Prelude a une typologie des massifs granitiques

Abstract Based on their chemical and chronologic characteristics the granitic rocks of massifs are classified in two groups: syntectonic and late tectonic granites of the first phase; and extensively fractured, with coal deposition and later mineralization of the second phase. A structural analysis of the Meymac region (central French massif) is used as an example as it represents a granitic pluton, with continuous evolution resulting in a zonal distribution of the minerals and formations. The typological determination of granitic massifs requires specifically defined terminology, and metalliferous deposits must be differentiated. Examination of the granitic facies reveals four types of massifs: massifs with porphyritic granite associated with medium-grained non-porphyritic granite; massifs with porphyritic granite containing fine-grained granite bodies; massifs of coarse-grained, non-porphyritic granite; and massifs of varied facies disposed in an irregular manner. Typology seems to be a possible beginning in the study of the dynamics of deepseated petrogenesis.