196-3 Coupled Chemical-Mechanical Processes in Experimentally Deformed Calcite Grains, Nitratine Analog Material, and Naturally Deformed Fault Rocks

Session: Strain and Displacement: Patterns, Gradients, Partitioning, and Reconstructions (Posters)

Poster Booth No.: 203

Presenting Author:

Matty Mookerjee

Authors:

Mookerjee, Matty¹, Lisabeth, Harry², Olivarez, Atzi³, Ortega-Vidrio, Yajaira⁴, Perez Villanueva, Abigail⁵, Witt, Kevin⁶

(1) Geology Department, Sonoma State University, Rohnert Park, CA, USA, (2) Earth and Environmental Sciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA, USA, (3) Geology, Sonoma State University, Rohnert Park, CA, USA, (4) Geology, Sonoma State University, Rohnert Park, CA, USA, (5) Geology, Sonoma State University, Rohnert Park, CA, USA, (6) Geology, Sonoma State University, Rohnert Park, CA, USA,

Abstract:

Calcite-rich lithologies—including limestone, chalk, and marble—represent an ideal system for investigating the coupled mechanical and chemical processes that govern deformation within sedimentary basins and fault zones. Calcite’s high chemical reactivity and its capacity for crystal plasticity under a range of temperature, pressure, and stress conditions make it a model mineral for exploring the interplay of brittle, ductile, and fluid-assisted deformation mechanisms. This study aims to disentangle these complex interactions by integrating controlled laboratory deformation experiments with detailed microstructural analyses of naturally deformed fault-related samples.

We employ both Electron Backscatter Diffraction (EBSD) and Laue X-ray microdiffraction to map grain-scale deformation, residual strain, and crystallographic misorientation. Complementary experiments using nitratine, a structural analog to calcite, are used to simulate higher-temperature and lower strain-rate conditions. These experimental results are compared with naturally deformed calcite samples from a range of tectonic settings.

Preliminary findings demonstrate a strong influence of fluid chemistry on deformation mechanisms. Manganese-doped experiments show a notable increase in dislocation creep, as evidenced by (1) elevated concentrations of low-angle neighbors in the disorientation angle distribution histogram, (2) qualitative assessments of grain microstructures, and (3) the development of a Crystallographic Vorticity Axis (CVA) fabric. Additionally, the manganese-doped sample have a marked decrease in twin density with respect to our control sample, whereas the non-doped samples exhibited a significant increase in twin density.

New analyses using geometrically necessary dislocation (GND) density maps further illuminate the mechanical behavior of these samples. These maps enable visualization and quantification of force chain networks—connected zones of elevated dislocation density—that reveal preferential pathways of stress transmission and the onset of strain localization.

By bridging laboratory and natural observations and applying advanced microstructural techniques, this work provides new insights into fault mechanics and basin evolution. These findings have important implications for understanding subsurface deformation, improving models of seismic hazard, and informing strategies for sustainable resource extraction.

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

doi: 10.1130/abs/2025AM-9005

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.