Registros magmáticos extensionais e colisionais no Terreno Apiaí, sul-sudeste do Brasil: integração de dados U-PB - Zircão

The aim of this work is the presentation of a synthesis of available geochronological data for the basement inliers and metavolcano-sedimentary sequences which occur in the southern part of the Apiaí Terrane, south-southeastern Brazil. These data, especially those obtained during the last decade, have made substantial modifications to the tectonic scenario of south-southeastern Brazil with the recognition of the presence of extensional basins (continental rifts) with magmatism and sedimentation at the late Paleoproterozoic (1790 - 1750 Ma) and of the Mesoproterozoic (1600 - 1450 Ma). These processes started at the late Paleoproterozoic in the Betara, Perau and Apiai Mirim Nuclei, and the basins became widerduring the Mesoproterozoic with the deposition of the Betara, Perau, Votuverava and Água Clara metavolcano-sedimentary sequences. A different pattern is found for the Itaicoca Sequence which occupies the northern part of the Apiaí Terrain. Here two rock associations of different ages are found. The first is a metamorphosed carbonate platform association with subalkaline, tholeiitic metabasic rocks with minimum deposition ages at the end of the Mesoproterozoic or beginning of the Neoproterozoic (Itaiacoca Sequence; 1030 - 900 Ma), while the second mainly contains metapsammites and metavolcanic rocks including ultrapotassic trachytes deposited during the Cryogenian-Ediacaran transition between 645 and 628 Ma (Abapã Sequence). It is then proposed that the present scenario of the Apiaí Terrane be representative of the distinct tectono-sedimentary histories, reflecting a polycyclic evolution. In the Mesoproterozoic, stable conditions prevailed, withthe deposition of the majority of the sequences (Lajeado, Água Clara, Betara, Perau, Votuverava) in a passive margin context, succeded by a Tonian extensional phase (deposition of the Itaiacoca Sequence). In the Ediacaran the region was transformed into an unstable active margin, with the predominance of magmatic arcs (Três Córregos, Cunhaporanga and Agudos Grandes) and restricted sedimentation (Abapã, Antinha and Iporanga Sequences).O principal objetivo deste trabalho é apresentar uma síntese dos dados geocronológicos disponíveis para as sequências metavulcano-sedimentares e núcleos de embasamento que ocorrem na porção sul do Terreno Apiaí, sul-sudeste do Brasil. Os dados obtidos, principalmente na última década, têm modificado substancialmente o cenário tectônico do sul-sudeste brasileiro, identificando a presença de bacias extensionais (rifts continentais) com magmatismo e sedimentação associada do final do Paleoproterozoico (1790 - 1750 Ma) e do Mesoproterozoico (1600 - 1450 Ma). O desenvolvimento desses processos parecem ter se iniciado no final do Paleoproterozoico (Núcleos Betara, Perau e Apiaí Mirim), evoluindo para bacias mais amplas durante o Mesoproterozoico com a deposição das sequências metavulcanossedimentares Betara, Perau, Votuverava e Água Clara. Padrão distinto é observado para a Sequência Itaiacoca, que ocupa a porção setentrional do Terreno Apiaí. O estudo geológico-geocronológico caracterizou a existência de dois conjuntos litológicos temporalmente distintos, o primeiro representado por uma associação plataformal metacarbonática, que inclui rochas metabásicas de natureza toleítica/subalcalina, com idades mínimas de deposição relacionadas ao final do Mesoproterozoico/início do Neoproterozoico (Sequência Itaiacoca: 1.030-900 Ma). O segundo conjunto é representado principalmente por rochas metapsamíticas com metavulcânicas associadas, incluindo traquitos ultrapotássicos, depositados na transição Criogeniano/Ediacarano (Sequência Abapã: 645-628 Ma). O presente cenário sugere histórias tectono-sedimentares distintas para o Terreno Apiaí, refletindo uma evolução policíclica. Durante o Mesoproterozoico predominaram condições relativamente estáveis com a deposição de grande parte das sequências metavulcanossedimentares (Lajeado, Água Clara, Betara, Perau, Votuverava), num contexto de margem passiva, sucedidos pela deposição da Sequência Itaiacoca, associada a regimes extensionais do Toniano. No Ediacarano prevaleceram condições instáveis, de margem ativa, caracterizadas por restrita sedimentação (Sequências Abapã, Antinha e Iporanga) e colocação dos batólitos graníticos Três Córregos, Cunhaporanga e Agudos Grandes, representantes de arcos magmáticos

Análises in situ de U e Pb em zircão por SHRIMP II por controle remoto e de Hf por LA-ICP-MS: um exemplo de datação e da evolução genética de zircão através da razão 176Hf/177Hf em amostra da pedreira Ita no Complexo Atuba, SE Brasil

