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TitleOrigin of the Upper Ordovician-lower Silurian cherts of the Yangtze block, South China, and their palaeogeographic significance
AuthorRan, B; Liu, S G; Jansa, L; Sun, W; Yang, D; Ye, Y H; Wang, S Y; Luo, C; Zhang, X; Zhang, C J
SourceJournal of Asian Earth Sciences vol. 108, 2015 p. 1-17,
Alt SeriesNatural Resources Canada, Contribution Series 20200232
PublisherElsevier Ltd
Mediapaper; on-line; digital
File formatpdf
Lat/Long WENS 102.0000 110.0000 34.0000 27.0000
Subjectsgeneral geology; Nature and Environment; Science and Technology; lithofacies; cherts; black shales; volcanic rocks; sandstones; paleogeography; Yangtze Block; Ordovician; Silurian
Illustrationslocation maps; stratigraphic columns; photographs; tables; composite sections; AFM diagrams; plots
Released2015 04 21
AbstractVolcanic rocks, black shales, calcareous sandstones and cherts occur in the Wufeng and Longmaxi formations, which cross late Katian through Rhuddanian exposed along the northern and central part of the Yangtze block, South China. The evidence provided by radiolarite occurrences, sedimentological features and immobile elements indicate that the silica in these rocks is sedimentary and not of hydrothermal origin. Precursors of chert were deposited on a continental margin, or in a deeper basin on the shelf, during blooms of radiolarians and times of decreased clastic input. Interbedded volcanic tuffs of rhyolitic to andesitic composition suggest the presence of a continental volcanic arc to the east-southeast. The large regional extent of bentonites documents explosive volcanicity resulting in silica saturation of waters, leading to high bioproductivity and radiolarian blooms. Deepening of the sedimentary environment is most probably the result of orogenesis generated by an accretion of the Cathaysia Block to the Yangtze Block during the Ordovician-Silurian transition. Increasing water depth together with a decrease in clastic input contributed to the development of the radiolarian cherts in the basin.

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