The michiquillay porphyry copper deposit

Michiquillay is a mineralized intrusive quartz monzonite porphyry displaying typical porphyry copper alteration zones as found in metallized intrusives of that composition. From the interior outward these are the phyllic, argillic and propylitic zones. The potassic zone is not exposed at the surface. The intrusion and the center of mineralization coincide with the intersection of a major transverse fault and a cross fault. Mineralization appears dominantly to occur in fractures which may be related to each of these major structures, and is ascribed in origin to simultaneous movement on each fault during the period of hydrothermal activity. The stockwork developed at the fault intersection, and which is the locus of the ore body, fades as distance is gained away from its center. Coincidentally, intensity of mineralization also weakens.     

多宝山斑岩铜矿床成因模式

多宝山斑岩铜矿床位于蒙古—鄂霍茨克(古亚洲)地槽东部。矿区周围出露的地层以中古生界为主,在复背斜核部出露有奥陶系。从多宝山矿区向东南40公里为新开岭隆起,隆起呈北东东走向,上面地层多属下古生界和前古生界,而其东南广大地区地层多属石炭二叠系。多宝山矿区含矿的花岗岩体,经K-Ar法年龄测定,为292百万年,属中石炭世。由此可见,在多宝山矿床形成期间,多宝山矿区应位于正负构造单元接壤处偏隆起一侧。     

埃达克岩与斑岩铜矿

埃达克岩与斑岩铜矿有着密切的关系,世界级的斑岩铜矿大多与O型埃达克岩有关,表明板片部分熔融形成的(O型)埃达克岩最有利于成矿,而我国的斑岩铜矿大多与C型埃达克岩有关.埃达克岩可以作为找矿标志来使用,从而开辟了一条新的找矿思路,对寻找超大型和超巨型斑岩铜矿会有所启发.文中指出,中国北方造山带、吉黑东部和冈底斯地区具有寻找斑岩铜矿的广阔前景.     

五子骑龙矿床——被改造的斑岩铜矿上部带

五子骑龙矿床产于紫金山矿田的一个早白垩世火山管道旁侧。火山管道中充填的英安斑岩向深部逐渐相变为花岗闪长斑岩。由于后期断裂的破坏，该花岗闪长斑岩及其矿化系统被上冲到与五子骑龙矿床相邻的中寮矿床近地表位置，从而形成斑岩型铜矿床－中寮矿床。五子骑龙矿床中，环绕英安斑岩发育明矾石化、迪开石化、埃洛石化和红柱石化蚀变，这些蚀变是改造并叠加早期绢英岩化蚀变的结果。其铜矿石中的铜蓝、硫砷铜矿和蓝辉铜矿，也经常交     

Origin of the Skagit migmatites,North Cascades Range,Washington State

Stromatic and schlieren-type migmatites are a major lithology in the type section of the Skagit Gneiss complex in the North Cascades Range of Washington State, USA. Migmatite mesosomes are chiefly biotite schist, amphibolite, and orthogneiss, in decreasing order of abundance. Leucosomes are predominantly leucotrondhjemites with a very limited range of composition that is nearly independent of associated mesosome type. Melanosomes, consisting mainly of biotite and/or hornblende±garnet, are inconsistently developed and absent in places. The age of migmatization is not well established, but appears to be Late Cretaceous or early Tertiary. This is also the age of syntectonic tonalite to trondhjemite intrusives that are predominant in most parts of the Skagit complex. Although temperatures in excess of 700° C and pressures as high as 10 kb occurred, there is no evidence for widespread partial melting of the mesosomes with which the migmatites are closely associated. Mass balance calculations preclude an origin by injection of a silicate melt or hydrothermal fluid unless accompanied by metasomatic replacement reactions. Mass balance relationships also show that the Skagit migmatites could not have formed solely by closed system processes such as partial melting or metamorphic segregation, unless the mesosomes present were not the protolith from which the migmatites formed. Field, petrographic and geochemical data indicate that an origin by migmatization of a missing mesosome is quite unlikely. The most feasible process of migmatization appears to be infiltration of an aqueous fluid into a metamorphic protolith along fracture or foliation planes. This triggers a variable degree of metamorphic segregation or possibly minor partial melting. Unmixing of leucosomes and melanosomes from the mesosome protolith must be accompanied by metasomatic replacement, but the total mass transfer required is only a few wt%.     

