Geochemistry of Triassic Siliceous Rocks of the Muyinhe Formation in the Changning-Menglian Belt of Southwest China
The Changning-Menglian belt, distributed over southwestern Yunnan Province in Southwest China, contains oceanic rocks that are considered to be remnants of the Paleotethys.This study observed Triassic siliceous rocks of the Muyinhe Formation in the Changning-Menglian belt and analyzed their geochemistry.The samples have high concentrations of SiO2 (81.65 wt.%-88.38 wt.%;average: 84.99 wt.%±2.14 wt.%).Most of the samples were plotted in the non-hydrothermal field on the Al-Fe-Mn diagram.Most of the samples were plotted in the continental margin field on the Fe2O3/TiO2-Al2O3/(Al2O3+Fe2O3) and (La/Ce)N-Al2O3/(Al2O3+Fe2O3) diagrams.Moreover, the samples show a flat REE (rare earth element) pattern normalized to NASC (North America shale composite).These geochemical results, in addition to the lack of rhythmical bedding of the siliceous rocks, strongly suggest that the siliceous rocks are unlikely to represent pelagic deposits.Although previous studies have suggested that the siliceous rocks are pelagic deposits, the present results indicate that the extent of the pelagic ocean basins in the Paleotethys during the Triassic is probably less than previously believed.These non-pelagic deposits may represent the closure stage of the Paleotethys.
geochemistry Triassic siliceous rock Paleotethys Muyinhe Formation Changning-Menglian belt
Tsuyoshi Ito Xin Qian Qinglai Feng
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences,
国际会议
武汉
英文
403-411
2015-10-16（万方平台首次上网日期，不代表论文的发表时间）