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PGE geochemistry of the Fengshan porphyry–skarn Cu–Mo deposit, Hubei Province, Eastern China
Abstract
The Fengshan Cu–Mo deposit is located in the western part of the Jiurui Cu–Au–Mo district in the Late Mesozoic Middle–Lower Yangtze River Metallogenic Belt (YRMB), Eastern China. The mineralization is spatially associated with the Fengshan granodiorite porphyry stock (149–138 Ma), where two types of ore bodies (porphyry, skarn) occur. The Fengshan deposit is located on the Yangtze Craton, i.e., in an intracontinental extensional environment, a geological setting not considered by previous studies of PGE abundance and distribution in porphyry systems. For the present investigation the PGE geochemistry of fourteen samples of the granodiorite, ore and flotation concentrates were determined by ICP-MS, after preconcentration by the Lead Fire Assay technique from large (30 g) samples. A maximum of 32 ppb Pd and 81.2 ppb Pt is reported for the molybdenum flotation concentrate. Cu, Au, Pt, Pd contents from flotation concentrate samples are almost 1 to 2 orders of magnitude higher than those reported for ore samples; this is especially true for the Pt content. Covariant diagrams of Cu and Mo with noble metals (Au, Ag, Pt and Pd) reveal weak correlation between Cu vs. Au, Ag, and Mo vs. Pt. Also, Au shows a slightly positive relationship with Pt and Pd.
... Ore deposits of platinum group elements (PGEs) have been reported from a wide range of geotectonic settings, although they are mainly associated with orthomagmatic sulfide mineralization during partial melting of depleted mantle (Cabri 2002;Economou-Eliopoulos 2010;Li and Ripley 2011;Barnes and Ripley 2016;Economou-Eliopoulos et al. 2017). However, previous studies showed that PGEs are also present in porphyry Cu deposits (PCDs), albeit at much lower concentrations: Pd contents reach hundreds of ppb in sulfides or flotation concentrates at some deposits (subeconomic: 0.03 g/ t), which make those PCDs more profitable to mine (Tarkian et al., 1991;Tarkian and Stribrny, 1999;Sotnikov et al., 2001;Kiousis et al., 2005;Turesebekov et al., 2005;Wang et al., 2009Wang et al., , 2014Eliopoulos et al., 2014;Economou-Eliopoulos et al., 2017;Plotinskaya et al., 2018). For example, the approximate reserve tonnage has been estimated to be 15 t Pd and 3.5 t Pt in the Skouries deposit, Greece, about Cordillera of British Columbia, (2) Balkan Peninsula, (3) Southeast Asia and (4) the Central Asia. ...
... In the Au vs. Pt and Au vs. Pd diagrams, it is shown that no obvious correlation is present between Au and Pt (Fig. 7a), while higher Au contents are related to higher Pd contents (Fig. 7b), which is consistent with the results of many other PCDs studies (Tarkian et al., 2003;Augé et al., 2005;Berzina and Korobeinikov, 2007;Pašava et al., 2010). In addition, Pd content is higher than Pt content in the samples, with Pd/Pt ratio > 1 (Table 2), which is consistent with the previous studies on PCDs in IAE by others (Augé et al., 2005;Berzina and Korobeinikov, 2007;Pašava et al., 2010;Sotnikov et al., 2001;Tarkian et al., 2003;Thompson et al., 2001) and the Fengshan PCD in IEE (Wang et al., 2014;this study). Therefore, we concluded that Pd is more enriched than other PGEs in PCDs. ...
... Abbreviations: Bt-biotite, Chl-chlorite; Ccp-chalcopyrite; Di-diopside; Ep-epidote; Grt-garnet; Kfs-K-feldspar; Mag-magnetite; Mb-dolomitic marble; Mol-molybdenite; Pl-plagioclase; Py-pyrite; Qz-quartz; Ser-sericite; Srp-serpentine. Fig. 9. Bar chart of Pt, Pd, Au and Cu contents in typical PCDs in IAE and IEE (data source: Tarkian and Stribrny 1999;Economou-Eliopoulos and Eliopoulos 2000;Tarkian et al. 2003;Augé et al. 2005;Wang et al. 2009Wang et al. , 2014. Location of these deposits is shown in Fig. 1. ...
The Tongshankou deposit is located in the southern part of the Edong district in the late Mesozoic Middle–Lower Yangtze River Metallogenic Belt, Eastern China. Alterations related to the porphyry and skarn mineralization are pervasive and intensive. Based on the ore metal contents, four groups of ores/mineralized-rocks are divided: Cu–Mo mineralized rock, Cu–Mo ore, Cu–Mo–W ore and Cu ore. The former two groups are porphyry related, and the latter two groups are skarn related. The average grades of Au, Pt and Pd in the ores are hundreds ppb, ∼2.3 ppb, and ∼10 ppb, respectively. While they are ∼340 ppb, ∼29.3 ppb, and ∼14.4 ppb in the flotation concentrations, respectively. Considering the similar geological characteristics and tectonic setting (intracontinental extensional environment (IEE)) for the Tongshankou and Fengshan PCDs, they are compared with the PCDs that formed in an island arc environment (IAE). Our data show that: (1) Pd and Pt contents of PCDs in IEE are much lower than those of PCDs in IAE; (2) Pd is more abundant than Pt in PCDs. Critical controlling factors for Pt–Pd enrichments in PCDs include: (1) Oxidized, mantle–derived parental magmas, which also explain why PCDs in IAE have higher Pt–Pd contents than PCDs in IEE; (2) Modes of PGE transport and precipitation (as chloride- or bisulfide- complexes) in late-stage hydrothermal fluids; (3) Behavior of sulfur during the magmatic evolution, since PGE and Au could be captured and preserved in magma due to sulfur undersaturation.
... There are few case studies on platinum group elements (PGE) mineralisation in skarns that have been documented to this day (Meinert et al., 2000 and references therein;Armitage et al., 2002;Wang et al., 2014). Some of the reasons may be due to the scarcity of platinum group metal (PGM) bearing skarns or, in case they do occur, they may be of less economic significance and, thus, are given little attention or just simply due to the lack of appropriate metallurgical techniques to extract them from their host rocks (White, 1994). ...
... Some of the reasons may be due to the scarcity of platinum group metal (PGM) bearing skarns or, in case they do occur, they may be of less economic significance and, thus, are given little attention or just simply due to the lack of appropriate metallurgical techniques to extract them from their host rocks (White, 1994). Over the past decades, research has shown that the genesis of skarns has always been related to magmatic activity (Armitage et al., 2002;Ciobanu and Cook, 2004;Calagari and Hosseinzadeh, 2006;Öztürk et al., 2005;Wang et al., 2014). During the skarn-forming process, elements and ores are redistributed during metasomatic and hydrothermal alteration processes which are, in turn, controlled by various physical, geochemical and geological factors (Armitage et al., 2002;Ferry et al., 2002;Gaeta et al., 2009;Mollaei et al., 2009;Wang et al., 2014). ...
... Over the past decades, research has shown that the genesis of skarns has always been related to magmatic activity (Armitage et al., 2002;Ciobanu and Cook, 2004;Calagari and Hosseinzadeh, 2006;Öztürk et al., 2005;Wang et al., 2014). During the skarn-forming process, elements and ores are redistributed during metasomatic and hydrothermal alteration processes which are, in turn, controlled by various physical, geochemical and geological factors (Armitage et al., 2002;Ferry et al., 2002;Gaeta et al., 2009;Mollaei et al., 2009;Wang et al., 2014). ...
The skarns in drill core SS330, extracted at the contact zone between the Platreef magmas from the Northern limb of the Bushveld Igneous Complex and the country rock dolomite, are investigated to understand processes that were involved in their genesis and have influenced the distribution of the platinum group element (PGE) mineralisation.
The skarn lithologies are diopside-rich rocks (i.e. clinopyroxenite and feldspathic clinopyroxenite), and forsterite-rich rocks (olivine clinopyroxenite and serpentinite). The geochemical data show that the skarns were formed by metasomatic transformations of dolomite; such that Ca was pivotal in the genesis of diopside-rich rocks whereas Mg played a major role in the genesis of forsterite-rich rocks when compared to magmatic rocks from the Platreef. The metasomatic fluids involved in the skarn- and reef-forming processes were Si–Al–Fe-rich with variable amounts of the base metal sulphide (BMS) elements (e.g. Cu, Ni, Zn, Co) and originated from three mafic magmas. It is suggested that the fluids evolved along three crystallisation trends (i.e. upwards, downwards and inwards) leading to SiO2, Na2O, Fe2O3, Cu, Ni, Pt and Pd enrichments and Al2O3 depletion which resulted in the formation of the PGE and PGE-BMS reefs. On these bases, the proposed indices (e.g. SiO2/Al2O3, Na2O/Al2O3, Fe2O3/Al2O3, Si+Na+Fe/Al) can be used as lithogeochemical vectors to locate the position of the PGE
reefs downhole in drill core SS330.
... Some previous reports show the PGE enrichment in porphyry Cu deposits in China: 3 to 50 ppb in ore samples from Dexing porphyry Cu deposit; 3.4 t of PGE prospective reserves in Yulong porphyry Cu deposit (Wang et al., 2014;Xiang and Ru, 1999). And some porphyryskarn deposits in the Middle-Lower Yangtze Metallogenic belt (MLYMB) also have both Pd and Pt enrichments (Gu and Chen, 1993;Tan, 2001Tan, , 2002. ...
... ppb, respectively. To generate elevated Pt and Pd contents in porphyry Cu deposits, enriched mantle and oxidized alkaline magmas are the prerequisites (Wang et al., 2014). PGE-enriched materials in the mantle can supply PGE to the porphyry stocks or hydrothermal systems, and the oxidized alkaline arc magmas allow the noble metals to remain in the magmas (Mclnnes and Cameron, 1994;Wang et al., 2014). ...
... To generate elevated Pt and Pd contents in porphyry Cu deposits, enriched mantle and oxidized alkaline magmas are the prerequisites (Wang et al., 2014). PGE-enriched materials in the mantle can supply PGE to the porphyry stocks or hydrothermal systems, and the oxidized alkaline arc magmas allow the noble metals to remain in the magmas (Mclnnes and Cameron, 1994;Wang et al., 2014). The source magma for Fenghuanghshan granodiorite is associated with a moderate to high oxygen fugacity. ...
The Fenghuangshan copper–gold deposit, located in the Tongling ore cluster field along the Lower Yangtze metallogenic belt (LYRB) in eastern China, mainly consist of skarn ores hosted in granodiorite. U–Pb dating of magmatic zircons from Fenghuangshan granodiorite yields a weighted mean 206Pb/238U age of 143.1 ± 1.6 Ma. Five molybdenite samples collected in the Fenghuangshan deposit yield a Re–Os isochron age of 141.7 ± 0.8 Ma, demonstrating that the ore formation event is coeval with the Fenghuangshan granodiorite intrusion. The magmatic zircon ƐHf(T) values vary from − 12.0 to − 28.3, corresponding two-stage Hf model ages between 1.6 Ga to 2.4 Ga. Geochemical and isotopic signatures suggest that the Fenghuangshan granodiorite resembles adakite, which was derived from partial melting of the subducted oceanic crust towards LYRB during the early Cretaceous. The occurrence of inherited zircons shows the intrusive granodiorite was assimilated by old crustal materials during its emplacement. The biotite thermobarometry, zircon Ce(IV)/Ce(III) ratios and Eu anomalies coincidently demonstrate that the magma source of granodiorite was under high to moderate oxidized condition, conducive to Cu–Au mineralization. The sulfide ores in Fenghuangshan deposit are enriched in Pd and Pt, which could also be a consequence of the high oxidized magma source. The high Re abundance in molybdenite and platinum group element (PGE) contents of sulfide ores suggest that the ore-forming materials are characterized by mixed sources from the mantle and crust, and were slightly affected by hydrothermal alteration.
