Petrography, geochemistry and Sm-Nd isotopes of the granites from eastern of the Tapajós Domain, Pará state

Moacir José Buenano Macambira,Flávio Robson Dias Semblano,Marcelo Lacerda Vasquez

doi:10.1590/2317-4889201620160059

Abstract

ABSTRACT: The Tapajós Domain, located in the southern portion of the Amazonian Craton, is a tectonic domain of the Tapajós-Parima Province, a Paleoproterozoic orogenic belt adjacent to a reworked Archean crust, the Central Amazonian Province. This domain has been interpreted as the product of an assemblage of successive magmatic arcs followed by post-orogenic A-type magmatism formed ca. 1880 Ma-old granites of the Maloquinha Intrusive Suite. The study presented here was carried out in four granitic bodies of this suite (Igarapé Tabuleiro, Dalpaiz, Mamoal and Serra Alta) from the eastern part of the Tapajós Domain, as well as an I-type granite (Igarapé Salustiano) related to the Parauari Intrusive Suite. The A-type granites are syenogranites and monzogranites, and alkali feldspar granites and quartz syenites occur subordinately. These rocks are ferroan, alkalic-calcic to alkalic and dominantly peraluminous, with negative anomalies of Ba, Sr, P and Ti and high rare earth elements (REE) contents with pronounced negative Eu anomaly. This set of features is typical of A-type granites. The Igarapé Salustiano granite encompasses monzogranites and quartz monzonites, which are magnesian, calcic to calc-alkalic, high-K and mainly metaluminous, with high Ba and Sr contents and depleted pattern in high field strength elements (HFSE) and heavy rare earth elements (HREE), characteristic of I-type granites. The source of magma of these A-type granites is similar to post-collisional granites, while the I-type granite keeps syn-collisional signature. Most of the studied granites have εNd (-3.85 to -0.76) and Nd TDM model ages (2.22 to 2.46 Ga) compatible with the Paleoproterozoic crust of the Tapajós Domain. We conclude that the Archean crust source (εNd of -5.01 and Nd TDM of 2.6 Ga) was local for these A-type granites.

Highlights

As well as other terrains of the Amazonian Craton, the Tapajós Domain hosts meaningful Paleoproterozoic granitoids related to formation of the Tapajós-Parima province (Fig. 1) (Santos et al 2000; 2004)
The Dalpaiz, Mamoal, Igarapé Tabuleiro and Serra Alta plutons belonging to the Maloquinha Intrusive Suite (MIS) have a high content of SiO2 (69.1-77.1%), and the Igarapé Salustiano granite, belonging to Parauari Intrusive Suite (PIS), has uniform composition in two of the three analyzed samples with SiO2 between 74.2 and 76.7% and a sample (MV-116) with lower value (67.1%)
In K2O vs. SiO2 diagram (Fig. 5A) MIS samples fell into high-K and shoshonite fields, and the PIS samples plotted as high- to medium-K, indicating that the PIS has Na2O content higher than K2O compared to its high alkalis content

Summary

Introduction

As well as other terrains of the Amazonian Craton, the Tapajós Domain hosts meaningful Paleoproterozoic granitoids related to formation of the Tapajós-Parima province (Fig. 1) (Santos et al 2000; 2004). In this context the Maloquinha Intrusive Suite (MIS) is included. Several similar plutons have been mapped, and Andrade et al (1978) proposed the name Maloquinha Intrusive Suite for these granitic plutons These granites are characterized by an alkaline affinity (A-type), typical of intracontinental or post-collisional environments. MIS appears to postdate the Tropas Orogeny (Santos et al 2004), which originated the Parauari Intrusive Suite (PIS) rocks

Results

Discussion

Conclusion