Introduction to the special issue on "Geoconservation" of the Journal of the Geological Survey of Brazil

This Special Issue on Geoconservation brings relevant contributions from Brazilian researchers on topics ranging from data collection to geoscientific outreach. The ten selected papers were initially presented as abstracts at the V Brazilian Symposium on Geological Heritage, held in Crato, Ceará, from October 14 to 18, 2019

Potencial geoturístico do Parque Estadual da Serra do Ibitipoca, sudeste do estado de Minas Gerais

The Ibitipoca Mountain is a spectacularly morphostructural feature located between the Santa Rita do Ibitipoca and Lima Duarte cities, southeast Minas Gerais State, between the Parallel 21º38' and 21º44', and Meridians 43º50' and 44º00'. In this environment, was created in 1973 Ibitipoca State Park by Forest Institute of Minas Gerais State, which protects an area of 1,488 ha, with higher altitudes ranging from 1784 m, for the Morro da Lombada and 1722 m of Pico do Pião. This natural feature represents a great declivity of the Serra da Mantiqueira widely flattened with a plateau in the north portion, and a devastated south topography. In the geological context, Ibitipoca Mountain consists mainly of quartzites and coarse grain size, interspersed with layers of fine micaceous quartzites and garnet-sillimanite-biotite schist. The sediments that filled the original sedimentary basin have been metamorphosed in amphibolite facies, and deformed in a compressive tectonic regime resulting from an evolving nappe folding type, with the subsequent development of systems of faults and shear zones of high angle. The result of this tectonic event in sedimentary transitional continent-ocean, associated with erosion action, provided the development of fifteen wonderful and unique caves in quartzites, specially the Bromelias Cave with more development. The geomorphology can be summarized by the occurrence of escarpment plunging toward the river valleys and of Rio do Salto and Córrego da Mata, controlled by major tectonic folding that affected the metasedimentary rocks. The relief of the Ibitipoca Mountain present ruiniform forms, lapies and small valleys that may have been generated by processes of landslides galleries caves or doline. The rocks of PEI have a complex tectonic evolution that result in interesting geoforms. This ancient geological environment shows surprisingly exuberant flora and fauna and exotic caverns and pits that constitute potential areas to Geotourism.A Serra do Ibitipoca é uma feição morfoestrutural espetacular localizada entre os municípios de Santa Rita do Ibitipoca e Lima Duarte, sudeste do Estado de Minas Gerais, aproximadamente entre o paralelo 21º38' e 21º44', e meridianos 43º50' e 44º00'. Neste ambiente, foi criado em 1973 o Parque Estadual do Ibitipoca (PEI) pelo Instituto Estadual de Florestas de Minas Gerais, que protege uma área de 1488 ha, com altitude média de 1500m e altitudes superiores que variam de 1784m, referente ao Morro da Lombada e 1722m ao Pico do Pião. A Serra do Ibitipoca representa um contraforte proeminente da Serra da Mantiqueira, e constitui-se em duas cristas aplainadas ao norte e arrasadas ao sul. No âmbito geológico, a Serra do Ibitipoca é constituída basicamente por quartzitos de granulometria grossa, intercalados por camadas de quartzitos finos micáceos e granada-sillimanita-biotita xisto. Os sedimentos que preencheram a bacia sedimentar original foram metamorfizados na fácies anfibolito, e deformados em regime tectônico compressivo, resultantes de uma evolução tipo nappe de dobra, com desenvolvimento subseqüente de sistemas de falhas e zonas de cisalhamento de alto ângulo. O resultado desta manifestação tectônica em ambiente sedimentar transicional continente-oceano, associado à atuação de processos erosivos, propiciou o desenvolvimento de quinze magníficas e peculiares grutas formadas em rochas quarzíticas, destacando-se a Gruta das Bromélias com maior extensão. A geomorfologia pode ser resumida pela ocorrência de cristas que mergulham na direção dos vales do rio do Salto e Córrego da Mata, controladas por grandes dobramentos tectônicos que afetou o pacote metassedimentar. O relevo da Serra do Ibitipoca possui feições que chamam a atenção, como pontes naturais, dolinas, lapiés e pequenos vales que podem ter sido gerados por processos de desabamentos de galerias das cavernas. As rochas do PEI têm uma evolução tectônica complexa que resultam em geoformas interessantes. Este antigo ambiente geológico apresenta surpreendentemente flora e fauna exuberantes e exóticas cavernas e grutas que constituem áreas potenciais para o Geoturismo

Worldwide trends in hypertension prevalence and progress in treatment and control from 1990 to 2019: a pooled analysis of 1201 population-representative studies with 104 million participants.

