| Autor: |
Márcio Martins Pimentel, Hardy Jost, Reinhardt Adolfo Fuck, Richard Austin Armstrong, Elton Luiz Dantas, Alain Potrel |
| Jazyk: |
English<br />Portuguese |
| Rok vydání: |
2003 |
| Předmět: |
|
| Zdroj: |
Geologia USP. Série Científica, Vol 3, Pp 1-12 (2003) |
| Druh dokumentu: |
article |
| ISSN: |
1519-874X |
| Popis: |
The first SHRIMP U-Pb ages for granitoid rocks from the southern part of the Goiás-Crixás Archean Block (Caiçara andUvá complexes) are presented and discussed in combination with Sm-Nd isotopic data in order to elucidate the main aspectsof the geological evolution of that part of the Brasília Belt in central Brazil. Zircon grains from a tonalitic gneiss (GOV-4) inthe Uvá Complex show that the original tonalite crystallized at 2934 ± 5 Ma. One metamorphic zircon crystal is concordantand indicates an Archean age for the recrystallization episode (2793 ± 3 Ma) and one inherited grain with an age of 3092 ± 9suggests, together with negative values of eNd(T) (+0.4 and –4.6), that the magma was contaminated with older crust. Oneleucocratic granite (GOV-1) exposed north of the Goiás greenstone belt crystallized at 626 ± 7 Ma, as indicated by theigneous overgrowths surrounding older inherited cores. The latter indicate a crystallization age of 2893 ± 12 Ma. This rockis interpreted therefore as the product of Neoproterozoic anatexis of ca. 2.89 Ga-old rocks of the Caiçara Complex. This isreinforced by strongly negative eNd(T = 626) values of – 28.0 and –29.0. Its crystallization age is identical to the U-Pb agesof the Itapuranga granite and Uruana quartz syenite, which are exposed to the north of the investigated area and interpretedas syn-tectonic intrusions in relation to the main Brasiliano tectonic event. This represents, therefore, the first evidence ofNeoproterozoic magmatism within the Goiás Archean Block and raises the possibility that other leucogranite dykes andstocks identified regionally may also have been formed during the Brasiliano orogeny. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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