Abstract
The eruption of Soufrière Hills Volcano, Montserrat, has been ongoing since 1995. The volcano is erupting a crystal-rich hornblende-plagioclase andesite with ubiquitous mafic inclusions, indicating mixing with mafic magma. This mafic magma is thought to be the driving force of the eruption, supplying heat and volatiles to the andesite resident in the magma chamber. As well as producing macroscopic mafic inclusions, the magma mixing process involves incorporation of phenocrysts from the andesite into the mafic magma. These inherited phenocrysts show clear disequilibrium textures (e.g. sieved plagioclase rims and thermal breakdown rims on hornblende). Approximately 25 % of all phenocrysts in the andesite show these textures, indicating very extensive mass transfer between the two magma types. Fragments of mafic inclusions down to sub-mm scale are found in the andesite, together with mafic crystal clusters, which are commonly found adhered to the rims of phenocrysts with disequilibrium features. Mineral chemistry also points to the transfer of microlites or microphenocrysts, initially formed in the mafic inclusions, into the andesite. This combined evidence suggests that some of the mafic inclusions disaggregate during mingling and/or ascent, possibly due to shearing, and raises the question: What proportion of the andesite ‘groundmass’ actually originated in the mafic inclusions, and thus, what is the true amount of mafic magma in the magmatic system? We present a new method for quantifying the relative proportions of groundmass plagioclase derived from mafic and andesitic magma, based on analysis of back-scattered electron images of the groundmass. Preliminary results indicate that approximately 16 % of all groundmass plagioclase belongs genetically to the mafic inclusions. Together with the crystal clusters, disequilibrium phenocryst textures and mm-scale inclusions, there is a ‘cryptic’ mafic component in the andesite of approximately 6 % by volume. This is significant compared with the proportion of macroscopic mafic inclusions (typically ~ 1–5 %). The new method has the potential to allow tracking of the mafic fraction through time and thus to yield further insights into magma hybridisation processes.
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References
Bacon CR (1986) Magmatic inclusions in silicic and intermediate volcanic rocks. J Geophys Res 91:6091–6112
Barclay J, Herd RA, Edwards BR, Christopher T, Kiddle EJ, Plail M, Donovan A (2010) Caught in the act: implications for the increasing abundance of mafic enclaves during the recent eruptive episodes of the Soufriere Hills Volcano, Montserrat. Geophys Res Lett 37:L00E09
Baxter PJ, Bonadonna C, Dupree R, Hards VL, Kohn SC, Murphy MD, Nichols A, Nicholson RA, Norton G, Searl A, Sparks RSJ, Vickers BP (1999) Cristobalite in volcanic ash of the Soufrière Hills Volcano, Montserrat, British West Indies. Science 283:1142–1145
Blundy JD, Sparks RSJ (1992) Petrogenesis of mafic inclusions in granitoids of the Adamello Massif, Italy. J Petrol 35:1039–1104
Browne BL, Eichelberger JC, Patino LC, Vogel TA, Dehn J, Uto K, Hoshizumi H (2006) Generation of porphyritic and equigranular mafic enclaves during magma recharge events at Unzen Volcano, Japan. J Petrol 47:301–328
Cashman KV (1992) Groundmass crystallisation of Mount St. Helens dacite, 1980–1986: a tool for interpreting shallow magmatic processes. Contrib Mineral Petrol 109:431–449
Clynne MA (1999) A complex magma mixing origin for rocks erupted in 1915, Lassen Peak, California. J Petrol 40:105–132
