Picrite Sills and Crystal-Melt Reactions in the Honningsvåg Intrusive Suite, Northern Norway

Christian Tegner and Brian Robins
Danish Lithosphere Centre, Øster Voldgade 10, 1350 København K, Denmark
Department of Geology, University of Bergen, 5007 Bergen, Norway

Abstract: Field relations in the upper part of Intrusion II of the Caledonian Honningsvåg 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.

Keywords: crystal-melt reactions • picrite • cumulates • sills • Honningsvåg • Norway

Mineralogical Magazine; February 1996 v. 60; no. 398; p. 53-66; DOI: 10.1180/minmag.1996.060.398.05
© 1996, The Mineralogical Society
Mineralogical Society (www.minersoc.org)