Provenance and tectonic setting of neoproterozoic supracrustal rocks from the Ceara Central Domain, Borborema Province (NE Brazil): constraints from geochemistry and detrital zircon ages

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Major- and trace-element and U-Pb analyses of detrital zircons were performed on metavolcano sedimentary sequences and igneous rocks from the Ceara Central Domain (CCD) in the Borborema Province of northeastern Brazil. No significant geochemical differences were found between these rocks, which were possibly initially deposited as parts of a very large metavolcano-sedimentary sequence. Weathering in the source area was moderate, and the sediments were deposited as both sands and clays. The sources of the sediments were likely mixtures of felsic and intermediate rocks deposited predominantly in an active-margin setting with minor contributions of both continental arc and passive margin components. Three main source ages were identified: Palaeoproterozoic (similar to 2.2 Ga), for which potential sources include the Palaeoproterozoic Madalena-Algodoes Suite; early Neoproterozoic (similar to 850 Ma), related to felsic volcanic magmatism due to continental rifting, initial phases of the Santa Quiteria Magmatic Arc, or magmatic arc systems on the margins of the Palaeoproterozoic crust; and late Neoproterozoic (similar to 650 Ma), associated with extensive granite generation and migmatization events accompanying Santa Quiteria Arc activity. Deposition of the CCD volcanosedimentary rocks occurred shortly before regional, collision-type metamorphism accompanying the amalgamation of the SAo Francisco-Congo Cratons (similar to 620-630 Ma).564481500Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [2006/17261-6

High-pressure granulites from Carire, Borborema Province, NE Brazil: Tectonic setting, metamorphic conditions and U-Pb, Lu-Hf and Sm-Nd geochronology

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)In the northwest region of the Ceara Central Domain, Borborema Province, an elongate area of mylonitic diorites and granodiorites is structurally controlled by NE-SW-trending strike-slip faults. Granitic material and layers and lenses of felsic and mafic granulites occur along the main shear zones. We present and discuss petrographic, geothermobarometric. and geochronological (LA-MC-ICPMS U-Pb and Lu-Hf in zircon and Sm-Nd whole-rock) data for these rocks. Felsic granulites are composed of orthopyroxene + clinopyroxene + plagioclase + quartz +/- hornblende +/- garnet +/- biotite +/- feldspar, while the mafic granulites comprise clinopyroxene + plagioclase + garnet + hornblende +/- rutile +/- quartz. The P-T conditions recorded range from 9.4 to 83 kbars and from 804 to 870 degrees C for the felsic granulites and from 13.6 to 10.2 kbars and 910 to 750 degrees C for the mafic granulites. U-Pb zircon ages of granodiorite host rocks are 2157 and 2044 Ma. The felsic granulites yield a U-Pb age of 2110 Ma, while the mafic granulites yield U-Pb zircon ages of 613 and 589 Ma for the metamorphic recrystallization. Sm-Nd and Lu-Hf T-DM ages for the mafic granulites are similar (1.6-1.3 Ga) and share positive values of epsilon(Nd) and epsilon(Hf), which suggests that these mafic rocks were derived from a juvenile Mesoproterozoic crust. In addition, the felsic granulites and the granodiorites have similar TDM-Nd and U-Pb ages (with positive values of epsilon(Nd)), indicating a Paleoproterozoic mantle source for these rocks. (C) 2012 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.2241732892909Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)INCT-ET [573713/2008-1]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [03/07663-3, 07/58535-6]CNPq [42.0222/2005-7]INCT-ET [573713/2008-1

Neoproterozoic tectonic and magmatic episodes in the NW sector of Borborema Province, NE Brazil, during assembly of Western Gondwana

