Petrogenesis of Early Permian olivine-bearing cumulates and associated basalt dykes from Bocca di Tenda (Northern Corsica): Implications for post-collisional Variscan evolution

The Early Permian gabbroic sequence of Bocca di Tenda (Northem Corsica) intrudes a plutonic suite made of hornblende-granitoids and is crosscut by basalt dykes with chilled margins. The gabbroic sequence includes olivine-gabbronorite cumulates that consist mainly of euhedral olivine (Fo78-72) and plagioclase (An68-61), and poikilitic clinopyroxene (Mg#=0.85-0.80), orthopyroxene and Ti-pargasite. Pyroxenes from the olivine-gabbronorites have delta(18)O values of +6.3 parts per thousand to +6.7 parts per thousand, which are evidence for the involvement of a crustal component in the petrogenesis of these rocks. The basalts have Mg# values of 57 to 53 and chondrite-normalised patterns characterised by a steady decrease from LREE to HREE. Relative to modern N-MORB. they show also moderate enrichment of Nb and Ta over Zr and Hf, which are in turn slightly enriched over Y and HREF The olivine-gabbronorites and basalts show overlapping Nd isotopic compositions (initial epsilon(Nd) of +2.4 to +1.4 and of +3.0 to +1.5, respectively) and have clinopyroxenes with nearly parallel incompatible trace element patterns, thus revealing that these two rock types formed by melts with similar compositions. Most likely, the primary melts of Bocca di Tenda gabbroic sequence were slightly enriched in most incompatible elements and Nd isotopic compositions relative to modem N-MORB. (C) 2008 Elsevier B.V. All rights reserved.