BACKGROUND: Hypertension can be detected at the primary health-care level and low-cost treatments can effectively control hypertension. We aimed to measure the prevalence of hypertension and progress in its detection, treatment, and control from 1990 to 2019 for 200 countries and territories. METHODS: We used data from 1990 to 2019 on people aged 30-79 years from population-representative studies with measurement of blood pressure and data on blood pressure treatment. We defined hypertension as having systolic blood pressure 140 mm Hg or greater, diastolic blood pressure 90 mm Hg or greater, or taking medication for hypertension. We applied a Bayesian hierarchical model to estimate the prevalence of hypertension and the proportion of people with hypertension who had a previous diagnosis (detection), who were taking medication for hypertension (treatment), and whose hypertension was controlled to below 140/90 mm Hg (control). The model allowed for trends over time to be non-linear and to vary by age. FINDINGS: The number of people aged 30-79 years with hypertension doubled from 1990 to 2019, from 331 (95% credible interval 306-359) million women and 317 (292-344) million men in 1990 to 626 (584-668) million women and 652 (604-698) million men in 2019, despite stable global age-standardised prevalence. In 2019, age-standardised hypertension prevalence was lowest in Canada and Peru for both men and women; in Taiwan, South Korea, Japan, and some countries in western Europe including Switzerland, Spain, and the UK for women; and in several low-income and middle-income countries such as Eritrea, Bangladesh, Ethiopia, and Solomon Islands for men. Hypertension prevalence surpassed 50% for women in two countries and men in nine countries, in central and eastern Europe, central Asia, Oceania, and Latin America. Globally, 59% (55-62) of women and 49% (46-52) of men with hypertension reported a previous diagnosis of hypertension in 2019, and 47% (43-51) of women and 38% (35-41) of men were treated. Control rates among people with hypertension in 2019 were 23% (20-27) for women and 18% (16-21) for men. In 2019, treatment and control rates were highest in South Korea, Canada, and Iceland (treatment >70%; control >50%), followed by the USA, Costa Rica, Germany, Portugal, and Taiwan. Treatment rates were less than 25% for women and less than 20% for men in Nepal, Indonesia, and some countries in sub-Saharan Africa and Oceania. Control rates were below 10% for women and men in these countries and for men in some countries in north Africa, central and south Asia, and eastern Europe. Treatment and control rates have improved in most countries since 1990, but we found little change in most countries in sub-Saharan Africa and Oceania. Improvements were largest in high-income countries, central Europe, and some upper-middle-income and recently high-income countries including Costa Rica, Taiwan, Kazakhstan, South Africa, Brazil, Chile, Turkey, and Iran. INTERPRETATION: Improvements in the detection, treatment, and control of hypertension have varied substantially across countries, with some middle-income countries now outperforming most high-income nations. The dual approach of reducing hypertension prevalence through primary prevention and enhancing its treatment and control is achievable not only in high-income countries but also in low-income and middle-income settings. FUNDING: WHO

Worldwide trends in hypertension prevalence and progress in treatment and control from 1990 to 2019: a pooled analysis of 1201 population-representative studies with 104 million participants

Background Hypertension can be detected at the primary health-care level and low-cost treatments can effectively control hypertension. We aimed to measure the prevalence of hypertension and progress in its detection, treatment, and control from 1990 to 2019 for 200 countries and territories. Methods We used data from 1990 to 2019 on people aged 30-79 years from population-representative studies with measurement of blood pressure and data on blood pressure treatment. We defined hypertension as having systolic blood pressure 140 mm Hg or greater, diastolic blood pressure 90 mm Hg or greater, or taking medication for hypertension. We applied a Bayesian hierarchical model to estimate the prevalence of hypertension and the proportion of people with hypertension who had a previous diagnosis (detection), who were taking medication for hypertension (treatment), and whose hypertension was controlled to below 140/90 mm Hg (control). The model allowed for trends over time to be non-linear and to vary by age. Findings The number of people aged 30-79 years with hypertension doubled from 1990 to 2019, from 331 (95% credible interval 306-359) million women and 317 (292-344) million men in 1990 to 626 (584-668) million women and 652 (604-698) million men in 2019, despite stable global age-standardised prevalence. In 2019, age-standardised hypertension prevalence was lowest in Canada and Peru for both men and women; in Taiwan, South Korea, Japan, and some countries in western Europe including Switzerland, Spain, and the UK for women; and in several low-income and middle-income countries such as Eritrea, Bangladesh, Ethiopia, and Solomon Islands for men. Hypertension prevalence surpassed 50% for women in two countries and men in nine countries, in central and eastern Europe, central Asia, Oceania, and Latin America. Globally, 59% (55-62) of women and 49% (46-52) of men with hypertension reported a previous diagnosis of hypertension in 2019, and 47% (43-51) of women and 38% (35-41) of men were treated. Control rates among people with hypertension in 2019 were 23% (20-27) for women and 18% (16-21) for men. In 2019, treatment and control rates were highest in South Korea, Canada, and Iceland (treatment >70%; control >50%), followed by the USA, Costa Rica, Germany, Portugal, and Taiwan. Treatment rates were less than 25% for women and less than 20% for men in Nepal, Indonesia, and some countries in sub-Saharan Africa and Oceania. Control rates were below 10% for women and men in these countries and for men in some countries in north Africa, central and south Asia, and eastern Europe. Treatment and control rates have improved in most countries since 1990, but we found little change in most countries in sub-Saharan Africa and Oceania. Improvements were largest in high-income countries, central Europe, and some upper-middle-income and recently high-income countries including Costa Rica, Taiwan, Kazakhstan, South Africa, Brazil, Chile, Turkey, and Iran. Interpretation Improvements in the detection, treatment, and control of hypertension have varied substantially across countries, with some middle-income countries now outperforming most high-income nations. The dual approach of reducing hypertension prevalence through primary prevention and enhancing its treatment and control is achievable not only in high-income countries but also in low-income and middle-income settings. Copyright (C) 2021 World Health Organization; licensee Elsevier

