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The Highwood Mountains potassic igneous province, Montana: mineral fractionation trends and magmatic processes revisited

Published online by Cambridge University Press:  05 July 2018

C. M. B. Henderson ,
F. R. Richardson  and
J. M. Charnock
C. M. B. Henderson*
Affiliation:
School of Earth, Atmospheric and Environmental Sciences (SEAES), Williamson Building, University of Manchester M13 9PL, UK Accelerator Science and Technology Centre (ASTeC), Daresbury Laboratory, Science and Technology Facilities Council, Warrington WA4 4AD, UK
F. R. Richardson
Affiliation:
School of Earth, Atmospheric and Environmental Sciences (SEAES), Williamson Building, University of Manchester M13 9PL, UK
J. M. Charnock
Affiliation:
School of Earth, Atmospheric and Environmental Sciences (SEAES), Williamson Building, University of Manchester M13 9PL, UK
*
*E-mail: michael.henderson@manchester.ac.uk
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Abstract

Potassium-rich mafic dykes and lavas from the Highwood Mountains Igneous Province, USA were studied by electron-microprobe and bulk-rock analysis. For the mafic phonolites, compositional trends for olivine and augite phenocrysts and groundmass biotite, alkali feldspar and titanomagnetites are presented and substitution mechanisms discussed. Phenocrysts of biotite and augite in the minettes are also characterized, together with groundmass alkali feldspar and titanomagnetite. The alkali feldspars and biotites are commonly enriched in Ba. Olivine, clinopyroxene and biotite phenocrysts are generally quite magnesium-rich, which is consistent with the primitive natures of the least evolved rocks.

Bulk-rock major-element compositions are combined with modal and microprobe data for the principal phenocrysts to calculate model residual liquid compositions for mafic phonolites, minettes and a syenitic rock. On the basis of phase-equilibria, it is suggested that the main controls of differentiation are polybaric involving crystallization during transport of primary magmas from the mantle for the minettes, and low-pressure differentiation for the mafic phonolites. Whereas magma mixing might have contributed to petrogenesis, many of the disequilibrium features exhibited by clinopyroxene and biotite phenocrysts can also be attributed to pre-existing phenocrysts undergoing decompression melting during magma uprise from its mantle source, followed by rapid crystal growth and episodic volatile loss in sub-volcanic magma chambers.

Keywords

petrogenesis of K-rich basaltic rocksprimary biotite fractionationdecompression meltingmagma mixingphase equilibria
Type
Research Article
Information
Mineralogical Magazine , Volume 76 , Issue 4 , August 2012 , pp. 1005 - 1051
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2012

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References

Anderson, A.T. (1976) Magma mixing: petrological process and volcanological tool. Journal of Volcanology and Geothermal Research, 1, 3–33.CrossRefGoogle Scholar
Baker, D.R. and Eggler, D.H. (1987) Compositions of anhydrous and hydrous melts coexisting with plagio-clase, augite and olivine or low-Ca pyroxene from 1 atm to 8 kbar: application to the Aleutian volcanic centre of Atka. American Mineralogist, 72, 12–28.Google Scholar
Barksdale, J.D. (1937) The Shonkin Sag laccolith. American Journal of Science, 33, 321–359.CrossRefGoogle Scholar
Barton, M. and Hamilton, D.L. (1979) The melting relationships of a madupite from the Leucite Hills, Wyoming. Contributions to Mineralogy and Petrology, 69, 133–142.Google Scholar
Barton, M. and Hamilton, D.L. (1982) Water-under-saturated melting experiments bearing upon the origin of potassium-rich magmas. Mineralogical Magazine, 45, 267–278.CrossRefGoogle Scholar
