Granulite-facies metamorphism at ca. 570-580 Ma in the Porangatu Granulite Complex, central Brazil: implications for the evolution of the Transbrasiliano Lineament

Abstract

ABSTRACT:The Porangatu Granulite Complex is exposed in the central part of the Neoproterozoic Tocantins province in central Brazil, along the boundary between the Brasília Belt to the east and the Araguaia Belt to the west. This is part of the transcontinental Transbrasiliano-Kandi shear system. The complex includes garnet-rich enderbite and charnockite, high-grade gneisses as well as lenses of garnet-bearing mafic granulite or amphibolites, and in situ anatectic charnockite, elongated in the NNE-SSW direction along the Talismã Shear Zone (TSZ). These rocks represent suites of ortho-derived rocks of calc-alkaline affinity and small contributions of tholeiitic basalts and aluminous paragneisses. The structural framework records thrust components probably related to the early stages of an oblique collision during the evolution of Neoproterozoic Brasiliano orogens, and can be understood as involving a collisional system of two crustal blocks, initially with thrust components which in its final stage evolved to a transcurrent system with dextral movement. This led to intense imbrication, generation of mylonitic foliation, stretching lineation, tectonic banding and rotation of structures and minerals. The heterogeneous and progressive ductile deformation was accompanied by metamorphic re-equilibrium in late Neoproterozoic time. Granulite facies conditions reached a metamorphic maximum at temperature and pressure above 850°C and 10 kbar, in an almost anhydrous environment, with or without anatexis. Zircon U-Pb SHRIMP analyses for two selected rock samples indicated the combined age of 580 ± 7 Ma for a charnockite and 548 ± 48 Ma for a mafic granulite from which the charnockite is throught to have been derived. The mafic granulite contains zircon grains of ca. 2.1 Ga, indicating Paleoproterozoic igneous protoliths involved in Neoproterozoic high-grade metamorphism. In addition, older inherited zircon grains of ca.

Blue quartz in Brazil: the Rio dos Remédios occurrence – preliminary study

“…The age of the blue quartz bearing rocks ranges from 2760 ± 11 to 2757 ± 7 Ma, to 580 ± 7 Ma, as determined for the felsic (rhyolitic) volcanic rocks of the Grão Pará Group (Trendall et al, 1998) and the charnockites of the Porangatu Granulite Complex (Gorayeb et al, 2017), respectively. Whether the quartz developed the blue color during the initial crystallization, and therefore the color is the same age as the host rock, or it is the product of subsequent metamorphic events has not yet been determined.…”

“…The rest of the occurrences are related to: 1 -collisional and metamorphic events, such as the 2050 Ma (Rosa et al, 2000) Guanambi Batholith related to the Transamazonian Cycle, the 2760 ± 11 -2757 ± 7 Ma (Trendall et al, 1998) felsic volcanic rocks of the Grão Pará Group (Cristalino IOCG deposit) and the 2128 ± 8 Ma (Mello et al, 2006) Lagoa do Gato quartzfeldspar porphyry of the Grão Pará and Rio Itapicuru Greenstone Belts respectively, the 580 Ma (Gorayeb et al, 2017) Porangatu Granulite Complex charnockites resulted from the Amazon craton collision with the São Francisco -Congo cratons, the charnockites of the Santa Catarina Granulite Complex with a 2720 Ma protolith which underwent granulite facies metamorphic episodes 2680 and 2170 Ma ago (Hartmann et al, 2000), the 2552 Ma (Giustina et al, 2009) Campinorte Sequence metarhyolite of the Brasilia Belt, the 2157 ± 5 Ma (Cid et al, 2000) granite of the Couro de Onça Intrusive Suite related to the Transamazonian Cycle, the Brasiliano/Pan-African 587 ± 8 Ma (Junior et al, 2011) Zimbros Intrusive Suite rhyolite, the ca. 2040 -2060 Ma (Neves et al, 2020) Sucuru granite associated with subduction-collisional events linked to the assembly of the Nuna/Columbia supercontinent, or 2 -within-plate magmatism, as is the case with the 1871 ± 5 Ma (Costi et al, 2009) Abonari granite of the Mapuera Intrusive Suite, Amazon Craton, or the 2006 ± 24 Ma (Sparrenberger & Tassinari, 1999) Riacho dos Cavalos pegmatite of the Granite-Gneiss Complex (Goiás Tin Province).…”

The role of V-shaped oceans and ribbon continents in the Brasiliano/PanAfrican assembly of western Gondwana

“…630–600 Ma 127 , 128 , granulitic magmatism at ca. 570–580 Ma in the northern part of the Tocantins Province 129 and final collision of the Amazonian paleocontinent to the amassed western Gondwana around 540–520 Ma 130 .…”

Wrapping a Craton: A Review of Neoproterozoic Fold Belts Surrounding the São Francisco Craton, Eastern Brazil

“…These reverse faults limit and cut rigid, slightly deformed paleo-mesoproterozoic blocks, showing large open folds, cushioning the impact of the Transbrasiliano system [62,86]. Regional metamorphism increases westward, from the greenschist facies near the cratonic border to the amphibolite and granulite facies to the west in the metamorphic core [42,80,87].…”

“…Later, the continental collisional tectonic evolved to the northern sector, with the collision between the Amazonian and the São Francisco cratons, controlled by NE lineaments and lateral transports (transpressional belt). The collision of the São Francisco and the Amazonian paleoplates took place much later, at around 570-540 Ma [87,88], leading to the development of the North Brasília Belt. The mega inflection of the Pirineus [20] and the overlapping zone may be the result of the interference between two distinct Neoproterozoic belts.…”