Contributions to Mineralogy and Petrology

, Volume 157, Issue 5, pp 609–624 | Cite as

Microlite transfer by disaggregation of mafic inclusions following magma mixing at Soufrière Hills volcano, Montserrat

  • Madeleine C. S. Humphreys
  • Thomas Christopher
  • Vicky Hards
Original Paper


The Soufrière Hills volcano on Montserrat has for the past 12 years been erupting andesite with basaltic to basaltic–andesite inclusions. The andesite contains a wide variety of phenocryst textures and strongly zoned microlites. Analysis of minor elements in both phenocrysts and microlites allows us to put detailed constraints on their origins. Compositions of clinopyroxene, from overgrowth rims on quartz and orthopyroxene and coarse-grained breakdown rims on hornblende, are identical to those from the mafic inclusions, indicating that these rims form during interaction with mafic magma. In contrast, resorbed quartz and reversely zoned orthopyroxenes form during heating. Microlites of plagioclase and orthopyroxene are chemically distinct from the phenocrysts, being enriched in Fe and Mg, and Al and Ca respectively. However, microlites of plagioclase, orthopyroxene and clinopyroxene are indistinguishable from the compositions of these phases in the mafic inclusions. We infer that the inclusions disaggregated under conditions of high shear stress during ascent in the conduit, transferring mafic material into the andesite groundmass. The mafic component of the system is therefore greater than previously thought. The presence of mafic-derived microlites in the andesite groundmass also means that care must be taken when using this as a starting material for phase equilibrium experiments.


Magma mixing Mafic inclusions Microlites Hybridisation Disaggregation Soufrière Hills volcano Montserrat 