Coombs ML, Eichelberger JC, Rutherford MJ (2002) Experimental and textural constraints on mafic enclave formation in volcanic rocks. J Volcanol Geotherm Res 119:125–144
Costa A (2005) Viscosity of high crystal content melts: dependence on solid fraction. Geophys Res Letters 32:L22308
Costa F, Chakraborty S, Dohmen R (2003) Diffusion coupling between trace and major elements and a model for calculation of magma residence times using plagioclase. Geochim Cosmochim Acta 67:2189–2200
Couch S, Harford CL, Sparks RSJ, Carroll MR (2003) Experimental constraints on the conditions of formation of highly calcic plagioclase microlites at the Soufrière Hills Volcano, Montserrat. J Petrol 44:1455–1475
D’Lemos RS (1996) Mixing between granitic and dioritic crystal mushes, Guernsey, Channel Islands, UK. Lithos 38:233–257
Devine JD, Murphy MD, Rutherford MJ, Barclay J, Sparks RSJ, Carroll MR, Young SR, Gardner JE (1998) Petrologic evidence for pre-eruptive pressure-temperature conditions, and recent reheating, of andesite magma erupting at the Soufrière Hills Volcano, Montserrat, WI. Geophys Res Lett 25:3669–3672
Devine JD, Rutherford MJ, Norton GE, Young SR (2003) Magma storage region processes inferred from geochemistry of Fe-Ti oxides in andesitic magma, Soufrière Hills Volcano, Montserrat, WI. J Petrol 44:1375–1400
Druitt TH, Costa F, Deloule E, Dungan M, Scaillet B (2012) Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano. Nature 482:77–80
Edmonds M, Aiuppa A, Humphreys M, Moretti R, Giudice G, Martin RS, Herd RA, Christopher T (2010) Excess volatiles supplied by mingling of mafic magma at an andesite arc volcano. Geochem Geophys Geosys 11:Q04005
Eichelberger JC (1978) Andesitic volcanism and crustal evolution. Nature 275:21–24
Eichelberger JC, Chertkoff DG, Dreher ST, Nye CJ (2000) Magmas in collision: rethinking chemical zonation in silicic magmas. Geology 28:603–606
Elsworth D, Mattioli G, Taron J, Voight B, Herd R (2008) Implications of magma transfer between multiple reservoirs on eruption cycling. Science 322:246–248
Feeley TC, Dungan MA (1996) Compositional and dynamic controls on mafic-silicic magma interactions at continental arc volcanoes: evidence from Cordón El Guadal, Tatara-San Pedro complex, Chile. J Petrol 37:1547–1577
Feeley TC, Wilson LF, Underwood SJ (2008) Distribution and compositions of magmatic inclusions in the Mount Helen dome Lassen Volcanic Center, California: insights into magma chamber processes. Lithos 106:173–189
Ghiorso MS, Sack RO (1995) Chemical mass transfer in magmatic processes. IV. A revised and internally consistent thermodynamic model for the Interpolation and Extrapolation of Liquid-Solid equilibria in magmatic systems at elevated temperatures and pressures. Contrib Miner Petrol 119:197–212
Ginibre C, Kronz A, Wörner G (2002) High-resolution quantitative imaging of plagioclase composition using accumulated backscattered electron images: new constraints on oscillatory zoning. Contrib Mineral Petrol 142:436–448
Harford CL, Pringle MS, Sparks RSJ, Young SR (2002) The volcanic evolution of Montserrat using 40Ar/39Ar geochronology. In: Druitt TH, Kokelaar BP (eds) 2002. The eruption of Soufriere Hills Volcano, Montserrat, from 1995 to 1999. Geological Society, London, vol 21, pp 93–113
Heiken G, Eichelberger JC (1980) Eruptions at Chaos Crags, Lassen Volcanic National Park, California. J Volcanol Geotherm Res 7:443–481
Higgins MD (1994) Numerical modelling of crystal shapes in thin sections: estimation of crystal habit and true size. Am Mineral 79:113–119
