Sm-Nd age of the fazenda brasileiro gabbro, Bahia, Brazil: example of robust behavior of the Sm-Nd isotopic system under extreme hydrothermal alteration
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| Natura: | Artículo científico |
| Lingua: | en |
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Academia Brasileira de Ciências
2003
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| _version_ | 1876489041034084352 |
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| author | Maria da Glória Silva |
| author_facet | Maria da Glória Silva |
| contents | Sm-Nd age of the fazenda brasileiro gabbro, Bahia, Brazil: example of robust behavior of the Sm-Nd isotopic system under extreme hydrothermal alteration Maria da Glória Silva Márcio M. Pimentel Multidisciplinaria (Ciencias Naturales y Exactas) Sm Nd Paleoproterozoic Fazenda Brasileiro gold mineralization The Fazenda Brasileiro gold mineralization is hosted by a gabbroic sill, intrusive into metavolcanicmetasedimentaryrocks of the Rio Itapicuru Greenstone Belt, São Francisco Craton. The 2.05 Ga old mineralizationis associated with intense shearing and hydrothermal alteration, and the host gabbro is altered to aseries of rocks rich in sericite, chlorite, actinolite, carbonate and quartz.Twelve whole-rock samples of the gold mineralization, representing varied degrees of alteration, from rockswith preserved igneous textures to the ore (quartz-carbonate-sulfide-chlorite), were studied by the Sm-Ndmethod. All analytical points resulted in an isochron (MSWD = 1.9) indicating the age of 2142 +/ 47 Ma(1s) and Epsilon Nd (T) of +1.2. Chlorite-sericite-carbonate rich hydrothermal rocks indicate the age of 2148+/ 57 Ma and Epsilon Nd (T) of +1.1. The positive Epsilon Nd (T) suggest limited or no contaminationwith older continental crust, compatible with an oceanic setting for the tholeiites.Combined withREEdata, the Sm-Nd isotopic results reveal that the hydrothermal alteration, although intense,was unable to alter significantly the Sm/Nd ratios of the original igneous rocks and did not cause importantscatter of the analytical points, providing a rare example of robust behavior of the isotopic system, even underintense hydrothermal alteration. 2003 artículo científico 0001-3765 https://www.redalyc.org/articulo.oa?id=32775309 en http://www.redalyc.org/revista.oa?id=327 Anais da Academia Brasileira de Ciências application/pdf Academia Brasileira de Ciências Anais da Academia Brasileira de Ciências (Brasil) Num.3 Vol.75 |
| format | Artículo científico |
| id | redalyc_32775309 |
| institution | Redalyc |
| language | en |
| publishDate | 2003 |
| publisher | Academia Brasileira de Ciências |
| spellingShingle | Sm-Nd age of the fazenda brasileiro gabbro, Bahia, Brazil: example of robust behavior of the Sm-Nd isotopic system under extreme hydrothermal alteration Maria da Glória Silva Multidisciplinaria (Ciencias Naturales y Exactas) Sm Nd Paleoproterozoic Fazenda Brasileiro gold mineralization Sm-Nd age of the fazenda brasileiro gabbro, Bahia, Brazil: example of robust behavior of the Sm-Nd isotopic system under extreme hydrothermal alteration Maria da Glória Silva Márcio M. Pimentel Multidisciplinaria (Ciencias Naturales y Exactas) Sm Nd Paleoproterozoic Fazenda Brasileiro gold mineralization The Fazenda Brasileiro gold mineralization is hosted by a gabbroic sill, intrusive into metavolcanicmetasedimentaryrocks of the Rio Itapicuru Greenstone Belt, São Francisco Craton. The 2.05 Ga old mineralizationis associated with intense shearing and hydrothermal alteration, and the host gabbro is altered to aseries of rocks rich in sericite, chlorite, actinolite, carbonate and quartz.Twelve whole-rock samples of the gold mineralization, representing varied degrees of alteration, from rockswith preserved igneous textures to the ore (quartz-carbonate-sulfide-chlorite), were studied by the Sm-Ndmethod. All analytical points resulted in an isochron (MSWD = 1.9) indicating the age of 2142 +/ 47 Ma(1s) and Epsilon Nd (T) of +1.2. Chlorite-sericite-carbonate rich hydrothermal rocks indicate the age of 2148+/ 57 Ma and Epsilon Nd (T) of +1.1. The positive Epsilon Nd (T) suggest limited or no contaminationwith older continental crust, compatible with an oceanic setting for the tholeiites.Combined withREEdata, the Sm-Nd isotopic results reveal that the hydrothermal alteration, although intense,was unable to alter significantly the Sm/Nd ratios of the original igneous rocks and did not cause importantscatter of the analytical points, providing a rare example of robust behavior of the isotopic system, even underintense hydrothermal alteration. 2003 artículo científico 0001-3765 https://www.redalyc.org/articulo.oa?id=32775309 en http://www.redalyc.org/revista.oa?id=327 Anais da Academia Brasileira de Ciências application/pdf Academia Brasileira de Ciências Anais da Academia Brasileira de Ciências (Brasil) Num.3 Vol.75 |
| title | Sm-Nd age of the fazenda brasileiro gabbro, Bahia, Brazil: example of robust behavior of the Sm-Nd isotopic system under extreme hydrothermal alteration |
| topic | Multidisciplinaria (Ciencias Naturales y Exactas) Sm Nd Paleoproterozoic Fazenda Brasileiro gold mineralization |
| url | https://www.redalyc.org/articulo.oa?id=32775309 |