Resolving the role of carbonaceous material in gold precipitation in metasediment-hosted orogenic gold deposits

Geology ◽  
2016 ◽  
Vol 45 (2) ◽  
pp. 167-170 ◽  
Author(s):  
Si-Yu Hu ◽  
Katy Evans ◽  
Dave Craw ◽  
Kirsten Rempel ◽  
Kliti Grice
Keyword(s):  
Carbonaceous Material ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
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.

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.

Lithospheric controls on the formation of provinces hosting giant orogenic gold deposits

2006 ◽  
Vol 40 (8) ◽  
pp. 874-886 ◽  
Author(s):  
Frank P. Bierlein ◽  
David I. Groves ◽  
Richard J. Goldfarb ◽  
Benoit Dubé
Keyword(s):  
Gold Deposits ◽  
Orogenic Gold ◽  
Orogenic Gold Deposits

A Tentative Study of Relationship between Mantle Plumes, Supercontinents and Orogenic Gold Deposits

2013 ◽  
Vol 734-737 ◽  
pp. 265-268
Author(s):  
Jun Hao Cui ◽  
Tao Ren
Keyword(s):  
Mantle Plume ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Upper Crust ◽  
Orogenic Gold Deposits ◽  
Orogenic Gold Deposit ◽  
The Earth ◽  
Tectonic Environment ◽  
The Relationship

On the basis of predecessors study, this paper found that outbreak frequency of mantle plume is increase, while scale is reduce. The mantle plume provides ore-forming minerals to orogenic gold deposits, as well as affords force to supercontinent formation and decomposition, for the more controls the global tectonic. Supercontinent is the movement of upper crust that could be cause by combine factors of cold and heat mantle plume. Supercontinent supply suitable tectonic environment for orogenic gold deposits. Further, we discuss the relationship between mantle plume, supercontinent and orogenic gold deposit on space and time. With the evolution of the earth, especially the energy loss, the frequency of orogenic gold mineralization is increasing, while the scale is reducing.

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