Bhattachargi, S. (1967) Mechanics of flow differentia-tion in ultramafic and mafic sills. Journal of Geology, 75, 101–112.CrossRefGoogle Scholar
Blundy, J. and Cashman, K. (2008) Petrologic reconstruction of magmatic system variables and processes. Pp. 179–239 in: Minerals, Inclusions and Volcanic Processes (K.D. Putirka and FJ. Tepley III, editors). Reviews in Mineralogy and Geochemistry, 69. Mineralogical Society of America, Washington DC and the Geochemical Society, St. Louis, Missouri, USA.Google Scholar
Buie, B.F. (1941) Igneous rocks of the Highwood Mountains Montana. Part III. Dikes and related intrusives. Bulletin of the Geological Society of America, 52, 1753–1808.CrossRefGoogle Scholar
Delaney, J.S., Smith, J.V., Carswell, D.A. and Dawson, J.B. (1980) Chemistry of micas from kimberlites and xenoliths—II. Primary-and secondary-textured micas from peridotite xenoliths. Geochimica et Cosmochimica Acta, 44, 857–872.CrossRefGoogle Scholar
Droop, G.T.R. (1987) A general equation for estimating Fe+ concentrations in ferromagnesian silicates and oxides from microprobe analyses, using stoichio-metric criteria. Mineralogical Magazine, 51, 431–435.CrossRefGoogle Scholar
Edgar, A.D. (1992) Barium-rich phlogopite and biotite from some Quaternary alkali mafic lavas, West Eifel, Germany. European Journal of Mineralogy, 4, 321–330.CrossRefGoogle Scholar
Esperanca, S and Holloway, J.R. (1987) On the origin of some mica-lamprophyres: experimental evidence from a mafic minette. Contributions to Mineralogy and Petrology, 95, 207–216.Google Scholar
Fenn, P.M. (1977) The nucleation and growth of alkali feldspars from hydrous melts. The Canadian Mineralogist, 15, 135–161.Google Scholar
Fleet, M.E. (editor) (2003) Sheet Silicates: Micas, volume 3A, second edition of Deer, Howie and Zussman, Rock-Forming Minerals. The Geological Society of London, London, 758 pp.Google Scholar
Frey, H.M. and Lange, R.A. (2010) Phenocryst complexity in andesites and dacites from the Tequila volcanic field, Mexico: resolving the effects of degassin. vs. magma mixing. Contributions to Mineralogy and Petrology, 162, 415–445.CrossRefGoogle Scholar
Fudali, R.F. (1963) Experimental studies bearing on the origin of pseudoleucite and associated problems of alkalic rock genesis. Geological Society of America Bulletin, 74, 1101–1126.CrossRefGoogle Scholar
Gamble, R.P. and Taylor, L.A. (1980) Crystal/liquid partitioning in augite: effects of cooling rate. Earth and Planetary Letters, 47, 21–33.CrossRefGoogle Scholar
Gibb, F.G.F. (1968) Flow differentiation in the xenolithic ultrabasic dykes of the Cuillins and of the Strathaird Peninsula, Isle of Skye, Scotland. Journal of Petrology, 9, 411–443.CrossRefGoogle Scholar
Gibb, F.G.F. (1973) The zoned clinopyroxenes of the Shiant Islands sill, Scotland. Journal of Petrology, 14, 203–230.Google Scholar
Gibb, F.G.F. and Henderson, C.M.B. (1978) The petrology of the Dippin Sill, Isle of Arran. Scottish Journal of Geology, 14, 1–27.CrossRefGoogle Scholar
Gibb, F.G.F. and Henderson, C.M.B. (1996) The Shiant Isles Main Sill: structure and mineral fractionation trends. Mineralogical Magazine, 60, 67–97.CrossRefGoogle Scholar
Gibb, F.G.F. and Henderson, C.M.B. (2006) Chemistry of the Shiant Isles main sill, NW Scotland, and wider implications for the petrogenesis of mafic sills. Journal of Petrology, 47, 191–230.CrossRefGoogle Scholar
Greenough, J.D. and Kyser, T.K. (2003) Contrasting Archean and Proterozoic lithospheric mantle: iso-topic evidence from the Shonkin Sag sill (Montana). Contributions to Mineralogy and Petrology, 145, 169–181.CrossRefGoogle Scholar
Gupta, A.K. and Green, D.H. (1988) The liquidus surface of the system forsterite—kalsilite—quartz at 28 kb under dry conditions, in presence of H2O, and of CO2 . Mineralogy and Petrology, 39, 163–174.CrossRefGoogle Scholar
