Age, tectonic setting and regional implications of the Chiang Khong volcanic suite, northern Thailand

The Chiang Kahong volcanic suite forms the northeastern part of the Tak-Chiang Khong volcanic belt in the Sukhothai terrane of northern Thailand. It consists mainly of subaerial andesitic to rhyolitic tuffaceous rocks. A rhyolitic tuff yielded a Middle Triassic U-Pb (zircon) age of 232.9 [+ or -] 0.4 Ma. The suite displays calc-alkalic chemical trends and Nb, P, and Ti depletion characteristic of subduction-related magmatism. Based on petrological similarities, the suite is correlated with the c. 240 Ma Lampang volcanic rocks located farther to the SW in the Tak Chiang Khong belt, and with volcanic rocks of similar age in the Lincang--Jinghong belt in Yunnan, in the western part of the Simao block. These correlations support the placement of the Palaeo-Tethyan suture to the west of the Sukhothai terrane.