The volumes of CO2 released at some basaltic volcanoes (e.g., Etna, Stromboli) significantly exceed the limits of solubility in silicate melt, indicating flushing by deep, CO2-rich fluids from crustal and mantle sources. A similar flushing mechanism in silicic magmatic systems has been less evident. Here, we propose that H2O–CO2 contents in quartz-hosted melt inclusions (MIs) can serve as an indicator of interaction between hydrous rhyolitic magma and carbonic fluid. Numerical modeling of this interaction process at the single-bubble scale, accounting for volatile diffusivity dependencies on water content, demonstrates that a uniformly dehydrated melt with highly variable CO2 concentrations can form on relatively short timescales. In natural magma bodies where bubble coalescence and escape occur, this process generates melt compositions that form subvertical arrays on H2O–CO2 diagrams. Such compositions, preserved in melt inclusions, are commonly found in pyroclastic deposits from catastrophic intraplate rhyolitic eruptions, such as those of the Yellowstone caldera. Reinterpretation of extensive published MI data from the pre-Huckleberry Ridge Tuff-A ashfall deposits at Yellowstone reveals episodes of carbonic fluid-magma interaction that likely initiated explosive eruptions. The first eruptive cycle is associated with flushing at the basal boundary layer of the magma chamber by a fluid enriched in CO2 and Li. The resulting bubbly layer would ascend rapidly, being captured in the earliest erupted magma that forms the base of the ash sequence. MIs from this level show a strong positive correlation between CO2 and Li concentrations. In contrast, a significant negative correlation between CO2 and Li is observed in MIs from near the top of the 2-meter-thick ash sequence. This pattern is attributed to a second, distinct flushing episode by a Li-poor fluid, which culminated in the massive early Huckleberry Ridge Tuff (HRT-A) ignimbrite eruption that overlies the ashfall deposits. Other samples exhibit a strong positive correlation between Li and H2O, explainable by syneruptive diffusive loss of both components. Diffusive water loss from reentrants and MIs consistently indicates a syneruptive magma decompression rate of ~0.02–0.06 MPa/s. Finally, the unusual population of reentrants and MIs with uniformly low H2O (1–1.5 wt.%) but variable-to-high CO2 contents at the top of the ash section can be explained by dehydration during interaction with (or formation from) a water-poor melt. This melt was likely generated by remelting of largely solidified rhyolite, underplated by basalt, as an alternative or complementary process to CO2 flushing.
Citation: Alexander G Simakin, Vera N Devyatova. Fluxing with CO2 of rhyolitic magma at the beginning of an eruption—scholastic concept or reality?[J]. AIMS Geosciences, 2026, 12(2): 388-422. doi: 10.3934/geosci.2026015
The volumes of CO2 released at some basaltic volcanoes (e.g., Etna, Stromboli) significantly exceed the limits of solubility in silicate melt, indicating flushing by deep, CO2-rich fluids from crustal and mantle sources. A similar flushing mechanism in silicic magmatic systems has been less evident. Here, we propose that H2O–CO2 contents in quartz-hosted melt inclusions (MIs) can serve as an indicator of interaction between hydrous rhyolitic magma and carbonic fluid. Numerical modeling of this interaction process at the single-bubble scale, accounting for volatile diffusivity dependencies on water content, demonstrates that a uniformly dehydrated melt with highly variable CO2 concentrations can form on relatively short timescales. In natural magma bodies where bubble coalescence and escape occur, this process generates melt compositions that form subvertical arrays on H2O–CO2 diagrams. Such compositions, preserved in melt inclusions, are commonly found in pyroclastic deposits from catastrophic intraplate rhyolitic eruptions, such as those of the Yellowstone caldera. Reinterpretation of extensive published MI data from the pre-Huckleberry Ridge Tuff-A ashfall deposits at Yellowstone reveals episodes of carbonic fluid-magma interaction that likely initiated explosive eruptions. The first eruptive cycle is associated with flushing at the basal boundary layer of the magma chamber by a fluid enriched in CO2 and Li. The resulting bubbly layer would ascend rapidly, being captured in the earliest erupted magma that forms the base of the ash sequence. MIs from this level show a strong positive correlation between CO2 and Li concentrations. In contrast, a significant negative correlation between CO2 and Li is observed in MIs from near the top of the 2-meter-thick ash sequence. This pattern is attributed to a second, distinct flushing episode by a Li-poor fluid, which culminated in the massive early Huckleberry Ridge Tuff (HRT-A) ignimbrite eruption that overlies the ashfall deposits. Other samples exhibit a strong positive correlation between Li and H2O, explainable by syneruptive diffusive loss of both components. Diffusive water loss from reentrants and MIs consistently indicates a syneruptive magma decompression rate of ~0.02–0.06 MPa/s. Finally, the unusual population of reentrants and MIs with uniformly low H2O (1–1.5 wt.%) but variable-to-high CO2 contents at the top of the ash section can be explained by dehydration during interaction with (or formation from) a water-poor melt. This melt was likely generated by remelting of largely solidified rhyolite, underplated by basalt, as an alternative or complementary process to CO2 flushing.
