The island of Oldra, part of the Late Ordovician Solund-Stavfjord Ophiolite Complex of the western Norwegian Caledonides, comprises extrusive rocks, a sheeted dyke complex and high-level gabbros. The metabasalts are of N-MORB affinity, and their Nd isotopic composition (?_Nd=+ 7.8 to +8.4) indicates generation from a relatively homogeneous, bul strongly depleted mantle. Eighty percent of the metabasalts classify as FeTi-basalts (FeO^t/MgO >1. 75, TiO₂ > 2 wt% ), but pseudostratigraphically their distribution varies significantly (51% of the extrusive rocks and 92% of the sheeted dykes). The contents of FeO^t, MgO, Al₂O₃, Cr, Ni and Zr indicate that differences in depth of melting (30 to 12 kbar), crystal fractionation of olivine, plagioclase and clinopyroxene at different levels in the mantle and crust (

Hanne Lone Ryttvad, Norsk Hydro ASA, Sandslivn. 90, N0-5049 Bergen, Norway;
Harald Furnes, Geologisk Institutt, Allégt. 41, NO-5007 Bergen, Norway (e-mail. This email address is being protected from spambots. You need JavaScript enabled to view it.);
Kjell Petter Skjerlie, Institutt for Geologi, N0-9037 Tromsø, Norway;
Rinn Rolfsen, Esso Norge AS, Grensevn. 6, N0-4313 Sandnes, Norway