The origin of barite and related veins on the Avalon Peninsula of Newfoundland

Maloney, James Andrew (1990) The origin of barite and related veins on the Avalon Peninsula of Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Hydrothermal barite ± calcite ± sulphide mineral veins occur in Newfoundland on the Isthmus of Avalon and along the west, southern and south-eastern coasts of the Cape St. Mary's area of the Avalon Peninsula. Earlier formed quartz-dominated veins are the most abundant vein type in this area and occur over a much larger area. The data collected in this study (field relationships, paragenetic data, fluid inclusion data, carbon, oxygen and sulphur isotope data, REE data) allow for the following conclusions: -- 1) The early quartz ± chlorite veins were formed during a regional deformational and low-grade metamorphic event, by precipitation in fracture sets developed during this deformation. -- 2) During this deformational event a hot pulse of hydrothermal fluid moved through the same fracture set in more localized areas. This later fluid pulse deposited sulphide-mineral-dominated veins where it was hottest and presumably closest to its source. Further from the source, where the fluid was cooler, calcite- and barite-dominated veins were precipitated. -- 3) The proximity of the "hottest" sulphide-dominated veins to known syndeformational granitic intrusions, combined with the geochemical evidence, strongly suggest that the hot fluid pulse was sourced by fluid exsolved during crystallization of these granitic magmas. Carbon, oxygen, sulphur and rare earth elements were all likely sourced from these granitic melts as well. In some of the veins studied, there is evidence that elemental and isotopic exchange took place between this magmatic fluid and either the surrounding country rock or meteoric waters.

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