Colloidal origin of colloform-banded textures in the Paleogene low-sulfidation Khan Krum gold deposit, SE Bulgaria

Marinova, Irina; Ganev, Valentin; Titorenkova, Rositsa

doi:10.1007/s00126-013-0473-4

Cited by 30 publications

(13 citation statements)

References 44 publications

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“…The LS ores have electrum ± gold as principal ore minerals, along with associated silver sulfides, selenides, tellurides, and sulfosalts, which generally occur with such gangue minerals as quartz, opal, adularia, and calcite (examples: Sleeper, Round Mountain, Midas, Nevada); (2) High sulfidation or "acid-sulfate" ores that form from acidic solutions (high magmatic: meteoric ratio) with electrum or gold as the main ore mineral, typically associated with the copper-arsenic minerals enargite or luzonite, and quartz, alunite, jarosite, and dickite are the common associated gangue minerals (Examples: Goldfield, Nevada, Summitville, Colorado); and (3) Intermediate sulfidation ores, which are generally transitional between the end members 1 and 2 above, but also have a higher salinity ore-forming solutions, which leads to higher Ag:Au ratios in the ores, higher content of associated base metal-sulfide minerals (examples: Mexican silver deposits; Comstock, Nevada; Creede, Colorado). We, and others [38], have focused on LS ores for our research on metallic nanoparticles, and thus we cannot affirm that they are universally significant in other epithermal ore types, but our cursory observations suggest that they might be. The western United States of America (USA) in general, and Nevada in particular, hosts numerous epithermal ores with representative examples from each of the three of the subdivisions.…”

Section: Bonanza Epithermal Ore Characteristicsmentioning

confidence: 60%

“…The "fractal" electrum dendrites (discussed below) have been observed in many Tertiary bonanza epithermal ores in northern Nevada, and have been interpreted to be evidence of nanoparticle nucleation and aggregation in ore formation [35,36]. More recently, similar textures and genetic interpretations have been made from ores from the southeastern USA [37] and Bulgaria [38]. Finally, disseminated electrum nanoparticles have recently been discovered in the epithermal Round Mountain (Nevada) deposit and have been proposed to be precursors for coarser electrum crystals there [39,40].…”

Section: Introductionmentioning

confidence: 88%

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Formation and Aggregation of Gold (Electrum) Nanoparticles in Epithermal Ores

Saunders

Burke

2017

Minerals

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Here, we review the concept that nanoparticles and colloids may have played a significant role in forming some types of hydrothermal ores deposits, particularly epithermal. This concept was first proposed almost a century ago but the development of new analytical technologies, lab experiments, and the discovery of new epithermal deposits where nanoparticles are evident have added credence to the "gold colloid theory". Nanoparticles are defined to have at least one dimension <10 −7 m, and may have different chemical and physical properties than the bulk solids. Colloids are typically <10 −6 m in diameter and have the added characteristic that they are dispersed in another medium. In epithermal ore-forming solutions, gold or electrum nanoparticles nucleate from supersaturated hydrothermal solutions, and thus this is a "far-from-equilibrium" process. In some cases, gold nanoparticles may simply play a transitory role of aggregating to form much coarser-grained crystals, where all of the evidence of nanoparticles precursor phases is not preserved. However, in some epithermal ores, silica nanoparticles also formed, and their co-deposition with gold (electrum) nanoparticles preserved the gold aggregation features as self-organized "fractal" dendrites. Here, we review existing the data on gold and electrum nanoparticles in epithermal ores, present images of electrum nanoparticles and their aggregates, and discuss the significance of gold nanoparticles formation and aggregation in helping to produce some of the highest-grade gold ores in the world.

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Section: Bonanza Epithermal Ore Characteristicsmentioning

confidence: 60%

Section: Introductionmentioning

confidence: 88%

Formation and Aggregation of Gold (Electrum) Nanoparticles in Epithermal Ores

Saunders

Burke

2017

Minerals

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“…The 'fractal' electrum dendrites have been observed in many the Tertiary bonanza epithermal ores in northern Nevada, and have been interpreted to be evidence of nanoparticle nucleation and aggregation in ore formation. More recently, similar textures and genetic interpretations have been made from ores from the southeastern USA [33] and Bulgaria [35]. Finally, disseminated electrum nanoparticles have recently been discovered in the epithermal Round Mountain (Nevada) deposit and have been proposed to be precursors for coarser electrum crystals there [36,37].…”

Section: Discussionmentioning

confidence: 79%

“…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. [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Sometimes massive gold occurs in assemblage with siderite ( Figure 5e,f, 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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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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“…Two models have been proposed to explain the origin of these textures: (i) epitaxial overgrowth of small quartz crystals on large existing quartz crystals (Dong et al, 1995) and iicrystallization from former fibrous, water-rich chalcedony (Sander and Black, 1988). Recently, Marinova et al (2014) has reported that feathery textures are generally accepted as being a re-crystallization product from chalcedony in the context of having a gel precursor.…”

Section: Introductionmentioning

confidence: 99%

Feathery and network-like filamentous textures as indicators for the crystallization of quartz from a silica gel precursor at the Rusey Fault, Cornwall, UK

Yilmaz

Duschl

Genova³

2016

Preprint

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Abstract. Quartz crystals from a hydrothermal shear-zone-hosted quartz deposit (Rusey Fault, Cornwall, UK) show feathery textures and network-like filamentous textures. Optical hot-cathodoluminescence (CL) analysis and LA-ICP-MS investigations on quartz samples revealed that positions exhibiting feathery textures (violet luminescence) incorporate higher amounts of Ca, As, Na, Mg, and K than quartz positions without feathery textures (blue luminescence). Raman spectroscopy investigations revealed the presence of a weak peak ("shoulder") at 507–509 cm−1 in quartz affected by feathery textures, which we attribute to the presence of moganite, a microcrystalline silica variety. The combined occurrence of feathery textures and network-like filamentous textures in quartz samples from the Rusey fault zone points to the presence of a silica gel precursor before or during the crystallization.

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Colloidal origin of colloform-banded textures in the Paleogene low-sulfidation Khan Krum gold deposit, SE Bulgaria

Cited by 30 publications

References 44 publications

Formation and Aggregation of Gold (Electrum) Nanoparticles in Epithermal Ores

Formation and Aggregation of Gold (Electrum) Nanoparticles in Epithermal Ores

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

Feathery and network-like filamentous textures as indicators for the crystallization of quartz from a silica gel precursor at the Rusey Fault, Cornwall, UK

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