Triassic felsic magmatism in SE Peninsular Malaysia: Petrogenesis and geodynamic implications for the Eastern Paleotethyan tectonic transition.

Middle–Late Triassic volcanism and contemporary granitoids in East Malaya provide significant insights into the magmatic evolution and geodynamic processes of the Paleotethyan Ocean in SE Asia. This paper presents new zircon ages and whole-rock geochemical data including Sr-Nd-Pb-Hf isotopic analyses for newly identified felsic volcanic rocks and granites in SE Peninsular Malaysia. Zircon geochronological data constrain their formation time at 238–235 Ma. All samples have relatively high SiO 2 contents with enrichment in light rare earth elements but have negative anomalies at Nb, Ta, Ti, and Eu on spidergrams. Calculated zircon saturation temperatures are between 840 °C and 957 °C. Samples have (87Sr/86Sr) i ratios between 0.70501 and 0.71014 and ε Nd (t) values ranging from −6.6 to −5.9, with (206Pb/204Pb) i = 18.45–18.77, (207Pb/204Pb) i = 15.68–15.71, and (208Pb/204Pb) i = 38.88–38.97. The zircon in-situ ε Hf (t) values and T DM2 ages range from −5.6 to +4.5 and 1.62 Ga to 0.98 Ga, respectively. The primary melting source which produced these felsic volcanic rocks and granites was Proterozoic crustal rocks with a juvenile middle-lower crustal component. Triassic volcanism in SE Peninsular Malaysia northerly correlates with synchronous volcanic rocks in the Lancangjiang and Chiang Khong-Lampang-Tak volcanic zones. Our data, along with regional observations, indicate that these volcanic rocks and granites formed in a localized extensional setting in response to the Paleotethyan slab breakoff. While the initial collision of Sibumasu with East Malaya may have occurred at ∼237 Ma. [Display omitted] • Felsic volcanic rocks and granites in SE Peninsular Malaysia formed at 238–235 Ma. • Triassic felsic magmatism formed in response to the Paleotethyan slab breakoff. • The initial collision between Sibumasu and East Malaya might occur at ∼237 Ma. • Felsic volcanic rocks in East Malaya can correlate with the LCJ and CLT zones. [ABSTRACT FROM AUTHOR]