Page 97 - Handbook of Gold Exploration and Evaluation

78 Handbook of gold exploration and evaluation

2.8 The Chillagoe goldfield, North Queensland.

of the ice sheets and the redistribution of weight at the beginning of the
Cambrian period. The Dargalong Metamorphics stretched and eventually broke
and the Palmerville fault started to move. Continental Australia underwent
intense weathering and erosion each time it was uplifted. At least 8 km thickness
of crust was planed off the Dargalong Metamorphics in the period from 550±450
million years ago reducing the ranges into gently undulating hills which again
rose due to isostatic adjustment. Melting took place at depth and the molten
granitic rocks moved up along tensional fractures in the Dargalong
Metamorphics to solidify some kilometres from the surface as the Nundah
Granodiorite. The metal-rich steam released from the granodiorite formed a halo
of water-rich minerals glinting with uranium, thorium and gold.