U–Pb zircon geochronology of Early Permian to Late Triassic rocks from Singapore and Johor: A plate tectonic reinterpretation Grahame Oliver a, ⁎, Khin Zaw b , Mark Hotson b , Sebastien Meffre b , Takayuki Manka b a Department of Civil and Environmental Engineering, National University of Singapore, Singapore b CODES ARC Centre of Excellence in Ore Deposits, University of Tasmania, Private Bag 126, Hobart 7001, Tasmania, Australia abstract article info Article history: Received 26 June 2012 Received in revised form 26 March 2013 Accepted 28 March 2013 Available online 12 April 2013 Keywords: U–Pb geochronology Johor Singapore Plate tectonics Tin The results of U–Pb zircon geochronology of Permian to Middle Triassic granitoids from Singapore and neighbouring Johor are presented. Rhyolite from Pulau Sibu is 276 ± 5 Ma, gabbros from Singapore give ages of 260 ± 2 to 249 ± 2 Ma, granites from Singapore give ages from 249 ± 2 to 230 ± 6 Ma and rhyolite from Telkuma gives an age of 238 ± 2 Ma. U–Pb detrital zircon age spectra from a Late Triassic conglomerate from Singapore show Carboniferous, Mid- dle Triassic and Late Triassic spikes at 350, 245 and 217 Ma respectively. These new data, when combined with published U–Pb zircon ages, allow a revision of the plate tectonic evolution of the Malaysian Peninsula region. A tin-bearing magmatic arc evolved in the Eastern Malaysian Peninsula part of Indochina from the Early Permian to the Middle Triassic when the Palaeo Tethys Ocean was subducted and Sibumasu continental lithosphere was rifted from Pangea. This opened up the Neo Tethys Ocean. That the granitoid ages show a progressive decrease in age from Pulau Sibu (276 ± 5 Ma) to Singapore (230 ± 6 Ma) suggests that during this Andean-type orogenic phase, the subduction zone rolled back and steepened causing the locus of mainly I-type magmatism to migrate from east to west (in present day coordinates) across the Eastern and Central Belts and stretch the lithosphere as it did so. In the Late Triassic, Sibumasu collided with Indochina causing the Western Belt (Sibumasu) to over-thrust the Central Belt (Indochina) along the Bentong–Raub Suture. The lower half of the thickened crust (formally the tin-bearing Indochina Plate) was partially melted and pre- dominantly S-type tin-bearing granites were intruded into the upper crust (formally Sibumasu). This Late Triassic collisional phase is the Indosinian Orogeny in Peninsular Malaysia. © 2013 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. 1. Introduction The basement geology of mainland SE Asia, Malaysia and Singapore is composed of a complex collage of tectonic plates mostly derived from Gondwana/Pangea in the Palaeozoic and Mesozoic and accreted to Asia in the Late Palaeozoic to Cenozoic (Metcalfe, 1988, 2011; Zaw et al., 2014–in this issue). Although this broad tectonic framework is relatively well understood, the detailed geology and in particular the timing, extent and polarity of subduction zones are poorly constrained in Peninsular Ma- laysia. U–Pb zircon geochronology of igneous rocks using laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) is now an in- expensive and rapid method for constraining the ages of magmatic, meta- morphic and sedimentary rocks to aid with tectonic reconstructions. In this paper, we present the LA-ICP-MS U–Pb zircon geochronology of the granitoids and granitoid-derived sedimentary rocks from Singapore and neighbouring Johor, Malaysia, and investigate the implications of these results for the plate tectonic evolution of the Malaysian Peninsula region. 2. Regional geology of the Malaysian Peninsula 2.1. Stratigraphy The geology of the Malaysian Peninsula can be subdivided into four main tectono-stratigraphic units: the Western, Central and East- ern Belts and the Bentong–Raub Suture Zone (Hutchison and Tan, 2009)(Fig. 1). The Western Belt has a Cambrian to Upper Permian, mainly shallow marine sedimentary sequence of Gondwana affinity, containing cold water brachiopods and glacial drop stones (Lee, 2009). Radiolarian cherts in the Semanggol Formation give Upper De- vonian to Middle Triassic ages (Metcalfe, 2011) with some gaps in the record, including a lack of Lower Triassic cherts. Although there are small outcrops of Permian limestones and cherts in the Kodiang– Chuping basin (see Fig. 1), there is a notable lack of Permian volcanic activity or siliciclastic deposition in the Western Belt generally and no record of uppermost Triassic sedimentation (Nuraiteng, 2009). Gondwana Research 26 (2014) 132–143 ⁎ Corresponding author at: Department of Geography, 1 Arts Link, National Univer- sity of Singapore, 117570, Singapore. Tel.: +65 65166639; fax: +65 67773091. E-mail address: geogo@nus.edu.sg (G. Oliver). 1342-937X/$ – see front matter © 2013 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.gr.2013.03.019 Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr