Au-Ag-Te–RICH MELT INCLUSIONS IN HYDROTHERMAL GOLD-QUARTZ VEINS, XIAOQINLING LODE GOLD DISTRICT, CENTRAL CHINA

2021 ◽  
Author(s):  
Wei Jian ◽  
Jingwen Mao ◽  
Bernd Lehmann ◽  
Nigel J. Cook ◽  
Guiqing Xie ◽  
...  
Keyword(s):  
Melt Inclusions ◽  
Experimental Studies ◽  
Gold Deposits ◽  
Central China ◽  
Lode Gold ◽  
Quartz Veins ◽  
The North ◽  
Reduction Mechanisms ◽  
Adsorption Reduction ◽  
Lode Gold Deposits

Abstract We present petrographic and microthermometric evidence for precipitation of Au-Ag-Te–rich melt directly from hydrothermal fluids and subsequent entrapment as primary melt inclusions within pyrite from quartz veins of the Xiaoqinling lode gold district, southern margin of the North China craton. We propose the formation of Au-Ag-Te–rich melt through adsorption-reduction mechanisms on pyrite and subsequent growth of the melt nuclei via direct scavenging of metals from fluids. Because neither initial formation nor later growth of the melt require saturation of the ore fluid with respect to the constituent metals, this mechanism offers a new understanding of the enrichment of low-abundance ore components, such as gold. Our model may thus partly explain the discrepancy between the high gold solubilities reported from experimental studies and the much lower gold concentrations usually measured in natural fluids. This study also implies that Au-Ag-Te–rich melt has probably gone unrecognized in other lode gold deposits in which Au-Ag tellurides are present.

scholarly journals The Lode Gold Occurrence in the «Territory» of Oleg Kuvaev (North of the Chukotka Upland)

2021 ◽  
Vol 20 (3) ◽  
pp. 250-266
Author(s):  
V.I. Silaev ◽  
◽  
A.V. Kokin ◽  
V.N. Filippov ◽  
A.F. Khazov ◽  
...  
Keyword(s):  
Quartz Vein ◽  
Native Gold ◽  
Gold Deposits ◽  
Lode Gold ◽  
Carbon Particles ◽  
The North ◽  
Aluminium Sulfate ◽  
Gold Silver ◽  
Lode Gold Deposits ◽  
Gold Sulfide

A sample of a gold-bearing quartz vein from the Upper-Ichuveem ore occurrence, discovered in the Triassic terrigenous complex in the north of the Chukotka Upland, the Oleg Kuvaev's “Territory”, had been comprehensively studied. The gross gold grade was estimated at 3–4 g / t. The vein includes quartz, native gold, sulfide-goldsilver solid solutions, alumoseladonite, aluminium-sulfate-phosphates Fe-Pb-Mg-Ca compound, apatite, pyrite, iron-titanium oxides, litharge, native phases composed of Fe (Ni), Ag-Pb-Bi, Fe-Al-PS-As, multicomponent ocher of hypergene origin. Native gold ranges from medium to fine. The vein contains particles of non-crystalline organic matter, which is close in composition of organic groups to polysaccharides. It is possible that the carbon particles found in the gold-quartz vein are of an abiogenic nature and can be compared with abiogenic condensed organelles in the products of modern volcanism. The data obtained make it possible to attribute the Upper- Ichuveem gold ore occurrence to a low-sulfide gold-quartz formation, but with additional signs of gold-silver and polymetallic formations, which can be regarded as a favorable prerequisite for prospecting and exploration in Oleg Kuvaev's «Territory» not only of gold-placer deposits, but also of lode gold deposits.

scholarly journals Metasomatized lithospheric mantle for Mesozoic giant gold deposits in the North China craton

Geology ◽  
2019 ◽  
Vol 48 (2) ◽  
pp. 169-173 ◽  
Author(s):  
Zaicong Wang ◽  
Huai Cheng ◽  
Keqing Zong ◽  
Xianlei Geng ◽  
Yongsheng Liu ◽  
...  
Keyword(s):  
North China Craton ◽  
Lithospheric Mantle ◽  
North China ◽  
Mantle Metasomatism ◽  
Gold Deposits ◽  
Mantle Xenoliths ◽  
Lode Gold ◽  
The North ◽  
Craton Destruction ◽  
Lode Gold Deposits

