MAJOR IMPURITY ELEMENTS IN NATIVE GOLD AND THEIR ASSOCIATION WITH GOLD MINERALIZATION SETTINGS IN DEPOSITS OF ASIAN FOLD BELTS

2017 ◽  
Keyword(s):  
Native Gold ◽  
Gold Mineralization ◽  
Fold Belts ◽  
Impurity Elements

scholarly journals Native Gold in the Chudnoe Au-Pd-REE Deposit (Subpolar Urals, Russia): Composition, Minerals in Intergrowth and Genesis

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 451
Author(s):  
Galina Palyanova ◽  
Valery Murzin ◽  
Andrey Borovikov ◽  
Nikolay Karmanov ◽  
Sergei Kuznetsov
Keyword(s):  
Native Gold ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Gold Mineralization ◽  
Type I ◽  
Type Ii ◽  
Subpolar Urals ◽  
Type V ◽  
Impurity Elements

Composition of native gold and minerals in intergrowth with rhyolites of the Chudnoe Au-Pd-REE deposit (Subpolar Urals, Russia) was studied using optical microscopy, scanning electron microscopy, and electron microprobe analysis. Five varieties of native gold have been identified, based on the set of impurity elements and their quantities, and on intergrown minerals. Native gold in rhyolites from the Ludnaya ore zone is homogeneous and contains only Ag (fineness 720‰, type I). It is in intergrowth with fuchsite or allanite and mertieite-II. In rhyolites from the Slavnaya ore zone, native gold is heterogeneous, has a higher fineness, different sets and contents of elements: Ag, Cu, 840–860‰ (type II); Ag, Cu, Pd, 830–890‰ (III); Ag, Pd, Cu, Hg, 840–870‰ (IV). It occurs in intergrowth with fuchsite, albite, and mertieite-II (type II), or albite, quartz, and atheneite (III), or quartz, albite, K-feldspar, and mertieite-II (IV). High fineness gold (930–1000‰, type V) with low contents of Ag, Cu, and Pd or their absence occurs in the form as microveins, fringes and microinclusions in native gold II–IV. Tetra-auricupride (AuCu) is presented as isometric inclusions in gold II and platelets in the decay structures in gold III and IV. The preliminary data of a fluid inclusions study showed that gold mineralization at the Chudnoe deposit could have been formed by chloride fluids of low and medium salinity at temperatures from 105 to 230 °C and pressures from 5 to 115 MPa. The formation of native gold I is probably related to fuchsitization and allanitization of rhyolites. The formation of native gold II-V is also associated with the same processes, but it is more complicated and occurred later with a significant role of Na-, Si-, and K-metasomatism. The presence of Pd and Cu in the ores and Cr in fuchsite indicates the important role of mafic-ultramafic magmatism.

scholarly journals NATIVE GOLD OF UKRAINE, PREREQUISITES FOR THE CREATION OF ITS CRYSTALLOGENETIC DETERMINANT

2018 ◽  
pp. 6-18
Author(s):  
V. Kvasnytsya ◽  
I. Kvasnytsya
Keyword(s):  
Native Gold ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Ukrainian Shield ◽  
Low Grade ◽  
Near Surface ◽  
Mineral Associations ◽  
Gold Mineral ◽  
Impurity Elements

