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High-silica magmas (≥68 weight % silicon dioxide) have produced some of the largest and most impactful volcanic eruptions in Earth’s history. Quartz-hosted melt inclusions can provide critical insights into the architecture, evolution, and eruption of silicic magmas; however, the reliability of mineral-hosted melt inclusion compositions has been questioned because of potential postentrapment modification of inclusions via diffusive exchange. We demonstrate that with careful sample selection, both naturally glassy and experimentally homogenized quartz-hosted melt inclusions can retain meaningful preeruptive signatures and provide useful insights into preeruptive magmatic conditions. We also show that hydrogen isotope measurements and detailed descriptions of melt inclusion geometries are particularly critical for identifying postentrapment diffusive exchange in melt inclusions, whether it is due to natural or experimental processes. Last, combining data from measurements of quartz-hosted melt inclusion hydrogen isotopes, trace elements, volatiles, and geometries, we fingerprint multiple discrete rhyolite magma reservoirs in the Highland Range volcanic sequence (NV, USA).
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Olivine-Hosted Melt Inclusions: A Microscopic Perspective on a Complex Magmatic World
Inclusions of basaltic melt trapped inside of olivine phenocrysts during igneous crystallization provide a rich, crystal-scale record of magmatic processes ranging from mantle melting to ascent, eruption, and quenching of magma during volcanic eruptions. Melt inclusions are particularly valuable for retaining information on volatiles such as H 2 O and CO 2 that are normally lost by vesiculation and degassing as magma ascends and erupts. However, the record preserved in melt inclusions can be variably obscured by postentrapment processes, and thus melt inclusion research requires careful evaluation of the effects of such processes. Here we review processes by which melt inclusions are trapped and modified after trapping, describe new opportunities for studying the rates of magmatic and volcanic processes over a range of timescales using the kinetics of post-trapping processes, and describe recent developments in the use of volatile contents of melt inclusions to improve our understanding of how volcanoes work. ▪ Inclusions of silicate melt (magma) trapped inside of crystals formed by magma crystallization provide a rich, detailed record of what happens beneath volcanoes. ▪ These inclusions record information ranging from how magma forms deep inside Earth to its final hours as it ascends to the surface and erupts. ▪ The melt inclusion record, however, is complex and hazy because of many processes that modify the inclusions after they become trapped in crystals. ▪ Melt inclusions provide a primary archive of dissolved gases in magma, which are the key ingredients that make volcanoes erupt explosively.
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- Award ID(s):
- 1644013
- PAR ID:
- 10312769
- Date Published:
- Journal Name:
- Annual Review of Earth and Planetary Sciences
- Volume:
- 49
- Issue:
- 1
- ISSN:
- 0084-6597
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1146/annurev-earth-082420-060506
