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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian

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Volume 104, Issue 6


The ascent of water-rich magma and decompression heating: A thermodynamic analysis

Allen F. Glazner
  • Department of Geological Sciences, University of North Carolina, Chapel Hill, North Carolina 27599-3315, U.S.A Orcid 0000-0002-3111-5885
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Published Online: 2019-05-27 | DOI: https://doi.org/10.2138/am-2019-6925


The ascent of hydrous, silica-rich magmas from the lower crust drives volcanic eruptions, builds the upper crust, and concentrates metals such as Cu, Au, and Mo into ore deposits. Owing to the negative slope of the melting curve for granitic materials in the presence of water, it has long been assumed that water-saturated magmas move into the subsolidus field and freeze upon ascent; therefore, for magma to rise it must be water-undersaturated at a temperature well above the solidus. This assumption ignores the considerable energy released by crystallization. Here I show that if magma ascent is treated as an adiabatic, reversible process, then water-saturated magma can rise to the surface, following the solidus to shallow depth and higher temperature as it undergoes modest crystallization and vapor exsolution. Decompression heating is an alternative to magma recharge for explaining pre-eruptive reheating seen in many volcanic systems and accounts for paradoxical growth of quartz during a heating event. The viscosity increase that accompanies vapor exsolution as magma rises to shallow depth explains why silicic magmas tend to stop in the upper crust rather than erupting, producing the observed compositional dichotomy between plutonic and volcanic rocks.

Keywords: Thermodynamics; magma; decompression; adiabatic; granite; rhyolite

References cited

  • Ague, J.J., and Brimhall, G.H. (1988) Magmatic arc asymmetry and distribution of anomalous plutonic belts in the batholiths of California; effects of assimilation, crustal thickness, and depth of crystallization. Geological Society of America Bulletin, 100, 912–927.Google Scholar

  • Annen, C., Scaillet, B., and Sparks, R.S.J. (2006) Thermal constraints on the emplacement rate of a large intrusive complex; the Manaslu Leucogranite, Nepal Himalaya. Journal of Petrology, 47, 71–95.Google Scholar

  • Asimow, P.D. (2000) Melting the mantle. In H. Sigurdsson, Ed., Encyclopedia of Volcanoes pp. 55–68. Academic Press, San Diego.Google Scholar

  • Bagdonas, D.A., Frost, C.D., and Fanning, C.M. (2016) The origin of extensive Neoarchean high-silica batholiths and the nature of intrusive complements to silicic ignimbrites: Insights from the Wyoming batholith, U.S.A. American Mineralogist, 101, 1332–1347.Google Scholar

  • Beard, J.S., and Lofgren, G.E. (1991) Dehydration melting and water-saturated melting of basaltic and andesitic greenstones and amphibolites at 1, 3, and 6.9 kb. Journal of Petrology, 32, 365–401.Google Scholar

  • Blundy, J., and Cashman, K. (2001) Ascent-driven crystallisation of dacite magmas at Mount St. Helens 1980-1986. Contributions to Mineralogy and Petrology, 140, 631–650.Google Scholar

  • Blundy, J., Cashman, K., and Humphreys, M. (2006) Magma heating by decompression-driven crystallization beneath andesite volcanoes. Nature, 443, 76–80.Google Scholar

  • Bowen, N.L. (1915) The crystallization of haplobasaltic, haplodioritic, and related magmas. American Journal of Science, 40, 161–185.Google Scholar

  • Brown, M. (1994) The generation, segregation, ascent and emplacement of granite magma. Earth Science Reviews, 36, 83–130.Google Scholar

  • Burnham, C.W., and Davis, N.F. (1971) The role of H2O in silicate melts; I, P-V-T relations in the system NaAlSi3O8-H2O to 10 kilobars and 1000 °C. American Journal of Science, 270, 54–79.Google Scholar

  • Burnham, C.W., and Davis, N.F. (1974) The role of H2O in silicate melts; II, Thermodynamic and phase relations in the system NaAlSi3O8-H2O to 10 kilobars, 700° to 1100 °C. American Journal of Science, 274, 902–940.Google Scholar

  • Burnham, C.W., Holloway, J.R., and Davis, N.F. (1969) Thermodynamic properties of water to 1,000 °C and 10,000 bars. Special Paper 96, Geological Society of America.