The Medio Coreau domain of NE Brazil is located along the northwest margin of Borborema Province, the western branch of a Brasiliano/Pan-African collisional belt that formed during the assembly of Western Gondwana. The early Paleoproterozoic basement of the Medio Coreau domain is composed of migmatitic gneisses and juvenile granulites, overlain by late Paleoproterozoic and Neoproterozoic rocks intruded by syn- to post-tectonic Brasiliano granitoids. According to integrated structural and geochronological data (U-Pb zircon and monazite ages), the Neoproterozoic tectonic evolution of the Medio Coreau is characterized by low-angle thrusting and transcurrent deformation. U-Pb geochronological data from plutons intruded during this compressional regime indicate the collisional evolution began at approximately 622 Ma and continued until about 591 Ma. The continuation of convergence until approximately 560 Ma resulted in the formation of NE-SW and E-W shear zones within the Borborema Province and adjoining West African provinces. The final stage of the ductile tectonism was characterized by uplift and high-angle fault generation between approximately 560 and 545 Ma. The last tectonic event was an extensional phase, resulting in the formation of the Jaibaras graben and intrusion of post-orogenic granites at around 532 Ma. (c) 2007 Elsevier Ltd. All rights reserved.25327128

Mesoarchean (3.0 and 2.86 Ga) host rocks of the iron oxide-Cu-Au Bacaba deposit, Carajas Mineral Province: U-Pb geochronology and metallogenetic implications

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The Bacaba iron oxide-copper-gold deposit, situated within a WNW-ESE-striking shear zone in the Carajas Domain, Carajas Mineral Province, is hosted by the Serra Dourada Granite, the Bacaba Tonalite, and crosscutting gabbro intrusions, which were intensely affected by sodic (albite-scapolite), potassic, chloritic, and hydrolytic hydrothermal alteration. This deposit is located 7 km northeast of the world-class Sossego iron oxide-copper-gold deposit and might represent a distal and deeper portion of the same or related hydrothermal system. The U-Pb laser ablation inductively coupled plasma-mass spectrometry data for zircon from a sodically altered sample of the Serra Dourada Granite yielded a 2,860 +/- 22 Ma (MSWD=11.5) age. Three samples from the Bacaba Tonalite, including one with potassic alteration and two with Cu-Au mineralization, rendered the 3,001.2 +/- 3.6 Ma (MSWD=1.8), 2,990.9 +/- 5.8 Ma (MSWD=1.9), and 3,004.6 +/- 9 Ma (MSWD=2.2) ages, respectively. The ca. 2.86 and ca. 3.0 Ga ages are interpreted as the timing of the igneous crystallization of the Serra Dourada Granite and the Bacaba Tonalite, respectively, and represent the oldest magmatic events recognized in the Carajas Domain. The Serra Dourada Granite and the Bacaba Tonalite are interpreted to greatly predate the genesis of the Bacaba deposit. A genetic link is improbable in the light of the similarities with the Sossego deposit, which is also hosted by younger ca. 2.76 Ga metavolcano-sedimentary units of the ItacaiA(0)nas Supergroup. In this context, the iron oxide-copper-gold deposits in the southern sector of the Carajas Domain could be mainly controlled by important crustal discontinuities, such as a regional shear zone, rather than be associated with a particular rock type. These results expand the potential for occurrences of iron oxide-copper-gold deposits within the Mesoarchean basement rocks underlying the Carajas Basin, particularly those crosscut by Neoarchean shear zones.467789811Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [555065/2006-5]CNPq [303359/2008-0]FAPESP [MCT/CNPq/Fapespa 573733/2008-2

Evidence for Neoproterozoic continental arc magmatism in the Santa Quiteria Batholith of Ceara State, NW Borborema province, NE Brazil: implications for the assembly of West Gondwana

Recent field investigations and geochronological studies of Neoproterozoic rocks in the northwestern part of the Borborema Province, Ceara State, NE Brazil provide important clues pertaining to the nature of convergence between the Borborema Province and the West African-Sao Luis craton during the assembly of West Gondwana. U-Pb zircon data indicate that the earliest evidence of convergent magmatism along the northwest margin of the Borborema Province occurred around 777 Ma, and was followed by the development of a large continental arc batholith (Santa Quiteria batholith) between ca. 665 and 591 Ma within the central part of Ceara State. These findings, along with supporting geophysical data, suggest that convergence between the Borborema Province and the West African-Sao Luis craton involved closure of an oceanic realm with subduction polarity to the southeast beneath the northwestern part of the province. Consequently, it seems likely that the Pharusian Ocean was continuous from the Hoggar Province in West Africa into South America during the late Neoproterozoic and additional data suggests that it may have even been connected with the Goianides Ocean of the Brasilia Belt farther to the southwest.6226527