Peter B. Thomas

Dartmouth, N. S.

The West Gore mine was the major producer to antimony in Canada from 1882 to 1939, and it is listed among the gold deposits of Nova Scotia. However, the last comprehensive geological report on the camp dates to 1939. This thesis attempts to provide an up-dated geological description of the West Gore deposit on the basis of a compilation of data from unpublished and published reports and limited field and laboratory work by the author.

The deposit consists of a steep quartz-stibnite complex vein that trends approximately 120o. Stibnite (Sb2S3), native Sb and scarce native gold are the ore minerals that occur in a gangue of quartz and arsenopyrite.

The host rocks consist of slates and minor quartzite of the Halifax Formation (Meguma Group) of Ordovician age, and at least 25 km from the nearest outcrop of Devonian granitoid rocks. The West Gore vein system truncates (and is therefore younger than) the regional metamorphic fabric of the Meguma Group and interbedded quartz-arsenopyrite-gold veins.

Hydrothermal alteration associated with the ore has resulted in strong sericitization of the otherwise chloritic slates. The mineralization appears to have consisted of a combination of open space filling, replacement and remobilization. The first major mineral to crystallize was quartz, followed by movement and brecciation and introduction of stibnite and native antimony, that filled spaces and replaced other minerals. Free gold appears to be limited to the intersection of the steep vein with older, interbedded quartz-arsenopyrite-gold veins at depth.

Fluid inclusion studies yielded anomalously high homogenization temperatures and were inconclusive but may suggest that the fluid inclusions in the quartz leaked during tectonism or that they represent boiling of hydrothermal solutions.

The setting of the West Gore orebody is compared with known Sb-W deposits in Lower Paleozoic black shales elsewhere in Nova Scotia, the Middle East and Western Europe. The possibility of a granitic body at depth and the metasediments as a source for the metals are briefly discussed.

Keywords:
Pages: 105
Supervisors: Marcos Zentilli

Peter is a past president of the Dawson Geology club.
This shot was taken in Peter's field area of West Gore, Nova Scotia.
Peter was demonstrating how to climb around the pond at the bottom of the falls.
Watch out Pete, Slippery when wet.

Petey and the Boys (Joe and Ray)Peter is now living in New Brunswick where he has a consulting business. He is married to a wonderful (she must be a saint) woman named Wendy and has three kids; Joe, Ray and Robin.