A geochemical study of two peraluminous granites from south-central Iberia: the Nisa-Albuquerque and Jalama batholiths

In this paper we present new petrological and geochemical data for two pera luminous granite batholiths (Nisa Alburquerque and Jalama batholiths) repre sentative of the 'Araya-type' granites of the Central-Iberian Zone. Both gr anites are composite with several facies (monzogranites and leucogranites) that can be grouped into two main granite units: the external units and cen tral units. Intrusive relationships and lack of geochemical coherence betwe en the central and external units indicate that they are not comagmatic bur represent different pulses. The central units of both batholiths are petro logically and geochemically different. On the other hand, external units sh ow a lot of similarities and are the main object of this study. The main ch aracteristics of the external granites can be interpreted in terms of an in complete fractional crystallization process of early mineral phases (plg Kf + bt) which probably took place at the level of emplacement. Other possi ble mechanisms of magmatic differentiation (magma mixing, restite unmixing, sequential melting) can be discarded based on field, petrography and geoch emical data. We propose that the 'Araya-type' granites are formed by the in trusion of distinct magma pulses (central and external). Further evolution within each pulse call be due to incomplete fractional crystallization poss ibly taking place at the emplacement level.