On the growth of witherite and its replacement by the Mg-bearing double carbonate norsethite: Implications for the dolomite problem

2018 ◽  
Vol 103 (2) ◽  
pp. 252-259 ◽  
Author(s):  
Michael Lindner ◽  
Guntram Jordan
Keyword(s):  
Dolomite Problem

From poorly-ordered precursors to crystals: Factors contributing to spherulitic growth of dolomite

2021 ◽  
Author(s):  
Juan Diego Rodriguez Blanco ◽  
Adrienn Maria Szucs
Keyword(s):  
Unified Model ◽  
Formation Mechanisms ◽  
Formation Processes ◽  
Ambient Conditions ◽  
Contributing Factors ◽  
Geological Record ◽  
Spherulitic Growth ◽  
Dolomite Problem ◽  
Dolomite Formation ◽  
Dolomite Precipitation

<p>Dolomite is one of the most abundant carbonate minerals in the geological record, yet it barely forms in the present. The contrast in the abundance of dolomite between geological and modern records combined with the impossibility of synthesizing stoichiometric dolomite in the laboratory at ambient conditions are known as the 'dolomite problem'. This enigma has been in the scope of research for decades, trying to understand dolomite formation, mechanisms and the contributing factors. Dolomite is known to form via two abiotic mechanisms; through (1) dolomitization or (2) dolomite cementation. Also, the contribution of microorganisms can result in biotic dolomite crystallization. The mechanisms of dolomite formation at the molecular and nanoscale in biotic and abiotic environments are relatively well-described, but we still struggle to develop a unified model of dolomite formation in modern and ancient settings. In this contribution, we summarize the development of research related to the dolomite formation processes and in particular the direct dolomite precipitation via spherulitic growth of proto-dolomite.</p>

scholarly journals Oxygen isotope composition of the Phanerozoic ocean and a possible solution to the dolomite problem

2018 ◽  
Vol 115 (26) ◽  
pp. 6602-6607 ◽  
Author(s):  
Uri Ryb ◽  
John M. Eiler
Keyword(s):  
Oxygen Isotope ◽  
Isotope Exchange ◽  
Isotope Composition ◽  
Temporal Variations ◽  
Oxygen Isotope Exchange ◽  
Diagenetic Alteration ◽  
Isotope Studies ◽  
Dolomite Problem ◽  
Clumped Isotope

The18O/16O of calcite fossils increased by ∼8‰ between the Cambrian and present. It has long been controversial whether this change reflects evolution in the δ18O of seawater, or a decrease in ocean temperatures, or greater extents of diagenesis of older strata. Here, we present measurements of the oxygen and ‟clumped” isotope compositions of Phanerozoic dolomites and compare these data with published oxygen isotope studies of carbonate rocks. We show that the δ18O values of dolomites and calcite fossils of similar age overlap one another, suggesting they are controlled by similar processes. Clumped isotope measurements of Cambrian to Pleistocene dolomites imply crystallization temperatures of 15–158 °C and parent waters having δ18OVSMOWvalues from −2 to +12‰. These data are consistent with dolomitization through sediment/rock reaction with seawater and diagenetically modified seawater, over timescales of 100 My, and suggest that, like dolomite, temporal variations of the calcite fossil δ18O record are largely driven by diagenetic alteration. We find no evidence that Phanerozoic seawater was significantly lower in δ18O than preglacial Cenozoic seawater. Thus, the fluxes of oxygen–isotope exchange associated with weathering and hydrothermal alteration reactions have remained stable throughout the Phanerozoic, despite major tectonic, climatic and biologic perturbations. This stability implies that a long-term feedback exists between the global rates of seafloor spreading and weathering. We note that massive dolomites have crystallized in pre-Cenozoic units at temperatures >40 °C. Since Cenozoic platforms generally have not reached such conditions, their thermal immaturity could explain their paucity of dolomites.

scholarly journals Can Primary Ferroan Dolomite and Ankerite Be Precipitated? Its Implications for Formation of Submarine Methane-Derived Authigenic Carbonate (MDAC) Chimney

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 413 ◽  
Author(s):  
Fan Xu ◽  
Xuelian You ◽  
Qing Li ◽  
Yi Liu
Keyword(s):  
Iron Reduction ◽  
Extracellular Polymeric Substances ◽  
Microbial Culture ◽  
Reduction Zone ◽  
Secondary Products ◽  
Iron Reducing Bacteria ◽  
Sulfate Reducing ◽  
Dolomite Problem ◽  
Reducing Bacteria ◽  
Ferroan Dolomite

Microbes can mediate the precipitation of primary dolomite under surface conditions. Meanwhile, primary dolomite mediated by microbes often contains more Fe2+ than standard dolomite in modern microbial culture experiments. Ferroan dolomite and ankerite have been regarded as secondary products. This paper reviews the process and possible mechanisms of microbial mediated precipitation of primary ferroan dolomite and/or ankerite. In the microbial geochemical Fe cycle, many dissimilatory iron-reducing bacteria (DIRB), sulfate-reducing bacteria (SRB), and methanogens can reduce Fe3+ to Fe2+, while SRB and methanogens can also promote the precipitation of primary dolomite. There are an oxygen respiration zone (ORZ), an iron reduction zone (IRZ), a sulfate reduction zone (SRZ), and a methanogenesis zone (MZ) from top to bottom in the muddy sediment diagenesis zone. DIRB in IRZ provide the lower section with Fe2+, which composes many enzymes and proteins to participate in metabolic processes of SRB and methanogens. Lastly, heterogeneous nucleation of ferroan dolomite on extracellular polymeric substances (EPS) and cell surfaces is mediated by SRB and methanogens. Exploring the origin of microbial ferroan dolomite may help to solve the “dolomite problem”.

Structure and reactivity of the dolomite (104)–water interface: New insights into the dolomite problem

2007 ◽  
Vol 71 (3) ◽  
pp. 566-579 ◽  
Author(s):  
P. Fenter ◽  
Z. Zhang ◽  
C. Park ◽  
N.C. Sturchio ◽  
X.M. Hu ◽  
...  
Keyword(s):  
Water Interface ◽  
Dolomite Problem

Surface–water interactions in the dolomite problem

2001 ◽  
Vol 3 (15) ◽  
pp. 3217-3221 ◽  
Author(s):  
Nora H. de Leeuw ◽  
Stephen C. Parker
Keyword(s):  
Surface Water ◽  
Dolomite Problem
Sign in / Sign up

Export Citation Format

Share Document