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The Archean-Paleoproterozoic terrane of central Brazil is an exotic and allochthonous part of the Tocantins Province, a large Brasiliano/Pan-African orogen of the South American Platform formed during the Brasiliano orogeny. The terrane amalgamated to the province during the late stages of the orogeny as a crustal segment consisting of six Archean orthogneiss complexes and five low-grade metamorphic, in part Paleoproterozoic (Rhyacian) greenstone belts. The Uvá complex is the southernmost orthogneiss association of the Archean-Paleoproterozoic terrane of central Brazil. New U–Pb LA-ICP-MS data from zircon crystals show that the complex formed at least during two magmatic stages. The older consists of polydeformed tonalite and granodiorite batholitic and diorite stock protoliths with igneous age of 3040 Ma to 2930 Ma. The youngest comprises tonalite, monzogranite and granodiorite tabular bodies formed between 2876 and 2846 Ma. As compared to the orthogneisses of the northern portion of the terrane, both the oldest and youngest granitogenesis stages of the Uvá complex are, in average, about 150 Ma older. This suggests that the northern and southern orthogneisses formed during different times as independent crustal segments, but when and why they amalgamated is still under investigation. [ABSTRACT FROM AUTHOR]

Abstract: The Serrinha magmatic suite (Mineiro belt) crops out in the southern edge of the São Francisco craton, comprising the Brito quartz-diorite, Brumado de Cima and Brumado de Baixo granodiorites, granophyres and felsic sub-volcanic and volcanic rocks, part of which intruded into the Nazareno greenstone belt. The suite rocks have petrographic features that are consistent with magma supercooling due to the low water content combined with volatile loss, leading to crystallization of quartz and alkaline feldspar at the rims of plagioclase phenocrysts (granophyric intergrowth). The investigated rocks are sub-alkaline, calc-alkaline and show low content in rare earth elements. The U–Pb zircon crystallization ages for the Brumado de Cima granodiorite [2227±22 (23) Ma] and a coeval granophyre [2211±22 (23) Ma], coupled with available single-zircon Pb evaporation ages for the Brito and Brumado de Baixo plutons, are significantly older than the “Minas orogeny” (ca. 2100–2050Ga) of Quadrilátero Ferrífero area, eastward from the Serrinha suite. Our data establish an early Rhyacian event tectonically linked with the evolution of the Mineiro belt. The bulk Nd isotopic signature [low negative to positive ε Nd( t ) values] of the Serrinha samples are consistent with the important role of Paleoproterozoic mantle components in the magma genesis. The integrated geologic, geochemical and isotopic information suggests that Paleoproterozoic evolution of the Mineiro belt initiated in a passive continental margin basin with deposition of the Minas Supergroup at ca. 2500Ma. This stage was succeeded by outboard rupture of the oceanic lithosphere with development and coalescence of progressively younger magmatic arcs during Rhyacian time. One of the earliest arcs formed the Serrinha suite. The tectonic collage of the Serrinha and Ritápolis (2190–2120Ma) arcs produced the NE–SW Lenheiro shear zone, resulting in mylonitization and recrystallization of both the granitoid intrusions and host rocks. As a matter of fact juxtaposition of distinct magmatic units in age and origin took place along the Lenheiros structure in this sector of the Mineiro belt. [Copyright &y& Elsevier]

The Quadrilátero Ferrífero (QF) is an important, polydeformed mineral province, located in the southernmost portion of São Francisco Craton. The Rio das Velhas greenstone belt (RVGB) is an Archean meta-volcano-sedimentary succession from the QF, the Córrego do Sítio unit (CdS) being its most widely distributed sedimentary sequence. Detailed sedimentology study allied to x-ray diffraction-XRD and geochronological (LA-ICP-MS in detrital zircon) analyses provide evidence for a new interpretation of the CdS. The identified sedimentary structures of the CdS (e.g. flaser and lenticular bedding, sharp and erosional base, normal grading, mud drapes, quartz granules, syndepositional deformation, and ball & pillow) led the interpretation of these couplets as turbidity currents deposits corresponding to TA and TE facies of the classic Bouma Sequence. The CdS sequence was deposited on distal portions of an ancient submarine fan environment by turbidity current mechanisms, then it was partially reworked by tidal bottom currents. Geochronological data pointed out the main influence of the Rio das Velhas II magmatic event in the deposition of the eastern QF metasedimentary sequence, as evidenced by the maximum depositional age at 2818 ± 31 Ma. The surrounding metamorphic complexes terrains may have acted as source areas during the deposition of the sedimentary sequences, probably in a convergent to a collisional marginal tectonic setting (subduction stage). • Córrego do Sitio unit sedimentary sequences interpreted as turbiditity currents partially influenced by tidal bottom currents. • Eastern Rio das Velhas greenstone belt metagraywacke maximum depositional age at 2818 ± 31 Ma. • Sedimentary provenance from surrounding Archean metamorphic complexes. [ABSTRACT FROM AUTHOR]

The Serra das Pipocas Greenstone Belt is one of the rare Paleoproterozoic greenstone belts within the Borborema Province. It is on the west border of the Archean/Paleoproterozoic Nucleus (Cruzeta and Mombaça Complex) of the Ceará Central Domain, northern portion of the Borborema Province. The Serra das Pipocas Greenstone Belt has an elongated sigmoidal shape encompassing about 1000 km2 of the Ceará Central Domain. It consists of a metavolcanosedimentary sequence formed by metasedimentary psammitic-pelitic-marly rocks and interleaved metaultramafic and metamafic rocks, represented by chlorite-anthophyllite-actinolite/tremolite schists and amphibolites. Layers of metatuffs, metabasic, meta-acid sills (metadacites), metacherts, gondites and banded iron formations occur within the metamafic rocks. Actinolite, metagabbro, metadiorite bodies, metabasic dike, Neoproterozoic metagranodiorites and leucogranites crosscut the metavolcanosedimentary sequence. Close to the borders of metagranodioritic bodies (zircon U–Pb 2181 ± 4.4 Ma), the metavolcanosedimentary sequence is hydrothermally altered. The metaultramafic rock (chlorite-anthophyllite-actinolite/tremolite schist) contains high MgO (>18 wt%), low alkali (≤1 wt%) and TiO 2 (<0.8 wt%) and Al 2 O 3 /TiO 2 ratios between 9.94 and 27.26, with a mean value of 17.13. Values of (Gd/Yb) N vary between 1.00 and 1.88, which attest affiliation with komatiite protoliths, between the Munro and Barberton types. The amphibolites are usually fine-grained and depleted in ΣREE (33.14–45.02 ppm), with low (La/Yb) CH values (0.74–3.82). This reflects weak LREE enrichment in relation to HREE, and no Ce and Eu anomalies [(Eu/Eu*) n between 0.98 and 1.04]. Such patterns are similar to T-MORB (1.7–4.3). Additionally, some mafic-ultramafic metaplutonic rocks present chemical composition similar to their volcanic counterparts, and this may indicate cumulates or sills contemporary to this sequence. Zircon U–Pb dating using LA-ICP-MS of three distinct metadacite occurrences (western border: 2234 ± 13 Ma, eastern border: 2212 ± 13 Ma, and central portion: 2156 ± 45 Ma) and metagranodiorites (2181 ± 4.4 Ma) indicates that the sequence was formed during the Rhyacian/Orosirian and later affected by late Neoproterozoic. [ABSTRACT FROM AUTHOR]