征对比也显示,成矿物质来源与辽河群没有必然联系。综合矿床地质特征和地球化学特征,认为白云金矿床是与深部岩浆流体活动有关的岩浆热液型金矿床。 相似文献
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山西省阳高县堡子湾金矿床矿物标型特征 总被引：2，自引：0，他引：2
根据成因矿物学及找矿矿物学观点，系统研究堡子湾金矿床黄铁矿、金矿物、方铅矿、黄铜矿和闪锌矿等金属矿物，石英、碳酸盐、绢(白)云母和金红石等非金属矿物的产状、形态及化学成分标型，结果表明：①矿床中矿物组合复杂，硫化物种类多，有少量硫盐矿物出现；②矿物中微量元素成分复杂，富含As，Sb，Bi，Se，Te等Au活化、迁移有利的矿化搬运剂，Cu，Ph，Zn，Au，Ag等成矿元素和Cr，Ni，V等深源元素；元素矿物组合及其特征比值指示金矿化与深源(下地壳或上地慢)浅成岩浆热液活动(斑岩系统)有关，燕山期石英二长斑岩(角砾岩)是成矿的主导因素；③矿石中大量出现铁白云石、富铁闪锌矿，粒状、富Ti金红石的大量分布，反映矿床剥蚀深度较大，目前可能已揭露至中深部中温带，位于斑岩系统的中下部，深部金矿化不利；④矿石含丰富的铜矿物，其他硫化物矿物中含铜量大，指示深部可能存在斑岩型Cu(Au)矿化。 相似文献
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为了解卡尔却卡铜多金属矿床的物质来源, 探讨其成岩、成矿机制, 通过现场调查, 结合矿床地质成矿条件, 对矿区典型的岩浆岩、围岩及矿石进行了主量元素、微量元素分析及S、Pb同位素分析.结果表明: 矿区岩体属中酸性岩, 为高钾钙碱性系列岩石, 源于深部, 上侵时受地壳混染, 具同源特征.不同地质体稀土配分曲线均为右倾轻稀土富集型, 岩浆岩、矽卡岩和矿石为同一成矿系统.微量元素地球化学显示矿区花岗岩产于火山弧环境.矿石硫同位素δ34SCDT值为4.4×10-3~11.0×10-3, 处于岩浆硫跟围岩混合硫范围内, 成矿物质具多源性.矿石铅同位素Th/U值范围为3.46~3.69, μ值为9.46~9.52, 均低于9.58, 介于地壳与原始地幔值之间, 反应矿石铅具深源铅和壳源铅特征.铅同位素特征参数示踪、构造模式示踪和Δβ-Δγ图解示踪的结果表明: 铅来源与岩浆作用有关, 以壳源铅为主并混合少量深源地幔铅.总结矿床地球化学特征表明成矿物质主要来源于岩浆, 少量来源于周围地层.矿区岩体成矿演化过程复杂, 在岩体中形成斑岩型铜、钼矿化, 在与碳酸盐岩接触带形成矽卡岩型铅、锌矿化, 及至后期热液作用形成中低温热液脉型金矿化, 是一个多因复成矿床. 相似文献
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通过对辽西北票二道沟金矿Ⅲ号脉的不同中段的矿石组构、金的分布特点和主要载金矿物立方体、五角十二面体及它形黄铁矿的热电性研究,讨论了成矿特征,计算了成矿温度和矿体剥蚀率并对深部找矿远景进行了预测。研究表明:二道沟金矿金的分布特点存在不均匀性;黄铁矿热电性以P型为主且变化范围宽,只有少量的N型,表明矿体的剥蚀率较低。二道沟金矿可能存在多期次的热液活动,且每一期次相互叠加改造;成矿热液来自南东方向,成矿热液早期温度较高,金属元素大量沉淀温度为150～300℃,属中低温,且不同中段的成矿温度有一定的变化规律。不同晶形的黄铁矿热电性研究表明,不同晶形载金能力不同,黄铁矿热电性P型频率不同,形成的温度不同,但计算的矿体剥蚀率相差不大。 相似文献
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《International Geology Review》2012,54(12):1149-1165
The Gay deposit, situated in the Orenburg region, is identified with one of Russia's principal occurrences of pyrite (pyrite deposits are an important source of Russia's gold). It belongs to the west subzone of the Magnitogorsk synclinorium and occurs in Devonian rhyolite-basaltic volcanic rocks. The deposit comprises five large pyrite-chalcopyrite, pyrite-chalcopyrite- sphalerite, and pyrite orebodies. The supergene zone extends to 120-240 m below surface and consists of the following three subhorizontal zones (from bottom to top): the secondary sulfide enrichment, the leaching, and the oxidation zone (where ores are enriched in gold). There are two levels of secondary gold enrichment in the weathering profile. The lower level, located in the leaching zone, corresponds with the level of water table fluctuations. The rich, flat-lying horizon (1.5-10.0 m) is composed of bedded, friable native sulfur-quartz ores; it contains 19.0-52.2 ppm Au and up to 389 ppm Ag. Native gold and silver