Early Paleozoic trondhjemite, gneissic granite and alkali granite in southern Yunnan preserve important records for the Prototethyan tectonic evolution and regional correlations. Zircon ages suggest that these granitoids were emplaced during 476–436 Ma. The trondhjemites are characterized by high Na2O and low K2O contents, with εNd (t) values of −1.9 to −3.5 and εHf (t) values of −2.8 to +3.9. The trondhjemites were derived from an amphibolite source with a juvenile mafic component. The gneissic granites belong to the metaluminous low-K calc-alkaline series with εNd (t) value of −6.2 and εHf (t) values of −5.0 to −0.4. The alkali granites belong to the high-K calc-alkaline series and yield εNd (t) values of −10.1 to −10.7 and εHf (t) values of −7.9 to −2.3. The gneissic granites were derived from an “ancient” lower mafic crust, whereas the alkali granites were derived from a meta-sedimentary source. These granitoids were formed during the subduction of Prototethyan Ocean beneath the Simao Block, and can compare with those from the Truong Son and Tam Ky-Phuoc Son zones in southern Laos. Our study, along with these Early Paleozoic igneous from southern Laos, central Vietnam and Malay Peninsula suggests an arc-back-arc system along the northern margin of Gondwana.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5322386
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