The gabbro-wehrlite association in the eastern part of the Baltic Shield.

Abstract

Proterozoic mafic and ultramafic intrusive rocks are widespread in the Archaean Kuhmo greenstone belt, including three minor Ni-Cu deposits. Similar intrusions exist in the Koli area where they are incorporated in the same magmatic association as the Ni-bearing intrusions of Pechenga. The cumulate sequences include olivine, and plagioclase-clinopyroxene-magnetite cumulates. Ti-rich amphibole and mica occur as postcumulus phases in ultramafic rocks. The chemical compositions of the minerals and rocks differ from those of the Pechenga intrusions, reflecting differences in the parent magmas and their fractionation stages. The parent magmas in E Finland and Pechenga correspond with picrites of the Suisaarian and Pechenga types, respectively.-R.E.S.