Petrology and chemistry of basic rocks from the north: central region of the Mantiqueira Province, Brazil

Between the Coastal Belt and the São Francisco Craton basic melts intruded the basement (Fig. 1) related to different tectonic and thermo-tectonic events over geologic time.Available petrological, chemical and radiometric data on the basic rocks from the study area may be divided into the following distinct groups:1. Basie roeks of alkaline affinity associated with ultrabasie rocks of the Espinhaço Supergroup.These roeks are eharaeterized by high values of Ti0 2 and Na 2 0 and low values of ~O .Metamorphism is eommon and foliation is parallel to the regional struetural trend.2. Basie roeks of the southem and southeastem parts of the area (Quadrilátero Ferrffero).These highly metamorphosed roeks oeeur in Arehean greenstone balts; their foliation is parallel to the regional trend.3. Alkaline basie roeks (gabbros and basalts) with high contents of Na 2 0 , ~O , Ti02' P 205 and BaO, exhibiting alkaline to calca1ka1ine differentiation trends.They are localized in the Coastal Mobile Belt and in the outeropping parts of the Parafba do Sul Complex (HORN, 1986; WIEDEMANN et ai., 1986).4. Basic roeks in the undifferentiated basement between the Coastal Mobile Belt and the Espinhaço range (CORREIA NEVES & HORN, 1988), can be subdivided in to at least three subgroups: a. Tholelltlc basie roeks with foliation and metasomatie alteration (oIdest group).