| [1] |
Huppert H, Woods AW (2002) The role of volatiles in magma chamber dynamics. Nature 420: 493–495. https://doi.org/10.1038/nature01211 doi: 10.1038/nature01211
|
| [2] | Simakin AG, Ghassemi A (2018) Mechanics of magma chamber with implication to the effect of CO2 fluxing, Volcanoes: Geological and Geophysical Setting, Theoretical Aspects and Numerical Modeling, Applications to Industry and Their Impact on the Human Health, 175–207. http://dx.doi.org/10.5772/intechopen.71655 |
| [3] |
Thomas N, Tait S, Koyaguchi T (1993) Mixing of stratified liquids by the motion of gas bubbles: application to magma mixing. Earth Planet Sci Lett 115: 161–175. https://doi.org/10.1016/0012-821X(93)90220-4 doi: 10.1016/0012-821X(93)90220-4
|
| [4] |
Simakin A, Schmeling H, Trubitsyn V (1997) Convection in melts due to sedimentary crystal flux from above. Phys Earth Planet Inter 102: 185–200. https://doi.org/10.1016/S0031-9201(97)00010-1 doi: 10.1016/S0031-9201(97)00010-1
|
| [5] | Steinberg GS, Steinberg AG, Merzhanov AG (1989) Fluid mechanism of pressure growth in volcanic (magmatic) systems. Mod Geol 13: 257–265. |
| [6] |
Seropian G, Kennedy BM, Walter TR, et al. (2021) A review framework of how earthquakes trigger volcanic eruptions. Nat Commun 12: 1004. https://doi.org/10.1038/s41467-021-21166-8 doi: 10.1038/s41467-021-21166-8
|
| [7] |
Bagdassarov N (1994) Pressure and volume changes in magmatic systems due to the vertical displacement of compressible materials. J Volcanol Geotherm Res 63: 95–100. https://doi.org/10.1016/0377-0273(94)90020-5 doi: 10.1016/0377-0273(94)90020-5
|
| [8] |
Simakin AG (2010) The role of intercameral degassing of andesite magma of the Shiveluch volcano (Kamchatka). Dokl Earth Sci 431: 458–461. https://doi.org/10.1134/S1028334X10040100 doi: 10.1134/S1028334X10040100
|
| [9] |
Simakin AG, Devyatova VN, Shiryaev AA (2023) Theoretical and Experimental Modeling of Local Scale CO2 Flushing of Hydrous Rhyolitic Magma. Russ J Earth Sci 23. https://doi.org/10.2205/2023es000871 doi: 10.2205/2023es000871
|
| [10] |
Befus KS, Manga M (2019) Supereruption quartz crystals and the hollow reentrants Supereruption quartz crystals and the hollow reentrants. Geology 47: 710–714. https://doi.org/10.1130/G46275.1 doi: 10.1130/G46275.1
|
| [11] |
Yoshimura S, Nakamura M (2010) Chemically driven growth and resorption of bubbles in a multivolatile magmatic system. Chem Geol 276: 18–28. https://doi.org/10.1016/j.chemgeo.2010.05.010 doi: 10.1016/j.chemgeo.2010.05.010
|
| [12] |
Yoshimura S, Nakamura M (2011) Carbon dioxide transport in crustal magmatic systems. Earth Planet Sci Lett 307: 470–478. https://doi.org/10.1016/j.epsl.2011.05.039 doi: 10.1016/j.epsl.2011.05.039
|
| [13] |
Yoshimura S, Nakamura M (2013) Flux of volcanic CO2 emission estimated from melt inclusions and fluid transport modelling. Earth Planet Sci Lett 361: 497–503. https://doi.org/10.1016/j.epsl.2012.11.020 doi: 10.1016/j.epsl.2012.11.020
|
| [14] |
Severs MJ, Azbej T, Thomas JB, et al. (2007) Experimental determination of H2O loss from melt inclusions during laboratory heating: Evidence from Raman spectroscopy. Chem Geol 237: 358–371. https://doi.org/10.1016/j.chemgeo.2006.07.008 doi: 10.1016/j.chemgeo.2006.07.008
|
| [15] |
Myers ML, Wallace PJ, Wilson CJN, et al. (2016) Prolonged ascent and episodic venting of discrete magma batches at the onset of the Huckleberry Ridge supereruption, Yellowstone. Earth Planet Sci Lett 451: 285–297. https://doi.org/10.1016/j.epsl.2016.07.023 doi: 10.1016/j.epsl.2016.07.023
