Neoproterozoic magmatism and high-grade metamorphism in the Goiás Massif: New LA-MC-ICMPS U–Pb and Sm–Nd data and implications for collisional history of the Brasília Belt

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• 作者：Maria Emilia Schutesky Della Giustina ; Claudinei Gouveia de Oliveira ; Má ; rcio Martins Pimentel ; Bernhard Buhn
• 关键词：Neoproterozoic ; Brasiliano orogen ; Uruaç ; u Complex ; U– ; Pb LA-MC-ICPMS ; Metamorphic core ; Delamination
• 刊名：Precambrian Research
• 出版年：2009
• 出版时间：July 2009
• 年：2009
• 卷：172
• 期：1-2
• 页码：67-79
• 全文大小：2670 K

文摘

This paper presents the first U–Pb and Sm–Nd data for the gneisses of the high-grade Uruaçu Complex, exposed in the northern part of the Neoproterozoic Brasília Belt, central Brazil. Previous studies have interpreted this complex as the exposure of Archaean or Paleoproterozoic continental crust, included, therefore, in the so-called Goiás Massif, a small Archaean/Paleoproterozoic allochthonous (?) block. The complex is located in the northern Brasília Belt, adjacent to the eastern limit of the Goiás Magmatic Arc, and comprises a variety of para- and orthogneisses metamorphosed under amphibolite to granulite facies. New U–Pb LA-MC-ICPMS data for zircon grains from felsic and mafic orthogneisses reveal ages ranging from ca. 690 to 650 Ma, interpreted as representative of the original igneous crystallization. Zircon overgrowths indicate metamorphic ages around 650 Ma, suggesting that the metamorphism was partly concomitant or only slightly younger than the intrusion of granitoids and mafic bodies, as well as with the closure of the ocean between the Amazon and São Francisco continents at the end of the Neoproterozoic.

The main geological characteristics of the Uruaçu Complex, as well as the new U–Pb crystallization and provenance ages discussed in this work, are analogous to those observed in the Anápolis–Itauçu Complex, exposed in the southern Brasília Belt. This may suggests the correlation between both complexes, resulting in a long granulitic belt developed to the east of the Goiás Magmatic Arc during the main collisional stage of evolution of the Brasília Belt. High-grade metamorphism and associated igneous intrusions represented mainly by metagabbros and metagranites are, therefore, a conspicuous feature of the final stages of evolution of the Brasília Belt and might be related to delamination, uplift and extension following ocean closure and continental collision.