Please use this identifier to cite or link to this item:
Title: Zircon petrochronology reveals the moderately juvenile signature of a diatexite from the boundary one between the Brasília and Ribeira orogens (SE Brazil) : relict of a Tonian arc?
Authors: Costa, Fernanda Moura
Penna, João Lucas Andrade
Martins, Lorena Cristina Dias
Tedesch, Mahyra
Novo, Tiago Amâncio
Araujo, Cristina Santos
Vieira, Pedro Leonardo Rossi
Lana, Cristiano de Carvalho
Soares, Antônio Carlos Pedrosa
Keywords: Protracted zircon geochronological record
Prolonged metamorphism
Juvenile magma
Brasiliano orogeny
Issue Date: 2022
Citation: COSTA, F. M. et al. Zircon petrochronology reveals the moderately juvenile signature of a diatexite from the boundary one between the Brasília and Ribeira orogens (SE Brazil): relict of a Tonian arc? Journal of South American Earth Sciences, v. 116, artigo 103767, jun. 2022. Disponível em: <>. Acesso em: 15 mar. 2023.
Abstract: Unraveling the tectonic evolution of Precambrian high-grade rocks is often challenging owing to widespread metamorphic overprint under high to ultra-high temperature conditions. In this scenario, isotopic systems-based investigations constitute an important tool to obtain the time constrains of formation and evolution of rocks.We present a petrochronological investigation using U–Pb and Lu–Hf data of zircon grains extracted from a biotitebearing granitic leucosome from a diatexite found in the boundary zone between the Brasília and Ribeira orogens, SE Brazil. Clusters of 176Hf/177Hf(t) ratio values characterize two distinct zircon data groups, suggesting at least two different crystallization stages. 176Hf/177Hf(t) ratios from group 1 range from 0.28230 to 0.28247 with εHf (t) between +7.54 and − 1.55, representing a moderately juvenile to evolved magma. This group constrains a time interval of ca. 890-540 Ma, and the ancient zircon core (890 Ma) could potentially record the minimum age for the magmatic crystallization of a moderately juvenile protolith, with ϵHf (890) ranging from +8.66 to +0.36. Excluding this ancient zircon (since it is the only date older than 800 Ma), the oldest grain provides a minimum crystallization age of ca. 797 Ma, with ϵHf (797) between +6.73 and -1.61. Group 2, exhibiting 176Hf/177Hf(t) ratios from 0.28214 to 0.28225and negative εHf(t) values (− 3.35 to − 7.53), represents xenocrysts of crustal origin from the protolith or an influx of allochthonous crustal melt during high-grade metamorphism. The age spreading from ca. 890 Ma to ca. 540 Ma along the concordia is consistent with a Pb-loss scenario, with cores locally providing younger ages than rims. This is also consistent with prolonged metamorphism, as newly crystallized domains also present a spread of ages. Our data indicate that the leucosome is the metamorphic product of a moderately juvenile rock. When placed in the regional context, the biotite-bearing granitic leucosome may represent the relic of a magmatic arc, now located in the boundary zone between the Brasília and Ribeira orogens. Its moderately juvenile signature suggests the following tectonic setting interpretations: (i) an intra-oceanic subduction setting similar to modern island arcs or an early stage of continental subduction, formed at ca. 890–800 Ma and, thus could be potentially correlated with juvenile magmatic arcs found in both Brasília (Mara Rosa – Arenopolis ´ arc system) and Ribeira (Serra da Prata – Rio Negro arc system) orogens, suggestive of a large ocean realm to the south of the Sao ˜ Francisco paleocontinental block in Tonian time; and (ii) the most primitive relic of an early stage of the continental magmatic arc installed on the active margin of the Paranapanema paleocontinent.
ISSN: 1873-0647
Appears in Collections:DEGEO - Artigos publicados em periódicos

Files in This Item:
File Description SizeFormat 
  Restricted Access
17,27 MBAdobe PDFView/Open

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.