Geochemistry and Nd isotopic composition of the Permian Ko Sire Formation, Phuket Island, Thailand: implications for palaeoclimate and palaeogeographical configuration of the Sibumasu Terrane

Abstract

The Sibumasu Terrane is a continental block in SE Asia that is considered to have been attached to Gondwana before its collision with Indochina during the Triassic. The elemental geochemistry and Sm-Nd isotopic composition of mudrocks from the lower Permian Ko Sire Formation of the Phuket Group on Phuket Island (central Sibumasu Terrane), Thailand, were analysed to investigate its provenance, weathering history and palaeogeographical location prior to its separation from Gondwana. The whole-rock elemental geochemistry identified a felsic, granodioritic source rock, which is consistent with the general consensus regarding Gondwanan sediment provenance. Despite the evidence for sediment recycling, such as abundant dropstone clasts derived from sedimentary rocks, the low degree of chemical weathering and lack of zircon enrichment indicate a cold and arid palaeoclimate in its source area, which resulted in ice-rafted transportation of clasts and suspension deposition of fine-grained clastic sediments. Sm-Nd isotopic data and previously published detrital zircon U-Pb age spectra provide more detailed information on the source-rock composition, which was similar to that of the North Australian crustal element, suggesting that the central Sibumasu Terrane was located on the northern margin of north Australia during the late Paleozoic.