149-8 High alkalinity fluids produced by hydrolysis and phase separation of H2O-salt fluids: an experimental approach

Session: Research to Accelerate Recovery of Critical Minerals from Primary and Secondary Resources (Posters)

Poster Booth No.: 276

Presenting Author:

Brady Fox

Authors:

Fox, Brady¹, Cano, Néstor Alfredo², Camprubi, Antoni³, Steele-Macinnis, Matthew⁴, Lamadrid, Hector M.⁵

(1) School of Geosciences, University of Oklahoma, Norman, Oklahoma, USA, (2) Instituto de Geologia, Universidad Nacional Autónoma de México, Mexico City, DF, Mexico, (3) UNAM, Instituto de Geologia, Mexico City, DF, Mexico, (4) University of Alberta, Edmonton, AB, Canada, (5) School of Geosciences, University of Oklahoma, Norman, OK, USA,

Abstract:

Fluids play an important role in nearly every geological process. As fluids and magmas ascend, they undergo multiple events of exsolution and phase separation (boiling) that are responsible for the fractionation of all the major components of the fluids (H₂O, CO₂, salts, etc.), becoming one of the major controls on the movement and concentration of critical metals in the Earth’s crust. The P-T range where phase separation occurs (> 300 °C) encompasses a wide range of geologic processes, including geothermal systems, oceanic hydrothermal venting, magmatic to hydrothermal ore deposits, volcanic and sub-volcanic hydrothermal systems, and contact metamorphism. Despite the importance of boiling, certain aspects of the accompanying chemical fractionation of aqueous-salt fluids, such as hydrolysis, remain poorly understood. Hydrolysis of H₂O-salt fluids follows the general reaction H₂O \+ MCl = HCl_(vapor) + MOH_(liquid) (where M represents the cations in the salt component). This fractionation generates a vapor phase that, as boiling intensifies, becomes increasingly acidic, while the liquid phase becomes progressively more alkaline. Most of the attention on hydrolysis has focused on the acidic vapors, yet little attention has been given to the alkaline-rich liquid component, outside of brief mentions in experimental studies. In this study, we focus on understanding the geochemical and mineralogical evidence left by these alkaline-rich fluids during boiling by trapping synthetic fluid inclusions in different H2O-salt systems. To prevent acid-alkaline neutralization, experiments will utilize double platinum capsules in vertical, cold-sealed vessels. The results of the study will be compared with boiling assemblages from different geologic settings in nature.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10580

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