Precious metal and telluride mineralogy of large volcanic-hosted massive sulfide deposits in the Urals

Summary The study focuses on the mode of occurrence of Au, Ag and Te in ores of the Gaisk, Safyanovsk, Uzelginsk and other volcanic-hosted massive sulfide (VHMS) deposits in the Russian Urals. Minerals containing these elements routinely form fine inclusions within common sulfides (pyrite, chalcopyrite and sphalerite). Gold is mostly concentrated as ‘invisible’ gold within pyrite and chalcopyrite at concentrations of 1–20 ppm. Silver mainly occurs substituted in tennantite (0.1–6 wt.% Ag). In the early stages of mineralization, gold is concentrated into solid solution within the sulfides and does not form discrete minerals. Mineral parageneses identified in the VHMS deposits that contain discrete gold- and gold-bearing minerals, including native gold, other native elements, various tellurides and tennantite, were formed only in the latest stages of mineralization. Secondary hydrothermal stages and local metamorphism of sulfide ores resulted in redistribution of base and precious metals, refining of the common sulfides, the appearance of submicroscopic and microscopic inclusions of Au–Ag alloys (fineness 0.440–0.975) and segregation of trace elements into new, discrete minerals. The latter include Au and Ag compounds combined with Te, Se, Bi and S. Numerous tellurides (altaite, hessite, stützite, petzite, krennerite etc.) are found in the massive sulfide ores of the Urals and appear to be major carriers of gold and PGE in VHMS ores.     

Gold distribution in As-deficient pyrite and telluride mineralogy of the Yangzhaiyu gold deposit,Xiaoqinling district,southern North China craton

The Mesozoic Yangzhaiyu lode gold deposit is situated in the southern edge of the North China craton. Gold mineralization is hosted in Archean amphibolite facies metamorphic rocks, and consists mainly of auriferous quartz veins. Pyrite is the predominant sulfide mineral, with minor amounts of chalcopyrite, sphalerite, and galena. Based on morphology and paragenesis, there are three generations of pyrite, termed as first generation (G1), second generation (G2), and third generation (G3). They have distinct contents, occurrences, and distribution patterns of gold. The coarse-grained, euhedral G1 pyrite contains negligible to low levels of gold, whereas both invisible and visible gold are present in the fine- to medium-grained G2 pyrite that is characterized by abundance of microfractures and porosities, forming a foam-like texture. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) depth profiles indicate that invisible gold occurs either as solid solution or as nanoparticles of gold-bearing tellurides in the G2 pyrite. Visible gold is widespread and present as irregular grains and stringers of native gold mostly along grain boundaries or filling microfractures of pyrite, likely resulting from remobilization of invisible gold once locked in the G2 pyrite. The G3 pyrite, invariably intergrown with chalcopyrite, sphalerite, and galena, contains the highest levels of invisible gold. There is a positive correlation between Au, Ag, and Te, indicating that gold occurs as submicroscopic Au-bearing telluride inclusions in the host minerals. Whenever gold, either invisible or visible, is present, As is always below or only marginally higher than the detection limit of LA-ICP-MS. This indicates that As played an insignificant role in gold mineralization. Tellurides are widespread in the auriferous quartz veins, consisting mainly of petzite, calaverite, hessite, altaite, and tellurobismuthite. Native gold commonly occurs as intergrowths with tellurides. Textural evidence indicates a precipitation sequence, in a temporal order, of calcaverite, petzite, altaite, tellurobismuthite, and hessite. Little amount of sulfide phases has been found in association with the tellurides, indicating that tellurides were deposited under low S fugacity (fS ₂ ) and/or high Te fugacity (fTe ₂ ) conditions. The textural relationships, when combined with fluid inclusion microthermometric data of auriferous quartz veins and tellurides thermodynamic data, permit estimation for logfTe ₂ during telluride formation, which are −6.8 to −10.8 at 300°C and −9.6 to −17.6 at 250°C. Available geochronological and geochemical data suggest that Te was most likely derived from the late Mesozoic magmatic rocks widespread in the Xiaoqinling district and other parts of the southern North China craton, which were emplaced broadly contemporaneous with gold mineralization at Yangzhaiyu. This study highlights the role of Te and tellurides as important gold scavengers in As-deficient ore fluids.     

