Géothermométrie par les pyroxènes et mise en place du massif anorthositique d'Egersund-Ogna (Rogaland, Norvège méridionale)

Microprobe analyses are presented of 62 orthopyroxene-clinopyroxene pairs from 17 samples from the Egersund-Ogna anorthositic body. Equilibrium temperatures, calculated by various opx-cpx geothermometers (Wood and Banno, 1973; Wells, 1977), as well as the Al-contents of the pyroxenes show relative variations. The interpretation is consistent with the crystallization of the anorthosite along a PT gradient and the syn-emplacement deformation of the mass itself together with its envelope.