Picrite sills and crystal-melt reactions in the Honningsvag Intrusive Suite, northern Norway

Field relations in the upper part of Intrusion II of the Caledonian Honningsvag Intrusive Suite show that some peridotite sheets transgress, and include in situ rafts of, the adjacent gabbroic cumulates. Modal and textural analyses of three olivine melagabbro sheets show non-cotectic mineral proportions that are likely to result from crystal-melt reactions. Discordant, replacive fingers and pipes of feldspathic peridotite along interfaces between peridotite and overlying olivine melagabbro also suggest crystal-melt reactions. It is proposed that several picritic sills intruded porous gabbroic cumulates in the upper part of Intrusion II. Lateral infiltration of picritic magma led to crystal-melt reactions, mainly assimilation of plagioclase and precipitation of olivine, resulting in the formation of olivine melagabbro and peridotite sheets, and replacive fingers and pipes of feldspathic peridotite.