GEOCHEMISTRY OF MIOCENE GRANITOIDS FROM B EJAIA-AMIZOUR (NORTHERN ALGERIA)

The Bejaia-Amizour volcanoplutonic complex includes seven zoned pluton ic bodies intruding the Cretaceous and Tertiary flysch nappes of the n orthern Algerian margin. They range in composition from diorites to gr anodiorites, quartz-monzonites and granites. They display K-rich calc- alkaline petrographic and chemical characteristics, and have been affe cted by late- to post-magmatic hydrothermal alteration processes follo wing their crystallization under low total pressures. The study of the ir trace element compositions suggests their derivation from a basalti c parent magma through combined crystal fractionation, magma mixing an d crustal contamination processes. However, the lack of correlation be tween SiO2 contents, Sr-87/Sr-86, Nd-143/Nd-144, deltaO-18 ratios and Rb/Nb, Ba/Nb, La/Nb ratios indicates that crustal contamination couple d with differentiation occurred within small individual magma chambers . This process is not chiefly responsible for their calc-alkaline trac e element fingerprints, e.g. negative Nb anomalies with respect to nei ghbouring incompatible elements.