Fluid Composition and Source of Early Proterozoic Lode Gold Deposits of the Birimian Volcanic Belt, West Africa

1996 ◽  
Vol 38 (1) ◽  
pp. 22-32 ◽  
Author(s):  
Reiner Klemd ◽  
Ulf Hünken ◽  
Martin Olesch
2021 ◽  
Author(s):  
Wei Jian ◽  
Jingwen Mao ◽  
Bernd Lehmann ◽  
Nigel J. Cook ◽  
Guiqing Xie ◽  
...  

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.


1996 ◽  
Vol 8 (5) ◽  
pp. 937-960 ◽  
Author(s):  
Steffen G. Hagemann ◽  
Philip E. Brown

Geology ◽  
1990 ◽  
Vol 18 (3) ◽  
pp. 238 ◽  
Author(s):  
Daniel J. Kontak ◽  
Paul K. Smith ◽  
Robert Kerrich ◽  
Paul F. Williams

2006 ◽  
Vol 43 (12) ◽  
pp. 1835-1857 ◽  
Author(s):  
A M Goodwin ◽  
M B Lambert ◽  
O Ujike

Late Neoarchean volcanic belts in the southern Slave Province include (1) in the east, the Cameron River – Beaulieu River belts, which are characterized by stratigraphically thin, flow-rich, classic calc-alkaline, arc-type sequences with accompanying syngenetic volcanogenic massive sulphide deposits; and (2) in the west, the Yellowknife belt, which is characterized by stratigraphically thick, structurally complex, pyroclastic-rich, adakitic, back-arc basin-type sequences, with accompanying epigenetic lode-gold deposits. The volcanic belt association bears persuasive chemical evidence of subduction-initiated magma generation. However, the greenstone belts, together with coeval matching patterned belts in Superior Province of the southern Canadian Shield, bear equally persuasive evidence of prevailing autochthonous–parautochthonous relations with respect to component stratigraphic parts and to older gneissic basement. The eastern and western volcanic belts in question are petrogenetically ascribed to a "westerly inclined" (present geography) subduction zone(s) that produced shallower (east) to deeper (west), slab-initiated, mantle wedge-generated, parent magmas. This early stage microplate tectonic process involved modest mantle subduction depths, small tectonic plates, and small sialic cratons. In the larger context of Earth's progressively cooling, hence subduction-deepening mantle, this late Neoarchean greenstone belt development (2.73–2.66 Ga) merged with the massive end-Archean tonalite–trondhjemite–granodiorite–granite (TTGG) "bloom" (2.65–2.55 Ga), resulting in greatly enhanced craton stability. Successive subduction-deepening, plate-craton-enlarging stages, with appropriate metallotectonic response across succeeding Proterozoic time and beyond, led to modern-mode plate tectonics.


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