Geochemical and geochronological constrains on the Chiang Khong volcanic rocks （northwestern Thailand） and its tectonic implications  

作　　者：Xin QIAN Qinglai FENG Chongpan CHONGLAKMANI Denchok MONJAI 

机构地区：[1]State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Wuhan 430074, China [2]School of Geotechnology, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand

出　　处：《Frontiers of Earth Science》2013年第4期508-521,共14页地球科学前沿（英文版）

摘　　要：Volcanic rocks in northwestern Thailand exposed dominantly in the Chiang Khong area, are commonly considered to be genetically linked to the tectonic evolution of the Paleo-Tethyan Ocean. The volcanic rocks consist mainly of andesitic to rhyolitic rocks and are traditionally mapped as Permian-Triassic sequences. Our zircon U-Pb geochronological results show that two andesitic samples （TL-1-B and TL-31-B）, are representative of the Doi Yao volcanic zone, and give a mean weighted age of 241.2-＋-4.6 Ma and 241.7-＋-2.9 Ma, respectively. The rhyolitic sample （TL-32-B1） from the Doi Khun Ta Khuan volcanic zone erupted at 238.3＋3.8 Ma. Such ages indicate that Chiang Khong volcanic rocks erputed during the early Middle Triassic period. Seven samples from the Doi Yao and Doi Khun Ta Khuan zones exhibit an affinity to arc volcanics. Three rhyolitic samples from the Chiang Khong area have a geochemical affinity to both arc and syn-eollisional volcanic rocks. The Chiang Khong arc volcanic rocks can be geochemically compared with those in the Lampang area in northern Thailand, also consistent with those in Jinghong area of southwestern Yunnan. This indicates that the Chiang Rai arc-volcanic zone might northwardly link to the Lancangjiang volcanic zone in southwestern China.Volcanic rocks in northwestern Thailand exposed dominantly in the Chiang Khong area, are commonly considered to be genetically linked to the tectonic evolution of the Paleo-Tethyan Ocean. The volcanic rocks consist mainly of andesitic to rhyolitic rocks and are traditionally mapped as Permian-Triassic sequences. Our zircon U-Pb geochronological results show that two andesitic samples （TL-1-B and TL-31-B）, are representative of the Doi Yao volcanic zone, and give a mean weighted age of 241.2-＋-4.6 Ma and 241.7-＋-2.9 Ma, respectively. The rhyolitic sample （TL-32-B1） from the Doi Khun Ta Khuan volcanic zone erupted at 238.3＋3.8 Ma. Such ages indicate that Chiang Khong volcanic rocks erputed during the early Middle Triassic period. Seven samples from the Doi Yao and Doi Khun Ta Khuan zones exhibit an affinity to arc volcanics. Three rhyolitic samples from the Chiang Khong area have a geochemical affinity to both arc and syn-eollisional volcanic rocks. The Chiang Khong arc volcanic rocks can be geochemically compared with those in the Lampang area in northern Thailand, also consistent with those in Jinghong area of southwestern Yunnan. This indicates that the Chiang Rai arc-volcanic zone might northwardly link to the Lancangjiang volcanic zone in southwestern China.

关 键 词：volcanic rocks GEOCHEMISTRY zircon U-Pb age early Middle Triassic Chiang Khong northwestern Thailand 

分 类 号：P588.14[天文地球—岩石学] P618.510.4[天文地球—地质学]