3.26 Ga black smoker-type mineralization in the Strelley Belt, Pilbara Craton, Western Australia

Abstract

Early Archaean (3.26 Ga) volcanogenic massive sulphide (VMS) deposits located within the low strain and very-low metamorphic grade Strelley greenstone belt, East Pilbara, Western Australia, contain exceptionally well-preserved sulphide textures which are directly analogous to those formed in black smoker chimneys at present-day submarine hydrothermal vents. The VMS deposits are associated with seafloor alteration zones in and below silicacarbonate laminites, at the top of a pile of tholeiitic to calc-alkaline intermediate and felsic volcanic rocks with trace element abundances indicative of modem subduction-related processes. VMS mineralization comprises Zn-rich sulphide lenses with significant Cu and barite, and variable Pb and Ag, above Cu-rich stringer zones, all of which are similar to Phanerozoic VMS deposits. Sulphide-sulphate mineralization implicates hydrothermal discharge into sulphate-bearing ocean waters.