Forms of Gold and Some Typomorphic Characteristics of Native Gold of the Pavlik Orogenic Deposit (Magadan Oblast)

AbstractThe Çöpler gold deposit occurs within the stockwork of quartz hosted by the Çöpler granitoid (Eosen) and by surrounding metasediments of Keban metamorphic (Late Paleozoic - Early Mesozoic) and the Munzur limestones (Late Carboniferous - Early Cretaceous).Native gold accompanied by small amounts of chalcopyrite, pyrite, magnetite, maghemite, hematite, fahlerz, marcasite, bornite, galena, sphalerite, specular hematite, goethite, lepidochrosite and bravoitic pyrite within the stockwork ore veinlets. In addition, epidote (pistazite - zoisite), garnet, scapolite, chlorite, tremolite/actinolite, muscovite and opaque minerals were determined within the veinlets occurred in skarn zones.The study of fluid inclusions in quartz veinlets showed that the hydrothermal fluids contain CaCl2, MgCl2 and NaCl and the salinities of the two phases (L+V) inclusions range from 1.7 to 20.6% NaCl equivalent. Salinity values up to 44% were determined within the halite bearing three phases inclusions. Their homogenization temperature values have a wide range from 145.0 to 380.0°C, indicative of catathermal/hypothermal to epithermal conditions. The δ 18O and δD values of the fluid inclusion waters from the Çöpler granitoid correspond to those assigned to Primary Magmatic Water, those from the metasediments of Keban metamorphics fall outside of the Primary Magmatic and are within the Metamorphic Water field. A sample from a quartz vein within the skarn zone hosted by the Munzur limestones has a particularly low δD value.The results suggest that fluids derived from the granitoids were mixed with those derived from the metasediments of Keban metamorphics and the the Munzur limestones and resulting in quartz veinlets in these lithologies and the formation of stockwork ores. In view of the occurrence, the features described and processes envisaged for this study area may be applicable in similar settings.

Download Full-text

Genesis of Precious Metal Mineralization in Intrusions of Ultramafic, Alkaline Rocks and Carbonatites in the North of the Siberian Platform

Minerals ◽

10.3390/min11040354 ◽

2021 ◽

Vol 11 (4) ◽

pp. 354

Author(s):

Anatoly M. Sazonov ◽

Aleksei E. Romanovsky ◽

Igor F. Gertner ◽

Elena A. Zvyagina ◽

Tatyana S. Krasnova ◽

...

Keyword(s):

High Temperature ◽

Siberian Platform ◽

Precious Metal ◽

Native Gold ◽

Precious Metals ◽

Ore Formation ◽

Central Type ◽

Alkaline Rocks ◽

The North ◽

Pge Mineralization

The gold and platinum-group elements (PGE) mineralization of the Guli and Kresty intrusions was formed in the process of polyphase magmatism of the central type during the Permian and Triassic age. It is suggested that native osmium and iridium crystal nuclei were formed in the mantle at earlier high-temperature events of magma generation of the mantle substratum in the interval of 765–545 Ma and were brought by meimechite melts to the area of development of magmatic bodies. The pulsating magmatism of the later phases assisted in particle enlargement. Native gold was crystallized at a temperature of 415–200 °C at the hydrothermal-metasomatic stages of the meimechite, melilite, foidolite and carbonatite magmatism. The association of minerals of precious metals with oily, resinous and asphaltene bitumen testifies to the genetic relation of the mineralization to carbonaceous metasomatism. Identifying the carbonaceous gold and platinoid ore formation associated genetically with the parental formation of ultramafic, alkaline rocks and carbonatites is suggested.

Download Full-text

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

Minerals ◽

10.3390/min11050451 ◽

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.

