Geophysical and Geochemical Constraints on Magma Storage Depths Along the Cascade Arc: Knowns and Unknowns

Wieser, Penny E.; Kent, Adam J. R.; Till, Christy B.; Abers, Geoff A.

doi:10.1029/2023gc011025

Cited by 6 publications

(1 citation statement)

References 221 publications

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“…This is equivalent to a saturation pressure for a magma storage depth of ~4-6 km, broadly consistent with observed magma storage in the shallow crust [e.g. Huber et al 2019;Wieser et al 2023]. Unrealistically high-water contents (≪ 10 wt.% H 2 O) are required to get all calculated viscosities below the defined threshold, suggesting 10 6 Pa.s is not completely representative value that distinguishes eruptible from non-eruptible magmas, or there are other mechanisms that allow more crystal-rich magmas to erupt.…”

Section: Influences On Effective Viscosity and Magma Eruptibilitysupporting

confidence: 80%

An appraisal of the observed crystallinities of volcanic materials

Shamloo,

Kent

2024

Volcanica

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There is a broad consensus that magma eruptibility—the ability of magma stored in the subsurface to erupt onto Earth's surface—is strongly controlled by viscosity. Related to this, a critical parameter that controls viscosity is crystallinity. However, there is uncertainty in the crystallinities that distinguish eruptible from non-eruptible magmas, and whether highly crystalline magmas (>60 vol.%) could be erupted in some conditions. An underutilized but important source of information for understanding this relationship is the observed crystallinities in erupted volcanic materials, which by definition represent a set of eruptible magmas. Here we present a compilation of reported crystallinities for nearly 1000 volcanic samples of differing composition, tectonic setting, and eruption style, which provides valuable insight into the fundamental mechanisms which drive eruptions. Overall, the 95th percentile crystallinity value of our full dataset is 57 vol.%, and \>99 % of all non-dome samples have crystallinity ≤53 vol.%. This suggests that 50–60 vol.% crystallinity represents a fundamental limit for eruptibility for most volcanic rocks. Some dome samples are clear exceptions to this and are erupted with considerably higher crystallinities. There is also a significant correlation between crystallinity and whole rock SiO2 content as observed previously, but a shallow slope suggests whole rock and melt silica content have less impact on critical crystallinity for erupted magma than previously thought. Melt viscosity (as a function of SiO2, temperature, and H2O content) and crystallinity both play important roles on increasing effective viscosity, where melt viscosity plays a more important role at low crystal fractions, and crystallinity plays a more important role at crystallinities greater than ~40 vol.%.

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Section: Influences On Effective Viscosity and Magma Eruptibilitysupporting

confidence: 80%

An appraisal of the observed crystallinities of volcanic materials

Shamloo,

Kent

2024

Volcanica

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Deciphering magmatic processes from plagioclase, clinopyroxene and amphibole chemistry and textures: A case study of a basaltic lava flow in the Basque-Cantabrian Basin (Northern Spain)

Pesquera,

Gil-Crespo

2024

Miner Petrol

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This paper addresses the study of a pillow lava interbedded with Late Albian-Early Cenomanian sediments that crops out in Armintza (Bizkaia, Northern Spain). The lava flow is an alkaline basalt with abundant macrocrysts of clinopyroxene, kaersutite, Ca-rich plagioclase (50-86% An) and ilmenite, which display a variety of textures and complex zoning patterns indicative of open-system magmatic behaviour. Macrocryst cores are likely to be inherited antecrysts that underwent complex processes under deep pre-eruptive conditions (≈ 700-800 MPa). Microcrysts and macrocryst rims formed during magmatic ascent and emplacement at shallower levels (≈ 35 MPa). Hypothetical melts in equilibrium with clinopyroxenes and amphiboles have trace element compositions like metasomatic vein melts containing amphibole, and their patterns overlap with those of the Armintza pillow lava. This suggests a metasomatised lithospheric mantle with amphibole-rich veins as a potential source for the alkaline basaltic melt. It is even conceivable that the Armintza pillow lava and other alkaline volcanic manifestations of the Basque-Cantabrian Basin were part of the same magma plumbing system through which a series of time-limited eruptions of different batches of magma ascended from the lithospheric mantle to the upper crust during the Albian to the Santonian.

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