Influences of Sedimentary Environments and Volcanic Sources on Diagenetic Alteration of Volcanic Tuffs in South China

Permian-Triassic (P-Tr) altered volcanic ashes (tuffs) are widely distributed within the P-Tr boundary successions in South China. Volcanic altered ashes from terrestrial section-Chahe (CH) and marine section-Shangsi (SS) are selected to further understand the influence of sedimentary environments a...

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Bibliographic Details
Published in:Scientific reports 2018-05, Vol.8 (1), p.7616-12, Article 7616
Main Authors: Gong, Nina, Hong, Hanlie, Huff, Warren D., Fang, Qian, Bae, Christopher J., Wang, Chaowen, Yin, Ke, Chen, Shuling
Format: Article
Language:English
Subjects:
140/125
704/2151/209
704/2151/330
704/2151/3930
704/2151/414
Ashes
Clay minerals
Humanities and Social Sciences
Illite
Isotopes
Kaolinite
Minerals
multidisciplinary
Permian
Science
Science (multidisciplinary)
Sedimentary environments
Triassic
Weathering
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Summary:Permian-Triassic (P-Tr) altered volcanic ashes (tuffs) are widely distributed within the P-Tr boundary successions in South China. Volcanic altered ashes from terrestrial section-Chahe (CH) and marine section-Shangsi (SS) are selected to further understand the influence of sedimentary environments and volcanic sources on diagenetic alterarion on volcanic tuffs. The zircon 206 Pb/ 238 U ages of the corresponding beds between two sections are almost synchronous. Sedimentary environment of the altered tuffs was characterized by a low pH and did not experience a hydrothermal process. The dominant clay minerals of all the tuff beds are illite-smectite (I-S) minerals, with minor chlorite and kaolinite. I-S minerals of CH (R3) are more ordered than SS (R1), suggesting that CH also shows a higher diagenetic grade and more intensive chemical weathering. Besides, the nature of the volcanism of the tuff beds studied is derived from different magma sources. The clay mineral compositions of tuffs have little relation with the types of source volcanism and the depositional environments. Instead, the degree of the mixed-layer clay minerals and the REE distribution are mainly dependent upon the sedimentary environments. Thus, the mixed-layer clay minerals ratio and their geochemical index can be used as the paleoenvironmental indicator.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-018-26044-w