Journal articles: 'Epithermal mineralisation'

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Μιχαήλ, Κ., and Μ. Δημήτρουλα. "HYDROTHERMAL ALTERATION AND MINERALIZATION OF THE PETROTA EPITHERMAL SYSTEMS (W.THRACE, GREECE)." Bulletin of the Geological Society of Greece 36, no. 1 (January 1, 2004): 369. http://dx.doi.org/10.12681/bgsg.16687.

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At the Petrota graben important epithermal zones are developed. On the basis of the mineral assemblages of alteration zones and the type of the host rocks, the epithermal zones can be grouped into three epithermal systems: 1. Perama epithermal system 2. Mavrokoryfi epithermal system and 3. Othondoto epithermal system Hydrothermal alteration zones are developed within volcanoclastic rocks - epiclastic sandstones, andésite tuffs (Perama epithermal system), hyaloclastites (Mavrokoryfi) and rhyolitic rocks (Othondoto). Silicification (in various types) and advanced argillic alteration are the most important alteration zones and are established on the largest scale. Ore mineralisation occurs as veins, veinlets in silicification zones or secondary mineralisation in the supergene zone (Perama epithermal system). Disseminated ore mineralization is also found in the silicification zone at Othondoto and Mavrokoryfi epithermal systems. Based on the geological environment, the type of hydrothemal alteration zones (silicification and advanced argillic alteration) and the mineral compositon of the ore (enargite- luzonite), the hydrothermal systems of Petrota graben can be referred as high sulfidation systems.

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Cidu, R. "Hydrogeochemistry around an Epithermal System Hosting Gold Mineralisation." Mineralogical Magazine 58A, no. 1 (1994): 173–74. http://dx.doi.org/10.1180/minmag.1994.58a.1.93.

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Smith, Daniel J., Jon Naden, and Gawen R. T. Jenkin. "Host rock effects on epithermal Au-Te mineralisation." Applied Earth Science 125, no. 2 (April 2, 2016): 95–96. http://dx.doi.org/10.1080/03717453.2016.1166668.

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SKARPELIS, N. "Geodynamics and evolution of the Miocene mineralization in the Cycladic - Pelagonian belt, Hellenides." Bulletin of the Geological Society of Greece 34, no. 6 (January 1, 2002): 2191. http://dx.doi.org/10.12681/bgsg.16862.

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The paper aims to provide a sound account of the type of Miocene mineralisations in the Cycladic – Pelagonian belt and their relationship with the geodynamic evolution of the area. Skarn and manto types, epithermal precious and base metals mineralisation, and vein magnesite in ultramafics are associated to distinct stages of the geodynamic evolution of the belt. Extensional tectonics favoured their generation. Late stages of extensional tectonics resulted in the formation of vertical to subvertical NW-SE trending fault zones, which were then used as conduits for ascending hydrothermal fluids. The relationship between the geodynamics and the metallogenetic evolution of the belt is discussed on the basis of available data on the geology of four critical areas: Tinos and Mykonos islands, Laurium and Northern Euboea.

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Sutarto, Sutarto, Arifudin Idrus, Agung Harijoko, Lucas Donny Setijadji, and Franz Michael Meyer. "VEINS AND HYDROTHERMAL BRECCIAS OF THE RANDU KUNING PORPHYRY Cu-Au AND EPITHERMAL Au DEPOSITS AT SELOGIRI AREA, CENTRAL JAVA INDONESIA." Journal of Applied Geology 7, no. 2 (July 27, 2015): 82. http://dx.doi.org/10.22146/jag.26982.

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The Randu Kuning prospect is situated at Selogiri area, Wonogiri, Central Java, Indonesia. This location is about 40 km to the south-east from Solo city or approximately 70 km east of Yogyakarta city. Many Tertiary dioritic rocks related alterationmineralisation were found at the Randu Kuning area and its vicinity, including hornblende microdiorite, hornblende-pyroxene diorite and quartz diorite. Mineralisation type of the Randu Kuning prospect was interpreted as porphyry Cu-Au and a number epithermal Au-base metals deposits in its surrounding. The closed existing of porphyry Cu-Au and epithermal Au-base metals type deposits at the Randu Kuning area produced a very complex of veins and hydrothermal breccias crosscutting relationship. A lot of porphyry veins types were found and observed at the Randu Kuning area, and classiﬁed into at least seven types. Most of the porphyry veins were cross cut by epithermal type veins. Many epithermal veins also are found and crosscut into deeply porphyry vein types. There are genetically at least two type of hydrothermal breccias have recognized in the research area, i.e. magmatic-hydrothermal breccia and phreatomagmatic breccia. Magmatic hydrothermal breccias are mostly occured in contact between hornblende microdiorite or quartz diorite and hornblende-pyroxene diorite, characterized by angular fragments/clasts supported or inﬁlled by silicas, carbonates and sulphides matrix derived from hydrothermal ﬂuids precipitation. Phreatomagmatic breccias are characterized by abundant of the juvenile clasts, indicated contact between hot magma with ﬂuid or water as well as many wall rock fragments such as altered diorites and volcaniclastic rock clasts set in clastical matrix. The juvenile clasts usually compossed by volcanic glasses and aphanitic rocks in rounded-irregular shape. Both veining and brecciation processes have an important role in gold and copper mineralisation of the Randu Kuning Porphyry Cu-Au and epithermal Au-base metals deposits, mostly related to the presence of quartz veins/veinlets containing signiﬁcant sulphides, i.e., quartz with thin centre line sulphides (Abtype) veins, pyrite±chalcopyrite (C type) veinlets, pyrite+quartz± chalcopyrire±carbonate (D type) veins of porphyry types as well as epithermal environment quarts+ sulphides+carbonate veins.

