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Incursion of meteoric waters into the ductile regime in an active orogen

Menzies, C.D.; Teagle, D.A.H.; Craw, D.; Cox, S.C.; Boyce, A.J.; Barrie, C.D.; Roberts, S.

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Authors

D.A.H. Teagle

D. Craw

S.C. Cox

A.J. Boyce

C.D. Barrie

S. Roberts



Abstract

Rapid tectonic uplift on the Alpine Fault, New Zealand, elevates topography, regional geothermal gradients, and the depth to the brittle ductile transition, and drives fluid flow that influences deformation and mineralisation within the orogen. Oxygen and hydrogen stable isotopes, fluid inclusion and Fourier Transform Infrared (FT-IR) analyses of quartz from veins which formed at a wide range of depths, temperatures and deformation regimes identify fluid sources and the depth of penetration of meteoric waters. Most veins formed under brittle conditions and with isotope signatures (δ18OH2O = −9.0 to +8.7‰VSMOW and ‰ ) indicative of progressively rock-equilibrated meteoric waters. Two generations of quartz veins that post-date mylonitic foliation but endured further ductile deformation, and hence formation below the brittle to ductile transition zone ( depth), preserve included hydrothermal fluids with values between −84 and ‰ , indicating formation from meteoric waters. FT-IR analyses of these veins show no evidence of structural hydrogen release, precluding this as a source of low values. In contrast, the oxygen isotopic signal of these fluids has almost completely equilibrated with host rocks (δ18OH2O = +2.3 to +8.7‰). These data show that meteoric waters dominate the fluid phase in the rocks, and there is no stable isotopic requirement for the presence of metamorphic fluids during the precipitation of ductilely deformed quartz veins. This requires the penetration during orogenesis of meteoric waters into and possibly below the brittle to ductile transition zone.

Citation

Menzies, C., Teagle, D., Craw, D., Cox, S., Boyce, A., Barrie, C., & Roberts, S. (2014). Incursion of meteoric waters into the ductile regime in an active orogen. Earth and Planetary Science Letters, 399, 1-13. https://doi.org/10.1016/j.epsl.2014.04.046

Journal Article Type Article
Acceptance Date Apr 29, 2014
Online Publication Date May 20, 2014
Publication Date Aug 1, 2014
Deposit Date Oct 2, 2019
Publicly Available Date Mar 28, 2024
Journal Earth and Planetary Science Letters
Print ISSN 0012-821X
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 399
Pages 1-13
DOI https://doi.org/10.1016/j.epsl.2014.04.046

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