Gupta, A.K., Mauli Dwivedi, M., Bhattachariya, H. and Dasgupta, S. (2010) Silica-undersaturated portion of the sytem nepheline—kalsilite—SiO2 at 2 GPa [P(H2O) = P(total)]. The Canadian Mineralogist, 48, 1297–1313.CrossRefGoogle Scholar
Hamilton, D.L. and MacKenzie, W.S. (1965) Phase-equilibrium studies in the system NaAlSiO4(nepheline)-KAlSiO4 (kalsilite)-SiO2-H2O. Mineralogical Magazine, 34, 214–231.CrossRefGoogle Scholar
Hammer, J.E. (2008) Experimental studies of the kinetics and energetics of magma crystallization. Pp. 9–59 in: Minerals, Inclusions and Volcanic Processes (K.D. Putirka and F.J. Tepley III, editors) Reviews in Mineralogy and Geochemistry, 69. Mineralogical Society of America, Washington DC and the Geochemical Society, St. Louis, Missouri, USA.CrossRefGoogle Scholar
Helz, R.T. (1982) Phase relations and compositions of amphiboles produced in studies of the melting behaviour of rocks. Pp. 279–353 in: Amphiboles: Petrology and Experimental Phase Relations (D.R. Veblen and P.H. Ribbe, editors). Reviews in Mineralogy, 9B. Mineralogical Society of America, Washington DC.Google Scholar
Henderson, C.M.B. (1965) Minor element chemistry of leucite and pseudoleucite. Mineralogical Magazine, 35, 596–603.CrossRefGoogle Scholar
Henderson, C.M.B. and Foland, KA. (1996) Ba-and Ti-rich primary biotite from the Brome alkaline igneous complex. Monteregian Hills, Quebec: mechanisms of substitution. The Canadian Mineralogist, 34, 1241–1252.Google Scholar
Henderson, C.M.B. and Gibb, F.G.F. (1977) Formation of analcime in the Dippin sill, Isle of Arran. Mineralogical Magazine, 41, 534–547.CrossRefGoogle Scholar
Henderson, C.M.B. and Gibb, F.G.F. (1983) Felsic mineral crystallization trends in differentiating alkaline basic magmas. Contributions to Mineralogy and Petrology, 84, 355–364.CrossRefGoogle Scholar
Henderson, C.M.B. and Gibb, F.G.F. (1987) The petrology of the Lugar sill, SW Scotland. Transactions of the Royal Society of Edinburgh, 77, 325–347.CrossRefGoogle Scholar
Henderson, C.M.B. and Pierozynski, W.J. (2012) An experimental study of Sr, Ba and Rb partitioning between alkali feldspar and silicate liquid in the system nepheline—kalsilite—quartz at 0.1 GPa P(H2O): a reassessment. Mineralogical Magazine, 76, 157–190.CrossRefGoogle Scholar
Hurlbut, C.S. Jr and Griggs, D. (1939) Igneous rocks of the Highwood Mountains Montana. Part I. The laccoliths. Bulletin of the Geological Society of America, 50, 1043–1112.Google Scholar
Jones, R.H. and MacKenzie, W.S. (1989) Liquidus phase reationships in the system CaAl2Si2O8—NaAlSi3O8-KAlSi3O8-NaAlSiO4-KAlSiO4 at P(H2O) = 5 kb. Contributions to Mineralogy and Petrology, 101, 78–92.Google Scholar
Kent, A.J.R (2008) Melt inclusions in basaltic and related volcanic rocks. Pp. 273–331 in: Minerals, Inclusions and Volcanic Processes (KD. Putirka and F.J. Tepley III, editors) Reviews in Mineralogy and Geochemistry, 69. Mineralogical Society of America, Washington DC and the Geochemical Society, St. Louis, Missouri, USA.CrossRefGoogle Scholar
Krkpatrick, R.J., Kuo, L.-C, and Melchior, I (1981) Crystal growth in incongruently-melting composi-tions: programmed cooling experiments with diop-side. American Mineralogist, 66, 233–241.Google Scholar
Larsen, E.S. (1941) Igneous rocks of the Highwood Mountains Montana. Part II. The extrusive rocks. Bulletin of the Geological Society of America, 52, 1733–1752.CrossRefGoogle Scholar
Larsen, E.S. and Buie, B.F. (1941) Igneous rocks of the Highwood Mountains Montana. Part V. Contact Metamorphism. Bulletin of the Geological Society of America, 52, 1829–1840.CrossRefGoogle Scholar