应用电子探针技术研究%山东金青顶金矿床碲化物特征

对含碲金矿中碲化物物相组成和元素赋存特征开展系统的研究,有助于对此类金矿矿床成因的理解和找矿勘查工作。山东金青顶金矿床伴生的碲化物由于碲化物颗粒较小,不易被发现,以往的研究缺乏对碲化物元素分布的精细刻画。本文通过电子探针背散射图像、波谱分析、能谱分析结合面扫描技术对金青顶金矿床碲化物进行了分析,研究碲化物的种类、共生关系、化学成分以及元素分布特征等。结果表明:碲金银矿与碲银矿密切共生,常形成连生体,Au、Ag在连生体中不均匀分布,面扫描图局部可见碲金矿亮斑;Te总是优先和Ag结合,生成碲银矿,随着Ag的消耗碲金银矿开始出现,Ag被耗尽后Te与Au生成碲金矿,成矿后期热液中多余的金与碲金银矿或碲银矿反应生成非常规碲化物(如本文发现的Ag2.95Au1.83Te),当Te消耗完后生成自然金;金银矿物的生长顺序是碲银矿—碲金银矿—碲金矿—自然金。本研究为含碲金矿的综合利用提供了技术支持。     

Chimneys in Paleozoic massive sulfide mounds of the Urals VMS deposits: Mineral and trace element comparison with modern black,grey, white and clear smokers

In the Urals, a wide range of well-preserved chimneys are found in VMS deposits, which are associated with ultramafic (Atlantic type: Dergamysh), mafic (Cyprus type: Buribay), bimodal mafic (Uralian type: Yubileynoye, Sultanovskoye, Yaman-Kasy, Molodezhnoye, Uzelga-4, Valentorskoye) and bimodal felsic (Kuroko or Baymak type: Oktyabrskoye, Tash-Tau, Uselga-1, Talgan, Alexandrinskoye) sequences. Chimneys have also been found in the Safyanovskoye deposit (Altay type) that is hosted by intercalated felsic lavas and carbonaceous shales. A combination of geological, mineralogical and trace element data provide a general outline for comparison between chimneys from the Urals deposits and modern vent sites. The chimneys from the Dergamysh deposit show a broad affinity with those from the Rainbow and other vent sites associated with serpentinites of the Mid-Atlantic Ridge. The chimneys from the Buribay deposit are similar to the black smokers of the EPR vent sites including the scarcity of rare minerals. The chimneys from the Urals type of the VMS deposits show some similarities with grey smokers from the Brother Volcano and PACMANUS sites. The chimneys from the Baymak type of the VMS deposits resemble grey and white smokers of the PACMANUS and grey smokers of the Suiyo vent sites. The chimneys from the Safyanovskoye deposit are similar to the black and clear smokers from the Okinawa Trough. Mineral assemblages are controlled by the combination of host rock composition and physico-chemical conditions of the ore-forming processes. Amount of colloform pyrite, isocubanite and pseudomorphic pyrite and marcasite after pyrrhotite decreases in the chimneys across the range from ultramafic and mafic to felsic-hosted deposits and is concomitant with increase in the contents of sphalerite, galena, bornite, fahlores, native gold and barite across this range. The chimneys from the Urals type contain abundant tellurides and sulfoarsenides, while these minerals are rare (except for hessite) in the Baymak type deposits. In the same range, the buffering capacity of host rocks decreases in contrast to the increase in ƒS₂ and ƒO₂. With the exception of the Safyanovskoye deposit, trace element assemblages in chalcopyrite vary to reflect the host rock: ultramafic (high Se, Sn, Co, Ni, Ag and Au) → mafic (high Co, Se, Mo and low Bi, Au and Pb) → bimodal mafic (high Te, Au, Ag, Bi, Pb, Co, moderate Se, and variable As and Sb) → bimodal felsic (high As, Sb, Mo, Pb, moderate Bi, and low Co, Te and Se). In sphalerite of the same range, the contents of Bi, Pb, Ag, Au and Sb increase versus Fe, Se and Сo. The variations in trace elements in colloform pyrite coincide with these changes. The specific mineral changes in the local ranges from Cu- to Zn-rich chimneys in each VMS deposit are similar to the general changes in the range of host rock classes of the deposits. However, the local T, ƒS₂ and ƒO₂ changes can broadly be interpreted in terms of contribution of variable oxygenated cold seawater to the subseafloor and seafloor hydrothermal processes.     

北京市得田沟金矿床碲矿物系列的研究

北京市得田沟金矿床是受韧性剪切带控制的金－黄铁矿－多金属硫化物石英脉型金矿床。笔者通过研究发现该矿床中的碲已达工业品位。     

Gold and silver tellurides in the Shirokinsky ore-and-placer cluster,the Sette-Daban Ridge,Yakutia

The first findings of Au and Ag tellurides (sylvanite and petzite) in sulfide-quartz ore of the Shirokinsky ore and placer cluster located in the Sette-Daban Horst-Anticlinorium are described. These minerals were found for the first time at the gold deposits of East Yakutia. The chemical compositions (wt %) of sylvanite (23.65–24.61 Au, 12.7–13.13 Ag, 59.3–59.97 Te, 96.26–97.97 in total) and petzite (23.17–25.24 Au, 42.27–44.40 Ag, 31.26–33.37 Te, 98.19–102.55 in total) are reported. Galena as a host mineral is associated with native gold, electrum, hessite, and stützite. The finding of Au-Ag and Ag tellurides provides evidence for the development of Au-telluride mineralization in the Sette-Daban Horst-Anticlinorium.     

小秦岭金矿田中的两种罕见矿物—碲铅铋矿和自然碲

碲铅铋矿和自然碲产于河南省小秦岭含金石英脉矿床中。碲铅铋矿化学成分平均值(%)为:Te44.06,Bi40.24,Pb14.23,并含有微量的Ag、Au、Hg、Fe、Ni、Cu等元素。理论化学式为(Bi,Pb)_3Te_4,其中Bi>Pb。共生矿物有自然金、碲金矿、破银矿、碲铅矿、碲金银矿、碲铋矿;方铅矿、闪锌矿、黄铁矿、黄铜矿等。 自然碲反射色为纯白微带乳色,非均质性清楚,偏光色为蓝灰-棕灰色。显微硬度为H_v=85.1kg/mm~2(25g)。共生矿物有碲金银矿、碲银矿、黄铜矿等。化学成分中碲含量达98.44％,并含Ag、Cu、W、Fe、Pt等微量元素。     

Mineral Paragenesis and Ore‐Forming Processes of the Dongping Gold Deposit,Hebei Province,China

The Dongping gold deposit is located near the center of the northern margin of the North China Craton. It is hosted in the Shuiquangou syenite and characterized by large amounts of tellurides. Numerous studies have addressed this deposit; the mineral paragenesis and ore‐forming processes, however, are still poorly studied. In this contribution, a new mineral paragenesis has been evaluated to further understand ore formation, including sulfides (pyrite, chalcopyrite, galena, sphalerite, molybdenite, and bornite), tellurides (altaite, calaverite, hessite, muthmannite, petzite, rucklidgeite, sylvanite, tellurobismuthite, tetradymite, and volynskite), and native elements (tellurium and gold). Molybdenite, muthmannite, rucklidgeite, and volynskite are reported for the first time in this deposit. We consider the Dongping gold deposit mainly formed in the Devonian, and the ore‐forming processes and the physicochemical conditions for ore formation can be reconstructed based on our newly identified ore paragenesis, that is, iron oxides → (CO₂ effervescence) → sulfides → (fTe₂/fS₂ ratio increase) → Pb‐Bi‐tellurides → (condensation of H₂Te vapor) → Au‐Ag‐tellurides → (mixing with oxidizing water) → carbonate and microporous gold → secondary minerals → secondary minerals. The logfO₂ values increase from the early to late stages, while the fH₂S and logfS₂ values increase initially and then decrease. CO₂ effervescence is the main mechanism of sulfides precipitation; this sulfidation and condensation of H₂Te vapor lead to deposition of tellurides. The development of microporous gold indicates that the deposit might experience overprint after mineralization. The Dongping gold deposit has a close genetic relationship with the Shuiquangou syenite, and tellurium likely originated from Shuiquangou alkaline magmatic degassing.     

A comparative mineralogical study of Te-rich magmatic-hydrothermal systems in northeastern Greece

Summary Several magmatic-hydrothermal systems in northeastern Greece (western Thrace and Limnos Island) are highly enriched in tellurides which, in addition to native gold and electrum, represent major carriers of precious metals in the ore. Deposition near the porphyry-epithermal transition for several systems is indicated by field relations and by the presence of key minerals (Pb- and Ag-rich tellurides, Bi-sulfosalts and Bi-tellurides/tellurosulfides). Hessite, stützite, sylvanite, petzite, coloradoite, altaite, unnamed Ag-sulfotelluride, native tellurium and electrum are abundant in intermediate sulfidation quartz-carbonate veins together with zincian tetrahedrite-group minerals, chalcopyrite and galena. The presence of hessite, goldfieldite, native gold and enargite or famatinite suggests deposition at a high sulfidation state. The main stage of telluride deposition took place at ∼275 °C at log fTe₂ values of −8.5 to −7.1 and log fS₂ values of −10.8 to −9.0, based on the Fe-content in sphalerite and the sulfide-telluride mineralogy. The close spatial association of telluride mineralization with intrusive centers of intermediate composition, the base metal enrichment and the trace element signature involving Au, Ag, Te, Bi, Sn and Mo suggest that ore-forming components were introduced at the porphyry-epithermal transition. Potential sources of tellurium are the high-K calc-alkaline (western Thrace) to shoshonitic (Limnos) intrusive rocks.     

