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A New Understanding of the Provinces of the Amazon Craton Based on Integration of Field Mapping and U-Pb and Sm-Nd Geochronology |
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| Authors: | Joo Orestes Schneider Santos Lo Afraneo Hartmann Henri Eugene Gaudette David Ian Groves Neal Jesse Mcnaughton Ian Robert Fletcher |
| Institution: | aInstituto de Geociências, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves n° 9.500, Porto Alegre, Rio Grande do Sul, 91500-000, Brazil. Companhia de Pesquisa de Recursos Minerais, Rua Banco da Província, 105, Porto Alegre — Rio Grande do Sul, 90840-030, Brazil bInstituto de Geociências, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves n° 9.500, Porto Alegre, Rio Grande do Sul, 91500-000, Brazil cDepartment of Earth Sciences, University of New Hampshire, Durham, New Hampshire, 03824, USA dCentre for Strategic Mineral Deposits- CSMD -Department of Geology and Geophysics, University of Western Australia, Nedlands, Western Australia, 6907, Australia eCentre for Strategic Mineral Deposits- CSMD -Department of Geology and Geophysics, University of Western Australia, Nedlands, Western Australia, 6907, Australia fCentre for Strategic Mineral Deposits- CSMD -Department of Geology and Geophysics, University of Western Australia, Nedlands, Western Australia, 6907, Australia |
| Abstract: | New conventional and sensitive high-resolution ion microprobe zircon U-Pb dating has led to a new understanding of the subdivision and evolution of the Amazon Craton during Precambrian time, with major improvements and changes made to the previous Rb-Sr based model. The interpretation of U-Pb and Sm-Nd isotopic data identifies eight main Precambrian tectonic provinces in the Craton, with ages ranging from 3.1 to 0.99 Ga. Some of the provinces were generated by accretional, arc-related processes (Carajás, Transamazonic, Tapajós-Parima and Rondônia-Juruena) and others by recycling of continental crust (Central Amazon, Rio Negro and Sunsas). The exposed Archean crust is restricted to the east (Carajás and south Amapá in Brazil) and north (Imataca in Venezuela) of the craton, indicating that the Amazon Craton is largely a Proterozoic crust. The Carajás-Imataca (3.10–2.53 Ga) and Transamazonian (2.25–2.00 Ga) Provinces are composed predominantly of granite-greenstone terranes. The Tapajós-Parima (2.10–1.87 Ga) and Rondônia-Juruena (1.75–1.47 Ga) Provinces represent new crust added as orogenic belts, while the Rio Negro (1.86–1.52 Ga) and Sunsas (1.33–0.99 Ga) Provinces originated mainly by magmatic-tectonic recycling of the above two orogenic belts. The only zone with a prominent northeast trend is the poorly known K'Mudku Shear Belt, characterized by a ∼1.20 Ga shear zone which deforms the rocks of at least three different provinces (Rio Negro, Tapajós-Parima and Transamazonic). The Central Amazon Province comprises mostly Orosirian volcano-plutonic rocks (Uatumã Magmatism) and is a terrane in which the exposed crustal structure and deformation are pluton-related. The Sm-Nd TDM model ages and ɛNd suggest that the Central Amazon Province was generated by the partial melting of Archean continental crust (Carajás Province?), perhaps related to underplating that began at the end of the Tapajós-Parima Orogeny (1.88–1.86 Ga). |
| Keywords: | Amazon Craton South America crustal growth Transamazonic U-Pb geochronology |
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