Textural and chemical consequences of interaction between hydrous mafic and felsic magmas: an experimental study

Mattia Pistone*, Jon D Blundy, Richard A Brooker, EIMF (Edinburgh Ion Microprobe Facility)

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

25 Citations (Scopus)
317 Downloads (Pure)

Abstract

Mantle-derived, hydrous mafic magmas are often invoked as a mechanism to transfer heat, mass and volatiles to felsic plutons in the Earth’s crust. Field observations suggest that mafic, water-rich magmas often intrude viscous felsic crystal-rich mushes. This scenario can advect water from the crystallising mafic magma to the felsic magma, leading to an increase in melt fraction in the felsic mush and subsequent mobilisation, at the same time as the mafic magma becomes quenched through a combination of cooling and water loss. To investigate such a scenario, we conducted experiments on a water-undersaturated (4 wt% H2O in the interstitial melt) dacitic crystal mush (50–80 vol% quartz crystals) subject to volatile supply from a water-saturated (≥6 wt% H2O) andesite magma at 950 °C and 4 kbar. Our experimental run products show unidirectional solidification textures (i.e. comb layering) as crystals nucleate at the mafic–felsic interface and grow into the mafic end-member. This process is driven by isothermal and isobaric undercooling resulting from a change in liquidus temperature as water migrates from the mafic to the felsic magma. We refer to this process as “chemical quenching” and suggest that some textures associated with natural mafic–felsic interactions are not simply cooling-driven in origin, but can be caused by exsolution of volatiles adjacent to an interface, whether a water-undersaturated felsic magma (as in our experiments) or a fracture.

Original languageEnglish
Article number8
Number of pages21
JournalContributions to Mineralogy and Petrology
Volume171
Issue number1
Early online date21 Dec 2015
DOIs
Publication statusPublished - 1 Jan 2016

Keywords

  • Comb layering
  • Diffusion
  • Magma
  • Mixing
  • Undercooling
  • Water

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