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Discovery of young submarine volcanism in the Cook Islands: New constraints on the location of the Rarotonga hotspot.

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Title: Discovery of young submarine volcanism in the Cook Islands: New constraints on the location of the Rarotonga hotspot.
Authors: Du, Yifan1 (AUTHOR) ydu823@ucsb.edu, Jackson, Matthew G.1 (AUTHOR), Jicha, Brian2 (AUTHOR), Kylander-Clark, Andrew1 (AUTHOR), Byerly, Benjamin L.1 (AUTHOR), Bizimis, Michael3 (AUTHOR), Halldórsson, Sæmundur Ari4 (AUTHOR), Seward, Gareth G.E.1 (AUTHOR), Anderson, Olivia E.1 (AUTHOR), Rioux, Matthew1 (AUTHOR), Konrad, Kevin5 (AUTHOR), Harðardóttir, Sunna1 (AUTHOR), Bai, Ruixia1 (AUTHOR), Giuliani, Andrea6 (AUTHOR), Wiens, Douglas A.7 (AUTHOR), Wei, S. Shawn8 (AUTHOR), McCormack, Gerald9 (AUTHOR), Parianos, John Michael10 (AUTHOR)
Source: Geochimica et Cosmochimica Acta. Feb2026, Vol. 415, p283-296. 14p.
Subjects: Submarine volcanoes, Analytical geochemistry, Plate tectonics, Islands, Volcanology, Lava flows
Geographic Terms: Cook Islands, Rarotonga (Cook Islands), Pacific Ocean
Abstract: A multiple-hotspot origin has been proposed for the Cook–Austral volcanic lineament in the southwest (SW) Pacific. One candidate, the Rarotonga hotspot, is associated with volcanism on only two islands: Rarotonga (1.157 ± 0.003 to 1.697 ± 0.055 Ma) and Aitutaki (youngest stage: 1.382 ± 0.058 to 1.941 ± 0.035 Ma), located ∼250 km apart in a north–south (N–S) direction. Their overlapping eruption ages and lack of clear age progression preclude a robust evaluation of a hotspot origin. This study identifies and investigates a new volcanic feature, Tama Seamount—located ∼80 km east–southeast (ESE) of Rarotonga Island along a Pacific plate flowline—potentially associated with the Rarotonga hotspot. New ages from two lavas (40Ar/39Ar groundmass ages: 0.664 ± 0.027 and 0.816 ± 0.020 Ma) and from a nepheline syenite xenolith—including zircon U–Pb dating (weighted mean age: 0.74 ± 0.02 Ma) and a biotite 40Ar/39Ar age (0.730 ± 0.007 Ma)—constrain Tama's age. These ages align with a Rarotonga hotspot age progression based on Pacific plate motion, and support a Rarotonga hotspot origin for Tama. We also report on the first lava samples dredged from the submarine flanks of Rarotonga Island, which exhibit geochemical fingerprints and an age (1.493 ± 0.007 Ma) consistent with those of previous Rarotonga samples. Furthermore, radiogenic isotopes of Tama samples in this study overlap with existing Rarotonga Island data, supporting a genetic relationship between Tama Seamount and Rarotonga Island. Together, these new results suggest Tama Seamount represents the youngest known expression of the Rarotonga hotspot. [ABSTRACT FROM AUTHOR]
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Abstract:A multiple-hotspot origin has been proposed for the Cook–Austral volcanic lineament in the southwest (SW) Pacific. One candidate, the Rarotonga hotspot, is associated with volcanism on only two islands: Rarotonga (1.157 ± 0.003 to 1.697 ± 0.055 Ma) and Aitutaki (youngest stage: 1.382 ± 0.058 to 1.941 ± 0.035 Ma), located ∼250 km apart in a north–south (N–S) direction. Their overlapping eruption ages and lack of clear age progression preclude a robust evaluation of a hotspot origin. This study identifies and investigates a new volcanic feature, Tama Seamount—located ∼80 km east–southeast (ESE) of Rarotonga Island along a Pacific plate flowline—potentially associated with the Rarotonga hotspot. New ages from two lavas (40Ar/39Ar groundmass ages: 0.664 ± 0.027 and 0.816 ± 0.020 Ma) and from a nepheline syenite xenolith—including zircon U–Pb dating (weighted mean age: 0.74 ± 0.02 Ma) and a biotite 40Ar/39Ar age (0.730 ± 0.007 Ma)—constrain Tama's age. These ages align with a Rarotonga hotspot age progression based on Pacific plate motion, and support a Rarotonga hotspot origin for Tama. We also report on the first lava samples dredged from the submarine flanks of Rarotonga Island, which exhibit geochemical fingerprints and an age (1.493 ± 0.007 Ma) consistent with those of previous Rarotonga samples. Furthermore, radiogenic isotopes of Tama samples in this study overlap with existing Rarotonga Island data, supporting a genetic relationship between Tama Seamount and Rarotonga Island. Together, these new results suggest Tama Seamount represents the youngest known expression of the Rarotonga hotspot. [ABSTRACT FROM AUTHOR]
ISSN:00167037
DOI:10.1016/j.gca.2025.12.058