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123249 - Permeability during magma expansion and compaction.pdf (4.72 MB)

Permeability during magma expansion and compaction

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posted on 2023-05-19, 14:29 authored by Gonnermann, HM, Giachetti, T, Fliedner, C, Nguyen, CT, Houghton, BF, Crozier, JA, Rebecca CareyRebecca Carey
Plinian lapilli from the 1060 Common Era Glass Mountain rhyolitic eruption of Medicine Lake Volcano, California, were collected and analyzed for vesicularity and permeability. A subset of the samples were deformed at a temperature of 975°, under shear and normal stress, and postdeformation porosities and permeabilities were measured. Almost all undeformed samples fall within a narrow range of vesicularity (0.7–0.9), encompassing permeabilities between approximately 10−15 m2 and 10−10 m2. A percolation threshold of approximately 0.7 is required to fit the data by a power law, whereas a percolation threshold of approximately 0.5 is estimated by fitting connected and total vesicularity using percolation modeling. The Glass Mountain samples completely overlap with a range of explosively erupted silicic samples, and it remains unclear whether the erupting magmas became permeable at porosities of approximately 0.7 or at lower values. Sample deformation resulted in compaction and vesicle connectivity either increased or decreased. At small strains permeability of some samples increased, but at higher strains permeability decreased. Samples remain permeable down to vesicularities of less than 0.2, consistent with a potential hysteresis in permeability-porosity between expansion (vesiculation) and compaction (outgassing). We attribute this to retention of vesicle interconnectivity, albeit at reduced vesicle size, as well as bubble coalescence during shear deformation. We provide an equation that approximates the change in permeability during compaction. Based on a comparison with data from effusively erupted silicic samples, we propose that this equation can be used to model the change in permeability during compaction of effusively erupting magmas.

Funding

Australian Research Council

History

Publication title

Journal of Geophysical Research: Solid Earth

Volume

122

Issue

12

Pagination

9825-9848

ISSN

2169-9313

Department/School

School of Natural Sciences

Publisher

Wiley-Blackwell Publishing Inc.

Place of publication

United States

Rights statement

Published 2017 American Geophysical Union. Not subject to U.S. copyright.

Repository Status

  • Open

Socio-economic Objectives

Expanding knowledge in the earth sciences

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