... In the magmatic stage, distribution of platinum-group elements (PGEs) and Cu is controlled by the partition coefficients between sulfide and silicate melt, silicate mineral and other non-sulfide phases (Barnes and Maier, 1999;Fleet et al., 1991Fleet et al., , 1999Naldrett, 2004;Sattari et al., 2002). In the hydrothermal stage, PGEs would be preferably enriched in hot oxidized brines as chloride, hydroxide and sulfate complexes (Azaroual et al., 2001;Gammons, 1995Gammons, , 1996Gammons and Bloom, 1993;Gammons et al., 1992;Hanley, 2005; Ore Geology Reviews 66 (2015) 403-421 Mountain and Wood, 1988;Sassani and Shock, 1998;Wang et al., 2014) or in reduced sulfur-rich fluids as bisulfide complexes (Barnes and Liu, 2012;Gammons and Bloom, 1993;Mountain and Wood, 1988;Pan and Wood, 1994;Wood et al., 1994). However, Cu in magmatichydrothermal systems can be transported as hydrated copper-chloride or chloride complexes (Archibald et al., 2002;Hack and Mavrogenes, 2006;Liu and McPhail, 2005), which are sensitive to temperature, pressure, pH values and NaCl contents but not oxidization state. ...
... In previous studies, lead fire assay (Economou- Eliopoulos and Eliopoulos, 2000) and nickel sulfide (NiS) fire assay (Eliopoulos and Economou-Eliopoulos, 1991;Tarkian and Stribrny, 1999;Wang et al., 2014) were commonly used for the determination of PGEs and Au in porphyry rocks. ...
... In a few examples, the PGE have been a valuable byproduct of Cu-Au production (Peterson, 1993;Economou-Eliopoulos, 2005;Pašava et al., 2010;Eliopoulos et al., 2014). Numerous studies have described the geochemistry and mineralogy of the PGE in porphyry deposits in the North American Cordillera (McMillan, 1991;Barrie, 1993;Peterson, 1993;Schroeter, 1995;Economou-Eliopoulos and Eliopoulos, 1999;Nixon and LaFlamme, 2002;Thompson et al., 2002;Nixon, 2004;LeFort, 2009;MacKenzie, 2009;Pass et al., 2009;Pass, 2010;LeFort et al., 2011;Bath et al., 2014;Logan and Mihalynuk, 2014;Micko et al., 2014;Hanley et al., 2021) and the European Alpine orogenic belt (Herrington et al., 1998;Economou-Eliopoulos and Eliopoulos, 1999;Tarkian and Stribrny, 1999;Strashimirov et al., 2002;Kehayov et al., 2003;Tarkian et al., 2003;von Quadt et al., 2005;Augé et al., 2005;Economou-Eliopoulos, 2005;Eliopoulos et al., 2014;McFall et al., 2016;2018); and the Ural-Mongolian metallogenic belt (e.g., Economou-Eliopoulos and Eliopoulos, 1999;Sotnikov et al., 2001;Economou-Eliopoulos, 2005;Berzina et al., 2007;Wang et al., 2014;Plotinskaya et al., 2018). A few deposits with PGE enrichments have also been noted in the Western Pacific margin (Tarkian and Koopmann, 1995;Economou-Eliopoulos and Eliopoulos, 1999;Economou-Eliopoulos, 2005;Eliopoulos et al., 2014); and the South American Cordillera (Crespo et al., 2018). ...
The second part of this article can be found here: 10.3389/feart.2023.819109 (DOI). At the late Triassic New Afton alkalic porphyry Cu-Au deposit (British Columbia, Canada), pyrite is a widely distributed minor sulfide phase within hypogene ore where it predates Cu mineralization and hosts significant concentrations of Pd and Pt. Here we characterize pyrite major, minor and trace element composition by EPMA and LA-ICP-MS, and S isotopes (bulk pyrite and in situ SIMS in individual growth zones) to elucidate compositional variations at different stages of pyrite growth with respect to PGE deposition. At least two cycles of zoned Co-Ni-Pd-Pt-Se-As co-enrichment are recorded over two stages of pyrite growth at the New Afton deposit. Concentrations of Co (up to ∼5.5 wt%; highest observed in any reported ore-forming system) and Ni (up to 1 wt%) overlap with pyrite from mafic-ultramafic platinum-group element (PGE) deposits, iron oxide±apatite and iron oxide-copper-gold deposits (IOA-IOCG), and mantle peridotite-associated base metal exhalative deposits. In early hypogene (type I) pyrite, high Pt (up to ∼24 ppm) occurs in crystal cores that have high Co/Ni ratio (>∼7), high Co (>∼ 1 wt%) and are poor in Ni, Se, and As. With progressive growth, early hypogene pyrite rims and late hypogene (type II) cores record an initial Ni-Pd-As-Se (±Co) co-enrichment stage, followed by oscillations in composition (from “barren” to variably Co-Ni-Pd-Pt-As-Se-enriched). Pd in pyrite (up to ∼70 ppm) is inversely correlated to Co/Ni ratio, being enriched when Co/Ni < ∼7 and Ni > ∼1000 ppm. The highest levels of Pd enrichment occur in the most Ni- and Se-enriched growth zones. The transition from early, high Co/Ni (Pt-enriched) to later, low Co/Ni (Pd-enriched) growth zones is accompanied by a decrease in pyrite δ³⁴SVCDT of up to ∼7‰ (4‰ range in single grains) with a total range in composition measured between −5.5‰ and +1.4‰. Subsequent to the shift to lower values, overgrowths of high Co/Ni pyrite formed with values of δ³⁴SVCDT similar to the earliest Co-Pt-rich growth zones. Some combination of fluctuations in temperature and oxygen fugacity related to episodic cooling and hydrothermal recharge involving new pulses of metal-rich magmatic fluids is required to explain the observed metal enrichment patterns and variations in S isotope values. Co-Ni-rich pyrite may be a valuable exploration vector to PGE enrichment in porphyry deposits.
... The Edong ore district, on the western margin of Middle-Lower Yangtze River metallogenic belt, is characterized by late Mesozoic porphyry-skarn Cu-Au-Mo-Fe deposits with reports of Pd, Pt, Se and Te enrichments (Gu and Chen, 1993;Wang et al., 2014;Xie et al., 2019a;Han et al., 2019). The Tongshankou deposit, as a representative porphyry-skarn Cu-Mo system in the region, has been reported to contain the highest Pd + Pt concentration of 20.8 ppb based on bulk ore assay results of 12 samples (Wang et al., 2020). ...
... f gold in classic Carlin-type deposits (Hofstra and Cline, 2000). The Cu-Au skarn deposits at Fengshan have peripheral replacement zones of Pb, Zn, Au, and Ag mineralization (Peters et al., 2002), and their deposit geology and skarn mineralogy and the nature of ore-bearing intrusions have been studied extensively (Zhao et al., 1999;Xie et al., 2008M.F. Wang et al., 2014). However, the genesis of the carbonate-hosted Au deposits remains unclear, and little is known about the link between these Au deposits and Cu-Au skarns (Fig. 2). ...
Carbonate-hosted Au deposits (12 million tonnes at 5.0 g/t Au) are located less than 1.5 km away from Cu-Au skarn deposits in the Fengshan area, Middle-Lower Yangtze River metallogenic belt, eastern China. The skarn deposits occur in the contact zones of late Mesozoic granodiorite porphyry intrusions. Bismuth tellurides and coloradoite (HgTe) occur in Cu-Au skarn and peripheral Au-As ores, respectively, whereas tellurides, including coloradoite, and lorandite (TlAsS2) are present in carbonate-hosted Au ores outside the marble front. New zircon U-Pb ages indicate that the granodiorite porphyry intrusions spatially related to both Cu-Au skarn and carbonate-hosted Au deposits were emplaced between 149.9 ± 1.3 and 145.9 ± 0.7 Ma, which overlaps with molybdenite Re-Os ages of 149.1 ± 2.1 to 145.4 ± 2.9 Ma from the Cu-Au skarn deposits. Sulfur isotope compositions of sulfide minerals from the Cu-Au skarn deposits (δ34S = –2.5 to 6.4) are similar to those from carbonate-hosted Au deposits (δ34S = –4.8 to 2.6), suggesting a similar magmatic source of sulfur. Geologic, mineralogical, and sulfur isotope evidence collectively indicate that the carbonate-hosted Au deposits are the distal product of Cu-Au skarn mineralization rather than Carlin-type Au deposits, as has been previously suggested. This study proposes a genetic model to illustrate possible linkages between oxidized Cu-Au skarn deposits (associated with oxidized magmas) and carbonate-hosted Au deposits, which may have important implications for Au deposits in the more distal parts of Cu-Au skarn systems in the Middle-Lower Yangtze River metallogenic belt and elsewhere.
... 长江中下游多金属成矿带是中国东部最著名 的成矿带之一， 鄂东南矿集区位于成矿带西段， 矿 集区内以铁、 铜矿产为主， 其次为金、 钨、 钼等， 矿床 类型主要有矽卡岩型和矽卡岩-斑岩复合型 [1][2][3][4][5][6] 。前 人对鄂东南矿集区的矿床成矿时代、 成矿地球动力 学背景、 成矿岩体特征、 区域成矿模型等进行了大 量研究 [7][8][9][10][11] 。铁山铁铜矿床在 20 世纪 50 年代已经开 始大规模的勘探开采工作， 许多学者已对其矿床地 质特征、 成矿时代、 成矿物质来源、 矿床成因、 控矿 构造、 蚀变与矿化的关系等进行了大量深入的研 究 [6,[11][12][13][14][15] ， 研究程度非常高。然而， 长期以来并无学 者对铁山铁铜矿床的成矿流体开展过细致深入的 研究。众所周知， 热液矿床形成过程中流体的组 成、 运移、 演化及矿质沉淀机制是矿床学研究的重 点和难点 [16][17][18] ， 目前而言， 流体包裹体是研究成矿流 体性质、 揭示矿质迁移和沉淀富集机制最直接和有 效的方法 [19][20] 。近年来， 矽卡岩矿床中流体包裹体 的研究多集中在传统冷热台测定均一温度、 盐度、 计算成矿流体密度、 成矿压力， 估算成矿深度 [21][22] ； 借助激光拉曼方法对流体包裹体气相、 液相、 子矿 物进行半定量分析 [23][24][25] ； 采用四级质谱和离子色谱 方法对群体包裹体气、 液相成分进行定量分析 [26][27][28] ； 利 用 LA-ICP-MS 原 位 微 区 的 分 析 技 术 对 体 积 较大的流体包裹体进行高精度的成分分析 [29][30][31] (1) 石榴子石中的流体包裹体 [82] ， 造成溶液 pH 值上升， 直接破坏 了 Na-Fe-Cl 络合物的稳定性， 致使 Fe 质发生卸载 图 11 铁山铁铜矿床成矿流体成矿温度-pH 演化图解 Fig. 11 The evolution diagram of ore-forming temperature and pH of ore-forming fluids from the Tieshan Fe-Cu deposit ...
