Geochemical and microstructural evidence for interseismic changes in fault zone permeability and strength, <scp>A</scp>lpine <scp>F</scp>ault, <scp>N</scp>ew <scp>Z</scp>ealand

Boulton, Carolyn ORCID: 0000-0003-0597-6152, Menzies, Catriona D, Toy, Virginia G ORCID: 0000-0002-7621-2064, Townend, John ORCID: 0000-0002-7017-620X and Sutherland, Rupert (2017) Geochemical and microstructural evidence for interseismic changes in fault zone permeability and strength, <scp>A</scp>lpine <scp>F</scp>ault, <scp>N</scp>ew <scp>Z</scp>ealand. Geochemistry, Geophysics, Geosystems, 18 (1). pp. 238-265.

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Official URL: http://dx.doi.org/10.1002/2016gc006588

Abstract

<jats:title>Abstract</jats:title><jats:p>Oblique dextral motion on the central Alpine Fault in the last circa 5 Ma has exhumed garnet‐oligoclase facies mylonitic fault rocks from ∼35 km depth. During exhumation, deformation, accompanied by fluid infiltration, has generated complex lithological variations in fault‐related rocks retrieved during Deep Fault Drilling Project (DFDP‐1) drilling at Gaunt Creek, South Island, New Zealand. Lithological, geochemical, and mineralogical results reveal that the fault comprises a core of highly comminuted cataclasites and fault gouges bounded by a damage zone containing cataclasites, protocataclasites, and fractured mylonites. The fault core‐alteration zone extends ∼20–30 m from the principal slip zone (PSZ) and is characterized by alteration of primary phases to phyllosilicate minerals. Alteration associated with distinct mineral phases occurred proximal the brittle‐to‐plastic transition (T ≤ 300–400°C, 6–10 km depth) and at shallow depths (T = 20–150°C, 0–3 km depth). Within the fault core‐alteration zone, fractures have been sealed by precipitation of calcite and phyllosilicates. This sealing has decreased fault normal permeability and increased rock mass competency, potentially promoting interseismic strain buildup.</jats:p>

Item Type:	Article
Depositing User:	Symplectic Admin
Date Deposited:	13 Feb 2017 08:12
Last Modified:	18 Sep 2023 08:11
DOI:	10.1002/2016gc006588
Related URLs:	Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3005771