Molybdenum and sulfur incorporation as oxyanion substitutional impurities in calcium carbonate minerals: A computational investigation
Graphical abstract
Introduction
Major volcanic eruptions have a strong effect on both the local and global climate. The cooling effect that follows large eruptions can in some cases last for decades after the actual eruption (Robock, 2000; Sigl et al., 2013; Zielinski, 2000). Much of the knowledge about the impact of volcanic eruptions on climate comes from paleo-volcanic records such as sulfate concentrations in ice cores (Severi et al., 2012; Yalcin et al., 2007; Zielinski et al., 1994), tree-rings (McCarroll and Loader, 2004) and marine and lake sediments (Lowe, 2011; Voelker, 2002). During the last decade, speleothems have been extensively studied as a new archive for paleo-volcanic activity (Badertscher et al., 2014; Fairchild and Treble, 2009; Finch et al., 2001; Ünal-İmer et al., 2015). This archive has been revealed to be a multi-proxy source of information on climatic and environmental changes. Speleothem-based records such as trace element concentrations (Hartland et al., 2012), oxygen and carbon isotopes of calcite and hydrogen and oxygen isotopes of fluid inclusion water (Affolter et al., 2019; Fleitmann et al., 2009; Marshall et al., 2009) provide valuable information on decadal- to millennial-scale changes in precipitation and temperature. When compared to previous sources of paleo-volcanic activity data, speleothems have two important advantages. First, it is much easier to determine their absolute age accurately using uranium-series dating (Dorale et al., 2004; St Pierre et al., 2009). Second, they can often be found in locations proximal to volcanoes (e.g. Badertscher et al., 2014). Comparatively, in ice cores, it is difficult to separate high and low latitudinal eruptions and therefore determine the location of the volcano.
Volcanic eruptions are often rich in elements (particularly sulfur) which will eventually become incorporated into speleothem calcite. In addition to sulfur, the concentrations of molybdenum and bromine in stalagmites have recently been identified as important tracers of volcanic activity (Badertscher et al., 2014). To rationalize the involved correlations, knowledge about atomic-level structural and thermodynamic aspects of the impurity incorporation is needed. Calcite, the most common polymorph of calcium carbonate, forms the majority of speleothems but given certain conditions, aragonite is also stable (De Choudens-Sanchez and Gonzalez, 2009; Given and Wilkinson, 1985; Railsback et al., 1994). Although much rarer, vaterite can also form when the temperature within the cave is low enough, or if specific ion concentrations are prevalent in the aqueous phase forming the solid, but it is known to be unstable with respect to recrystallization to calcite and/or aragonite (Lacelle et al., 2009). Monohydrocalcite CaCO3·H2O, (MHC), is a rare hydrous phase of calcium carbonate which has been discovered in cave environments in a few rare cases (Fischbeck and Müller, 1971; Stoffers and Fischbeck, 1974). Ikaite CaCO3·6H2O is a hydrous phase of calcium carbonate commonly referred to as the “cold weather” phase. It is found in arctic environments, but is rare in caves. Field et al. (2018) reported the discovery of ikaite pseudomorphs in speleothems from the UK, which is the first evidence for ikaite being a constituent of speleothems. This rarity is partially because ikaite is known to be unstable with respect to recrystallisation at temperatures above 10 °C. Despite their rarity, the hydrated phases of calcium carbonate are still considered in our investigation, as they might still be relevant due to the dynamic nature of calcium carbonate phase transformations over long timescales.
The chemistry of sulfur incorporation in calcium carbonates has been studied in previous work, for example: the isotopic ratios of sulfur in carbonates (Balan et al., 2014), sulfur incorporation as sulfate ions (SO4)2− in the bulk of different CaCO3 polymorphs (Fernández-Díaz et al., 2010), its effect on the growth of calcite (Vavouraki et al., 2008) and the reactions of SO2 with the calcite surface (Böke et al., 1999; Malaga-Starzec et al., 2004). It is clear from these studies that carbonate substitution by sulfate is increasingly unfavourable in the order vaterite – calcite – aragonite. In contrast, very little is known about the incorporation of molybdenum in carbonate minerals. By analogy with sulfur, one can assume that incorporation will occur by molybdate substitution at the carbonate site, but since the (MoO4)2− anion is bigger than the (SO4)2− anion, the energetics of the substitution can be expected to be quite different.
In this paper we discuss the incorporation of molybdate ions (MoO4)2− (and (SO4)2−, for comparison) into CaCO3 polymorphs. We use quantum-mechanical simulations to elucidate the geometry and thermodynamics of incorporation of these anions in carbonate minerals: calcite, aragonite, vaterite, ikaite and monohydrocalcite (MHC).
Section snippets
Computational methods
Calcium carbonates and their interactions with other phases have been widely studied using computer simulation methods based on classical interatomic potentials (e.g. de Leeuw and Parker, 1998; Raiteri et al., 2010; Ruiz-Hernandez et al., 2010; Wang et al., 2011). However, because in this and following work we want to study a range of impurities for which currently there are no interatomic potentials available, and to gain in accuracy, we have performed our calculations using quantum-
Results and discussion
The calculated ion exchange energies are shown in Table 2. For sulfate/carbonate substitutions in the anhydrous calcium carbonate polymorphs, the ion exchange energies follow the order vaterite < calcite < aragonite, which is in agreement with previous work by (Arroyo-de Dompablo et al., 2015). This previous work did not consider the hydrated phases. Our calculations of the hydrated phases show that the sulfate/carbonate exchange energies for both MHC and ikaite are of similar values as for
Conclusions
We have presented a computer simulation study, based on density functional theory, of the incorporation of sulfate and molybdate impurities in calcium carbonates. The trend in incorporation stability of molybdate anions in anhydrous calcium carbonate phases is similar to the one obtained here, and in previous work, for sulfate anions (vaterite > calcite > aragonite). The 12c site of the P6522 structure of vaterite is the most stable substitution site for both sulfate and molybdate anions. We
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by the Natural Environment Research Council through the SCENARIO DTP (grant ref. NE/L002566/1), the Centre for Past Climate Change (CPCC) at the University of Reading; and ARCHER, the UK's national high-performance computing service, via the UK's HPC Materials Chemistry Consortium (EPSRC grant ref. EP/R029431).
