Prof. Vincenzo Stagno [Sapienza University of Rome, Italy]

Title: Origin and rheology of CO2-rich magmas are controlled by changes in the mantle oxidation state through time

Language:  English presentation

Time: Beijing, 3:00 - 4:00 PM, Tuesday, March 5, 2024

Place:  Conference room A417, HPSTAR (Beijing)    

Host:  Dr. Yanhao Lin

Abstract:

Natural mantle rocks andinclusions in diamonds bring geochemical evidence of the passage of CO2-bearingmagmas formed by redox-assisted partial melting processes in the upper mantle. Dependingon their rheological properties, these melts likely acted as either growthmedia of diamonds or metasomatic agents or ascending magmas eventually eruptedto the terrestrial surface. I will present the results of viscosity and liquidstructure experiments conducted at high pressures and temperatures on severalsynthetic compositions with variable CO2 and SiO2contents to be representative of natural volatile-bearing magmas. The collecteddata aim to establish a relation between mantle redox state and magma rheologybased on which the gradual oxidation of the whole Earth’s interior through timeresulted in the formation of magmas with diverse volatile contents and viscositiesvarying up to 3 orders of magnitude with some implications for the seismicdiscontinuities in depth.

Brief introduction of the speaker: 

Selected publications:Stagno, V., & Frost, D. J. (2010). Carbon speciation in the asthenosphere: Experimental measurements of the redox conditions at which carbonate-bearing melts coexist with graphite or diamond in peridotite assemblages. Earth and Planetary Science Letters, 300(1-2), 72-84.Stagno, V., Tange, Y., Miyajima, N., McCammon, C.A., Irifune, T., & Frost, D.J. (2011). The stability of magnesite in the transition zone and the lower mantle as function of oxygen fugacity. Geophysical Research Letters, 38, L19309.Stagno, V., Ojwang, D. O., McCammon, C. A., & Frost, D. J. (2013). The oxidation state of the mantle and the extraction of carbon from Earth’s interior. Nature, 493(7430), 84-88.Aulbach, S., & Stagno, V. (2016). Evidence for a reducing Archean ambient mantle and its effects on the carbon cycle. Geology, 44, 751-754.Stagno, V., Frost, D.J., McCammon, C.A., Mohseni, H., & Fei, Y.W. (2015). The oxygen fugacity at which graphite or diamond forms from carbonate-bearing melts in eclogitic rocks. Contributions to Mineralogy and Petrology, 169, 1-18.Stagno, V. , & Fei, Y. . (2020). The redox boundaries of earth's interior. Elements, 16(3), 167-172.