  1. Allègre CJ, Provost A, Jaupart C (1981) Oscillatory zoning: a pathological case of crystal growth. Nature 294:223–228. doi:10.1038/294223a0 CrossRefGoogle Scholar
  2. Anderson AT (1976) Magma mixing: petrological process and volcanological tool. J Volcanol Geotherm Res 1:3–33. doi:10.1016/0377-0273(76)90016-0 CrossRefGoogle Scholar
  3. Andersen DJ, Lindsley DH, Davidson PM (1993) QUILF: A Pascal program to assess equilibria among Fe–Mg–Ti oxides, pyroxenes, olivine and quartz. Comput Geosci 19:1333–1350. doi:10.1016/0098-3004(93)90033-2 CrossRefGoogle Scholar
  4. Arculus RJ (1976) Geology and geochemistry of the alkali basalt-andesite association of Grenada, Lesser Antilles island arc. Geol Soc Am Bull 87:612–624. doi :10.1130/0016-7606(1976)87<612:GAGOTA>2.0.CO;2CrossRefGoogle Scholar
  5. Arculus RJ, Wills KJA (1980) The petrology of plutonic blocks and inclusions from the Lesser Antilles island arc. J Petrol 21:743–799Google Scholar
  6. Bachmann O, Dungan MA (2002) Temperature-induced Al-zoning in hornblendes of the Fish Canyon magma, Colorado. Am Mineral 87:1062–1076Google Scholar
  7. Bacon CR (1986) Magmatic inclusions in silicic and intermediate volcanic rocks. J Geophys Res 91:6091–6112. doi:10.1029/JB091iB06p06091 CrossRefGoogle Scholar
  8. Bacon CR (1989) Crystallization of accessory phases in magmas by local saturation adjacent to phenocrysts. Geochim Cosmochim Acta 53:1055–1066. doi:10.1016/0016-7037(89)90210-X CrossRefGoogle Scholar
  9. Barclay J, Rutherford MJ, Carroll MR et al (1998) Experimental phase equilibria constraints on pre-eruptive storage conditions of the Soufrière Hills magma. Geophys Res Lett 25:3437–3440. doi:10.1029/98GL00856 CrossRefGoogle Scholar
  10. Beattie P (1993) Olivine-melt and orthopyroxene-melt equilibria. Contrib Mineral Petrol 115:103–111. doi:10.1007/BF00712982 CrossRefGoogle Scholar
  11. Bindeman IN, Davis AM, Drake MJ (1998) Ion microprobe study of plagioclase-basalt partition experiments at natural concentration levels of trace elements. Geochim Cosmochim Acta 62:1175–1193. doi:10.1016/S0016-7037(98)00047-7 CrossRefGoogle Scholar
  12. Blake S, Fink JH (2000) On the deformation and freezing of enclaves during magma mixing. J Volcanol Geotherm Res 95:1–8. doi:10.1016/S0377-0273(99)00129-8 CrossRefGoogle Scholar
  13. Blundy JD, Sparks RSJ (1992) Petrogenesis of mafic inclusions in granitoids of the Adamello Massif, Italy. J Petrol 33:1039–1104Google Scholar
  14. Blundy J, Cashman K, Humphreys M (2006) Magma heating by decompression-driven crystallization beneath andesite volcanoes. Nature 443:76–80. doi:10.1038/nature05100 CrossRefGoogle Scholar
  15. Bottinga Y, Kudo A, Weill D (1966) Some observations on oscillatory zoning and crystallization of magmatic plagioclase. Am Mineral 51:792–806Google Scholar
  16. Browne BL, Eichelberger JC, Patina LC et al (2006) Generation of porphyritic and equigranular mafic enclaves during magma recharge events at Unzen Volcano, Japan. J Petrol 47:301–328. doi:10.1093/petrology/egi076 CrossRefGoogle Scholar
  17. Buckley VJE, Sparks RSJ, Wood BJ (2006) Hornblende dehydration reactions during magma ascent at Soufrière Hills Volcano, Montserrat. Contrib Mineral Petrol 151:121–140. doi:10.1007/s00410-005-0060-5 CrossRefGoogle Scholar
  18. Cashman KV (1992) Groundmass crystallization of Mount St. Helens dacite, 1980–1986: A tool for interpreting shallow magmatic processes. Contrib Mineral Petrol 109:431–449. doi:10.1007/BF00306547 CrossRefGoogle Scholar
  19. Clynne MA (1999) A complex magma mixing origin for rocks erupted in 1915, Lassen Peak, California. J Petrol 40:105–132. doi:10.1093/petrology/40.1.105 CrossRefGoogle Scholar
  20. Couch S, Sparks RSJ, Carroll MR (2001) Mineral disequilibrium in lavas explained by convective self-mixing in open magma chambers. Nature 411:1037–1039. doi:10.1038/35082540 CrossRefGoogle Scholar
  21. Couch S, Harford CL, Sparks RSJ, Carroll MR (2003a) Experimental constraints on the conditions of formation of highly calcic plagioclase microlites at the Soufrière Hills Volcano, Montserrat. J Petrol 44:1455–1475. doi:10.1093/petrology/44.8.1455 CrossRefGoogle Scholar
  22. Couch S, Sparks RSJ, Carroll MR (2003b) The kinetics of degassing-induced crystallization at Soufrière Hills Volcano, Montserrat. J Petrol 44:1477–1502. doi:10.1093/petrology/44.8.1477 CrossRefGoogle Scholar
