LE3 .A278 2019

2019

Barr, Sandra

Acadia University

Bachelor of Science

Honours

Geology

Earth & Environmental Sciences

The Faribault Brook Formation forms the lower part of the Jumping Brook Metamorphic Suite which underlies a large part of the western Cape Breton Highlands east of Cheticamp. It consists mainly of variedmafic metavolcanic rocks interlayered with metawacke similar to that in the overlying Dauphinee Brook Formation. Both formations host occurrences of sulphide minerals, Au, and Ag; however, the rocks are strongly deformed and metamorphose, and stratigraphic relationships and the nature of the mineral occurrences that they contain are poorly understood. In this study, core from two drill holes, GM-08-08 and FB-01-86/08, was logged in detail by visual inspection combined with magnetic susceptibility measurements, petrographic study of representative thin and polished sections, and chemical analyses. In combination these data enabled identification of greenschist-facies metabasalt, metatuff, metawacke, and metarhyolite, intruded by thin sills of younger unmetamorphosed amygdaloidal basalt. The mafic units are difficult to distinguish based on petrography as all are dominated by actinolitic amphibole chlorite, epidote, plagioclase, and quartz and have similar low magnetic susceptibilities. Hence protolith variations were distinguished geochemically using immobile elements and elemental ratios, including Zr/TiO2, Zr/Y, and Nb/Y. As in other studies of metabasic rocks in the Faribault Brook Formation, the mafic samples display depletion in Nb and light rare earth elements, and overall the chemical characteristics are those of mid-ocean ridge basalt erupted or intruded in association with turbiditic wacke in a back-arc basin. Sulphide mineral as well as gold occur as disseminations in the metabasic rocks and in association with quartz-carbonate veins parallel to and locally cross-cutting the foliation. The rocks have potential to contain economic deposits of both volcanogenic massive sulphide and vein type.

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https://scholar.acadiau.ca/islandora/object/theses:3274