Neogene rock uplift and erosion in northern Borneo: evidence from the Kinabalu granite, Mount Kinabalu

Abstract

Thermochronological data from the Kinabalu granite, emplaced between c. 7.2 and 7.8 Ma, provide a unique record of northern Borneo's exhumation during the Neogene. Biotite 40 Ar/ 39 Ar ages (c. 7.32-7.63 Ma) record rapid cooling of the granite in the Late Miocene as it equilibrated with ambient crustal temperatures. Zircon fission-track ages (c. 6.6-5.8 Ma) and apatite (U-Th-Sm)/He ages (central age c. 5.5 Ma) indicate rapid cooling during the Late Miocene-Early Pliocene. This cooling reflects exhumation of the granite, uplift and erosion bringing it closer to the Earth's surface. Thermochronological age versus elevation relationships suggest exhumation rates of more than 7 mm a −1 during the latest Miocene and Early Pliocene. Neither the emplacement of the Kinabalu granite nor its exhumation is related to the Sabah orogeny, which terminated in the Early Miocene. Instead, granite magmatism was caused by extension related to subduction rollback of the Sulu Arc, and Mio-Pliocene exhumation of the Kinabalu granite was driven either by lithospheric delamination or break-off of a subducted slab beneath Sabah. Plio-Pleistocene tectonism offshore and onshore northern Borneo reflects continuing large-scale gravity-driven tectonics in the region.

Mantle structure and tectonic history of SE Asia

“…Regional surface wave tomography (Tang and Zheng, 2013) shows high velocities in the lithosphere suggesting the anomaly is real. Assuming it is not an artefact, a possible explanation for this feature is a slab subducted northwards from the Celebes Sea in the Middle and Late Miocene (c. 15 to 5 Ma), now broken off, which created the Sulu arc (Cottam et al, 2013;Hall, 2013). However, if this was the case it would be expected that the slab would be imaged beneath the Sulu Sea and it is not (Vertical_slices/Slices_Sulu/Sulu_sli.mov and Vertical_slices/Slices_Proto_SCS/Proto_SCS_sli.mov; mm17.mp4 and mmc15.mp4).…”

“…However, if this was the case it would be expected that the slab would be imaged beneath the Sulu Sea and it is not (Vertical_slices/Slices_Sulu/Sulu_sli.mov and Vertical_slices/Slices_Proto_SCS/Proto_SCS_sli.mov; mm17.mp4 and mmc15.mp4). The anomaly is directly beneath Mt Kinabalu which is a granite pluton emplaced between 8-7 Ma (Cottam et al, 2010) and rapidly exhumed during the Late Miocene to Early Pliocene (Cottam et al, 2013). An alternative explanation is that the anomaly represents a thickened lithosphere beneath northern Borneo, formed during collision of the Dangerous Grounds microcontinental block with the Sabah-Cagayan volcanic arc, which has recently detached and is sinking into the mantle below Mt Kinabalu (Cottam et al, 2013).…”

The 2015 M w 6.0 Mt. Kinabalu earthquake: an infrequent fault rupture within the Crocker fault system of East Malaysia

“…Kinabalu, whereas geological evidence indicates that the Mt. Kinabalu Granite has risen rapidly since its crystallization 5-6 Ma (Cottam et al 2013). These contradictions suggest that the extensional forces that are creating the normal fault system are directly related neither to the forces creating the offshore fold-and-thrust belt nor to those that have created the edifice of Mt.…”

“…Within that mountainous backbone, by far the highest peak is Mt. Kinabalu, which consists of a granitic pluton that was rapidly exhumed since its crystallization about 5-6 Ma (Cottam et al 2013) (Fig. 1b).…”

Quantifying deformation in North Borneo with GPS

“…The Baram Delta is an active fold-and-thrust belt and situated south of the NorthWest Borneo Trough (Ingram et al 2004;King et al 2010; (Hall 2013). During this period (8-7 Ma) also the Mount Kinabalu granite was intruded into the already existing Crocker Range (Cottam et al 2010(Cottam et al , 2013. Deposition of the Rajang Group and Trusmadi Formation ended 40-35 Ma and predates the Crocker Range.…”