DOI: 10.1016/j.palaeo.2017.02.023
论文题名: Influence of palaeoweathering on trace metal concentrations and environmental proxies in black shales
作者: Marynowski L. ; Pisarzowska A. ; Derkowski A. ; Rakociński M. ; Szaniawski R. ; Środoń J. ; Cohen A.S.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2017
卷: 472 起始页码: 177
结束页码: 191
语种: 英语
英文关键词: Gd/Yb
; Inorganic proxies
; Redox conditions
; REE
; Stable isotopes
; U/Th
; Weathering
英文摘要: The mineralogical and chemical compositions of Lower Carboniferous (Tournaisian) marine black shale from the Kowala quarry, the Holy Cross Mountains, Poland, were investigated. This study focuses on disturbances in palaeoenvironmental proxies caused by palaeoweathering, which progressively changed the major and trace element abundances. Palaeomagnetic investigations reveal that the Devonian – Carboniferous succession was weathered during the Permian-Triassic by the infiltration of oxidizing fluids related to karstification following post-Variscan exhumation. The weathering process led to vermiculitization of chlorite, partial dissolution of calcite and replacement of pyrite by hematite and goethite. Moreover, the concentrations of some trace metals, including Co, Cu, Pb, Mo, Ni, As and U, significantly decreased. Consequently, some elemental abundance ratios that are used as environmental proxies, including U/Th, Ni/Co and V/Cr, were altered. Elements that are bound to iron sulphides (e.g., Mo) appear to be especially prone to mobilization by even a lightly weathered black shale. The documented weathering, including changes in elemental concentrations, can potentially create misinterpretations of the original palaeoenvironmental conditions. In addition, the palaeoweathering of the studied samples appears to have substantially changed the carbon, oxygen, nitrogen and molybdenum stable isotope values. The nitrogen and molybdenum stable isotope ratios, in particular, appear to be most sensitive to the effects of weathering and therefore are good indicators of (palaeo)weathering processes. The major cause of these changes is the decay of organic matter and pyrite. For the organic carbon stable isotopes ratios, the main factor that controlls this process appears to be the preferential degradation of labile organic matter. A combination of the total organic carbon (TOC), total sulphur (TS) content, Mo concentration and stable isotope compositions seems to be the most useful for identify (palaeo)weathering. Our results suggest that reductions in TS and Mo in tandem with diminished Mo stable isotope values in the absence of obvious changes to the TOC content provide the most compelling evidence of (palaeo)weathering. © 2017 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/67887
Appears in Collections: 过去全球变化的重建
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作者单位: Faculty of Earth Sciences, University of Silesia, Będzińska 60, Sosnowiec, Poland; Institute of Geological Sciences, Polish Academy of Sciences, Research Centre in Kraków, ul. Senacka 1, Kraków, Poland; Institute of Geophysics, Polish Academy of Science, Ks. Janusza 64, Warszawa, Poland; School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes, United Kingdom
Recommended Citation:
Marynowski L.,Pisarzowska A.,Derkowski A.,et al. Influence of palaeoweathering on trace metal concentrations and environmental proxies in black shales[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2017-01-01,472