Geology of gold-bearing skarn deposits in the middle and lower Yangtze River Valley and adjacent regions

The middle and lower Yangtze River Valley and adjacent regions are the most important metallogenic belt of gold (and copper)-bearing skarn deposits in China. The total gold reserves in this belt have been estimated at more than 600 t. The gold-bearing skarns are mainly distributed in the southeastern Hubei, Tongling and northern Anhui regions. Favorable tectonic settings are depressions and fold zones of the platforms, i.e., mobile belts. These skarns are hosted by platformal limestone, dolomitic limestone and dolomite of the Triassic, Carboniferous-Permian and Middle to Lower Cambrian formations. The related intrusions are Yenshanian (180 to 113 Ma) calc-alkaline quartz monzodiorite, granodiorite, quartz monzonite, monzogabbro, and their hybabyssal facies. The intrusions have high Fe₂O₃/FeO (>0.5) and intermediate initial ⁸⁷Sr/⁸⁶Sr ratios (0.7046 to 0.7087). Their REE distribution patterns are LREE-enriched and exhibit smooth, right-dipping curves. These suggest that the source materials mainly came from upper mantle, with contamination by sialic crustal components. The auriferous skarns are both calcic and magnesian, but calcic skarns are most common. The constituent minerals of the calcic skarns are diopside, garnet, wollastonite, vesuvianite and scapolite, whereas magnesian skarns are dominated by forsterite, spinel, diopside, phlogopite, chondrodite and clinohumite, with abundant superimposed serpentine, clinochlore and brucite. The compositions of coexisting pyroxenes and garnets are diopside and andradite, indicating the high oxygen fugacity and low acidity conditions. Gold is closely associated with Cu (Pb, Zn) sulfides and exists mainly in the form of native gold and electrum. Arsenides, tellurides, bismuthides and selenides are present in many ore deposits. Therefore, Cu, As, Bi, Te, Ag, Pb, Zn, Se and Co are the major metals present in the deposits and are important geochemical ore-searching indicators. In some Au (Fe, Cu) magnesian skarns, magnesiomagnetite, magnesioferrite and ludwigite are locally abundant. The metasomatic zoning in many gold skarn deposits is very distinct consisting of an outward sequence of: Fe (Cu)→Cu (Mo)→Cu (Au)→Au (Cu)→Au (Pb, Zn). The geologic characteristics of Au (Cu) skarn deposits that formed in the mobile platformal setting of China have distinct differences compared to Au skarns formed in orogenic belts at convergent plate margins in British Columbia and the western USA.     

青海西部祁漫塔格地区矽卡岩铁铜多金属矿床的矽卡岩类型和矿物学特征

青海西部祁漫塔格地区矽卡岩型铁铜多金属矿床分布广泛,主要发育两类矽卡岩,即钙矽卡岩和锰质矽卡岩,少数矿区还有镁矽卡岩.钙矽卡岩的组成矿物主要有透辉石、钙铁辉石、钙铝-钙铁系列石榴石、绿帘石、阳起石和方柱石,常伴随Fe、Cu、Mo矿化,构成钙矽卡岩型铁多金属矿床或铜(钼)矿床,而锰质矽卡岩主要由锰钙铁辉石组成,含少量锰三...     