|
| [16] |
Zelenski M, Simakin A, Taran Yu, et al. (2021) Partitioning of elements between high-temperature, low-density aqueous fluid and silicate melt as derived from volcanic gas geochemistry. Geochim Cosmochim Acta 295: 112–134. https://doi.org/10.1016/j.gca.2020.12.011 doi: 10.1016/j.gca.2020.12.011
|
| [17] |
Kerrick DM, Jacobs GK (1981) A Modified Redlich Kwong equation of state for H2O, CO2, and H2O–CO2 mixtures at elevated pressures and temperatures. Am J Sci 281: 735–767. https://doi.org/10.2475/ajs.281.6.735 doi: 10.2475/ajs.281.6.735
|
| [18] |
Nowak M, ·Behrens H (1997) An experimental investigation on diffusion of water in haplogranitic melts. Contrib Mineral Petrol 126: 365–376. https://doi.org/10.1007/s004100050256 doi: 10.1007/s004100050256
|
| [19] |
Zhang Y, Ni H (2010) Diffusion of H, C, and O Components in Silicate Melts. Rev Mineral Geochem 72: 171–225. https://doi.org/10.2138/rmg.2010.72.5 doi: 10.2138/rmg.2010.72.5
|
| [20] |
Watson EB (1991) Diffusion of dissolved CO2 and Cl in hydrous silicic to intermediate magmas. Geochim Cosmochim Acta 55: 1897–1902. https://doi.org/10.1016/0016-7037(91)90031-Y doi: 10.1016/0016-7037(91)90031-Y
|
| [21] |
Yoshimura S (2015) Diffusive fractionation of H2O and CO2 during magma degassing. Chem Geol 411: 172–181. https://doi.org/10.1016/j.chemgeo.2015.07.003 doi: 10.1016/j.chemgeo.2015.07.003
|
| [22] |
Pichavant M, Di Carlo I, Rotolo SG, et al. (2013) Generation of CO2-rich melts during basalt magma ascent and degassing. Contrib Mineral Petrol 166: 545–561. https://doi.org/10.1007/s00410-013-0890-5 doi: 10.1007/s00410-013-0890-5
|
| [23] |
Befus KS, Gardner JE (2016) Magma storage and evolution of the most recent effusive and explosive eruptions from Yellowstone Caldera. Contrib Mineral Petrol 171: 30. https://doi.org/10.1007/s00410-016-1244-x doi: 10.1007/s00410-016-1244-x
|
| [24] |
Barth A, Plank T (2021) The Ins and Outs of Water in Olivine-Hosted Melt Inclusions: Hygrometer vs. Speedometer. Front Earth Sci 9: 614004. https://doi.org/10.3389/feart.2021.614004 doi: 10.3389/feart.2021.614004
|
| [25] |
Simakin AG, Bindeman IN (2022) Convective Melting and Water Behavior around Magmatic-Hydrothermal Transition: Numerical Modeling with Application to Krafla Volcano, Iceland. J Petrol 63: egac074. https://doi.org/10.1093/petrology/egac074 doi: 10.1093/petrology/egac074
|
| [26] |
Anderson AT, Davis AM, Lu F (2000) Evolution of Bishop Tuff rhyolitic magma based on melt and magnetite inclusions and zoned phenocrysts. J Petrol 41: 449–473. https://doi.org/10.1093/petrology/41.3.449 doi: 10.1093/petrology/41.3.449
|
| [27] |
Hencz M, Biró T, Kovács IJ (2021) Uniform "water" content in quartz phenocrysts from silicic pyroclastic fallout deposits – implications on pre-eruptive conditions. Eur J Mineral 33: 571–589. https://doi.org/10.5194/ejm-33-571-2021 doi: 10.5194/ejm-33-571-2021
|
| [28] | Kats A (1962) Hydrogen in alpha-quartz. Philips Res Rep 17: 133–195,201–279. https://resolver.tudelft.nl/uuid:ab91c719-f00b-4362-ade3-8d44db910980 |
| [29] |
Jollands MC, Ellis B, Tollan PME, et al. (2020) An eruption chronometer based on experimentally determined H-Li and H-Na diffusion in quartz applied to the Bishop Tuff. Earth Planet Sci Lett 551: 116560. https://doi.org/10.1016/j.epsl.2020.116560 doi: 10.1016/j.epsl.2020.116560
