?Where, when and why? for the arc-trench gap from Mesozoic Paleo-Pacific subduction zone: Sabah Triassic-Cretaceous igneous records in East Borneo

Establishing the location (where), timing (when) and reasons for the development (why) for the Mesozoic subduction along the western Paleo-Pacific that extended from Coastal South China to SE Vietnam has proven problematic due to the difficulty in the identification of the fore-arc igneous rocks. This paper firstly presents a set of zircon U-Pb and whole-rock 40Ar/39Ar geochronological, zircon in-situ Lu-Hf iso-topes, and whole-rock elemental and Sr-Nd-Pb isotopic data for the Mesozoic igneous rocks from the Sabah ophiolites and Segama non-ophiolitic basement in NE Borneo. Our work documents major phases of the formation of these rock units at -185-140 Ma, -135-112 Ma and -130-85 Ma for the Telupid, Kudat and Darvel Bay ophiolites in Sabah, respectively. The mafic rocks within the ophiolites are classi-fied into the MORB-, high-Nb, Nb-enriched and arc-like rocks, with the similar Sr-Nd (eNd(t) = +6.4-+10.2) and Atlantic-Pacific Ocean MORB-like Pb isotopic compositions. Their generation is related to input of slab-derived melt in the MORB mantle wedge source in an arc-trench gap setting. The Segama non-ophiolitic igneous rocks were dated at 251-178 Ma, with zircon in-situ eHf(t) = +9.5-+17.5, and are clas-sified as high-Si and low-Si adakite, and high-mg andesite. They are the fractional products of the wedge -derived magma with the source being modified by slab-derived fluids. The magmatic flare-ups at -251- 203, -185-153 Ma, -135-112 Ma and -95-85 Ma in Sabah are comparable with those in Coastal South China and West Borneo, indicating the Jurassic-Cretaceous accretionary orogenesis in Sabah. Sabah was tectonically located at the East Cathaysia margin of South China in the Mesozoic. It was a long-lived (>150 Ma) Andean-type active continental margin with multi-staged pulsed subduction and rollback in East Asia. Such a subduction system initiated no later than the earliest Triassic (-251 Ma) and continued till the Late Cretaceous (-85 Ma).(c) 2023 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Automated summary

This paper investigates the Mesozoic subduction along the coastal areas of Southeast Asia using various geological dating methods. The study finds that the formation of these rocks is closely related to crustal subduction and magmatic activities, providing evidence for a long-term material recycling process of subduction in the region.