The dolomite problem: Stable and radiogenic isotope clues

2005 ◽  
pp. 49-68 ◽  
Author(s):  
Lynton S. Land
Keyword(s):  
Radiogenic Isotope ◽  
Dolomite Problem

Radiogenic Isotope Geology

Physics Today ◽  
1996 ◽  
Vol 49 (6) ◽  
pp. 60-60 ◽  
Author(s):  
Alan P. Dickin ◽  
Richard Muller
Keyword(s):  
Radiogenic Isotope

Late Paleocene Arctic coastal climate inferred from molluscan stable and radiogenic isotope ratios

2001 ◽  
Vol 170 (1-2) ◽  
pp. 101-113 ◽  
Author(s):  
Aradhna Tripati ◽  
James Zachos ◽  
Louie Marincovich ◽  
Karen Bice
Keyword(s):  
Isotope Ratios ◽  
Radiogenic Isotope ◽  
Late Paleocene ◽  
Coastal Climate

A fast, single column extraction chromatography method for the isolation of Neodymium from iron-rich materials prior to radiogenic isotope ratio measurements

2022 ◽  
Author(s):  
Abdelmouhcine GANNOUN ◽  
Krzysztof SUCHORSK ◽  
Christian Pin
Keyword(s):  
Extraction Chromatography ◽  
Isotope Ratio ◽  
Separation Method ◽  
Chromatography Method ◽  
Radiogenic Isotope ◽  
Synergistic Enhancement ◽  
Isotopic Analyses ◽  
Single Column ◽  
Column Extraction ◽  
Isotope Ratio Measurements

A novel separation method is described for the separation of Nd from Fe-rich, silicate samples in view of isotopic analyses. The procedure is based on the synergistic enhancement of the...

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>

Radiogenic isotope geochemistry

2012 ◽  
pp. 220-357
Author(s):  
Claude J. Allegre ◽  
Christopher Sutcliffe
Keyword(s):  
Isotope Geochemistry ◽  
Radiogenic Isotope

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.

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