A new understanding of the provinces of the Amazon Craton based on integration of field mapping and U-Pb and Sm-Nd geochronology

J.O.S. Santos, L.A. Hartmann, H.E. Gaudette, David Groves, Neal Mcnaughton, I.R. Fletcher

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    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, are-related processes (Carajas, Transamazonic, Tapajos-Parima and Rondonia-Juruena) and others by recycling of continental crust (Central Amazon, Rio Negro and Sunsas). The exposed Archean crust is restricted to the east (Carajas and south Amapa in Brazil) and north (Imataca in Venezuela) of the craton, indicating that the Amazon Craton is largely a Proterozoic crust. The Carajas-Imataca (3.10-2.53 Ga) and Transamazonian (2.25-2.00 Ga) Provinces are composed predominantly of granite-greenstone terranes. The Tapajos-Parima (2.10-1.87 Ga) and Rondonia- 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 similar to 1.20 Ga shear zone which deforms the rocks of at least three different provinces (Rio Negro, Tapajas-Parima and Transamazonic). The Central Amazon Province comprises mostly Orosirian volcano-plutonic rocks (Uatuma Magmatism) and is a terrane in which the exposed crustal structure and deformation are pluton-related. The Sm-Nd T-DM model ages and epsilon(Nd) suggest that the Central Amazon Province was generated by the partial melting of Archean continental crust (Carajas Province?), perhaps related to underplating that began at the end of the Tapajos-Parima Orogeny (1.88-1.86 Ga).
    Original languageEnglish
    Pages (from-to)453-488
    JournalGondwana Research
    Publication statusPublished - 2000


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