A Late Miocene magmatic flare-up in West Sulawesi triggered by Banda slab rollback

Abstract

Cenozoic magmatism occurs throughout West Sulawesi, Indonesia, yet its detailed evolution remains enigmatic due mainly to the scarcity of precise dating. Here, we report new whole-rock geochemical and zircon U-Pb-Hf isotopic data of plutonic/volcanic rocks and river sediments from West Sulawesi to constrain the petrogenesis and magmatic tempo. The magmatic rocks are intermediate to felsic (SiO2 = 58.1−68.0 wt%), high-K calc-alkaline to shoshonitic (K2O = 2.2−6.0 wt%), metaluminous to weakly peraluminous, and I-type in composition. Trace element concentrations and ratios (e.g., Nb/U = 1.7−4.3 and Ti/Zr <28), along with negative zircon εHf(t) values (−17.0 to −0.4) and old crustal model ages (TDMC = 2.1−1.1 Ga), indicate a dominant magma source region from the underlying continental crystalline basement. U-Pb dating on zircons from ten magmatic rocks yielded weighted mean 206Pb/238U ages of 7.2−6.1 Ma, best representing the crystallization ages of host magmas, further consistent with the prominent age peaks (7.3−6.3 Ma) defined by detrital zircons from four sedimentary samples. Our new data, combined with available results, allow the identification of a noticeable climax of magmatism (flare-up) at ca. 7−6 Ma, forming a continuous magmatic belt throughout West Sulawesi. Given the absence of contemporaneous subduction and the coincidence of incipient opening of the South Banda Basin during ca. 7.15−6.5 Ma, the Late Miocene magmatic flare-up in West Sulawesi and coeval regional extension in eastern Indonesia are attributed to a resumed episode of Banda slab rollback.

Neogene sediment provenance and paleogeography of SE Sulawesi, Indonesia

“…The Upper Miocene Pandua Formation records detrital zircon age spectra with Proterozoic, Triassic and Late Miocene peaks. The Proterozoic and Triassic peaks suggest recycling of the Meluhu Formation, while the Late Miocene peak probably represents magmatism and volcanic activity that are recorded in west Sulawesi (Hennig et al, 2016; White et al, 2017; Zhang et al, 2020) and SE Sulawesi (White et al, 2014).…”

Seismotectonics of Sulawesi, Indonesia

“…The rollback also facilitated the development of the South Sula fault, which exhibited the extensional southdipping normal fault (Titu-eki & Hall, 2020). Moreover, the resume extension-related magmatism in the South Arm of Sulawesi around the Middle and Late Miocene was also associated with the Banda slab rollback (Polvé et al, 1997;Hall, 2011;Hall & Sevastjanova, 2011;Zhang et al, 2020).…”

“…Sulawesi Island in the eastern Indonesian archipelago reflects a complex tectonic interaction between the Indian-Australian, Sunda, and Philippine Sea plates (Figure 1a). The distinctive K-shape of Sulawesi Island is the result of a series of ongoing tectonic events spanning the Cretaceous to the present day (Hall, 2012;Hall & Sapkman, 2015;Liu et al, 2020;Zhang et al, 2020Zhang et al, , 2022. As a result, the island is complex tectonically and active seismically.…”

Post-Earthquake groundwater potential analysis in Mamuju Regency, West Sulawesi

“…Secondly, it was influenced by Neogene contraction and lift due to the Sula Spur collision in the Early Miocene (Hamilton, 1979;Bergman et al, 1996;Calvert and Hall, 2007). The Early Miocene collision of the Sula Spur microcontinent (Klompé, 1954) and the North Arm volcanic arc (Hall, 2002) was followed by extensional fragmentation of the Sula Spur microcontinent because of Banda subduction rollback (Honthaas et al, 1998;Spakman and Hall, 2010;Hall, 2012;Hennig et al, 2016;Zhang et al, 2020;Nugraha et al, 2022).…”