Based on petrographic observations of garnet and tremolite collected from the Tieshan Fe-Cu deposit, the authors found that the primary fluid inclusions are generally of three types: gaseous inclusions, liquid inclusions and halite daughter mineral-bearing three-phase inclusion. According to temperature measurement results, the homogenization temperatures at the prograde skarn stage range from 499.2℃ to 594.8℃, the fluid salinity peak values range from 17.3 %NaCl to 19.5 %NaCl, the densities range from 0.45g/cm³ to 0.62g/cm3, and the pressure ranges from 58.0×10⁶ Pa to 90.6×10⁶ Pa; the homogenization temperatures at the retrograde alteration stage range from 356.2℃ to 428.6℃, the fluid salinity peak values range from 7.2%Nacl to 15.5%NaCl, the densities range from 0.52g/ cm3 to 0.83g/cm³, the metallogenic pressure ranges from 23.8 × 10⁶ Pa to 29.7 × 10⁶ Pa, and the metallogenic depth ranges from 0.90km to 1.12km with an average of 0.95km. These data indicate that the ore-forming fluid of the Tieshan Fe-Cu deposit has the characteristics of high temperature, moderate-low salinity, and low density. Therefore, the Tieshan Fe-Cu deposit is an epithermal skarn deposit. Composition analysis of grouped fluid inclusions indicates that gaseous composition is dominated by H2O and CO2, followed by small amounts of CH4, C2H6, N2 and H2S, the cations of liquid composition are dominated by Na⁺, Ca²⁺ and K⁺, and the anions are dominated by SO4²⁻and Cl⁻. The results show that Cl⁻, SO4²⁻ and carbonate complexes played an important role in migration and enrichment of iron. The mixing of fluids of different origins and the evolution of pH might have been the dominant enrichment and precipitation mechanism of the Tieshan Fe-Cu deposit.
... The basement is covered by Paleoproterozoic to Neoproterozoic volcanosedimentary rocks including calc-alkaline basalts, rhyolitic rocks and marine carbonate and clastic sedimentary rocks that can be metamorphosed to schists and gneisses (Chang et al., 1991). The ages of the Yanshanian igneous rocks in the MLYRMB range from 150 to 120 Ma (Mao et al., 2006;Hu and Jiang, 2010;Yang et al., 2011;Jiang et al., 2013;Pang et al., 2014, Wang et al., 2014. ...
The platinum-group elements (PGE) are enriched in many alkalic porphyry deposits in the Canadian Cordillera, and these have the potential to be classified and extracted as byproducts of Cu-Au mining, constituting important secondary (“unconventional”) PGE sources for Canada. However, studies dedicated to PGE in porphyry settings in Canada are uncommon, and a unified predictive ore deposit model is lacking. This chapter provides new constraints on the mineralogical sites of deposition and origin of PGE at two alkalic porphyry deposits within the Canadian Cordillera: Afton, which is estimated to contain ~ 12 t Pd+Pt, and Mt. Milligan, which is estimated to contain ~ 30 t Pd+Pt.
In these deposits and other alkalic porphyry systems in British Columbia, PGE content is not always correlated with Cu and Au content, in particular at high metal concentrations. This suggests that, whereas the sites of deposition maybe spatially coincident, the timing (and possibly source) of PGE and Cu/Au are distinct, requiring multiple stages of ore deposition to explain the overall distribution of PGE and other chalcophile metals.
One stage of PGE enrichment involved the precipitation of discrete mineral phases containing As, Sb, Te, and Hg (dominantly temagamite, kotulskite, merenskyite, mertieite-II/isomertieite, and sperrylite), but these phases are late in the paragenesis and host only a minor proportion of the bulk rock Pd and Pt. Accessory Co-Ni-As–rich pyrite, commonly pre-dating Cu-Au deposition, is an important repository of PGE, containing high dissolved concentrations of Pd (up to ~ 40 ppm) and Pt (up to ~ 1 ppm) and controlling the Pd/Pt ratio of mineralization. In pyrite, Pd deposition was coeval with Ni enrichment, and Pt deposition was coeval with Co enrichment; the Co/Ni ratio of pyrite controlled the Pd/Pt ratio of pyrite. Fluid inclusion studies suggest that PGE deposition was tied to boiling (at Afton) or fluid mixing (at Mt. Milligan), processes that would promote the deposition of Pd and Pt, carried as bisulfide (in more reduced systems) or chloride complexes (in oxidized, acidic fluids most typical of alkalic PGE environments).
The mineral chemistry of the pyrite suggests that introduction of PGE into the porphyry environment required fluid or melt input from a distinct mafic magmatic source, with similarities in pyrite chemistry to mafic-ultramafic Ni-Cu-PGE, IOCG (Fe-oxide-Cu-Au), and mantle peridotite-related Cu-Co-Ni deposits. The unusual association of PGE and pyrite may have led to misrepresentation of PGE grades in the literature for porphyry deposits. Further, it calls to question the representativeness of the global inventory of PGE in porphyry settings if sampling programs focused on Cu-Au-rich domains and PGE were not analyzed routinely. Recognition of Co-Ni-As−rich pyrites in heavy mineral separates or thin section (detectable by routine microprobe analysis) may allow discrimination of PGE-barren from PGE-rich systems in the Canadian Cordillera since only the Co-Ni-As−rich pyrite is associated with significant PGE enrichment.
Porphyry Cu can contain significant concentrations of platinum-group elements (PGE: Os, Ir, Ru, Rh, Pt, Pd). In this study, we provide a comprehensive in situ analysis of noble metals (PGE, Au, Ag) for (Cu-Fe)-rich sulfides from the Elatsite, one of the world’s PGE-richest porphyry Cu deposits. These data, acquired using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), indicate that Pd was concentrated in all the (Cu-Fe)-rich sulfides at ppm-levels, with higher values in pyrite (~ 6 ppm) formed at the latest epithermal stage (i.e., quartz–galena–sphalerite assemblage) than in bornite and chalcopyrite (<5 ppm) from the hypogene quartz–magnetite–bornite–chalcopyrite ores. Likewise, Au is significantly more concentrated in pyrite (~ 5 ppm) than in the (Cu-Fe)-rich sulfides (≤0.08 ppm). In contrast, Ag reaches hundreds of ppm in pyrite and bornite (~ 240 ppm) but is in much lesser amounts in chalcopyrite (< 25 ppm). The inspection of the time-resolved spectra collected during LA-IPC-MS analyses indicate that noble metals are present in the sulfides in two forms: (1) structurally bound (i.e., solid solution) in the lattice of sulfides and, (2) as nano- to micron-sized inclusions (Pd-Te and Au). These observations are further confirmed by careful investigations of the PGE-rich (Cu-Fe)-rich sulfides by combining high-spatial resolution of field emission scanning electron microscope (FESEM) and focused ion beam and high-resolution transmission electron microscopy (FIB/HRTEM). A typical Pd-bearing mineral includes the composition PdTe2 close to the ideal merenskyite but with a distinct crystallographic structure, whereas Au is mainly found as native element. Our detailed mineralogical study coupled with previous knowledge on noble-metal inclusions in the studied ores reveals that noble metal enrichment in the Elatsite porphyry ores was mainly precipitated from droplets of Au-Pd-Ag telluride melt (s) entrained in the high-temperature hydrothermal fluid. These telluride melts could separate at the time of fluid unmixing from the silicate magma or already be present in the latter either derived from deep-seated crustal or mantle sources. Significant enrichment in Pd and Au (the latter correlated with As) in low-temperature pyrite is interpreted as remobilization of these noble metals from pre-existing hypogene ores during the epithermal overprinting.
This report contains data on the Re content of molybdenite samples collected from a wide variety of mineral deposits in Canada and a few deposits from outside Canada. Estimates of Re resources based on this data indicate that porphyry Cu, Cu-Mo and Cu-Au deposits have the most resources and the greatest potential for Re production in Canada, primarily as a by-product of Mo production. Other deposit types with potential for Re production as a by-product include sediment-hosted Cu and U deposits, PGE-rich Ni-Cu deposits associated with mafic and ultramafic rocks and vein deposits with high Re grades.
The Fuzishan Cu-Mo deposit is located in the Edong district of the Middle-Lower Yangtze River Metallogenic Belt, China. The orebodies mainly occurred as lenticular and bedded shapes in the skarn zone between the Lower Permian Qixia Formation carbonate rocks and the quartz diorite. Four paragenetic stages have been recognized based on petrographic observations: (1) prograde skarn stage, (2) retrograde skarn stage, (3) quartz-sulfide stage, and (4) carbonate stage. Six fluid inclusion types were recognized: S 1 (vapor + liquid + halite ± other daughter minerals), S 2 (vapor + liquid + daughter minerals except halite), L V (rich liquid + vapor), V L (rich vapor + liquid), V (vapor), and L (liquid) types. Fluid inclusion studies show distinct variations in composition, final homogenization temperature, and salinity in four stages. Daughter minerals of the primary fluid inclusions include chalcopyrite, molybdenite, hematite, anhydrite, calcite, and halite in the prograde skarn stage and hematite, calcite, and sulfide (?) in the retrograde skarn stage. No daughter minerals occurred in the quartz-sulfide and carbonate stages. Final homogenization temperatures recorded in these stages are from 405 to >550°C, from 212 to 498°C, from 150 to 485°C, and from 89 to 223°C, respectively, while salinities are from 3.7 to 42.5, from 2.6 to 18.5, from 2.2 to 17.9, and from 0.2 to 11.5 wt.% NaCl equivalent, respectively. The coexisting V L and S 1 type fluid inclusions show similar homogenization temperature of 550 to about 650°C in the prograde skarn stage, indicating that immiscibility occurred at lithostatic pressure of 700 bars to perhaps 1000 bars, corresponding to a depth of 2.6 km to about 3.7 km. The coeval V L and L V types fluid inclusions with homogenization temperature of 350 to 400°C in the late retrograde skarn and quartz-sulfide stages suggest that boiling occurred under hydrostatic pressure of 150 to 280 bars, equivalent to a depth of 1.5 to 2.8 km. Mo mineralization in the retrograde stage predated Cu mineralization which mainly occurred in the quartz-sulfide stage. Fluid compositions indicate that ore-forming fluid has high f O 2 and rich Cu and Mo concentration in the early stage, while relatively lower f O 2 and poor Cu and Mo concentration in the middle to late stages. Microthermometric data show a decreasing trend in temperature and salinity in the fluid evolution process. Decreasing temperature and boiling event may be the main factors that control the ore precipitation.
The Skouries deposit is a platinum-group element (PGE) enriched Cu-Au porphyry system located in the Chalkidiki peninsula, Greece, with associated Ag, Bi and Te enrichment. The deposit is hosted by multiple porphyritic monzonite and syenite intrusions, which originated from a magma chamber at depth. An initial quartz monzonite porphyritic intrusion contains a quartz–magnetite ± chalcopyrite–pyrite vein stockwork with intense potassic alteration. The quartz monzonite intrusion is cross cut by a set of syenite and mafic porphyry dykes and quartz–chalcopyrite–bornite ± magnetite veins which host the majority of the Cu and Au mineralisation. Late stage quartz–pyrite veins, with associated phyllic alteration crosscut all previous vein generations. Electron microprobe and scanning electron microscopy shows that the PGE are hosted by platinum-group minerals (PGM) in the quartz-chalcopyrite–bornite ± magnetite veins and within potassic alteration assemblages. The PGE mineralisation in Skouries is therefore part of the main high temperature hypogene mineralisation event. Platinum-group minerals at Skouries include: sopcheite [Ag4Pd3Te4], merenskyite [(Pd,Pt)(Te,Bi)2] and kotulskite [Pd(Te,Bi)], with rare telargpalite [(Pd,Ag)3Te], isomertieite [Pd11Sb2As2], naldrettite [Pd2Sb], testibiopalladite [PdTe(Sb,Te)] and sobolevskite [PdBi]. The most common platinum-group mineral is sopcheite. The PGM in Skouries are small, 52 µm² on average, and occur as spherical grains on the boundaries between sulphides and silicates, and as inclusions within hydrothermal quartz and sulphides. These observations support a “semi-metal collector model” whereby an immiscible Bi-Te melt acts as a collector for PGE and other precious metals in high temperature hydrothermal fluids. This mechanism would allow the formation of PGM in porphyries without Pt and Pd fluid saturation.
