Geochemistry and PGE mineralization of the Kitto intrusion : a product of Mesoproterozoic plume magmatism through fault bounded archean crust, East Nipigon Embayment, Northern Ontario

Abstract

The Kitto intrusion is a Mesoproterozoic 1117.7 ±1.8 Ma peridotitic to gabbroic intrusion, that formed as a result of plume magmatism and was emplaced along Mesoproterozoic and Archean faults in the East Nipigon Embayment of northern Ontario. The plume signature for the Kitto intrusion is suggested by five samples with OIB (ocean island basalt)-like primitive mantle normalized multielement patterns in the lherzolite-olivine websterites. In the southern part of the intrusion, the sequence of lithologies from top to bottom is lherzolite, olivine websterite, vari-textured pyroxenite, pyroxenite and melanogabbro. The basement is banded iron formation and mafic metavolcanic rocks. Lithologies on surface are dominantly lherzolite, with olivine websterite present in the area of the Phoenix mineralized occurrence. The Kitto intrusion is dominated by lherzolite that exhibits cumulate to pyroxene-poikilitic textures dominated by olivine with lesser clinopyroxene and poikilitic orthopyroxene.