|
| [30] |
Bachheimer JP (1998) An investigation into hydrogen stability in synthetic, natural and air-swept synthetic quartz in air temperatures up to 1100℃. J Phys Chem Solids S9: 831–840. https://doi.org/10.1016/S0022-3697(96)00164-3 doi: 10.1016/S0022-3697(96)00164-3
|
| [31] | Abdisa LT (2021) One Dimensional Heat Equation and its Solution by the Methods of Separation of Variables, Fourier Series and Fourier Transform. J Appl Comp Math 10: 1–6. |
| [32] |
Ferguson DJ, Gonnermann HM, Ruprecht P, et al. (2016) Magma decompression rates during explosive eruptions of Kilauea volcano, Hawaii, recorded by melt embayments. Bull Volcanol 78: 71. https://doi.org/10.1007/s00445-016-1064-x doi: 10.1007/s00445-016-1064-x
|
| [33] | Myers ML, Wallace PJ, Wilson CJN, et al. (2018) Ascent rates of rhyolitic magma at the onset of three caldera-forming eruptions. Am Mineral 103: 952–965. |
| [34] |
Myers ML, Wallace PJ, Wilson CJN (2019) Inferring magma ascent timescales and reconstructing conduit processes in explosive rhyolitic eruptions using diffusive losses of hydrogen from melt inclusions. J Volcanol Geotherm Res 369: 95–112. https://doi.org/10.1016/j.jvolgeores.2018.11.009 doi: 10.1016/j.jvolgeores.2018.11.009
|
| [35] |
Myers ML, Druitt TH, Schiavi F, et al. (2021) Evolution of magma decompression and discharge during a Plinian event (Late Bronze-Age eruption, Santorini) from multiple eruption-intensity proxies. Bull Volcanol 83: 18. https://doi.org/10.1007/s00445-021-01438-3 doi: 10.1007/s00445-021-01438-3
|
| [36] |
Mutch EJF, Newcombe ME, Rudge JF (2024) 3D diffusion of water in melt inclusion‐bearing olivine phenocrysts. Geochem Geophys Geosyst 25: e2023GC011365. https://doi.org/10.1029/2023GC011365 doi: 10.1029/2023GC011365
|
| [37] |
Befus KS, Ruefer AC, Allison CM, et al. (2023) Quartz-hosted inclusions and embayments reveal storage, fluxing, and ascent of the Mesa Falls Tuff, Yellowstone. Earth Planet Sci Lett 601: 117909. https://doi.org/10.1016/j.epsl.2022.117909 doi: 10.1016/j.epsl.2022.117909
|
| [38] |
Gordeychik B, Churikova T, Shea T, et al. (2020) Fo and Ni relations in olivine differentiate between crystallization and diffusion trends. J Petrol 61: egaa083. https://doi.org/10.1093/petrology/egaa083 doi: 10.1093/petrology/egaa083
|
| [39] |
Neukampf J, Laurent O, Tollan P, et al. (2022) Degassing from magma reservoir to eruption in silicic systems: The Li elemental and isotopic record from rhyolitic melt inclusions and host quartz in a Yellowstone rhyolite. Geochim Cosmochim Acta 326: 56–76. https://doi.org/10.1016/j.gca.2022.03.037 doi: 10.1016/j.gca.2022.03.037
|
| [40] |
Swallow EJ, Wilson CJ, Myers ML, et al. (2018) Evacuation of multiple magma bodies and the onset of caldera collapse in a supereruption, captured in glass and mineral compositions. Contrib Mineral Petrol 173: 33. https://doi.org/10.1007/s00410-018-1459-0 doi: 10.1007/s00410-018-1459-0
|
| [41] | Christiansen RL (2001) The quaternary and pliocene Yellowstone Plateau volcanic field of Wyoming, Idaho, and Montana, US Department of the Interior, US Geological Survey. 729. |
| [42] |
Stelten ME, Cooper KM, Vazquez JA, et al. (2015) Mechanisms and timescales of generating eruptible rhyolitic magmas at Yellowstone caldera from zircon and sanidine geochronology and geochemistry. J Petrol 56: 1607–1642. https://doi.org/10.1093/petrology/egv047 doi: 10.1093/petrology/egv047