The distribution of platinum group elements (PGE) and other chalcophile elements among sulfides from the Creighton Ni–Cu–PGE sulfide deposit, Sudbury, Canada, and the origin of palladium in pentlandite

Concentrations of platinum group elements (PGE), Ag, As, Au, Bi, Cd, Co, Mo, Pb, Re, Sb, Se, Sn, Te, and Zn, have been determined in base metal sulfide (BMS) minerals from the western branch (402 Trough orebodies) of the Creighton Ni–Cu–PGE sulfide deposit, Sudbury, Canada. The sulfide assemblage is dominated by pyrrhotite, with minor pentlandite, chalcopyrite, and pyrite, and they represent monosulfide solid solution (MSS) cumulates. The aim of this study was to establish the distribution of the PGE among the BMS and platinum group minerals (PGM) in order to understand better the petrogenesis of the deposit. Mass balance calculations show that the BMS host all of the Co and Se, a significant proportion (40–90%) of Os, Pd, Ru, Cd, Sn, and Zn, but very little (<35%) of the Ag, Au, Bi, Ir, Mo, Pb, Pt, Rh, Re, Sb, and Te. Osmium and Ru are concentrated in equal proportions in pyrrhotite, pentlandite, and pyrite. Cobalt and Pd (∼1 ppm) are concentrated in pentlandite. Silver, Cd, Sn, Zn, and in rare cases Au and Te, are concentrated in chalcopyrite. Selenium is present in equal proportions in all three BMS. Iridium, Rh, and Pt are present in euhedrally zoned PGE sulfarsenides, which comprise irarsite (IrAsS), hollingworthite (RhAsS), PGE-Ni-rich cobaltite (CoAsS), and subordinate sperrylite (PtAs₂), all of which are hosted predominantly in pyrrhotite and pentlandite. Silver, Au, Bi, Mo, Pb, Re, Sb, and Te are found predominantly in discrete accessory minerals such as electrum (Au–Ag alloy), hessite (Ag₂Te), michenerite (PdBiTe), and rhenium sulfides. The enrichment of Os, Ru, Ni, and Co in pyrrhotite, pentlandite, and pyrite and Ag, Au, Cd, Sn, Te, and Zn in chalcopyrite can be explained by fractional crystallization of MSS from a sulfide liquid followed by exsolution of the sulfides. The early crystallization of the PGE sulfarsenides from the sulfide melt depleted the MSS in Ir and Rh. The bulk of Pd in pentlandite cannot be explained by sulfide fractionation alone because Pd should have partitioned into the residual Cu-rich liquid and be in chalcopyrite or in PGM around chalcopyrite. The variation of Pd among different pentlandite textures provides evidence that Pd diffuses into pentlandite during its exsolution from MSS. The source of Pd was from the small quantity of Pd that partitioned originally into the MSS and a larger quantity of Pd in the nearby Cu-rich portion (intermediate solid solution and/or Pd-bearing PGM). The source of Pd became depleted during the diffusion process, thus later-forming pentlandite (rims of coarse-granular, veinlets, and exsolution flames) contains less Pd than early-forming pentlandite (cores of coarse-granular).     

Tellurium-bearing minerals in zoned sulfide chimneys from Cu-Zn massive sulfide deposits of the Urals, Russia

Tellurium-bearing minerals are generally rare in chimney material from mafic and bimodal felsic volcanic hosted massive sulfide (VMS) deposits, but are abundant in chimneys of the Urals VMS deposits located within Silurian and Devonian bimodal mafic sequences. High physicochemical gradients during chimney growth result in a wide range of telluride and sulfoarsenide assemblages including a variety of Cu-Ag-Te-S and Ag-Pb-Bi-Te solid solution series and tellurium sulfosalts. A change in chimney types from Fe-Cu to Cu-Zn-Fe to Zn-Cu is accompanied by gradual replacement of abundant Fe-, Co, Bi-, and Pb- tellurides by Hg, Ag, Au-Ag telluride and galena-fahlore with native gold assemblages. Decreasing amounts of pyrite, both colloform and pseudomorphic after pyrrhotite, isocubanite ISS and chalcopyrite in the chimneys is coupled with increasing amounts of sphalerite, quatz, barite or talc contents. This trend represents a transition from low- to high sulphidation conditions, and it is observed across a range of the Urals deposits from bimodal mafic- to bimodal felsic-hosted types: Yaman-Kasy → Molodezhnoye → Uzelga → Valentorskoye → Oktyabrskoye → Alexandrinskoye → Tash-Tau → Jusa.     

