Geochemical and Sm-Nd isotopic study of Paleoproterozoic basaltic and gabbroic rocks of the Hurwitz Group, Kaminak Lake area, Kivalliq region Northwest Territories

Abstract

Basaltic and gabbroic rocks of the Ameto Formation comprise part of the Paleoproterozoic Hurwitz Group and are considered to be 2111 Ma, based on their correlation with Hurwitz Group gabbros southwest of the study area. Volcanic rocks are locally pillowed and are interlayered with mudstone, siltstone, and diamictite, all cut by gabbroic sills. Igneous rocks preserve variably developed foliations and a low-grade metamorphic mineral assemblage implying deformation and metamorphism at greenschist facies. Major-, trace-, and rare-earth-element geochemical data demonstrate a homogeneous suite of tholeiitic basalts with affinities to both continental and volcanic-arc tholeiites. The gabbroic rocks are intrusive equivalents of the basalts. Values of eNd(2.111 Ga) range from -0.54 to +0.25 and yield TDM ages of 2598 to 2508 Ma. The combined data suggest that parental magmas were at least in part derived from a metasomatically enriched mantle source and that metasomatism occurred immediately after accretion of the Neoarchean Kaminak greenstone belt.