Calcite sealing in a fractured geothermal reservoir: Insights from combined EBSD and chemistry mapping

McNamara, David D ORCID: 0000-0001-9789-2436, Lister, Aaron and Prior, Dave J (2016) Calcite sealing in a fractured geothermal reservoir: Insights from combined EBSD and chemistry mapping. JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, 323. pp. 38-52.

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Abstract

Fractures play an important role as fluid flow pathways in geothermal resources hosted in indurated greywacke basement of the Taupo Volcanic Zone, New Zealand, including the Kawerau Geothermal Field. Over time, the permeability of such geothermal reservoirs can be degraded by fracture sealing as minerals deposit out of transported geothermal fluids. Calcite is one such fracture sealing mineral. This study, for the first time, utilises combined data from electron backscatter diffraction and chemical mapping to characterise calcite vein fill morphologies, and gain insight into the mechanisms of calcite fracture sealing in the Kawerau Geothermal Field. Two calcite sealing mechanisms are identified 1) asymmetrical syntaxial growth of calcite, inferred by the presence of single, twinned, calcite crystals spanning the entire fracture width, and 2) 3D, interlocking growth of bladed vein calcite into free space as determined from chemical and crystallographic orientation mapping. This study also identifies other potential uses of combined EBSD and chemical mapping to understand geothermal field evolution including, potentially informing on levels of fluid supersaturation from the study of calcite lattice distortion, and providing information on a reservoir's history of stress, strain, and deformation through investigation of calcite crystal deformation and twinning patterns.

Item Type:	Article
Uncontrolled Keywords:	Calcite, Fracture sealing, Kawerau geothermal field, Reservoir, Permeability
Depositing User:	Symplectic Admin
Date Deposited:	16 Aug 2019 07:32
Last Modified:	19 Jan 2023 00:29
DOI:	10.1016/j.jvolgeores.2016.04.042
Open Access URL:	https://aran.library.nuigalway.ie/bitstream/handle...
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3051909