https://jgsb.cprm.gov.br/index.php/journal/issue/feed Journal of the Geological Survey of Brazil 2022-09-22T12:56:20+00:00 Evandro Klein editor_jgsb@sgb.gov.br Open Journal Systems <p><strong>SCOPE AND MISSION</strong></p> <p><strong>Journal of the Geological Survey of Brazil (JGSB)</strong> is a peer-reviewed, open-access periodical, published three times a year (April, August, and December) by the Geological Survey of Brazil, which is attached to the Ministry of Mines and Energy of Brazil.</p> <p>Our Mission is the dissemination of original, high-quality scientific research, and in-depth reviews of relevant subjects that cover all disciplines of the Earth Sciences in Brazil, and elsewhere, intending to be of interest to a broad audience of geological scientists.</p> https://jgsb.cprm.gov.br/index.php/journal/article/view/179 Petrography, geochemistry and zircon U-Pb geochronology of the Siderian-Rhyacian granitoids of NW Bacajá Domain, Amazonian Craton 2022-07-28T10:20:40+00:00 Cleberson Vieira da Silva clebersonviieira@gmail.com Wagner Silva Amaral wamaral@unicamp.br Felipe Holanda dos Santos felipeholanda@ige.unicamp.br <p>Archean and Paleoproterozoic granitoids with different geochemical affinities are widely distributed in the basement of high-grade metamorphic rocks of the Bacajá Domain, which consists of Rhyacian granite-greenstone terrain with Archean-Siderian fragments, one of which is in the southeastern Amazonian Craton. Understanding the diversity of these rocks in the geological record is essential to improve the evolution of knowledge of the Amazonian Craton. Thus, this work presents petrographic, geochemical, and geochronological (U-Pb LA-ICP-MS in zircon) data on granitoids of the São José Complex, Canaã Granite, Sant’Ana Granodiorite and Uirapuru Granite, that occur in the northwestern of the Bacajá Domain. São José Complex is composed of biotite tonalites and granodiorites slightly peraluminous from medium to high-K, magnesian and I-type affinities. One U-Pb zircon age was obtained at 2502 ± 6 Ma, which may represent a subduction magmatism in pre-collisional stage arc environment prior to the Transamazonian Orogeny, formed from the melt of Archean crustal sources and amphibolitic rocks. The granitoids like Canaã Granite, Sant’Ana Granodiorite and Uirapuru Granite are composed of weakly metaluminous to peraluminous monzogranites, granodiorites with subordinate tonalites and syenogranites, with high SiO<sub>2</sub> and K<sub>2</sub>O contents and high-K calc-alkaline to shoshonitic affinities, of ferroan I-type and A-type. The age of 2124 ± 7 Ma was obtained for the Sant’Ana Granodiorite, which may indicate its formation in syn- to post-collisional environments related to magmatic episodes of the Transamazonian Orogeny. The granodiorite was crystallized from partial melt of crustal sources derived from intermediate rocks such as tonalites and psammitic gneisses that occur in the region.</p> 2022-09-09T00:00:00+00:00 Copyright (c) 2022 Journal (JGSB) and the authors https://jgsb.cprm.gov.br/index.php/journal/article/view/183 Composition and P-T conditions of the lithospheric mantle beneath the Azimuth 125º Lineament, Northern and Southeastern Brazil: constraints from peridotite xenoliths enclosed in diamond-bearing kimberlites 2022-08-17T16:10:20+00:00 Vidyã Vieira Almeida vidya.almeida@cprm.gov.br Joseneusa Brilhante Rodrigues joseneusa.rodrigues@cprm.gov.br Izaac Cabral Neto izaac.cabralneto@cprm.gov.br Francisco Valdir Silveira francisco.silveira@cprm.gov.br Homero Braz Silva homero@brasilexplore.com.br <p>We present new petrographic and chemical data together with calculated <em>P</em>-<em>T</em> equilibrium conditions of peridotite xenoliths enclosed in kimberlites from Rondônia, Northern Brazil (Cosmos-1 and Carolina-1) and Minas Gerais, Southeastern Brazil (Canastra-1) located in the Azimuth 125º Lineament. The composition of the mantle minerals is distinct in both areas, which can be related to the diversity of the lithospheric mantle beneath the southwestern portion of the Amazonian Craton and the Brasília Belt. New and compiled chemical data indicate that subcalcic G10 garnet occurs in samples from the Canastra-1 kimberlite and other occurrences of the Alto Paranaíba Igneous Province and can be related to the remnants of the Archean lithospheric mantle of the São Francisco Craton beneath the area. The garnets from Rondônia are mostly G5 (pyroxenitic) and G9 (lherzolitic) with a higher abundance of G3 (eclogitic) and G4 (pyroxenitic/eclogitic) relative to the Alto Paranaíba Igneous Province. Higher pressures and temperatures were calculated for the samples from Rondônia (40-60 kbar and 1030-1380 ºC) compared to samples from Minas Gerais (25-40 kbar and 730-1000 ºC). The peridotite xenoliths from Rondônia show <em>P</em>-<em>T </em>equilibrium conditions in the diamond stability field and can be the source of at least part of the diamond from the area. The <em>P</em>-<em>T</em> stability fields of the xenoliths from both locations are aligned close to the 40 mW/m<sup>2</sup> geotherm. The data indicate that the cratonic 40 mW/m<sup>2</sup> geothermal gradient in Rondônia may be related to a process of thermal relaxation of the lithospheric mantle after the Paleoproterozoic to Mesoproterozoic tectonothermal events of the southwestern Amazonian Craton until the sampling of the xenoliths by the magma in the Permian-Triassic.