التفاصيل البيبلوغرافية
| العنوان: |
Porosity-permeability relationships in crystal-rich basalts from Plinian eruptions. |
| المؤلفون: |
Moitra, Pranabendu, Houghton, Bruce F. |
| المصدر: |
Bulletin of Volcanology; Nov2021, Vol. 83 Issue 11, p1-11, 11p |
| مصطلحات موضوعية: |
EXPLOSIVE volcanic eruptions, BASALT, POROSITY |
| مصطلحات جغرافية: |
ETNA, Mount (Italy), ITALY, NEW Zealand |
| مستخلص: |
Magma permeability allows release of exsolved and pressurized volatiles during magma ascent, potentially modulating explosive volcanic eruptions. While porosity-permeability relationships in the clasts from silicic Plinian eruptions have received considerable interests in recent years, knowledge on magma permeability during Plinian eruptions of basaltic magma is lacking. In this study, we investigate the porosity-permeability relationships in pyroclasts from the well-studied Plinian eruptions of basaltic magma at Mt. Tarawera, New Zealand (1886 CE) and Mt. Etna, Italy (122 BCE). We find that Darcian permeabilities in the studied clasts range between approximately 10−12 m2 and 10−10 m2 over a range of total porosity between 48 and 82%. The vesicles are well connected with values of 45–82% for connected porosity. Pyroclasts from the studied Plinian eruptions contain abundant microlites (∼ 60–90 vol. %) in the matrix surrounding vesicles. At a given total porosity, the measured permeabilities are somewhat higher than that measured in the crystal-poor lapilli from less explosive basaltic eruptions, and about 1–2 orders of magnitude higher than that in silicic Plinian clasts. The estimated percolation threshold is ∼34% for the two basaltic Plinian eruptions. Using modeling of ascent of multiphase magma through volcanic conduits during eruptions, we find that the relative timing of crystallization and the onset of percolation might have played a key role in the development of the measured porosity-permeability relationships. Using scaling analysis, we further show that rheological stiffening of basaltic melt due to a high crystal content just prior to magma fragmentation should have stabilized the vesicle networks, preserving textures reflecting the eruptive conditions with insignificant post-eruptive modification. [ABSTRACT FROM AUTHOR] |
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| قاعدة البيانات: |
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