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Radmard, Kaikhosrov, Hassan Zamanian, Mohamad Reza Hosseinzadeh, and Ahmad Ahmadi Khalaji. "Geochemistry and statistical analyses of porphyry system and epithermal veins at Hizehjan in northwestern Iran." Geologos 23, no. 3 (December 20, 2017): 183–200. http://dx.doi.org/10.1515/logos-2017-0020.

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Abstract Situated about 130 km northeast of Tabriz (northwest Iran), the Mazra’eh Shadi deposit is in the Arasbaran metallogenic belt (AAB). Intrusion of subvolcanic rocks, such as quartz monzodiorite-diorite porphyry, into Eocene volcanic and volcano-sedimentary units led to mineralisation and alteration. Mineralisation can be subdivided into a porphyry system and Au-bearing quartz veins within andesite and trachyandesite which is controlled by fault distribution. Rock samples from quartz veins show maximum values of Au (17100 ppb), Pb (21100 ppm), Ag (9.43ppm), Cu (611ppm) and Zn (333 ppm). Au is strongly correlated with Ag, Zn and Pb. In the Au-bearing quartz veins, factor group 1 indicates a strong correlation between Au, Pb, Ag, Zn and W. Factor group 2 indicates a correlation between Cu, Te, Sb and Zn, while factor group 3 comprises Mo and As. Based on Spearman correlation coefficients, Sb and Te can be very good indicator minerals for Au, Ag and Pb epithermal mineralisation in the study area. The zoning pattern shows clearly that base metals, such as Cu, Pb, Zn and Mo, occur at the deepest levels, whereas Au and Ag are found at higher elevations than base metals in boreholes in northern Mazra’eh Shadi. This observation contrasts with the typical zoning pattern caused by boiling in epithermal veins. At Mazra’eh Shadi, quartz veins containing co-existing liquid-rich and vapour-rich inclusions, as strong evidence of boiling during hydrothermal evolution, have relatively high Au grades (up to 813 ppb). In the quartz veins, Au is strongly correlated with Ag, and these elements are in the same group with Fe and S. Mineralisation of Au and Ag is a result of pyrite precipitation, boiling of hydrothermal fluids and a pH decrease.

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Torres, Melgarejo, Torró, Camprubí, Castillo-Oliver, Artiaga, Campeny, et al. "The Poopó Polymetallic Epithermal Deposit, Bolivia: Mineralogy, Genetic Constraints, and Distribution of Critical Elements." Minerals 9, no. 8 (July 31, 2019): 472. http://dx.doi.org/10.3390/min9080472.

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The tin-rich polymetallic epithermal deposit of Poopó, of plausible Late Miocene age, is part of the Bolivian Tin Belt. As an epithermal low sulfidation mineralisation, it represents a typological end-member within the “family” of Bolivian tin deposits. The emplacement of the mineralisation was controlled by the regional fault zone that constitutes the geological border between the Bolivian Altiplano and the Eastern Andes Cordillera. In addition to Sn and Ag, its economic interest resides in its potential in critical elements as In, Ga and Ge. This paper provides the first systematic characterisation of the complex mineralogy and mineral chemistry of the Poopó deposit with the twofold aim of identifying the mineral carriers of critical elements and endeavouring to ascertain plausible metallogenic processes for the formation of this deposit, by means of a multi-methodological approach. The poor development of hydrothermal alteration assemblage, the abundance of sulphosalts and the replacement of löllingite and pyrrhotite by arsenopyrite and pyrite, respectively, indicate that this deposit is ascribed to the low-sulphidation subtype of epithermal deposits, with excursions into higher states of sulphidation. Additionally, the occurrence of pyrophyllite and topaz has been interpreted as the result of discrete pulses of high-sulphidation magmatic fluids. The δ34SVCDT range in sulphides (−5.9 to −2.8‰) is compatible either with: i. hybrid sulphur sources (i.e., magmatic and sedimentary or metasedimentary); or ii. a sole magmatic source involving magmas that derived from partial melting of sedimentary rocks or underwent crustal assimilation. In their overall contents in critical elements (In, Ga and Ge), the key minerals in the Poopó deposit, based on their abundance in the deposit and compositions, are rhodostannite, franckeite, cassiterite, stannite and, less importantly, teallite, sphalerite and jamesonite.

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Hakim, F. R., and A. Idrus. "Preliminary Study of Geology, Alteration and Ore Mineralisation at East Motoling Area, South Minahasa District, North Sulawesi, Indonesia." IOP Conference Series: Earth and Environmental Science 921, no. 1 (November 1, 2021): 012034. http://dx.doi.org/10.1088/1755-1315/921/1/012034.

