U-Pb zircon SHRIMP data from the Cana Bravalayered complex: new constraints for themafic-ultramafic intrusions of Northern Goiás,Brazil

Abstract

The Cana Brava Complex is the northernmostand least well known layered intrusion of a discontinuousbelt of mafic-ultramafic massifs within the Brasilia Belt,which also comprises theNiquelândia and Barro Alto complexes.Available geochronological data from a range oftechniques (K/Ar, Ar/Ar, Rb/Sr, Sm/Nd and U/Pb) providea range of possible ages (time span from 3.9 Ga to 450 Ma),hence a precise and reliable age for the Cana Brava Complexis still lacking. Also, preliminary isotopic and geochemicaldata of the Cana Brava Complex suggest a significantcrustal contamination, which could have affectedbulk-rock Sr and Nd systematics resulting in meaninglessage determinations. In this paper, we present new U-PbSHRIMP zircon analyses from four samples of differentunits of the Cana Brava Complexwhich suggest that the intrusionoccurred during the Neoproterozoic, between 800and 780 Ma, i.e. at the same age ofNiquelândia. Discordantolder 206Pb/238U ages are provided by inherited zircons,and match the age of the metamorphism of the embeddingPalmeirópolis Sequence.

Keywords

• cana brava
• layered complex
• geochemistry
• zircon
• shrimp