Tyler Williams Honours Thesis Abstract
St. Andrew Goldfield’s Holloway mine is located along the dextral transpressional steeply south dipping, east to west striking Porcupine Destor Deformation zone. Heterogeneous brittle-ductile deformation characterizes the structural environments that host economical gold mineralization within the Smoke Deep ore zone. Gold mineralization is associated with three different microstructural settings all of which accompany pyrite mineralization. Favorable depositional sites include synkinematic veins, rheological boundaries and felsic lithologies. These settings occur locally within medium-grained to coarse-grained spherulitic felsic lithologies that create competency contrast with the neighbouring southern and northern schistose units. The ore units are interpreted as hypabyssal intrusions of albitite composition, with associated aplite pods. Constituent phenocrysts of the albitites retained their relict shape evident of competency contrast between itself and neighbouring volcanic lithologies. During deformation the formation of microfractures in competent pyrite porphyroblasts aided in the development of low-pressure structural localities conducive to the accumulation of gold from auriferous-carbonate-rich metamorphic fluids. The neighboring schistose units effectively envelope the ore lithologies and are characterized as mylonitized mafic volcanics and metasediments. Metamorphic temperatures within the zone reached lower amphibolite facies conditions indicated by amphibolite textures including kink banding of feldspars, specifically of albite, and the development of subgrains from relict albite and potassium feldspar phenocrysts.