Geology and Structure of the Thompson 1-D Deposit
The Thompson Nickel Belt is a linear feature 8-40 kilometres wide that extends for more than 160 kilometres along the boundary between the Churchill and Superior geological provinces. Reworked Archean basement gneisses and Early Proterozoic (1.8 – 1.9 Ga) cover rocks are intensely deformed and have been metamorphosed to amphibolite-granulite facies.
The Proterozoic Ospwagan Group assemblage exhibits a distinct and predictable tectonostratigraphy that is indicative of shelf margin to deep basin depositional environments. Ultramafic bodies silled into the P2 unit, assimilated the pelitic-graphitic-sulphidic sediments, and magmatic Ni sulphides were deposited.
During orogenesis, the sediment pile was affected by polyphase deformation and related high pressure – high temperature metamorphism. Shearing in F2 and F3 deformation resulted in dilatant zones and mobilization of Ni sulphides into the zones. The kinematics of the shear zones affected the size, shape and orientation of the dilatant structures.
Recent exploration strategies for the Thompson 1D Deposit include structural analysis to determine the location and geometries of dilatant zones. Oriented core provides accurate structural information allowing for projection of structural trends and patterns away from boreholes. Targeting can then concentrate on areas where structural measurements predict shear kinematics favorable to dilatant zone development.
In areas lacking structural information, targeting is influenced by large-scale flexures in the host stratigraphy and within interpreted pressure shadows around competent units.
Nickel, Thompson, 1D-Deposit