Magma chambers versus mush zones: constraining the architecture of sub-volcanic plumbing systems from microstructural analysis of crystalline enclaves.
Philosophical transactions. Series A, Mathematical, physical, and engineering sciences
The Royal Society
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Holness, M., Stock, M., & Geist, D. (2019). Magma chambers versus mush zones: constraining the architecture of sub-volcanic plumbing systems from microstructural analysis of crystalline enclaves.. Philosophical transactions. Series A, Mathematical, physical, and engineering sciences, 377 (2139), 20180006. https://doi.org/10.1098/rsta.2018.0006
There are clear microstructural differences between mafic plutonic rocks that formed in a dynamic liquid-rich environment, in which crystals can be moved and re-arranged by magmatic currents, and those in which crystal nucleation and growth are essentially in situ and static. Crystalline enclaves, derived from deep crustal mushy zones and erupted in many volcanic settings, afford a unique opportunity to use the understanding of microstructural development, established from the study of intrusive plutons, to place constraints on the architecture of sub-volcanic systems. Here, we review the relevant microstructural litterature, before applying these techniques to interrogate the crystallisation environments of enclaves from the Kameni Islands of Santorini, and Rábida Volcano in the Galápagos. Crystals in samples of deep-sourced material from both case studies preserve evidence of at least some time spent in a liquid-rich environment. The Kameni enclaves appear to record an early stage of crystallisation during which crystals were free to move, with the bulk of crystallisation occurring in a static, mushy environment. In contrast, the Rábida enclaves were sourced from an environment in which hydrodynamic sorting and re-arrangement by magmatic currents were common, consistent with a liquid-rich magma chamber. While presently-active volcanoes are thought to be underlain by extensive regions rich in crystal mush, these examples preserve robust evidence for the presence of liquid-rich magma chambers in the geological record.
NERC (via University of Manchester) (R118242)
External DOI: https://doi.org/10.1098/rsta.2018.0006
This record's URL: https://www.repository.cam.ac.uk/handle/1810/288252