Mineralogical constraints оn the petrogenesis of the Pangeon granitoids (Central Macedonia, northern Greece)

Abstract

The Pangeon granitoids intrude the metamorphic rocks of the Lower Tectonic Unit of the Rhodope Massif and are discriminated into two petrographic types: A medium- to coarse-grained, porphyritic, hornblende+biotite tonalite to granodiorite (PTG) and a fine- to medium-grained, biotite±muscovite, granodiorite to granite (MGG). Microgranular mafic enclaves (MME) of monzodioritic composition are present in the PTG rocks. The hornblendes are characterized as hastingsite, magnesiohastingsite and edenite. The biotites show calc-alkaline rock series characteristics (MME and PTG) or calc-alkaline to peraluminous characteristics (MGG). Muscovites are distinguished in primary, late magmatic and secondary (sericite) on the basis of their textural and chemical criteria. Textural evidence and compositional variations of the minerals support mainly a fractional crystallization rather than a restite unmixing or magma mixing process for the evolution within each one rock type of the Pangeon granitoids while they rule out a genetic relation between MME, PTG and MGG through fractional crystallization. Crystallization pressure values obtained by AI-in-hornblende for the PTG along with the presence of magmatic epidote suggest a magma emplacement at mid-crustal depths. Textural and mineralogical data of MME suggest that they were incorporated into their host as solids during the emplacement of the granitoids.