par Wilmart, Edith;Demaiffe, Daniel ;Duchesne, Jean-Clair
Référence Economic geology and the bulletin of the Society of Economic Geologists, 84, 5, page (1047-1056)
Publication Publié, 1989
Article révisé par les pairs
Résumé : The ilmenite norite of the deposit is connected to a main dike which varies in composition from monzonorite to quartz mangerite. Fine-grained satellite dikes also occur in the vicinity of the main dike. A number of rock samples have been analyzed for 36 major and trace elements. An Rb-Sr whole-rock isochron gives an age of 930 Ma. Initial Sr isotope compositions of the ilmenite norite, the main dike, and the satellite dikes are 0.7050, 0.7069, and 0.7100, respectively, thus precluding a comagmatic origin without invoking contamination. The evolution of the main dike can be accounted for by a closed-system fractional crystallization of a monzonoritic magma. The satellite dikes represent undifferentiated monzonorites. The orebody is interpreted as a noritic cumulate which was enriched in dense, oxide-rich magma before being emplaced as a crystal mush. The main-dike illustrates the process by which a quartz mangerite can derive from a monzonoritic magma, and gives support to a comagmatic origin of charnockitic and monzonoritic rocks. -from Authors