Carbon isotope evidence for a magmatic origin for Archaean gold-quartz vein ore deposits

Abstract

Archaean gold-quartz vein/shear zone systems constitute one of the most important types of gold ore deposit; however, their origin is controversial. Here we discuss newly obtained δ13C(PDB) values for carbonate associated with the second largest such system in the world (Hollinger–McIntyre, Superior Province, Canada), together with values for fourteen other Au-mineralized locations in the Timmins area1 and for the largest such system in the world (Golden Mile, Western Australia2). All of the data are statistically identical to the δ13C values, reported here, of proven magmatic carbonate recently found with Au- and W-enriched MoS2 mineralization in the Mink Lake sodic granodiorite stock, northwest Ontario. The δ13C values appear to exclude greenschist–amphibolite facies metamorphic processes, a widely accepted genetic alternative3–6, and granulite facies processes7,8. We conclude that currently available carbon isotope data suggest that the H2O–CO2 fluid which deposited this type of Archaean Au mineralization was magmatically derived.