Formation and Tectonic Evolution of Ophiolites in the Sabah Area (Borneo, SE Asia)

Zircon U-Pb dating, rock geochemistry, Sr-Nd-Pb, and zircon Hf isotope analyses were conducted on the ultrabasic and basic rocks of ophiolites in the Sabah area (Borneo, SE Asia). The zircon U-Pb ages of ultrabasic and basic rocks range from 248 to 244 Ma, indicating that the ophiolites already existed in the early Triassic. The rare earth elements of basic rocks in Central Sabah show N-MORB-type characteristics and E-MORB-type characteristics in the northwest and southeast. The εNd(t) values of basic rocks range from 3.66 to 8.73, and the εHf(t) values of zircon in ultrabasic rocks are between −10.2 and −6.1. Trace element analysis shows that the magmatic source was influenced by melts and fluids from the subducting plate of the Paleo-Tethys Ocean. The tectonic evolution of the Sabah area can be traced back to the Early Triassic. At that time, the fast subduction of the Paleo-Tethys Ocean plate and the retreating of the Paleo-Pacific plate resulted in the upwelling of mantle material in relatively small extensional settings, leading to the formation of the ophiolites. From the Jurassic to the Early Cretaceous, the Paleo-Pacific plate was intensely subducted, and the ophiolite intrusion in the Sabah area moved to the continental crust of South China or the Sundaland margin as fore-arc ophiolites. From the Late Cretaceous to the Miocene, with the expansion of the Proto-South China Sea and South China Sea oceanic crust, the ophiolites in the Sabah area drifted southward with microplate fragments and sutured with East Borneo.