Sir:Wilson et al. (2003), in their important paper on the Ridgeway Au-Cu deposit, describe hydrothermal alteration about the Ridgeway porphyry ore system. However, their findings are substantially more valuable if taken into account with the published works on regional burial metamorphism of the district (Smith, 1968, 1969). These works described burial metamorphism of the Ordovician volcanic sequences, including the hosts to the Ridgeway deposit, based on district and regional zonation of secondary mineral assemblages. This discussion briefly presents this context and focuses on the key issue of discriminating the porphyry-related hydrothermal alteration from the effects...

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