Tellurides, selenides and Bi-mineral assemblages from the Río Narcea Gold Belt, Asturias, Spain: genetic implications in Cu–Au and Au skarns

Summary Gold ores in skarns from the Río Narcea Gold Belt are associated with Bi–Te(–Se)-bearing minerals. These mineral assemblages have been used to compare two different skarns from this belt, a Cu–Au skarn (calcic and magnesian) from the El Valle deposit, and a Au-reduced calcic skarn from the Ortosa deposit. In the former, gold mineralization occurs associated with Cu–(Fe)-sulfides (chalcopyrite, bornite, chalcocite-digenite), commonly in the presence of magnetite. Gold occurs mainly as native gold and electrum. Au-tellurides (petzite, sylvanite, calaverite) are locally present; other tellurides are hessite, clausthalite and coloradoite. The Bi-bearing minerals related to gold are Bi-sulfosalts (wittichenite, emplectite, aikinite, bismuthinite), native bismuth, and Bi-tellurides and selenides (tetradymite, kawazulite, tsumoite). The speciation of Bi-tellurides with Bi/Te(Se + S) ≤ 1, the presence of magnetite and the abundance of precious metal tellurides and clausthalite indicate fO₂ conditions within the magnetite stability field that locally overlap the magnetite-hematite buffer. In Ortosa deposit, gold essentially occurs as native gold and maldonite and is commonly related to pyrrhotite and to the replacement of l?llingite by arsenopyrite, indicating lower fO₂ conditions for gold mineralization than those for El Valle deposit. This fact is confirmed by the speciation of Bi-tellurides and selenides (hedleyite, joséite-B, joséite-A, ikunolite-laitakarite) with Bi/Te(+ Se + S) ≥ 1.     

Silver-rich telluride mineralization at Mount Charlotte and Au–Ag zonation in the giant Golden Mile deposit,Kalgoorlie, Western Australia

The gold deposits at Kalgoorlie in the 2.7-Ga Eastern Goldfields Province of the Yilgarn Craton, Western Australia, occur adjacent to the D2 Golden Mile Fault over a strike of 8 km within a district-scale zone marked by porphyry dykes and chloritic alteration. The late Golden Pike Fault separates the older (D2) shear zone system of the Golden Mile (1,500 t Au) in the southeast from the younger (D4) quartz vein stockworks at Mt Charlotte (126 t Au) in the northwest. Both deposits occur in the Golden Mile Dolerite sill and display inner sericite–ankerite alteration and early-stage gold–pyrite mineralization replacing the wall rocks. Late-stage tellurides account for 20 % of the total gold in the first, but for <1 % in the second deposit. In the Golden Mile, the main telluride assemblage is coloradoite?+?native gold (898–972 fine)?+?calaverite?+?petzite?±?krennerite. Telluride-rich ore (>30 g/t Au) is characterized by Au/Ag?=?2.54 and As/Sb?=?2.6–30, the latter ratio caused by arsenical pyrite. Golden Mile-type D2 lodes occur northwest of the Golden Pike Fault, but the Hidden Secret orebody, the only telluride bonanza mined (10,815 t at 44 g/t Au), was unusually rich in silver (Au/Ag?=?0.12–0.35) due to abundant hessite. We describe another array of silver-rich D2 shear zones which are part of the Golden Mile Fault exposed on the Mt Charlotte mine 22 level. They are filled with crack-seal and pinch-and-swell quartz–carbonate veins and are surrounded by early-stage pyrite?+?pyrrhotite disseminated in a sericite–ankerite zone more than 6 m wide. Gold grade (0.5–0.8 g/t) varies little across the zone, but Au/Ag (0.37–2.40) and As/Sb (1.54–13.9) increase away from the veins. Late-stage telluride mineralization (23 g/t Au) sampled in one vein has a much lower Au/Ag (0.13) and As/Sb (0.48) and comprises scheelite, pyrite, native gold (830–854 fine), hessite, and minor pyrrhotite, altaite, bournonite, and boulangerite. Assuming 250–300 °C, gold–hessite compositions indicate a fluid log f _Te2 of ?11.5 to ?10, values well below the stability of calaverite. The absence of calaverite and the dominance of hessite in the D2 lodes of the Mt Charlotte area point to a kilometer-scale mineral and Au/Ag zonation along the Golden Mile master fault, which is attributed to a lateral decrease in peak tellurium fugacity of the late-stage hydrothermal fluid. The As/Sb ratio may be similarly zoned to lower values at the periphery. The D4 gold–quartz veins constituting the Mt Charlotte orebodies represent a younger hydrothermal system, which did not contribute to metal zonation in the older one.     