Worldwide trends in hypertension prevalence and progress in treatment and control from 1990 to 2019: a pooled analysis of 1201 population-representative studies with 104 million participants

Background Hypertension can be detected at the primary health-care level and low-cost treatments can effectively control hypertension. We aimed to measure the prevalence of hypertension and progress in its detection, treatment, and control from 1990 to 2019 for 200 countries and territories. Methods We used data from 1990 to 2019 on people aged 30–79 years from population-representative studies with measurement of blood pressure and data on blood pressure treatment. We defined hypertension as having systolic blood pressure 140 mm Hg or greater, diastolic blood pressure 90 mm Hg or greater, or taking medication for hypertension. We applied a Bayesian hierarchical model to estimate the prevalence of hypertension and the proportion of people with hypertension who had a previous diagnosis (detection), who were taking medication for hypertension (treatment), and whose hypertension was controlled to below 140/90 mm Hg (control). The model allowed for trends over time to be non-linear and to vary by age. Findings The number of people aged 30–79 years with hypertension doubled from 1990 to 2019, from 331 (95% credible interval 306–359) million women and 317 (292–344) million men in 1990 to 626 (584–668) million women and 652 (604–698) million men in 2019, despite stable global age-standardised prevalence. In 2019, age-standardised hypertension prevalence was lowest in Canada and Peru for both men and women; in Taiwan, South Korea, Japan, and some countries in western Europe including Switzerland, Spain, and the UK for women; and in several low-income and middle-income countries such as Eritrea, Bangladesh, Ethiopia, and Solomon Islands for men. Hypertension prevalence surpassed 50% for women in two countries and men in nine countries, in central and eastern Europe, central Asia, Oceania, and Latin America. Globally, 59% (55–62) of women and 49% (46–52) of men with hypertension reported a previous diagnosis of hypertension in 2019, and 47% (43–51) of women and 38% (35–41) of men were treated. Control rates among people with hypertension in 2019 were 23% (20–27) for women and 18% (16–21) for men. In 2019, treatment and control rates were highest in South Korea, Canada, and Iceland (treatment >70%; control >50%), followed by the USA, Costa Rica, Germany, Portugal, and Taiwan. Treatment rates were less than 25% for women and less than 20% for men in Nepal, Indonesia, and some countries in sub-Saharan Africa and Oceania. Control rates were below 10% for women and men in these countries and for men in some countries in north Africa, central and south Asia, and eastern Europe. Treatment and control rates have improved in most countries since 1990, but we found little change in most countries in sub-Saharan Africa and Oceania. Improvements were largest in high-income countries, central Europe, and some upper-middle-income and recently high-income countries including Costa Rica, Taiwan, Kazakhstan, South Africa, Brazil, Chile, Turkey, and Iran. Interpretation Improvements in the detection, treatment, and control of hypertension have varied substantially across countries, with some middle-income countries now outperforming most high-income nations. The dual approach of reducing hypertension prevalence through primary prevention and enhancing its treatment and control is achievable not only in high-income countries but also in low-income and middle-income settings

Worldwide trends in hypertension prevalence and progress in treatment and control from 1990 to 2019: a pooled analysis of 1201 population-representative studies with 104 million participants

