A Low‐Sulfidation Epithermal Mineralization in the River Reef Zone, the Poboya Prospect, Central Sulawesi, Indonesia: Vein Textures, Ore Mineralogy, and Fluid Inclusions

Significant selenium enrichment associated with selenides and previously unknown Ag-Pb-Sb, Ag-Sb and Pb-Sb sulfosalts has been discovered in hydrothermal ore veins in the Anthony of Padua mine near Poličany, Kutná Hora ore district, central Bohemia, Czech Republic. The ore mineralogy and crystal chemistry of more than twenty silver minerals are studied here. Selenium mineralization is evidenced by a) the occurrence of selenium minerals, and b) significantly increased selenium contents in sulfosalts. Identified selenium minerals include aguilarite and selenides naumannite and clausthalite. The previously unknown sulfosalts from Kutná Hora are identified: Ag-excess fizélyite, fizélyite, andorite IV, andorite VI, unnamed Ag-poor Ag-Pb-Sb sulfosalts, semseyite, stephanite, polybasite, unnamed Ag-Cu-S mineral phases and uytenbogaardtite. Among the newly identified sulfides is argyrodite; germanium is a new chemical element in geochemistry of Kutná Hora. Three types of ore were recognized in the vein assemblage: the Pb-rich black ore (i) in quartz; the Ag-rich red ore (ii) in kutnohorite-quartz gangue; and the Ag-rich ore (iii) in milky quartz without sulfides. The general succession scheme runs for the Pb-rich black ore (i) as follows: galena – boulangerite (– jamesonite) – owyheeite – fizélyite – Ag-exces fizélyite – andorite IV – andorite VI – freieslebenite – diaphorite – miargyrite – freibergite. For the Ag-rich red ore (ii) and ore (iii) the most prominent pattern is: galena – diaphorite – freibergite – miargyrite – pyragyrite – stephanite – polybasite – acanthite. The parallel succession scheme progresses from Se-poor to Se-rich phases, i.e., galena – members of galena – clausthalite solid solution – clausthalite; miargyrite – Se-rich miargyrite; acanthite – aguilarite – naumannite. A likely source of selenium is in the serpentinized ultrabasic bodies, known in the area of “silver” lodes in the South of the ore district, which may enable to pre-concentrate selenium, released into hydrothermal fluids during tectonic events. The origin of the studied ore mineralization is primarily bound to the youngest stage of mineralization of the whole ore district, corresponding to the Ag-Sb sequence of the ´eb´ ore type of the Freiberg ore district in Saxony (Germany) and shows mineralogical and geochemical similarities to low-sulfidation epithermal-style Ag-Au mineralization.

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The conditions of formation of Au–Ag epithermal mineralization of the Amguemo-Kanchalan volcanic field (Eastern Chukotka)

Вулканология и сейсмология ◽

10.31857/s0203-03062019568-80 ◽

2019 ◽

pp. 68-80

Author(s):

A. V. Volkov ◽

V. Yu. Prokofiev ◽

A. A. Sidorov ◽

S. F. Vinokurov ◽

A. A. Elmanov ◽

...

Keyword(s):

Practical Importance ◽

Fluid Pressure ◽

Volcanic Belt ◽

Volcanic Field ◽

Hydrothermal Fluids ◽

Medium Temperature ◽

Epithermal Mineralization ◽

Low Salt ◽

Low Sulfidation ◽

Regional Forecast

The article considers the conditions of formation of Au–Ag epithermal mineralization of the Amguemo-Kanchalan volcanic field (AKVP), located on the Western closure of the East Chukchi flank zone of the Okhotsk-Chukchi volcanic belt (OCHVB). In the AKVP potentially large Au–Ag Valunisty mine and several perspective deposits and ore occurrences (Zhilnoye, Shah, Gornoye, Ognennoye and Osennee) are localized. The results of thermo- and cryometric studies of fluid inclusions in quartz and calcite of epithermal veins showed that the solutions was dominated by chlorides Na and K. Epithermal mineralization was deposited by heterogeneous hydrothermal fluids with low salt concentrations (0.2–3.6 wt. % equiv. NaCl, in medium-temperature conditions – 174–354°C). The fluid pressure reached 30–160 bar, which corresponds to the formation depth of 0.1–0.6 km, under hydrostatic conditions. The obtained results allow us to attribute the studied epithermal mineralization to the low sulfidation class. The magmatic hearth of andesitic magmas and meteoric waters are the most probable sources of ore-forming fluids. The information given in the article is of practical importance for regional forecast-metallogenic constructions, prospecting and evaluation of epithermal Au–Ag deposits.

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THE CASPOSO GOLD-SILVER DEPOSIT: EVIDENCE FOR PERMO-TRIASSIC LOW-SULFIDATION EPITHERMAL MINERALIZATION IN THE CORDILLERA FRONTAL, SAN JUAN PROVINCE, ARGENTINA

Economic Geology ◽

10.5382/econgeo.4755 ◽

2020 ◽

Author(s):

S. Grignola ◽

S. Hagemann ◽

A.S. Fogliata ◽

J. Miller ◽

F. Jourdan ◽

...

Keyword(s):

Lower Triassic ◽

The Andes ◽

Vein Formation ◽

Epithermal Mineralization ◽

Lithostratigraphic Units ◽

Gold Silver ◽

Felsic Dikes ◽

Host Rocks ◽

Low Sulfidation ◽

Silver Mineralization

Abstract New geochronological data provide evidence for Permo-Triassic low-sulfidation epithermal gold-silver mineralization in the Cordillera Frontal, Argentina. The U-Pb sensitive high-resolution ion microprobe (SHRIMP) analyses on zircons and titanite gave the following results: (1) andesite and rhyolite volcanic host rocks of the Casposo Au-Ag deposit yielded a range of ages between 267.1 ± 0.7 and 241.7 ± 2.2 Ma; (2) two composite plutons located near Casposo yielded ages of 268.2 ± 1.5 and 265.1 ± 1.5 Ma for the Colorado syenogranite-granite pluton and 266.6 ± 1.4 and 254.0 ± 2.4 Ma for the Casposo granodiorite-tonalite pluton; (3) a trachyan-desite dike emplaced at 265.7 ± 1.2 Ma that is crosscut by mineralized quartz-adularia-calcite-gold veins in the Kamila East area; (4) felsite intrusions, interpreted to be temporally related to the emplacement of mineralized veins at 261.1 ± 3.5 Ma; and (5) composite rhyolite/andesite dikes that crosscut all other lithostratigraphic units and mineralized veins at 238.4 ± 1.6 Ma. The 40Ar/39Ar dates on hydrothermal adularia within quartz-adularia-calcite-gold veins of the Casposo deposit revealed at least three, likely discreet, hydrothermal fluid pulses and associated periods of vein formation during extensional events between 280–274, 262–258, and 250–246 Ma. Relative and absolute timing of volcanic host rocks, plutons, postmineralization felsic dikes, and gold-bearing veins of the Casposo epithermal vein system suggest the presence of significant Permian (Cisuralian)-Lower Triassic low-sulfidation epithermal-style gold-silver mineralization at the eastern flank of the Cordillera Principal in Argentina. The existence of this epithermal Au-Ag system opens the potential for a significant magmatic-hydrothermal system in a part of the Andes that previously was considered to be of low prospectivity.

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Fluid processes in the Tesbihdere base-metal-Au deposit: Implications for epithermal mineralization in the Biga Peninsula, NW Turkey

Open Geosciences ◽

10.2478/s13533-012-0169-9 ◽

2014 ◽

Vol 6 (2) ◽

Cited By ~ 2

Author(s):

Gulcan Bozkaya ◽

David Banks ◽

Fatih Ozbas ◽

Jon Wallington

Keyword(s):

Fluid Inclusions ◽

Meteoric Water ◽

Large Range ◽

Magmatic Fluid ◽

Biga Peninsula ◽

Epithermal Mineralization ◽

Wide Range ◽

Nw Turkey ◽

Fracture Opening ◽

Enclosing Rocks

AbstractTesbihdere is one of a number of spatially close epithermal Cu-Pb-Zn-Ag-Au deposits hosted by andesites and rhyolites, typical of deposits in the Biga peninsula. Microthermometry of fluid inclusions shows a wide range of temperatures, ∼360–170°C, and salinities, ∼10-0.5 wt.% NaCl, in the different deposits studied. Dilution of a moderately saline magmatic? fluid with meteoric water occurred at constant temperature indicating, the temperature of both fluids was controlled by the geological environment. Boiling was not a major factor, but did occur in very minor amounts. The large range of temperatures within individual samples can only reasonably be explained by variations from near lithostatic to hydrostatic pressure during vein and fracture opening. That this pressure decrease did not produce extensive boiling suggests that vein opening was gradual rather than aggressive, allowing the pressure and temperature decrease to follow a path close to the L-V boiling curve. P-T reconstruction places emplacement of these ore veins at between 300–500 m beneath the surface. Similarities of LA-ICPMS of fluid inclusions from Tesbihdere, Azitepe and Basmakci, supports the conclusion that they were part of the same contemporaneous mineralizing system. The fluids are dominated by Na, with the concentrations of K>Ca>Mg combined equivalent to the concentration of Na. The range of K/Na ratios is not consistent with the fluid inclusion temperatures as the calculated temperatures are significantly higher indicating the fluids were not close to equilibrium with the enclosing rocks. Elevated K concentrations are consistent with acid-sulphate waters in shallow epithermal systems. Ore metals Cu, Zn and Pb are present in significant concentrations ∼500, 300 and 200 ppm respectively and the low Fe/Mn ratios are indicative of a relatively oxidising fluid. The negative δ 34S values of sulphides are consistent with boiling and oxidising redox conditions.

