摘要
The characteristics of Late Permian-Early Triassic (P2-T1) continent marginal arc-volcanic rocks on the eastern side of the ocean-ridge/oceanic island basalts in the Chiang Mai belt were analyzed on the basis of REE, trace elements and geotectonic setting. These volcanic rocks consist of basaltic andesite, andesite and rhyolite, belonging to mainly calc-alkaline series with minor tholeiitic series. Chemical compositions of the volcanic rocks are characterized by high content of Al2O3. REE distribution patterns are of the LREE-enrichment of rightward incline type. Large cation elements are highly enriched and the U and Th are also enriched contrast with the depleted Ti, Cr and P. This result is of great importance in exploring the evolution of the paleo-Tethys in the Chiang Mai belt.