References (49)
- et al.
Speleothems as sensitive recorders of volcanic eruptions – the Bronze Age Minoan eruption recorded in a stalagmite from Turkey
Earth Planet. Sci. Lett.
(2014) - et al.
First-principles modeling of sulfate incorporation and 34S/32S isotopic fractionation in different calcium carbonates
Chem. Geol.
(2014) - et al.
Effect of airborne particle on SO2–calcite reaction
Appl. Surf. Sci.
(1999) - et al.
Kinetic and thermodynamic factors controlling the distribution of SO32− and Na+ in calcites and selected aragonites
Geochim. Cosmochim. Acta
(1985) - et al.
Trace elements in speleothems as recorders of environmental change
Quat. Sci. Rev.
(2009) - et al.
The role of sulfate groups in controlling CaCO3 polymorphism
Geochim. Cosmochim. Acta
(2010) - et al.
Trace element variation in speleothem aragonite: potential for palaeoenvironmental reconstruction
Earth Planet. Sci. Lett.
(2001) - et al.
From soil to cave: transport of trace metals by natural organic matter in karst dripwaters
Chem. Geol.
(2012) - et al.
The sulphur isotopic composition of trace sulfates in Carboniferous brachiopods: implications for coeval seawater, correlation with other geochemical cycles and isotope stratigraphy
Chem. Geol.
(2001) - et al.
Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set
Comput. Mater. Sci.
(1996)
Tephrochronology and its application: a review
Quat. Geochronol.
Model study of initial adsorption of SO2 on calcite and dolomite
Appl. Surf. Sci.
Preliminary paleoclimate reconstruction based on a 12,500 year old speleothem from Vancouver Island, Canada: stable isotopes and U-Th disequilibrium dating
Quat. Sci. Rev.
Stable isotopes in tree rings
Quat. Sci. Rev.
Thermochemistry of strontium incorporation in aragonite from atomistic simulations
Geochim. Cosmochim. Acta
Expanding the utility of Uranium-series dating of speleothems for archaeological and palaeontological applications
J. Archaeol. Sci.
An Atomic Force Microscopy study of the growth of calcite in the presence of sodium sulfate
Chem. Geol.
Global distribution of centennial-scale records for Marine Isotope Stage (MIS) 3: a database
Quat. Sci. Rev.
Use of paleo-records in determining variability within the volcanism–climate system
Quat. Sci. Rev.
Central Europe temperature constrained by speleothem fluid inclusion water isotopes over the past 14,000 years
Sci. Adv.
Computational investigation of the influence of tetrahedral oxoanions (sulfate, selenate and chromate) on the stability of calcium carbonate polymorphs
RSC Adv.
Projector augmented-wave method
Phys. Rev. B
Calcite and aragonite precipitation under controlled instantaneous supersaturation: elucidating the role of CaCO3 saturation state and Mg/Ca ratio on calcium carbonate polymorphism
J. Sediment. Res.
Surface structure and morphology of calcium carbonate polymorphs calcite, aragonite, and vaterite: an atomistic approach
J. Phys. Chem. B
Cited by (9)
Glendonites throughout the Phanerozoic
2023, Earth-Science ReviewsPetrography and geochemistry of successions from northwest Bolivia
2023, Journal of South American Earth SciencesThe Mo- and U-isotope signatures in alternating shales and carbonate beds of rhythmites: A comparison and implications for redox conditions across the Cambrian-Ordovician boundary
2022, Chemical GeologyCitation Excerpt :In addition to redox conditions, the isotope fractionation between U6+ and U4+ can also be affected by organic matter burial rates, sedimentation rates, and basin reservoir effects (Andersen et al., 2014; Lau et al., 2020). Molybdenum exists in carbonates primarily as authigenic Mo phases formed during early diagenesis (e.g., Romaniello et al., 2016) and Mo accommodated on calcite surfaces (Midgley et al., 2020). Natural non-skeletal carbonates (e.g., ooid sands) and synthesized carbonates have been reported to exhibit negligible Mo isotope fractionations from ambient solutions (Voegelin et al., 2009; Chen et al., 2021).
Bromate incorporation in calcite and aragonite
2022, Geochimica et Cosmochimica ActaCitation Excerpt :Second, metastable bulk incorporation can still occur due to the complicated kinetics of mineral growth. For example, it is known that sulphate can partially incorporate in the bulk of calcite, even if the calculated solubility limits obtained for sulphate (Midgley et al., 2020) are very low (in fact much lower than the solubility limits obtained here for bromate). The higher solution limit of bromate compared to sulphate and molybdate is mainly due to the lower strain around the oxyanion impurity when the fourth, apical oxygen is not present, even if the trigonal pyramidal bromate ion is not a perfect fit to substitute the trigonal planar carbonate anion.
Co-Substituted BiFeO<inf>3</inf>: Electronic, Ferroelectric, and Thermodynamic Properties from First Principles
2023, Advanced Theory and SimulationsAnion elements incorporation into corals skeletons: Experimental approach for biomineralization and paleo-proxies
2023, Proceedings of the National Academy of Sciences of the United States of America