The main developments in the typomorphism of native gold from various depth and uneven-aged deposits are described briefly, and the basis for creating a native gold crystallogenetic determinant of Ukraine is proposed. A significant geological material for the most known occurrences of gold mineralization in Ukraine was collected and processed, and a certain stage of studying the crystallomorphology and chemical composition of visible native gold was completed. The crystals of native gold from the occurrences and deposits on the Ukrainian Shield, the Donbass, in the Ukrainian Carpathians and the Transcarpathia have been characterized. The methods of native gold studying, such as goniometry, scanning electron microscopy, and microprobe analysis were used. The typomorphic features of native gold from the main deposits and ore occurrences of Ukraine are determined, which can be used in the practice of predictive, geological prospecting and prospecting for gold. The native gold of the Ukrainian Shield is attributed to deep mineralization, the Ukrainian Carpathians and the Donbass - to medium-deep mineralization and the Transcarpathia – to shallow mineralization. It is shown that in Ukraine, as in other gold-bearing regions of the world, the transition from an ancient deep and medium deep mineralization to a younger near-surface mineralization increases the number of well-formed crystals of native gold and their morphology becomes more complex, individuals of isometric form are replaced by distorted crystals, the role of dendrites and complex twins increases, the grade of gold becomes lower and its heterogeneity grows, the composition and concentration of impurity elements change. The crystallomorphology of the shallow low-grade native gold of the Transcarpathia is diverse (the Muzhi³ve deposit, quartz-barite ores). Unique crystals here are complex twins of cube-octahedrons of native gold. Specificity of medium-deep medium-grade native gold from some ore occurrences of the Donbass is rhombododecahedral faceting of its crystals. Crystallomorphology of deep high-grade native gold from deposits and ore occurrences of the Ukrainian Shield is monotonous. Research data on native gold from known deposits and ore occurrences of Ukraine are generalized and systematization of endogenous gold ore occurrences of Ukraine is made on this basis. A model of a crystallogenetic determinant of native gold of Ukraine is proposed, in which the following main sections are emphasized: 1) native gold mineral associations; 2) chemical-structural and other features of gold crystals; 3) gold crystals morphology; 4) gold crystals anatomy; 5) the method and mechanism of gold crystals growth; 6 ) typomorphic signs of gold crystals; 7) genesis of gold. As an example, a crystallogenetic determinant of native gold from the Proterozoic conglomerates of the Bilokorovychi structure on the Volyn megablock is given. The mineralogical criteria of gold mineralization are outlined and some general conclusions concerning genesis, forecast and searches of gold deposits in Ukraine are made.

The Age of Gold Mineralization in the Yana–Kolyma Metallogenic Belt, Northeastern Russia: First Data of Re–Os Isotope Geochronology of Native Gold

2021 ◽  
Vol 15 (4) ◽  
pp. 293-306
Author(s):  
V. Yu. Fridovsky ◽  
N. A. Goryachev ◽  
R. Sh. Krymsky ◽  
M. V. Kudrin ◽  
B. V. Belyatsky ◽  
...  
Keyword(s):  
Native Gold ◽  
Gold Mineralization ◽  
Northeastern Russia ◽  
Isotope Geochronology ◽  
Metallogenic Belt ◽  
Os Isotope

Gold-bismuth-telluride-sulphide assemblages at the Viceroy Mine, Harare-Bindura-Shamva greenstone belt, Zimbabwe

2008 ◽  
Vol 72 (4) ◽  
pp. 953-970 ◽  
Author(s):  
T. Oberthür ◽  
T. W. Weiser
Keyword(s):  
Native Gold ◽  
Gold Mineralization ◽  
Close Association ◽  
Shear Zones ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Main Stage ◽  
Melting Temperatures ◽  
Native Bismuth ◽  
Gold Bearing

AbstractGold mineralization at the Viceroy Mine is hosted in extensional veins in steep shear zones that transect metabasalts of the Archaean Arcturus Formation. The gold mineralization is generally made up of banded or massive quartz carrying abundant coarse arsenopyrite. However, most striking is a distinct suite of Au-Bi-Te-S minerals, namely joseite-A (Bi4TeS2), joseite-B (Bi4Te2S), hedleyite (Bi7Te3), ikunolite (Bi4S3), ‘protojoseite’ (Bi3TeS), an unnamed mineral (Bi6Te2S), bismuthinite (Bi2S3), native Bi, native gold, maldonite (Au2Bi), and jonassonite (AuBi5S4). The majority of the Bi-Te-S phases is characterized by Bi/(Se+Te) ratios of >1. Accordingly, this assemblage formed at reduced conditions at relatively low fS2 and fTe2. Fluid-inclusion thermometry indicates depositional temperatures of the main stage of mineralization of up to 342°C, in the normal range of mesothermal, orogenic gold deposits worldwide. However, melting temperatures of Au-Bi-Te phases down to at least 235°C (assemblage (Au2Bi + Bi + Bi7Te3)) imply that the Au-Bi-Te phases have been present as liquids or melt droplets. Furthermore, the close association of native gold, native bismuth and other Bi-Te-S phases suggests that gold was scavenged from the hydrothermal fluids by Bi-Te-S liquids or melts. It is concluded that a liquid/melt-collecting mechanism was probably active at Viceroy Mine, where the distinct Au-Bi-Te-S assemblage either formed late as part of the main, arsenopyrite-dominated mineralization, or it represents a different mineralization event, related to rejuvenation of the shear system. In either case, some of the gold may have been extracted from pre-existing, gold-bearing arsenopyrite by Bi-Te-S melts, thus leading to an upgrade of the gold ores at Viceroy. The Au-Bi-Te-S assemblage represents an epithermal-style mineralization overprinted on an otherwise mesothermal (orogenic) gold mineralization.

