Supergene remobilization of Au in Au-bearing regolith related to orogenic deposits: A case study from Kazakhstan

Kalinin, Yuri A.; Palyanova, Galina; Naumov, E.A.; Kovalev, K.R.; Pirajno, Franco

doi:10.1016/j.oregeorev.2019.04.019

Cited by 17 publications

(13 citation statements)

References 31 publications

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“…Evidentially, mustard gold is characteristic of gold-telluride [12][13][14][15] and gold-antimony [16][17][18] deposits, weathering crust [19][20][21] and placers [22,23]. Recently, mustard gold, sometimes with an admixture of Tl (up to 6.34 wt%), was found in the Oleninsky Au-Ag deposit (Kola Peninsula, Russia) [24].…”

Section: Discussionmentioning

confidence: 99%

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Characteristics of Supergene Gold of Karst Cavities of the Khokhoy Gold Ore Field (Aldan Shield, East Russia)

Anisimova¹,

Kondratieva²,

Kardashevskaia³

2020

Minerals

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Typomorphic features of supergene gold in karst cavities were studied in the recently discovered Au–Te–Sb–Tl deposit within the Khokhoy gold ore field of the Aldan-Stanovoy auriferous province (Aldan shield, East Russia). Two morphological types of supergene gold, massive and porous, are recognized there. The first type is represented by gold crystals and irregular mass, with the fineness ranging from 835 to 1000‰. They are closely associated with goethite, siderite, unnamed Fe, Te, and Tl carbonates, Tl tellurites/tellurates and antimonates, as well as avicennite with a Te impurity. The second type is represented by mustard gold of two types with different internal structure: microporous and dendritic. The supergene gold is characterized by persistently high fineness. Along with Ag, it invariably contains Hg (up to 5.78 wt%) and Bi, and, rarely, Pb, Cu, and Fe. The supergene gold is chemically homogeneous, and its particles are all marked by high fineness, without any rims or margins. The obtained characteristics made it possible to prove the existence of two genetic types of supergene gold. Mustard microporous gold is the result of the decomposition of the associated minerals—goethite, Tl oxides, tellurium, Fe, Mn and Tl carbonates and antimonates, containing microinclusions of gold. Massive gold and dendrites are newly formed. The decomposition, remobilization, and reprecipitation of residual gold nanoparticles and their aggregation led to the formation of dendrites, and with further crystal growth and filling of pores, to gold of massive morphology. In terms of morphology, internal structure, fineness, and trace element composition, supergene gold of the Khokhoy gold ore field is comparable to gold from the Kuranakh deposit (Russia) and the Carlin-type gold deposits. It also is similar to spungy and mustard gold from Au–Te and Au–Sb deposits, weathering crusts, and placers. Its main characteristic feature is a close paragenesis with Tl minerals.

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Section: Discussionmentioning

confidence: 99%

“…In the interstices between massive gold there are found dendritic gold particles closely interwoven with goethite ( Figure 5c, Table 3, Nos. [16][17][18][19][20][21][22][23]. The most intricate forms of gold are seen in a very rare mineral avicennite (Tl 2 O 3 ), an oxide of thallium with a Te impurity ( Figure 5d, Table 3; Nos.…”

Section: Massive Goldmentioning

confidence: 99%

Characteristics of Supergene Gold of Karst Cavities of the Khokhoy Gold Ore Field (Aldan Shield, East Russia)

Anisimova¹,

Kondratieva²,

Kardashevskaia³

2020

Minerals

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“…Association of secondary gold and Fe hydroxides was the final oxidation product of the studied parageneses. Secondary high fineness gold in association with supergene minerals, including goethite, has been described in Au-bearing regolith in deposits in Kazakhstan [22], where the secondary gold is not the mustard species, but has a crystal shape and different genesis. Table 5.…”

Section: Types Of Mustard Goldmentioning

confidence: 99%

Mustard Gold of the Gaching Ore Deposit (Maletoyvayam Ore Field, Kamchatka, Russia)

