As rochas básicas intrusivas das suítes Rio Branco e Salto do Céu, na região de Rio Branco (MT) sudoeste do Cráton Amazônico

Abstract

The basic magmatism is located in the southwestern portion of the Amazonian Craton (MT) belonging to the Cachoeirinha Tectonic Domain and redefined into two independent basic events. Mesoproterozoic mafic dikes named Rio Branco Intrusive Basic Suite are constituted by microgabbros to quartz microgabbros and microdiorites to quartz microdiorites, showing discontinuous distributions and localized mostly on the border of the acid to intermediate rocks of the batholiths. Neoproterozoic mafic sills and dikes (± 808 Ma) are grouped into the Salto do Ceu Basic Suite and constituted by diabase and microgabbros associated to the Aguapei Group strata. Rio Branco magmatism is constituted from two distinct magmas of basic and acid composition and represents a post-orogenic to anorogenic magmatic event of transition between I and A types and environment representing late intrusions in the magmatic cicle, related to the end of the collisional event of Cachoeirinha Orogeny. The Rio Branco Intrusive Basic Suite is of alkaline basalts generated in an intraplate. The Salto do Ceu Intrusive Basic Suite magmatism distributes along the field of alkaline basalts and formed into intraplate environment and characterizes an extensional event probably related to mechanisms of orogenic collapse in the Sunsas-Aguapei Orogenic Belt.