scholarly journals Typomorphic Features of Placer Gold from the Billyakh Tectonic Melange Zone of the Anabar Shield and Its Potential Ore Sources (Northeastern Siberian Platform)

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 281
Author(s):  
Boris Gerasimov ◽  
Vasily Beryozkin ◽  
Alexander Kravchenko
Keyword(s):  
Native Gold ◽  
Gold Mineralization ◽  
Coarse Fraction ◽  
Gold Deposits ◽  
Primary Sources ◽  
The Arctic ◽  
Geochemical Data ◽  
Placer Gold ◽  
Anabar Shield ◽  
Tectonic Mélange

Precambrian shields and outcropped Precambrian rock complexes in the Arctic may serve as the most important sources of various types of mineral raw materials, including gold. The gold potential of the Anabar shield in the territory of Siberia has, thus far, been poorly studied. A number of primary and placer gold occurrences have been discovered there, but criteria for the prediction of and search for gold mineralization remain unclear. The main purpose of this paper was to study the typomorphic features of placer gold in the central part of the Billyakh tectonic mélange zone in the Anabar shield and to compare them to mineralization from primary sources. To achieve this, we utilized common methods for mineralogical, petrographic, and mineragraphic analyses. Additionally, geochemical data were used. As a result of this investigation, important prospecting guides were identified, and essential criteria for the prediction of and search for gold deposits were elucidated. The characteristics of the studied placer gold were specific for gold derived from a proximal provenance. These characteristics included the poor roundness of the native gold grains, a cloddy–angular and dendritic form, an uneven surface, and a high content of coarse-fraction native gold (0.5–2 mm), which was as high as 24% of the volume of analyzed native gold. In addition, we conducted a study on the mineralogical features of the gold-sulfide mineralization that was disseminated throughout a small exposure area of paleo-Proterozoic para- and orthogneisses in the Anabar shield basement. A comparison of mineral inclusions in the coarse-fraction native gold and mineral assemblages in the ore deposits showed that one of the possible primary sources for placer gold might be small bodies of metasomatically altered orthogneisses associated with large granitoid plutons.

Metallogeny of the Marco zone, Corvet Est, disseminated gold deposit, James Bay, Quebec, Canada

2012 ◽  
Vol 49 (10) ◽  
pp. 1154-1176
Author(s):  
Martin Aucoin ◽  
Georges Beaudoin ◽  
Robert A. Creaser ◽  
Paul Archer
Keyword(s):  
Gold Deposit ◽  
Basaltic Andesite ◽  
Native Gold ◽  
Gold Mineralization ◽  
Isotope Composition ◽  
Hanging Wall ◽  
Volcanic Rocks ◽  
Weighted Average ◽  
James Bay ◽  
Host Rocks

