Studying the Lincang terrane is essential to understand the tectonic evolution of the Proto-Tethys in the Sanjiang region of Southwest China.However,there have been ongoing debates about its tectonic characte-ristics.This study focuses on the Lancang Group,which serves as the basement of the terrane.Our study presents zircon U-Pb chronology and whole-rock elemental composition of altered metavolcanic rocks in the area.The zircon U-Pb dating results indicate that these rocks formed during the Late Ordovician period,specifically at(457±2)Ma and(455±2)Ma.The protoliths of the 22 chlorite schists are from the low-potassium tholeiite series,while the protoliths of the six albite chlorite schists are basaltic-andesites from the high-potassium calc-alkaline-potassium basalt series.These rocks share similar characteristics with typical arc volcanic features,such as strong enrichment of light rare earth elements(LREEs),large-ion lithophile elements(LILEs),and negative anomalies of high field strength elements(HFSE).This evidence supports the idea that the Huimin magmatism was formed through the subduction of the Proto-Tethys Ocean to the Simao Block during the Ordovician-Silurian period.Therefore,we propose that the Lincang terrane may not be a distinct block with Precambrian basement,but rather a continental arc that formed through the subduction of the Proto-and Paleo-Tethys at the margin of the Simao Block.
Proto-Tethysmagmatic arcLincang terraneLancang Group
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