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Geochemical and microstructural evidence for interseismic changes in fault zone permeability and strength, Alpine Fault, New Zealand

Boulton, C.; Menzies, C.D; Toy, V.G.; Townend, J.; Sutherland, R.

Geochemical and microstructural evidence for interseismic changes in fault zone permeability and strength, Alpine Fault, New Zealand Thumbnail


Authors

C. Boulton

V.G. Toy

J. Townend

R. Sutherland



Abstract

Oblique dextral motion on the central Alpine Fault in the last circa 5 Ma has exhumed garnetoligoclase 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 (T300–4008C, 6–10 km depth) and at shallow depths (T520–1508C, 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.

Citation

Boulton, C., Menzies, C., Toy, V., Townend, J., & Sutherland, R. (2017). Geochemical and microstructural evidence for interseismic changes in fault zone permeability and strength, Alpine Fault, New Zealand. Geochemistry, Geophysics, Geosystems, 18(1), 238-265. https://doi.org/10.1002/2016gc006588

Journal Article Type Article
Acceptance Date Dec 12, 2016
Online Publication Date Jan 25, 2017
Publication Date Jan 31, 2017
Deposit Date Oct 2, 2019
Publicly Available Date Mar 28, 2024
Journal Geochemistry, Geophysics, Geosystems
Publisher American Geophysical Union
Peer Reviewed Peer Reviewed
Volume 18
Issue 1
Pages 238-265
DOI https://doi.org/10.1002/2016gc006588

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Copyright Statement
Boulton, C., Menzies, C.D, Toy, V.G., Townend, J. & Sutherland, R. (2017). Geochemical and microstructural evidence for interseismic changes in fault zone permeability and strength, Alpine Fault, New Zealand. Geochemistry, Geophysics, Geosystems 18(1): 238-265. 10.1002/2016GC006588. To view the published open abstract, go to https://doi.org/ and enter the DOI.




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