The concentrations and ratios of plant carbon (C), nitrogen (N), and phosphorus (P) are powerful indicators of various ecological processes. The effect of elevation on the ecological stoichiometric characteristics of plants is presently unclear. Here, we examined the C:N:P ratios of the wetland sedge, Carex brevicuspis, along a small-scale elevation gradient and their relationships with the physicochemical characteristics of soil and inundation time of the Dongting Lake wetlands, China. The soil water content and inundation time decreased, whereas the soil bulk density increased with increasing elevation. The height, density, coverage, and aboveground biomass of plants and the organic matter content and total N and P concentrations of the soil increased initially, and then decreased with increasing elevation. The total foliar C concentration and the foliar C:N, C:P, and N:P ratios increased, whereas the total foliar N and P concentrations decreased with increasing elevation. The canonical correspondence analysis (CCA) indicated that the soil water content and inundation time were the primary factors affecting the ecological stoichiometric characteristics of C. brevicuspis. The total foliar C concentration and the C:N, C:P, and N:P ratios decreased, but the total foliar N and P concentrations increased with increasing soil water content and inundation time. Our findings highlight the effects of elevation on plant growth and stoichiometric characteristics, which are applicable to the conservation and management of the wetlands dominated with C. brevicuspis.
The Tieshan Fe–Cu deposit is located in the Edong district, which represents the westernmost and largest region within the Middle–Lower Yangtze River Metallogenic Belt (YRMB), Eastern China. Skarn Fe–Cu mineralization is spatially associated with the Tieshan pluton, which intruded carbonates of the Lower Triassic Daye Formation. Ore bodies are predominantly located along the contact between the diorite or quartz diorite and marbles/dolomitic marbles. This study investigates the mineral chemistry of magnetite in different skarn ore bodies. The contrasting composition of magnetite obtained are used to suggest different mechanisms of formation for magnetite in the western and eastern part of the Tieshan Fe–Cu deposit. A total of 178 grains of magnetite from four magnetite ore samples are analyzed by LA–ICP–MS, indicating a wide range of trace element contents, such as V (13.61–542.36 ppm), Cr (0.003–383.96 ppm), Co (11.12–187.55 ppm) and Ni (0.19–147.41 ppm), etc. The Ti/V ratio of magnetite from the Xiangbishan (western part of the Tieshan deposit) and Jianshan ore body (eastern part of the Tieshan deposit) ranges from 1.32 to 5.24, and 1.31 to 10.34, respectively, indicating a relatively reduced depositional environment in the Xiangbishan ore body. Incorporation of Ti and Al in magnetite are temperature dependent, which hence propose that the temperature of hydrothermal fluid from the Jianshan ore body (Al = 3747–9648 ppm, with 6381 ppm as an average; Ti = 381.7–952.0 ppm, with 628.2 ppm as an average) was higher than the Xiangbishan ore body (Al = 2011–11122 ppm, with 5997 ppm as an average, Ti = 302.5–734.8, with 530.8 ppm as an average), indicating a down–temperature precipitation trend from the Jianshan ore body to the Xiangbishan ore body. In addition, in the Ca + Al + Mn versus Ti + V diagram, magnetite is plotted in the skarn field, consideration with the ternary diagram of TiO2–Al2O3–MgO, proposing that the magnetite ores are formed by replacement, instead of directly crystallized from iron oxide melts, which provide a better understanding regarding the composition of ore fluids and processes responsible for Fe mineralization in the Tieshan Fe–Cu deposit.
Child maltreatment negatively affects children's development and wellbeing. This study investigated the associations between child maltreatment (i.e., emotional neglect, emotional abuse, and physical abuse) and interpersonal functioning, including parent-child relationship, teacher-student relationship, and peer relationships among children with oppositional defiant disorder (ODD). A total of 256 children with ODD and their parents and class master teachers from Mainland China completed questionnaires. Results showed a negative correlation between emotional abuse (parent-reported) and children's interpersonal relationships with parents, teachers, and peers. Emotional neglect and physical abuse were related to poor parent-child relationships. Latent profile analysis revealed three profiles of child maltreatment among children with ODD. ODD children with more severe levels of one type of maltreatment were also more likely to have experienced severe levels of other types of maltreatment. Children with ODD who were in the group of high maltreatment had the poorest quality of interpersonal relationships. Our findings highlight the urgent need to prevent child maltreatment and promote more positive parenting in families with ODD children.
The Skouries porphyry deposit is located in Chalkidiki peninsula, Serbo-Macedonian metallogenic belt. It is hosted in alkaline rocks which intruded in Vertiskos units in Paleogene- Neogene. The distribution of intrusions is controlled by Stratoni-Varvara and Megali Panaghia-Gomati deep fault. The deposit contains more than 5.2×108t copper with Cu 0.5%, Au 0.8×10-6, Pd110×10-9 and Pt 17×10-9. Mineralization of the deposit mainly consists of vein type, stockwork type and dissemination type, and occurs in the altered porphyry and country rocks. Ore minerals mainly include chalcopyrite, bornite, pyrite and magnetite. Alterations related to mineralization are mainly potassic alteration, propylitization and silicification. Considering the consistency of U-Pb age of zircon and Ar-Ar age of whole rock, and the characteristics of petrology and geochemistry, it is concluded that the emplacement of the Paleogene-Neogene intrusions played an important role in the ore-forming process, and the deposit was formed at 19Ma. It is worth noticing that the deposit has high content of Pd-Pt. And there are also some reports on PGE enrichment in porphyry Cu deposits in China, such as Dexing and Yulong. Therefore, the investigation of the characteristics and the metallogenic regularity of the Skouries deposit summarized in this paper will offer valuable reference for the exploration of the similar deposits in China.
We present the preliminary results of an investigation into Tertiary hydrothermal alteration of ultramafic rocks from the Semail ophiolite, Oman. We infer a Tertiary regional thermal event manifested in basaltic and basanitic dyke intrusion, extensional faulting and fluid flow. New data include field and mineralogical observations, geochemical analyses and geochemical models of alteration processes. Two types of hydrothermal alteration are documented. Carbonate-altered serpentinite is mineralogically and chemically similar to travertine that is abundant in northern Oman. The second alteration type is silica-iron oxide also known locally as "listwaenite". Both rocktypes contain anomalous but sub-economic levels of Ni and Pt, but are depleted in Cu. Geochemical modelling has shown that ionic strength and cation contents of potential hydrothermal fluids are of less significance than oxidation state and to a lesser extent pH in mobilizing Pt from potential source rocks. Ppm levels of Pt are predicted in oxidized waters that have interacted with serpentinite, gabbro, pyritic gabbro and chromitite containing Pt metal and PtS. The rocks with highest Pt abundance (pyritic gabbro and chromitite) are not necessarily the best source rocks given that they have higher concentrations of reductant minerals. Modelling suggests that Pt release may occur in a rapid "spike" as Pt-undersaturated oxidized fluid overcomes the ability of the rock to buffer oxygen fugacity to low levels. Prediction of economic Pt deposits requires knowledge of many variables including fluid composition, total fluid flux, flow path (i.e. rock types traversed, mainly influencing oxidation state and pH), porosity (fracture density?) and time. Understanding the hydrodynamic regime in the area is therefore critical to the prediction of ore deposits.
Re-evaluation of theoretical calculations reaffirms that, at temperatures up to 300°C, significant solubility (>10 ppb) of Pt and Pd as chloride complexes is restricted to highly oxidizing and acidic conditions. This conclusion is supported by recently reported experimental solubility measurements. Experiments on the solubility of Pt and Pd in sodium hydroxide solutions at 25°C confirm that a change in species from Pd(OH)20 to Pd(OH)3- occurs at a pH of approximately 12, but apparently no such change in speciation occurs for Pt. The measured log β2 for Pt(OH)20 agrees very well with the previously predicted value, whereas predicted stability-constants for Pt(OH)3- and Pt(OH)42- should be considered only as provisional estimates. Hydroxide complexation is unlikely to contribute to the hydrothermal transport of Pt and Pd in most geological environments. Nevertheless, Pt, Pd and Au hydroxide complexes may be the dominant inorganic species of these metals in oxidized surficial waters such as seawater, lake water, and river water. -from Authors
Re-Os ages for six different molybdenite samples from the Elatsite deposit provide an opportu-nity to directly determine the age of ore mineralization for a Cretaceous subvolcanic Cu-Au system. There are two main stages of mineralization, an early magnetite-bornite-chalcopyrite stage (with noteable enrich-ments in Au-Pd-Pt), and a later chalcopyrite-pyrite stockwork stage where molybdenite first appears as a noteable sulfide phase at hand-specimen scale. In contrast to porphyry Cu systems that contain molybdenite throughout the paragenetic sequence, noteable molybdenite at Elatsite is restricted to a much narrower time interval. Our samples represent the main stage stockwork mineralization and their Re-Os ages range from 92.43 ± 0.04 to 92.03 ± 0.05 Ma (without 187 Re decay constant uncertainty). This suggests a minimum abso-lute life span of 400,000 ± 90,000 years for the stockwork mineralization in a magmatic-hydrothermal system <1.5 km across at the subvolcanic level. The high Re concentrations in the molybdenite (300-2750 ppm, 1875 ppm median) support direct involvement of mantle in an arc-subduction environment. These new Re-Os data and recently published U-Pb ages for zircon are in very good agreement, again demonstrating that robust and consistent age results may be expected from the Re-Os chronometer in molybdenite.
The Alpine-Balkan-Carpathian-Dinaride (ABCD) belt is one of the world's oldest mining areas and played a major role in the history of European civilizations, from well before the peak of the Greek and Roman civilizations up until the present day. Today, it is Europe's premier Cu-Au (-Pb-Zn-Ag) province, especially for gold-rich deposits associated with calc-alkaline magmatism, which have become a focus of renewed exploration interest after the political change in the eastern part of Central Europe. The Alpine-Balkan-Carpathian-Dinaride metallogenic and geodynamic province is part of the Alpine-Himalayan orogenic system which extends from western Europe through Iran and the Himalayas to China and Malaysia. This orogenic system is the result of convergence of the African, Arabian and Indian plates and their collision with Eurasia, mainly from the Cretaceous to the present. Along the Alpine-Himalayan system, major calc-alkaline magmatism is associated with certain segments only, whereas other segments are characterised by extensive regional metamorphism. This is a reflection of the complex geometry of the collision interface, with interfering microplates giving rise to several discontinuous sutures, highly diachronous magmatism, and transient subduction of continental crust leading to variable crustal thickening followed by extension and orogenic collapse. These interfering processes led to a very complex arcuate trace of the orogen, especially in the ABCD segment (e.g. Channell and Horváth 1976; Csontos 1995; Nemcok et al. 1998; Wortel and Spakman 2000; Ciobanu et al. 2002, this volume). The segmented geodynamic character of the orogen is reflected in an equally discontinuous distribution of ore deposits (Mitchell 1996; Jankovic 1997). This character stands in marked contrast to the long-lasting subduction of oceanic plates along the margins of the Pacific basin, which resulted in relatively stable magmatic arcs with elongate belts of magmatic-hydrothermal ore deposits, notably in the Andes. As a result of the complex geodynamic history, with several oceanic sub-basins and indenting continental microplates, the metallogeny of the ABCD region comprises several phases of major ore formation, in segments of limited lateral extent along the trace of the orogen. Major chromite deposits and copper-rich volcanic rock-hosted massive sulphides formed during precollisional oceanic magmatism between Early Jurassic and Middle Cretaceous, but probably in an oceanic arc rather than in a mid-ocean spreading environment. Three spatially and temporally distinct tectonic and metallogenic belts are associated with the Late Cretaceous to Neogene tectonic evolution of the ABCD belt (Fig. 1; Table 1) and are the focus of this Issue of Mineralium Deposita.
