Typology and petrographic characteristics of Birimian granitoids at the chilled margins of doleritic dykes in the Téra-Ayorou pluton (Liptako, Western Niger)

The doleritic dykes intersecting the granitoids of Ayorou and Kandadji sectors belong to the Birimian domain of the Léo-Man shield (West African Craton). These rocks have been the subject of several studies, but these works have not interested on their characteristics at the contact area with the doleritic dykes. The aim of this work is to determine the typology and petrographic characteristics of the Liptako granitoids at the chilled margins of the doleritic dykes in the Ayorou and Kandadji sectors. The methodology conducted consists of sampling and laboratory works. The typology of granitoids in boths sectors consists of locally porphyritic or foliated granodiorites, locally migmatitic or two-mica biotite granite, microdiorite and porphyritic diorites. They have been intersected by quartzo-feldspathic, pegmatitic, aplitic, doleritic veins, and the development of leucosomes and melanosomes at the chilled margins of thick dykes (40-60 m). The foliated granodiorite and two-mica granite are characterized by hydrothermal alteration or low-grade post magmatic metamorphism process; corresponding to hornblende and biotite chloritization and plagioclase sericitization. The relationship between granitoids and the doleritic dykes at their chilled margins is traduced by slightly increase in metamorphic structures and alteration minerals and decrease of crystals size, linked to the emplacement of the doleritic dykes