Volcanic and hydrothermal reconstruction of the Pilley's Island volcanogenic massive sulfide district, central Newfoundland

McKinley, Conor Patrick (2013) Volcanic and hydrothermal reconstruction of the Pilley's Island volcanogenic massive sulfide district, central Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Pilley's Island in the Central Mobile Belt, Newfoundland, Canada, is host to a cluster of bimodal felsic Zn-Pb-Cu-Au-Ag volcanogenic massive sulfide (VMS) deposits. In the Pilley's Island terrane, VMS-bearing felsic volcanic rocks are derived from the remelting of a hydrated, arc basalt substrate; these have been juxtaposed by thrust faulting against barren mafic volcanic rocks derived from partial melting of slab metasomatized mantle wedge within an Ordovician peri-Laurentian subduction zone. -- Sulfide formation likely took place within a peri-Laurentian arc rift based on immobile element signatures. The deposits formed via sub-seafloor replacement of volcanic flows or volcaniclastic strata, with evidence including: large, gradational alteration and mineralization haloes surrounding the deposits and relict host rock fragments with in the sulfide. -- Zones proximal to mineralization exhibit muscovite ± illite alteration and elemental vectors to mineralization include loss of SiO₂, CaO, Na₂O and grains of Fe₂O₃, K₂O, base metals, and volatile elements (As, Sb, Tl).

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