The age distribution of the crust is a fundamental parameter in modeling continental evolution and the rate of crustal accretion through Earth's history, but this is usually estimated from surface exposures. The exposed Yangtze craton in eastern China consists mainly of Proterozoic rocks with rare Archean outcrops. However, the U-Pb ages and Hf isotope systematics of xenocrystic zircons brought to the surface in lamproite diatremes from three Proterozoic outcrop areas of the craton suggest the widespread presence of unexposed Archean basement, with zircon age populations of 2900 2800 Ma and 2600 2500 Ma and Hf model ages of 2.6 to ca. 3.5 Ga or older. The zircons also record thermal events reworked on the craton ca. 2020 Ma (remelting of older crust) and 1000 850 Ma (addition of juvenile mantle material). The observation of deep crust significantly older than the upper crust will require revision of models for the rates of crustal generation through time.
In the determination of Re and platinum group elements in geological samples, various techniques have been em- ployed for digesting samples, including Carius tube, high-pressure asher (HPA-S), alkali fusion and nickel sulfide fire assay. The normal Carius tube technique is able to digest relatively small amount of sample and has a possible safety problem caused by a high internal pressure. This paper reports a modified Carius tube method which utilizes a sealed stainless steel high-pressure autoclave filled with water to prevent explosion of the tube. During heating, the external and internal pressures of the Carius tube increase simultaneously, such that the possible explosion of Carius tube can be avoided. Consequently, this technique allows a higher temperature (up to 330°C), a greater volume of aqua regia (up to 2/3 of the total volume of the Carius tube) and thus larger sample mass (12 g) relative to the normal Carius tube technique. Fairly good agreement were obtained for PGE poor mafic rocks (IPGE < 0.03 ng/g). The efficiency to dissolve ultramafic rocks and chromites at different temperatures was investigated. We demonstrate that this technique is more effective than normal Carius tube technique for ultramafic rocks and chromites containing refractory minerals and the detection limits and precision can be improved for PGE poor mafic samples. The total procedural blanks are lower than 0.003 ng for Os, 0.03 ng for Re, Ir, Ru and Rh and 0.4 ng for Pd and Pt.
This paper reports a modified digestion method for the determination of platinumgroup elements (PGEs) in geological samples. Samples are first digested by HF in a custom made 120 ml PTFE beaker on a hot plate to remove silicates. The dried residue is then digested with HF + HNO3 at 190 °C for about 48 h after the beaker is sealed in a stainless steel pressure bomb. Although only HF + HNO3 are used for sample digestion at relatively low temperature, ultramafic rocks with refractory minerals can be effectively decomposed by this method. Analytical results for CCRMP (CANMET, Ottawa, Canada) certified reference materials WGB-1 (gabbro), UMT-1 (ultramafic ore tailings), WPR-1 (peridotite) and WMS-1(Massive Sulphide), agree well with the certified values. The proposed method significantly simplifies the sample digestion procedures for PGE analysis compared to those used previously.
The 1,500-km-long Banatitic Magmatic and Metallogenetic Belt (BMMB) of Romania, Serbia and Bulgaria is a complex calc-alkaline magmatic arc of Late Cretaceous age. It hosts a variety of magmatic-hydrothermal Cu, Au, Mo, Zn, Pb and Fe deposits, including Europe's only world-class porphyry-copper deposits. Regional metallogeny can be linked to subduction of the Vardar Ocean during the Late Cretaceous, as part of the closure of the Neotethys Ocean that had separated Europe and Africa in the Mesozoic. Porphyry Cu-(Au)-(Mo) and intimately associated epithermal massive sulphides dominate in the central segments of the belt in southernmost Banat (Romania), Serbia and north-west Bulgaria. These districts are the economically most important today, including major active Cu-Au mines at Moldova Nou! in Romania, Majdanpek, Veliki Krivelj and Bor in Serbia, and Elatsite, Assarel and Chelopech in Bulgaria. More numerous (and mostly mined in the past) are Fe, Cu and Zn-Pb skarns, which occur mainly at the two ends of the belt, in Eastern Bulgaria and in Romania. This paper summarises some of the deposit characteristics within the geodynamic framework of terminal Vardar subduction. Heterogeneous terranes of the belt, including the Apuseni Mountains at the western end, are aligned parallel to the Vardar front following continental collision of the Dacia and Tisza blocks. All available geochronological data (numerous K-Ar and some U-Pb and Re-Os ages) are compiled, and are complemented by a new high-precision Re-Os date for the Dognecea skarn deposit, south-west Romania (76.6ǂ.3 Ma). These data indicate that magmatism extended over at least 25 million years, from about 90 to 65 Ma in each segment of the belt. Within Apuseni Mountains and Banat, where magma emplacement was related to syn-collisional extension in the orogenic belt of Carpathians, ore formation seems to be restricted in time and maybe constrained by a shared tectonic event.
The Elatsite porphyry copper deposit occurs in an island-arc setting hosted by Late Cretaceous monzonitic-monzodioritic porphyry stocks which were emplaced into Precambrian-Cambrian phyllites. Trace element data of the Late Cretaceous intrusive rocks suggest that they are I-type volcanic arc granitoids. Two main ore mineral assemblages are distinguished: (1) magnetite-bornite-chalcopyrite, and (2) chalcopyrite-pyrite. The first one is linked to potassic-propylitic, and the second to phyllic-argillic alteration. Minor ore minerals are hematite, molybdenite, sphalerite, pyrrhotite, marcasite, hessite, and solid solutions of linnaeite-siegenite-carrollite, tetrahedrite-tennantite, clausthalite-galena, gold-electrum and merenskyite-moncheite. Precious-metal contents are relatively high throughout the deposit but Au, Pd and Pt are concentrated more strongly in the magnetite-bornite-chalcopyrite assemblage. Average grades of Au, Ag, Pd and Pt calculated for the 0.33% Cu ore body are 0.96, 0.19, 0.007 and 0.002 g/t respectively. Analyses of flotation concentrates revealed 25.6% Cu, and Ag, Au, Pd and Pt contents of 33.0, 13.6, 0.72 and 0.15 g/t respectively. The copper mineralisation at Elatsite took place at pressures of 120 to 300 bar, corresponding to depths of formation of 1 to 3 km under hydrostatic conditions. The precious metals were probably transported jointly as chloride complexes in highly saline magmatic-hydrothermal solutions. The fluids had temperatures of 340 to >700 C and salinities of 28 to 64% NaCl, and mixed with meteoric water.
Abundant gold deposits are distributed along the margins of the North China Craton (NCC). Occurring throughout the Precambrian basement and located in or proximal to Mesozoic granitoids, these deposits show a consistent spatial–temporal association with Late Jurassic–Early Cretaceous magmatism and are characterized by quartz lode or disseminated styles of mineralization with extensive alteration of wall rock. Their ages are mainly Early Cretaceous (130–110 Ma) and constrain a very short period of metallogenesis. Sr–Nd–Pb isotopic tracers of ores, minerals and associated rocks indicate that gold and associated metals mainly were derived from multi-sources, i.e., the wall rocks (Precambrian basement and Mesozoic granites) and associated mafic rocks.
Several possible approaches for the location of mobile terminal in mobile telecommunication networks are presented in this paper. Some location algorithms are analyzed, such as location algorithm based TOA (Time of Arrival) parameters and location algorithm based AOA (Angle of Arrival) parameters. There are some analyses of location error about those methods in this paper. Finally some location simulation works are done about location method based TOA parameters and AoA parameters. The simulation results demonstrate the performance of location error. Those kinds of location approaches are compared with each other.
99% of the platinum group metals world production come from only four deposits. The South African Bushveld complex is with 80% of the total production the largest deposit, followed by the North Siberian Noril'sk-Talnakh complex, with 12%, the Canadian Sudbury complex, with 5%, and the North American Stillwater complex, with 2%. In 1996, a new deposit in the Great Dyke complex in Zimbabwe, will start its operation which will reach about 4 to 5% of the world production. - In contrast to platinum group metals, exclusively mined in the above mentioned magmatic ore deposits, gold occurs in a couple of genetically different types of deposits. The world gold production has remained constant since 1992, with about 2 200 t Au per year. South Africa, with 27% of the total production, followed by the USA, with 15%, Australia, with 12%, Canada, with 7% and Russia, with 7% belong to the most important producers in the world.
Precious metal (Pt, Pd and Au) and Re contents in rocks, ores and flotation concentrates of Siberian (Russia) and Mongolian porphyry Cu-Mo and Mo-Cu deposits were studied. The following deposits are discussed: Early Devonian porphyry Mo-Cu Sora deposit (Kuznetsk Alatau Mountains, Russia) and porphyry Cu-Mo Aksug deposit, (northeastern Tuva, Russia); Triassic porphyry Cu-Mo Erdenetiin Ovoo deposit (northern Mongolia). The samples analyzed include unaltered host rocks of plutons, porphyry rocks of ore-bearing series, different types of altered rocks, mineral separate analyses of molybdenite, chalcopyrite and magnetite, as well as flotation concentrates. Pt, Pd, Au and Re contents were determined using ICP/MS, AAS and inversion voltammetric analysis. PGE abundances in rocks and poorly mineralized samples span a large range from below detection limit to 65 ppb Pt and 74 ppb Pd. Re concentrations in whole rock samples range from below detection limit to 89 ppb. Molybdenite has been shown to be the major host phase for Re. The results presented show that Aksug deposit reveals elevated PGE and Au contents in ore minerals and flotation concentrates. High Pd contents in ores of the Aksug deposit are in accordance with the presence of palladium mineralization in the form of palladium telluride merenskyite (Pd, Pt) Te2. The variety of precious metals and Re contents in the studied deposits could be caused by a complex interplay of several factors, including importance of primary metal concentrations derived from the source, transport of metals to the deposition area, physicochemical properties of the fluid (f02, pH, Js, T, P), and depositional conditions. Higher Re contents in molybdenite and chalcopyrite separates are typical for copper-rich Aksug and Erdenetiin Ovoo deposits. Rhenium concentration in sulfides from molybdenum-rich Sora deposit is significantly lower. Highly oxidized, Cl-rich fluid style at Aksug and Erdenetiin Ovoo was favorable for high rhenium solubility and transport to depositional area. The occurrence of significant precious metals contents at Aksug were likely due to: 1) PGE and Au enriched source, 2) favorable fluid style (high f02, high Cl-activity), promoting high solubility and transportation of precious metals in ore-forming fluid as chloride complexes; 3) moderately reducing depositional conditions from PGE-bearing solutions containing As and Te, facilitating PGM deposition. As for the porphyry systems at the Sora and Erdenetiin Ovoo deposit they were probably devoid of precursors favorable for the enrichment in PGE and Au or the role of such precursors was insignificant.