Abstract The origin of giant lode gold deposits of Mesozoic age in the North China craton (NCC) is enigmatic because high-grade metamorphic ancient crust would be highly depleted in gold. Instead, lithospheric mantle beneath the crust is the likely source of the gold, which may have been anomalously enriched by metasomatic processes. However, the role of gold enrichment and metasomatism in the lithospheric mantle remains unclear. Here, we present comprehensive data on gold and platinum group element contents of mantle xenoliths (n = 28) and basalts (n = 47) representing the temporal evolution of the eastern NCC. The results indicate that extensive mantle metasomatism and hydration introduced some gold (<1–2 ppb) but did not lead to a gold-enriched mantle. However, volatile-rich basalts formed mainly from the metasomatized lithospheric mantle display noticeably elevated gold contents as compared to those from the asthenosphere. Combined with the significant inheritance of mantle-derived volatiles in auriferous fluids of ore bodies, the new data reveal that the mechanism for the formation of the lode gold deposits was related to the volatile-rich components that accumulated during metasomatism and facilitated the release of gold during extensional craton destruction and mantle melting. Gold-bearing, hydrous magmas ascended rapidly along translithospheric fault zones and evolved auriferous fluids to form the giant deposits in the crust.

scholarly journals Genesis of the Longmendian Ag–Pb–Zn Deposit in Henan (Central China): Constraints from Fluid Inclusions and H–C–O–S–Pb Isotopes

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-21
Author(s):  
Xinglin Chen ◽  
Yongjun Shao ◽  
Chunkit Lai ◽  
Cheng Wang
Keyword(s):  
Fluid Inclusions ◽  
Central China ◽  
Granitic Magma ◽  
Two Phase ◽  
Quartz Veins ◽  
The North ◽  
Granitic Magmatism ◽  
Polymetallic Sulfides ◽  
Homogenization Temperatures ◽  
Stage 1

The Longmendian Ag–Pb–Zn deposit is located in the southern margin of the North China Craton, and the mineralization occurs mainly in quartz veins, altered gneissic wallrocks, and minor fault breccias in the Taihua Group. Based on vein crosscutting relations, mineral assemblages, and paragenesis, the mineralization can be divided into three stages: (1) quartz–pyrite, (2) quartz–polymetallic sulfides, and (3) quartz–carbonate–polymetallic sulfides. Wallrock alteration can be divided into three zones, i.e., chlorite–sericite, quartz–carbonate–sericite, and silicate. Fluid inclusions in all Stage 1 to 3 quartz are dominated by vapor-liquid two-phase aqueous type (W-type). Petrographic and microthermometric analyses of the fluid inclusions indicate that the homogenization temperatures of Stages 1, 2, and 3 are 198–332°C, 132–260°C, and 97–166°C, with salinities of 4.0–13.3, 1.1–13.1, and 1.9–7.6 wt% NaCleqv, respectively. The vapor comprises primarily H2O, with some CO2, H2, CO, N2, and CH4. The liquid phase contains Ca2+, Na+, K+, SO42−, Cl−, and F−. The sulfides have δ34S=–1.42 to +2.35‰ and 208Pb/204Pb=37.771 to 38.795, 207Pb/204Pb=15.388 to 15.686, and 206Pb/204Pb=17.660 to 18.101. The H–C–O–S–Pb isotope compositions indicate that the ore-forming materials may have been derived from the Taihua Group and the granitic magma. The fluid boiling and cooling and mixing with meteoric water may have been critical for the Ag–Pb–Zn ore precipitation. Geological and geochemical characteristics of the Longmendian deposit indicate that the deposit is best classified as medium- to low-temperature intermediate-sulfidation (LS/IS) epithermal-type, related to Cretaceous crustal-extension-related granitic magmatism.

Chapter 37: Giant Placers of the Upper Kolyma Gold Fields, Yana-Kolyma Province, Russian Northeast

2020 ◽  
pp. 797-821
Author(s):  
N. A. Goryachev ◽  
A. S. Yakubchuk ◽  
I. S. Litvinenko ◽  
A. V. Lozhkin ◽  
Yu.V. Pruss ◽  
...  
Keyword(s):  
Late Jurassic ◽  
Climatic Factors ◽  
Gold Deposits ◽  
Passive Margin ◽  
Northeastern Russia ◽  
Quartz Veins ◽  
Orogenic Gold Deposits ◽  
The North ◽  
Lithospheric Plates ◽  
Rock Source

Abstract The Upper Kolyma gold placers of northeastern Russia produced 2,700 metric tons (t) Au. Approximately 40% of this gold was extracted from just five placers, Chai-Yuria, Berelekh, Maldyak, Malyi At-Yuryakh, and Omchak, and their immediate tributaries. The placers were derived from Late Jurassic to Early Cretaceous lode deposits, formed during sinistral translation subsequent to the Kolyma-Omolon superterrane accretion to the Verkhoyansk passive margin of the Siberian craton. The metallogenic events produced either abundant and widespread small quartz veins or more localized large to superlarge quartz stockworks and disseminated gold deposits. These orogenic gold deposits acted as a principal hard-rock source during formation of the gold placers, beginning in the Late Cretaceous but most importantly during the Cenozoic. Tectonic, geomorphologic, and climatic factors at a triple junction of the North American, Eurasian, and Okhotsk lithospheric plates provided the ultimate controls on placer formation.

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