Background Hypertension can be detected at the primary health-care level and low-cost treatments can effectively control hypertension. We aimed to measure the prevalence of hypertension and progress in its detection, treatment, and control from 1990 to 2019 for 200 countries and territories. Methods We used data from 1990 to 2019 on people aged 30–79 years from population-representative studies with measurement of blood pressure and data on blood pressure treatment. We defined hypertension as having systolic blood pressure 140 mm Hg or greater, diastolic blood pressure 90 mm Hg or greater, or taking medication for hypertension. We applied a Bayesian hierarchical model to estimate the prevalence of hypertension and the proportion of people with hypertension who had a previous diagnosis (detection), who were taking medication for hypertension (treatment), and whose hypertension was controlled to below 140/90 mm Hg (control). The model allowed for trends over time to be non-linear and to vary by age. Findings The number of people aged 30–79 years with hypertension doubled from 1990 to 2019, from 331 (95% credible interval 306–359) million women and 317 (292–344) million men in 1990 to 626 (584–668) million women and 652 (604–698) million men in 2019, despite stable global age-standardised prevalence. In 2019, age-standardised hypertension prevalence was lowest in Canada and Peru for both men and women; in Taiwan, South Korea, Japan, and some countries in western Europe including Switzerland, Spain, and the UK for women; and in several low-income and middle-income countries such as Eritrea, Bangladesh, Ethiopia, and Solomon Islands for men. Hypertension prevalence surpassed 50% for women in two countries and men in nine countries, in central and eastern Europe, central Asia, Oceania, and Latin America. Globally, 59% (55–62) of women and 49% (46–52) of men with hypertension reported a previous diagnosis of hypertension in 2019, and 47% (43–51) of women and 38% (35–41) of men were treated. Control rates among people with hypertension in 2019 were 23% (20–27) for women and 18% (16–21) for men. In 2019, treatment and control rates were highest in South Korea, Canada, and Iceland (treatment >70%; control >50%), followed by the USA, Costa Rica, Germany, Portugal, and Taiwan. Treatment rates were less than 25% for women and less than 20% for men in Nepal, Indonesia, and some countries in sub-Saharan Africa and Oceania. Control rates were below 10% for women and men in these countries and for men in some countries in north Africa, central and south Asia, and eastern Europe. Treatment and control rates have improved in most countries since 1990, but we found little change in most countries in sub-Saharan Africa and Oceania. Improvements were largest in high-income countries, central Europe, and some upper-middle-income and recently high-income countries including Costa Rica, Taiwan, Kazakhstan, South Africa, Brazil, Chile, Turkey, and Iran. Interpretation Improvements in the detection, treatment, and control of hypertension have varied substantially across countries, with some middle-income countries now outperforming most high-income nations. The dual approach of reducing hypertension prevalence through primary prevention and enhancing its treatment and control is achievable not only in high-income countries but also in low-income and middle-income settings

Análise cinemática do setor de junção entre as zonas de cisalhamento direcionais São Bento do Sapucai, Sertãozinho e Jundiuvira, nas imediações de Piracaia-SP

O setor centro-leste do Estado de São Paulo é caracterizado por um importante sistema de falhas transcorrentes que se constitui na feição mais visível da Faixa Ribeira. O objetivo deste trabalho é compreender a evolução cinemática de uma área atravessada por três destas zonas de cisalhamento direcionais: São Bento do Sapucaí (ZCSBS), Sertãozinho (ZCS) e Jundiuvira (ZCJ). As rochas mapeadas foram individualizadas nas seguintes unidades. Complexo Piracaia, constituído por paragnaisses e xistos a granada localmente migmatizados, Grupo Serra do Itaberaba, seqüência metavulcano-sedimentar com sillimanita-xistos, biotita-xistos, quartzitos, sericita-filitos e metabásicas e Grupo São Roque, formado por metarenitos a metargilitos. Estes terrenos são