青海尕林格铁矿床矽卡岩矿物学及蚀变分带

尕林格矽卡岩型铁多金属矿床位于青海省西部祁曼塔格成矿亚带的中部.矿体处于花岗闪长岩与滩间山群白云质大理岩接触带内以及外接触带沿NWW向断裂构造破碎带分布的大理岩和蚀变安山岩内.从侵入接触带往东,蚀变岩石分带性明显,主要划分出3种含矿矽卡岩带:含Fe的镁质矽卡岩带,含Fe、Cu的钙质矽卡岩带,含Fe、Pb、Zn的锰-钙质矽卡岩带.镁质矽卡岩带的矽卡岩矿物主要包括镁橄榄石及其蚀变矿物蛇纹石、粒硅镁石、透辉石、斜绿泥石,有关的金属矿物主要为磁铁矿.钙质矽卡岩带的主要矽卡岩矿物有绿钙闪石、铁阳起石、钙铁辉石、铁叶绿泥石、磷灰石、中长石,有关的金属矿物为磁铁矿、磁黄铁矿和少量黄铜矿.与锰-钙质矽卡岩有关的矽卡岩矿物有锰钙铁辉石、钙铁榴石、钙铝榴石、铁镁绿泥石、绿帘石、硅灰石、磷灰石、钙长石等,金属矿物有方铅矿、闪锌矿、磁铁矿和磁黄铁矿.通过对矿物组合的研究,确定了不同矿物组合的生成关系,划分了成矿期次,分为矽卡岩期、退化蚀变期和金属硫化物期,矽卡岩期又分为早、晚2个阶段.矽卡岩早期生成的石榴子石的化学成分端员以钙铝榴石(Gro67～ 99)为主,辉石的成分端员以透辉石(Di96～ 98)为主;矽卡岩期晚期阶段石榴子石的化学成分端员以钙铁榴石(Ad78～98)为主,辉石的成分端员以钙铁辉石(Hd68～ 84)为主.与中国东部矽卡岩型矿床进行对比后发现,锰-钙质矽卡岩带是一种向锰质矽卡岩带过渡的类型,对于寻找与锰质矽卡岩有关的矿化类型具有指示意义.     

腾冲棋盘石铅锌多金属矿成矿规律探讨

矿区位于腾冲西北部东河铁、铜、铅锌多金属成矿区,区内早白垩世花岗岩浆活动强烈,矽卡岩型矿床发育,形成众多铁、铜、铅、锌矽卡岩型矿床,是腾冲西北部重要成矿区,棋盘石矽卡岩型铅锌矿即是其中之一。矿床形成与早白垩世中酸性花岗岩关系密切,矿体位于上二叠统碳酸盐岩外接触带矽卡岩中。地层、岩体对矽卡岩及矿体的控制作用明显。     

湘南黄沙坪多金属矿床花岗质岩浆性质及演化对成矿差异的约束

黄沙坪矿床是湘南地区最大的铅锌矿床,除铅、锌外,可供开采利用的矿种还包括钨、锡、钼、铜、铁、硫等。矿区内岩浆作用复杂、成矿元素多样、矿化类型丰富,是研究湘南地区斑岩-矽卡岩-热液脉型Cu多金属与矽卡岩W-Sn多金属复合成矿作用的理想对象。为查明矿区Cu多金属与W多金属复合成矿机理,本文在已有研究的基础上,从岩石学、矿物学及元素地球化学等方面分别对区内石英斑岩和花岗斑岩这两类成矿岩体开展了系统研究。结果表明,两类岩体具有相似的源区特征,但在源区性质及其演化过程方面仍存在差异:石英斑岩侵位深度更浅,具有相对较高的氧逸度和较低的形成温度;而花岗斑岩则侵位相对更深,具有更高的形成温度和极高的分异演化程度、更低的氧逸度。这些地球化学特征差异可能是制约石英斑岩成铜矿而花岗斑岩成钨矿的重要原因。     

Zircon U–Pb geochronological,trace element,and Hf isotopic constraints on the genesis of the Fe and Cu skarn deposits in the Qiman Tagh area,Qinghai Province,Eastern Kunlun Orogen,China