云南普朗斑岩铜矿床地质特征

普朗斑岩铜矿地处甘孜-理塘结合带西侧德格-中甸陆块东缘,印支期义敦-中甸岛弧带南段。矿区地层为上三叠统图姆沟组,主要出露普朗印支期复式中酸性斑(玢)岩体,构造裂隙发育,岩石蚀变强烈,具典型的“斑岩型”蚀变分带:由中心向外依次为强硅化带→硅化钾化带→绢英岩化带→青磐岩化带。岩浆岩、岩浆侵位的地层、热液蚀变作用、热液运移和矿质沉淀的构造空间控制了本矿床的产出。其成矿作用发生于普朗复式斑岩体内,矿化与蚀变相伴进行,在岩体中心形成由细脉浸染状矿石组成的筒状矿体,岩体边部产出脉状矿体。成矿元素以铜为主,伴有金、银、钼、钯、硫等多种有用组分。矿床规模达到超大型。     

西藏朱诺斑岩铜矿床发现的重大意义及启示

朱诺斑岩铜矿床位于冈底斯火山岩浆弧之中西部,它是在原区域化探成果中无任何有编号异常的情况下,通过对原始化探数据进行重新处理时发现的,是迄今为止品位最富的大型斑岩铜矿床。它的发现“使冈底斯斑岩铜矿带的勘查区域向西延伸了数百km,有望发展成为巨型斑岩铜矿带”,自此揭开了在冈底斯西部寻找斑岩铜矿的序幕。该成果入选2004年全国地质调查工作重大新闻第二名(地质成果第一名),这是创新思维与科学找矿的范例。文章在较系统介绍了该矿床的成矿背景、矿化特征、发现过程及勘查新进展的同时,客观展示了笔者运用新的找矿思路对原有化探数据进行二次开发、赋予各种信息以客观的地质内涵、进行异常筛选及成矿预测研究的全过程;特别是在找矿难度越来越大的今天,对于启迪人们的找矿思路及降低勘查风险、快速缩小找矿靶区等方面具有非常重大的理论及现实意义。     

Don Javier斑岩型铜钼矿床地质特征

Don Javier矿床是在秘鲁南部新发现的大型斑岩铜钼矿床,位于秘鲁古近纪斑岩型铜钼成矿带内。该矿区主要出露Yarabamba花岗闪长岩体,NW走向的矿体赋存于英安斑岩及其围岩中。主要的矿石矿物有黄铜矿、辉钼矿、辉铜矿等。矿化蚀变由内向外依次为钾化、石英-绢云母化、泥化、青磐岩化,具有典型斑岩型铜矿床的蚀变分带特征。矿体呈筒状,主要分布于石英-绢云母化蚀变带中。矿区内的英安斑岩有4期,其中的前2期与矿化有关,后2期为成矿后侵位。NW向断裂是区内主要的控矿构造,对成岩成矿具有控制作用。与同一成矿带内相邻的Cerro Verde超大型斑岩型铜矿床相比较,两者具有类似的成矿特征。找矿实践表明,强烈的蚀变带、低阻高极化激电异常是找矿的有效标志。     

Environmental geochemistry of the Bingham Canyon porphyry copper deposit,Utah

At the Bingham Canyon porphyry copper deposit, sulfide mineralization progresses outward from a low-grade core through the following general zones: (1) molybdenite, (2) chalcopyrite-bornite, (3) chalcopyrite-pyrite, (4) pyrite, and (5) sphalerite-galena. The low-grade core and the molybdenite zone are composed of net neutralizing rock and will generally not acidify when exposed to surface weathering conditions. The copper-bearing zones of the orebody and the surrounding pyrite halo are net acid-generating and so will tend to acidify when exposed. Rocks in the lead-zinc halo are typically net neutralizing. In plan view, the distribution of net neutralization potential (NNP) is doughnut-shaped, with a positive (net neutralizing) 1,000-m-diameter core surrounded by a negative (net acid-generating) 3,000-m-diameter ring. Rock exposed in the lower 100 m of the current pit has a positive NNP and is overlain by 500 m of rock with a negative NNP.     

