Genesis and tectonic setting of the Malaysian Waterfall granites and tin deposit: Constraints from LA–ICP (MC)-MS zircon U–Pb and cassiterite dating and Sr–Nd–Hf isotopes

Abstract

The Waterfall tin deposit, located in the south Peninsular Malaysia, is one of the earliest exploited tin deposit of the giant Southeast Asian Tin Belt (SATB) which is a world-class tin metallogenic belt and holds the largest tin resource and reserves in the world. It is a skarn-type deposit genetically associated with the Waterfall granites. Samples from the Waterfall biotite granites were analyzed using the LA-MC-ICPMS zircon U–Pb dating techniques, and the results show that these ages range from 241.2 ± 2.5 Ma (MSWD = 1.3) to 239.0 ± 3.4 Ma (MSWD = 1.2). In addition, these ages are consistent with weighted average age of 238.5 ± 1.7 Ma (MSWD = 0.23), using the LA-ICPMS cassiterite U–Pb dating techniques, indicating a coeval granitic magmatism and tin mineralization event. These granites are characterized by high contents of SiO2, Al2O3, Na2O and K2O, low contents of P2O5, enrichment in Th, U, Nb, Zr and Hf and depletion in Ba, Nb, Sr, P and Ti, indicating that they likely belong to I-type granites with high-K calc-alkaline and metaluminous to peraluminous signatures. The Sr–Nd isotopes show that the Waterfall granites are characterized by relatively low initial 87Sr/86Sr ratios of 0.706131–0.707291, slightly negative εNd(t) values of −5.63 to −5.30, and old two-stages Nd model ages of 1.28–1.26 Ga. The zircon εHf(t) values of the zircon grains from the Waterfall biotite granites vary from −2.4 to 0.5, with average crustal Hf model ages of 1.42–1.24 Ga. Based on the elemental and Sr–Nd isotopic compositions of the meta-igneous rocks in the Kontum massif, Indochina Block, a model using the amphibolite and gneiss as two endmembers indicates that the magma for the Waterfall granites were possibly originated from the partial melting of the meta-igneous rocks of the Kontum massif. The Waterfall granites were likely emplaced in a syn-collision setting, triggered by the subduction of the Paleo-Tethys ocean floor beneath the Indochina Block. These granitic rocks, enriched in tin, are in favor of the tin mineralization, resulting in the giant tin mineralization in the SATB.