Petrogenesis for the Chiang Dao Permian High-Iron Basalt and Its Implication on the Paleotethyan Ocean in NW Thailand
The Changning-Menglian suture in SW Yunnan has been accepted as the Paleotethyan main ocean.However, it has been a matter of debate as to its southerly extension in NW Thailand (the Chiang Mai-Chiang Rai vs.Nan-Uttaradit zone).Our field investigation identified the high-iron basaltic rocks in the Chiang Dao Permian standard profile in NW Thailand.The high-iron rocks provide crucial records for understanding the controversy on the location of Paleotethyan main ocean in NW Thailand.The Early Permian high-iron samples show extremely high FeOt (20.96 wt.%-25.56 wt.%) and TiO2 (6.07 wt.%-6.34 wt.%) and low SiO2 (38.54 wt.%-43.46 wt.%) and MgO (1.61 wt.%-2.40 wt.%) contents.Such characteristics are similar to those of the Fenner differentiation trend rarely observed in the natural system, distinct from those of the normal Bowen trend.Their chondrite-normalized REE and primitive mantle-normalized patterns are generally similar to those of typical OIB.The initial 87Sr/86Sr ratios and εNd(t) values range from 0.704 677 to 0.705 103 and 3.16 to 3.48, respectively, falling near the field of typical OIB (oceanic-island basalt).These data synthetically suggest that the Chiang Dao high-iron rocks are the products of high-degree partial melting of peridotite with Fe-rich eclogitic blobs/streaks in response to a seamount setting.In comparison with the Permian tectonic setting in SW Yunnan and NW Thailand, it is inferred that the Paleotethyan Ocean was located between the Shan-Thai terrane of Sibumasu and Sukhothai arc along the Inthanon zone of the Chiang Mai-Chiang Rai rather than Nan-Uttaradit zones.
high-iron rock Fenner differentiation trend Chiang Dao OIB-like basalt Paleotethyan Ocean seamount setting
Yuzhi Zhang Yuejun Wang Boontarika Srithai Burapha Phajuy
School of Earth Science and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, China School of Earth Science and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, China; Department of Geological Sciences, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thai
国际会议
武汉
英文
425-434
2015-10-16（万方平台首次上网日期，不代表论文的发表时间）