  • Cann, J.R. (1970) Upward movement of granitic magma. Geological Magazine, 107, 335–340.Google Scholar

  • Clemens, J.D. (1984) Water contents of silicic to intermediate magmas. Lithos, 17, 273–287.Google Scholar

  • Clemens, J.D., and Mawer, C.K. (1992) Granitic magma transport by fracture propagation. Tectonophysics, 204, 339–360.Google Scholar

  • Clemens, J.D., and Wall, V.J. (1981) Origin and crystallization of some peraluminous (S-type) granitic magmas. Canadian Mineralogist, 19, 111–131.Google Scholar

  • Collins, W.J., Huang, H.Q., and Jiang, X. (2016) Water-fluxed crustal melting produces Cordilleran batholiths. Geology, 44, 143–146.Google Scholar

  • Daly, R.A. (1914) Igneous Rocks and their Origin, 563 p. McGraw-Hill, New York.Google Scholar

  • Ganguly, J. (2005) Adiabatic decompression and melting of mantle rocks: An irreversible thermodynamic analysis. Geophysical Research Letters, 32, 1–4.Google Scholar

  • Giordano, D., Russell, J.K., and Dingwell, D.B. (2008) Viscosity of magmatic liquids: A model. Earth and Planetary Science Letters, 271, 123–134.Google Scholar

  • Glazner, A.F. (2007) Thermal limitations on incorporation of wall rock into magma. Geology, 35, 319–322.Google Scholar

  • Glazner, A.F., Coleman, D.S., and Mills, R.D. (2015) The volcanic-plutonic connection. In C. Breitkreuz and S. Rocchi, Eds., Physical Geology of Shallow Magmatic Systems: Dykes, Sills, and Laccoliths, p. 1–22. Springer , New York.Google Scholar

  • Hamilton, W., and Myers, W.B. (1967) The nature of batholiths. U.S. Geological Survey Professional Paper, 554-C, 30 p.Google Scholar

  • Harris, P.G., Kennedy, W.Q., and Scarfe, C.M. (1970) Volcanism versus plutonism—the effect of chemical composition. In G. Newall and N. Rast, Eds., Mechanism of Igneous Intrusion, pp. 187–200. Liverpool Geological Society, U.K.Google Scholar

  • Jagoutz, O., and Kelemen, P.B. (2015) Role of arc processes in the formation of continental crust. Annual Review of Earth and Planetary Sciences, 43, 363–404.Google Scholar

  • Johannes, W., and Holtz, F. (1996) Petrogenesis and Experimental Petrology of Granitic Rocks, 335 p. Springer, New York.Google Scholar

  • Lange, R.L., and Carmichael, I.S.E. (1990) Thermodynamic properties of silicate liquids with emphasis on density, thermal expansion and compressibility. Reviews in Mineralogy and Geochemistry, 24, 25–64.Google Scholar

  • Lewis, G.N., Randall, M., Pitzer, K.S., and Brewer, L. (1961) Thermodynamics, 2nd ed., 723 p. McGraw-Hill, New York.Google Scholar

  • Mader, H.M., Llewellin, E.W., and Mueller, S.P. (2013) The rheology of two-phase magmas: A review and analysis. Journal of Volcanology and Geothermal Research, 257, 135–158.Google Scholar

  • McKenzie, D.P., and Bickle, M.J. (1988) The volume and composition of melt generated by extension of the lithosphere. Journal of Petrology, 29, 625–679.Google Scholar

  • Mercer, C.N., Hofstra, A.H., Todorov, T.I., Roberge, J., Burgisser, A., Adams, D.T., and Cosca, M. (2015) Pre-eruptive conditions of the Hideaway Park topaz rhyolite: insights into metal source and evolution of magma parental to the Henderson porphyry molybdenum deposit, Colorado. Journal of Petrology, 56, 645–679.Google Scholar

  • Miller, C.F., and Wark, D.A. (2008) Supervolcanoes and their explosive supereruptions. Elements, 4, 11–15.Google Scholar

  • Müller, A., Kerkhof, A.M. Van Den, Behr, H.J., Kronz, A., and Koch-Müller, M. (2010) The evolution of late—Hercynian granites and rhyolites documented by quartz—a review. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 100, 185–204.Google Scholar

  • Myers, J.S. (1975) Cauldron subsidence and fluidization: mechanisms of intrusion of the Coastal Batholith of Peru into its own volcanic ejecta. Geological Society of America Bulletin, 86, 1209–1220.Google Scholar

  • Patiño-Douce, A.E., and Beard, J.S. (1995) Dehydration-melting of biotite gneiss and quartz amphibolite from 3 to 15 kbar. Journal of Petrology, 36, 707–738.Google Scholar

  • Petford, N., Cruden, A.R., McCaffrey, K.J.W., and Vigneresse, J.-L. (2000) Granite magma formation, transport and emplacement in the Earth’s crust. Nature, 408, 669–673.Google Scholar

  • Pinkerton, H., and Stevenson, R.J. (1992) Methods of determining the rheological properties of magma at sub-liquidus temperatures. Journal of Volcanology and Geothermal Research, 53, 47–66.Google Scholar

  • Pruppacher, H.R., and Klett, J.D. (2010) Cooling of moist air. In J.D. Klett, Ed., Microphysics of Clouds and Precipitation, p. 485–501. Springer, Dordrecht.Google Scholar