|
| [43] |
Wilke S, Klahn C, Bolte T, et al. (2015) Experimental investigation of the effect of Ca, Fe and Ti on cotectic compositions of the rhyolitic system. Eur J Mineral 27: 147–159. https://doi.org/10.1127/ejm/2015/0027-2423 doi: 10.1127/ejm/2015/0027-2423
|
| [44] |
Zakirov IV, Sretenskaja NG, Aranovich LY, et al. (2007) Solubility of NaCl in CO2 at high pressure and temperature: First experimental measurements. Geochim Cosmochim Acta 71: 4251–4255. https://doi.org/10.1016/j.gca.2007.01.028 doi: 10.1016/j.gca.2007.01.028
|
| [45] |
Berkesi M, Guzmics T, Szabо C, et al. (2012) The role of CO2 rich fluids in trace element transport and metasomatism in the lithospheric mantle beneath the Central Pannonian Basin, Hungary, based on fluid inclusions in mantle xenoliths. Earth Planet Sci Lett 331–332: 8–20. https://doi.org/10.1016/j.epsl.2012.03.012 doi: 10.1029/2019GL083619
|
| [46] |
Befus KS, Manga M, Stan C, et al. (2019) Supervolcanoes erupt stressed quartz crystals. Geophys Res Lett 46: 8791–8800. https://doi.org/10.1029/2019GL083619 doi: 10.1029/2019GL083619
|
| [47] |
Giuffrida M, Viccaro M, Ottolini L (2018) Ultrafast syn-eruptive degassing and ascent trigger high-energy basic eruptions. Sci Rep 8: 147. https://doi.org/10.1038/s41598-017-18580-8 doi: 10.1038/s41598-017-18580-8
|
| [48] |
Bonadonna C, Ernst GGJ, Sparks RSJ (1998) Thickness variations and volume estimates of tephra fall deposits: the importance of particle Reynolds number. J Volcanol Geoth Res 81: 173–187. https://doi.org/10.1016/s0377-0273(98)00007-9 doi: 10.1016/s0377-0273(98)00007-9
|
| [49] |
Spera FJ (1984) Some Numerical Experiments on the Withdrawal of Magma From Crustal Reservoirs. J Geophys Res 89: 8222–8236. https://doi.org/10.1029/JB089iB10p08222 doi: 10.1029/JB089iB10p08222
|
| [50] |
Botcharnikov R, Freise M, Holtz F, et al. (2005) Solubility of COH mixtures in natural melts: new experimental data and application range of recent models. Ann Geophys 48: 633–646. https://doi.org/10.4401/ag-3224 doi: 10.4401/ag-3224
|
| [51] |
DeNosaquo KR, Smith RB, Lowry AR (2009) Density and lithospheric strength models of the Yellowstone–Snake River Plain volcanic system from gravity and heat flow data. J Volcanol Geoth Res 188: 108–127. https://doi.org/10.1016/j.jvolgeores.2009.08.006 doi: 10.1016/j.jvolgeores.2009.08.006
|
| [52] |
Jellinek AM, DePaolo DJ (2003) A model for the origin of large silicic magma chambers: precursors of caldera-forming eruptions. Bull Volcanol 65: 363–381. https://doi.org/10.1007/s00445-003-0277-y doi: 10.1007/s00445-003-0277-y
|
| [53] |
Simakin AG, Ghassemi A (2010) The role of magma chamber-fault interaction in caldera forming eruptions. Bull Volcanol 72: 85–101. https://doi.org/10.1007/s00445-009-0306-6 doi: 10.1007/s00445-009-0306-6
|
| [54] |
Caricchi L, Annen C, Blundy J, et al. (2014) Frequency and magnitude of volcanic eruptions controlled by magma injection and buoyancy. Nature Geosci 7: 126–130. https://doi.org/10.1038/ngeo2041 doi: 10.1038/ngeo2041
|
 geosci-12-02-015-s001.pdf |
 |
| geosci-12-02-015-s002.pdf |
|
Figures(16) / Tables(1)
Alexander G Simakin, Vera N Devyatova. Fluxing with CO2 of rhyolitic magma at the beginning of an eruption—scholastic concept or reality?[J]. AIMS Geosciences, 2026, 12(2): 388-422. doi: 10.3934/geosci.2026015
DownLoad: