Geology, petrology, U-Pb (shrimp) geochronology of the Morrinhos granite -Paraguá terrane, SW Amazonian craton: implications for the magmatic evolution of the San Ignácio orogeny

Abstract

Morrinhos granite is a batholith body that is slightly elongated in the NNW direction and approximately 1,140 km 2 long; it is located in the municipality of Vila Bela da Santíssima Trindade of the state of Mato Grosso, Brazil, in the Paraguá Terrane, Rondonian-San Ignácio Province, in the SW portion of the Amazonian Craton. This intrusion displays a compositional variation from tonalite to monzogranite, has a medium to coarse inequigranular texture and is locally porphyritic; biotite is the predominant mafic in one of the facies, and hornblende is predominant in the other, with both metamorphosed into the greenschist facies. The studied rocks characterize an intermediate to acidic sequence that was formed by a subalkaline magmatism; the series is alkali-calcic to metaluminous to slightly peraluminous, and the rocks evolved through fractioned crystallization mechanisms. The structural data show two deformation phases represented by penetrative foliation (S 1 ) and open folds (D 2 ), and both phases were most likely related to the San Ignácio Orogeny. The geochronological (U-Pb SHRIMP) and isotopic (Sm-Nd) investigations of these rocks indicated a crystallization age of 1350 ± 12 Ma, T DM of approximately 1.77 Ga and εNd (1.35) with a negative value of -2.57, suggesting that their generation was related to a partial melting process of a Paleoproterozoic (Statherian) continental crust. The results herein indicate that the Morrinhos granite was generated in a continental magmatic arc in a late-to post-orogenic stage of the San Ignácio Orogeny, and it can be recognized as belonging to the Pensamiento Intrusive Suite. KEYWORDS:

Petrogenesis, U-Pb and Sm-Nd geochronology of the Furna Azul Migmatite: partial melting evidence during the San Ignácio Orogeny, Paraguá Terrane, SW Amazon Craton

“…Regarding the metamorphic and magmatic events of the Paraguá Terrane, the data shown point to a correlation between dioritic injections and the Pensamiento Intrusive Suite (Litherland et al 1986, Bettencourt et al 2010, Nalon et al 2013, França et al 2014, probably related to syn-to tardi-kinematic granites of a continental arc during the San Ignácio Orogeny.…”

“…In the area, the basement of the Aguapeí Group is composed by migmatitic gneisses, with some occurrences of granulites with ages ranging from 1711 to 1640 Ma (Figueiredo et al 2013, Matos et al 2013, Faria et al 2014. These rocks crop out as Bettencourt et al (2010) and França et al (2014). mega-xenoliths or as basement windows in the midst of several granitic intrusions from San Ignácio Orogeny (Geraldes et al 2001, Matos et al 2009, Jesus et al 2010, Ruiz et al 2012, Nalon et al 2013, França et al 2014 (Fig.…”

“…These rocks crop out as Bettencourt et al (2010) and França et al (2014). mega-xenoliths or as basement windows in the midst of several granitic intrusions from San Ignácio Orogeny (Geraldes et al 2001, Matos et al 2009, Jesus et al 2010, Ruiz et al 2012, Nalon et al 2013, França et al 2014 (Fig. 2A and Tab.…”

“…The Lomas Manechis Granulite Complex consists of a granite-gneiss suite bearing amphibole and orthopyroxene originated between 1690 and 1660 Ma. Proposed models consider the sequences to be granulitized and migmatized during the San Ignacio Orogeny, and magmatism to have taken place in a magmatic arc setting represented by several orogenic granitoids emplaced around 1300 Ma , Jesus et al 2010, Ruiz et al 2012, Nalon et al 2013, França et al 2014.…”