Mantle origin of the Dexing porphyry copper deposit,SE China

The Dexing ore deposit, Jiangxi Province, is the largest porphyry copper deposit in China. Controversies exist regarding the ore-forming source of this deposit. We have conducted Pb isotope analyses of pyrites from the Tongchang and Fujiawu mines. Our results document consistent Pb isotopes from these two orebodies, with ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios of 17.954–18.320, 15.407–15.517, and 37.888–38.153, respectively. These Pb isotope ratios are consistent with those of ore-bearing adakitic porphyries but distinctly different from those of the Neoproterozoic metamorphic wall rocks, which indicates that the metals were derived from the porphyries. Based on previous S and Os isotopic data and comparisons with more than 20 Mo-bearing deposits worldwide, we further attribute the narrow range of δ³⁴S values of sulphide minerals and high Re–¹⁸⁷Os concentrations of associated molybdenites to a mantle origin. This large-scale copper deposit was evidently emplaced in a continental arc setting attending westward subduction of the palaeo-Pacific plate. Partial melting of the downgoing oceanic slab generated the adakitic magmas. The associated metals were extracted from the lithospheric mantle by these magmas during ascent through the mantle wedge.     

云南普朗斑岩型铜矿成矿岩体的基本特征

普朗斑岩型铜矿是格咱地区印支期斑岩型铜矿的典型代表,产于义敦构造-岩浆带南端的复式岩体。复式岩体为浅成-超浅成的中酸性斑(玢)岩体,可划分为3个侵入阶段,最早为石英闪长玢岩,中期为石英二长斑岩,晚期为花岗闪长斑岩。岩石地球化学特征表明,岩石富集Ba、La、Rb、Sr、K和亲铜元素Cu、Pb,亲铁元素Mo、Ni,亏损Nb、Zr、Hf、Ti。斑(玢)岩与岛弧花岗岩的岩石系列相同,属钙碱性岩系,成因类型一致,属I型花岗岩。普朗斑岩型铜矿床主要产于印支期的中酸性斑(玢)岩体,成矿作用受岩浆岩、侵位地层、热液运移、热液蚀变作用和构造空间的控制,其印支期构造-岩浆-热液之间的耦合,共同形成了斑岩成矿系统。     

西藏玉龙铜矿床——鼻状构造圈闭控制的特大型矿床

文章研究了背斜圈闭构造控制玉龙斑岩-矽卡岩型铜(钼)矿的形成和矿体的分布。通过对成矿体系中各矿体的产出和形态特征、矿床地球化学原生晕分布特征、圈闭构造的古构造应力场恢复等的研究,认为玉龙铜矿的斑岩型(Ⅰ号矿体)、矽卡岩型(Ⅱ、Ⅴ号似层状原生矿体、Ⅴ号矿体上层矿体)、矽卡岩-次生氧化富集型(Ⅱ、Ⅴ号似层状次生氧化矿体)、角岩型(接触带角岩中硫化物矿体)、隐爆角砾岩型等矿体的分布受甘龙拉背斜的南段倾伏端的构造圈闭控制。因此,超大型玉龙铜(钼)矿床的形成与良好的背斜圈闭构造有关。     

新疆土屋大型斑岩铜矿床特征及发现意义

土屋铜矿是新疆地矿局近年在斑岩型铜矿地质找矿方面取得的一项重大突破。矿床产于准噶尔板块南缘石炭纪增生拼贴岛弧带中。矿体赋存于石炭纪闪长玢岩和斜长花岗斑岩岩体内。属细脉浸染状矿化，具有厚度大、矿化均匀、品位低、组分简单、围岩蚀变分带明显的特点。目前初步控制的远景规模可望达大型以上。该矿床的发现不仅对新疆斑岩型铜矿的地质找矿具有重要指导意义，而且对促进新疆今后矿业经济的发展将起到重要作用。     

