The studies of the Tethys tectonic belt in Southeast Asia mainly focus on the evolution of the Paleo-Tethys in the Late Paleozoic,while the studies of the Proto-Tethys evolution immediately are pretty weakThe present study focuses on zircon U-Pb geochronology,geochemistry and zircon Lu-Hf isotopes of granites and hornblende gabbros from northern Thailand.These magmatic rocks yielded zircon U-Pb weighted mean age of 367-361 Ma.The geologic age is the Late Devonian.The northern Thailand granites are the high-K calc-alkaline A2 type granites,with the geochemical characteristics of relatively enriched LILE and relatively depleted HFSE,with obvious negative anomalies of Nb,Ta,Sr and Ti.The Hf isotopes have positive εHf(t)values(+5.43-+10.91)with TDM2 ages of 1 015.0-668.9 Ma,indicating a juvenile mafic lower crust source.The hornblende gabbros showhigh Al2O3、Zr and Nbcontents,but low contents of TiO2 and Ni,with the geochemical characteristics ofrelatively enriched LILE and relatively depleted HFSE,with the distinctly negative Nb and Ta anomalies,similar to the characteristics of island arc calc-alkaline basalts.Positive εHf(t)values(+1.24-+9.11)and high Mg#(50.0-64.8)indicate that it originates from the depleted mantle wedge.Based on the U-Pb age,Hf isotope and geochemical characteristics of the magmatic rocks in northern Thailand,it is believed that they were formed in the Late Devonian post-collisional extension-related tectonic setting,which can be compared with the corresponding the Proto-Tethys geological records in eastern Myanmar and southwestern Yunnan.The results provide evidence for the evolution of the Proto-Tethys in southwest Yunnan and Southeast Asia.
Late DevonianTethysmagmatic rockpost-collisionnorthern Thailandgeochemistry
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