Composition and conditions of formation of gold-telluride mineralization in the Tissa-Sarkhoi gold-bearing province (East Sayan)

The structure and petrologic composition of new gold-ore provinces in southeastern East Sayan (Tissa-Sarkhoi cluster) are considered. Several morphogenetic types of gold mineralization have been established: quartz veins with beresitization zones, veinlet-disseminated ores in granitoids, and listwaenitization and sulfidation zones in effusions of the Sarkhoi Group and intrusive rocks of the Late Riphean Khorin-Gol complex. According to geochronological dates and some mineralogical and geochemical features, the gold mineralization is close in age to these Precambrian island-arc complexes. Parageneses of two stages of ore formation have been recognized: early high-temperature (250–460 °C) gold-pyrite and late low-temperature (110–280 °C) gold-telluride. The latter mineralization is widespread and is represented by tellurides of Au, Ag, Pb, Bi, and Ni — petzite, calaverite, hessite, tellurobismuthite, altaite, and melonite. Native gold associated with these tellurides is characterized by a fineness of 750–900‰. The intimate temporal and spatial relationships of the gold mineralization with island-arc volcanoplutonic complexes and the wide occurrence of its veinlet-disseminated type suggest that this is porphyry gold mineralization related to the Late Riphean-Vendian island-arc magmatism.     

安徽铜陵新桥Cu-Au-S矿床黄铁矿微量元素LA-ICP-MS原位测定及其对矿床成因的制约

激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)是一种固体微区分析新技术。用该技术来分析矿床中硫化物的微量元素组成可以为研究成矿流体特征、矿床成因及找矿勘探提供有关的科学信息。文中以安徽铜陵矿集区内新桥Cu-Au-S矿床中的黄铁矿为研究对象,在详细的野外观察和室内鉴定的基础上,将矿床中的黄铁矿分为具有沉积特征的胶状黄铁矿(PyⅠ)、具有变形重结晶和热液叠加作用特征的细粒他形黄铁矿(PyⅡ)和具热液成因特征的中—粗粒自形黄铁矿(PyⅢ)3种类型。LA-ICP-MS原位微量元素测定结果显示,PyⅠ中相对富含Ti、Co、Ni、As、Se、Te;PyⅡ继承了PyⅠ中富含Ti、Co、Ni、As、Se、Te、Bi的特征,同时还含有不均匀分布的少量成矿元素(Cu、Pb、Zn、Au、Ag);PyⅢ中成矿元素Cu、Pb、Zn、Ag、Au以及Bi元素的含量较高,Co、Ni、As的含量较低。在元素赋存状态方面,Co、Ni、As、Se和Te均以类质同象的形式进入到了黄铁矿的晶格中;Bi在PyⅡ中主要以含Bi矿物的微细包裹体形式存在,而在PyⅢ中的Bi还部分取代了Fe而占据了晶格;Cu、Pb、Zn、Au、Ag这些成矿元素中,Cu和Zn分别以黄铜矿和闪锌矿的矿物包裹体存在于黄铁矿中;PyⅡ中所含的少量Au、Ag,可能分别以自然金和自然银的形式存在,而在PyⅢ中Au可能主要以银金矿的形式存在,Ag除了以银金矿的形式存在以外还可能赋存于黄铁矿中含铋的矿物包裹体内;Pb主要赋存于黄铁矿中的方铅矿或含铋矿物的包裹体中。在综合分析黄铁矿的结构形态和微量元素组成特征的基础上认为,PyⅠ型黄铁矿可能形成于前人提出的晚古生代海底沉积或喷流沉积环境,PyⅡ和PyⅢ型黄铁矿分别形成于中生代区域构造变形-热液叠加改造的过渡环境和热液环境,PyⅡ和PyⅢ的形成时间相近。新桥矿床的形成可能经历了晚古生代海底沉积或喷流沉积期和燕山期热液期,胶黄铁矿主要形成于沉积成矿期,而矿床中成矿物质Cu、Pb、Zn、Au、Ag等主要来自燕山期岩浆侵入作用形成的热液成矿系统。     

