Magmatic evolution of the last 3.6 Ma of volcanic activity in Gran Canaria (Canary Islands, Spain): petrographic and mineral chemistry evidences

New petrographic and mineral chemistry data obtained in 50 samples of the Post-Roque Nublo Group of Gran Canaria (Canary Islands, Spain) are presented. All the samples are well-known from a geochemical point of view and have been accurately studied (Gimeno et al. , 2003; Guillou et al., 2004). The more noteworthy petrographic feature is the presence of zoned clinopyroxene with green core (salitic composition) and brownish rim (diopsidic-salitic composition) in most of the samples. To explain this compositional variation it is suggested that magma mixing played an important role during magmatic evolution. Furthermore fractional crystallisation of basic magmas is needed to obtain most evolved ones. We suggest that crystal fractionation and magma mixing took place in magma reservoirs located at depths of 20 to 27 km and at 10 to 14 km. The proposed magma evolution model also explains the compositional variations within the Post-Roque Nublo Grou