A low-aluminum clinopyroxene-liquid geothermometer for high-silica magmatic systems

Karalee K. Brugman, Christy Till

Research output: Contribution to journalArticle

Abstract

Several geothermobarometric tools have focused on clinopyroxene due to its prevalence in igneous rocks, however clinopyroxene produced in high-silica igneous systems is high in iron and low in aluminum, causing existing geothermometers that depend on aluminum exchange to fail or yield overestimated temperatures. Here we present a new clinopyroxene-liquid geothermometer recommended for use in natural igneous systems with bulk SiO2 ≥ 70 wt%, which contain clinopyroxene with {equation presented} The new geothermometer lowers calculated temperatures by ~85 °C on average relative to Putirka (2008, Eq. 33) and reduces the uncertainty by a factor of two (standard error of estimate ±20 °C). When applied to natural systems, we find this new clinopyroxene-liquid geothermometer reconciles many inconsistencies between experimental phase equilibria and preexisting geothermometry results for silicic volcanism, including those from the Bishop Tuff and Yellowstone caldera-forming and post-caldera rhyolites. We also demonstrate that clinopyroxene is not restricted to near-liquidus temperatures in rhyolitic systems; clinopyroxene can be stable over a broad temperature range, often down to the solidus. An Excel spreadsheet and Python notebook for calculating temperature with this new geothermometer may be downloaded from GitHub at http://bit.ly/cpxrhyotherm.

Original languageEnglish (US)
Pages (from-to)996-1004
Number of pages9
JournalAmerican Mineralogist
Volume104
Issue number7
DOIs
StatePublished - Jul 1 2019

Fingerprint

Aluminum
Silicon Dioxide
clinopyroxene
aluminum
silica
silicon dioxide
liquid
calderas
Liquids
liquids
geotemperature
spreadsheets
Temperature
temperature
solidus
igneous rocks
caldera
Igneous rocks
liquidus
Spreadsheets

Keywords

  • clinopyroxene
  • Geothermometer
  • high-silica

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

Cite this

A low-aluminum clinopyroxene-liquid geothermometer for high-silica magmatic systems. / Brugman, Karalee K.; Till, Christy.

In: American Mineralogist, Vol. 104, No. 7, 01.07.2019, p. 996-1004.

Research output: Contribution to journalArticle

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