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Silicate bioweathering and biomineralization in lacustrine microbialites: ancient analogues from the Miocene Duero Basin, Spain

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Sanz Montero, M. Esther and Rodríguez Aranda, Juan Pablo (2009) Silicate bioweathering and biomineralization in lacustrine microbialites: ancient analogues from the Miocene Duero Basin, Spain. Geological magazine, 164 (4). pp. 527-539. ISSN 0016-7568

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Official URL: https://www.cambridge.org/core/journals/geological-magazine



Abstract

The Miocene dolomite-chert microbialites studied here offer a complete record of the geochemical cycles of silicate weathering and the subsequent formation of secondary products. The microbialites were formed in lacustrine systems during the Miocene of the Duero Basin, central Spain. Mineralogical, chemical and petrographic results provide evidence of the mediation of microbes in early weathering and by-product formation processes. Irrespective of the composition, the surfaces of the grains were subject to microbial attachment and concomitant weathering. Palaeo-weathering textures range from surface etching and pitting to extensive physical disaggregation of the minerals. Extreme silicate weathering led to the complete destruction of the silicate grains, whose prior existence is inferred from pseudomorphs exhibiting colonial textures like those recognized in the embedding matrix. Detailed petrographic and microanalytical examinations of theweathering effects in K-feldspars show that various secondary products with diverse crystallinity and chemical composition can coexist in the interior of a mineral. The coexistence of by-products is indicative of different microenvironmental conditions, likely created by microbial reactions. Thus, the presence of varied secondary products can be used as a criterion of biogenicity. Intensive alteration of P-bearing feldspars suggests that mineral weathering may have been driven by the nutrient requirements of the microbial consortium involved in the precipitation of dolomite. The rock record provides useful information on mineral weathering mediated by microbes.


Item Type:Article
Uncontrolled Keywords:Silicate dissolution, Microbial weathering, Biomineralization, Lake, Dolomite
Subjects:Sciences > Geology > Mineralogy
Sciences > Geology > Petrology
ID Code:58482
Deposited On:10 Jan 2020 12:16
Last Modified:13 Jan 2020 09:11

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