Pulsed emplacement of the Mount Kinabalu granite, northern Borneo

Abstract

High-precision U–Pb ion microprobe analyses provide new constraints on the emplacement and origin of the Kinabalu granite in Sabah, northern Borneo. The granite is a sheeted laccolith-like body comprising dyke-fed granitic units that young downwards, each emplaced beneath the previous sheet. Analyses of concentric growth zones in zircons indicate crystallization between 7.85 ± 0.08 and 7.22 ± 0.07 Ma, and show that the entire pluton was emplaced and crystallized within less than 800 ka. Several pulses of magmatism are recognized, each lasting for a maximum of 250 ka, and possibly as briefly as 30 ka. The oldest ages coincide with the highest elevations whereas the youngest ages are found at lower elevations around the edge of the body. Based on these new age data and field observations we identify the biotite granodiorite, hornblende granite and porphyritic facies as the Upper, Middle and Lower Units respectively. Inherited zircon ages indicate different protoliths for the Upper and Middle Units. The Upper Unit is derived from attenuated continental crust of the South China margin subducted beneath Sabah. The Middle Unit is sourced from melting of the crystalline basement in Sabah with little or no contribution from South China crust. Supplementary material: Full U–Pb ion microprobe analytical data, and modal and major element composition data are available at http://www.geolsoc.org.uk/SUP18385 .

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

“…The granite has a roughly elliptical shape, elongated approximately NE-SW, with a major axis of c. 16 km and a minor axis c. 10 km. Petrographically it is a true granite (Reinhard & Wenk 1951;Kirk 1968;Kasama et al 1970;Cottam et al 2010), closely resembling Cordilleran granitoids (Frost et al 2001). Amphibole geobarometry (Vogt & Flower 1989) suggests emplacement at between 3 and 8 km.…”

“…Exhumation was previously interpreted to reflect post-orogenic collapse following the end of the Early Miocene Sabah orogeny (Hutchison 1996), when the extended passive continental margin of South China collided with north Borneo (Hall & Wilson 2000;Hutchison et al 2000) and subduction terminated. However, recent dating studies (Cottam et al 2010) have shown that the age of the granite is between 8 and 7 Ma, bringing these previous interpretations into question . We present new thermochronological analyses ( 40 Ar/ 39 Ar, fission-track and (U-Th-Sm)/He) on samples of the Kinabalu granite collected from a 2000 m elevation profile up the southern slopes of Mount Kinabalu. We combine the results of the three principal thermochronometers to derive a detailed thermal history for the Kinabalu granite, and utilize the variation of thermochronometric data with elevation to estimate rates of exhumation.…”

Mantle structure and tectonic history of SE Asia

“…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 palaeogeography of Sundaland and Wallacea since the Late Jurassic

“…This significantly increased the land area of Palawan and Borneo and formed highlands in the interior of Borneo. Large rivers flowed outwards as Borneo rose and the land area contin- (Cottam et al, 2010) now exposed at 4 km above sea level. Kinabalu is one of the few mountains between New Guinea and the Himalayas that was provably capped by ice during the Pleistocene (Hope, 2004).…”