Structural Controls on gold mineralization on the margin of the Yilgarn craton, Albany–Fraser orogen: The Tropicana Deposit, Western Australia

25 26 The Tropicana gold deposit is located adjacent to the margin of the Yilgarn craton in 27 the Albany–Fraser orogen, Western Australia. The deposit is hosted in granulite facies 28 quartzo-feldspathic gneisses of the Archean Tropicana Gneiss. Ore bodies comprise 29 biotite-pyrite alteration concentrated in shear zones that formed during NE-SW 30 shortening in the late Archean, and clearly postdate the formation and deformation of 31 high-grade gneiss fabrics (D1 and D2). The orientation of the ore bodies is controlled 32 by the shear zones that are in turn localised by the gneissic banding. Mineralization 33 also involved solution and coeval microfracturing and veining of more competent 34 pegmatitic units. The mineralizing event (D3) was followed by at least two further 35 deformations, which reactivated and overprinted the biotite fabrics with sericite and 36 chlorite, created new shear zones, and affected gold distribution. D5 consisted of 37 dextral shear on ~E-W shear zones, which subdivide the deposit into five major 38 structural domains. The importance of structurally controlled permeability at 39 Tropicana is similar in cratonic lode gold deposits, as is the protracted 40 deformation/fluid flow history. Like Renco mine in Zimbabwe, Tropicana gold 41 deposit was formed by hydrothermal fluid flow peripheral to the craton: economic 42 gold mineralization was clearly post-peak metamorphism. 43 44 M AN US CR IP T AC CE PT ED ACCEPTED MANUSCRIPT