Metamorphic evolution and U-Pb zircon SHRIMP geochronology of the Belizário ultramafic amphibolite, Encantadas Complex, southernmost Brazil

Anais da Academia Brasileira de Ciências

Léo A. Hartmann²  João O.s. Santos¹  Jayme A.d. Leite¹  Carla C. Porcher²  Neal J. Mcnaughton¹ 

[1] ,Universidade Federal do Rio Grande do Sul Instituto de Geociências Porto Alegre RS ,Brasil

关键词: ultramafic amphibolite;    zircon geochronology;    Encantadas Complex;    Trans-Amazonian Cycle;    metamorphism;    anfibolito ultramáfico;    geochronologia de zircão;    Complexo Encantadas;    Ciclo Transamazônico;    metamorfismo;   

DOI  :  10.1590/S0001-37652003000300010

来源: SciELO

【 摘 要 】

The integrated investigation of metamorphism and zircon U-Pb SHRIMP geochronology of the Belizário ultramafic amphibolite from southernmost Brazil leads to a better understanding of the processes involved in the generation of the Encantadas Complex. Magmatic evidence of the magnesian basalt or pyroxenite protolith is only preserved in cores of zircon crystals, which are dated at 2257 ± 12 Ma. Amphibolite facies metamorphism M1 formed voluminous hornblende in the investigated rock possibly at 1989 ± 21 Ma. This ultramafic rock was re-metamorphosed at 702±21 Ma during a greenschist facies eventM2; the assemblage actinolite + oligoclase + microcline + epidote + titanite + monazite formed by alteration of hornblende. The metamorphic events are probably related to the Encantadas Orogeny (2257±12 Ma) and Camboriú Orogeny (~ 1989 Ma) of the Trans-Amazonian Cycle, followed by an orogenic event (702±21 Ma) of the Brasiliano Cycle. The intervening cratonic period (2000-700 Ma) corresponds to the existence of the Supercontinent Atlantica, known regionally as the Rio de la Plata Craton.

【 授权许可】

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