ACTIVE BASALTIC VOLCANISM
Petrology is a powerful tool for analyzing volcanic eruptive products. Using experimentally calibrated thermometers and barometers, we can reconstruct the magma plumbing system beneath a volcano, the shape of magmatic reservoirs, and witness the cooling of lava flows. Disequilibrium features in volcanic rocks can also provide time contraints on reservoir processes (for exemple mixing) and magma ascent rates: diffusion in phenocrysts, size distribution of crystals and bubbles, volatil diffusion in melt inclusions and embayment... Over the past few years, I have been involved in a series of projects that apply petrology to the understanding of ongoing mafic volcanic eruptions:
- Eruptions in the Vanuatu arc, including the 2017-2018 eruption on Ambae, and the december 2018 eruption on Ambrym
- Large submarine eruption offshore Mayotte, ongoing since 2018
- Various eruptions of Piton de la Fournaise, Réunion island
- Eruptions in the Vanuatu arc, including the 2017-2018 eruption on Ambae, and the december 2018 eruption on Ambrym
- Large submarine eruption offshore Mayotte, ongoing since 2018
- Various eruptions of Piton de la Fournaise, Réunion island
VANUATU ARC
I have recalibrated an accurate Al-in hornblende barometer from experimental litterature data on rhyolites (Médard and Le Pennec, submitted). This new barometer takes into account the effect of both edenite and Tschermack substitutions on Al concentrations. Existing litterature data show a very good pressure-dependence of the Tschermack substitution (correlation coefficient of 0.95) for amphibole in equilibrium with biotite, plagioclase and quartz. Our new barometer reproduces experimental pressures with an average error of 58 MPa (equivalent to a depth of 2.2 km) in the 100-400 MPa range. More experiments are underway to improve the barometer’s accuracy. Compared to previous barometers, this new calibration is independent of temperature, and gives a much better resolution for magma chamber depth.
Collaborators: Philipson Bani, François Nauret, Estelle Rose-Koga, Yves Moussallam, Kenneth Koga, Christy Harruel (PhD student)
Moussallam Y, Médard E, Georgeais G, Rose-Koga EF, Koga KT, Pelletier B, Bani P, Grandin R, Boichu M, Shreve TL, Tari D, Peters N (submitted) How to turn off a lava lake? A petrological investigation of the 2018 intra-caldera and submarine eruptions of Ambrym volcano.
Moussallam Y, Rose-Koga EF, Koga KT, Médard E, Bani P, Devidal JL, Tari D (2019) Fast ascent rate during the 2017-2018 Plinian eruption of Ambae (Aoba) volcano; a petrological investigation. Contribution to Mineralogy and Petrology 174: 90, doi: 10.1007/s00410-019-1625-z.
Collaborators: Philipson Bani, François Nauret, Estelle Rose-Koga, Yves Moussallam, Kenneth Koga, Christy Harruel (PhD student)
Moussallam Y, Médard E, Georgeais G, Rose-Koga EF, Koga KT, Pelletier B, Bani P, Grandin R, Boichu M, Shreve TL, Tari D, Peters N (submitted) How to turn off a lava lake? A petrological investigation of the 2018 intra-caldera and submarine eruptions of Ambrym volcano.
Moussallam Y, Rose-Koga EF, Koga KT, Médard E, Bani P, Devidal JL, Tari D (2019) Fast ascent rate during the 2017-2018 Plinian eruption of Ambae (Aoba) volcano; a petrological investigation. Contribution to Mineralogy and Petrology 174: 90, doi: 10.1007/s00410-019-1625-z.
MAYOTTE VOLCANIC CRISIS
I have recalibrated an accurate Al-in hornblende barometer from experimental litterature data on rhyolites (Médard and Le Pennec, submitted). This new barometer takes into account the effect of both edenite and Tschermack substitutions on Al concentrations. Existing litterature data show a very good pressure-dependence of the Tschermack substitution (correlation coefficient of 0.95) for amphibole in equilibrium with biotite, plagioclase and quartz. Our new barometer reproduces experimental pressures with an average error of 58 MPa (equivalent to a depth of 2.2 km) in the 100-400 MPa range. More experiments are underway to improve the barometer’s accuracy. Compared to previous barometers, this new calibration is independent of temperature, and gives a much better resolution for magma chamber depth.
Collaborators: Carole Berthod, Lucia Gurioli, Patrick Bachèlery, Andrea Di Muro
Berthod C, Médard E, Bachèlery P, Gurioli L, Di Muro A, Peltier A, Komorowski JC, Benbakkar M, Devidal JL, Langlade J, Besson P, Boudon G, Rose-Koga E, Deplus C, Le Friant A, Bickert M, Nowak S, Thinon I, Burckel P, Hidalgo S, Kaliwoda M, Jorry S, Fouquet Y, Feuillet N (submitted) The 2018-ongoing Mayotte submarine eruption: magma migration imaged by petrological monitoring.
Collaborators: Carole Berthod, Lucia Gurioli, Patrick Bachèlery, Andrea Di Muro
Berthod C, Médard E, Bachèlery P, Gurioli L, Di Muro A, Peltier A, Komorowski JC, Benbakkar M, Devidal JL, Langlade J, Besson P, Boudon G, Rose-Koga E, Deplus C, Le Friant A, Bickert M, Nowak S, Thinon I, Burckel P, Hidalgo S, Kaliwoda M, Jorry S, Fouquet Y, Feuillet N (submitted) The 2018-ongoing Mayotte submarine eruption: magma migration imaged by petrological monitoring.