  23. Devine JD, Murphy MD, Rutherford MJ et al (1998) Petrologic evidence for pre-eruptive pressure-temperature conditions and recent reheating, of andesitic magma erupting at the Soufrière Hills Volcano, Montserrat, W.I. Geophys Res Lett 25:3669–3672. doi:10.1029/98GL01330 CrossRefGoogle Scholar
  24. Devine JD, Rutherford MJ, Norton GE et al (2003) Magma storage region processes inferred from geochemistry of Fe–Ti oxides in andesitic magma, Soufriere Hills Volcano, Montserrat, W.I. J Petrol 44:1375–1400. doi:10.1093/petrology/44.8.1375 CrossRefGoogle Scholar
  25. Eichelberger JC (1978) Andesitic volcanism and crustal evolution. Nature 275:21–27. doi:10.1038/275021a0 CrossRefGoogle Scholar
  26. Eichelberger JC (1980) Vesiculation of mafic magma during replenishment of silicic magma chambers. Nature 288:446–450. doi:10.1038/288446a0 CrossRefGoogle Scholar
  27. Feeley TC, Dungan MA (1996) Compositional and dynamic controls on mafic-silicic magma interactions at continental arc volcanoes: evidence from Cordòn El Guadal, Tatara, San Pedro Complex, Chile. J Petrol 37:1547–1577. doi:10.1093/petrology/37.6.1547 CrossRefGoogle Scholar
  28. Frost BR, Lindsley DH (1991) Occurrence of iron–titanium oxides in igneous rocks. Rev Mineral 25:433–468Google Scholar
  29. Garcia MO, Jacobson SS (1979) Crystal clots, amphibole fractionation and the evolution of calc-alkaline magmas. Contrib Mineral Petrol 69:319–327. doi:10.1007/BF00372257 CrossRefGoogle Scholar
  30. Ginibre C, Wörner G, Kronz A (2002) Minor- and trace-element zoning in plagioclase: implications for magma chamber processes at Parinacota Volcano, northern Chile. Contrib Mineral Petrol 143:300–315Google Scholar
  31. Hammond PA, Taylor LA (1982) The ilmenite/titano-magnetite assemblage: kinetics of re-equilibration. Earth Planet Sci Lett 61:143–150. doi:10.1016/0012-821X(82)90047-4 CrossRefGoogle Scholar
  32. Holland T, Blundy J (1994) Non-ideal interactions in calcic amphiboles and their bearing on amphibole-plagioclase thermometry. Contrib Mineral Petrol 116:433–447. doi:10.1007/BF00310910 CrossRefGoogle Scholar
  33. Leake BE, Wooley AR, Arps CES (1997) Nomenclature of amphiboles: Report of the subcommittee on amphiboles of the International Mineralogical Association, Commission on new minerals and mineral names. Can Mineral 35:219–246Google Scholar
  34. Lindsley DH (1983) Pyroxene thermometry. Am Mineral 68:477–493Google Scholar
  35. MacGregor AG (1938) The Royal Society expedition to Montserrat, B.W.I. The volcanic history and petrology of Montserrat, with observations on Mt Pele, in Martinique. Philos Trans R Soc Lond 229:1–90. doi:10.1098/rstb.1938.0002 CrossRefGoogle Scholar
  36. Martel C, Radadi Ali A, Poussineau S et al (2006) Basalt-inherited microlites in silicic magmas: evidence from Mount Pelée (Martinique, French West Indies). Geology 34:905–908. doi:10.1130/G22672A.1 CrossRefGoogle Scholar
  37. Martin VM, Pyle DM, Holness MB (2006) The role of crystal frameworks in the preservation of enclaves during magma mixing. Earth Planet Sci Lett 248:787–799. doi:10.1016/j.epsl.2006.06.030 CrossRefGoogle Scholar
  38. Melnik O, Sparks RSJ (1999) Nonlinear dynamics of lava dome extrusion. Nature 402:37–41. doi:10.1038/46950 CrossRefGoogle Scholar
  39. Murphy MD, Sparks RSJ, Barclay J et al (2000) Remobilization of andesite magma by intrusion of mafic magma at the Soufrière Hills Volcano, Montserrat, West Indies. J Petrol 41:21–42. doi:10.1093/petrology/41.1.21 CrossRefGoogle Scholar
  40. Nelson ST, Montana A (1992) Sieve-textured plagioclase in volcanic rocks produced by rapid decompression. Am Mineral 77:1242–1249Google Scholar
  41. Perret F (1939) The volcano-seismic crisis at Montserrat 1933–1937, vol 512. Carnegie Institue of Washington Publication, Washington, 76 ppGoogle Scholar
  42. Phinney WC (1992) Partition coefficients for iron between plagioclase and basalt as a function of oxygen fugacity: implications for Archaean and lunar anorthosites. Geochim Cosmochim Acta 56:1885–1895. doi:10.1016/0016-7037(92)90318-D CrossRefGoogle Scholar
  43. Pichavant M, Costa F, Burgisser A et al (2007) Equilibration scales in silicic to intermediate magmas: implications for experimental studies. J Petrol 48:1955–1972. doi:10.1093/petrology/egm045 CrossRefGoogle Scholar