</p> 2022-10-26T00:00:00+00:00 Copyright (c) 2022 Journal (JGSB) and the authors https://jgsb.cprm.gov.br/index.php/journal/article/view/181 Paleoproterozoic crustal evolution and Mesoproterozoic overprint in the Roosevelt-Guariba Transpressive Belt, Juruena Terrain, Southeastern Amazonas, Brazil 2022-07-26T19:44:04+00:00 Marcelo Esteves Almeida marcelo.esteves@cprm.gov.br Antônio Charles da Slva Oliveira charles.oliveira@cprm.gov.br João Orestes Schneider dos Santos orestes.santos@bigpond.com Gilles Ruffet gilles.ruffet@univ-rennes1.fr Joseneusa Brilhante Rodrigues joseneusa.rodrigues@cprm.gov.br <p>The Juruena Terrain (Rondônia-Juruena Province) in the southeastern Amazonas State shows a NW-SE dextral shear zones system denominated Roosevelt-Guariba Transpressive Belt (RGTB). The RGTB was generated in response to intracontinental crustal reworking, juxtaposing Paleoproterozoic Juruena granitic-gneiss and chronocorrelated supracrustal associations. This granitic-gneiss basement shows high-K calc-alkaline (Teodósia Suite) to transitional I- to A-type (Igarapé das Lontras Suite) signatures, produced in a continental magmatic arc setting around 1760-1740 Ma (zircon, titanite; U-Pb SHRIMP, LA-ICP-MS). New geochronological data about of the deformation and metamorphic rocks in the RGTB were obtained from migmatite paragneisses, amphibolites, S-type leucogranite (Quatro Cachoeiras Complex and Itamaraty Suite; zircon U-Pb SHRIMP) and protomylonites and mylonites (Igarapé das Lontras and Teodosia protholiths; amphibole-muscovite-sericite Ar-Ar step heating). The results suggest that Southeastern Amazonas (northern Juruena Terrain) was metamorphised/deformed during 1530-1460 Ma under temperatures of 900<sup> o</sup>C (zircon) to 580<sup>o</sup>C (hornblende) and 420<sup>o</sup>C (muscovite). The geochronological data show that the granite-gneiss basement (continental magmatic arc) and supracrustal rocks (foreland basin) were reworked by a regional event with age interval of 1530 Ma (high grade and anatexis) to 1460 Ma (medium grade). Finally, the Juruena Terrain is affected by a younger low-T event (1300 Ma, muscovite Ar-Ar step heating) with wide NE-trending structures (e.g. Buiuçu Shear Zone). This 1.3 Ga event suggests a continental reactivation caused by the pericratonic deformation related to Candeias/Sunsás Orogeny during the Columbia Supercontinent break-up, before of the Rodinia Supercontinent assembly. In summary, the Juruena Terrain in the southeast Amazonas shows a complex metamorphic and structural intracontinental evolution, involving polycyclic events since late Orosirian to Ectasian in a convergent tectonic setting. Therefore, the Juruena Terrain shows similar accretionary histories with others orogens and has apparent long-lived connections with Laurentia (Yavapai Province) and Baltica (Transscandinavian Igneous Belt), forming the core of the Columbia Supercontinent.</p> 2022-11-11T00:00:00+00:00 Copyright (c) 2022 Journal (JGSB) and the authors https://jgsb.cprm.gov.br/index.php/journal/article/view/191 Understanding the origin of the airborne geophysical signatures of the Jalapão geomorphological units, Urucuia Basin, Central–Northern Brazil 2022-09-22T12:56:20+00:00 Adolfo Silva adolfo.barbosa@cprm.gov.br Felipe da Mota Alves felipe.alves@cprm.gov.br <p>This study was carried out in order to understand the airborne geophysical signatures observed in the Jalapão region, Urucuia Basin, eastern Tocantins state. Airborne geophysical data (magnetic and gamma-ray spectrometry) and satellite images (Advanced Spaceborne Thermal Emission and Reflection Radiometer – ASTER) were processed and interpreted. I It was possible to characterize the main geomorphological units of the Jalapão region (residual landforms and dissected surfaces). The residual landforms (e.g., Serra do Espirito Santo and Occidental Baiano Plateau) have high concentrations of equivalent U (eU) and equivalent Th (eTh), and low K concentrations. ASTER image analysis suggests that these concentrations can be correlated with the products of chemical weathering (Fe oxides, clay, and weathering-resistant opaque minerals and other accessories). The dissected surfaces (mainly Jalapão Surface), however, is deficient in these radioelements, probably due to the quartz-rich nature of the related soils. Furthermore, the Jalapão Surface is practically non-magnetic, whereas residual landforms exhibit magnetic signals of low amplitude and high frequency, and are of unknown origin. The results suggest that the sources of these magnetic anomalies are shallow (≈ 270 m) and could be associated with ferrimagnetic minerals present in the alteration zone and/or in the ferruginous cements of the Serra das Araras Formation sandstones. The depth to basement in the region of this basin (1.44 km) rules out the possibility that the magnetic sources could be related to residual landforms.</p> 2022-11-04T00:00:00+00:00 Copyright (c) 2022 Journal (JGSB) and the authors