Larsen, E.S., Hurlbut, C.S. Jr, Buie, B.F. and Burgess, C.H. (1941a) Igneous rocks of the Highwood Mountains Montana. Part VI. Mineralogy. Bulletin of the Geological Society of America, 52, 1841–1856.CrossRefGoogle Scholar
Larsen, E.S., Hurlbut, C.S. Jr, Burgess, C.H. and Buie, B.F. (1941b) Igneous rocks of the Highwood Mountains Montana. Part VII. Petrology. Bulletin of the Geological Society of America, 52, 1857–1868.CrossRefGoogle Scholar
Leake, B.E., Woolley, A.R., Arps, C.E.S., Birch, W.D., Gilbert, M.C., Grice, J.D., Hawthorne, F.C., Kato, A., Kisch, H.J., Krivovichev, V.G, Linthout, K, Laird, J., Mandarino, J.A., Maresch, W.V., Nickel, E.H, Rock, N.M.S., Schumacher, J.C., Smith, D.C., Stephenson, N.C.N., Ungaretti, L., Whittaker, E.J.W. and Guo, Y.Z. (1997) Nomenclature of amphiboles: report of the International Mineralogical Association, commission on new minerals and mineral names. American Mineralogist, 82, 1019–1037.Google Scholar
Le Maitre, R.W., Streikesen, A., Zanettin, B., Le Bas, M.J., Bonin, B., Bateman, P., Bellieni, G, Dudek, A., Efremova, S., Keller, A.J., Lameyre, J., Sabine, PA., Schmid, R, Sørensen, H. and Woolley, A.R. (2002) Igneous Rocks: A Classification and Glossary of Terms. Recommendations of the International Union of Geological Sciences Subcommision on the Systematics of Igneous Rocks. Cambridge University Press, Cambridge, UK, 236 pp.CrossRefGoogle Scholar
Lindsley, D.H. (1966) P—T projection for part of the system kalsilite—silica. Geophysical Laboratory Report, Carnegie Institution Yearbook, 65, 244–247.Google Scholar
Lofgren, G (1974) An experimental study of plagioclase crystal morphology: isothermal crystallization. American Journal of Science, 274, 243–273.CrossRefGoogle Scholar
Lofgren, G (1980) Experimental studies on the dynamic crystallization of silicate melts. Pp. 487–551 in: Physics of Magmatic Processes (R.B. Hargraves, editor). Princeton University Press, Princeton, New Jersey, USA.Google Scholar
Luth, W.C. (1967a) The system KAlSiO4-Mg2SiO4-KAlSi2O6. Journal of the American Ceramic Society, 50, 174–176.Google Scholar
Luth, W.C. (1967b) Studies in the system KAlSiO4-Mg2SiO4—SiO2—H2O: I. Inferred phase relations and petrologic applications. Journal of Petrology, 8, 372–416.CrossRefGoogle Scholar
Luhr, J.F. and Carmichael, I.S.E. (1981) The Colima Volcanic Complex, Mexico: Part II. Late-Quaternary cinder cones. Contributions to Mineralogy and Petrology, 76, 127–147.CrossRefGoogle Scholar
Macdonald, R., Upton, B.G.J., Collerson, K.D., Hearn, B.C. Jr and James, D. (1992) Potassic mafic lavas of the Bearpaw Mountains, Montana: chemistry and origin. Journal of Petrology, 33, 305–346.CrossRefGoogle Scholar
Mankser, W.L., Ewing, R.C. and Keil, K. (1979) Barian-titanian biotites in nephelinites from Oahu, Hawaii. American Mineralogist, 64, 156–159.Google Scholar
McBirney, A.R. (1980) Mixing and unmixing of magmas. Journal of Volcanology and Geothermal Research, 7, 357–371.Google Scholar
Melluso, L., Morra, V. and Di Girolamo, P. (1996) The Mt. Vulture volcanic complex (Italy): evidence for distinct parental magmas and for residual melts with melilite. Mineralogy and Petrology, 56, 225–250.Google Scholar
Metrich, N. and Wallace, P.J. (2008) Volatile abun-dances in basaltic magmas and their degassing paths tracked by melt inclusions. Pp. 363–402 in: Minerals, Inclusions and Volcanic Processes (K.D. Putirka and F.J. Tepley III, editors) Reviews in Mineralogy and Geochemistry, 69. Mineralogical Society of America, Washington DC and the Geochemical Society, St. Louis, Missouri, USA.Google Scholar
Mitchell, RH. (1981) Titaniferous phlogopites from the West Kimberley area, western Australia. Contributions to Mineralogy and Petrology, 76, 243–251.Google Scholar
Mitchell, RH. and Bergman, S.C. (1991) Petrology of Lamproites. Plenum Press, New York, 449 pp.CrossRefGoogle Scholar