intrudidos por ortognaisses de composição granítica-granodiorítica (Serra do Barro Branco) a granítica (Serra do Mato Mole) e por vários corpos granitóides menores. A movimentação das zonas de cisalhamento direcionais foi responsável pela geração da foliação mais persistente na área (Sn milonítica), orientada preferencialmente NE, e plano axial a dobras apertadas a isoclinais em superfícies S(n-1). A similaridade mineralógica entre os dois planos sugere uma evolução progressiva sobre a própria foliação milonítica principal. Esta foliação é modificada localmente por clivagens S(n+1), tardias ou posteriores ao seu desenvolvimento e plano-axiais a dobras assimétricas com vergência para NW. O deslocamento sinistral das zonas de cisalhamento São Bento do Sapucaí e Sertãozinho gerou movimentos laterais oblíquos divergentes essencialmente subhorizontais, responsáveis pelo desenvolvimento de uma estrutura em flor negativa (na ZCSBS) que perrnitiu o abatimento de rochas de grau mais baixo e provavelmente a colocação de corpos graníticos (Serra do Mato Mole). A movimentação destral posterior da ZCJ gerou domínios transtrativos, preenchidos por metassedimentos, e transpressivos, responsáveis por compressão generalizada para NW e pelo desenvolvimento de grande parte das estruturas S(n+1). Esta inversão tectônica foi acompanhada de redução na temperatura em toda a área. Com base nos estudos de orientação preferencial cristalográfica (OPC) de eixos-C de quartzo foi possível a individualização de dois setores, caracterizados, respectivamente, por deformação não-coaxial (cisalhamento simples) e deformação não-coaxial associada a achatamento (transpressão). Estes setores estão relacionados com os limites do domínio transpressivo da ZCJ, cujos padrões de OPC sugerem ainda redução na temperatura de deformação das bordas para o centro.The middle-eastern part of the State of São Paulo is characterised by a transcurrent fault system that is the most visible feature of the Ribeira Belt. The aim of this research is to understand the kinematic evolution of an area cross-cut by three of these strike-slip shear zones (SZ): São Bento do Sapucaí (SBSSZ), Sertãozinho (SSZ) and Jundiuvira (JSZ).Field data allowed identification of the following units: Piracaia Complex, composed of paragneissic rocks and locally migmatized garnet schists; Serra do Itaberaba Group, a metavolcanic-sedimentary sequence that includes sillimanite-schists, biotite-schists, quartzites, sericite-filites and metabasic rocks; and São Roque Group, made up of metasandstones to metamudstones. These terrains are intruded by orthogneissic rocks of granitic-granodioritic (Serra do Barro Branco) to granitic (Serra do Mato Mole) composition and by several small granitic bodies.Displacement along these shear zones has generated the most penetrative planar structure in the area, an axial-plane foliation (milonitic, called Sn) to tight to isoclinal folds of S(n-1) surfaces, oriented mostly NE. The mineralogical resemblance between the two planes suggests a progressive evolution of the main milonitic foliation. It is locally modified by late to post S(n+1) axial-plane cleavages to asymmetric, northwest-verging folds. A sinistral sense of shear, identified in the São Bento do Sapucaí and Sertãozinho shear zones, produced mainly horizontal, divergent oblique lateral movements, by which a negative flower structure evolved (SBSSZ), leading to the subsidence of low-grade metasedimentary blocks and emplacement of granitic bodies (Serra do Mato Mole). The late dextral shear movement of the JSZ gave rise to transtensile domains, occupied by metasedimentary rocks, and transpressive domains, which led to a general compression toward the NW and to the development of the S(n+1) structures. This tectonic inversion was accompanied by a temperature reduction in the whole area. On the basis of lattice preferred orientation (LPO) analysis of quartz C-axes it was possible to identify two main sectors, which are characterised, respectively, by non-coaxial deformation (simple shear) and non-coaxial deformation fallowed by flattening (transpression). These sectors are related to the limits of the JSZ transpressive domain, in which the LPO patterns also suggest a decrease in the temperature of deformation from the boundaries to the centre