Fe and Cu skarn deposits are very important skarn types worldwide, but it is currently unclear whether the nature of intrusions related to Fe and Cu skarn deposits exerts a key influence on variations in metal associations between Fe and Cu skarn deposits. The Qiman Tagh area of Qinghai Province (QTQP), located in the Eastern Kunlun Orogen (EKO), provides a good opportunity to address this issue. Here, integrating new zircon U–Pb ages, trace elements and Hf isotopes from this study with published data, we constrain the sources of magma associated with Fe and Cu skarn deposits within the QTQP and discuss their role in controlling differences between Fe and Cu skarn deposits.Combined with published data, two discrete suites of the intrusions associated Fe and Cu skarn deposits have been recognized in the QTQP: (1) 245.1 ± 1.5 Ma granodiorite (related to a 245.5 ± 1.6 Ma Cu skarn deposit) has zircon εHf(t) values of −11.9 to −2.1; (2) 235–224 Ma monzonites, quartz monzonites, granodiorite porphyries, monzogranites, and granites associated with 234–225 Ma Fe skarn deposits are characterized by relatively high zircon εHf(t) values (−5.1 to +5.9). The Sr–Nd–Hf isotopic data suggest that the intrusions of Suite 1 and 2 were dominantly derived by partial melting of a Mesoproterozoic juvenile mafic lower crust. Suite 2 intrusions associated with Fe skarn deposits have more mantle components in their magma sources than rocks of Suite 1 that are related to a Cu skarn deposit. Furthermore, zircon εHf(t) values of intrusions associated with Fe and Cu skarn deposits in the QTQP show a negative correlation between mantle components in the magma sources and the contents of Cu and Zn in these deposits. Zircon trace elements indicate that the intrusions associated with Fe skarn deposits are relatively less oxidized than the rock associated with Cu skarn deposit in the QTQP, reflecting a positive correlation between crustal components in the magma sources and oxygen fugacity of the magmas. This indicates that different proportions of mantle and crustal materials in the magma sources may affect oxygen fugacity and Fe contents of the magmas, which possibly leads to the variations in metal associations between Fe and Cu skarn deposits in the QTQP. Zircon U–Pb ages, trace elements and Hf isotopic compositions, combined with geological, geochronological, and geochemical evidence, indicates that having different proportions of mantle components in the magma sources of intrusions associated with Fe and Cu skarn deposits is one of the most critical factors controlling differences in metal association between Fe and Cu skarn deposits.     

青海西部祁漫塔格地区主要矽卡岩铁多金属矿床成矿地质背景和矿化蚀变特征

青海西部祁漫塔格地区矽卡岩铁多金属矿床分布广泛,目前已成为中国西部最重要和最有找矿潜力的矽卡岩铁多金属成矿带.在大地构造上,该地区属东昆仑造山带;成矿主要与印支期(204～237Ma)闪长岩、花岗闪长岩和二长花岗岩有关;控矿地层包括蓟县系狼牙山组大理岩、硅质岩,奥陶系-志留系滩间山群大理岩、碎屑岩、硅质岩、中-基性火山岩和石炭系结晶灰岩、碎屑岩等.区内发育3类矽卡岩,即钙矽卡岩、镁矽卡岩和锰质矽卡岩,以前者为主.钙矽卡岩常伴生Fe、Cu、Mo(Pb,Zn)矿化,镁矽卡岩主要伴生Fe矿化,锰质矽卡岩则伴生Pb、Zn(Ag)矿化;矿石矿物组合多种多样,矿化具有一定的分带性.内接触带侵入岩广泛发育钾长石化,与矽卡岩类型一起构成该类矿床的重要找矿标志之一.     

矽卡岩型符山石玉—回龙玉石矿的发现及玉石特征

产于河南桐柏回龙地区的矽卡岩型符山石玉，通过镜下鉴定，能谱、光谱、电探测试分析，认为回龙玉是由多种矽卡岩矿物集合体组成的岩石。其中呈黄绿色色调均匀半透明的回龙玉，主要由符山石矿物集合体组成。矿物颗粒极细，质地细腻，硬度为７．比重３．２～３．４。研究后认为回龙玉矿是在高温低压的环境下，迅速冷凝后形成的特殊矽卡岩型矿床。     

一种未定名硫化物矿物——（Zn,Cu,Fe）S

未定名硫化物矿物是一个稀少矿物，它发现于内蒙古铅锌矿的钛卡岩矿床中。共生太物有黄铜矿、闪锌矿、方铅矿。它呈黑色，金属光泽，不透明，硬度为165－214kg/mm^2。反射铯为灰色微带蓝色，弱非均质性，深蓝－－黄褐色。化学成分（wt%）：S32.32、Cu6.46、Fe6.56、Zn54.29、Pb0.31、Cd0.2c、CO0.03（平均），分子式(Zn0.84Fe0.11Cu0.09)1.04S。X射线分析数据与闪锌矿相同，d值和晶胸参数比闪锌矿（含铁）的小，晶胞参数比人工合成闪锌矿的大。粉晶主要强线为3.108(100)、1.906(50)、1.628(30)、1.240(20)、1.103(20)。     