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The Ag- and Au-bearing phases in the Escondida epithermal vein, Cerro Moro deposit, Santa Cruz, Argentina

The Canadian Mineralogist ◽

10.3749/canmin.1900075 ◽

2020 ◽

Vol 58 (2) ◽

pp. 191-201 ◽

Cited By ~ 1

Author(s):

Ana C. Mugas Lobos ◽

María Florencia Márquez-Zavalía ◽

Laura B. Hernández

Keyword(s):

Partial Substitution ◽

Critical Element ◽

Santa Cruz ◽

Epithermal Deposits ◽

Fine Grained ◽

Quartz Veins ◽

Epithermal Mineralization ◽

Ore Minerals ◽

The Usa ◽

Low Sulfidation

ABSTRACT The Cerro Moro deposit is located at 48°5′55″S, 66°39′1.6″W and 100 m.o.s.l. in Santa Cruz province, southern Argentina. It is a low sulfidation Au-Ag epithermal mineralization hosted by numerous NW–SE structurally controlled quartz veins developed in close spatial and temporal proximity to the products of Jurassic extension and magmatism. The Escondida vein is the most significant mineralized structure, as it hosts the base metal-rich and Au-Ag high grade mineralization. In this vein and the Zoe ore-shoot, ore minerals are abundant (sphalerite, galena, chalcopyrite, acanthite, and less abundant pyrite and marcasite) and frequently related to dark grey, fine-grained quartz with massive, porous, crustiform, and banded textures; variable quantities of fine-grained flakes of muscovite are locally present. The Ag- and Au-bearing mineral association is represented by acanthite, argyrodite, polybasite, pearceite, stromeyerite, mckinstryite, and jalpaite. Abundant acanthite occurs commonly associated with gold and silver; copper enrichments were detected and interpreted as nanoinclusions of Cu-bearing minerals. The occurrence of Se- and Te-enriched minerals (acanthite, argyrodite, polybasite, pearceite, stromeyerite, and mckinstryite), rather than silver selenides and/or tellurides, indicates the presence of reduced mineralizing fluids and may be ascribed to partial substitution of S by Se or Te. Polybasite and pearceite were differentiated by their chemistry. Although the presence of argyrodite in epithermal deposits with silver sulfosalts is relatively common, this first mention in Cerro Moro is highly encouraging for exploration for germanium, a critical element, which is also considered strategic by countries such as the USA and China.

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Petrography, microthermometry, and isotopy of the gold veins from Vetas, Santander (Colombia)

Earth Sciences Research Journal ◽

10.15446/esrj.v24n1.63443 ◽

2020 ◽

Vol 24 (1) ◽

pp. 5-18

Author(s):

Sonia Rojas Barbosa ◽

Juan Carlos Molano ◽

Thomas Cramer

Keyword(s):

