192 Twenty-Seven Years of Advances in Understanding Salt-Sediment Interaction: A Legacy of Katherine A. Giles (Posters)

This session seeks contributions that highlight the interconnections between coevolving salt bodies and depositional systems in continental, shallow marine and deep marine settings. Field, geobiological, geophysical, and geochemical, as well as theoretical, physical and numerical modeling studies are encouraged.

Tuesday, 21 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Using PHAST Reaction-Transport Modeling to Study Near-Diapir Diagenesis.

Paper number: 192-3
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Sediment diagenesis at the margin of salt diapirs is a critical factor controlling permeability and porosity, and thus fluid and heat transport at salt bodies. Dissolution, replacement, and cementation are controlled by complex interactions between fluid chemistry, temperature, and pressure. Theoretically, such conditions can be reconstructed using Reaction-Transport Modeling (RTM), which simultaneously simulates solute transport and geochemical reactions. However, most RTMs are developed to address specific case studies, often requiring custom code or proprietary software. This presents limitations such as low computational efficiency, limited portability across platforms, and poor documentation, ultimately making these models difficult for other researchers to reuse or adapt. PHAST, a modeling tool that integrates PHREEQC, a geochemical modeling software with HST3D, a solute transport model, is a free and open-source program developed by the USGS. It is designed to simulate three-dimensional groundwater flow, solute transport, and multicomponent geochemical reactions. PHAST offers a user-friendly interface, accessible tutorials, and multithreaded processing, which improves computational performance. These advantages raise the question of whether PHAST can be applied more broadly, for instance, to simulate the geochemical processes involved in ore deposit formation or hydrocarbon migration. This study aims to adapt PHAST to predict diagenetic processes and their consequences for fluid flow at diapir margins. As a test, we apply this tool to the development of zebra limestone, which is characterized by alternating millimeter- to centimeter-scale bands of light and dark calcite crystals, features that have been observed at the Gypsum Valley salt diapir in the Paradox Basin, Colorado. Zebra rock formation is often associated with carbonate-hosted lead-zinc Mississippi Valley Type (MVT) ore deposits and hydrothermal dolomite-hosted hydrocarbon reservoirs.

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

doi: 10.1130/abs/2025AM-411943

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