The role of transient pressure gradients in mid-crustal advective mass transfer

Abstract

Abrupt pore pressure changes accompanying faulting can compete with, or locally predominate over, thermal gradients, in their capacity to transfer mass in deep hydrothermal systems. Differential mass transfer at 1- to >1000-m scales in the mesothermal Cloncurry Fe oxide-Cusingle bondAu district of northern Australia was apparently controlled by pore pressure cycling around dilatant parts of shear and fault zones. Geochemical reaction modelling of pore pressure drops in fluids initially equilibrated with altered wallrocks in the Cloncurry district produces model vein assemblages that mimic those observed in the field, whereas temperature-drop scenarios fail to replicate these veins.