PITON DE LA FOURNAISE, REUNION
I have recalibrated an accurate Al-in hornblende barometer from experimental litterature data on rhyolites (Médard and Le Pennec, submitted). This new barometer takes into account the effect of both edenite and Tschermack substitutions on Al concentrations. Existing litterature data show a very good pressure-dependence of the Tschermack substitution (correlation coefficient of 0.95) for amphibole in equilibrium with biotite, plagioclase and quartz. Our new barometer reproduces experimental pressures with an average error of 58 MPa (equivalent to a depth of 2.2 km) in the 100-400 MPa range. More experiments are underway to improve the barometer’s accuracy. Compared to previous barometers, this new calibration is independent of temperature, and gives a much better resolution for magma chamber depth.
We have been performing detailed thermometric studies on basaltic lava channels at Kilauea (Hawaii) and Piton de la Fournaise (Reunion Island, Indian Ocean). With careful sampling and sample preparation, the olivine/liquid thermometer of Ford (1983) gives enough precision to be able to calculate cooling rates in lava channels. Values of about 7 °C/km have been determined for the Muliwai a Pele lava channel emplaced during the final stage of Mauna Ulu’s 1969–1974 eruption. These values are then integrated into multiparameters models of lava flows that can be then used for prediction of lava flow paths.
Collaborators: Lucia Gurioli, Andrea Di Muro
We have been performing detailed thermometric studies on basaltic lava channels at Kilauea (Hawaii) and Piton de la Fournaise (Reunion Island, Indian Ocean). With careful sampling and sample preparation, the olivine/liquid thermometer of Ford (1983) gives enough precision to be able to calculate cooling rates in lava channels. Values of about 7 °C/km have been determined for the Muliwai a Pele lava channel emplaced during the final stage of Mauna Ulu’s 1969–1974 eruption. These values are then integrated into multiparameters models of lava flows that can be then used for prediction of lava flow paths.
Collaborators: Lucia Gurioli, Andrea Di Muro
OLDER VOLCANISM
We have been performing detailed thermometric studies on XXth century basaltic lava channels at Kilauea (Hawaii) and Piton de la Fournaise (Reunion Island, Indian Ocean). With careful sampling and sample preparation, the olivine/liquid thermometer of Ford (1983) gives enough precision to be able to calculate cooling rates in lava channels. Values of about 7 °C/km have been determined for the Muliwai a Pele lava channel emplaced during the final stage of Mauna Ulu’s 1969–1974 eruption. These values are then integrated into multiparameters models of lava flows that can be then used for prediction of lava flow paths.
Fig. 3. Glass in equilibrium with olivine, plagioclase and clinopyroxene from the Mauna Ulu eruption of Kilauea
OLDER publications
Elahpour E, Nauret F, Médard E, Benbakkar M, Quéinnec G, van Wyk de Vries B (2019) The petrogenesis and geochemistry of Tabas Black Land volcanic field: implications for volcanic activity along the Nayband fault, East Iran. Volcanica 2(2): 105-127, doi: 10.30909/vol.02.02.105127.
Rhéty M, Harris AJ, Villeneuve N, Gurioli L, Médard E, Chevrel O, Bachélery P (2017) A comparison of cooling- and volume-limited flow systems: examples from channels in the Piton de la Fournaise April 2007 lava flow field. Geochemistry, Geophysics, Geosystems 18: 3270-3291, doi: 10.1002/2017GC006839.
Sehlke A, Whittington A, Robert B, Harris AJ, Gurioli L, Médard E (2014) Pahoehoe to `a`a transition of Hawaiian lavas: an experimental study. Bulletin of Volcanology 76: 876, doi: 10.1007/s00445-014-0876-9.
Robert B, Harris AJ, Gurioli L, Médard E, Sehlke A, Whittington A (2014) Textural and rheological evolution of basalt flowing down a lava channel. Bulletin of Volcanology 76: 824, doi: 10.1007/s00445-014-0824-8.
Hetényi G, Taisne B, Garel F, Médard E, Bosshard S, Mattsson HB (2012) Scales of columnar jointing in igneous rocks: field measurements and controlling factors. Bulletin of Volcanology 74: 457-482, doi: 10.1007/s00445-011-0534-4.
Rhéty M, Harris AJ, Villeneuve N, Gurioli L, Médard E, Chevrel O, Bachélery P (2017) A comparison of cooling- and volume-limited flow systems: examples from channels in the Piton de la Fournaise April 2007 lava flow field. Geochemistry, Geophysics, Geosystems 18: 3270-3291, doi: 10.1002/2017GC006839.
Sehlke A, Whittington A, Robert B, Harris AJ, Gurioli L, Médard E (2014) Pahoehoe to `a`a transition of Hawaiian lavas: an experimental study. Bulletin of Volcanology 76: 876, doi: 10.1007/s00445-014-0876-9.
Robert B, Harris AJ, Gurioli L, Médard E, Sehlke A, Whittington A (2014) Textural and rheological evolution of basalt flowing down a lava channel. Bulletin of Volcanology 76: 824, doi: 10.1007/s00445-014-0824-8.
Hetényi G, Taisne B, Garel F, Médard E, Bosshard S, Mattsson HB (2012) Scales of columnar jointing in igneous rocks: field measurements and controlling factors. Bulletin of Volcanology 74: 457-482, doi: 10.1007/s00445-011-0534-4.