Possible primary upper mantle peridotite in norwegian basal gneiss

Abstract

Garnet peridotites at Ugelvik on the island of Oteroy do not show the extensive mineral and bulk rock chemical variations demonstrated by the previously described garnet peridotites at the nearby Kalskaret and Almklovdalen localities. Instead they show striking mineralogical and chemical similarities to the garnet peridotites which occur as nodules in kimberlite pipes and also to those described from the Czech Massif. In the light of this similarity and their compatibility with likely mantle compositions suggested by the chondrite meteorite and pyrolite models and the likely upper mantle mineralogy indicated by the experimental high pressure and temperature petrology studies, it is postulated that the garnet peridotites from Ugelvik, kimberlite pipes, the Czech Massif and also possibly those from Bellinzona in Switzerland may all be representative of essentially unmodified upper mantle material.