Shrimp and conventional U-Pb age, Sm-Nd isotopic characteristics and tectonic significance of the K-rich Itapuranga suite in Goiás, Central Brazil

Márcio M Pimentel,Reinhardt A Fuck,Richard A Armstrong,Elton L Dantas

doi:10.1590/s0001-37652003000100011

Márcio M Pimentel, Reinhardt A Fuck + Show 2 more

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https://doi.org/10.1590/s0001-37652003000100011

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Abstract

The Itapuranga alkali granite and Uruana quartz syenite are large K-rich EW-elongated intrusions, in the central part of the Neoproterozoic Brasília Belt, central Brazil. They are associated with Pireneus lineaments, which cut the regional NNW-SSE structures of the southern part of the belt. SHRIMP and conventional U-Pb data for the Itapuranga and Uruana intrusions indicate crystallization ages of 624 ± 10 Ma and 618 ± 4 Ma, respectively. Three zircon cores from the Itapuranga granite yielded U-Pb ages between 1.79 and 1.49 Ga. Sm-Nd T DM ages for both intrusions are 1.44 Ga and epsilonNd(T) values are -5.1 and -5.7, suggesting the input of material derived from older (Paleo- to Mesoproterozoic) sialic crust in the origin of the parental magmas. Magma mixing structures indicate co-existence of mafic and felsic end-members. The felsic end-member of the intrusions is dominantly represented by crust-derived melts, formed in response to the invasion of Paleo/Mesoproterozoic sialic crust by alkali-rich mafic magmas at ca. 620 Ma. These intrusions are roughly contemporaneous with, or perhaps slightly younger than, the peak of regional metamorphism in the southern Brasília Belt. Their emplacement along the Pireneus lineament suggest a syn-tectonic origin for them, most probably in transtensional settings along these faults.

Highlights

The Brasília Belt is part of a large Neoproterozoic (Brasiliano/Pan African) orogen developed between the Amazon and São Francisco cratons in central Brazil (Figure 1)
The Almas-Conceição do Tocantins Paleoproterozoic Block (Figure 1) is interpreted as an extension of the sialic terrains exposed within the northwestern part of the São Francisco Craton and represents, an autochthonous exposure of the sialic basement of the Brasília Belt sediments
In this paper we present new conventional and SHRIMP U-Pb data, as well as Sm-Nd isotopic results for these rocks, and discuss their significance in relation to the timing of development of the EW faults associated with the Pireneus Syntaxis

Summary

Introduction

The Brasília Belt is part of a large Neoproterozoic (Brasiliano/Pan African) orogen developed between the Amazon and São Francisco cratons in central Brazil (Figure 1). 780-760 Ma in the northern mafic granulites (Ferreira Filho et al 1994, Correia et al 1997, Pimentel et al 2001), and at ca. The peak of metamorphism at the end of the Neoproterozoic was shortly followed by, or was concomitant with uplift, erosion and extensive mafic magmatism, especially in the western and central parts of the belt (Pimentel et al 1996, Hollanda et al 2002)

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