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Abstract The East Motoling area is one of the prospect areas in the Minahasa region of North Sulawesi, which has indications of low sulfidation epithermal-type mineralization. The research was conducted as a preliminary study to determine the characteristics of geological conditions, alteration, and ore mineralization in the epithermal system. The research method is divided into two main parts, such as fieldwork including surface geological mapping (lithology, stratigraphy, geomorphology, structural geology, alteration and mineralization) and laboratory analysis methods including petrographic analysis. The stratigraphy of the study area consists of altered volcaniclastic breccia, altered lapilli tuff, altered tuff, limestone, welded lapilli tuff, and andesitic breccia. Volcaniclastic breccia, altered lapilli tuff, and altered tuff, member of the Volcanic Rock Formation which is Late – Middle Miocene age, are the host rock for ore mineralization and hydrotermal alteration process. There are 3 types of alterations that have developed, namely argillic (illite + quartz ± kaolinite), sericitic (sericite + illite ± chlorite), and propylitic (chlorite + epidote ± illite). The dextral slip fault with NW – SE trend present as a main control structure to formation of extention fracture/vein. The epithermal veins are relatively north-northeast – south-southwest, north-northwest – south-southeast, and northwest – southeast. The textures of the veins divided into 7 main groups, namely that is bladed-quartz, breccia, calcedony, colloform, comb, mold, and massive quartz. Ore mineralization is forms in the veins as pyrite and banded sulfide. Apart from that, the disseminated pyrite also limitedly found around the veins.

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Micklethwaite, Steven. "Mechanisms of faulting and permeability enhancement during epithermal mineralisation: Cracow goldfield, Australia." Journal of Structural Geology 31, no. 3 (March 2009): 288–300. http://dx.doi.org/10.1016/j.jsg.2008.11.016.

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McCarroll, Robert Jak, Ian T. Graham, Russell Fountain, Karen Privat, and Jon Woodhead. "The Ojolali region, Sumatra, Indonesia: Epithermal gold–silver mineralisation within the Sunda Arc." Gondwana Research 26, no. 1 (July 2014): 218–40. http://dx.doi.org/10.1016/j.gr.2013.08.013.

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Idrus, Arifudin, Fahmi Hakim, I. Wayan Warmada, Mochammad Aziz, Jochen Kolb, and Franz Michael Meyer. "GEOLOGY AND ORE MINERALISATION OF NEOGENE SEDIMENTARY ROCK HOSTED LS EPITHERMAL GOLD DEPOSIT AT PANINGKABAN, BANYUMAS REGENCY, CENTRAL JAVA, INDONESIA." Journal of Applied Geology 7, no. 2 (July 27, 2015): 75. http://dx.doi.org/10.22146/jag.26981.

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Low suphidation (LS) epithermal gold deposits were recently found in the Paningkaban area, Central Java province, Indonesia, with more than ﬁve hundred artisanal gold miners currently operating in the area. This study is aimed to understand the geological factors controlling the gold mineralization and to characterize the alteration and ore mineralogy of the deposit. Several epithermal veins/veinlets trending N–S, NW–SE, and NE–SW are hosted by Tertiary turbiditic volcanoclastic sedimentary rocks of the Halang formation. This formation is composed of looping gradation of sandstone and siltstone units. Pre- and syn-mineralization structures such as extension joints, normal sinitral fault and sinitral fault control the gold mineralization. Fault movements formed dilational jogs manifested by NW-SE-trending en-echelon tension gash veins. Four main alteration zones are identiﬁed: (a) phyllic, (b) argillic, (c) sub propylitic and (d) weak subpropylitic. Ore minerals consist of native gold, electrum, native silver, pyrite, chalcopyrite, sphalerite, galena, arsenopyrite, cubanite, marcasite, covellite and tennantite, which are commonly associated withargillic alteration. Vein structures such as massive, swarm and low angle veins, stockwork and veins dispersed in diatreme breccia are present. Normal banded, cockade, crustiform, bladed carbonates as well as, comb and saccharoidal features are the typical vein textures. It is noteworthy that the veins are basically composed of carbonate with minor quartz at gold grades of up to 83 g/t Au. Based on the vein structures and textures, four stages of ore mineralization were developed consisting of (a) early stage (ﬂuidized breccia and quartz vein), (b) middle stage (carbonate base metal), (c) late stage (late carbonate), and supergene stage. Gold mineralization originated mainly during middle and late stages, particularly in association with cockade, crustiform, bladed carbonate base metal veins. Based on those various features, the LS epithermal deposit in the study area is categorized as carbonate-base metalgold mineralization type.

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Titisari, A. D., D. Phillips, I. W. Warmada, Hartono, and A. Idrus. "40Ar/39Ar geochronology of the Pongkor low sulfidation epithermal gold mineralisation, West Java, Indonesia." Ore Geology Reviews 119 (April 2020): 103341. http://dx.doi.org/10.1016/j.oregeorev.2020.103341.

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Hamilton, Ayrton, Kathleen Campbell, Julie Rowland, and Patrick Browne. "The Kohuamuri siliceous sinter as a vector for epithermal mineralisation, Coromandel Volcanic Zone, New Zealand." Mineralium Deposita 52, no. 2 (April 19, 2016): 181–96. http://dx.doi.org/10.1007/s00126-016-0658-8.

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Perkins, Rebecca J., Frances J. Cooper, Brian Tattitch, Jon Naden, and Daniel J. Condon. "The Kassiteres porphyry – epithermal system, NE Greece: evidence for rapid exhumation leading to sub-economic mineralisation." Applied Earth Science 126, no. 2 (April 3, 2017): 84–85. http://dx.doi.org/10.1080/03717453.2017.1306283.

