Protolith age of Santa Maria Chico granulites dated on zircons from an associated amphibolite-facies granodiorite in southernmost Brazil
U-Pb dating of zircon was undertaken with the Beijing SHRIMP II (sensitive high resolution ion microprobe) on anamphibolite facies granodiorite and an almandine-albite granulite from the Santa Maria Chico Granulitic Complex, southern Brazilian Shield. This work was also done to unravel protolith age...
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Academia Brasileira de Ciências
2008-09-01
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| Series: | Anais da Academia Brasileira de Ciências |
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| Online Access: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652008000300014 |
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| author | Léo A. Hartmann Dunyi Liu Yenbin Wang Hans-Joachim Massonne João O.S. Santos |
| author_facet | Léo A. Hartmann Dunyi Liu Yenbin Wang Hans-Joachim Massonne João O.S. Santos |
| author_sort | Léo A. Hartmann |
| collection | DOAJ |
| description | U-Pb dating of zircon was undertaken with the Beijing SHRIMP II (sensitive high resolution ion microprobe) on anamphibolite facies granodiorite and an almandine-albite granulite from the Santa Maria Chico Granulitic Complex, southern Brazilian Shield. This work was also done to unravel protolith ages which are often hidden in the array of partly reset data. The obtained metamorphic ages of the granodiorite gneiss and the granulite are 2035 ± 9 Ma and 2006 ± 3 Ma, respectively. These data are within the range of metamorphic ages determined in previous studies (2022 ± 18 Ma and 2031 ± 40 Ma). However, protolith ages for the granodiorite (2366 ± 8 Ma) and the granulite (2489 ± 6 Ma) were obtained which are outside the previously recognized range (> 2510-2555 Ma). The magmatic protolith age of the granodiorite refers to a previously little known magmatic event in the shield. Further investigations may demonstrate that amphibolite facies zircon crystals are useful as a window into geological events in associated granulites, because zircon ages are blurred in the studied granulites.<br>Um granodiorito de fácies anfibolito e um almandina-albita granulito do Complexo Granulítico Santa Maria Chico, porção sul do Escudo Brasileiro, foram datados pelo método U-Pb em zircão por Beijing SHRIMP II (sensitive high resolution ion microprobe). Esta investigação inclui a determinação das idades de protólitos que estão ocultas no conjunto de dados parcialmente re-equilibrados. As idades metamórficas obtidas no gnaisse granodiorítico e no granulito são 2035 ±9 Ma e 2006 ±3 Ma, respectivamente. Esses dados estão dentro da variação das idades metamórficas determinadas em estudos anteriores (2022 ±18 Ma e 2031 ±40 Ma). No entanto, as idades do protólito do granodiorito (2366 ±8 Ma) e do granulito (2489 ±6 Ma) estão fora da variação de idades ( > 2510-2555 Ma) reconhecidas anteriormente. A idade magmática do protólito do granodiorito corresponde a uma idade pouco conhecida anteriormente no escudo. Estudos adicionais podem demonstrar que cristais de zircão de fácies anfibolito são úteis como janelas para o entendimento de eventos geológicos em granulitos associados, pois as idades de zircão nos granulitos estudados encontram-se obscurecidas por recristalização. |
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| language | English |
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| spelling | doaj.art-d4a5021a930948ca8ee228c96e60fd672022-12-22T00:41:04ZengAcademia Brasileira de CiênciasAnais da Academia Brasileira de Ciências0001-37651678-26902008-09-0180354355110.1590/S0001-37652008000300014Protolith age of Santa Maria Chico granulites dated on zircons from an associated amphibolite-facies granodiorite in southernmost BrazilLéo A. HartmannDunyi LiuYenbin WangHans-Joachim MassonneJoão O.S. SantosU-Pb dating of zircon was undertaken with the Beijing SHRIMP II (sensitive high resolution ion microprobe) on anamphibolite facies granodiorite and an almandine-albite granulite from the