The large Bystrinskoe Cu–Au–Fe deposit (Eastern Trans-Baikal Region): Russia’s first example of a skarn–porphyry ore-forming system related to adakite

The Bystrinskoe skarn-porphyry Cu–Au–Fe deposit (Eastern Trans-Baikal Region) is confined to skarn zones, which were formed along the contact of granitoids referred to the Shakhtama intrusive complex (J_2–3), with terrigenous–carbonate sedimentary rocks. Commercial (Cu–Au–Fe ± W, Mo) mineralization was formed due to the regional postcollision development involving the intrusion of porphyritic granitoids, the derivatives of oxidized adakite highly magnesian magmas enriched in water, sulfur, and metals, which could develop under melting of garnet-bearing amphibolite in the mafic lower crustal arc.     

High‐temperature gold‐copper extraction with chloride flux in lava tubes of Tolbachik volcano (Kamchatka)

Subvolcanic environments in supra‐subduction zones are renowned for hosting epithermal deposits that often contain electrum and native gold, including bonanza examples. This study examined mineral assemblages and processes occurring in shallow‐crust volcanic settings using recent eruption (2012–2013) of the basaltic Tolbachik volcano in the Kamchatka arc. The Tolbachik eruptive system is characterized by an extensive system of lava tubes. After cessation of magma input, the tubes maintained the flow of hot oxidized gases that episodically interacted with the lava surfaces and sulphate‐chloride precipitates from volcanic gases on these surfaces. The gas‐rock interaction had strong pyrometamorphic effects that resulted in the formation of molten salt, oxidized (tenorite, hematite, Cu‐rich magnesioferrite) and skarn‐like silicate mineral assemblages. By analogy with experimental studies, we propose that a combination of these processes was responsible for extraction of metals from the basaltic wall rocks and deposition of Cu‐, Fe‐ and Cu‐Fe‐oxides and native gold.     

云南个旧塘子凹锡多金属矿床夕卡岩地质地球化学特征

从地质产状、矿物组合和岩石化学成分等方面探讨了个旧塘子凹接触带不同类型夕卡岩的特征。该夕卡岩带从内侧到外侧常具有辉石夕卡岩带和石榴子石夕卡岩带交替出现的现象，其岩石化学成分也相应地发生韵律变化，表现为在辉石夕卡岩带中SiO2和MgO含量较高，而在石榴子石夕卡岩带中CaO、TFe和Al2O3含量较高。认为夕卡岩带中的韵律变化一方面与被交代围岩中存在灰质白云岩和大理岩的互层带有关，另一方面与岩浆期后热液的渗滤交代作用有关。围岩中的灰质白云岩层被交代后形成辉石带，大理岩层被交代后形成石榴子石带。     

赞比亚西北省姆维尼伦加地区成矿地质特征及找矿远景研究

赞比亚西北省姆维尼伦加地区的金属矿产丰富,具有层控型铜-钴矿、热液型铜-钴矿、沉积型铁矿、矽卡岩型铁矿,与新生代火山岩及韧性剪切带有关的金矿等矿产。铜矿体主要赋存于新元古界加丹加超群下罗安组地层中,矿体主要受地层、穹窿构造、卢菲利安弧、前陆盆地控制。提出了具有良好找矿前景的4处成矿远景区。     