Associações metamórficas de alta pressão: nappes neoproterozóicas a sul do Cráton São Francisco

A área estudada é caracterizada por um conjunto de unidades estruturalmente relacionadas transportadas grosseiramente para E-NE em direção à borda sul do Cráton São Francisco. A Nappe Socorro-Guaxupé (NSG), a oeste, representa a unidade mais superior, sendo composta por assembléias minerais nas facies anfibolito e granulito que mostram uma trajetória P-T compatível com uma evolução metamórfica inicial envolvendo magmatismo na base da crosta antes e durante seu soterramento. Este gradiente térmico anômalo foi responsável pela geração de metamorfismo granulítico anidro, sugestão corroborada pela heterogeneidade das composições isotópicas de oxigênio. As unidades subjacentes ocorrem como uma grande pilha metassedimentar organizada como uma nappe superior formada por Ky/Sill granulitos (Nappe Três Pontas-Varginha - NTPV), na qual um padrão metamórfico invertido foi reconhecido, e uma nappe inferior constiruída por Ky xistos e gnaisses (Nappe Carmo Cachoeira - NCC), separados por uma descontinuidade tectônica. Na NTPV, trajetórias P-T tipo IBC horárias, típicas de ambientes colisionais, foram definidas para os Ky e Sill granulitos. Os Ky granulitos basais mostram uma trajetória no campo de estabilidade da Ky, enquanto os dados para os Sill granulitos superiores sugerem uma evolução próxima ao limite Sill/Ky, fato que ilustra as diferenças entre a evolução metamórfica dos dois tipos de granulitos e demonstra as condições de temperatura decrescentes em direção à base da unidade. Na NCC a trajetória tipo ITD exibe uma tendência para a depressão das paleogeotermas em direção às temperaturas mais baixas, o que está relacionado ao underthrusting de litosfera fria em zonas de subducção. As diferenças verificadas entre as trajetórias P-T da NTPV e NCC podem ser o resultado do espessamento crustal que normalmente acompanha um episódio de subducção. Os contrastes entre os valores de \'delta POT. 18\'O da NTPV e NCC, além das diferenças internas entre as amostras e as fases minerais, são consistentes com a preservação da composição isotópica anterior ao metamorfismo, e sugerem uma fonte altamente heterogênea para estas rochas. Dados litoquímicos nestes metassedimentos confirmam esta afirmação. As baixas razões A/R (0,6-0,9) nas rochas cálciossilicáticas da NTPV indicam que a milonitização ocorreu sob condições quase anidras, e processos aquosos tiveram um papel apenas secundário. As relativamente pequenas diferenças observadas nos valores \'delta POT. 18\'O do espécime cálciossilicático indeformado para o deformado (\'DA ORDEM DE\' 1,6%o) sugere que a composição isotópica do fluido associado aos processos de milonitização era muito semelhante àquele em equilíbrio com a assembléia metamórfica. Estimativas da composição isotópica de oxigênio nos equivalentes indeformados e inalterados da NTPV e NCC apontam para valores de \'delta POT. 18\'O de até 18%o. A comparação entre estes valores e aqueles obtidos nas rochas granitóides do embasamento (8,267-8,490%o) exclui a possibilidade destes últimos serem possíveis fontes para os metapelitos. A NCC superpõe-se, a nordeste, a uma seqüência quartzítica e a metassedimentos de baixo grau, e a oeste a rochas do embasamento, parte do Cráton São Francisco. As temperaturas isotópicas de oxigênio mostram uma redução em direção à base do pacote como um todo, o que é consistente com o padrão metamórfico invertido previamente reconhecido. O contato tectônico da unidade mais basal e o embasamento é caracterizado por um alto gradiente de temperatura, sugerindo que cavalgamento sob baixa temperatura tenha atuado como processo tectônico dominante.The area studied is characterised by a set of structurally related units roughly transported to E-NE towards the southern edge of the São Francisco Craton. The Socorro-Guaxupé Nappe (SGN) represents the western and uppermost terrain made up of both amphibolite and granulite facies mineral assemblages, showing a P-T trajectory compatible with an initial metamorphic evolution involving magmatic heating of the lower crust before and during its burial. This anomalous thermal gradient generated water-absent granulitic metamorphism, a suggestion also indicated by the heterogeneous oxygen isotopic compositions. The underlying units occur as a large metasedimentary pile structurally organised as an upper Ky/Sill-bearing granulitic Três Pontas-Varginha Nappe (TPVN), in which an inverted metamorphic pattern was recognised, and a lower Ky-bearing schistose and gneissic Carmo da Cachoeira Nappe (CCN), separated by a tectonic discontinuity. In the TPVN, crockwise, IBC-type P-T paths typical in many collisional settings were defined for both Ky- and Sill-type granulites. The entire basal Ky granulites trajectory lies in the Ky stability field, whilst data from the upper Sill granulites suggest an evolution towards the Sill/Ky boundary. These distinct paths testify the differences between the metamorphic evolution of the two types of granulites, and demonstrate the decreasing temperature conditions towards the base of the unit. In the CCN the ITD-type P-T path exhibits a tendency for the depression of the paleogeotherm pattern toward lower temperatures related to underthrusting of cold lithosphere in subduction zones. The differences verified between the TPVN and CCN P-T paths may result from the normal thickening event that follows a subduction episode. The contrasts between the \'delta POT. 18\'O values from TPVN and CCN, as well as the internal differences among both samples and mineral phases, are consistent with a general preservation of isotopic composition prior to metamorphism, and argue for a highly heterogeneous source for these rocks. Lithochemical data on these metasediments corroborate this suggestion The low TPVN calc-silicate W/R ratios (0.6-0.9) indicate that mylonitisation occurred under prevalent rock-dominated conditions, and fluid-related processes played only a minor role. The relatively small differences observed in the \'delta POT. 180\'O values from the undeformed to the deformed calc-silicate specimen (\'DA ORDEM DE\' 1.6%o) suggest that the \'delta POT. 18\'O composition of the fluid associated with the mylonitisation processes was close to that in equilibrium with the metamorphic assemblage. Estimation of the oxygen isotopic composition of both TPVN undeformed and CCN unaltered equivalents points to \'delta POT. 18\'O values of up to 18%o. Comparison between these values and those achieved from the basement granitoid rocks (8.267 -8.490%o) argues against the latter as possible sources for the metapelites. To the north, the CCN lays over a quartzitic sequence superposed, in its eastern portion, on low-grade metasediments, and in the west on rocks from the basement, part of the São Francisco Craton. Oxygen isotope thermometry shows a temperature decrease towards the base of the whole system, which is consistent with the previously recognised inverted metamorphic pattern. The tectonic contact of the most basal unit and the basement is characterised by a steep temperature gradient suggesting low-temperature thrusting acting as a dominant tectonic process