halides (chlorargyrite, iodargyrite, and embolite) are the principal precious-metal minerals. Electrum, native silver, acanthite, and uytenbogaardtite constitute the minor ones. The upper level of the enrichment is located in the lower part of gossan. This bonanza is composed of hematite-quartz ochres. Gold concentration is 13.5 to 21.2 ppm. Native gold of high fineness and silver halides apparently are associated here with poorly crystallized iron oxides. The formation of supergene gold enrichments may result partly from residual concentration and partly from mobilization and reprecipitation of the precious metal. Rich horizons form by repeated gold redeposition in accordance with weathering and a gradual erosion surface lowering. The lower bonanza forms at first in the process of oxidation involving pyrite and native sulfur. Gold may be transported by complexes with metastable sulfur oxy-anions: sulfites, thiosulfates, or polythionates. The upper enriched horizon forms in the course of further evolution of the weathering profile in the stage of hematite recrystallizaiton and its transformation into goethite. 相似文献
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甘肃北山拾金坡金矿床地质特征及成因分析 总被引：1，自引：1，他引：1
拾金坡金矿是甘肃北山南带较为典型的含金硫化物石英脉型金矿床,矿化富集与加里东晚期—海西早期拾金坡复式岩体密切相关。矿体产于岩体的内接触带,产出部位明显受近EW向断裂破碎带的控制。矿体主要为大脉状、脉状、透镜状。矿床中发育一套典型的中温热液成因的矿物组合,矿石以强烈的绢云母化、碳酸盐化、硅化和黄铁矿化为特征,矿石的金属矿物组合为自然金_银金矿_黄铁矿_方铅矿_闪锌矿_黄铜矿,矿化属中温热液成因。硫和铅同位素显示成矿金属物质主要来自围岩,即斑状花岗岩;氢和氧同位素组成表明成矿流体来自花岗岩浆水。成矿时代属早—中海西期。因此可推断,拾金坡金矿床属于与构造_岩浆活动有关的中温岩浆热液成因矿床。 相似文献
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Submillimeter Scale Variation of Oxygen Isotope of Vein Quartz at the Hishikari Deposit, Japan 总被引：2，自引：1，他引：1
Abstract: The physical and chemical mechanism of gold precipitation in the typical low-sulfidation epithermal gold deposit at the Hishikari mine was quantified by submillimeter scale oxygen isotope analyses of vein quartz. In situ CO2 laser-ablated fluorination was used to measure temporal δ18 O excursions. The calculated oxygen isotopic compositions of the ore-forming fluid indicate a dynamic process of epithermal vein formation. Intermittent opening of the vein allowed introduction of metal-bearing deep fluid to the epithermal system, and associated boiling and subsequent mixing with meteoric water caused precipitation of precious metals. 相似文献
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山东谢家沟金矿床矿石与金矿物特征 总被引：2，自引：0，他引：2
新发现的谢家沟大型金矿床位于山东招远市西南部, 对其进行详细的宏观、微观矿石学基础研究, 包括矿石类型和成矿期次的划分以及金矿物的成色等, 对指导该区找矿具有重要意义.矿石类型划分为原生矿石和氧化矿石, 其中原生矿石分为黄铁绢英岩、黄铁矿-黄铜矿绢英岩、多金属硫化物绢英岩和黄铁矿-黄铜矿石英脉等4类, 它们分布于脆-韧性剪切带不同部位, 成矿作用方式有差别.成矿期次分2期5阶段.金的赋存状态主要有包体金、晶隙金和裂隙金, 金矿物成色平均值为844.19, 为中深成矿作用产物, 其中包体金成色均值为859.96, 晶隙金为843.83, 裂隙金为833.08, 反映从包体金至晶隙金再到裂隙金的成矿作用温度是逐渐降低的. 相似文献