湖北大冶铜绿山铜铁矿床夕卡岩矿物学及碳氧硫同位素特征

湖北大冶铜绿山铜铁矿床是长江中下游西段鄂东南矿集区一个大型夕卡岩矿床。围岩为三叠系大理岩及白云质大理岩,决定了其发育丰富的钙镁质复合夕卡岩矿物组合,包括石榴子石、辉石、角闪石、绿帘石、金云母、绿泥石等。本文详细描述了夕卡岩不同阶段矿物的特征,并对矿物进行了电子探针分析(EPMA)及碳、氧、硫稳定同位素研究。结果表明石榴子石形成于三期,成分上属于钙铝—钙铁系列,且从早到晚具有从钙铝向钙铁榴石演化趋势,反映出成矿溶液由酸性向碱性演化。环带结构的石榴子石和绿帘石从核部到边部Fe含量增高,说明磁铁矿是在Fe浓度升高的碱性溶液中沉淀。辉石为透辉石。角闪石属于单斜角闪石中的钙质角闪石,包括透闪石,韭闪石和少量阳起石。矿物成分分析表明辉石和石榴子石的Mn/Fe值与矿化金属元素存在一定的联系。相对于钙质夕卡岩,镁质或含镁质夕卡岩是铜铁矿体交代的更有利岩石。矿床硫化物的δ34SV-CDT均为正值且变化范围较窄,介于0.6‰～3.8‰。成矿阶段方解石δ13CV-PDB变化于-2.9‰～6.3‰,δ18OV-SMOW变化于9.6‰～12.6‰,成矿后方解石的同位素值明显增大,δ13CV-PDB为-0.9‰～1.3‰,δ18OV-SMOW为15.2‰～17.3‰,趋向于围岩的同位素值。研究结果说明成矿阶段的硫和碳来自于深源或地幔,而成矿后期碳与地层发生明显的同位素交换反应。     

呼斯特岩体矽卡岩型铜铁矿成矿地质特征及找矿潜力分析

论述了呼斯特岩体成矿地质背景,以艾木斯呆依铜铁矿床为例,叙述矽卡岩型铜铁矿成矿地质特征,从岩体成矿地质条件、矿化特征和含矿性出发,指出岩体主攻矿床类型为矽卡岩型,主攻矿种为铁、铜、铅锌、钼、钨,找矿有利地段为岩体南东部凹陷部位,总体找矿潜力较大.     

In-situ LA–ICP-MS trace elemental analyses of magnetite: The Mesozoic Tengtie skarn Fe deposit in the Nanling Range,South China

The Nanling Range in South China hosts numerous world-class W–Sn deposits and some Fe deposits. The Mesozoic Tengtie Fe skarn deposit in the southern Nanling Range is contemporaneous with the regional Sn mineralization. The deposit is composed of numerous ore bodies along the contacts between the late Paleozoic or Mesozoic carbonate rocks and the Yanshanian Lianyang granitic complex. Interaction of the magma with hosting dolomitic limestone and limestone formed calcic (Ca-rich) and magnesian (Mg-rich) skarns, respectively. The Tengtie deposit has a paragenetic sequence of the prograde stage of anhydrous skarn minerals, followed by the retrograde stage of hydrous skarn minerals, and the final sulfide stage. Magnetite in the prograde and retrograde skarn stages is associated with diopside, garnet, chlorite, epidote, and phlogopite, whereas magnetite of the final stage is associated with chalcopyrite and pyrite. Massive magnetite ores crosscut by quartz and calcite veins are present mainly in the retrograde skarn stage. Laser ablation ICP-MS was used to determine trace elements of magnetite from different stages. Some magnetite grains have unusually high Ca, Na, K, and Si, possibly due to the presence of silicate mineral inclusions. Magnetite of the prograde stage has the highest Co contents, but that of the sulfide stage is extremely poor in Co which partitions in sulfides. Magnetite of magnesian skarns contains more Mg, Mn, and Al than that of calcic skarns, attributed to the interaction of the magma with compositionally different host rocks. Magnetite from calcic and magnesian skarns contains 6–185 ppm Sn and 61–1246 ppm Sn, respectively. The high Sn contents are not due to the presence of cassiterite inclusions which are not identified in magnetite. Instead, we believe that Sn resides in the magnetite structure. Regionally, intensive Mesozoic Sn mineralization in South China indicates that concurrent magmatic–hydrothermal fluids may be rich in Sn and contribute to the formation of high-Sn magnetite. Our study demonstrates that trace elements of magnetite can be a sensitive indicator for the skarn stages and wall-rock compositions, and as such, trace elemental chemistry of magnetite can be a potentially powerful fingerprint for sediment provenance and regional mineralization.     