Operar o espectrômetro de massa SHRIMP à distância, remotamente via Internet, é sem dúvida uma técnica alternativa de grande interesse para a datação de cristais de zircão. Embora não represente avanço no método geocronológico U-Pb em zircão, a técnica de operação remota traz, além de facilidade, grande economia nesse tipo de análise. Foi executada pela primeira vez em análises espectrométicas envolvendo dois laboratoratórios internacionais (São Paulo, Brasil - Beijing, China) possibilitando a obtenção de resultados em tempo real. O procedimento foi aplicado em três amostras de rochas gnáissico-migmatíticas da pedreira Ita (próxima à cidade de Curitiba - Paraná - Brasil) pertencentes ao Complexo Atuba. Tais rochas, quando analisadas através do método U-Pb (TIMS) demonstraram uma evolução complexa, com idades bastante imprecisas. A presença de importantes heranças arqueanas e paleoproterozoicas, neste complexo, foram confirmadas nas zonas internas de cristais de zircão obtidas em leucossomas neoproterozoicos. Análises adicionais realizadas em rochas dioríticas indicaram ser intrusivas, e não encaixantes, e apresentaram idades relacionadas às colisões continentais (0.6 Ga) envolvidas durante a assembléia de Gondwana, no Neoproterozoico. A determinação das razões de isótopos de Hf em cristais de zircão, por meio de LA-ICP-MS, representa uma nova opção para checar a importância relativa da contribuição de material do manto (&#949;Hf >; 0) e crosta (&#949;Hf ; 0) and crustal contributions (&#949;Hf < 0) during the growth of the zircon crystals. While the archean component in the complex was derived from the mantle (&#949;Hf +1.5 to +8.7) the paleoproterozoic component had a crustal contribution (&#949;Hf-9.1 to -10.1)

The Precambrian Khondalite Belt in the Daqingshan area, North China Craton: evidence for multiple metamorphic events in the Palaeoproterozoic era

High-grade pelitic metasedimentary rocks (khondalites) are widely distributed in the northwestern part of the North China Craton and were named the ‘Khondalite Belt’. Prior to the application of zircon geochronology, a stratigraphic division of the supracrustal rocks into several groups was established using interpretative field geology. We report here SHRIMP U–Pb zircon ages and Hf-isotope data on metamorphosed sedimentary and magmatic rocks at Daqingshan, a typical area of the Khondalite Belt. The main conclusions are as follows: (1) The early Precambrian supracrustal rocks belong to three sequences: a 2.56–2.51 Ga supracrustal unit (the previous Sanggan ‘group’), a 2.51–2.45 Ga supracrustal unit (a portion of the previous upper Wulashan ‘group’) and a 2.0–1.95 Ga supracrustal unit (including the previous lower Wulashan ‘group’, a portion of original upper Wulashan ‘group’ and the original Meidaizhao ‘group’) the units thus do not represent a true stratigraphy; (2) Strong tectono-thermal events occurred during the late Neoarchaean to late Palaeoproterozoic, with four episodes recognized: 2.6–2.5, 2.45–2.37, 2.3–2.0 and 1.95–1.85 Ga, with the latest event being consistent with the assembly of the Palaeoproterozoic supercontinent Columbia; (3) During the late Neoarchaean to late Palaeoproterozoic (2.55–2.5, 2.37 and 2.06 Ga) juvenile, mantle-derived material was added to the crust

Petrografia, geoquímica e geocronologia dos granitos patrimônio Santo Antônio e São Domingos (Suíte Cunhaporanga, Paraná, Sudeste do Brasil)