Mitchell, R.H. and Edgar, A.D. (2002) Melting experiments on SiO2-rich lamproites to 6.4 GPa and their bearing on the sources of lamproite magmas. Mineralogy and Petrology, 74, 115–128.CrossRefGoogle Scholar
Morimoto, N, Fabries, J., Ferguson, A.K., Ginzburg, I.V., Seifert, F.A. and Zussman, J. (1988) Nomenclature of pyroxenes. Mineralogical Magazine, 52, 535–550.CrossRefGoogle Scholar
Nag, K., Arima, M. and Gupta, A.K. (2007) Experimental study of the joins forsterite-diopside-leucite and forsterite—leucite—akermanite up to 2.3 GPa [P(H2O = P(Total)] and variable temperatures: its petrological significance. Lithos, 98, 177–194.CrossRefGoogle Scholar
Nash, W.P. and Wilkinson, J.F.G (1970) Shonkin Sag Laccolith, Montana. I. Mafic minerals and estimates of temperature, pressure, oxygen fugacity and silica activity. Contributions to Mineralogy and Petrology, 25, 241–269.CrossRefGoogle Scholar
Nash, W.P. and Wilkinson, J.F.G. (1971) Shonkin Sag Laccolith, Montana. II. Bulk rock chemistry. Contributions to Mineralogy and Petrology, 33, 162–170.Google Scholar
Nelson, S.T. and Montana, A. (1992) Sieve-textured plagioclase in volcanic rocks produced by rapid decompression. American Mineralogist, 77, 1242–1249.Google Scholar
O'Brien, H.E., Irving, A.J. and McCallum, I.S. (1988) Complex zoning and resorption of phenocrysts in mixed potassic mafic magmas of the Highwood Mountains, Montana. American Mineralogist, 73, 1007–1024.Google Scholar
O'Brien, H.E., Irving, A.J. and McCallum, I.S. (1991) Eocene potassic magmatism in the Highwood Mountains, Montana: petrology, geochemistry and tectonic implications. Journal of Geophysical Research, 96, B8, 13237–13260.Google Scholar
O'Brien, H.E., Irving, A.J., McCallum, I.S. and Thirlwall, M.F. (1995) Strontium, neodymium, and lead isotopic evidence for the interaction of post-subduction astheno spheric potassic mafic magmas of the Highwood Mountains, Montana, USA, with ancient Wyoming craton lithospheric mantle. Geochimica et Cosmochimica Acta, 59, 4539–4556.CrossRefGoogle Scholar
Osborne, F.F. and Roberts, E.J. (1931) Differentiation in the Shonkin Sag laccolith, Montana. American Journal of Science, 22, 331–353.CrossRefGoogle Scholar
Pirsson, L.V. (1905) The petrology and geology of the igneous rocks of the Highwood Mountains, Montana. U.S. Geological Survey, Bulletin 237.Google Scholar
Powell, R and Powell, M. (1974) An olivine-clino-pyroxene geothermometer. Contributions to Mineralogy and Petrology, 48, 249–263.CrossRefGoogle Scholar
Putirka, K.D. (2008) Thermometers and barometers for volcanic systems. Pp. 61–120 in: Minerals, Inclusions and Volcanic Processes (K.D. Putirka and F.J. Tepley III, editors) Reviews in Mineralogy and Geochemistry, 69. Mineralogical Society of America, Washington DC and the Geochemical Society, St. Louis, Missouri, USA.CrossRefGoogle Scholar
Rieder, M., Cavazzini, C, D'Yakonov, Y.S., Frank-Kamenetskii, VA., Gottardi, G, Guggenheim, S., Koval, P.V., Muller, G., Neiva, A.M.R., Radoslovich, E., Robert, J.-L., Sassi, F.P., Takeda, H, Weiss, Z. and Wones, D.R (1998) Nomenclature of the micas. The Canadian Mineralogist, 36, 41–48.Google Scholar
Righter, K., Darby Dyar, M., Delaney, J.S., Venneman, T.W., Hervig, R.L. and King, P.L. (2002) Correlations of octahedral cations with OH∼, O ∼, Cl-, and F∼ in biotite from volcanic rocks and xenoliths. American Mineralogist, 87, 142–153.CrossRefGoogle Scholar
Roux, J. and Hamilton, D.L. (1976) Primary igneous analcite—an experimental study. Journal of Petrology, 17, 244–257.CrossRefGoogle Scholar
Ruddock, D.I. and Hamilton, D.L. (1978) The system KAlSi2O6-CaMgSi2O6-H2O at 4 kilobars. Progress in Experimental Petrology, Fourth Report. NERC Publications Series D11, 25–27.Google Scholar
