GEOCHEMISTRY OF GRANITIC-ROCKS AND THEIR MINERALS FROM THE KAVALA PLUTON, NORTHERN GREECE

The Kavala pluton is composed of metaluminous Alpine I-type granitic r ocks. A medium- to coarse-grained porphyritic gneissic granodiorite pr edominates over a coarse-grained granodiorite, but neither mineralogic al nor geochemical distinctions were found between them. Subordinate d iorite, tonalite and monzogranite also crop out. The granodiorites con tain numerous enclaves of diorite and tonalite compositions. Most of t he whole-rock major and trace element variation diagrams indicate frac tionation trends from diorite to monzogranite, but the enclaves fall o utside the trends. However the variation diagrams of Nb of rocks, Zr, Ce, La, Nd, Rb, Rb/K, Ni/Mg of amphiboles, Mn of allanite and Ca and M n of epidote versus 1/3Si + K - (Ca + Mg) in the granitic rocks define a tonalite, granodiorite and monzogranite sequence, showing that dior ite and enclaves plot outside the trends. Least squares analysis of ma jor elements and modelling of trace elements indicate that granodiorit e and monzogranite are probably derived from a tonalite magma by fract ional crystallization of plagioclase, amphibole, biotite and quartz. T he relatively high delta(18)O values and the positive correlation betw een SiO2 and initial Sr-87/Sr-86 suggest that this mechanism was accom panied by crustal contamination. The minerals of these granitic rocks were re-equilibrated during deformation contemporaneous with emplaceme nt and during cooling, but the enclaves were already solidified.