Download Full-text

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

Russian Journal of Pacific Geology ◽

10.1134/s1819714021040035 ◽

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

Download Full-text

An Application for Thermodynamic Calculation of AuxAg1 – x-Fluid Equilibria: Super-Pure Native Gold in Woxi Au–Sb–W Deposit, Western Hunan, China

Geochemistry International ◽

10.1134/s0016702920130054 ◽

2021 ◽

Vol 59 (3) ◽

pp. 314-327

Author(s):

Y. Liang ◽

J. S. Zhong ◽

Q. M. Pei ◽

K. Hoshino

Keyword(s):

Thermodynamic Calculation ◽

Native Gold ◽

Western Hunan

Download Full-text

The occurrence of gold in Voia deposit, South Apuseni Mountains, Romania

10.5194/egusphere-egu21-4813 ◽

2021 ◽

Author(s):

Elena-Luisa Iatan

Keyword(s):

Iron Oxides ◽

Base Metal ◽

Mineral Assemblage ◽

Native Gold ◽

Metal Sulfides ◽

Volcanic Complex ◽

Apuseni Mountains ◽

Base Metal Sulfides ◽

Mineral Assemblages ◽

Phyllic Alteration

Voia deposit belongs to the S&#259;c&#259;r&#226;mb-Cetra&#537;-Cordurea Miocene volcano-tectonic alignment of the South Apuseni Mountains, Romania. This large volcanic complex represents a Sarmatian-Pannonian magmatic-hydrothemal mega-system of around 5 km2 with an estimated 3&#8211;4 Ma time-space evolution, consisting of seven andesitic volcanic structures grouped in a circle, three subvolcanic andesite-quartz porphyry microdiorite and associated porphyry Cu-Au(Mo), pyrite Ca-Mg skarns and epithermal Au-Ag-Pb-Zn-Cu mineralizations.The mineral assemblages of alteration and mineralization processes belong to several mineralized zones on a vertical scale, according to sampling evidence and laboratory studies. HS products are found in the upper part of the structure (300-500 m), with dominant advanced and intermediate argillic alterations and sulfide-sulfate gold-poor veins (pyrite, marcasite, base metal sulfides, Fe-Ti oxides, vuggy quartz, alunite, gypsum, anhydrite). Within the 500-1200 m depth, the HS mineral assemblages gradually decrease in favor of IS and LS products. It is characterized by the coexistence of gold-rich LS assemblage (native gold, base metal sulfide, adularia, sericite-illite, chlorite, carbonates &#177; anhydrite veins), with the IS assemblage (iron oxides, chalcopyrite, pyrite, quartz, anhydrite). These assemblages overprint the HS mineral associations, resulting in a transition zone characterized by gold - pyrite - chalcopyrite - iron oxides - quartz - anhydrite mineral assemblage characteristic for HS and native gold - pyrite - base metal sulfides - carbonates - quartz mineral assemblage corresponding to IS+LS type.Gold is present in all of the identified mineralization forms: porphyry-epithermal Cu-Au, epi-mesothermal carbonate veins with gold - base metal sulfides, quartz veins with pyrite - chalcopyrite - magnetite &#177; hematite &#177; anhydrite, anhydrite veins with base metal sulfides and sulfosalts, anhydrite veins with pyrite - anhydrite &#177; quartz, vuggy quartz (silica residue) with gold-poor pyrite veins and impregnations in porphyry systems.Drilling core samples revealed that in Voia deposit, gold is concentrated in chalcopyrite (drills no. 7, 19, 37) along with pyrite - magnetite - hematite - quartz assemblage from the late potassic stage. The major amount of gold associated with chalcopyrite tends to be mainly submicroscopic. Pyrite from anhydrite veins of the early potassic stage &#177; phyllic alteration is relatively poor in gold (drills no. 1-6, 8-14). However, the highest gold contents are present in pentagonal dodecahedron pyrites (drills no. 33, 38, 39) of pyrite-chalcopyrite-magnetite &#177; hematite-quartz assemblage from late potassic stage &#177; phyllic alteration. Pyrite associated with magnetite from anhydrite veins tends to be poor in gold (drills no. 8, 11, 15, 28, 29). A carbonate vein containing gold-bearing base metal sulfides that was intercepted at 960,00-960,30m depth by drill no. 17 is one of the richest in gold.Native gold occurs as fine inclusions in ore minerals (5-20 &#956;m). Large irregular grains of native gold (>50 &#956;m) appear at mineral boundaries and along the fissures. The gold color is bright yellow and has a measured Au:Ag ratio of 5:1, suggesting that native gold has been formed at a relatively high temperature.Acknowledgments: This work was supported by two Romanian Ministry of Research and Innovation grants: PN-III-P4-ID-PCCF-2016-4-0014 and PN-III-P1-1.2-PCCDI-2017-0346/29.

Download Full-text