Rutherford, M.J. (2008) Magma ascent rates. Pp. 241–271 in: Minerals, Inclusions and Volcanic Processes (K.D. Putirka and F.J. Tepley III, editors) Reviews in Mineralogy and Geochemistry, 69. Mineralogical Society of America, Washington DC and the Geochemical Society, St. Louis, Missouri, USA.Google Scholar
Sack, R.O. and Carmichael, I.S.E. (1984) Fe+ = Mg+and TiAl2 = MgSi2 exchange reactions between clinopyroxene and silicate melts. Contributions to Mineralogy and Petrology, 85, 103–115.CrossRefGoogle Scholar
Sato, M. (1978) Oxygen fugacity of basaltic magmas and the role of gas forming elements. Geophysical Research Letters, 5, 447–449.CrossRefGoogle Scholar
Scarfe, CM., Luth, W.C. and Tuttle, O.F. (1966) An experimental study bearing on the absence of leucite in plutonic rocks. American Mineralogist, 51, 726–735.Google Scholar
Schairer, J.F. (1955) The ternary systems leuci-te—corundum—spinel and leucite—forsterite—spinel. Journal of the American Ceramic Society, 38, 153–158.CrossRefGoogle Scholar
Schairer, J.F. (1957) Melting relations of the common rock-forming oxides. Journal of the American Ceramic Society, 40, 215–235.Google Scholar
Sekine, T. and Wyllie, P.J. (1982) Phase relationships in the system KAlSiO4-Mg2SiO4-SiO2-H2O as a model for hybridization between hydrous siliceous melts and peridotite. Contributions to Mineralogy and Petrology, 79, 368–374.CrossRefGoogle Scholar
Sood, M.K., Platt, R.G. and Edgar, A.D. (1970) Phase relations in portions of the system diopside—nepheline—kalsilite—silica and their importance in the genesis of alkaline rocks. The Canadian Mineralogist, 10, 380–394.Google Scholar
Speer, JA. (1984) Micas in igneous rocks. Pp. 299–356 in: Micas (S.W. Bailey, editor). Reviews in Mineralogy, 13. Mineralogical Society of America, Washington DC.CrossRefGoogle Scholar
Streck, M.J. (2008) Mineral textures and zoning as evidence for open system processes. Pp. 595–622 in: Minerals, Inclusions and Volcanic Processes (K.D. Putirka and F.J. Tepley III, editors) Reviews in Mineralogy and Geochemistry, 69. Mineralogical Society of America, Washington DC and the Geochemical Society, St. Louis, Missouri, USA.CrossRefGoogle Scholar
Thompson, RN. (1974) Primary basalts and magma genesis I. Skye, northwest Scotland. Contributions to Mineralogy and Petrology, 45, 317–341.CrossRefGoogle Scholar
Wallace, P. and Carmichael, I.S.E. (1989) Minette lavas and associated leucitites from the Western Front of the Mexican Volcanic Belt: petrology, chemistry, and origin. Contributions to Mineralogy and Petrology, 103, 470–492.CrossRefGoogle Scholar
Walker, D., Kirkpatrick, R.J., Longhi, I and Hays, J.F. (1976) Crystallization history of lunar picritic basalt sample 12002: phase equilibria and cooling-rate studies. Geological Society of America Bulletin, 87, 646–656.2.0.CO;2>CrossRefGoogle Scholar
Weed, W.H. and Pirsson, L.V. (1895) Highwood Mountains of Montana. Geological Society America Bulletin, 6, 389–422.CrossRefGoogle Scholar
Wendlandt, RF. and Eggler, D.H. (1980) The origins of potassic magmas: 1. Melting relations in the systems KAlSiO4-Mg2SiO4-SiO2 and KAlSiO4-MgO-SiO2—CO2 to 30 kilobars. American Journal of Science, 280, 385–420.Google Scholar
Wilson, A.D. (1955) Determination of ferrous iron in rocks and minerals. Bulletin of the Geological Survey of Great Britain, 9, 56–58.Google Scholar
Wones, D.R (1981) Mafic silicates as indicators of intensive variables in granitic magmas. Mining Geology, 31, 191–212.Google Scholar
Wood, B.J. (1976) An olivine—pyroxene geotherm-ometer: a discussion. Contributions to Mineralogy and Petrology, 56, 297–303.CrossRefGoogle Scholar
Zeng, R and MacKenzie, W.S. (1984) Phase diagrams for the system leucite—H2O at 2 and 5 kb. Progress in Experimental Petrology, Sixth Report. NERC Publications Series D25, 25–27.Google Scholar