Basement metal scavenging during basin evolution:Cambrian and Proterozoic interaction at the Century Zn [sbnd]Pb [sbnd]Ag Deposit, Northern Australia

Abstract

In some Phanerozoic base metal provinces floored by continental crust (Mississippi Valley, Irish midlands), controversy has arisen concerning whether basement rocks contribute significantly to the metal (and isotope) budgets, as opposed to surface or basinal fluids and rocks. For the Mesoproterozoic Century Zn-Pb-Ag deposit, we demonstrate that fluids associated with compaction of overlying Cambrian limestones penetrated the deposit, scavenged lead and zinc, and redeposited them in the limestones. This circulation was accompanied by penetration of carbonate breccia dykes into the basement, formation of shallow dipping shear zones and folds in the cover, and development of sulphide-bearing veins and stylolites. The process was facilitated by syn- or post-Cambrian reactivation of the Termite Range Fault, which was previously active during the Proterozoic ore deposition.