| Popis: |
The Araguaia Belt (AB) in northcentral Brazil formed as the result of the amalgamation of the Amazonian and Sao Francisco-Congo cratons along with the Parnaiba Block during late Neoproterozoic times. Ediacaran/Cambrian late- to post-orogenic magmatism took place at ∼540 Ma following this continental collision at 550-540 Ma. Such magmatism is represented in the southern portion of the Araguaia Belt by the peraluminous Santa Luzia and Barrolândia granites, as well as by the Presidente Kennedy Granodiorite in the central portion of the AB. Inherited zircon cores with distinct rims are abundant in the Santa Luzia Granite. This pluton yields U Pb MC-LA-ICP-MS zircon and monazite ages of 538 ± 1 Ma and 534 ± 5 Ma, respectively. In addition, U Pb zircon and monazite ages of 536 ± 6 Ma and 524 ± 6 Ma, respectively, are obtained for the Barrolândia Granite. The data presented in this work and in the literature allow to group the studied Santa Luzia and Barrolândia granites, together with Presidente Kennedy Granodiorite, in a single suite, named Santa Luzia Suite, maintaining the Santa Luzia pluton as the type-area. Rocks related to this Cambrian magmatism are essentially peraluminous, magnesian to slightly ferroan, and calc-alkaline in character. Such rocks probably originated from magmas formed by partial melting of meta-igneous sources that were subsequently contaminated via assimilation of metasedimentary rocks. In the AB, both the collision related to the 550-540 Ma Brasiliano/Pan-African orogeny, and the intimately associated ∼540 Ma late- to post-orogenic Santa Luzia Suite magmatism record the closure of the Clymene Ocean as well as the late stages of compressional tectonics related to west Gondwana amalgamation. The latter was followed by exhumation related to collapse of the Araguaia orogen. |
Full Text from ScienceDirect