U-Pb zircon geochronology of Early Permian to Late Triassic rocks from Singapore and Johor: A plate tectonic reinterpretation

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, Middle 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 predominantly 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.