The Provenance of Heavy Minerals in the Mesozoic and Tertiary Formations at the Venture B-13 Borehole, Offshore Nova Scotia, Canada
Yawooz Kettanah and Grant D. Wach
Dalhousie University, Halifax, NS
Sandstones from Jurassic, Cretaceous and Tertiary formations were analyzed for heavy mineral provenances at the Venture gas field (Venture B-13 Borehole), Offshore Nova Scotia. The reservoir sandstones are within the Late Jurassic Mic Mac formation and the Early Cretaceous Missisauga formation. The Missisauga is overlain by other Cretaceous (Logan Canyon, Dawson Canyon, and Wyandot) and Tertiary (Banquereau) formations. Heavy mineral analysis of the sandstone fraction showed variable amounts of opaques (Fe and Fe-Ti oxides), ultrastable (zircon, tourmaline, rutile), stable (staurolite, garnet, apatite, monazite), moderately stable (epidote, sillimanite-kyanite) and rarely unstable minerals. Ultrastable minerals are dominant in all formations, while moderately stable minerals become more abundant in the Tertiary sediments.
Chemical data plotted on triangular diagrams show tourmalines falling in aluminous metapelite and metapsammite / Ca-poor metapelite, metapsammite and quartz-tourmaline rock provenances for the Banquereau and Logan Canyon formations; and Li-poor granitoid, pegmatite and aplite and less Ca-poor metapelite, metapsammite and quartz-tourmaline rocks provenances for the Missisauga formation. Garnet plots show distribution in the fields of granite-granite pegmatites in the Missisauga, and in biotite schists and amphibolite fields (Banquereau) and amphibolite field (Mic Mac and Logan Canyon). These results suggest a dominant granitic and metamorphic provenances. The probable source is the South Mountain Batholith (peraluminous, granodiorite – monzogranite - leucocratic complex of Devonian to Carboniferous age), and the thermal aureole produced by intrusion into the overlying metawackes and slates of the Meguma Supergroup (Cambro-Ordovician) that dominates the geology of the Nova Scotian mainland.