Alkaline rocks, ranging in age from Precambrian to Cainozoic, are widespread in the Cordillera. They may be divided into kimberlite, mafic ultrapotassic syenite-pyroxenite-ijolite-carbonatite, alkali basalt, felsic syenite, and peralkaline granite-syenite-gabbro assemblages. Many of these alkaline rocks were emplaced in extensional tectonic environments, including rifts and back-arc basins. Important precious metal deposits associated with alkaline rocks include: 1) epithermal gold deposits, 2) porphyry copper-precious-metal deposits and 3) submarine exhalative deposits. Epithermal gold deposits are related to felsic (generally silica-undersaturated) syenites, trachytes and phonolites forming epizonal intrusions and vent complexes. They are characterized by K-feldspar-quartz-carbonate-fluorite-telluride veins, relatively low S abundance, and Au > Ag. Porphyry copper-precious-metal deposits are related to alkali gabbro and syenite (both silica-saturated and -undersaturated) plutons. They are characterized by Cu-sulphides in disseminations, pegmatites, veins and local immiscible blebs; relatively high S abundance; and Cu > Ag > Pt metals or Au. Both types of deposits exhibit pervasive carbonatic, K-metasomatic, redox and phyllic alteration. Epithermal gold deposits may grade downward into porphyry copper-precious-metal deposits. The difference in gold concentration between the two types may reflect changes in the dominance of thiosulphide-Au and telluro-Au complexes as transporting agents. To-date, submarine exhalative deposits have not been important producers of precious metals in the Cordillera except where the exhalite metals have been mobilized and concentrated by plutons. Epithermal silver and silver-base-metal deposits are associated with calc-alkaline rocks. In cases where the calc-alkaline rocks are coeval with alkaline rocks, the calc-alkaline rocks probably represent partial crustal melting by alkaline magmas. Using an electronic computer and a data-base of over 4200 analysed alkaline and related rocks from the Cordillera, the authors developed a series of chemical fingerprints to recognize areas with a high exploration potential for discovery of alkaline rock-related precious-metal deposits. These criteria define potential source-host rocks as: 1) alkaline (wt.% Na2O + K2O > 0.3718 (wt.% SiO2)-14.5); 2) members of the alkali basalt (basaltic rocks with normative olivine and nepheline or leucite), or the felsic syenite (Na2O + K2O >10 wt.% and MgO <2 wt.%) assemblage; 3) showing one or more of the following alteration assemblages-K-metasomatism (K2O > Na2O), redox (Fe2O3 >1.5 FeO), or carbonatic (CO2 >0.5 wt.%); 4) showing local anomalies in some of the following-Au (>10 ppb), Ag, As, Bi, Ce, Cu, F, Hg, La, Mo, Nb, Pb, S, Sb, Te, Tl (low in porphyry systems), U, and V; and 5) showing high Ba and Sr in Ba : Sr : Rb ratios. Such fingerprints may be effective in other areas and may be particularly useful in prospecting for invisible epithermal and submarine exhalative gold deposits. Authors' abstract-C.N.
A survey is given of the dimensions and composition of the present continental crust. The abundances of immobile elements in sedimentary rocks are used to establish upper crustal composition. The present upper crustal composition is attributed largely to intracrustal differentiation resulting in the production of granites senso lato. Underplating of the crust by ponded basaltic magmas is probably a major source of heat for intracrustal differentiation. The contrast between the present upper crustal composition and that of the Archean upper crust is emphasized. The nature of the lower crust is examined in the light of evidence from granulites and xenoliths of lower crustal origin. It appears that the protoliths of most granulite facies exposures are more representative of upper or middle crust and that the lower crust has a much more basic composition than the exposed upper crust. There is growing consensus that the crust grows episodically, and it is concluded that at least 60% of the crust was emplaced by the late Archean (ca. 2.7 eons, or 2.7 Ga). There appears to be a relationship between episodes of continental growth and differentiation and supercontinental cycles, probably dating back at least to the late Archean. However, such cycles do not explain the contrast in crustal compositions between Archean and post-Archean. Mechanisms for deriving the crust from the mantle are considered, including the role of present-day plate tectonics and subduction zones. It is concluded that a somewhat different tectonic regime operated in the Archean and was responsible for the growth of much of the continental crust. Archean tonalites and trond-hjemites may have resulted from slab melting and/or from melting of the Archean mantle wedge but at low pressures and high temperatures analogous to modern boninites. In contrast, most andesites and subduction-related rocks, now the main contributors to crustal growth, are derived ultimately from the mantle wedge above subduction zones. The cause of the contrast between the processes responsible for Archean and post-Archean crustal growth is attributed to faster subduction of younger, hotter oceanic crust in the Archean (ultimately due to higher heat flow) compared with subduction of older, cooler oceanic crust in more recent times. A brief survey of the causes of continental breakup reveals that neither plume nor lithospheric stretching is a totally satisfactory explanation. Speculations are presented about crustal development before 4000 m.y. ago. The terrestrial continental crust appears to be unique compared with crusts on other planets and satellites in the solar system, ultimately a consequence of the abundant free water on the Earth.
Lithospheric delamination is the foundering of dense lithosphere into less dense asthenosphere. The causes for this density inversion are thermal, compositional, and due to phase changes. For delamination to occur in the specific, and probably common, case where lithospheric mantle is intrinsically less dense than underlying asthenosphere due to composition differences, a critical amount of shortening is required for the densifying effect of cooler temperature to counterbalance the effect of composition. Crustal thickening that results from shortening may result in a crustal root that, due to phase changes, becomes denser than the underlying mantle lithosphere and should delaminate with it: most of the negative buoyancy resides at the top of the mantle and the bottom of the crust. In most cases composition is not known well enough to calculate the driving energy of delamination from densities of equilibrium mineral assemblages in a lithospheric column Poorly known kinetics of phase changes contribute additional uncertainties. In all cases however, the effects of delamination under a region are readily recognizable: rapid uplift and stress change, and profound changes in crustal and mantle-derived magmatism (a reflection of changes in thermal and compositional structure). Characteristics of delamination magmatism are exhibited in the Southern Puna Plateau, central Andes. The consequences of delamination for theories of crustal and mantle evolution remain speculative, but could be important. Recognition of delamination-related magmas in older (including Archean) orogens may be the best way to recognize past delamination events, because the magmas are among the most indelible and least ambiguous of delamination indicators.
A technique based on the common ion effect was used to obtain information on the stoichiometry of the Pt(IV) and Pd(II) chloride complexes at elevated temperature. The solubility of AgCl(s) was measured in solutions of fixed m HCl and varying Pt(IV) or Pd(II) concentration. Parallel experiments were conducted at Me/Cl mole ratios (Me = Pt or Pd) of 0.0-0.5 for m HCl = 0.03-3.0 at T = 100, 200, and 300°C. The average Cl ligand numbers for Pt ranged from 4.2 to 5.8, with the majority of values > 5. These results are adequately explained by a mixture of the simple monomeric species PtCl 2- 6 , PtCl - 5 , and PtCl 0 4 . The temperature dependence of the equilibrium constant for the dissociation reaction PtCl 2- 6 = PtCl - 5 + Cl - was obtained: log K = 2.40 (±0.25) - , K (valid to 573 K), which is in good agreement with published low temperature data. The neutral PtCl 0 4 species may become important at 300°C and low chloride concentrations (0.01 m HCl). Extrapolation of existing data indicates that the PT(IV) chloride complexes are stable with respect to Pt(II) chloride complexes over a range of f O 2 -pH conditions which narrows quickly with increase in temperature. Nonetheless, PtCl 2- 6 may be the dominant form of dissolved Pt in highly oxidized brines to at least 100°C. The average Cl ligand numbers for palladium ranged from 2.14 to 2.83, and were insensitive to temperature. These results could be explained by a mixture of PdCl 2 and PdCl - 3 . However, this is in disagreement with published experimental data which indicate that PdCl -2 4 is the predominant form of aqueous Pd at high chloride concentrations. An alternate explanation is that a significant quantity of the total aqueous Pd was present as polynuclear complexes, due to the very high Pd/Cl ratios of the experiments. Insufficient data exist to discriminate between these two hypotheses.
The solubility of the assemblage AgCl(s) + Ag-Pd alloy was measured in NaCl / HCl solutions at 300°C using the silica tube method. Oxidation state was controlled by the solid phases, according to the reaction . (A1) The Cl concentrations of the solutions ranged from 0.2 to 4.0 m, with calculated pH 300° C = 0.47 to 1.67. The surfaces of the alloys after the experiments were corroded and showed a substantial depletion in Ag relative to the initial compositions (either Ag .5 Pd .5 or Ag .7 Pd .3 ). Ag solubilities ranged from 0.026 to 0.39 m, whereas Pd solubilities were 3 to 4 orders of magnitude lower (max. of 10 -3.41 m). The results are in excellent agreement with previous studies of the solubility of AgCl ( , 1976; et al., 1986) and Pd-sulfide phases ( et al., 1992) in hydrothermal brines. For the following reaction: , (A2) a value of log K 300° C = 12.81 ± .18 was obtained, which compares with a value of 12.65 ± 0.5 obtained by et al. (1992). The agreement is strong evidence in favor of the validity of both experimental investigations. The results of the present study indicate that Ag will be far more soluble than Pd over most of the range of pH, f O 2 , and SCl concentration found in nature. Nonetheless, Pd-rich alloys may form, owing to the strong thermodynamic partitioning of Pd into the solid phase. Scavenging of dissolved palladium by pre-existing Au-Ag alloy is a viable precipitation mechanism and may limit PGE mobility to extremely low levels in many natural hydrothermal systems. Because this is the first detailed study of its type, the methods and results presented in this study have important applications to future experimental work in the hydrothermal geochemistry of precious metal alloys.
The Tonglushan ore district in the Middle–Lower Yangtze River Valley metallogenic belt includes the Tonglushan Cu–Fe, the Jiguanzui Au–Cu, and the Taohuazui Au–Cu skarn deposits. They are characterized by NE-striking ore bodies and hosted at the contact of Triassic carbonate rocks and Late Mesozoic granitoid deposits. New Sensitive High-Resolution Ion Microprobe (SHRIMP) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA–ICP-MS) zircon U–Pb, molybdenite Re–Os, and phlogopite 40Ar–39Ar ages indicate that these skarn deposits formed between 140.3±1.1 and 137.3±2.4Ma. These dates are identical to the zircon U–Pb ages for host quartz diorites ranging from 140±2 to 139±1Ma. These results confirm that both skarn mineralization and related intrusions were initiated during the Early Cretaceous. The high rhenium contents (261.4–1152μg/g) of molybdenites indicate that a metasomatic mantle fluid was involved in the ore-forming process of these skarn ore systems. This conclusion is consistent with previously published constraints from sulfur, deuterium, and oxygen isotope compositions, and the geochemical signatures, and Sr–Nd isotopic data of the mineralization-hosting intrusions. Geological and geochronological evidence demonstrates that there were two igneous events in the Tonglushan ore district. The first resulted in the emplacement of quartz diorite during the Early Cretaceous (140±2 to 139±1Ma), and the second is characterized by the eruption of volcanic rocks during the mid-Early Cretaceous (130±2 to 124±2Ma). The former is spatially, temporally and genetically associated with skarn gold-bearing mineralization (140.3±1.1 to 137.3±2.4Ma). The recognition of these two igneous events invalidates previous models that proposed continuous magmatism and associated mineral deposits in the Middle–Lower Yangtze River Valley metallogenic belt.