The Patrimônio Santo Antônio and São Domingos Granites are located in the northwest portion of the Itaiacoca Belt, which is part of the Apiaí Terrane (or tectonic domain), a segment of the southern Ribeira Belt, the major tectonic unit of the Mantiqueira Province (Southeast Brazil). These granites are related to the Cunhaporanga Granitic Suite and are intrusive into metasedimentary rocks of the Itaiacoca Group. The plutons are represented mainly by porphyritic monzogranites, with rare occurrences of syenogranites. The porphyritic monzogranites are ferroan to magnesian, high-K, alkali-calcic, and metaluminous to peraluminous. Trace elements patterns of the granites, which have been locally affected by hydrothermal alteration, suggest an association with magmas emplaced in a late- to post-tectonic setting. The geochemical signatures suggest a mantle source enriched in incompatible elements remobilized from the oceanic crust during subduction. The geochronological age of the Patrimônio Santo Antônio Granite (589 ± 6 Ma, zircon, U-Pb SHRIMP) indicates that the magmatism associated with these plutons occurred between the final stages of evolution of the Cunhaporanga Granitic Suite (ca. 650 to 590 Ma) and the emplacement of the post-orogenic and anorogenic plutons of the Apiaí Domain (ca. 590 to 570 Ma).Os Granitos Patrimônio Santo Antônio e São Domingos localizam-se na porção noroeste da Faixa Itaiacoca constituinte do Terreno (ou domínio tectônico) Apiaí segmento do Cinturão Ribeira Meridional da Província Mantiqueira localizada no sudoeste do Brasil. Ambos estão relacionados com a Suíte Granítica Cunhaporanga e são intrusivos em rochas metassedimentares do Grupo Itaiacoca. São constituídos por ocorrências esparsas de sienogranitos e majoritariamente por monzogranitos porfiríticos de caráter metaluminoso a peraluminoso, álcali-cálcico de alto K e comportamento ferroso a magnesiano. O comportamento dos elementos traços, por vezes afetado por alteração hidrotermal, é sugestivo de magmatismo pós a tardi-colisional, com assinaturas geoquímicas que sugerem origem a partir de manto enriquecido pela adição de elementos incompatíveis remobilizados de crosta oceânica durante subducção. A idade geocronológica obtida para o Granito Patrimônio Santo Antônio (589 ± 6 Ma, zircões, U-Pb, SHRIMP) situa o magmatismo destes plútons entre os estágios finais de evolução da Suíte Granítica Cunhaporanga (ca. 650 a 590 Ma) e da colocação dos plútons pós-orogênicos e anorogênicos do Domínio Apiaí (ca. 590 a 570 Ma)

Increased Provision of Bioavailable Mg through Vegetables Could Significantly Reduce the Growing Health and Economic Burden Caused by Mg Malnutrition

Magnesium (Mg) is an essential mineral nutrient for human health and its deficiency associated with many diseases, including stroke, heart failure, and type 2 diabetes. Vegetables are an important source of dietary Mg for humans. In this study, we quantified vegetable Mg content by a global meat analysis, analyzed human health, and economic impact caused by Mg deficiency. Results revealed that vegetable Mg content showed a large variation with an average value of 19.3 mg 100 g−1 FW. Variation in per capita vegetable-Mg supply in different continents is largely ascribed to continental difference in the amount and the type of vegetables produced. The health and economic loss attributed to Mg deficiency are estimated to be 1.91 million disability-adjusted life years (DALYs) and 15.8 billion dollars (0.14% of GDP), respectively. A scenario analysis indicated that the increasing vegetable production (increased by 8.9% and 20.7% relative to 2017 in 2030 and 2050) and vegetable Mg content (increased by 22% through biofortification) could significantly reduce DALYs (1.24 million years) and economic burden (0.09% of GDP). This study could guide a major re-balance of production practices, species cultivated, and Mg biofortification to provide sufficient vegetable Mg for better human Mg nutrition

Lightness timescale for terrestrial sediments of China

The Nihewan Beds at Yangyuan reflect apparently continuous, high-resolution deposition of fluvial-lacustrine sediment in the climatically important loess deposit regions of north China. The Hutouliang section forms the upper portion of Nihewan Beds deposited during the Brunhes magnetic polarity chron. Lightness values measured on successive samples display similar variability to the aeolian flux record of oceanic sediment core V21-146 located downwind from this area in the North Pacific. The oxygen isotope timescale of core V21-146 was transferred to the lightness curve to provide a preliminary timescale allowing more detailed age control in the Hutouliang section. This timescale will provide useful assistance in dating boundary ages of the loess-soil sequence in China and interpreting regional climatic data

Dating of zircon from high-grade rocks: Which is the most reliable method?

Magmatic zircon in high-grade metamorphic rocks is often characterized by complex textures as revealed by cathodoluminenscence (CL) that result from multiple episodes of recrystallization, overgrowth, Pb-loss and modifications through fluid-induced disturbances of the crystal structure and the original U-Th-Pb isotopic systematics. Many of these features can be recognized in 2-dimensional CL images, and isotopic analysis of such domains using a high resolution ion-microprobe with only shallow penetration of the zircon surface may be able to reconstruct much of the magmatic and complex post-magmatic history of such grains. In particular it is generally possible to find original magmatic domains yielding concordant ages. In contrast, destructive techniques such as LA-ICP-MS consume a large volume, leave a deep crater in the target grain, and often sample heterogeneous domains that are not visible and thus often yield discordant results which are difficult to interpret. We provide examples of complex magmatic zircon from a southern Indian granulite terrane where SHRIMP II and LA-ICP-MS analyses are compared. The SHRIMP data are shown to be more precise and reliable, and we caution against the use of LA-ICP-MS in deciphering the chronology of complex zircons from high-grade terranes