  • Ramberg, H. (1971) Temperature changes associated with adiabatic decompression in geological processes. Nature, 234, 539–540.Google Scholar

  • Robie, R.A., Hemingway, B.S., and Fisher, J.R. (1978) Thermodynamic properties of minerals and related substances at 298.15 K and 1 bar (105 Pascals) pressure and at higher temperatures. Bulletin of the U. S. Geological Survey 1452, 456 p.Google Scholar

  • Rosera, J.M., Coleman, D. S., and Stein, H.J. (2013) Re-evaluating genetic models for porphyry Mo mineralization at Questa, New Mexico: Implications for ore deposition following silicic ignimbrite eruption. Geochemistry, Geophysics, Geosystems, 14, 787–805.Google Scholar

  • Rudnick, R.L., and Gao, S. (2013) Composition of the continental crust. In Treatise on Geochemistry: 2nd ed., Vol. 4, pp. 1–51. Elsevier.Google Scholar

  • Sato, H. (2005) Viscosity measurement of subliquidus magmas; 1707 basalt of Fuji Volcano. Journal of Mineralogical and Petrological Sciences, 100, 133–142.Google Scholar

  • Schoene, B., Schaltegger, U., Brack, P., Latkoczy, C., Stracke, A., and Günther, D. (2012) Rates of magma differentiation and emplacement in a ballooning pluton recorded by U-Pb TIMS-TEA, Adamello batholith, Italy. Earth and Planetary Science Letters, 355-356, 162–173.Google Scholar

  • Shane, P., Nairn, I.A., Smith, V.C., Darragh, M., Beggs, K., and Cole, J.W. (2008) Silicic recharge of multiple rhyolite magmas by basaltic intrusion during the 22.6 ka Okareka Eruption Episode, New Zealand. Lithos, 103, 527–549.Google Scholar

  • Singer, B.S., Costa, F., Herrin, J.S., Hildreth, W., and Fierstein, J. (2016) The timing of compositionally-zoned magma reservoirs and mafic “priming” weeks before the 1912 Novarupta-Katmai rhyolite eruption. Earth and Planetary Science Letters, 451, 125–137.Google Scholar

  • Singh, S., Kumar, R., Barley, M.E., and Jain, A.K. (2007) SHRIMP U-Pb ages and depth of emplacement of Ladakh Batholith, Eastern Ladakh, India. Journal of Asian Earth Sciences, 30, 490–503.Google Scholar

  • Sisson, T.W., Ratajeski, K., Hankins, W.B., and Glazner, A.F. (2005) Voluminous granitic magmas from common basaltic sources. Contributions to Mineralogy and Petrology, 148, 635–661.Google Scholar

  • Thomas, J.B., and Watson, E.B. (2012) Application of the Ti-in-quartz thermobarometer to rutile-free systems. Reply to: a comment on: ‘TitaniQ under pressure: the effect of pressure and temperature on the solubility of Ti in quartz’ by Thomas et al. Contributions to Mineralogy and Petrology, 164, 369–374.Google Scholar

  • Tribaudino, M., Angel, R.J., Cámara, F., Nestola, F., Pasqual, D., and Margiolaki, I. (2010) Thermal expansion of plagioclase feldspars. Contributions to Mineralogy and Petrology, 160, 899–908.Google Scholar

  • Tuttle, O.F., and Bowen, N.L. (1958) Origin of granite in the light of experimental studies in the system NaAlSi3O8-KAlSi3O8-SiO2-H2O. Geological Society of America Memoir, 74, 153.Google Scholar

  • Ussler, W., and Glazner, A.F. (1992) Graphical analysis of enthalpy-composition relationships in mixed magmas. Journal of Volcanology and Geothermal Research, 51, 23–40.Google Scholar

  • Waldbaum, D.R. (1971) Temperature changes associated with adiabatic decompression in geological processes. Nature, 232, 545–547.Google Scholar

  • Wark, D.A., Hildreth, W., Spear, F.S., Cherniak, D.J., and Watson, E.B. (2007) Pre-eruption recharge of the Bishop magma system. Geology, 35, 235–238.Google Scholar

  • Waters, L.E., and Lange, R.A. (2017) Why aplites freeze and rhyolites erupt: Controls on the accumulation and eruption of high-SiO2 (eutectic) melts. Geology, 45, 1019–1022.Google Scholar

  • Waters, L.E., Andrews, B.J., and Lange, R.A. (2015) Rapid crystallization of plagioclase phenocrysts in silicic melts during fluid-saturated ascent: phase equilibrium and decompression experiments. Journal of Petrology, 56, 981–1006.Google Scholar

About the article

Received: 2018-12-10

Accepted: 2019-03-01

Published Online: 2019-05-27

Published in Print: 2019-06-26

Citation Information: American Mineralogist, Volume 104, Issue 6, Pages 890–896, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am-2019-6925.

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