RT Journal Article
T1 Bioinduced precipitation of barite and celestite in dolomite microbialites Examples from Miocene lacustrine sequences in the Madrid and Duero Basins, Spain
A1 Sanz Montero, María Esther
A1 Rodríguez Aranda, Juan Pablo
A1 García del Cura, M. Ángeles
AB This paper provides an ancient analogue for biologically mediated celestite and barite formation in dolomite precipitating microbial mats developed in lacustrine environments during the Miocene. Barite and celestite occurrences were studied in three temporally and spatially separated sedimentary successions: S1 and S2 in the Madrid Basin and S3 in the Duero Basin. In S1, macrocrystalline selenite gypsum occurs as laterally continuous beds; in the two other successions (S2 and S3), calcite pseudomorphs of lenticular gypsum aggregates are hosted in dolomite beds as evidence for the former presence of this evaporite. In S1, only celestite is associated with dolomite. Celestite crystals occur as both intergrown clusters, concentrated in pockets likely created by the dissolution of intrasedimentary anhydrite precursors, and as single precipitates associated with dolomite masses that replace selenite gypsum. Celestite crystals are nucleated commonly on organic substances that are pervasively associated with them. In S2 and S3, scarce single celestite crystals are restricted to calcite pseudomorphs after gypsum, whereas barite is the sulphate precipitated in the pseudomorphs' surroundings. Barite is commonly present as patchy poikilotopic crystals which include microbial structures and is embedded in organic matter. Additionally, barite is found as a secondary precipitate within Ba-bearing feldspars. Feldspar weathering is, thus, envisaged as amajor source of barium at these sites. Petrographical, isotopic and compositional observations point out that the barite and celestite formation was not caused by abiological processes only. Rather, the patchy distribution of the sulphates, close links to organic matter with biogenic isotope signatures, and inclusion of microbial structures, such as biologically mediated dolomite, provides evidence for the involvement of microbes in the formation of the sulphates. The coprecipitation of barite and celestite with dolomite entails complex interactions between different microorganisms and reinforces the biological formation of dolomite in saline lakes.
PB Elsevier
SN 0037-0738
YR 2009
FD 2009
LK https://hdl.handle.net/20.500.14352/52362
UL https://hdl.handle.net/20.500.14352/52362
LA eng
DS Docta Complutense
RD 10 abr 2025