Fluid Inclusions ◽

Gold Mineralization ◽

Coarse Grained ◽

Fine Grained ◽

Quartz Veins ◽

Low Salinity ◽

Second Stage ◽

The Third ◽

Jurassic Rocks ◽

Low Sulfidation

The gold mineralization located in Vetas, Santander, consists of auriferous quartz veins hosted in Bucaramanga gneiss rocks, intrusive Jurassic rocks, and intrusive to porphyritic Miocene rocks. This study identified four mineralizing events: (1). Sericite, carbonate (ankerite and calcite?), massive and microcrystalline quartz, sphalerite, adularia, albite, galena, thin pyrite, pyrrhotite, chalcopyrite. The age for this stage is 10.78 ±0.23Ma (Ar/Ar on sericite). (2). Molybdenite, magnetite with exsolution of ilmenite, As-pyrite, sphalerite, fine-grained pyrite and little chalcopyrite quartz with huge, feathery, fine mosaic, flamboyant and microcrystalline textures and, tourmaline and sericite. (3). Gold and tennantite associated with sphalerite, fine- and coarse-grained pyrite, As-pyrite, chalcopyrite like inclusions, and quartz with flamboyant, mosaic, massive and “comb” textures, and tourmaline. Stage 2 and 3 happened from 7.58 ±0.15 Ma to 6,89±0,41Ma (Ar/Ar on sericite). (4). Thick, thin, and pyrite with arsenic, hematite and microcrystalline quartz (forming breccia texture), and sericite. The age for this stage is 5.24 ±0.10 (Ar/Ar on sericite). Post-mineral: quartz comb, alunite, halloysite, kaolinite, and ferrum hydroxides. The stable isotopes, ∂18O, ∂D, and ∂34S and fluid inclusions analysis infer that fluids were producing a mixture of meteoric and magmatic fluids with low salinity and minimum trapping temperatures between 200°C to 390°C. The mineralogy association, and fluid inclusions, in the first event show characteristic of low sulfidation epithermal. The second stage was hottest and with more magmatic signature over printed an intermediate sulfidation system; show a little more salinity on the fluids and more mineralogical diversity, the third and four events, could show an evolution of this fluid, where it was cooling and impoverishing on metals. Two initials stages are contemporaneous with two magmatic Miocene pulses on the area: the first one of granodiorite composition 10, 9± 0.2 Ma (U/Pb zircon), and the other one rhyodacite with 8.4 ±0.2 y 9.0 ± 0.2 Ma.

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Fluid Inclusion Study of The Tumpangpitu High Sulfidation Epithermal Gold Deposit in Banyuwangi District, East Java, Indonesia

Journal of Geoscience Engineering Environment and Technology ◽

10.24273/jgeet.2018.3.01.1039 ◽

2018 ◽

Vol 3 (1) ◽

pp. 8

Author(s):

Yu Yu Myaing ◽

Arifudin Idrus ◽

Anastasia Dewi Titisari

Keyword(s):

Fluid Inclusion ◽

Fluid Inclusions ◽

Homogenization Temperature ◽

Fluid Inclusion Study ◽

Epithermal Gold ◽

High Sulfidation ◽

Epithermal Mineralization ◽

Epithermal Gold Deposit ◽

Inclusion Study ◽

Low K

The Tumpangpitu high sulfidation (HS) epithermal gold deposit is located in the south coast of East Java, Banyuwangi District, East Java Province, Indonesia. This area lies within the central portion of the Cenozoic Sunda‐Banda magmatic arc which trends southeast from northern Sumatra to west Java then eastward through east Java, Bali, Lombok, Sumbawa and terminating at Banda sea. The geology of the Tumpangpitu is predominantly occupied by Late Oligocene to Middle Miocene low-K calc-alkaline to alkaline andesitic volcanic rocks and interbedded with volcaniclastic rock sequences, which are associated with low-K intermediate intrusions. The mineralization style at the Tumpangpitu area is composed of a high‐sulfidation (HS) epithermal gold-copper system which is typically associated with concealed gold-rich porphyry copper system. The HS epithermal mineralization is hosted by volcanic and volcaniclastic rocks in this research area. The mineralization domains are divided into Zone A, Zone B and Zone C which are situated along NW-SE-trending silica ledges zones. The HS epithermal mineralization is texturally occurs as vuggy replacements mineralization as well as stockworks, disseminated forms, fractures and veins. Fluid inclusion study was conducted for 6 quartz vein samples which petrographically entrapped fluid inclusions. Homogenization temperature (Th) and melting temperature (Tm) can microthermometrically be determined by fluid inclusion analysis. The average homogenization temperature (Th) of the fluid inclusions gives 180˚C to 342˚C and melting temperature are from -0.1 ˚C to -1.4˚C. Tm corresponds to the salinities ranging from 0.1 to 4.5 wt% NaCl equivalent. The paleodepth of ore formation can be estimated from the salinity of fluid. Since the deposit was not formed at boiling condition, the minimum paleodepth of ore (quartz) samples taken from both shallow level (53.35 m) and deep level (135.15 m) is determined at 650m and 1,220 m, respectively. The microthermometric data point out that the Tumpangpitu deposit formed at moderate temperature and low salinity by magmatic fluid mixing and dilution by meteoric water during the hydrothermal fluid evolution. On the basis of the fluid inclusion microthermometric data and its other key characteristics, the Tumpangpitu gold mineralization shares some similarities compared to other typical HS-epithermal gold deposits worlwide although it also shares few differences.

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