Age and MORB geochemistry of the Sabah ophiolite basement

Abstract

A late Jurassic to early Cretaceous (Neocomian) age is most likely for the ophiolite basement of Sabah, consistent with the Barremian-Aptian age of the overlying ribbon cherts. Attempts at dating have been confined to the K:Ar method, unfortunately unsuited to this rock suite because of its low potassium and high atmospheric argon contents. Our data confirm the need for interpreting part of the extensive ophiolite terrane of the Segama Highlands as consisting of continental lithosphere of Jurassic age - only limited exposures of calc-alkaline granite are known in the Litog Klikog Kiri vicinity ofUlu Segama. The ophiolite suite of the Labuk and Segama Highlands is oflow-K tholeiitic affinity and the trace element geochemistry indicates MORB characteristics, typical of magma formation at a mid ocean ridge spreading centre. Before uplift, the Sabah ophiolitic basement may be interpreted as having formed an integral part of either the western Pacific or the eastern Indian Ocean, extant beneath sea level in the Argo Abyssal Plain west of Australia.