Experimental calibration of V–Sc oxybarometers based on clinopyroxene- and orthopyroxene-melt equilibria
Year: 2026
Type: article
Abstract: We present new experimental calibration of V–Sc exchange between clinopyroxene, orthopyroxene, and silicate melt at physical–chemical conditions characteristic of arc magmatism. The calibration combines previously published experimental datasets with new high-pressure rapid-quench experiments conducted in a molybdenum-hafnium carbide pressure vessel assembly equipped with a custom-designed semi-permeable hydrogen membrane to control oxygen fugacity ( f O 2 ). Experiments were performed at 200 MPa under water-saturated conditions, covering temperatures of 1030–870 °C and f O 2 from − 1 to + 7 log units relative to fayalite-magnetite-quartz buffer (FMQ). Melt composition effects were evaluated by comparing liquid lines of descent of medium-K calc-alkaline basaltic and shoshonitic magmas. The resulting orthopyroxene-melt oxybarometer accurately reproduces f O 2 , yielding a median absolute error of 0.36 log units over the range FMQ − 2 to + 5.5. Precise calibration of the clinopyroxene-melt oxybarometer was more challenging due to the clinopyroxene’s more complex composition and potential kinetic effects. Nevertheless, the proposed equation reproduces f O 2 with an overall median absolute error of 1.01 log units over the calibrated range FMQ − 2.5 to + 5. Provided that the equilibrium melt composition can be constrained by the analysis of silicate melt inclusions or groundmass glass, the proposed pyroxene-melt oxybarometers can be used to track the variation of magmatic f O 2 in diverse settings and over a broad temperature range.
Authors: Enzo-Enrico Cacciatore, Zoltán Zajacz
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,990
Funder: Université de Genève
OpenAlex ID: W7203677584