Humphreys MCS, Blundy JD, Sparks RSJ (2006) Magma evolution and open-system processes at Shiveluch Volcano: insights from phenocryst zoning. J Petrol 47:2303–2334
Humphreys MCS, Christopher T, Hards V (2009a) Microlite transfer by disaggregation of mafic inclusions following magma mixing at Soufrière Hills volcano, Montserrat. Contrib Mineral Petrol 157:609–624
Humphreys MCS, Edmonds M, Christopher T, Hards V (2009b) Chlorine variations in the magma of Soufrière Hills Volcano, Montserrat: insights from Cl in hornblende and melt inclusions. Geochim Cosmochim Acta 73:5693–5708
Humphreys MCS, Edmonds M, Christopher T, Hards V (2010) Magma hybridisation and diffusive exchange recorded in heterogeneous glasses from Soufrière Hills Volcano, Montserrat. Geophys Res Lett 37:L00E06
Jerram DA, Higgins MD (2007) 3D analysis of rock textures: quantifying igneous microstructures. Elements 3:239–245
Kent AJR, Darr C, Koleszar AM, Salisbury MJ, Cooper KM (2010) Preferential eruption of andesitic magmas through recharge filtering. Nat Geosci 3:631–636
Kiddle EJ, Edwards BR, Loughlin SC, Petterson M, Sparks RSJ, Voight B (2010) Crustal structure beneath Montserrat, Lesser Antilles, constrained by xenoliths, seismic velocity structure and petrology. Geophys Res Lett 37:L00E11
Komorowski J-C, Legendre Y, Christopher T, Bernstein M, Stewart R, Joseph E, Fournier N, Chardot L, Finizola A, Wadge G, Syers R, Williams C, Bass V (2010) Insights into processes and deposits of hazardous vulcanian explosions at Soufrière Hills Volcano during 2008 and 2009 (Montserrat, West Indies). Geophys Res Lett 37:L00E19
Kouchi A, Sunagawa I (1985) A model for mixing basaltic and dacitic magmas as deduced from experimental data. Contrib Mineral Petrol 89:17–23
Macdonald R, Hawkesworth CJ, Heath E (2000) The Lesser Antilles volcanic chain: a study in arc magmatism. Earth Sci Rev 49:1–76
Martel C, Radadi Ali A, Poussineau S, Gourgaud A, Pichavant M (2006) Basalt-inherited microlites in silicic magmas: evidence from Mount Pelée (Martinique, French West Indies). Geology 34:905–908
McLeod GW, Dempster TJ, Faithfull JW (2011) Deciphering magma-mixing processes using zoned titanite from the Ross of Mull granite, Scotland. J Petrol 52:55–82
Melnik O, Sparks RSJ (1999) Nonlinear dynamics of lava dome extrusion. Nature 402:37–41
Mortazavi M, Sparks RSJ (2004) Origin of rhyolite and rhyodacite lavas and associated mafic inclusions of Cape Akrotiri, Santorini: the role of wet basalt in generating calcalkaline silicic magmas. Contrib Mineral Petrol 146:397–413
Murphy MD, Sparks RSJ, Barclay J, Carroll MR, Lejeune A-M, Brewer TS, Macdonald R, Black S, Young SR (1998) The role of magma mixing in triggering the current eruption at the Soufrière Hills volcano, Montserrat, West Indies. Geophys Res Lett 25:3433–3436
Murphy MD, Sparks RSJ, Barclay J, Carroll MR, Brewer TS (2000) Remobilisation of andesite magma by intrusion of mafic magma at the Soufrière Hills Volcano, Montserrat, West Indies. J Petrol 41:21–42
Nakada S, Bacon CR, Gartner AE (1994) Origin of phenocrysts and compositional diversity in pre-Mazama rhyodacite lavas, Crater Lake, Oregon. J Petrol 35:127–162
Plail M, Barclay J, Humphreys MCS, Edmonds M, Herd R, Christopher T (2012) Characterisation of mafic enclaves in the erupted products of Soufrière Hills Volcano, Montserrat 1995–2010. Geol Soc Lon Memoir (accepted)
Plechov PYu, Tsai AE, Shcherbakov VD, Dirksen OV (2008) Opacitization conditions of hornblende in Bezymyannyi Volcano andesites (March 30, 1956 eruption). Petrology 16:19–35
