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The Borborema Province hosts several Mn-rich metasedimentary sequences, containing up to 40 wt% MnO(total). These sequences are composed of Mn oxide and Mn silicate lenses that alternate with spessartite quartzite layers. They are also spatially associated with graphite-bearing gneissic and granitic rocks. Here, we use the Lagoa do Riacho manganese deposit, a Mn-rich sequence of the northern Borborema Province (within the Canindé do Ceará Complex), to constrain the time of deposition of the Mn-rich sedimentary protolith, discuss its tectonic setting, and draw correlations between African and Brazilian manganese deposits. The age of the youngest detrital zircon population from a meter-sized spessartite quartzite bed, interlayered with oxidized Mn ore, was close to 2130 Ma. Similarly, a gneiss hosting the Mn mineralization yielded a maximum depositional age close to 2156 Ma. U–Pb dating of zircon metamorphic overgrowths from the Mn-bearing sequences and host rocks coupled to a zircon U–Pb crystallization age of an intrusive leucocratic granite provided a minimum age interval for the Mn-rich succession (ca. 2106–2023 Ma). These constraints point to a Rhyacian depositional age (ca. 2200–2100 Ma) for the Mn-rich precursors, which were most likely deposited as syn-orogenic sediments. The results also allow us to conclude that the age range of 2200–2100 Ma is coeval with the timing of deposition of other world-class manganese deposits, such as those from the Francevillian and Birimian groups in Gabon and Ghana, respectively, besides those from the South American Platform (e.g., Serra do Navio, Carajás, and Minas Gerais). [ABSTRACT FROM AUTHOR]

Sanukitoid rocks make up a complete magmatic series with distinct geochemical characteristics of TTG suites and granitoids from modern magmatic arcs and are regarded as markers of the transition from typically Archean geodynamics to modern plate tectonics. Although most known sanukitoid suites formed during the Neoarchean and Mesoarchean, numerous papers have characterized Paleoproterozoic magmatic arc granitoid rocks showing affinity with the sanukitoid series. This work presents new data from field, lithogeochemistry, zircon U-Pb geochronology, and Sm-Nd and Sr isotopic studies on granodioritic granulites with sanukitoid signatures from the Juiz de Fora Complex (JFC), one of the Paleoproterozoic tectonic components of the Minas-Bahia Orogenic System (MBOS), southern São Francisco Paleocontinent (southeastern Brazil). These rocks crystallized at -2175 Ma and present values of εNdt between -4.0 and +0.5, TDM between 2.57 and 2.12 Ga, and 87Sr/86Sri between 0.6937 and 0.7137. We interpret these rocks as the result of crystallization of magmas from a hybrid mantle source extensively contaminated by crustal material during protracted subduction. In southeastern São Francisco Paleocontinent, the association of sanukitoid rocks with other mag- matic arc rocks points to a complex and prolonged Rhyacian accretionary system similar to modern plate tectonics. [ABSTRACT FROM AUTHOR]

We present U–Pb Sensitive High Mass Resolution Ion MicroProbe (SHRIMP) data of unexposed igneous-metamorphic basement rocks from two areas of the southeastern Río de la Plata craton (RPC; Buenos Aires city) located within the Buenos Aires–Piedra Alta (BAPA) terrane – and the Tapalqué area (Buenos Aires province) – located within the Tandilia terrane, and discuss the tectonic evolution of that portion of the craton based on both the new data and previous work. The newly obtained geochronological data of drill cores indicate that: (a) arc magmatism occurred at 2164–2186 Ma corresponding to early ‘Trans-Amazon’ (early Rhyacian) arc magmatism; (b) the age of collision between the BAPA and Tandilia terranes is inferred to have commenced at ca. 2110 Ma; (c) peak metamorphism occurred at ca. 2069 Ma; and (d) the presence of rocks related to the RPC is confirmed under Cenozoic sediments in a large area between Martin Garcia Island and Tandil. We envisage an early Rhyacian divergent double subduction scheme between the BAPA and Tandilia terranes – i.e. N-dipping towards BAPA and S-dipping towards Tandilia – prior to the late Rhyacian collision between these two terranes. [ABSTRACT FROM PUBLISHER]