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Journal of the Geological Society; 2000; v. 157; issue.3; p. 553-563
© 2000 Geological Society of London

Regular Article

Petrochemistry, U–Pb (zircon) age, and palaeotectonic setting of the Lampang volcanic belt, northern Thailand

S. M. BARR1, A. S. MACDONALD1, G. R. DUNNING2, P. OUNCHANUM3 & W. YAOWANOIYOTHIN4

1 Department of Geology, Acadia University, Wolfville, NS Canada B0P 1X0 (e-mail: sandra.barr{at}acadiau.ca)
2 Department of Earth Sciences, Memorial University, St John’s, Nfld Canada A1B 3X5
3 Department of Geological Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
4 M Thai Tower 1, All Seasons Place, 87 Wireless Road, Lumpini, Phathumwam, Bangkok 10330, Thailand

Scientific editing by Jennie Gilbert.

Two NE-trending belts of mainly subaerial dacitic to rhyolitic flows and tuffs occur in the area between the towns of Lampang and Denchai in northern Thailand. In the western belt (Doi Ton), the rocks have been pervasively altered to quartz keratophyre; rocks in the eastern belt (Doi Luang) are generally less altered. Mobile chemical components such as Na2O and K2O show wide variation, particularly in samples from the Doi Ton belt. However, low Zr/TiO2 ratios and low Nb and Ta contents support an origin at a convergent plate margin. A positive epsilon Nd value of +4.9 for rhyolite from the Doi Luang belt supports derivation from a primitive crustal source. A rhyolite sample from the Doi Luang belt yielded a U–Pb zircon age of 240 ± 1 Ma (early Mid-Triassic).

The Doi Ton and Doi Luang belts are part of the Lampang volcanic belt, which can be traced to the north into the Lincang–Jinghong volcanic belt in southern China. Comparison with published petrological data from the Lincang–Jinghong belt shows strong similarity, including the widespread development of keratophyric mineralogy and chemistry. The Lampang–Lincang–Jinghong belt formed at an early Mid-Triassic convergent plate margin, and is similar in age and tectonic setting to the more mafic Phetchabun volcanic belt on the east side of the Nan River suture zone. These data constrain the timing of final amalgamation between the Indochina and Shan-Thai terranes to Mid-Triassic or younger.


Keywords: Lampang, Thailand, Triassic, tectonics, volcanic arc.




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S. M. Barr, A. S. Macdonald, P. Ounchanum, and M. A. Hamilton
Age, tectonic setting and regional implications of the Chiang Khong volcanic suite, northern Thailand
Journal of the Geological Society, 2006; 163: 1037 - 1046.
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