Pore Structure Determines Pathways of Rock Alteration

October 11, 2021
Pore Structure Determines Pathways of Rock Alteration
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) data of an interface between two intermediate phases in CM reacted for 317 days. Inset: relative pore size distribution in CM for different number of days of MgCl2 treatment, calculated from SANS and USANS beamline data.

Scientific Achievement

Replacement of Ca by Mg in highly porous limestone is found to be relatively homogeneous, while in low-porosity limestone it proceeds via distinct intermediate phase zones with sharp boundaries between calcite, dolomite, and magnesite.

Significance and Impact

Models to predict mineral reactions are important for geothermal energy production, carbon sequestration, and gas production, and this work shows the importance of considering porosity and grain boundary transport.

Research Details

  • Low porosity Carthage Marble (CM) and high porosity Texas Cream (TC) limestones were treated with saturated aqueous MgCl2 in sealed containers at 200 °C from 32 to 317 days.
  • This comprehensive study identifies previously unknown relations between parent rock microstructure, mechanisms of element replacement and the evolution of porosity.

“Influence of Microstructure on Replacement and Porosity Generation During Experimental Dolomitization of Limestones,”
Juliane Weber, Michael Cheshire, Markus Bleuel, David Mildner. Yao-Jen Chang, Anton Ievlev, Ken Littrell, Jan Ilavsky, Andrew Stack, and Lawrence Anovitz,
Geochimica et Cosmochimica Acta 303, 137-158 (2021).
DOI: https://doi.org/10.1016/j.gca.2021.03.029