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Kilias, Stephanos P., Jon Naden, Ioannis Cheliotis, Thomas J. Shepherd, Heleni Constandinidou, John Crossing, and Ioannis Simos. "Epithermal gold mineralisation in the active Aegean Volcanic Arc: the Profitis Ilias deposit, Milos Island, Greece." Mineralium Deposita 36, no. 1 (January 1, 2001): 32–44. http://dx.doi.org/10.1007/s001260050284.

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Bernstein, Stefan, and Christian Knudsen. "Epithermal gold and massive sulphide mineralisation in oil impregnated Palaeogene volcanic rocks of Ubekendt Ejland,West Greenland." Geological Survey of Denmark and Greenland (GEUS) Bulletin 4 (July 20, 2004): 77–80. http://dx.doi.org/10.34194/geusb.v4.4790.

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The discovery in 2002 of a gold mineralised quartz-carbonate vein at Ubekendt Ejland, central West Greenland, yielding 0.6 ppm Au over 0.7 m, led to a reconnaissance sampling project in summer 2003. Most of the accessible quartz-carbonate veins on the south-east coast of the island (Figs 1, 2) were sampled during boat-supported field work. Massive sulphide mineral deposits (Fe-Zn-Pb) were located in the centre of brecciated quartz-carbonate vein systems at several places along the south and south-east coast of the island, and gold anomalies mainly associated with the occurrence of the massive sulphides were identified. Pervasive hydrothermal alteration of the volcanic wall rocks surrounds the quartz-carbonate vein systems, which comprise low-temperature mineral assemblages dominated by dolomite and veined by chalcedony and fibrous silica. Evidence of oil migration into volcaniclastic rocks prior to the intense hydrothermal activity was found in several places in the form of organic carbon, interpreted to be pyrobitumen, that infills pores and cavities in hyaloclastites.

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Skarpelis, Nikos, and Stavros Triantafyllidis. "Environmental impact from supergene alteration and exploitation of a high sulphidation epithermal type mineralisation (Kirki, NE Greece)." Applied Earth Science 113, no. 1 (April 2004): 110–16. http://dx.doi.org/10.1179/037174504225004493.

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Lindley, I. D. "Epithermal and arc-related layered mafic platinum-group element mineralisation in the mafic–ultramafic rocks of eastern Papua." Australian Journal of Earth Sciences 63, no. 4 (May 18, 2016): 393–411. http://dx.doi.org/10.1080/08120099.2016.1212926.

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Daliran, Farahnaz. "The carbonate rock-hosted epithermal gold deposit of Agdarreh, Takab geothermal field, NW Iran—hydrothermal alteration and mineralisation." Mineralium Deposita 43, no. 4 (December 6, 2007): 383–404. http://dx.doi.org/10.1007/s00126-007-0167-x.

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Blanks, Daryl E., David A. Holwell, and Izak Van Coller. "Multi Stage Epithermal Au-Ag Mineralisation in the Kiziltepe Deposit, Western Turkey: Evidence From 3D High Resolution CT Scanning." Acta Geologica Sinica - English Edition 88, s2 (December 2014): 706–7. http://dx.doi.org/10.1111/1755-6724.12375_14.

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Nosyrev, M. Yu, and A. Yu Yurchuk. "Geophysical characteristics of the Belaya Gora gold deposit (Khabarovsk Krai, Russia)." LITHOSPHERE (Russia) 22, no. 1 (March 2, 2022): 118–34. http://dx.doi.org/10.24930/1681-9004-2022-22-1-118-134.

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Research subject. SThe geophysical fields and physical properties of altered gold-bearing rocks within the Belogorskoye ore field and the Belaya Gora gold deposit located in the Khabarovsk Krai.Materials and methods. Magnetic field and the distribution of electrical resistivity and polarisability obtained during land-based surveys as well as magnetic susceptibility, apparent electrical resistivity and polarisability of the samples from trenches and drilling cores have been studied. The analysis of the spatial correlation of the features of geophysical fields and gold mineralisation has been carried out. The physical properties of rocks are analysed depending on the intensity and type of superimposed hydrothermal alterations and gold content.Results. A significant decrease of magnetic susceptibility for all types of altered rock is indicated. Differences in electrical resistivity and polarisability are observed for hydrothermally altered rocks of the pre-ore stage and ore-bearing metasomatites. The former, with a relatively increased electrical resistance, have the highest polarisability (within the ore field), while the latter are characterised by an even higher resistance, but with the significant decrease in polarisability, which remains slightly elevated relative to unaltered rocks. These patterns also determine the geophysical characteristics of the ore field and deposit. The gold ore field is characterised by a significant decrease in the magnetic field intensity, an areal anomaly of increased polarisability, and, in general, an increased apparent electrical resistance. The deposit itself, as an area covering ore bodies, is generally characterised by an even more intensive increase in apparent electrical resistivity and a relative decrease in polarisability against its generally high background.Conclusions. Based on the performed research, a geophysical model of the Belaya Gora gold deposit is proposed, which may be used as a reference during the planning of geophysical works and the interpretation of geophysical data during the exploration works for epithermal gold mineralisation within the volcanic-tectonic structures in the Nizhne-Amursky region.

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Barton, Mark D. "Granitic magmatism and metallogeny of southwestern North America." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 87, no. 1-2 (1996): 261–80. http://dx.doi.org/10.1017/s0263593300006672.

