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- Title
Geochemistry of Triassic siliceous rocks of the Muyinhe Formation in the Changning-Menglian belt of Southwest China.
- Authors
Ito, Tsuyoshi; Qian, Xin; Feng, Qinglai
- Abstract
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 SiO (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 FeO/TiO-AlO/(AlO+FeO) and (La/Ce)N-AlO/(AlO+FeO) 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.
- Subjects
CHINA; GEOCHEMISTRY; SILICEOUS rocks; SHALE; GEOLOGICAL basins; MARINE sediments
- Publication
Journal of Earth Science, 2016, Vol 27, Issue 3, p403
- ISSN
1674-487X
- Publication type
Article
- DOI
10.1007/s12583-016-0672-x