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Banded Iron Formations (BIF) developed strongly during the Neoarchean – Paleoproterozoic Eras linked with global environmental processes such as the Great Oxidation Event (GOE) and changes in geodynamics, sea level, geobiology, hydrothermal systems, and sediment deposition conditions. BIF development and distribution worldwide are also related to supercontinent cycles, being a powerful tool to understand the evolution of plate tectonics. In this paper, we used field-based geological-structural data, petrography, X-ray diffraction, and lithogeochemical analyses to perform the first characterization of Banded Iron Formations at the Luis Alves Craton (LAC), Southern Brazil. The LAC BIF are classified as oxide and silicate facies, both with granoblastic texture. Oxide facies consists of quartz and magnetite. Besides these minerals, silicate facies contains olivine and ferrosilite, evidencing granulite metamorphism. Based on major elements oxide facies has a hydrothermal signature, with low content of Al 2 O 3 and TiO 2 , whereas silicate facies register a continental sediment contribution been more enriched in these elements, MgO, MnO, and CaO. Trace-elements also indicate the main source for both silicate and oxide facies, which is seawater with a major influence of low-T hydrothermal sources, besides continental sedimentation sources. The Ce/Ce × anomaly is true negative, representing oxidizing waters, which also may represent a shallow water column depth. The depositional environment is inferred as a shallow, restricted basin. Oxide facies represents sedimentation closer to hydrothermal vents and with weak influence from continental clastic sedimentation, while silicate facies represent sedimentation closer to an adjoining continental landmass. Oxide facies has more Algoma-like characteristics, such as higher Fe and Eu contents, Sm/Yb and Eu/Sm typical of higher hydrothermal fluid inputs, and low siliciclastic contribution. On the other hand, silicate facies resembles Superior-type BIF, with higher siliciclastic contribution, negative Ce/Ce × anomalies, and Eu/Eu* <1.8. In summary, we propose the LAC BIF is representative of a transitional environment from Algoma-to Superior-type. The first depositions of the LAC BIFs may have developed within an Algoma-like environment during the Neoarchean. The waning tectonic and volcanic activity during the Siderian shifted to a platformal environment, with shallower waters that may induce the deposition of carbonates typical of Superior-type deposits. The depositional basin may have been closed by the Rhyacian and those sediments were then pushed down to the lower crust and underwent granulite facies metamorphism. • Oxide and silicate facies BIFs were recognized in the Luis Alves Craton. • These BIFs register granulite metamorphism, having ferrosilite and olivine in their composition. • Through the geochemical data, the depositional paleoenvironment was recognized. • The sedimentary sources of BIFs are both hydrothermal and continental. • These BIFs have characteristics of both Algoma and Superior type deposits. [ABSTRACT FROM AUTHOR]

This study contemplates the geochemical and mineralogical characterization with spatial analysis of the following soil parameters of the "Alto de Santa Tereza" hillside in Recife/Brazil: granulometric; morphoscopic; compositional; chemical; and mineralogical. The general objective of the present study is report on how the weathering in the soil of the slope influenced on the occurrence of landslides. For this purpose, particle size analysis, X-ray diffraction, X-ray fluorescence, Scanning Electron Microscopy, and binocular lens observation were performed. On the studied slope, it was possible to identify two distinct sedimentary facies for the Barreiras Formation sediments: alluvial fans and fluvial channels/floodplains. Featuring, for the most part, sandy-clayey soil with prismatic and spherical, sub-angular to angular quartz grains, moderately selected. Kaolinite and quartz are the predominant minerals in the samples, and silicon oxides and aluminum are the components with the highest percentage. It was noticed that there is a relationship between Ki (silica/alumina ratio) and Kr (silica/alumina ratio and iron oxide) for the studied soils, the Ki values increase linearly with the increment in Kr. The weathering indices demonstrate that the studied soils of Barreiras Formation presented intense chemical alteration. The locations of the previous landslides in region of Recife show that most of the landslide occurrences are associated with the highly weathered zone. [ABSTRACT FROM AUTHOR]

The eastern portion of the Dom Feliciano Belt in southernmost Brazil, known as Pelotas Terrane, is composed of Neoproterozoic rocks presenting metamorphic xenoliths in granitoid rocks, described and interpreted as "basement inliers". Based on novel petrographic, mineral/whole rock/Sr–Nd geochemistry and U–Pb geochronological data, this paper presents the first record of a Paleoproterozoic metagabbro xenolith in the Pelotas Terrane. The studied xenolith exhibits a sharp and angular contact with the host rock and a predominant granoblastic texture, with sub-vertical mm-to cm-thick metamorphic banding, marked by the felsic and mafic bands, composed respectively of bytownite (An 85) ± quartz, and diopside ± tremolite ± epidote. Zircon, apatite, and iron/titanium oxides occur as accessory minerals. The peak metamorphism for this rock is estimated at amphibolite facies conditions. The whole-rock chemistry of the metagabbro suggests a basic derivation (e.g., SiO 2 52 wt%; Al 2 O 3 12 wt%; Ni 33 ppm). The spidergrams demonstrate high LILE and HFSE concentrations. Chondrite-normalized REE patterns show enrichment in LREE. The Sr–Nd isotopic data show 87Sr/86Sr (i) = 0.701024, εNd (i) = 5.44, and Nd-T DM = 2.1 Ga. The metagabbro yielded a U–Pb Concordia age with analytical points arranged in a Discordia line. The upper intercept was interpreted as a magmatic crystallization age of 2.1 Ga (zircon cores), and the lower intercept indicated a resetting age of 616 Ma (zircon rims). The obtained Archean age (2.8 Ga) is interpreted as inherited. Gabbro's metamorphism likely reached the amphibolite facies, elemental and isotopic geochemistry. The remote zircon inheritance of xenoliths that have had polycyclic survival is used to link the occurrence of a gabbro xenolith, in the Pelotas Terrane (Dom Feliciano Belt; Southern Brazil), whose magmatic crystallization age is Paleoproterozoic, with the basement terranes before the Namaquan orogeny, in the Rehoboth region (Gariep Belt and Bushmanland/Namaqualand; Namibia). These units could be related to the evolution of an ancient Paleoproterozoic magmatic arc formed by the convergence of two Archean continents during the evolution of the Atlantica Supercontinent. [Display omitted] • First magmatic record of Paleoproterozoic rock in eastern Dom Feliciano Belt. • Metagabbro xenolith with 87Sr/86Sr (i) = 0.701024, εNd (i) = 5.44, Nd-T DM = 2.1 Ga. • Magmatic arc-related rock linked to the Rehoboth Basement Inlier, Africa. • An important piece in the West Gondwana assembly. [ABSTRACT FROM AUTHOR]

Abstract: After the development of the highly sensitive material Al2O3:C, personal dosimetry using optically stimulated luminescence (OSL) has been continuously adopted in place of thermoluminescence dosimeters (TLD) by different countries (e.g. USA and Japan). In order to use a dosimetric system in Brazil it is necessary to develop a protocol and to fulfill performance and type tests in accordance with the accreditation program approved by the responsible governmental committee. This paper presents a proposal for an accreditation program for OSL personal dosimetry using a commercial dosimetric system, including tests that follow the same rules as applied to TLD and film dosimetry. The experimental results are within the reliability interval and in accordance to the expected behavior. A new test concerning re-analysis of exposed badges is also proposed. [Copyright &y& Elsevier]