多元统计分析在普朗斑岩型铜矿床中的应用

普朗斑岩型铜矿是云南格咱岛弧成矿带中印支期斑岩型铜矿床的典型代表。本文应用聚类分析、因子分析方法对普朗斑岩型铜矿成矿岩体中微量元素进行了分析和科学分类。根据普朗复式斑(玢)岩体的地质条件和微量元素地球化学特征,从理论角度定性分析和定量分析均确定了普朗复式岩体存在明显的Cu-Au-Ag矿化异常,主成矿元素Cu与Au、Ag、Mo、W等具有较好的相关性,且局部存在中―低温的Pb、Zn矿化异常组合。矿床的形成与印支期中酸性斑(玢)岩体的侵入有密切的联系,成矿作用具多期多阶段性。     

The geochemistry of the leached capping of the La Granja porphyry copper deposit, Peru

Ninety rock samples from the La Granja porphyry copper in northern Peru have been analyzed for 30 elements, 10 of which are discussed here. Although intense weathering has produced a leached capping up to 200 m thick, the distribution of Mg, Ca, Na, K, Rb and Sr can still be correlated with different phases of hydrothermal alteration.There has been complete supergene leaching of sulphides; Cu has been depleted 10 to 30 times and Mo up to twice with respect to hypogene ore, Fe has been enriched in some parts of the leached capping, whereas Au remained stable. The coincidence of low Fe, high Mo and high Au contents with a high Cu/Fe ratio in the capping indicates the approximate centre of the underlying orebody. Also, high K, Rb, Mg and low Sr indicate high-grade copper ore.     

Lead isotope data from the Sar-Cheshmeh porphyry copper deposit,Iran

Lead isotope compositions of nine sulfide concentrates from ore samples from the Sar-Cheshmeh deposit are reported. They range from virtually unaltered granodiorite through varying degrees of potassic alteration to ores showing strong phyllic alteration (sericite veins). The samples without strong phyllic alteration have fairly uniform lead isotope compositions around ²⁰⁶Pb/²⁰⁴Pb=18.6, ²⁰⁷Pb/²⁰⁴Pb=15.6, and ²⁰⁸Pb/²⁰⁴Pb=38.7. Two samples with sericite veins have markedly more radiogenic lead. It is concluded that the fluid responsible for the potassic alteration and the associated mineralization was essentially magmatic, whereas convecting meteoric water from the country rock acted as a mineralizing solution during phyllic alteration. In the context of the plumbotectonics model, the deposit has a typical orogen signature intermediate between primitive and mature island-arc settings.     

东天山土屋特大型斑岩铜矿成矿地质特征与矿床对比

土屋特大型斑岩铜矿位于东天山吐鲁番—哈密陆块南部边缘岛弧环境中。多期岩浆活动和矿化是铜金属超常堆集的主要因素。海底火山活动和热泉沸腾逸散造就了铜金属的预富集(矿源层),闪长玢岩和斜长花岗斑岩的侵位和叠加矿化使铜金属进一步富化和最终成矿。以细碧角斑质为主的火山岩喷发于潮坪—滨海环境,闪长玢岩、斜长花岗斑岩形成于较强的氧化环境;强还原示踪矿物黄铁矿含量较少。矿石的低品位、矿石的结构构造、蚀变特征以及矿石建造具典型斑岩矿床特征;矿石高品位、矿床形成较低温度及大量硅化蚀变又表现为某些热液矿床特征(次火山岩热液)。典型斑岩铜矿床、次火山热液矿床、土屋铜矿床对比,土屋铜矿床矿床类型仍不失为斑岩型铜矿,并具有自身特征。     

The mineralogy of propylites of the large Peschanka porphyry copper deposit (West Chukotka)

The Au-Mo-Cu porphyry Peschanka deposit is confined to the Egdygkych Pluton (K₁). The deposit comprises three major types of metasomatic rocks: quartz-K-feldspar-biotite, propylites and quartz-sericite. In their chemical compositions, amphiboles of propylites range from early magnesiohornblende to tremolite-actinolite. Compared to magmatic K-feldspar, the metasomatic K-feldspar is enriched in barium (up to 7.3 wt % BaO). Tourmaline belongs to the intermediate member of the oxydravite-povondraite series. The Al content in chlorite decreases to the outer zones of propylitization, which is caused by a decrease in the temperature of mineralization.     

