| Citation: | Jiangfeng Qin, Shaocong Lai, Guowei Zhang, Chunrong Diwu, Yong-fei Li. Zircon LA-ICP MS U-Pb Dating of the Longkang Andesitic Ignimbrites from Jiuzhaigou: Evidence of the Mianlue Suture Westward Extension. Journal of Earth Science, 2008, 19(1): 47-53.
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Genesis of metasedimentary-volcanics outcroped in Kangxian-Pipasi-Nanping (康县－琵琶寺－南坪) tectonic zone is closely related with tectonic evolution of the Mianlue (勉略) Ocean. In the west end of Kangxian-Pipasi-Nanping tectonic zone, there are hundred meters of andesitic ignimbrites and tuffites. Zircon U-Pb dating on these volcanics has great significance to the tectonic implication of the volcanic rocks. Zircons from an ignimbrite sample (JZG-L) have been collected from Yazhagou (牙扎沟) in the east end of the Tazang-Longkang (塔藏－隆康) Section for LA-ICP MS U-Pb dating. The zircons from Longkang andesitic ignimbrites are magmatic genesis with oscillatory zoning and high U ((35–750) ppm), Th ((311–717) ppm) contents with high Th/U (0.44–1.30) ratios. The measured 206Pb/238U ratios are in good analytical precision, yielding a weighted mean age of (246±3) Ma (
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