保山金厂河大型铜铁多金属隐伏矿床

隐伏矿床位于金厂河隆起核部上、下两层矽卡岩化带中,垂向上Pb、Zn—Cu、Cu、Fe—Fe多层楼结构,水平上Fe、Cu—Pb、Zn—Cu分带。属热液交代矽卡岩型铜铁多金属矿床。     

矿精粉中关键金属元素赋存状态研究方法流程的建立:以长江中下游成矿带富钴硫矿精粉为例

长江中下游成矿带作为我国矿床学研究程度和矿产利用技术水平最高的成矿带之一,大部分矿床中除了主要成矿元素铜、金、铁和硫等,还伴生潜在可利用的关键金属资源镉、钴、硒、碲和铼等。由于目前矿山主要选矿回收铜、铁、硫、铅、锌、金和银等主要矿种,在不改变选矿工艺的条件下,矿山产品矿精粉中关键金属的分布特征和可利用性是当前关键金属资源利用的核心问题之一。本文对成矿带内玢岩型铁矿床、矽卡岩型铁矿床、矽卡岩型铁铜矿床、矽卡岩型铜金矿床、斑岩型铜金矿床和角砾岩筒型铜金矿床等六类矿床的矿山产品(铜金粉、硫精粉、铁精粉和金精粉)进行了系统化学成分分析,发现目前的矿山产品中关键金属元素含量普遍不高,但矽卡岩型铁矿床中的龙桥铁矿床硫精粉中富集钴,具有综合回收利用钴资源的潜力。在此基础上,本次工作利用综合矿物分析技术(TIMA),扫描电镜(SEM)和激光剥蚀-等离子体质谱仪(LA-ICP-MS)三种测试方法,系统开展了富钴硫精粉中钴的赋存状态研究。结果表明,龙桥硫精粉中钴矿物为辉砷钴矿、铁硫砷钴矿和硫铜钴矿,分别占硫精粉中总钴含量的9.93%、0.64%和0.01%。黄铁矿晶格中类质同象形式产出的钴占总量的81.97%,此外还有7.46%的钴赋存在其他矿物中。通过对比研究,初步建立了矿精粉中关键金属元素赋存状态的研究方法流程,为矿精粉中钴的回收利用提供了依据。     

鄂东南矿集区程潮大型矽卡岩铁矿的矿物学特征及其地质意义

程潮铁矿是鄂东南地区典型的矽卡岩铁矿,迄今为止对其矽卡岩矿物学特征研究较少。本文以程潮铁矿主要矽卡岩矿物为研究对象,利用电子探针技术对该矿矽卡岩矿物学特征进行了研究。电子探针分析结果表明:程潮铁矿石榴石和辉石分别以钙铁榴石和透辉石为主;角闪石主要是韭闪石,其次为铁韭闪石、透闪石、阳起石。其中,早期矽卡岩阶段的石榴石和辉石分别以钙铁榴石和透辉石为主;晚期脉状矽卡岩阶段的石榴石端员组分介于钙铁榴石和钙铝榴石之间,而辉石则相对于早期矽卡岩阶段的辉石更趋近于钙铁辉石端员。通过矽卡岩矿物学特征研究表明,花岗岩对矽卡岩和矿体的形成起到了重要作用。     

湖南宝山铜铅锌多金属矿床矿物学特征及其地质意义

宝山铜铅锌多金属矿床位于我国南岭成矿带中段北缘,是南岭成矿带中的重要类型之一。宝山矿床具有明显的水平分带性,即以花岗闪长斑岩为中心的铜钼矿化,周边是铅锌银矿化。本文通过对宝山铜铅锌多金属矿床中的石榴子石、透辉石、黄铁矿、闪锌矿等矿物进行矿物学研究及电子探针测试分析,归纳总结出：宝山铜铅锌多金属矿床成矿期次为矽卡岩阶段、退变质与氧化物阶段、硫化物阶段;矿床石榴石端员组分总体以钙铁榴石（23.48%~90.39%）为主,其次为钙铝榴石（5.81%~71.27%）;辉石的成分端员以透辉石（Di_61-95）为主,石榴子石成分和透辉石组分与世界上典型矽卡岩型铜矿的石榴子石和透辉石组分十分相似,属于典型的矽卡岩型铜矿床。从宝山铜铅锌多金属矿床硫化物中黄铁矿、闪锌矿矿物成分组成可以看出,该矿床硫化物为岩浆热液成因,并呈现出北东向比南西向成矿温度高的特征。