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ABSTRACT:In southwestern North America, late Palaeozoic through Cenozoic granitoids and their related mineral deposits show consistent patterns that can be interpreted in terms of combined provincial, exposure and process controls. Voluminous Cordilleran magmatism began in the Permian and continued with few major interruptions through the Mesozoic and Cenozoic, reaching maximum fluxes in the mid-Jurassic, Late Cretaceous and Oligocene. Two distinctive types of broad-scale igneous suites formed. The first type consists of calc-alkaline to alkaline suites that vary regularly with time from early intermediate-mafic centres to late felsic centres over intervals lasting 20–50 Ma. These suites formed during periods of stable convergence and compressional tectonics, most notably in the late Mesozoic and early–mid-Cenozoic. The second type is compositionally varied, but shows no obvious secular variation in composition. This type formed during neutral to extensional tectonics in the mid-Mesozoic and the mid- to late Cenozoic. Regional (west to east) and secular (old to young) changes from calcic to alkalic compositions do not correspond to basement types; they point to tectonic rather than crustal controls on magmatic evolution, although basement signatures are clearly transmitted in isotopic systematics. Contrasting types of intrusive centres formed in the same lithospheric columns, suggesting that variability reflects thermal and stress regimes, subcrustal magma flux and crustal thickness. Simple thermal and mechanical models of limits on assimilation and magma uprise are broadly consistent with these patterns.Igneous-related mineralisation is ubiquitous where epizonal environments are preserved, thus preservation (and exposure) form the first-order filter on metallogeny. Mineralisation includes porphyry, skarn, epithermal, replacement and syngenetic deposits of widely varying styles, metal contents and links to magmatic heat and materials. Metal contents and alteration styles correlate closely with igneous compositions and are broadly independent of setting, although systematic regional variations in metal ratios are documented. Ore element suites vary from Cu–Au–Fe associated with (quartz) dioritic to monzonitic intrusive centres through Cu–Zn–Mo–Pb–Ag–W–Au associated with broadly granodioritic centres, and finally to F–Mo–Zn–W–Ag–Be associated with metaluminous to strongly peraluminous granitic centres. A model that includes both composition and process controls rationalises this igneous correlation and the lack of strong regional control. Key features are (1) mineralogical controls on fluid compositions and (2) the efficacy of magmatic processes in producing voluminous ore-forming aqueous fluids. This interpretation is supported by field relationships, igneous petrographic and isotopic data, and theoretical considerations.

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Camprubí, Antoni, Eduardo González-Partida, Antonin Richard, Marie-Christine Boiron, Luis González-Ruiz, César Aguilar-Ramírez, Edith Fuentes-Guzmán, Daniel González-Ruiz, and Claire Legouix. "MVT-Like Fluorite Deposits and Oligocene Magmatic-Hydrothermal Fluorite–Be–U–Mo–P–V Overprints in Northern Coahuila, Mexico." Minerals 9, no. 1 (January 18, 2019): 58. http://dx.doi.org/10.3390/min9010058.

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The formation of most fluorite deposits in northern Coahuila (NE Mexico) is explained by MVT models, and is a part of the metallogenic province of northeastern Mexico. However, fluorite skarn deposits also occur in the same region, and there is evidence for late hydrothermal manifestations with no clear origin and evolution. The latter are the main focus of this study; in particular, F–Be–U–Mo–V–P stringers in the Aguachile-Cuatro Palmas area that overprint preexisting fluorite mantos. The region experienced the emplacement of several intrusives during the Eocene and the Oligocene that are collectively grouped into the East Mexico Alkaline Province (EMAP) and postdate MVT-like deposits. Some of these intrusives have associated skarn deposits; most of them are polymetallic, but the unusual El Pilote deposit contains fluorite mineralisation that was remobilised from MVT-like deposits. The formation of the Aguachile deposit (and, collectively, part of the Cuatro Palmas deposit) has been attributed to a shallow retrograde skarn model. The Cuatro Palmas and Las Alicias fluorite deposits consist of MVT-like deposits overprinted by late hydrothermal fluorite mineralisation rich in Be–U–Mo–V–P, and the Aguachile deposit consists entirely of the latter type. The systematic fluid inclusion study of MVT-like, skarn, and late hydrothermal fluorite deposits reveals a very different distribution of temperature and salinity data that allows the discrimination of mineralising fluids for the type of deposit. MVT-like deposits were formed by fluids with temperatures of homogenisation that range between 50 °C and 152 °C and salinities between 5 and 15.5 wt.% NaCl equivalent. The El Pilote fluorite skarn was formed by fluids with temperatures of homogenisation that range between 78 °C and 394 °C and salinities between 5 and 34 wt.% NaCl equivalent, and include CaCl2-rich brines with salinities that range between 24.5 and 29.1 wt.% CaCl2. Late shallow fluorite–Be–U–Mo–V–P hydrothermal deposits were formed by fluids with temperatures of homogenisation that range between 70 °C and 180 °C and salinities between 0.9 and 3.4 wt.% NaCl equivalent; the sole exception to the above is the La Fácil deposit, with salinities that range between 7.9 and 8.8 wt.% NaCl equivalent. While temperatures of homogenisation are similar between MVT-like and late hydrothermal deposits, and both even have hydrocarbon-rich fluid inclusion associations, the salinity of late deposits is similar to that of retrograde skarn fluids, although further diluted. However, homogenisation temperatures tend to be higher in late hydrothermal than in MVT-like deposits, thus making them more similar to retrograde skarn fluids. Although this characteristic cannot solely establish a genetic link between a retrograde skarn model and late hydrothermal deposits in the study area, the characteristics of fluids associated with the latter separate these deposits from those ascribed to an MVT-like model. Assuming that mineralising fluids for late fluorite–Be–U–Mo–V–P hydrothermal deposits may correspond to a retrograde skarn (or “epithermal”) deposit, the source for fluorine may be either from (A) the dissolution of earlier formed MVT-like deposits, (B) the entrainment of remaining F-rich basinal brines, or (C) hydrothermal fluids exsolved from highly evolved magmas. Possibilities A and B are feasible due to a hypothetical situation similar to the El Pilote skarn, and due to the occurrence of hydrocarbon-rich fluid inclusions at the La Fácil deposit. Possibility C is feasible because intrusive bodies related to highly evolved magmas would have provided other highly lithophile elements like Be, U and Mo upon the exsolution of their hydrothermal fluids. Such intrusive bodies occur in both study areas, and are particularly conspicuous at the Aguachile collapse structure.

