Dynamic thermochronological study of Mt Kinabalu, Sabah, Malaysia
Christian Sperber, completed PhD
This project intends to apply cutting-edge low-temperature thermochronological techniques to resolve the tectonic and structural evolution of Mt Kinabalu, the highest mountain in Southeast Asia. This enigmatic peak stands out dramatically from the regional topography, with its 4100m summit rising above a massif largely below 1000m high, and with few other peaks up to 2500m. The full relief of Mt Kinabalu is even greater, as immediately to the north the topography descends rapidly to depths of more than 2000 m in the Sulu Sea. A related project examined the crystallisation and higher-temperature thermal history of the mountain’s granitic litholiges.
The mountain is composed of granite, and although the exact age of intrusion is uncertain, it is estimated to behave been emplaced and exhumed in a total of less than 15 Ma. A similar granite body along strike in Palawan has yielded U-Pb ages of ~15 Ma, and available K-Ar ages from rocks and minerals from the Kinabalu pluton itself and nearby minor intrusions spread over a range of about 8 million years. Existing data indicate that Mt Kinabalu must have experienced dramatic recent uplift and exhumation, but the timing and mechanism of this remain ambiguous. Pilot fission track dating studies estimate removal of 4-8 km of crust in less than 5 Ma.
Not only is this rapid unroofing unusual, its dynamic cause is also unclear. Immediately to the north and south of Kinabalu are large sedimentary basins that appear to have been subsiding at the same time the Kinabalu granite was forming. Recent and ongoing studies in Sabah by the SE Asia Research Group at Royal Holloway suggest a number of tectonic hypotheses that could account for the apparent subsidence and uplift. This project utilises low-temperature thermochronology – specifically apatite (U-Th)/He and apatite & zircon fission track dating – to test these hypotheses.
(U-Th)/He and fission track analyses were undertaken in collaboration with Barry Kohn & Asaf Raza (University of Melbourne), with additional fission track analyses carried aided by Andy Carter (University College London)