The Rio Apa Craton in Mato Grosso do Sul (Brazil) and northern Paraguay: Geochronological evolution, correlations and tectonic implications for Rodinia and Gondwana

Abstract

The Rio Apa cratonic fragment crops out in Mato Grosso do Sul State of Brazil and in northeastern Paraguay. It comprises Paleo-Mesoproterozoic medium grade metamorphic rocks, intruded by granitic rocks, and is covered by the Neoproterozoic deposits of the Corumbá and Itapocumi Groups. Eastward it is bound by the southern portion of the Paraguay belt. In this work, more than 100 isotopic determinations, including U-Pb SHRIMP zircon ages, Rb-Sr and Sm-Nd whole-rock determinations, as well as K-Ar and Ar-Ar mineral ages, were reassessed in order to obtain a complete picture of its regional geological history.The tectonic evolution of the Rio Apa Craton starts with the formation of a series of magmatic arc complexes. The oldest U-Pb SHRIMP zircon age comes from a banded gneiss collected in the northern part of the region, with an age of 1950 ؎ 23 Ma. The large granitic intrusion of the Alumiador Batholith yielded a U-Pb zircon age of 1839 ؎ 33 Ma, and from the southeastern part of the area two orthogneisses gave zircon U-Pb ages of 1774 ؎ 26 Ma and 1721 ؎ 25 Ma. These may be coeval with the Alto Tererê metamorphic rocks of the northeastern corner, intruded in their turn by the Baía das Garças granitic rocks, one of them yielding a zircon U-Pb age of 1754 ؎ 49 Ma. The original magmatic protoliths of these rocks involved some crustal component, as indicated by the Sm-Nd T DM model ages, between 1.9 and 2.5 Ga. Regional Sr isotopic homogenization, associated with tectonic deformation and medium-grade metamorphism occurred at approximately 1670 Ma, as suggested by Rb-Sr whole rock reference isochrons. Finally, at 1300 Ma ago, the Ar work indicates that the Rio Apa Craton was affected by widespread regional heating, when the temperature probably exceeded 350°C.Geographic distribution, age and isotopic signature of the lithotectonic units suggest the existence of a major suture separating two different tectonic domains, juxtaposed at about 1670 Ma. From that time on, the unified Rio Apa continental block behaved as one coherent and stable tectonic unit. It correlates well with the SW corner of the Amazonian Craton, where the medium-grade rocks of the Juruena-Rio Negro tectonic province, with ages between 1600 and 1780 Ma, were reworked at about 1300 Ma. Looking at the largest scale, the Rio Apa Craton is probably attached to the larger Amazonian Craton, and the actual configuration of southwestern South America is possibly due to a complex arrangement of allochthonous blocks such as the Arequipa, Antofalla and Pampia, with different sizes, that may have originated as disrupted parts of either Laurentia or Amazonia, and were trapped during later collisions of these continental masses.

Petrogenesis and U-Pb and Sm-Nd geochronology of the Taquaral granite: record of an orosirian continental magmatic arc in the region of Corumba - MS

“…Therefore we suggest a correlation between the Taquaral Granite and Alumiador Intrusive Suite (Rio Apa Terrane) once there display petrographic, compositional and age similarities between the Alumiador (Cordani et al 2010), despite their distinct T DM model ages which suggest distinct crustal sources. Regarding the tectonic settings, the Taquaral Granite constitutes an intrusion related to convergent plate boundaries, continental magmatic arc, generated from magma-crust interaction.…”

“…The first one describes this Terrane as an allochthonous crustal fragment geographically separated from the Amazon Craton by the Tucavaca Belt (Barros et al 1982, Del'Arco et al 1982, Litherland et al 1986, Alvarenga & Saes 1992, Brito Neves et al 1995, Trompette et al 1998, Tassinari & Macambira 1999, 2004, Santos et al 2000, Bettencourt et al 2010. The second proposal, by Ruiz et al (2005), Lacerda Filho et al (2006) and Cordani et al (2010), takes into consideration the previous proposal of Almeida (1967) and Amaral (1974), in which the Rio Apa Terrane is described as a prolongation of the Amazon Craton and the basement of Neoproterozoic mobile belts. This work adopted the second proposal thus considering the Rio Apa Terrane as a southern portion of the Amazon Craton (Fig.…”

“…Cordani et al (2010) presented Ar-Ar and K-Ar data around 1,300 Ma for the volcanic rocks from Serra da Bocaina and plutonic rocks from Alumiador Intrusive Suite. Theses authors presented a U-Pb zircon age of 1,839 ± 33 Ma and Nd T DM model ages between 2.54 and 2.49 Ga. Litherland and Klink (1982) and posteriorly called San Pablo by Saes and Leite (1993), Saes andFragoso Cesar (1994, 1996) and Saes (1999).…”

“…Several papers have shown the occurrence of Orosirian magmatism over an extensive area in southern Amazon Craton being recognized in the Rio Apa Terrane by Correia Filho et al (1981), Araújo et al (1982), Godoi et al (2001), Lacerda Filho et al (2006), Cordani et al (2010), Brittes et al (2013) and Plens et al (2013). Vargas-Mattos (2010) also describe the occurrence of Orosirian calc-alkaline granitoids in the San Pablo Terrane in Bolivia.…”

Geoquímica, dataciones U-Pb SHRIMP sobre circón e isótopos de Hf del magmatismo gondwánico en el NW de Argentina: petrogénesis e implicancias geodinámicas.

“…The recorded evidence of Early Mesoproterozoic crust in its southern extension could provide additional evidence for its connection to the Maz and Río Apa blocks, constituting together the hypothetical MARA craton, following the model proposed by Casquet et al (2009Casquet et al ( , 2010. The 1.24 to 1.36 Ga crustal ages obtained are coincident with the Andean-type magmatic arc recorded from the Maz terrane at 1.26 to 1.33 Ga (Casquet et al, 2011 and references therein), as well as to the thermal episode at 1.3 Ga that affected the Río Apa block (Cordani et al, 2010), pointing to a common history for the three areas at least during the Mesoproterozoic.…”