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甘肃省阳山金矿田金的赋存状态和金矿物特征 总被引：1，自引：0，他引：1
甘肃阳山金矿田属于类卡林型金矿床,金矿化类型主要有蚀变千枚岩、蚀变斜长花岗斑岩、蚀变砂岩、蚀变灰岩四种。金多呈独立金矿物形式出现,少许呈分散状,矿石中金矿物以自然金为主,其次是银金矿。金矿物以包体金、裂隙金、粒间金等形式嵌布于毒砂、黄铁矿、辉锑矿、粘土矿物等主要载金矿物中,且毒砂、黄铁矿、辉锑矿较其它金属硫化物中占优势。金矿物形态各样,粒度以微细粒为主。金矿物特征反映出本区金矿床的成矿物质主要来源于变质岩、岩浆岩和地幔,成矿作用与印支晚期中酸性侵入岩有关。这与地质地球化学研究所获得的矿床成因认识相一致。 相似文献
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辽宁朝阳小塔子沟-东五家子金矿田地球化学特征 总被引：1，自引：1，他引：0
在朝阳小塔子沟-东五家子金矿田范围内,北地金矿、小塔子沟金矿和东五家子金矿,因距离岩体的远近不同,形成了不同的特征.石英流体包裹体研究表明,位于岩体内接触带的北地金矿为中温、中-深成热液矿床,位于岩体外接触带的小塔子沟金矿为中温、中成热液矿床,远离岩体的东五家子金矿为中-低温、浅成热液矿床.氢、氧同位素研究表明,北地金矿和小塔子沟金矿的成矿流体主要为岩浆水,东五家子金矿的成矿流体为岩浆水和大气降水混合成因.微量元素研究表明,北地金矿矿石以Mo、Bi等元素相对富集为特征,小塔子沟金矿矿石以Cu、Zn等元素相对富集为特征,东五家子金矿矿石以Pb、Ag等元素相对富集为特征.矿床离岩体越远,金矿物中Au/Ag比值越小. 相似文献
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新疆托里萨I金矿床产于托里蛇纹岩套的超镁铁岩相内,与超镁铁岩的蚀变交代作用有关.矿床地球化学研究表明该矿床的形成与海底热泉活动有关,是一种新的金矿床类型. 相似文献
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Ore-Forming Fluid Characteristics of the Dayingezhuang Gold Deposit, Jiaodong Gold Province, China 总被引：27，自引：0，他引：27
Liqiang Yang Jun Deng Chunying Guo Jing Zhang Shaoqing Jiang Bangfei Gao Qingjie Gong Qingfei Wang 《Resource Geology》2009,59(2):181-193
The Dayingezhuang gold deposit is located in the central part of the Zhaoping Fault Zone, which is one of the most important gold-hosting faults in the Jiaodong gold province of China. Dayingezhuang is a typical large-scale shear zone-hosted disseminated gold deposit with superimposed silver mineralization. Fluid inclusion (FI) petrography and microthermometry, and analysis of oxygen and hydrogen isotopes for fluid inclusions were conducted to determine the characteristics of the ore-forming fluids and the processes of silver mineralization. Microthermometry data of FI indicated that ore-forming fluids are characterized by low salinity and low density. Homogenization pressures of FI are estimated at 20 × 105 –220 × 105 Pa. The change in ore-forming fluids from K2 SO4 type to NaCl type indicates the superposition of two hydrothermal mineralizing events. Ore-forming fluids were dominated by magmatic components in the early mineralization period, and affected by meteoric waters in the late period. Gold may have been transported as Au-S or Au-Cl complexes, whereas silver was transported as Ag-Cl complexes. Early fluid boiling and later fluid mixing are thought to be two of the main factors causing the deposition and superimposing of gold and silver to form the large deposit. 相似文献