The 1590-1520 Ma Cachoeirinha magmatic arc and its tectonic implications for the Mesoproterozoic SW Amazonian craton crustal evolution

Anais da Academia Brasileira de Ciências

Amarildo S. Ruiz²  Mauro C. Geraldes¹  João B. Matos²  Wilson Teixeira¹  William R. Van Schumus¹  Renata S. Schmitt¹ 

[1] ,Universidade Federal de Mato Grosso Departamento de Geologia Cuiabá MT ,Brasil

关键词: Amazonian craton;    U-Pb and Sm-Nd geochronology;    Mesoproterozoic;    juvenile magmatism;    Craton Amazônico;    geocronologia U-Pb e Sm-Nd;    Mesoproterozóico;    magmatismo de arco;   

DOI  :  10.1590/S0001-37652004000400013

来源: SciELO

【 摘 要 】

Isotopic and chemical data of rocks from the Cachoeirinha suite provide new insights on the Proterozoic evolution of the Rio Negro/Juruena Province in SW Amazonian craton. Six U-Pb and Sm-Nd analyses in granitoid rocks of the Cachoeirinha suite yielded ages of 1587-1522 Ma and T DM model ages of 1.88-1.75 Ga (EpsilonNd values of -0.8 to +1.0). In addition, three post-tectonic plutonic rocks yielded U-Pb ages from 1485-1389 Ma (T DM of 1.77-1.74 Ga and EpsilonNd values from -1.3 to +1.7). Variations in major and trace elements of the Cachoeirinha suite rocks indicate fractional crystallization process and magmatic arc geologic setting. These results suggest the following interpretations: (1) The interval of 1590-1520 Ma represents an important magmatic activity in SW Amazonian craton. (2) T DM and arc-related chemical affinity supportthe hypothesis that the rocks are genetically associated with an east-dipping subduction zone under the older (1.79-1.74 Ga) continental margin. (3) The 1590-1520 Ma age of intrusive rocks adjacent to an older crust represents similar geological framework along the southern margin of Baltica, corroborating the hypothesis of tectonic relationship at that time.

【 授权许可】

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