Re-Os systematics of Early Proterozoic ferropicrites, Pechenga Complex, northwestern Russia - Evidence for ancient Os-187-enriched plumes

During crystallization about 1.98 Ga ago, many of the bodies of various ferropicritic flows and sills of the Pechenga Complex, Russia, became highly differentiated. In addition, some of the larger igneous units are associated with major Ni-Cu ore deposits. This work examines the Re-Os isotopic systematics of these flows and sills. The Re-Os systematics of some whole rock samples of both mineralized and sulfide-poor intrusions were affected by post-magmatic events. The metamorphic effects are reflected in the recrystallization of many of the primary sulfides. Consequently, the primary igneous Re-Os systematics of these rocks are examined best by analyzing their magmatic phases such as chromite, olivine, clinopyroxene, and primary sulfides. These analyses are discussed in this paper. (AIAA)