Santa Maria Chico Granulitic Complex, southern Brazilian Shield. This work was also done to unravel protolith ages which are often hidden in the array of partly reset data. The obtained metamorphic ages of the granodiorite gneiss and the granulite are 2035 ± 9 Ma and 2006 ± 3 Ma, respectively. These data are within the range of metamorphic ages determined in previous studies (2022 ± 18 Ma and 2031 ± 40 Ma). However, protolith ages for the granodiorite (2366 ± 8 Ma) and the granulite (2489 ± 6 Ma) were obtained which are outside the previously recognized range (> 2510-2555 Ma). The magmatic protolith age of the granodiorite refers to a previously little known magmatic event in the shield. Further investigations may demonstrate that amphibolite facies zircon crystals are useful as a window into geological events in associated granulites, because zircon ages are blurred in the studied granulites.<br>Um granodiorito de fácies anfibolito e um almandina-albita granulito do Complexo Granulítico Santa Maria Chico, porção sul do Escudo Brasileiro, foram datados pelo método U-Pb em zircão por Beijing SHRIMP II (sensitive high resolution ion microprobe). Esta investigação inclui a determinação das idades de protólitos que estão ocultas no conjunto de dados parcialmente re-equilibrados. As idades metamórficas obtidas no gnaisse granodiorítico e no granulito são 2035 ±9 Ma e 2006 ±3 Ma, respectivamente. Esses dados estão dentro da variação das idades metamórficas determinadas em estudos anteriores (2022 ±18 Ma e 2031 ±40 Ma). No entanto, as idades do protólito do granodiorito (2366 ±8 Ma) e do granulito (2489 ±6 Ma) estão fora da variação de idades ( > 2510-2555 Ma) reconhecidas anteriormente. A idade magmática do protólito do granodiorito corresponde a uma idade pouco conhecida anteriormente no escudo. Estudos adicionais podem demonstrar que cristais de zircão de fácies anfibolito são úteis como janelas para o entendimento de eventos geológicos em granulitos associados, pois as idades de zircão nos granulitos estudados encontram-se obscurecidas por recristalização.http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652008000300014idade de protólitoPaleoproterozóicogeocronologia de zircãoComplexo Granulítico Santa Maria ChicoSHRIMPprotolith agePaleoproterozoiczircon geochronologySanta Maria Chico Granulitic ComplexSHRIMP |
| spellingShingle | Léo A. Hartmann Dunyi Liu Yenbin Wang Hans-Joachim Massonne João O.S. Santos Protolith age of Santa Maria Chico granulites dated on zircons from an associated amphibolite-facies granodiorite in southernmost Brazil Anais da Academia Brasileira de Ciências idade de protólito Paleoproterozóico geocronologia de zircão Complexo Granulítico Santa Maria Chico SHRIMP protolith age Paleoproterozoic zircon geochronology Santa Maria Chico Granulitic Complex SHRIMP |
| title | Protolith age of Santa Maria Chico granulites dated on zircons from an associated amphibolite-facies granodiorite in southernmost Brazil |
| title_full | Protolith age of Santa Maria Chico granulites dated on zircons from an associated amphibolite-facies granodiorite in southernmost Brazil |
| title_fullStr | Protolith age of Santa Maria Chico granulites dated on zircons from an associated amphibolite-facies granodiorite in southernmost Brazil |
| title_full_unstemmed | Protolith age of Santa Maria Chico granulites dated on zircons from an associated amphibolite-facies granodiorite in southernmost Brazil |
| title_short | Protolith age of Santa Maria Chico granulites dated on zircons from an associated amphibolite-facies granodiorite in southernmost Brazil |
| title_sort | protolith age of santa maria chico granulites dated on zircons from an associated amphibolite facies granodiorite in southernmost brazil |
| topic | idade de protólito Paleoproterozóico geocronologia de zircão Complexo Granulítico Santa Maria Chico SHRIMP protolith age Paleoproterozoic zircon geochronology Santa Maria Chico Granulitic Complex SHRIMP |
| url | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652008000300014 |
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