Tolstykh

Palyanova

Bobrova³

et al. 2019

Minerals

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The Gaching high-sulfidation (HS) epithermal Au–Ag deposits, part of the Maletoyvayam ore field, which is located in the volcanic belts of the Kamchatka Peninsula (Russia). The main ore components are native gold, tellurides, selenides, and sulphoselenotellurides of Au and oxidation products of Au-tellurides. This study examines the different types of native gold in this ore deposit and the mechanisms and sequential transformation of calaverite (AuTe2) into mustard gold. The primary high fineness gold (964‰–978‰) intergrown with maletoyvayamite Au3Te6Se4 and other unnamed phases (AuSe, Au(Te,Se)) differ from the secondary (mustard) gold in terms of fineness (1000‰) and texture. Primary gold is homogeneous, whereas mustard is spongy. Two types of mustard gold were identified: a) Mixtures of Fe-Sb(Te,Se,S) oxides and fine gold particles, which formed during the hypogenic transformation stage of calaverite due to the impact of hydrothermal fluids, and b) spotted and colloform gold consisting of aggregates of gold particles in a goethite/hydrogoethite matrix. This formed during the hypergenic transformation stage. Selenides and sulphoselenotellurides of gold did not undergo oxidation. Pseudomorphic replacement of calaverite by Au-Sb(Te,Se,S,As) oxides was also observed.

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“…Nevertheless, crushed samples frequently contain grains of native gold with a size of 0.05-0.1 mm, less often 0.2-0.35 mm. The mechanisms of enlargement of native gold particles in natural migration processes (dissolution, transfer, and deposition) of noble metal are interpreted in many works [17][18][19][20][21].…”

Section: Stages Of Metamorphism Andmentioning

confidence: 99%

Formation of Au-Bearing Antigorite Serpentinites and Magnetite Ores at the Massif of Ophiolite Ultramafic Rocks: Thermodynamic Modeling

et al. 2019

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We constructed thermodynamic models of the formation of two types of gold-ore mineralization at the Kagan ultramafic massif in the Southern Urals (Russia). The first type of gold-mineralization is widely spread at the massif in the tectonic zones of schistose serpentinites containing typically ≤ 0.1 ppm Au. The second type of gold-ore mineralization is represented by veined massive, streaky and impregnated magnetite ores in contact with serpentinites. It contains to 5 vol.% sulfides and 0.2–1.2 ppm Au. Our thermodynamic calculations explain the formation of two types of gold-ore mineralization in the bedrocks of ultramafic massifs. Metamorphic water, which is the result of the dehydration of early serpentinites (middle Riphean) during high-temperature regional metamorphism (700 °C, 10 kbar) (late Precambrian), is considered as the source of ore-bearing fluid in the models. The metasomatic interaction of metamorphic fluid with serpentinites is responsible for the gold-poor mineralization of the 1st type at T = 450–250 °C and P = 2.5–0.5 kbar. The hydrothermal gold-rich mineralization of the 2nd type was formed during mixing of metamorphic and meteoric fluids at T = 500–400 °C and P = 2–3 kbar and discharge of mixed fluid in the open space of cracks in serpentinites. The model calculations showed that the dominant forms of gold transport in fluids with pH = 3–5 are AuCl2− complexes (≥450 °C) and, as the temperature decreases, AuHS0, or AuOH0. Mineral associations obtained in model calculations are in general similar to the observed natural types of gold mineralization.

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Supergene remobilization of Au in Au-bearing regolith related to orogenic deposits: A case study from Kazakhstan

Cited by 17 publications

References 31 publications

Characteristics of Supergene Gold of Karst Cavities of the Khokhoy Gold Ore Field (Aldan Shield, East Russia)

Characteristics of Supergene Gold of Karst Cavities of the Khokhoy Gold Ore Field (Aldan Shield, East Russia)

Mustard Gold of the Gaching Ore Deposit (Maletoyvayam Ore Field, Kamchatka, Russia)

Formation of Au-Bearing Antigorite Serpentinites and Magnetite Ores at the Massif of Ophiolite Ultramafic Rocks: Thermodynamic Modeling

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