The Corvet Est gold deposit is hosted by Archean rocks of the Superior Province in the James Bay region, northern Quebec, Canada. The Marco zone is hosted by amphibolite-grade, strongly foliated volcanic rocks and consists of disseminated gold, with an apparent thickness ranging from 1.8 to 39.5 m and gold grades up to 23 g·t–1 over 1 m, that is continuous along strike for ∼1.3 km. The lithotectonic sequence comprises footwall basaltic andesite amphibolite overlain by a lenticular unit of metadacite and then by hanging-wall basaltic andesite amphibolite, all intruded by quartz–feldspar porphyry dikes. Dacite, basaltic andesite amphibolite, and quartz–feldspar porphyry show a calc-alkaline to transitional affinity and plot in the plate margin arc basalt field, with typical volcanic arc trace element patterns. Mineralization consists of pyrite, arsenopyrite, pyrrhotite, chalcopyrite, and gold, disseminated in deformed dacite, in andesite amphibolite, and in quartz–feldspar porphyry dikes. Dacite and andesite display weak alteration characterized by silicification. Native gold forms inclusions in metamorphic quartz, garnet, feldspar, arsenopyrite, and pyrite or free grains interstitial to quartz, feldspar, pyrite, chalcopyrite, and arsenopyrite. Free gold in late quartz veins cut the sericitized metamorphic fabric. Inclusion and interstitial native gold within minerals annealed during metamorphism shows that gold mineralization is pre- to syn-metamorphic, with some gold remobilized in later veins. Rhenium–osmium dating of arsenopyrite yields an isochron age of 2663 ± 13 Ma for mineralization and a weighted average model age of 2632 ± 7 Ma for arsenopyrite formed during peak metamorphism. The ∼2663 Ma arsenopyrite has a low initial 187Os/188Os of 0.19 ± 0.10, suggesting a juvenile crust or a mantle Os source. The sulfur isotope composition of Marco zone pyrite and arsenopyrite shows that sulfur could have been leached from its volcanic host rocks or from reduction of Archean seawater. The Corvet Est deposit is interpreted to be an orogenic gold deposit (2663 Ma) deformed and recrystallized during amphibolite-grade metamorphism (2632 Ma).

scholarly journals Process and Mechanism of Gold Mineralization at the Zhengchong Gold Deposit, Jiangnan Orogenic Belt: Evidence from the Arsenopyrite and Chlorite Mineral Thermometers

Minerals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 133 ◽  
Author(s):  
Si-Chen Sun ◽  
Liang Zhang ◽  
Rong-Hua Li ◽  
Ting Wen ◽  
Hao Xu ◽  
...  
Keyword(s):  
Phase Separation ◽  
Gold Deposit ◽  
Native Gold ◽  
Gold Mineralization ◽  
Early Stage ◽  
Orogenic Belt ◽  
Alteration Zone ◽  
Composition Analysis ◽  
Invisible Gold ◽  
Polymetallic Sulfides

The Zhengchong gold deposit, with a proven gold reserve of 19 t, is located in the central part of Jiangnan Orogenic Belt (JOB), South China. The orebodies are dominated by NNE- and NW- trending auriferous pyrite-arsenopyrite-quartz veins and disseminated pyrite-arsenopyrite-sericite-quartz alteration zone, structurally hosted in the Neoproterozoic epimetamorphic terranes. Three stages of hydrothermal alteration and mineralization have been defined at the Zhengchong deposit: (i) Quartz–auriferous arsenopyrite and pyrite; (ii) Quartz–polymetallic sulfides–native gold–minor chlorite; (iii) Barren quartz–calcite vein. Both invisible and native gold occurred at the deposit. Disseminated arsenopyrite and pyrite with invisible gold in them formed at an early stage in the alteration zones have generally undergone syn-mineralization plastic-brittle deformation. This resulted in the generation of hydrothermal quartz, chlorite and sulfides in pressure shadows around the arsenopyrite and the formation of fractures of the arsenopyrite. Meanwhile, the infiltration of the ore-forming fluid carrying Sb, Cu, Zn, As and Au resulted in the precipitation of polymetallic sulfides and free gold. The X-ray elements mapping of arsenopyrite and spot composition analysis of arsenopyrite and chlorite were carried out to constrain the ore-forming physicochemical conditions. The results show that the early arsenopyrite and invisible gold formed at 322–397 °C with lgf(S2) ranging from −10.5 to −6.7. The crack-seal structure of the ores indicates cyclic pressure fluctuations controlled by fault-valve behavior. The dramatic drop of pressure resulted in the phase separation of ore-forming fluids. During the phase separation, the escape of H2S gas caused the decomposition of the gold-hydrosulfide complex, which further resulted in the deposition of the native gold. With the weakening of the gold mineralization, the chlorite formed at 258–274 °C with lgf(O2) of −50.9 to −40.1, as constrained by the results from mineral thermometer.