北山地区金矿床金的赋存状态和金矿物特征

甘肃北山地区金矿床主要有岩浆热液型金矿床和与韧性剪切带有关的金矿床,矿化类型为石英脉型和蚀变岩型。金多呈独立金矿物形式出现,少放许呈分散状;金矿物以银金矿为主,次为自然金,平均成色７７２;金矿物以粒间金、裂隙金、连生金、连生金和包体金等形成嵌布于石英、黄铁矿、方铅矿及闪锌矿等主要载物较为发育。金矿物特征反映出本区金矿床的成矿物质主要来源于变质岩,华力西－印支期中酸性岩浆活动是主要的动力源。     

Au–Ag–Te Mineralization of the Low‐Sulfidation Epithermal Aginskoe Deposit,Central Kamchatka,Russia

Mineralogic studies of major ore minerals and fluid inclusion analysis in gangue quartz were carried out for the for the two largest veins, the Aginskoe and Surprise, in the Late Miocene Aginskoe Au–Ag–Te deposit in central Kamchatka, Russia. The veins consist of quartz–adularia–calcite gangue, which are hosted by Late Miocene andesitic and basaltic rocks of the Alnei Formation. The major ore minerals in these veins are native gold, altaite, petzite, hessite, calaverite, sphalerite, and chalcopyrite. Minor and trace minerals are pyrite, galena, and acanthine. Primary gold occurs as free grains, inclusions in sulfides, and constituent in tellurides. Secondary gold is present in form of native mustard gold that usually occur in Fe‐hydroxides and accumulates on the decomposed primary Au‐bearing tellurides such as calaverite, krennerite, and sylvanite. K–Ar dating on vein adularia yielded age of mineralization 7.1–6.9 Ma. Mineralization of the deposit is divided into barren massive quartz (stage I), Au–Ag–Te mineralization occurring in quartz‐adularia‐clays banded ore (Stage II), intensive brecciation (Stage III), post‐ore coarse amethyst (Stage IV), carbonate (Stage V), and supergene stages (Stage VI). In the supergene stage various secondary minerals, including rare bilibinskite, bogdanovite, bessmertnovite metallic alloys, secondary gold, and various oxides, formed under intensely oxidized conditions. Despite heavy oxidation of the ores in the deposit, Te and S fugacities are estimated as Stage II tellurides precipitated at the log f Te₂ values ?9 and at log fS₂ ?13 based on the chemical compositions of hypogene tellurides and sphalerite. Homogenization temperature of fluid inclusions in quartz broadly ranges from 200 to 300°C. Ore texture, fluid inclusions, gangue, and vein mineral assemblages indicate that the Aginskoe deposit is a low‐sulfidation (quartz–adularia–sericite) vein system.     

Shallow submarine epithermal Pb–Zn–Cu–Au–Ag–Te mineralization on western Milos Island,Aegean Volcanic Arc,Greece: Mineralogical,geological and geochemical constraints