Associações metamórficas de alta pressão: nappes neoproterozóicas a sul do Cráton São Francisco

A área estudada é caracterizada por um conjunto de unidades estruturalmente relacionadas transportadas grosseiramente para E-NE em direção à borda sul do Cráton São Francisco. A Nappe Socorro-Guaxupé (NSG), a oeste, representa a unidade mais superior, sendo composta por assembléias minerais nas facies anfibolito e granulito que mostram uma trajetória P-T compatível com uma evolução metamórfica inicial envolvendo magmatismo na base da crosta antes e durante seu soterramento. Este gradiente térmico anômalo foi responsável pela geração de metamorfismo granulítico anidro, sugestão corroborada pela heterogeneidade das composições isotópicas de oxigênio. As unidades subjacentes ocorrem como uma grande pilha metassedimentar organizada como uma nappe superior formada por Ky/Sill granulitos (Nappe Três Pontas-Varginha - NTPV), na qual um padrão metamórfico invertido foi reconhecido, e uma nappe inferior constiruída por Ky xistos e gnaisses (Nappe Carmo Cachoeira - NCC), separados por uma descontinuidade tectônica. Na NTPV, trajetórias P-T tipo IBC horárias, típicas de ambientes colisionais, foram definidas para os Ky e Sill granulitos. Os Ky granulitos basais mostram uma trajetória no campo de estabilidade da Ky, enquanto os dados para os Sill granulitos superiores sugerem uma evolução próxima ao limite Sill/Ky, fato que ilustra as diferenças entre a evolução metamórfica dos dois tipos de granulitos e demonstra as condições de temperatura decrescentes em direção à base da unidade. Na NCC a trajetória tipo ITD exibe uma tendência para a depressão das paleogeotermas em direção às temperaturas mais baixas, o que está relacionado ao underthrusting de litosfera fria em zonas de subducção. As diferenças verificadas entre as trajetórias P-T da NTPV e NCC podem ser o resultado do espessamento crustal que normalmente acompanha um episódio de subducção. Os contrastes entre os valores de \'delta POT. 18\'O da NTPV e NCC, além das diferenças internas entre as amostras e as fases minerais, são consistentes com a preservação da composição isotópica anterior ao metamorfismo, e sugerem uma fonte altamente heterogênea para estas rochas. Dados litoquímicos nestes metassedimentos confirmam esta afirmação. As baixas razões A/R (0,6-0,9) nas rochas cálciossilicáticas da NTPV indicam que a milonitização ocorreu sob condições quase anidras, e processos aquosos tiveram um papel apenas secundário. As relativamente pequenas diferenças observadas nos valores \'delta POT. 18\'O do espécime cálciossilicático indeformado para o deformado (\'DA ORDEM DE\' 1,6%o) sugere que a composição isotópica do fluido associado aos processos de milonitização era muito semelhante àquele em equilíbrio com a assembléia metamórfica. Estimativas da composição isotópica de oxigênio nos equivalentes indeformados e inalterados da NTPV e NCC apontam para valores de \'delta POT. 18\'O de até 18%o. A comparação entre estes valores e aqueles obtidos nas rochas granitóides do embasamento (8,267-8,490%o) exclui a possibilidade destes últimos serem possíveis fontes para os metapelitos. A NCC superpõe-se, a nordeste, a uma seqüência quartzítica e a metassedimentos de baixo grau, e a oeste a rochas do embasamento, parte do Cráton São Francisco. As temperaturas isotópicas de oxigênio mostram uma redução em direção à base do pacote como um todo, o que é consistente com o padrão metamórfico invertido previamente reconhecido. O contato tectônico da unidade mais basal e o embasamento é caracterizado por um alto gradiente de temperatura, sugerindo que cavalgamento sob baixa temperatura tenha atuado como processo tectônico dominante.The area studied is characterised by a set of structurally related units roughly transported to E-NE towards the southern edge of the São Francisco Craton. The Socorro-Guaxupé Nappe (SGN) represents the western and uppermost terrain made up of both amphibolite and granulite facies mineral assemblages, showing a P-T trajectory compatible with an initial metamorphic evolution involving magmatic heating of the lower crust before and during its burial. This anomalous thermal gradient generated water-absent granulitic metamorphism, a suggestion also indicated by the heterogeneous oxygen isotopic compositions. The underlying units occur as a large metasedimentary pile structurally organised as an upper Ky/Sill-bearing granulitic Três Pontas-Varginha Nappe (TPVN), in which an inverted metamorphic pattern was recognised, and a lower Ky-bearing schistose and gneissic Carmo da Cachoeira Nappe (CCN), separated by a tectonic discontinuity. In the TPVN, crockwise, IBC-type P-T paths typical in many collisional settings were defined for both Ky- and Sill-type granulites. The entire basal Ky granulites trajectory lies in the Ky stability field, whilst data from the upper Sill granulites suggest an evolution towards the Sill/Ky boundary. These distinct paths testify the differences between the metamorphic evolution of the two types of granulites, and demonstrate the decreasing temperature conditions towards the base of the unit. In the CCN the ITD-type P-T path exhibits a tendency for the depression of the paleogeotherm pattern toward lower temperatures related to underthrusting of cold lithosphere in subduction zones. The differences verified between the TPVN and CCN P-T paths may result from the normal thickening event that follows a subduction episode. The contrasts between the \'delta POT. 18\'O values from TPVN and CCN, as well as the internal differences among both samples and mineral phases, are consistent with a general preservation of isotopic composition prior to metamorphism, and argue for a highly heterogeneous source for these rocks. Lithochemical data on these metasediments corroborate this suggestion The low TPVN calc-silicate W/R ratios (0.6-0.9) indicate that mylonitisation occurred under prevalent rock-dominated conditions, and fluid-related processes played only a minor role. The relatively small differences observed in the \'delta POT. 180\'O values from the undeformed to the deformed calc-silicate specimen (\'DA ORDEM DE\' 1.6%o) suggest that the \'delta POT. 18\'O composition of the fluid associated with the mylonitisation processes was close to that in equilibrium with the metamorphic assemblage. Estimation of the oxygen isotopic composition of both TPVN undeformed and CCN unaltered equivalents points to \'delta POT. 18\'O values of up to 18%o. Comparison between these values and those achieved from the basement granitoid rocks (8.267 -8.490%o) argues against the latter as possible sources for the metapelites. To the north, the CCN lays over a quartzitic sequence superposed, in its eastern portion, on low-grade metasediments, and in the west on rocks from the basement, part of the São Francisco Craton. Oxygen isotope thermometry shows a temperature decrease towards the base of the whole system, which is consistent with the previously recognised inverted metamorphic pattern. The tectonic contact of the most basal unit and the basement is characterised by a steep temperature gradient suggesting low-temperature thrusting acting as a dominant tectonic process

