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Title: | Graphite–(Mo,W)S2 intergrowth as a palaeoenvironmental proxy in metasedimentary rocks |
Title of periodic: | Lithos |
metadata.dc.title.subtitlejournal: | An International Journal of Petrology, Mineralogy and Geochemistry |
Authors: | Cabral, Alexandre Raphael Zeh, Armin Viana, Nívea Cristina da Silva Schirmer, Thomas Lehmann, Bernd |
Affiliation: | Centro de Desenvolvimento da Tecnologia Nuclear,CDTN, Belo Horizonte, MG, Brazil Institut für Angewandte Geowissenschaften, Karlsruhe, Germany Vale Manganês S.A., Conselheiro Lafaiete, MG, Brazil Institute of Disposal Research, Technische Universität Clausthal, Clausthal-Zellerfeld, Germany Institute of Disposal Research, Technische Universität Clausthal, Clausthal-Zellerfeld, Germany |
Issue Date: | 2017 |
Keywords: | Tungsten-bearing molybdenite Gerais;Graphite;Molybdenum proxy;Queluzite;Barbacena greenstone belt;Minas Gerais |
Abstract: | Molybdenum enrichment in pristine organic-C-rich sedimentary rocks forms the basis for inferring the presence of dissolved oxygen in seawater. Organic matter removes dissolved hexavalent Mo from seawater where anoxic and euxinic conditions are attained. However, it is unknown whether this Mo-based proxy is retained under metamorphic conditions where organic C is no longer preserved. Here, we describe aggregates of graphite and molybdenite (MoS2) containing up to 21 mass per cent of W as tungstenite (WS2) in solid solution. These aggregates are disseminated in a sulfide-rich Mn-silicate-carbonate rock (queluzite), metamorphosed under amphibolite-facies conditions within the Archaean Barbacena greenstone belt in Minas Gerais, Brazil. Our finding indicates that: (i) W is, like Mo, a palaeoenvironmental proxy; (ii) the W proxy is sensitive to high fS2/fO2 environments; (iii) both Mo and W proxies survive amphibolite-facies overprint as (Mo,W)S2 intergrown with graphite. Archaean greenstones are potential candidates for storing palaeoenvironmental information as (Mo,W)S2–graphite intergrowths. |
Access: | L |
Appears in Collections: | Artigo de periódico |
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File | Description | Size | Format | |
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lithos.pdf | 821.32 kB | Adobe PDF | View/Open |
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