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The evolution of pore connectivity in volcanic rocks

Colombier, Mathieu; Wadsworth, Fabian B.; Gurioli, Lucia; Scheu, Bettina; Kueppers, Ulrich; Di Muro, Andrea; Dingwell, Donald B.

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Authors

Mathieu Colombier

Lucia Gurioli

Bettina Scheu

Ulrich Kueppers

Andrea Di Muro

Donald B. Dingwell



Abstract

Pore connectivity is a measure of the fraction of pore space (vesicles, voids or cracks) in a material that is interconnected on the system length scale. Pore connectivity is fundamentally related to permeability, which has been shown to control magma outgassing and the explosive potential of magma during ascent in the shallowest part of the crust. Here, we compile a database of connectivity and porosity from published sources and supplement this with additional measurements, using natural volcanic rocks produced in a broad range of eruptive styles and with a range of bulk composition. The database comprises 2715 pairs of connectivity C and porosity φ values for rocks from 35 volcanoes as well as 116 products of experimental work. For 535 volcanic rock samples, the permeability k was also measured. Data from experimental studies constrain the general features of the relationship between C and φassociated with both vesiculation and densification processes, which can then be used to interpret natural data. To a first order, we show that a suite of rocks originating from effusive eruptive behaviour can be distinguished from rocks originating from explosive eruptive behaviour using C and φ. We observe that on this basis, a particularly clear distinction can be made between scoria formed in fire-fountains and that formed in Strombolian activity. With increasing φ, the onset of connectivity occurs at the percolation threshold φcwhich in turn can be hugely variable. We demonstrate that C is an excellent metric for constraining φcin suites of porous rocks formed in a common process and discuss the range of φcvalues recorded in volcanic rocks. The percolation threshold is key to understanding the onset of permeability, outgassing and compaction in shallow magmas. We show that this threshold is dramatically different in rocks formed during densification processes than in rocks formed in vesiculating processes and propose that this value is the biggest factor in controlling the evolution of permeability at porosities above φc.

Citation

Colombier, M., Wadsworth, F. B., Gurioli, L., Scheu, B., Kueppers, U., Di Muro, A., & Dingwell, D. B. (2017). The evolution of pore connectivity in volcanic rocks. Earth and Planetary Science Letters, 462, 99-109. https://doi.org/10.1016/j.epsl.2017.01.011

Journal Article Type Article
Acceptance Date Jan 15, 2017
Online Publication Date Jan 30, 2017
Publication Date Mar 15, 2017
Deposit Date Mar 20, 2018
Publicly Available Date Mar 29, 2024
Journal Earth and Planetary Science Letters
Print ISSN 0012-821X
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 462
Pages 99-109
DOI https://doi.org/10.1016/j.epsl.2017.01.011

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