Crystal growth rate has not been sufficiently explored to understand element partitioning between calcite and seawater solutions. We investigated the uptake of Li, B, Mg, Sr, and Ba by Mg-bearing calcite slowly grown on a calcite cleavage fragment. Experiments were conducted by elevating the alkalinity of an artificial seawater solution. Growth rates were evaluated by addition of lanthanum spike. At the end of each experiment, cleavage fragments were extracted and examined with micro-Raman spectroscopy, scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) using depth profiling technique. Distribution of Li, B, Mg, Sr, and Ba in calcite overgrowth as well as partition coefficients of those elements were evaluated.

This study is focused on the mineralogical, chemical, and isotopic characterization of pyrites from the rocks of the Bazhenov Formation (Upper Jurassic–Lower Cretaceous organic-rich shales, Western Siberia, Russia). Scanning electron microscopy (SEM) revealed pyrites of different morphologies: small and large framboids, small crystals, and large euhedral crystals; all morphotypes were usually combined into aggregates. Isotope ratio mass spectrometry (IRMS) and secondary ion mass spectrometry (SIMS) showed that small framboids and microcrystalline pyrite are isotopically light, with δ³⁴SCDT varying from −55 to −20‰. Large framboids and euhedral crystals of pyrite are isotopically heavy with δ³⁴SCDT up to +26‰. Both morphology and δ³⁴S were suggested to be controlled by the redox conditions and sedimentation regime. The abundance of small framboids suggests that pyrite sedimentation occurred under anoxic conditions; the presence of the large framboids and euhedral crystals of pyrite suggest the accumulation of sediments occurred at suboxic conditions, possibly in the presence of oxygen.

Experiments on the incorporation of trace elements into calcite were performed, and rare earth elements (REE) were used to mark the growth zones of individual crystals. Experiments were conducted at different pH (7.7 to 8.8) and temperatures (2 °C to 24.6 °C) in NH₄Cl + CaCl₂ solutions, where REE were rapidly consumed by growing calcite. LA-ICP-MS line-scans yielded the distribution of (REE/Ca)_calcite within individual crystals in a manner consistent with the addition of REE into fluid. A sharp decrease of (REE/Ca)_calcite toward the crystal edge suggests the fast depletion of (REE/Ca)_fluid due to strong REE consumption by growing calcite. An attempt was made to estimate the lower limit of the partition coefficients between calcite and fluid using selected REE/Ca data within individual calcite crystals and the amount of REE added into fluid.

Transformation of aragonite, a mineral phase metastable at Earth’s surface, to calcite widely occurs in both sedimentary and metamorphic systems with the presence of an aqueous phase. The transformation process can affect geochemical signatures of aragonite (a protolith). This study focused on quantification of the retention of Mg/Ca and Sr/Ca ratios, and δ¹⁸O during the transformation process as well as evaluation of the transformation rate. To investigate the effect of transformation from aragonite to calcite on elemental and stable isotope ratios, we conducted a series of experiments in NaCl solutions at temperatures between 120 and 184 °C. Two additional experiments at 250 °C were conducted to estimate the transformation rate of aragonite to calcite. Protolith materials consist of (1) synthetic (Mg; Sr-bearing or non-Mg; Sr bearing) needle-shaped microcrystals of aragonite (100 µm in size) of natural aragonite. X-ray diffraction (XRD) showed that microcrystals successfully transformed to calcite within 30 h and scanning electron microscopy (SEM) yielded a change in the crystal size to >10 µm in rhombohedral shape. Electron backscatter diffraction (EBSD) of the larger aragonite chips showed that transformation to randomly oriented calcite occurred at the rims and along the cracks while the core retained an aragonite crystal structure. Isotope-ratio mass spectrometry (IRMS) analyses showed that calcite δ¹⁸O was controlled by temperature and δ¹⁸O of the solution. The obtained calibration curve of isotope fractionation factor versus temperature is consistent with other studies. Inductively coupled plasma optical emission spectroscopy (ICP-OES) analyses showed that calcite partially or completely retained Mg/Ca and Sr/Ca ratios through the transformation.

This study aims to evaluate relationships between elemental signatures in calcite and the crystallographic orientation of its planes. The ability of calcite (a widespread calcium carbonate mineral) to entrap various trace and minor elements in its structure is the foundation of multiple methods (also called proxies) to reconstruct paleoenvironment conditions (e.g., temperature, pH, and marine chemistry). Although several element-to-calcium ratios (E/Ca) are routinely measured in marine carbonates and are widely used in paleoclimate studies, some of the controls on the incorporation of these elements are still unclear. Here, we examine the effect of crystallography on (E/Ca)_calcite by growing thin layers of calcite on differently oriented Iceland Spar substrates immersed in modified seawater solution. Newly grown calcite layers were examined with Laser Ablation Inductivity–Coupled Plasma Mass Spectrometry (LA-ICP-MS), Backscattered Electron Imaging (BSE), and Energy Dispersive X-ray Spectroscopy (EDS). We propose that the crystallographic orientation might slightly influence the incorporation of lithium (Li), sodium (Na), magnesium (Mg), sulfur (S), and barium (Ba) into the studied calcite faces and have no impact on the incorporation of boron (B), potassium (K), and strontium (Sr) at least under the conditions of our experiment.