Rasband WS, Image J (1997–2011) U. S. National Institutes of Health, Bethesda, Maryland, USA, http://imagej.nih.gov/ij/
Rutherford MJ, Devine JD (2003) Magmatic conditions and magma ascent as indicated by hornblende phase equilibria and reactions in the 1995–2002 Soufrière Hills magma. J Petrol 44:1433–1454
Ryan GA, Loughlin SC, James MR, Jones LD, Calder ES, Christopher T, Strutt MH, Wadge G (2010) Growth of the lava dome and extrusion rates at Soufrière Hills Volcano, Montserrat, West Indies: 2005–2008. Geophys Res Lett 37:L00E08
R Development Core Team (2010) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN 3-900051-07-0, URL http://www.R-project.org/
Sato H, Nakada S, Fujii T, Nakamura M, Suzuki-Kamata K (1999) Groundmass pargasite in the 1991–1995 dacite of Unzen volcano: phase stability experiments and volcanological implications. J Volcanol Geotherm Res 89:197–212
Snyder et al (1997) Practical HPLC method development. Wiley, NY
Sparks RSJ, Marshall LA (1986) Thermal and mechanical constraints on mixing between mafic and silicic magmas. J Volcanol Geotherm Res 29:99–124
Sparks RSJ, Sigurdsson H, Wilson L (1977) Magma mixing: a mechanism for triggering acid explosive eruptions. Nature 267:315–318
Sparks RSJ, Murphy MD, Lejeune AM, Watts RB, Barclay J, Young SR (2000) Control on the emplacement of the andesite lava dome of the Soufrière Hills volcano, Montserrat by degassing-induced crystallisation. Terra Nova 12:14–20
Stout CM, Hammersley L, Clynne MA (2007) Field measurements of mafic enclave population density at Chaos Crags, Lassen Volcanic National Park, CA and implications for magma mixing. 103rd Annual meeting of the Geological Society of America, Cordilleran Section, abstract no. 30–12
Tepley FJ, Davidson JP, Clynne MA (1999) Magmatic interactions as reorded in plagioclase phenocrysts of Chaos Crags, Lassen Volcanic Center, California. J Petrol 40:787–806
Wadge G, Isaacs MC (1988) Mapping the volcanic hazards from Soufriere Hills Volcano, Montserrat, West Indies using an image processor. J Geol Soc Lon 145:541–551
Wadge G, Herd R, Ryan G, Calder ES, Komorowski J-C (2010) Lava production at Soufrière Hills Volcano, Montserrat: 1995–2009. Geophys Res Lett 37:L00E03
Wiebe RA (1987) Rupture and inflation of a basic magma chamber by silicic liquid. Nature 326:69–71
Zellmer GF, Hawkesworth CJ, Sparks RSJ, Thomas LE, Harford CL, Brewer TS, Loughlin SC (2003) Geochemical evolution of the Soufrière Hills volcano, Montserrat, Lesser Antilles volcanic arc. J Petrol 44:1349–1374
Acknowledgments
We acknowledge useful discussions with Kathy Cashman, Dan Morgan, Steve Sparks, Geoff Wadge, Paul Cole, Richard Katz and Vicki Smith, who also provided analytical support. MCSH was supported by a Royal Society University Research Fellowship. ME acknowledges support from COMET+, the NERC National Centre for Earth Observation. MP was supported by a NERC studentship. We acknowledge funding from NERC grant NE/I008543/1. Useful reviews were received from Mike Clynne and Pavel Plechov, which, together with suggestions from editor Jon Blundy, helped improve the manuscript.
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Humphreys, M.C.S., Edmonds, M., Plail, M. et al. A new method to quantify the real supply of mafic components to a hybrid andesite. Contrib Mineral Petrol 165, 191–215 (2013). https://doi.org/10.1007/s00410-012-0805-x
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DOI: https://doi.org/10.1007/s00410-012-0805-x