Intan Noviantari Manyoe, Gayatri Indah Marliyani, Agung Harijoko, Wahyudi, Michelle Nadya Putri, Anang Sahroni, Mochamad Nukman, Florian Lhuillier
Previous studies have attributed magmatism in the Gorontalo Eastern Mountain Complex (GEMC) to subduction-related processes, slab delamination, or extensional tectonics. However, the timing of magmatic activity and its relationship to changes in subduction geometry and vertical-axis rotation remain poorly constrained. This study presents a new integrated dataset that combines 40K-40Ar geochronology, major- and trace-element geochemistry, and paleomagnetic data to constrain the magmatic and tectonic significance of the GEMC. New and published data indicate that tholeiitic to calc-alkaline volcanic rocks, ranging from basalt to rhyolite, were emplaced between ∼44.6 Ma and ∼ 0.16 Ma. The Tinombo basement formed during Eocene back-arc spreading in the Celebes Sea, likely driven by rollback of southward-subducting plates. The Lower Member of the Bilungala Volcanics was emplaced during the Oligocene to Miocene in association with northward subduction, followed by a transition to subduction related to the Sangihe. Subsequent magmatism, represented by the Middle Member of the Bilungala Volcanics and the Motomboto–Pinogu Volcanics, occurred from the Pliocene to the Pleistocene and is linked to the North Sulawesi subduction. Paleomagnetic results reveal significant clockwise vertical-axis rotation in the Gorontalo (39.6° ± 7.7°), established by the Late Miocene and likely facilitated by the geometry of surrounding slabs and accommodated by right-lateral strike-slip faulting along the arc. The results indicate that progressive reorganization of subduction geometry exerted control on arc magmatism and block rotation. This study provides new constraints on the tectono-magmatic evolution of the North Sulawesi Arc and offers a conceptual framework for understanding the dynamics of a structurally and magmatically segmented island-arc system at a convergent plate boundary. Copyright © 2024. Published by Elsevier B.V.
Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada, Jl. Grafika No. 2, Yogyakarta, 55284, Indonesia; Geophysical Study Program, Faculty of Mathematics and Natural Science, Sekip Utara, Jl. Kaliurang Bulaksumur, Universitas Gadjah Mada, Yogyakarta, 55281, Indonesia; Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Theresienstr. 41, Munich, 80333, Germany; Geological Engineering Study Program, Faculty of Mathematics and Natural Science, Universitas Negeri Gorontalo, Jl. Prof. Dr. Ing. B.J. Habibie, Gorontalo, 96554, Indonesia
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