Mafic glass compositions: a record of magma storage conditions, mixing and ascent

Cashman, Katharine V. and Edmonds, Marie (2019) Mafic glass compositions: a record of magma storage conditions, mixing and ascent. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 377 (2139). p. 20180004. ISSN 1364-503X DOI https://doi.org/10.1098/rsta.2018.0004

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Abstract

The trans-crustal magma system paradigm is forcing us to re-think processes responsible for magma evolution and eruption. A key concept in petrology is the liquid line of descent (LLD), which relates a series of liquids derived from a single parent, and therefore tracks the inverse of the crystallization path. It is common practice to attribute multiple magma compositions, and/or multiple melt compositions (from melt inclusions and matrix glass), to a single LLD. However, growing evidence for rapid, and often syn-eruptive, assembly of multiple magma components (crystals and melts) from different parts of a magmatic system suggests that erupted magma and melt compositions will not necessarily represent a single LLD, but instead may reflect the multiple paths in pressure–temperature space. Here, we use examples from mafic magmatic systems in both ocean island and arc settings to illustrate the range of melt compositions present in erupted samples, and to explore how they are generated, and how they interact. We highlight processes that may be deduced from mafic melt compositions, including the mixing of heterogeneous primitive liquids from the mantle, pre-eruptive magma storage at a range of crustal and sub-Moho depths, and syn-eruptive mixing of melts generated from these storage regions. The relative dominance of these signatures in the glasses depends largely on the water content of the melts. We conclude that preserved melt compositions provide information that is complementary to that recorded by the volatile contents of crystal-hosted melt inclusions and coexisting mineral compositions, which together can be used to address questions about both the pre- and syn-eruptive state of volcanic systems.

Item Type:	Article
Additional Information:	© The Authors One contribution of 15 to a Theo Murphy meeting issue ‘Magma reservoir architecture and dynamics’.
Uncontrolled Keywords:	2018AREP; IA74
Subjects:	05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions:	05 - Petrology - Igneous, Metamorphic and Volcanic Studies 07 - Gold Open Access
Journal or Publication Title:	Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Volume:	377
Page Range:	p. 20180004
Identification Number:	https://doi.org/10.1098/rsta.2018.0004
Depositing User:	Sarah Humbert
Date Deposited:	07 Jan 2019 11:26
Last Modified:	07 Jan 2019 12:36
URI:	http://eprints.esc.cam.ac.uk/id/eprint/4379

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