Ion microprobe (SHRIMP II) U-Pb zircon analyses reveal trondhjemitic magmatism at 2.90 2.95 Ga in the Kongling area of the Yangtze craton, south China, about 150 km south of the Permian-Triassic Qinling-Dabie-Sulu orogenic belt. Detrital zircons from nearby Archean metapelites are 2.87 3.28 Ga, and the rocks have Sm-Nd depleted mantle model ages of 3.07 3.21 Ga. The new data reveal, for the first time, >3.2 Ga sialic crust in the Yangtze craton, part of which predates that of the adjacent southern North China craton. Both trondhjemites and metapelites contain ca. 2.75 Ga high-grade metamorphic zircons, and ca. 1.9 Ga zircons, related to intrusion of the Quanqitang K-feldspar granite into the Archean basement. Many zircons also underwent Pb loss ca. 1.0 Ga during the Jinning orogeny, when the Cathysian block accreted to the Yangtze craton. The new data support correlation of part of the Korean Peninsula with the Yangtze craton along the eastern extension of the Qinling-Dabie-Sulu orogenic belt.
The Eastern Yangtse Craton of central to eastern China is an important FeCu metallogenic province. Based on studies of the regional geology and tectonic evolution, this metallogenic belt is controlled by faults and aulacogens in the continental plate. In the Early Yanshan Epoch (Jurassic), the dominant west-northwest and east-west lithospheric faults controlled the distribution of Cu (Mo, and Au) mineralization, whereas in the Late Yanshan Epoch (Cretaceous) the north-northeast and northeast lithospheric faults controlled CuFe mineralization. In a mineral district, the distribution of ore-fields is under the dual control of basement fault(s) and near-surface fault(s). Based on the relation of ring and lineament faults to intrusions, a ‘three-level’ model of vertical zonation is proposed. Systematic petrochemical studies of Mesozoic igneous rocks and mineralization identify three subseries: (1) a calc-alkaline, intermediate to silicic subseries rich in potassium; (2) a calc-alkaline, intermediate to felsic subseries rich in sodium; and (3) a calc-alkaline, intermediate to mafic subseries rich in sodium. Genetic types of ore deposits are diverse, including Fe and Cu skarns, Cu porphyries, Fe ore magma injections, Ningwu-Luzong Fe deposits (from late orthomagmatic to pegmatitic-pneumato-hydrothermal, and to mesothermal-epithermal) associated with subvolcanic rocks, and remobilized sedimentary Fe and/or Cu deposits. The genetic types of ore deposits form two metallogenic series: (1) a sedimentary metallogenic series (active mainly in the Paleozoic), and (2) a magmatic-hydrothermal metallogenic series consisting of three subseries (active predominantly in the Jurassic and Cretaceous), with the latter being more important in this region. The superposition and compounding of these two metallogenic series contribute to many styles of mineralization in this mineral province.
Magmatic sulfide deposits are divisible into two major groups, those that are valued primarily for their Ni and Cu and that are mostly sulfide rich (>10% sulfide), and those that are valued primarily for their PGE and tend to be sulfide poor (<5% sulfide). Most members of the Ni-Cu group formed as a result of an interaction of mantle-derived magma with the crust that gave rise to the early onset of sulfide immiscibility. Of the different classes of deposit in this group, the komatiite-related class ranges from 2.7 to 1.9 Ga in age, the Flood basalt-related class from 1.1 to 0.25 Ga, and the Mg basalt- and basalt-related group from the Archean to the present. There is only one example each of anorthosite complex- and impact-related deposits, so that one cannot generalize about their secular distribution, except to say that anorthosite complexes are Proterozoic. Ural-Alaskan intrusions are dominantly Phanerozoic (some Archean deposits have been included with this group), but as yet no examples have been found with economic sulfide bodies. Seventy-five percent of known PGE resources occur in three intrusions-the Bushveld, Great Dyke, and Stillwater, the rocks all of which have crystallized from two magma types, an unusual, high SiO 2, MgO, and Cr and low Al 2O 3 type (U-type) that was emplaced at an early stage and a later, normal tholeiitic-type magma (T-type); the PGE are concentrated in layers close to the level at which the predominant crystallization switches from one magma type to the other. The U-type magma is interpreted as a PGE-rich, komatiitic magma (possibly the product of two-stage mantle melting) that has interacted to varying degrees with the crust, becoming SiO 2 enriched in this way. These three intrusions are Neoarchean to Paleoproterozoic in age. All known examples of komatiites, with one exception, are Paleoproterozoic or older and their secular distribution is thought to be due to cooling of the Earth. Known deposits do not occur in the oldest (>3.0 Ga) komatiites but appear at around 2.7Ga in continental (Kambalda, Western Australia) or island-arc (Perseverance-Mount Keith, Western Australia) environments, possibly because it was these environments that offered the opportunity for interaction with felsic rocks. It is suggested that the development of these environments in the Archean was an additional control on the age distribution of these deposits. It is postulated that the restricted secular distribution of PGE-enhanced intrusions is also due to the need for a hot mantle to give rise to U-type magmas.
The geologic history of the San Manuel-Kalamazoo deposit has provided an opportunity for the examination of vertical and horizontal zoning relationships in a porphyry copper system. Precambrian Oracle "granite," a Laramide monzonite porphyry, and a Laramide dacite porphyry are hosts to zones of potassic, phyllic, argillic, and propylitic assemblages shown to be coaxially arranged outward from a potassic core through phyllic, argillic, and propylitic zones. Alteration zones at depth comprise an outer chlorite-sericite-epidote- magnetite assemblage yielding to an inner zone of quartz-K4eldspar-sericite- chlorite. Mineralization zones are conformable to the alteration zones, the ore zone (with a 0.5% Cu cutoff) overlapping the potassic and phyllic zones. Occurrence of sulfides changes upward and outward from dissemination at the low-grade core of the deposit through microveinlet to veinlet and finally vein occurrence indicating the progressively increasing effect of structural control. Several aspects of San Manuel-Kalamazoo geology suggest that it is exemplary of the porphyry copper deposit group. To test that idea and to evolve three-dimensional aspects of these deposits, a table of geologic characteristics of 27 major porphyry deposits is presented. Consideration of the table indicates that the "typical" porphyry copper deposit is eraplaced in late Cretaceous sediments and metasediments and is associated with a Laramide (65 m.y.) quartz monzonite stock. Its host intrusive rock is elongate-irregular, 4,000 X 6,000 feet in outcrop, and is progressively differen-tiated from quartz diorite to quartz monzonite in composition. The host is more like a stock than a dike and is controlled by regional-scale faulting. The orebody is oval to pipelike, with dimensions of 3,500 X 6,000 feet and gradational boundaries. Seventy percent of the 140 million tons of ore occurs in the igneous host rocks, 30 percent in preore rocks. Metal values include 0.45% hypogene Cu with 0.35% supergene Cu, and 0.015% Mo. Alteration is zoned from potassic at the core (and earliest) outward through phyllic (quartz-sericite-pyrite), argillic (quartz-kaolin-montmorillonite), and propylitic (epidote-calcite-chlorite), the propylitic zone extending 2,500 feet beyond the copper ore zone. Over the same interval, sulfide species vary from chalcopyrite-molybdenite-pyrite through successive assemblages to an assemblage of galena-sphalerite with minor gold and silver values in solid solution, as metals, and as sulfosalts. Occurrence characteristics shift from disseminations through respective zones of microveinlets (crackle fillings), veinlets, veins, and finally to individual structures on the periphery which may contain high-grade mineralization. Breccia pipes with attendant crackle zones are common. Expression of zoning is affected by exposure, structural and compositional homogeneity, and postore faulting or intrusive activity. Vertical dimensions can reach 10,000 feet, with the upper reaches of the porphyry environment perhaps only at subvolcanic depths of a few thousand feet. The vertical and lateral zoning described is repeated with sufficient constancy that depths of exposure at many deposits can be cited against the model of San Manuel-Kalamazoo. Several lines of evidence suggest relatively shallow depths of formation and significant variations in water content in the porphyry environment. Shallow emplacement is consistent with the appearance of breccia pipes associated with ring and radial diking and with vertically telescoped zoning. Models of the source of altering-mineralizing fluids are considered.
Accurate and precise determination of platinum group elements (PGEs) at ppb concentrations in geological samples is important but problematic. This paper reports an improved analytical method for the determination of Pt, Pd, Ru, Ir and Rh at sub-ppb levels by isotope dilution-inductively coupled plasma mass spectrometry (ID-ICP-MS). Prior to experimentation, all reagents were carfully purified: HBO3, HCl and SnCl2 by Te coprecipitation and HNO3 and HF by subboiling distillation. HF, HNO3 and HCl were used to decompose 10 gram sample. The fluoride residue from the acid digestion is minimized by using H3BO3 for complexation, thus mini-fusion of sodium peroxide can be performed in corundum crucibles instead of bulk Na2O2 fusion to lower blank level. The solution of acid digestion and Na2O2 fusion are combined and PGEs are then pre-concentrated by Te coprecipitation. Cu, Ni, Zr and Hf are removed using cation exchange resin and P507 extraction chromatography resin combined in the same column to minimize their interference. Pt, Pd, Ru and Ir are determined using ID-ICP-MS, whereas the mono-isotopic element, Rh, is determined by external calibration using highly enriched 194Pt as the internal standard. The enriched 194Pt spike behaves similar to Rh during the Te precipitation procedure and acts as an ideal internal standard. The determination limits for PGE range from 0.01–0.19 ng g−1. The results obtained using this new method for the CCRMP (CANMET, Ottawa, Canada) certified reference materials WGB-1 (gabbro), TDB-1 (diabase) and UMT-1 (ultramafic ore tailings), show good agreement with the reported values, but have discrepancies compared with the certified values when the concentration of Ru, Rh and Ir below 0.5 ng g−1.
: The Fengshan porphyry-skarn copper–molybdenum (Cu–Mo) deposit is located in the south-eastern Hubei Province in east China. Cu–Mo mineralization is hosted in the Fengshan granodiorite porphyry stock that intruded the Triassic Daye Formation carbonate rocks in the early Cretaceous (∼140 Ma), as well as the contact zone between granodiorite porphyry stock and carbonate rocks, forming the porphyry-type and skarn-type association. The Fengshan granodiorite stock and the immediate country rocks are strongly fractured and intensely altered by hydrothermal fluids. In addition to intense skarn alteration, the prominent alteration types are potassic, phyllic, and propylitic, whereas argillation is less common. Mineralization occurs as veins, stock works, and disseminations, and the main ore minerals are chalcopyrite, pyrite, molybdenite, bornite, and magnetite. The contents of palladium, platinum and gold (Pd, Pt and Au) are determined in nine samples from fresh and mineralized granodiorite and different types of altered rocks. The results show that the Pd content is systematically higher than Pt, which is typical for porphyry ore deposits worldwide. The Pt content ranges from 0.037 to 1.765 ppb, and the Pd content ranges between 0.165 and 17.979 ppb. Pd and Pt are more concentrated in porphyry mineralization than skarn mineralization, and have negative correlations with Au. The reconnaissance study presented here confirms the existence of Pd and Pt in the Fengshan porphyry-skarn Cu–Mo deposit. When compared with intracontinent and island arc geotectonic settings, the Pd, Pt, and Au contents in the Fengshan porphyry Cu–Mo deposit in the intracontinent is lower than the continental margin types and island are types. A combination of available data indicates that Pd and Pt were derived from oxidized alkaline magmas generated by the partial melting of an enriched mantle source.
