Primary and tectonic features of the Currawong Zn-Cu-Pb(-Au) massive sulfide deposit, Benambra, Victoria; implications for ore genesis

The Late Silurian Currawong Zn-Cu-Pb(-Au) massive sulfide deposit is located in the northeastern highlands of Victoria, southeastern Australia. The Currawong deposit forms two strata-bound concordant massive sulfide lenses which have been dissected by late subvertical faulting. Each massive sulfide lens possesses a concordant stringer system in the footwall to the massive sulfides, which presumably represent major hydrothermal fluid pathways to the mineralization. Host rocks are comprised of subaqueous rhyodacitic to andesitic breccias and coherent volcanic rocks, and equivalent (temporally and spatially) epiclastic rocks that are contained in, and interfinger, with a monotonous succession of turbidites. The geometry and distribution of ore types in the Currawong deposit are characteristic of both sheet- and layered-type deposits as described in Australia. Mineralization is divided into six types: Pb-Zn, pyrite Zn, massive pyrite, pyrite-magnetite, footwall stringer, and overprinting veins and breccias related to local remobilization of base metal sulfides during deformation. Three generations of deformation are recognized in the host stratigraphy. These can be correlated to deformation textures observed within the ore based on consistent structural geometries; unequivocal evidence that mineralization predates the earliest deformation. The internal stratigraphy of the deposit is erratic, with ore facies changing laterally over tens of meters; however, a general vertical zonation of ore types exists within both lenses. From hanging wall to footwall, the zonation is exemplified by: Pb-Zn ore, pyrite Zn ore, intermixed pyrite Zn and massive pyrite ores, and Pb-Zn and pyrite Zn ore associated with sporadic occurrences of hydrothermally altered volcanic rocks. This zonation can be repeated up to three times in lens 1, forming a cyclic distribution. Pyrite-magnetite ore occurs at the base of the deposit located immediately above footwall stringer mineralization. Metal zonation..