Nanoscale Pathway of Modern Dolomite Formation in a Shallow, Alkaline Lake

Autor(en)

Patrick Meister, Silvia Frisia, István Dódony, Péter Pekker, Zsombor Molnár, Stephanie Neuhuber, Susanne Gier, Ivett Kovács, Attila Demény, Mihály Pósfai

Abstrakt

Dolomite [CaMg(CO

₃)

₂] formation under Earth surface conditions is considered largely inhibited, yet protodolomite (with a composition similar to dolomite but lacking cation ordering), and in some cases also dolomite, was documented in modern shallow marine and lacustrine, evaporative environments. Authigenic carbonate mud from Lake Neusiedl, a shallow, episodically evaporative lake in Austria consists mainly of Mg-calcite with zoning of Mg-rich and Mg-poor regions in μm-sized crystals. Within the Mg-rich regions, high-resolution transmission electron microscopy revealed < 5-nm-sized domains with dolomitic ordering, i.e., alternating lattice planes of Ca and Mg, in coherent orientation with the surrounding protodolomite. The calcite with less abundant Mg does not show such domains but is characterized by pitted surfaces and voids as a sign of dissolution. These observations suggest that protodolomite may overgrow Mg-calcite as a result of the changing chemistry of the lake water. During this process, oscillating concentrations (in particular of Mg and Ca) at the recrystallization front may have induced dissolution of Mg-calcite and growth of nanoscale domains of dolomite, which subsequently became incorporated as ordered domains in coherent orientation within less ordered regions. It is suggested that this crystallization pathway is capable of overcoming, at least at the nanoscale, the kinetic barrier to dolomite formation.

Organisation(en)

Institut für Geologie, Department für Evolutionsbiologie

Externe Organisation(en)

University of Pannonia, Hungarian Academy of Sciences

Journal

Crystal Growth & Design

Band

23

Seiten

3202–3212

Anzahl der Seiten

11

ISSN

1528-7483

DOI

https://doi.org/10.1021/acs.cgd.2c01393

Publikationsdatum

2022

Peer-reviewed

Ja

ÖFOS 2012

105104 Erosion, 105116 Mineralogie, 105121 Sedimentologie

ASJC Scopus Sachgebiete

Condensed Matter Physics, Allgemeine Chemie, Allgemeine Materialwissenschaften

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/4dadfcf6-e30b-400b-aa53-a7e01cdc63a0