There are many crustal fragments in northeast Borneo that are derived from Mesozoic ophiolites placed during the initiation of the western Pacific Ocean plate subducting beneath southeast China and southeast Asia [REF].
An ophiolite is a sequence of oceanic lithosphere that has been thrust on top of continental lithosphere and therefore has peridotites, gabbros and basaltic units overlain by cherts and submarine volcanic and sedimentary rocks [REF].