Skip to main content

ORIGINAL RESEARCH article

Front. Earth Sci.
Sec. Petrology
Volume 12 - 2024 | doi: 10.3389/feart.2024.1527863

Petrology of the Eocene alkaline volcanism from the western Rio Grande Rise, South Atlantic Ocean

Provisionally accepted
Julia Taciro Mandacaru Guerra Julia Taciro Mandacaru Guerra 1*Valdecir de Assis Janasi Valdecir de Assis Janasi 1*Priyeshu Srivastava Priyeshu Srivastava 2,3Miguel Angelo Stipp Basei Miguel Angelo Stipp Basei 1George Luiz Luvizotto George Luiz Luvizotto 4Luigi Jovane Luigi Jovane 3
  • 1 Instituto de Geociências - Universidade de São Paulo, São Paulo, Brazil
  • 2 Indian Institute of Geomagnetism (IIG), Mumbai, Maharashtra, India
  • 3 Instituto Oceanográfico - Universidade de São Paulo, São Paulo, Brazil
  • 4 Departamento de Geologia, Instituto de Geociências e Ciências Exatas, Universidade Estadual de São Paulo, Rio Claro, São Paulo, Brazil

The final, formatted version of the article will be published soon.

    The origin and evolution of the Rio Grande Rise is deeply related to the opening of the South Atlantic Ocean. The geology of the plateau records the transition from divergent plate margins at the Mid-Atlantic Ridge to an intraplate tectonic setting. Despite the potential to bring insights into the complex tectono-magmatic processes involved in the development of the Rio Grande Rise, there is an overall lack of integrated petrological studies regarding its intraplate Eocene alkaline magmatism. We have investigated trachytes, trachyandesites, alkali basalts, a trachybasalt and a basanite dredged from the western Rio Grande Rise to characterize its magmatic system. Integrated petrography, mineral chemistry and whole-rock geochemistry suggests that these rocks have evolved in a complex transcrustal polybaric magmatic system, where crystals were remobilized by host liquids with different composition at distinct depths.Disequilibrium between crystals and host magmas is evidenced by abundant clinopyroxene macrocrysts with resorbed or corroded cores and rims with contrasting composition, as well as by resorbed feldspar macrocrysts. Clinopyroxene crystals also record cyclic compositional variations in magmatic chambers submitted to multiple magma recharge episodes and a strong control by fractional crystallization. U-Pb dating of zircons from a trachyte yielded an age of 46.9 ± 0.3 Ma, which reinforces the importance of the Eocene volcanism from the western Rio Grande Rise. Moreover, results from Pb, Sr and Nd isotope analysis reveal that Eocene alkaline volcanic rocks from the Western Rio Grande Rise have EMI-flavored Tristan-type signatures. This suggests that the mantle sources from the western Rio Grande Rise and from the Walvis Ridge and Guyot Province magmatism still shared common characteristics long after its separation from the Walvis Ridge.

    Keywords: Rio Grande Rise, Alkaline volcanism, igneous petrology, mineral chemistry, South Atlantic Ocean, Enriched Mantle I, Tristan-Gough mantle plume

    Received: 13 Nov 2024; Accepted: 23 Dec 2024.

    Copyright: © 2024 Taciro Mandacaru Guerra, Janasi, Srivastava, Basei, Luvizotto and Jovane. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence:
    Julia Taciro Mandacaru Guerra, Instituto de Geociências - Universidade de São Paulo, São Paulo, Brazil
    Valdecir de Assis Janasi, Instituto de Geociências - Universidade de São Paulo, São Paulo, Brazil

    Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.