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Kunov, Angel. "Endogene-supergene systems of epithermal deposits and occurrences of acid-sulfate and adularia-sericite type (cases from Bulgaria) - hypothesis and models." Geologica Balcanica 33, no. 3-4 (December 30, 2003): 33–48. http://dx.doi.org/10.52321/geolbalc.33.3-4.33.

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The epithermal acid-sulfate and adularia-sericite deposits аrе among the main sources of raw mаterials as well as among the most interesting subject of study and genetic modelling and conclusions оn the mineral deposits. Both types have а broad оссurеnсе in Bulgaria, which allows аn extensive research оn them. Hereafter, discussing the main features of the epithermal mineralization а new hypothesis fоr аn integrated endogene-supergene system is proposed. This idea is based оn published evidences from worldwide as well as Bulgarian examples. Its соrе аrе the detailed mineralogical and petrological characteristics of the epithermal systems. It is suggested, that under some circumstances both endogene and supergene parts of the systems mау bе observed as аn integrity. This integrity is observed as unanimity between the nature and human mind. Among the main prerequisites fоr the origin of such systems аrе spatial compatibility; dependence between endogene and supergene mineralizations; presence of metasomatic rеplacement and indications fоr а metasomatic zonation; соmmоn structural-tectonic agents; geomorphological and climatic agents; etc. The proposed models fоr the epithermal mineralisations аrе based оn Bulgarian occurrences, including some elements from the models of Hedenquist, Lowenstern (1994), Hedenquist (1994), Fournier (1999) and Chavez (2000). These models have аn endogene and а supergene part with а respective metasomatic zonation. The proposed hypothesis is obviously debatable and as аnу оnе hypothesis contains facts and suggestions. However, it is also supported bу evidences from porphyritic systems, where а transition between hypogene and supergene mineralization was already suggested bу Sillitoe (1973). Some debatable points of the proposed hypothesis could bе the cases where а significant gap in time bеtween the primary and supergene mineralizations is established. However, in such cases usually as supergene processes аrе accepted to bе only the recent ones, but those acting simultaneously with the endogene оrе forming so far have bееn neglected. The recent geothermal and hydrothermal volcanic systems аrе the best proof of the simultaneous occurrence of both endogene and supergene processes. The integrity of both processes is already recognized with the admission of the mixed character of the fluids, the convection and the participation of meteoric waters as well as atmospheric oxygen together with magamatic products into the forming of the endogene epithermal deposits.

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Christova, Julia, Todor Todorov, and Kalinka Petrova. "Distribution of the silver in Bulgaria ore deposits." Geologica Balcanica 33, no. 1-2 (June 30, 2003): 3–16. http://dx.doi.org/10.52321/geolbalc.33.1-2.3.

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The content of silver in the different, in terms of genesis and macrochemism, endogenic mineralisations in Bulgaria varies from 1-2 to 200 g/t, most frequently 5-35 g/t. The highest concentrations of this element are registered in the West Balkan region (lead-silver ores near Chiprovtsi, gold-sulphide ores near Govezhda and polymetallic ores Iskar-Vratsa ore region as well as Kremikovtsi deposit); in the Central Rhodopes region (lead-zinc deposits in Laki, Madan and Davidkovo ore fields, Ardino silver-polymetallic deposit); in the lead-zinc ores in Ossogovo ore region; in the East Rhodopes ore region (gold-silver-polymetallic ores in Madzharovo ore field and Popsko, silver-gold ores in Sedefche and Sarnak); in the East Srednogorie (gold-copper-polymetallic ores near Bakadzhik and Zidarovo). Some of the more significant favourable geological prerequisites for the accumulation of silver in the ores are: Late Paleozoic or Tertiary (Oligocene-Miocene) age, geodynamic environments of collision and zones with thick earth crust, anticlinoria and big horst-like uplifts, WNW and NW host structures, close to the surface or flange sections of the mineralisations. The mineralisations with higher content of silver are, as a rule, related to granites. Their host rocks are carbonates with development of metasomatic processes such as dolomitisation and granitoids with periore alterations of the quartz-sericite, quartz-mica (beresite), adular-sericite or quartz-adularia metasomatites and argillizites. The composition of the ores includes lithophile-chalcophile geochemical associations with prevalence of antimony. A favourable factor for the accumulation of silver is the lead-zinc macrochemism with prevalence of lead in zones with thick earth crust and the polymetallic - in zones with basificated (subocean type) earth crust. The mineral composition of the ores includes galena, sulphosalt silver minerals, the especially high silver-bearing tetrahedrite-tennantite series with prevalence of tetrahedrite and participation of magnesium and iron carbonates (siderite, ankerite, dolomite). The character of the silver-bearing mineralisations in Bulgaria is medium to low-temperature and, according to their peculiarities, they can be related to the mesothermal, epithermal or telethermal genetic classes.