阿尔泰铜矿带南缘希勒克特哈腊苏斑岩铜矿的发现及其意义

希勒克特哈腊苏铜矿位于阿尔泰铜矿带南缘,即原卡拉先格尔斑岩铜矿带内。初步的研究和钻孔资料表明,铜矿体完全受斑岩体(石英闪长斑岩和花岗闪长斑岩)控制,矿石具细脉浸染状构造,金属矿物主要为黄铜矿和黄铁矿以及少量的磁铁矿、斑铜矿和镜铁矿。其中磁铁矿形成早于黄铜矿,指示了岩浆具有较高的氧化状态。矿化蚀变分带与斑岩铜矿基本相似,岩体内见钾长石化、黑云母化、硅化和黄铁矿化,接触带见石英绢云母化,围岩见青磐岩化。含矿斑岩的地球化学特征表明其属于埃达克岩(adakite):高SiO2(63%～66%)、高Al2O3(15%～17%)、富集Sr(378×10-6～447×10-6)、无负Eu异常、亏损Y(10×10-6～14×10-6)和Yb(1.3×10-6～1.5×10-6)以及低的Sr同位素初始值(0.70439)、高的(εNd)t(+6.9～+8.2)和低的δ18OV-SMOW(<10‰)。其Rb-Sr等时线年龄为(332.8±8.5)Ma,为早石炭世侵位的产物,其形成与蒙古洋板块向南俯冲造成的洋壳部分熔融有关,因此其成矿地质背景与世界巨型斑岩铜矿十分相似。另外,在希勒克特哈腊苏铜矿外围还有数个与其十分相似的铜矿点,因此该地区展示了良好的找矿前景,同时也是中国又一个潜在的斑岩铜矿带。     

Factors controlling copper solubility and chalcopyrite deposition in the Sungun porphyry copper deposit, Iran

The Sungun porphyry copper deposit is hosted in a Diorite/granodioritic to quartz-monzonitic stock that intruded Eocene volcanosedimentary and Cretaceous carbonate rocks. Copper mineralization is associated mainly with potassic alteration and to a lesser extent with sericitic alteration. Based on previously published fluid inclusion and isotopic data by Hezarkhani and Williams-Jones most of the copper is interpreted to have deposited during the waning stages of orthomagmatic hydrothermal activity at temperatures of 400 to 300 °C. These data also indicate that the hydrothermal system involved meteoric waters, and boiled extensively. In this work, thermodynamic data are used to delineate the stability fields of alteration and ore assemblages as a function of fS₂, fO₂ and pH. The solubility of chalcopyrite was evaluated in this range of conditions using recently published experimental data. During early potassic alteration (>450 °C), Copper solubility is calculated to have been >50 000 ppm, whereas the copper content of the initial fluid responsible for ore deposition is estimated, from fluid inclusion data, to have been 1200–3800 ppm. This indicates that initially the fluid was highly undersaturated with respect to chalcopyrite, which agrees with the observation that veins formed at T > 400 °C contain molybdenite but rarely chalcopyrite. Copper solubility drops rapidly with decreasing temperature, and at 400 °C is approximately 1000 ppm, within the range estimated from fluid inclusion data, whereas at 350 °C it is only 25 ppm. These calculations are consistent with observations that the bulk of the chalcopyrite deposited at Sungun is hosted by veins formed at temperatures of 360 ± 60 °C. Other factors that, in principle, may reduce chalcopyrite solubility are increases in pH, and decreases in fO₂ and aCl⁻. Our analysis shows, however, that most of the change in pH occurred at high temperature when chalcopyrite was grossly undersaturated in the fluid, and that the direction of change in fO₂ increased chalcopyrite solubility. We propose that the Sungun deposit formed mainly in response to the sharp temperature decrease that accompanied boiling, and partly as a result of the additional heat loss and decrease in aCl⁻, which occurred as a result of mixing of acidic Cu-bearing magmatic waters with cooler meteoric waters of lower salinity. Received: 8 July 1998 / Accepted: 8 April 1999