scholarly journals Fluid Inclusion Study of the Penjom, Tersang, and Selinsing Orogenic Gold Deposits, Peninsular Malaysia

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 111
Author(s):  
Charles Makoundi ◽  
Khin Zaw ◽  
Zakaria Endut
Keyword(s):  
Fluid Inclusion ◽  
Gold Deposit ◽  
Peninsular Malaysia ◽  
Gold Deposits ◽  
Black Shales ◽  
Orogenic Gold ◽  
Fluid Inclusion Study ◽  
Laser Raman ◽  
Orogenic Gold Deposits ◽  
Basin Scale

Ore-forming fluids in the auriferous district of the Central gold belt in Peninsular Malaysia were studied for their temperature, salinity, and relationship to the surrounding geology. Microthermometric analysis carried out showed homogenisation temperatures range from 210 to 348 °C (Tersang), between 194 and 348 °C (Selinsing), and from 221 to 346 °C (Penjom). Salinities range from 2.41 to 8.95 wt % NaCl equiv (Tersang), between 1.23 and 9.98 wt % NaCl equiv (Selinsing), and from 4.34 to 9.34 wt % NaCl equiv (Penjom). Laser Raman studies indicated that at the Tersang gold deposit, most inclusions are either pure or nearly pure CO2-rich (87–100 mol %), except for one inclusion, which contains CH4 gas (13 mol %). In addition, at Selinsing, most inclusions are CO2-rich (100 mol %). However, an inclusion was found containing CO2 (90 mol %), with minor N2 and CH4. Additionally, at the Penjom gold deposit, most fluid inclusions are CO2-rich (91–100 mol %), whereas one fluid inclusion is N2-rich (100 mol %) and another one has minor N2 and CH4. At a basin scale, homogenisation temperatures against salinity suggests an isothermal mixing of fluids. Most fluids are CO2-rich and are interpreted to be of metamorphic origin. The evidence further indicates involvement of magmatic fluids that is supported by the association of sandstone and carbonaceous black shales with magmatic rocks, such as rhyolite, rhyolite-dacite, and trachyte-andesite at the Tersang and Penjom orogenic gold deposits.

scholarly journals The Neglected Involvement of Organic Matter in Forming Large and Rich Hydrothermal Orogenic Gold Deposits

Geosciences ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 344
Author(s):  
Damien Gaboury
Keyword(s):  
Organic Matter ◽  
Gold Deposits ◽  
Black Shales ◽  
Orogenic Gold ◽  
Redox Activity ◽  
Bacterial Reduction ◽  
Orogenic Gold Deposits ◽  
Three Stages ◽  
Gold Bearing

Orogenic gold deposits have provided most of gold to humanity. These deposits were formed by fluids carrying dissolved gold at temperatures of 200–500 °C and at crustal depths of 4–12 km. The model involves gold mobilization as HS− complexes in aqueous solution buffered by CO2, with gold precipitation following changes in pH, redox activity (fO2), or H2S activity. In this contribution, the involvement of carbonaceous organic matter is addressed by considering the formation of large and/or rich orogenic gold deposits in three stages: the source of gold, its solubilization, and its precipitation. First, gold accumulates in nodular pyrite within carbonaceous-rich sedimentary rocks formed by bacterial reduction of sulfates in seawater in black shales. Second, gold can be transported as hydrocarbon-metal complexes and colloidal gold nanoparticles for which the hydrocarbons can be generated from the thermal maturation of gold-bearing black shales or from abiotic origin. The capacity of hydrocarbons for solubilizing gold is greater than those of aqueous fluids. Third, gold can be precipitated efficiently with graphite derived from fluids containing hydrocarbons or by reducing organic-rich rocks. Black shales are thus a key component in the formation of large and rich orogenic gold deposits from the standpoints of source, transport, and precipitation. Unusual CO2-rich, H2O-poor fluids are documented for some of the largest and richest orogenic gold deposits, regardless of their age. These fluids are interpreted to result from chemical reactions involving hydrocarbon degradation, hence supporting the fundamental role of organic matter in forming exceptional orogenic gold deposits.

Orogenic gold deposits: A proposed classification in the context of their crustal distribution and relationship to other gold deposit types

1998 ◽  
Vol 13 (1-5) ◽  
pp. 7-27 ◽  
Author(s):  
D.I Groves ◽  
R.J Goldfarb ◽  
M Gebre-Mariam ◽  
S.G Hagemann ◽  
F Robert
Keyword(s):  
Gold Deposit ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Orogenic Gold Deposits

A metasedimentary source of gold in Archean orogenic gold deposits

Geology ◽  
2021 ◽  
Author(s):  
Iain K. Pitcairn ◽  
Nikolaos Leventis ◽  
Georges Beaudoin ◽  
Stephane Faure ◽  
Carl Guilmette ◽  
...  
Keyword(s):  
Sedimentary Rock ◽  
Sedimentary Rocks ◽  
Gold Deposits ◽  
Metamorphic Grade ◽  
Orogenic Gold ◽  
Metal Source ◽  
Main Metal ◽  
Metasedimentary Rocks ◽  
Orogenic Gold Deposits ◽  
Archean Orogenic Gold Deposits

The sources of metals enriched in Archean orogenic gold deposits have long been debated. Metasedimentary rocks, which are generally accepted as the main metal source in Phanerozoic deposits, are less abundant in Archean greenstone belts and commonly discounted as a viable metal source for Archean deposits. We report ultralow-detection-limit gold and trace-element concentrations from a suite of metamorphosed sedimentary rocks from the Abitibi belt and Pontiac subprovince, Superior Province, Canada. Systematic decreases in the Au content with increasing metamorphic grade indicate that Au was mobilized during prograde metamorphism. Mass balance calculations show that over 10 t of Au, 30,000 t of As, and 600 t of Sb were mobilized from 1 km3 of Pontiac subprovince sedimentary rock metamorphosed to the sillimanite metamorphic zone. The total gold resource in orogenic gold deposits in the southern Abitibi belt (7500 t Au) is only 3% of the Au mobilized from the estimated total volume of high-metamorphic-grade Pontiac sedimentary rock in the region (25,000 km3), indicating that sedimentary rocks are a major contributor of metals to the orogenic gold deposits in the southern Abitibi belt.

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