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Titisari, Anastasia Dewi, David Phillips, and Hartono Hartono. "GEOCHEMICAL VARIATIONS ON HOSTED VOLCANIC ROCKS OF CIBALIUNG EPITHERMAL GOLD MINERALISATION, BANTEN – INDONESIA: IMPLICATIONS FOR DISTRIBUTION OF SUBDUCTION COMPONENTS." Journal of Applied Geology 6, no. 1 (September 2, 2015). http://dx.doi.org/10.22146/jag.7216.

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Subduction of the Indo-Australian Plate beneath the Eurasian Plate formed at least seven magmatic arcs in Indonesia. One of the magmatic arcs is the Neogene Sunda-Banda arc hosts various style of gold mineralisation such as Cibaliung epithermal gold mineralisation. Major and trace element data for host volcanic rocks to the Cibaliung epithermal gold mineralisation is provided by this study to identify the magmatic arc system and the distribution of subduction components. Enriched LILE (Large Ion Lithopile Element) and LREE (Light Rare Earth Element) compositions for basaltic andesite – rhyodacitic samples from the Cibaliung district are characteristic of calc-alkaline arcs. In this typical volcanic arc, the subduction component can be shown to make a dominant contribution to its content of LILE such as Rb, K, Th, and Ba enriched (more than 88%) relative to the mantle and within plate inputs. The incompatible elements (Hf, Zr, and Nb) cannot be observed in the subduction component and thus assumed to be derived from trace element enriched sub-continental lithosphere. These incompatible elements are defined as conservative elements therefore it suggests that the magma occurrence is related to a hydrous slab component. Keywords: Subduction, Indo-Australian plate, magmatic arcs, volcanic rocks, Cibaliung, epithermal gold.

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Mesquita, Maria José, Márcia Elisa Boscato Gomes, Igor de Camargo Moreira, Renata Augusta Sampaio Paes, Hevelyn Eduarda da Silva Martins, José Henrique Matos, Alberto Ruggiero, et al. "Paleoproterozoic gold deposits at Alta Floresta Mineral Province, Brazil: two overprinted mineralising events?" Geological Society, London, Special Publications, June 28, 2022, SP516–2021–64. http://dx.doi.org/10.1144/sp516-2021-64.

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AbstractLarge gold provinces commonly show complicated mineralization histories, and the Paleoproterozoic Alta Floresta, one of Brazil's most exciting Au-Cu mineral provinces, is a good example. The current models defined four deposit types, all connected to a single (1.88-1.75 Ga) magmatic-hydrothermal event. However, long Province history, diverse geodynamic environment, and older ages of Type-1mineralisation weaken the single metallogenic event and enable the hypothesis of overprinted mineral events. By scale-integrated analyses, we revise the tectonic-geological context, structural-hydrothermal alterations, and chlorite-white mica geothermobarometer and propose the type-1 as an older, granitoid-hosted orogenic mineralisation, with subsequent overprinting by the magmatic-hydrothermal event. The older orogenic gold event developed orogenic gold deposits on WNW-trending shear zones in the Peixoto de Azevedo domain granitic-gneiss rocks. Phengite, biotite, chlorite-carbonate phyllonites (3.3-6.1 kbar, 300º-420ºC) host fault-fill quartz veins (pyrite-chalcopyrite-magnetite-pyrrhotite-gold-Bi-Ag tellurides). Mg-rich chlorite-phengite is the main alteration footprint for this mineralisation type. A younger magmatic-hydrothermal event in the Juruena magmatic-arc rocks produced Fe-rich chlorite-white mica alteration zones (0.6-4.6 kbar, 120º-380ºC) and disseminated and stockwork-breccia ore (pyrite-chalcopyrite-gold-molybdenite- Ti minerals-allanite) in porphyry-epithermal deposits. Where the younger mineralisation overprints the older, phyllic alteration destroyed the phengite orogenic gold phyllonite Sn+1 foliation. The ages of two pyrite populations (1979 and 1841 Ma) in the older fault-fill veins and molybdenite in late fractures (1805-1782 Ma) or disseminated in the ca. 1.79 Ga syenogranite porphyry suggest more than two episodes of mineralisation. These two events differ in their alteration styles, P-T conditions, and structural, mineralogical, and textural ore styles. The multi-scale approach enlightens the relationships between the various mineralisation events, allowing a new explorational potential within the province.Supplementary material at https://doi.org/10.6084/m9.figshare.c.6056324

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Xue, Dong, Xiao-Hua Deng, Leon Bagas, Xu-An Chen, Yan-Shuang Wu, and Xiao Jiang. "Genesis of the Heiyanshan Tungsten Skarn Deposit in the East Tianshan, NW China: Insights From Geology, Fluid Inclusion, Isotopic Geochemistry and Geochronology." Frontiers in Earth Science 9 (September 7, 2021). http://dx.doi.org/10.3389/feart.2021.664603.