  44. Plechov PY, Tsai AE, Shcherbakov VD et al (2008a) Opacitization conditions of hornblende in Bezymyannyi Volcano andesites (March 30, 1956 eruption). Petrol 16:19–35Google Scholar
  45. Plechov PY, Fomin IS, Melnik OE et al (2008b) Evolution of melt composition during intrusion of basalts into a silicic magma chamber. Mosc Univ Geol Bull 63:247–257. doi:10.3103/S0145875208040054 CrossRefGoogle Scholar
  46. Ruprecht P, Wörner G (2007) Variable regimes in magma systems documented in plagioclase zoning patterns: El Misti stratovolcano and Andahua monogenetic cones. J Volcanol Geotherm Res 165:142–162. doi:10.1016/j.jvolgeores.2007.06.002 CrossRefGoogle Scholar
  47. 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. doi:10.1093/petrology/44.8.1433 CrossRefGoogle Scholar
  48. Rutherford MJ, Hill PM (1993) Magma ascent rates from amphibole breakdown: an experimental study applied to the 1980–1986 Mount St Helens eruptions. J Geophys Res 98:19667–19685. doi:10.1029/93JB01613 CrossRefGoogle Scholar
  49. Sato H, Holtz F, Behrens H, Botcharnikov R, Nakada S (2005) Experimental petrology of the 1991–1995 Unzen dacite, Japan. Part II: Cl/OH partitioning between hornblende and melt and its implications for the origin of oscillatory zoning of hornblende phenocrysts. J Petrol 46:339–354. doi:10.1093/petrology/egh078 CrossRefGoogle Scholar
  50. Scarfe CM, Fuji T (1987) Petrology of crystal clots in the pumice of Mount St. Helens’ March 19, 1982 eruption: significant role of Fe–Ti oxide crystallisation. J Volcanol Geotherm Res 34:1–14. doi:10.1016/0377-0273(87)90088-6 CrossRefGoogle Scholar
  51. Schumacher JC (1997) The estimation of the proportion of ferric iron in the electron-microprobe analysis of amphiboles. Can Mineral 35:238–246Google Scholar
  52. Sepp B, Kunzman T (2001) The stability of clinopyroxene in the system CaO–MgO–SiO2–TiO2 (CMST). Am Mineral 86:265–270Google Scholar
  53. Shepherd JB, Tomblin JF, Woo DA (1971) Volcano-seismic crisis in Montserrat, West Indies, 1966–1967. Bull Volcanol 35:143–163. doi:10.1007/BF02596813 CrossRefGoogle Scholar
  54. Singer BS, Dungan MA, Layne GD (1995) Textures and Sr, Ba, Mg, Fe, K, and Ti compositional profiles in volcanic plagioclase: Clues to the dynamics of calc-alkaline magma chambers. Am Mineral 80:776–798Google Scholar
  55. Sparks RSJ, Marshall LA (1986) Thermal and mechanical constraints on mixing between mafic and silicic magmas. J Volcanol Geotherm Res 29:99–124. doi:10.1016/0377-0273(86)90041-7 CrossRefGoogle Scholar
  56. Sparks RSJ, Murphy MD, Lejeune AM et al (2000) Control on the emplacement of the andesite lava dome of the Soufrière Hills Volcano, Montserrat by degassing-induced crystallization. Terra Nova 12:14–20. doi:10.1046/j.1365-3121.2000.00267.x CrossRefGoogle Scholar
  57. Stewart DC (1975) Crystal clots in calc-alkaline andesites as breakdown products of high-Al amphiboles. Contrib Mineral Petrol 53:195–204. doi:10.1007/BF00372604 CrossRefGoogle Scholar
  58. Stormer JC (1983) The effects of recalculation on estimates of temperature and oxygen fugacity from analyses of multi-component iron–itanium oxides. Am Mineral 66:586–594Google Scholar
  59. Venezky DY, Rutherford MJ (1999) Petrology and Fe–Ti oxide re-equilibration of the 1991 Mount Unzen mixed magma. J Volcanol Geotherm Res 89:213–230. doi:10.1016/S0377-0273(98)00133-4 CrossRefGoogle Scholar
  60. Wilke M, Behrens H (1999) The dependence of the partitioning of iron and europium between plagioclase and hydrous tonalitic melt on oxygen fugacity. Contrib Mineral Petrol 137:102–114. doi:10.1007/s004100050585 CrossRefGoogle Scholar
  61. Zellmer GF, Hawkesworth CJ, Sparks RSJ et al (2003a) Geochemical evolution of the Soufrière Hills Volcano, Montserrat, Lesser Antilles volcanic arc. J Petrol 44:1349–1374. doi:10.1093/petrology/44.8.1349 CrossRefGoogle Scholar
  62. Zellmer GF, Sparks RSJ, Hawkesworth CJ et al (2003b) Magma emplacement and remobilization timescales beneath Montserrat: insights from Sr and Ba zonation in plagioclase phenocrysts. J Petrol 44:1413–1431. doi:10.1093/petrology/44.8.1413 CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Madeleine C. S. Humphreys
    • 1
  • Thomas Christopher
    • 2
  • Vicky Hards
    • 2
    • 3
  1. 1.Department of Earth SciencesUniversity of CambridgeCambridgeUK
  2. 2.Montserrat Volcano ObservatoryFlemmings, MontserratWest Indies
  3. 3.British Geological SurveyNottinghamUK

Personalised recommendations