Program > Browse abstracts by speaker > Prasad Anulekha

The microscopic structure of water remains a subject of vigorous investigation, with accumulating evidence for the coexistence of low‐density water (LDW) and high‐density water (HDW) forms separated by a liquid–liquid phase transition (LLPT) occurring between 0.2 and 0.4 GPa.

This study aims to better understand the LLPT in water attributed to the alterations in hydrogen bonding. We examine, using the DAC, how these changes, coupled with high salt concentrations, affect the solubility of quartz and anhydrite—minerals that play essential roles in geochemical processes.

During subduction and slab dehydration, vast amounts of H₂O are released, significantly influencing the properties of subduction zone fluids. Water's polar nature and strong tendency to dissociate make it an exceptionally effective solvent relative to other volatiles, with these fluids exhibiting characteristics that are intermediate between hydrous silicate melts and pure water. These supercritical fluids control mass transfer into the mantle wedge and drive chemical interactions at depth.

Quartz shows a dissolution–precipitation behavior that limits the transport of silica in hydrothermal systems. Our results confirm that under low-temperature, high-pressure conditions, the presence of salt induces a salting-out effect that reduces silica solubility. Conversely, NaCl dramatically enhances the solubility of anhydrite (CaSO₄), increasing it by up to 200-fold compared to pure water conditions.

These observations provide valuable benchmarks for refining water models under extreme conditions and improving our understanding of hydrothermal fluid behavior in geological settings, with implications for magma generation and ore deposit formation. Overall, this study advances our comprehension of aqueous geochemistry by elucidating the complex interplay between water structure, salt concentration, and mineral solubility under extreme thermodynamic conditions. These findings not only refine theoretical models but also provide practical insights for predicting fluid behavior in subduction zones, contributing to our understanding of deep Earth processes.