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The eastern Tianshan Terrane is a highly prospective zone that contains several porphyry Cu–Mo, VMS Cu–Zn, magmatic Cu–Ni, epithermal and orogenic Au deposits. However, few attention has been paid to tungsten deposits. Of these, the source and evolution of the mineralising fluids related to the skarn W deposits are poorly understood. The Heiyanshan W deposit is hosted by metamorphosed clastic and carbonate beds in the Mesoproterozoic Jianshanzi Formation deposited on a continental margin tectonic setting. The Jianshanzi Formation is intruded by biotite monzogranite that yield weighted 206Pb/238U age of 326.9 ± 1.6 Ma, which suggest that the Heiyanshan W deposit was formed in the Carboniferous. The mineralisation is hosted by a prograde hydrothermal altered zone represented by a garnet (–pyroxene) skarn, and retrograde skarn characterised by fine-grained scheelite. The paragenesis of the Heiyanshan mineralisation can be subdivided into prograde skarn stage, retrograde skarn stage, quartz-sulphide stage and quartz-calcite vein stage. The types of fluid inclusions recognised in the various minerals in the deposits are liquid-rich aqueous, vapour-rich aqueous, and daughter mineral-bearing. The homogenisation temperatures of fluid inclusions from the Heiyanshan deposit decrease from 290 ± 28°C in garnet, through 232 ± 31°C in scheelite, to 232 ± 36°C in quartz and 158 ± 15°C in non-mineralised calcite, which is typical of W-bearing skarn deposits worldwide. The δ18Owater values from the Heiyanshan deposit range from +4.7 to +6.6‰ in garnet, +1.3 to +1.9‰ in quartz and −6.1 to −4.4‰ in calcite. We have measured δD in fluid inclusions from different minerals, although these bulk analyses are just a mixture of the different FIA’s present in the sample. The δD values of fluid inclusions in garnet, quartz, and calcite are from −121 to −71‰, −84 to −75‰ and −101 to −82‰, respectively, also indicative of deep-sourced magmatic fluids mixed with meteoric water. The decrease in the homogenisation temperatures for the fluid inclusions at the Heiyanshan deposit is accompanied by a drop in salinity indicating that tungsten-bearing minerals precipitated during fluid mixing between magmatic fluids and meteoric water. We conclude that eastern Tianshan Terrane contains two pulse of tungsten metallogenic events of Late Carboniferous and Early Triassic.

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Mulja, Thomas, and Mohamad Nur Heriawan. "The Miwah high sulphidation epithermal Au–Ag deposit, Aceh, Indonesia: dynamics of hydrothermal alteration and mineralisation interpreted from principal component analysis of lithogeochemical data." Ore Geology Reviews, June 2022, 104988. http://dx.doi.org/10.1016/j.oregeorev.2022.104988.

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Tolstykh, Nadhezda D., Marek Tuhý, Anna Vymazalová, František Laufek, Jakub Plášil, and Filip Košek. "Gachingite, Au(Te_1–xSe _x ) 0.2 ≈ x ≤ 0.5, a new mineral from Maletoyvayam deposit, Kamchatka peninsula, Russia." Mineralogical Magazine, January 24, 2022, 1–9. http://dx.doi.org/10.1180/mgm.2022.9.

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Abstract Gachingite, Au(Te1–xSe x ), 0.2 ≈ x ≤ 0.5, is a new mineral discovered in the Gaching ore occurrence of the Maletoyvayam epithermal deposit, Kamchatka, Russia. Gachingite forms individual droplet-like grains of sizes from 2 to 10 μm included in native gold (Au–Ag), associated with calaverite, maletoyvayamite, watanabeite and Au–Sb oxides. The aggregates do not exceed 100 μm in diameter. In plane-polarised light, gachingite is grey with a bluish tint, has bireflectance (bluish-grey to deep grey), and strong anisotropy with rotation tints blue to dark blue to brown. Reflectance values for gachingite in air (Rmin, Rmax in %) are: 39.9, 40.3 at 470 nm; 41.6, 43.3 at 546 nm; 42.0, 43.7 at 589 nm; and 43.0, 44.0 at 650 nm. Eighteen electron-microprobe analyses of gachingite gave an average composition: Au 62.40, Ag 0.57, Se 9.78, Te 27.33 and S 0.01, total 100.09 wt.%, corresponding to the formula (Au0.96Ag0.02)Σ0.98(Te0.65Se0.37)Σ1.02 based on 2 apfu, the simplified formula is Au(Te0.65Se0.35); the average analyses of its synthetic analogue is Au 65.7, Se 13.1 and Te 21.1, total 99.9 wt.%, corresponding to Au1.00(Te0.50Se0.50). The calculated density is 10.47 g/cm3. The mineral is orthorhombic, space group Cmce (#64) with a = 7.5379 Å, b = 5.7415 Å, c = 8.8985 Å, V = 385.12 Å3 and Z = 8. The crystal structure was solved and refined from the single-crystal X-ray-diffraction data of synthetic Au1.00(Te0.50Se0.50). The crystal structure of gachingite represents a unique structure type, containing linear [Au–Au–Au] chains running along the b-axis indicating strong metallic interaction in one direction. The structural identity of gachingite and its synthetic analogue Au1.00(Te0.50Se0.50) was confirmed by electron back-scatter diffraction and Raman spectroscopy. The formation of gachingite requires an abundant source of Au and Se and a high oxidising environment. Gachingite is related to the gold-bearing productive stage of ore mineralisation, which is stable at 250°C in log $f_{{\rm S}{\rm e}_ 2}$ range of −12.4 and −5.7. The mineral is named after its type locality.

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Journal articles on the topic 'Epithermal mineralisation'

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