The Kalgoorlie gold : a review of factors of formation for a giant gold deposit

Sammanfattning: The Archaean Yilgarn craton in Western Australia is a granite greenstone belt with abundant economically important mineral reserves, including several world-class gold deposits such as the giant Kalgoorlie deposit. Structural controls on gold deposition and the fact that most deposits were formed later in the craton’s tectonic history, has resulted in the general acceptance of a late-orogenic structurally-controlled model for gold mineralization in the Yilgarn craton. However the early establishment of fracture networks and conduits for vertical fluid transport during D1 are considered integral for formation of the Kalgoorlie deposit. This structural evidence has led to contrasting theories on the timing of formation of the Kalgoorlie gold. It also suggests that the factors of formation of the Kalgoorlie gold are possibly different from those of other gold deposits in the Yilgarn. This review paper suggests that the major factors of formation of the giant Kalgoorlie deposit include: 1. Host rock characteristics, such as the anomalous thickness resulting from regional deformation during D1, as well as competency contrasts which increases permeability and thus ore fluid infiltration; 2. Deformational movement creating structural controls and pathways for large-scale fluid transport and efficient fluid focusing, as well as resulting in suitable sites for gold deposition, such as breccias and quartz veins; 3. A protracted mineralization period spanning up to 45 million years, resulting in prolonged periods of fluid focusing and gold deposition. However none of these factors are considered solely responsible for producing a world-class gold deposit. Instead it is suggested that favourable conditions for several factors occurred in conjunction to produce a highly efficient fluid focusing system, and thus the giant Kalgoorlie deposit.