RE: Scallywag video 121 Jan 2021 23:14
This is to do with changes in the magma from 10km depth at 3kbar pressure at Malartic and how its ph and alkaline changes as it passes metasedimentary and mafic-ultramafic rocks
"Consistent with the constraints noted, we propose a genetic model for the Canadian Malartic deposit in which felsic to intermediate, borderline alkaline to subalkaline magmas, emplaced at midcrustal levels, exsolved relatively oxidized (logfO2~-19)
......,
?, CO2- and sulfur-rich (?aS = 0.1) auriferous fluids. These fluids rose to higher levels (~10 km; ~3 kbars), where they interacted with associated porphyritic monzodiorite intrusions, clastic Pontiac metasedimentary and Piché Group mafic to ultramafic rocks. The porphyries and metasedimentary rocks buffered the fluids to near-neutral pH, whereas the mafic-ultramafic rocks buffered the fluids to higher pH and lower fO2
?. Ore deposition resulted from pyritization of the host rocks and oxidation of the mineralizing fluid, which reduced aH2S
and caused destabilization of gold bisulfide species, leading to precipitation of native gold.