Two neoproterozoic crustal accretion events in the Brasília belt, central Brazil
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- 作者：Laux ; Jorge Henrique ; Pimentel ; Má ; rcio Martins ; Dantas ; Elton Luiz ; Armstrong ; Richard ; et. al.
- 关键词：Crustal accretion ; Geochronology U&ndash ; Pb ; Goiá ; s magmatic arc ; Orthogneiss
- 刊名：Journal of South American Earth Sciences
- 出版年：2005
- 出版时间：January, 2005
- 年：2005
- 卷：18
- 期：2
- 页码：183-198
- 全文大小：1.19 M
文摘
New U–Pb and Sm–Nd isotopic data for orthogneiss and granitoid rocks from the Neoproterozoic Goiás magmatic arc in western Goiás constrain the geological evolution of this juvenile crust in the western Brasília belt. Orthogneiss rock samples have U–Pb crystallization ages of 804±6, 669±3, 662±12, 634±8, 630±5, and 637±20Ma and show 
Nd(T) values between +2.8 and −15.1. Rock units with negative Nd(T) are more frequent in the eastern part of the studied area to the south of Anicuns, which indicates the presence of older continental crust in that part of the arc. Metagranitoids have ages of 821±10, 810±10, 792±5, 790±12, 782±14, 748±4, and 614±5Ma and Nd(T) values between +5.1 and −3.7. The data presented here, combined with those in the literature, suggest that igneous activity in the Goiás magmatic arc took place in two episodes: between ca. 0.89 and 0.8Ga, probably in intraoceanic settings, and between ca. 0.66 and 0.60Ga, likely in an active continental margin at the end of the Brasiliano orogeny.
Nd(T) values between +2.8 and −15.1. Rock units with negative Nd(T) are more frequent in the eastern part of the studied area to the south of Anicuns, which indicates the presence of older continental crust in that part of the arc. Metagranitoids have ages of 821±10, 810±10, 792±5, 790±12, 782±14, 748±4, and 614±5Ma and Nd(T) values between +5.1 and −3.7. The data presented here, combined with those in the literature, suggest that igneous activity in the Goiás magmatic arc took place in two episodes: between ca. 0.89 and 0.8Ga, probably in intraoceanic settings, and between ca. 0.66 and 0.60Ga, likely in an active continental margin at the end of the Brasiliano orogeny.