Análise cinemática do setor de junção entre as zonas de cisalhamento direcionais São Bento do Sapucai, Sertãozinho e Jundiuvira, nas imediações de Piracaia-SP

O setor centro-leste do Estado de São Paulo é caracterizado por um importante sistema de falhas transcorrentes que se constitui na feição mais visível da Faixa Ribeira. O objetivo deste trabalho é compreender a evolução cinemática de uma área atravessada por três destas zonas de cisalhamento direcionais: São Bento do Sapucaí (ZCSBS), Sertãozinho (ZCS) e Jundiuvira (ZCJ). As rochas mapeadas foram individualizadas nas seguintes unidades. Complexo Piracaia, constituído por paragnaisses e xistos a granada localmente migmatizados, Grupo Serra do Itaberaba, seqüência metavulcano-sedimentar com sillimanita-xistos, biotita-xistos, quartzitos, sericita-filitos e metabásicas e Grupo São Roque, formado por metarenitos a metargilitos. Estes terrenos são intrudidos por ortognaisses de composição granítica-granodiorítica (Serra do Barro Branco) a granítica (Serra do Mato Mole) e por vários corpos granitóides menores. A movimentação das zonas de cisalhamento direcionais foi responsável pela geração da foliação mais persistente na área (Sn milonítica), orientada preferencialmente NE, e plano axial a dobras apertadas a isoclinais em superfícies S(n-1). A similaridade mineralógica entre os dois planos sugere uma evolução progressiva sobre a própria foliação milonítica principal. Esta foliação é modificada localmente por clivagens S(n+1), tardias ou posteriores ao seu desenvolvimento e plano-axiais a dobras assimétricas com vergência para NW. O deslocamento sinistral das zonas de cisalhamento São Bento do Sapucaí e Sertãozinho gerou movimentos laterais oblíquos divergentes essencialmente subhorizontais, responsáveis pelo desenvolvimento de uma estrutura em flor negativa (na ZCSBS) que perrnitiu o abatimento de rochas de grau mais baixo e provavelmente a colocação de corpos graníticos (Serra do Mato Mole). A movimentação destral posterior da ZCJ gerou domínios transtrativos, preenchidos por metassedimentos, e transpressivos, responsáveis por compressão generalizada para NW e pelo desenvolvimento de grande parte das estruturas S(n+1). Esta inversão tectônica foi acompanhada de redução na temperatura em toda a área. Com base nos estudos de orientação preferencial cristalográfica (OPC) de eixos-C de quartzo foi possível a individualização de dois setores, caracterizados, respectivamente, por deformação não-coaxial (cisalhamento simples) e deformação não-coaxial associada a achatamento (transpressão). Estes setores estão relacionados com os limites do domínio transpressivo da ZCJ, cujos padrões de OPC sugerem ainda redução na temperatura de deformação das bordas para o centro.The middle-eastern part of the State of São Paulo is characterised by a transcurrent fault system that is the most visible feature of the Ribeira Belt. The aim of this research is to understand the kinematic evolution of an area cross-cut by three of these strike-slip shear zones (SZ): São Bento do Sapucaí (SBSSZ), Sertãozinho (SSZ) and Jundiuvira (JSZ).Field data allowed identification of the following units: Piracaia Complex, composed of paragneissic rocks and locally migmatized garnet schists; Serra do Itaberaba Group, a metavolcanic-sedimentary sequence that includes sillimanite-schists, biotite-schists, quartzites, sericite-filites and metabasic rocks; and São Roque Group, made up of metasandstones to metamudstones. These terrains are intruded by orthogneissic rocks of granitic-granodioritic (Serra do Barro Branco) to granitic (Serra do Mato Mole) composition and by several small granitic bodies.Displacement along these shear zones has generated the most penetrative planar structure in the area, an axial-plane foliation (milonitic, called Sn) to tight to isoclinal folds of S(n-1) surfaces, oriented mostly NE. The mineralogical resemblance between the two planes suggests a progressive evolution of the main milonitic foliation. It is locally modified by late to post S(n+1) axial-plane cleavages to asymmetric, northwest-verging folds. A sinistral sense of shear, identified in the São Bento do Sapucaí and Sertãozinho shear zones, produced mainly horizontal, divergent oblique lateral movements, by which a negative flower structure evolved (SBSSZ), leading to the subsidence of low-grade metasedimentary blocks and emplacement of granitic bodies (Serra do Mato Mole). The late dextral shear movement of the JSZ gave rise to transtensile domains, occupied by metasedimentary rocks, and transpressive domains, which led to a general compression toward the NW and to the development of the S(n+1) structures. This tectonic inversion was accompanied by a temperature reduction in the whole area. On the basis of lattice preferred orientation (LPO) analysis of quartz C-axes it was possible to identify two main sectors, which are characterised, respectively, by non-coaxial deformation (simple shear) and non-coaxial deformation fallowed by flattening (transpression). These sectors are related to the limits of the JSZ transpressive domain, in which the LPO patterns also suggest a decrease in the temperature of deformation from the boundaries to the centre