| Summary: | Thesis (M.Sc.)--Memorial University of Newfoundland, 1989. Earth Sciences Bibliography: leaves 243-251 Alteration and gold mineralization in late Precambrian subaerial volcanic rocks on the northern Burin Peninsula of southeastern Newfoundland are compared to younger epithermal systems. Several similarities are revealed when consideration is given to the deformational and metamorphic effects of the (Devonian) Acadian orogeny. -- Conspicuous erosionaliy resistant ridges composed of quartz, alunite, pyrophyllite, specularite, pyrite and rutile cover several thousand m2. These include the Hickey's Pond, Tower and Bullwinkle Showings which are shown to be products of intense surficial acid leaching, a common feature of modern geothermal fields. Specularite-rich hydrothermal breccias (+/- barite) occur at Hickey's Pond and the Bullwinkle showing, and in argillic alteration zones named the Chimney Falls and Strange Showings. Silicification (sensu strido) with incipient brecciation and quartz-pyrite veinlets is locally developed at Hickey's Pond. -- All rock samples collected at Hickey's Pond exhibit anomalous gold concentrations, but similar rocks from the Tower and Bullwinkle showings do not. The highest gold concentrations (5.4 g/t) are in the specularite-rich breccias, followed by the silicified rock with quartz-pyrite veinlets (2.5 g/t Au). Elsewhere, the highest gold concentrations are in specularite-rich breccias at the Strange Showing (0.8 g/t Au) and Chimney Falls (0.3 g/t Au). -- Two mineralizing stages are inferred. The first formed the silicified rock with quartz-pyrite veinlets and is inferred to reflect elevation of the boiling level and precious metal horizon of an ascending hydrothermal fluid into the near- surface environment at Hickey's Pond. The second formed the specularite-rich breccias, to which the only comparable mineralization noted is a baritc-jarositc- goethite-gold assemblage at Summitville, Colorado. Auriferous fluids from both stages flooded the porous and permeable acid leached rocks at Hickey's Pond, creating a large, very low grade gold deposit. The surficial features were buried by renewed volcanism, then subject to greenschist facies metamorphism and strong deformation during the Acadian orogeny. -- The sites of boiling inferred to have accompanied the genesis of the Bullwinkle and Tower Showings are shown to have been favourable sites for gold deposition. Semiquantitative modelling indicates that a significant gold deposit (> 6,000,000 g) could have formed in such (undiscovered) zones.
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