The Chiang Khong segment of the Chiang Khong-Lampang-Tak Volcanic Belt is composed of three broadly meridional sub-belts of mafic to felsic volcanic, volcaniclastic, and associated intrusive rocks. Associated sedimentary rocks are largely non-marine red beds and conglomerates. Three representative Chiang Khong lavas have Late Triassic (223-220 Ma) laser ablation inductively coupled mass-spectroscopy U-Pb zircon ages. Felsic-dominated sequences in the Chiang Khong Western and Central Sub-belts are high-K calc-alkaline rocks that range from basaltic to dominant felsic lavas with rare mafic dykes. The Western Sub-belt lavas have slightly lower high field strength element contents at all fractionation levels than equivalent rocks from the Central Sub-belt. In contrast, the Eastern Sub-belt is dominated by mafic lavas and dykes with compositions transitional between E-mid-oceanic ridge basalt and back-arc basin basalts. The Eastern Sub-belt rocks have higher FeO* and TiO2 and less light rare earth element enrichment than basalts in the high-K sequences. Basaltic and doleritic dykes in the Western and Central sub-belts match the composition of the Eastern Sub-belt lavas and dykes. A recent geochemical study of the Chiang Khong rocks concluded that they were erupted in a continental margin volcanic arc setting. However, based on the dominance of felsic lavas and the mainly non-marine associated sediments, we propose an alternative origin, in a post-collisional extensional setting. A major late Middle to early Late Triassic collisional orogenic event is well documented in northern Thailand and Yunnan. We believe that the paucity of radiometric dates for arc-like lavas in the Chiang Khong-Lampang-Tak Volcanic Belt that precede this orogenic event, coupled with the geochemistry of the Chiang Khong rocks, and strong compositional analogies with other post-collisional magmatic suites, are features that are more typical of volcanic belts formed in a rapidly evolving post-collisional, basin-and range-type extensional setting.

Item Type:	Refereed Article
Keywords:	Thailand, geology, Chiang Kong-Lampang volcanic belt, Late Triassic volcanism, tectonics
Research Division:	Earth Sciences
Research Group:	Geology
Research Field:	Tectonics
Objective Division:	Mineral Resources (excl. Energy Resources)
Objective Group:	Mineral Exploration
Objective Field:	Mineral Exploration not elsewhere classified
Author:	Srichan, W (Mr Weerapan Srichan)
Author:	Crawford, AJ (Professor Anthony Crawford)
Author:	Berry, RF (Associate Professor Ron Berry)
ID Code:	62079
Year Published:	2009
Web of Science® Times Cited:	13
Deposited By:	Centre for Ore Deposit Research - CODES CoE
Deposited On:	2010-03-09
Last Modified:	2010-04-15
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