A large number of experiments (n = 185) were used to measure the solubilities of synthetic PtS (cooperite) and PdS (vysotskite) in aqueous H2S-rich solutions at 30 to 300°C. The experiments were performed in sealed silica tubes (T > 100°C) or in Pyrex vessels equipped with gas-tight PTFE valves (T < 100°C). The solutions contained ΣS²⁻(aq) = 0.01 to 1.0 m, with pH controlled by (pH200°C = 0.5 to 1.0); (3.0 to 4.3); (6.4 to 7.9); or (7.7 to 8.2). The solubilities of both sulfides increased systematically with increase in ΣS·−. Maximum solubilities were 11.1 ppm Pd and 2.4 ppm Pt, for 200°C solutions containing 1.0 m ΣS²⁻ and pH values near the boundary. Much lower solubilities were measured in acid solutions (< 10 ppb). In general, solubilities decreased with increase in temperature, especially between 200 and 300°C. The results were used to calculate the following equilibrium constants (I = 0.0, P = Psat):
This stock, which contains a porphyry Cu-Ag-Au-Pt metals deposit, is an epizonal Laramide pluton at the SW end of the Colorado mineral belt. The stock and associated mineralization evolved by a seven-stage interaction of igneous and metasomatic processes: 1) forceful emplacement of syenite plutons; 2) intense hydrothermal argillization of stage 1 syenites; 3) intrusion of mafic syenite plutons, some layered, along shear zones; 4) violent escape of volatiles, producing intrusive breccia pipes; 5) intense K-metasomatic alteration of older stock units with production of a fenite-like alteration halo extending 1000 m beyond the stock and simultaneous intrusion of carbonate-bearing alkali feldspar dykes; 6) emplacement of trachyte, syenite pegmatite, and mafic pegmatite dykes; 7) deposition of metallic minerals, sanidine, quartz, calcite and fluorite as veinlets and disseminated replacement masses from hydrothermal solutions. The stock shows enrichment of volatiles (CO 2, F and S), high concentrations of Ba and Sr, low concentrations of Rb, high concentrations of Cu, Ag, Au, Bi, Te, Pt and Pd, with little or no enrichment in Nb, U, Y and Zr. A computer-readable data base was used to compare the Allard stock with others in the western USA and Canada. Major- and trace- element analyses (50) of samples from the Allard Stock are presented.-P.Br.
A new proficiency testing sample, OPY-1 (ultramafic rock), the basis of the twentieth international proficiency test of analytical geochemistry laboratories (GeoPT 20), was recently prepared by the International Association of Geoanalysts (IAG). This paper reports analytical data for Os, Ir, Ru, Rh, Pt and Pd with different digestion techniques, including an improved Carius tube, Carius tube combined with HF dissolution and alkaline fusion. About 4–15% of the PGEs are in the silicate phase, which cannot be leached by aqua regia even when digested at 300 °C with the Carius tube technique. Both the Carius tube technique combined with HF dissolution and alkaline fusion can obtain reliable data. The results demonstrated that OPY-1 is sufficiently homogeneous at a 2 g test portion level to be suitable as a reference material for method validation. The procedure for sealing the Carius tube was simplified and the recommended digestion procedures are provided.
An experimental study of the solubility of Pt and Pd sulfides and Au metal in aqueous bisulfide solutions was conducted at temperatures from 200° to 350 °C and at saturated vapor pressure. A 500-mL Bridgemantype pressure vessel constructed of titanium, and equipped with a motor-driven magnetic stirrer was employed. The pH and the oxidation state were buffered by the coexistence of H2S/HS−/SO inf4 sup2− . The pH at temperature was calculated to be in the range 5.91–9.43, and ∑S was 0.3–2.2 m. Under the experimental conditions, the measured solubility of gold is about two to three orders of magnitude greater than that of either platinum and palladium, and the measured solubility of platinum is, in general, approximately equal to that of palladium, in molal units. The solubilities are found to be in the range: platinum 4–800 ppb, palladium 1–400 ppb, and gold 2–300 ppm. The solubility data can be modeled adequately using the following reactions: Au+H2S+HH−=Au(HS) 2 − +1/2H2 (K14); PtS+HS−+H+=Pt (HS) 2 0 (K15); PdS+HS−+H+=Pd (HS) 2 0 (K16); PtS2+H2=Pt (HS) 2 0 (K21). With equilibrium constants determined as follows (errors represent two standard deviations):
Mineralized quartz diorites of the Santo Tomas II porphyry copper-gold deposit, carry high Au contents (average: 1.8 ppm) as well as 160 ppb Pd and 38 ppb Pt. Values of other platinum-group elements (PGE) and rhenium are below the analytical detection limits. There is a significant positive correlation between Au and Cu. The highest Pd values were detected in the most Au- and Cu-rich rocks. Platinum-group minerals (PGM) occur exclusively as inclusions in chalcopyrite and bornite. Potential Pd and Pt contents in sulphide concentrates are estimated at 1.5 g/t and 0.4 g/t, respectively. The precious metal assemblages consist of merenskyite (main PGM), kotulskite, moncheite, native gold, electrum, hessite and petzite. Polyphase fluid inclusions in quartz veinlets, associated with a PGM-bearing bornite-chalcopyrite-magnetite assemblage, are characterized by high salinity (35 to > 60 eq. wt% NaCl) and high trapping temperatures (between 380 and 520 C). They may represent primary magmatic-hydrothermal fluids, which have been responsible for the transport of Pd, Pt and Au as chloride complexes.
Sulphide and flotation concentrates from 33 porphyry copper deposits have been investigated for platinum-group elements (PGE), Au, Cu and platinum-group minerals (PGM). The major sulphides in the samples studied are chalcopyrite and pyrite. Bornite is less frequent and molybdenite occurs in traces only. PGM (merenskyite, sperrylite and an unidentified Pd-Sb telluride) have been found as inclusions in chalcopyrite. Pd and Pt are present in concentrations above the analytical detection limit (>8 ppb) in 70% respectively 30% of the deposits studied. The contents of Os, Ir, Ru and Rh are below detection limits in all samples. The analytical results show that 7 deposits (six of island are and one of continental margin setting) reveal relatively high Pd contents (130-1900 ppb) which are associated with high Au contents (1-28 ppm). In five of them discrete PGM can be identified in accordance with elevated levels of Pd. Correlations of Au, Pd and Pt point towards a common origin. Even though the data base is relatively small, a trend is obvious, suggesting that Au-rich island are porphyry copper deposits might host more Pd and Pt than the continental margin type ones. Other aspects of intrusive rocks, such as geological age, chemical composition and magma type do not seem to influence PGE contents.
The Cu–Fe–Au–Mo (W) deposits in southeastern Hubei are an important component of the Middle–Lower Yangtze River metallogenic
belt. Molybdenite from the Fengshandong Cu- (Mo), Ruanjiawan W–Cu- (Mo), Qianjiawan Cu–Au, Tongshankou Cu–Mo and Tonglüshan
Cu- (Fe) deposits yielded Re–Os ages of 144.0 ± 2.1 Ma, 143.6 ± 1.7 Ma, 137.7 ± 1.7 Ma, 142.3 ± 1.8–143.7 ± 1.8 Ma and 137.8
± 1.7–138.1 ± 1.8 Ma, respectively. Phlogopite from the Tieshan Fe- (Cu) deposit yielded an Ar–Ar age of 140.9 ± 1.2 Ma. These
data and other published isotopic ages (Re–Os molybdenite and Ar–Ar mica ages) for the Cu–Fe–Au–Mo (W) deposits in the Middle–Lower
Yangtze River metallogenic belt show that Cu–Fe–Au–Mo (W) mineralisation in the Tongling, Anqing, Jiurui and Edong ore districts
developed in a narrow time span between 135.5 and 144.9 Ma, reflecting an important regional metallogenic event. An integrated
study of available petrological and geochronological data, together with relationships to magmatism and the regional geodynamic
framework, indicate that the Cu–Fe–Au–Mo (W) mineralisation in the Middle–Lower Yangtze River belt occurred during a regime
of lithospheric extension. This extension is probably related to Late Mesozoic processes of lower crustal delamination and
lithospheric thinning in East China.
Mount Pinatubo in the Philippines, known for its cataclysmic eruption in 1991, hosts several porphyry copper deposits and active geothermal systems. An underlying mafic melt supplied much of the sulphur for the dacitic magma and its injection into the dacitic magma chamber triggered the eruption. The eruption caused purging of the sulphur-rich fluid from the dacite to the atmosphere and extensive fracturing. Similar events took place at Bingham Canyon, Utah, site of the largest copper and gold deposit in North America at 38 Ma. The Bingham Canyon mineralization took place beneath an active stratovolcano and pyroclastic flows contemporaneous with the mineralization show evidence for magma mingling. Ascent of mafic melt supplied sulphur and chalcophile elements to the felsic magma, which consolidated to form the Bingham stock and its underlying magma chamber. Injections of the mafic melt caused periodic eruptions of felsic magma to form the stratovolcano and deposition of sulphide minerals in highly fractured rocks in and around the stock.
We studied primary ore samples from Kalmakyr, a giant Cu–Au–Mo porphyry deposit in eastern Uzbekistan. Disseminated and stockwork-type
high-grade Cu–Au–Mo mineralization showed average concentrations of 55ppb Pd, 5.5ppb Pt, 0.95ppb Rh, 0.49ppb Ir, and 4.1ppm
Au (n = 8). This type of mineralization is characterized by the presence of pyrite, chalcopyrite, molybdenite, and gold. A peak
Pd content of 292ppb was determined in a base-metal-rich quartz vein in granodiorite porphyry, which contains galena, sphalerite,
chalcopyrite, tetrahedrite, and gold. Palladium correlates with Cu, Ag, Se, and S. Mineralogical and laser ablation ICP-MS
study confirmed that Pd is homogeneously distributed in chalcopyrite, which contains up to 110ppm Pd, and tetrahedrite, containing
up to 20ppm Pd. An assessment of the Pd and Pt budget at Kalmakyr showed the potential of approximately 17t of Pd and 1.7t
of Pt.
KeywordsCu–Au–Mo porphyry deposit-Platinum-group elements-Kalmakyr-Uzbekistan
The solubility of metallic Pt in HCl solutions was determined at 200 to 300°C at oxidation states buffered near the aqueous Pt(II)/Pt(IV) boundary. Equilibrium constants were obtained for the following disproportionation reactions: log K, 200° 250° 300°C 2PtCl42− = PtCl42− + Pt(s) + 2Cl− 1.47 1.70 1.54 (a) 2PtCl3− = PtCl5− + Pt(s) + Cl− 1.77 1.74 1.37 (b) with experimental uncertainties of approximately ±0.20 log units. These results are found to be in good agreement with previously published estimates for reaction at 60 to 152.5°C. The data indicate that the relative stability of the Pt(II) and Pt(IV) chloride complexes does not change appreciably with temperature. This is in contrast to previous work in the Au(0)/Au(I)/Au(III) system which demonstrates that the Au(I) chloride complexes are unstable with respect to Au (III) at low temperature, but become the dominant aqueous species at 300°C.Pt(IV) chloride complexes are unlikely to be important in high temperature hydrothermal fluids, as unrealistically high aqueous platinum concentrations are required to stabilize these species relative to Pt(II). In contrast, thermodynamic calculations suggest that Pt(IV) chloride or hydroxychloride complexes may be the dominant form of dissolved platinum in low temperature brines that are strongly oxidized (e.g., seawater). In oxygenated, Cl-rich solutions, the solubility of Pt is extremely high at pH < 6, such that the mobility of this metal will most likely be limited by surface adsorption reactions and/ or its abundance and rate of dissolution in the enclosing rock or soil. At neutral to alkaline pH, calculated solubilities are much lower, and saturation with Pt oxide phases may occur, as has recently been described in nature.