scholarly journals PROSPECTS OF THE DNIESTER RIVER FLOODPLAIN TERRACES STRATA FOR GOLD MINERALIZATION

2020 ◽  
pp. 71-77
Author(s):  
K. Derevska ◽  
O. Aleksandrov ◽  
V. Berehovenko ◽  
M. Kovalchuk ◽  
K. Rudenko ◽  
...  
Keyword(s):  
River Basin ◽  
Native Gold ◽  
Gold Mineralization ◽  
Flood Plain ◽  
Gold Deposits ◽  
Raw Material ◽  
Paleolithic Site ◽  
Late Paleolithic ◽  
Leading Role ◽  
Gold Bearing

The article clarifies the stratigraphic binding and origin of silicon nodules, which served as the main raw material for the manufacture of tools for mammoth hunters of the Mezhyrich Late Paleolithic site. In archaeological publications, these nodules are often mentioned to be confined to the "Vyrzhikovsky layer" (the Albian layer of the Lower Cretaceous), which was formed under continental conditions and consists of sand-clay (kaolin, in particular) deposits. The analysis of the necessary conditions and possible mechanisms for the formation of silicon nodules indicates the erroneousness of such ideas. Most likely, the source of silicon raw materials was the marine deposits of the Cenomanian (Upper Cretaceous), or, in accordance with the modern stratigraphic division of the Mesozoic-Cenozoic sequence, deposits of the Burim suite (upper Albian – lower Cenomanian). The paleogeographic setting, sedimentological conditions and lithological composition of the "Vyrzhikovsky layer" did not ensure the formation of silicon nodules in it in the form of inclusions. The latter are diagenetic in origin and could only form in the thickness of carbonate rocks, free of clay minerals. The region of Kaniv dislocations was the optimal region from the silicon production point of view, which was determined: firstly, by the tectonic dislocation of the sedimentary sequence, which contributed to the removal of deposits containing silicon nodules in the thickness of younger rocks; secondly,the erosion activity of temporary streams, which brought these deposits to the level of the denudation cut-off. The most convenient place for collecting flints was not the outcrop of bedrock in ravines but the cones of their removal, which overlook the floodplains of the Dnipro and Ros'. The possibility of collecting flint in the immediate vicinity of the Mezhirich site, in the ravines and gullies between the Ros and Rosava rivers, does not find confirmation, since the chalk deposits here lie much lower than the local erosion base and are not exposed by ravines. Therefore, the leading role in the formation of the raw material supply of the Late Paleolithic site of Mezhirich was played by the region adjacent to the Kaniv mountains of the alluvial-proluvial plain.Despite long-term geological study of the Dniester River basin, we still have no clear evidences about gold-bearing potentiality of this area as well as origin of gold. The leading role of geological, geochemical and mineralogical criteria is proved for defining the prospects of substantial gold deposits finding within the Dniester river basin. Gold was found here in the crystalline basement and in the sedimentary cover rocks. Study of mineralogy and lithology of the terraces above the flood-plain and typomorphic peculiarities of native gold shows that palaeogeographic conditions and alimentation zones of debris vary at the different tectonic stages of this area development. Gold-bearing potential of the Pliocene-Quaternary sediments in the Dniester River basin is related to the Pliocene (VI-IX terraces above the flood-plain) and Quaternary (I-V terraces above the flood-plain) terraces complex of the Dniester river, as well as this river and its inflows recent alluvia. Our study of the Mid-flow part of the Dniester river basin allow to conclude that native gold was found in geologocal strata of all ages, from Proterozoic up to the recent alluvium. This fact points the necessity of further prospecting to find the mother lodes of gold. Our field study, samples analyses made as well as publications observation allow highlighting the principal directions of further prospecting and evaluation works. The main among that are: 1) comprehensive study of river Dniester alluvia and its terraces complex (previously VI–VII terraces), that will allow to specify their material composition, to assess real gold-bearing potential and to define the history of denudation areas changes; 2) lithogeochemical prospecting of primary and secondary dispersion haloes to clear the principal gold-bearing regularities; 3) definition of prospect plots within the area described; 4) modern analytical approach study of typomorphic peculiarities of native gold from alluvia and terrace deposits to define its ore formational affinity and mineral type.

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