Milos Island contains several epithermal deposits (e.g., Profitis Ilias–Chondro Vouno Pb–Zn–Ag–Au–Te–Cu, Triades–Galana–Agathia–Kondaros Pb–Zn–Ag–Bi–W–Mo ± Cu–Au, and Katsimoutis–Kondaros–Vani Pb–Zn–Ag–Mn) of Late Pliocene to Early Pleistocene age. These deposits are hosted in calc-alkaline volcanic rocks emplaced as a result of three successive magma pulses in an emergent volcanic edifice: submarine rhyolitic to rhyodacitic cryptodomes at ca. 2.7. Ma (Profitis Ilias–Chondro Vouno), submarine to subaerial andesite to dacite domes at ca. 2.2 to 1.5 Ma (Triades–Galana–Kondaros–Katsimouti–Vani). Hydrothermal alteration of the volcanic rocks includes advanced argillic- (both hypogene and steam-heated), argillic, phyllic, adularia-sericite and propylitic types. In the northern sector (Triades–Galana–Agathia–Kondaros), initial magma degassing derived from andesitic–dacitic intrusives along NE–SW to E–W trending faults resulted in the development of pre-ore hypogene advanced argillic alteration (dickite, alunite, ± diaspore, pyrophyllite, halite, and pyrite) in a submarine environment. Mineralogical data indicate common features among the Profitis Ilias–Chondro Vouno, Kondaros–Katsimoutis–Vani and Triades–Galana mineralized centers, all of which are characterized by the presence of galena, Fe-poor sphalerite, and chalcopyrite as well as abundant barite, adularia, sericite and, to a lesser extent, calcite, which are typical of intermediate-sulfidation epithermal type deposits. Locally, at Triades–Galana and Kondaros–Agathia, high-sulfidation conditions prevailed as suggested by the presence of coexisting enargite and covellite. The high silver and gold content of the western Milos deposits is derived from Ag-bearing sulfosalts (polybasite, pearceite, pyrargyrite, freibergite) and tellurides. Gold at Profitis Ilias, both as native gold and silver-gold tellurides, is present in base-metal precipitates within multicomponent blebs, which recrystallized to form hessite, petzite, altaite, coloradoite, and native gold. Mineralogical evidence (e.g. microchimney structures, copper sulfides, widespread occurrence of barite, aragonite) suggests that precious metal mineralization in western Milos mineralization formed in a submarine setting.We present information on the surface distribution of Au, Ag, Cu, Pb, Zn, As, Sb, Hg, Mo, Bi, W and Cd at western Milos. Gold is enriched at Profitis Ilias–Chondro Vouno deposits and to a lesser extent at Triades–Galana. Arsenic is absent from the southern sector but shows elevated concentrations together with molybdenum, bismuth and tungsten at the northern sector (Triades–Galana, Vani deposits). The differences in precious and base metal abundances may be related to the depths at which the deposits are exposed, and/or different sources of magma. The metal signatures of the Triades–Galana and Agathia–Kondaros–Katsimouti–Vani (Mo–Bi–W–As–Hg–Ag–Au) occurrences compared to Profitis Ilias (Te–Au–Ag) reflect different sources of magma (dacite–rhyodacite for Profitis Ilias, andesite–dacite for Triades–Galana, and dacite for Kondaros–Katsimoutis). The enrichment of Te, Mo, W, and Bi in the deposits is a strong indication of a direct magmatic contribution of these metals.At western Milos, precious and base-metal vein mineralization was deposited during episodic injection of magmatic volatiles and dilution of the hydrothermal fluids by seawater. The mineralization represents seafloor/sub-seafloor precipitation of sulfides that formed in stockwork zones. Base and precious metal mineralization formed from intermediate- to high-sulfidation state fluids and mostly under boiling conditions as indicated by the widespread occurrence of adularia associated with metallic mineralization. We speculate that the widespread occurrence of boiling and the shallow depth of the precious- and base-metal emplacement prevented the formation of seafloor massive sulfides.     

Tellurides associated with volcanogenic massive sulfide (VMS) mineralization at Yuinmery and Austin,Western Australia

Tellurides have been identified in VMS mineralization at Yuinmery and Austin in the Archean Youanmi Terrane, Yilgarn Craton, Western Australia. Tellurides identified at Yuinmery include: petzite, stützite, hessite, tellurobismuthite, altaite, rucklidgeite, melonite, mattagamite and a nickel-cobalt telluride with chemical composition similar to cobaltian melonite which has previously only been reported once before. Tellurides and related minerals identified at Austin include: stützite, volynskite, tellurobismuthite, tetradymite, tsumoite, rucklidgeite, altaite and a mineral with the formula (Bi,Pb)₃(Te,Se,S)₄ corresponding to the rare mineral poubaite. The tellurides are interpreted to have been deposited with the base metals on and immediately below the sea floor by very hot fluids during a period of quiescence in the volcanism. The mineral assemblage suggests that the fluids in both areas had high ƒTe₂ and were oxidising but close to the pyrrhotite-pyrite boundary. The presence of Ni and Co tellurides at Yuinmery but not at Austin is probably due to the derivation of the fluids at Yuinmery from mafic volcanism whereas at Austin the succession is dominantly felsic. The metamorphic grade at Austin is higher than that at Yuinmery and this may have resulted in some re-crystallization of tellurides and tellurosulfides.     

山东省平邑归来庄碲型金矿床碲元素地球化学特征及成矿机制探讨

归来庄贫硫氧化型低温热液碲金矿床中金及碲化物矿物主要有自然金、碲金矿、碲金铜矿、碲银矿、碲金银矿、碲铅矿、碲镍矿、碲汞矿及自然碲等。金元素主要来源于泰山群山草峪组的片麻岩及寒武一奥陶系海相碳酸盐岩;碲元素主要是由铜石杂岩体的二长质、正长质等中偏碱性岩浆从地球深部的上地幔、下地壳带入矿区并进入由岩浆水及大气降水等组成的成矿热液中,与金元素形成碲金络合物进行搬迁、富集,因成矿体系的ｐＨ、Ｅｈ等物理化学