Petrologia e geocronologia (U/Pb-Sm/Nd) do Granito Passagem, Complexo Granitóide Pensamiento, SW do Cráton Amazônico (MT)

Abstract

Resumo O granito Passagem compreende stocks, plugs e diques localizados na Serra de Ricardo Franco -município de Vila Bela da Santíssima Trindade -Mato Grosso, pertencentes ao Terreno Paraguá, SW do cráton Amazônico. Constitui-se de monzo a sienogranitos e, mais raramente granodioritos, isotrópicos, leucocráticos de cor cinza-escuro até branco e textura preferencialmente equigranular hipidiomórfica a inequigranular xenomórfica, fina a média, tendo biotita como único mineral máfico primário essencial. Essas rochas caracterizam uma seqüência áci-da pouco expandida formada por um magmatismo sub-alcalino do tipo cálcio-alcalino de alto potássio, levemente peraluminoso, gerado em ambiente de arco magmático provavelmente em época pós-colisional. Mecanismo de cristalização fracionada de plagioclásio, biotita, titanita, apatita e zircão associado à concomitante assimilação crustal são sugeridos para a evolução dessas rochas. Os resultados aqui obtidos reforçam a hipótese de um magmatismo pós-colisional no Terreno Paraguá com idade de 1284 ± 20 Ma correspondendo à cristalização do Granito Passagem e permite reconhecê-lo como prolongamento, em terreno brasileiro, do Complexo granitóide Pensamiento. It consists of isotropic monzogranite, sienogranite and more rarely granodiorites with leucocratic dark gray to white color. These rocks range from hypidomorphic inequigranular to xenomorphic texture, fine to medium grained. Biotite is the only primary mafic present as essential phase and characterize an expanded slightly acid sequence formed by a sub-alkaline magmatism of high-potassium calc-alkaline, slightly peraluminous composition from arc magmatic tectonic environment during a post-collisional period. Mechanism of fractional crystallization of plagioclase, biotite, titanite, apatite and zircon associated with simultaneous crustal assimilation are suggested for the evolution of these rocks. The results support the hypothesis of a post-collisional magmatism in the Paraguá terrane at 1284 ± 20 Ma corresponding to the crystallization age of the Passagem granite. This paper propose that Passagem Granite represents as an extension in Brazilian terrane of the Pensamiento Granitoid Complex. Palavras-chave:

Geology and petrology of the Salto do Céu Suite: tectonic and stratigraphic implications on the SW Amazonian Craton

“…A maximum deposition age of 1.3 Ga on detrital zircons is attributed to it according to Leite & Saes (2003; bottom of Aguapeí Group in São Vicente and Lavrinha hills) and Geraldes et al (2014;Fortuna Formation in Ricardo Franco and Santa Barbara hills). The younger basement rocks of this group in the surrounding region are the post-kinematic granites of the Pensamiento Suite dated at 1290 Ma by U-Pb (LA-IPC-MS) (Jesus et al 2010). Geraldes et al (2014) report a maximum deposition age around 1540 Ma (U-Pb, LA-ICP-MS) for this group in the Rio Branco Hill, which supports the notion that it is a different sedimentary cover, likely another stratigraphic unit deposited in the Calymmian once the younger rocks of the underlying basement consist of post-kinematic granites of the Alvorada Suite dated around 1440 Ma by U-Pb (TIMS) on zircon (Geraldes et al 2001, Ruiz 2005.…”

Widespread ca. 1.4 Ga intraplate magmatism and tectonics in a growing Amazonia

“…In a similar manner, in the Bolivian counterpart, the San Ignacio orogeny (1.35^0.2 Ga) largely remobilized the Paraguá terrane by means of deformation, high-grade metamorphism and emplacement of collisional-type granitic plutons -the Pensamiento Granitoid Complex (e.g. Litherland et al 1986;Boger et al 2005;Santos et al 2008;Matos et al 2009;Jesus et al 2010;Nalon et al 2013;Franc a et al 2014). All the abovementioned highlight the final stage of the RSI composite orogeny given by juxtaposition of the Paraguá terrane to the Table 1.…”

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

“…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.…”