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Compositional zonation and cumulus processes in the Mount Mazama magma chamber, Crater Lake, Oregon

  • Timothy H. Druitt (a1) and Charles R. Bacon (a2)

The 6845 ± 50 BP climactic eruption of Mount Mazama discharged 47 ± 9 km3 of vertically zoned calc-alkaline magma, affording a virtually complete section through the chamber. Evidence for two andesitic parents with different trace-element (particularly Sr) and water contents is preserved in the ejecta. Prior to eruption, a dominant volume of rhyodacite was underlain successively by high-Sr andesite, high-Sr crystal mushes, and low-Sr crystal mushes. Intergranular liquids in the high-Sr magmas were probably richer in water than those in the low-Sr magmas. Thermal continuity throughout the ejecta favours eruption from a single, zoned reservoir. Insight into chamber development is given by preclimactic rhyodacitic lavas and tephra erupted between about 30,000 BP and the climactic eruption. The oldest of these lavas, contaminated derivatives of low-Sr magma, contain crystal-poor magmatic inclusions of low-Sr andesite; the youngest has inclusions of high-Sr andesite and, like rhyodacitic pumice in the climactic ejecta, is hybrid magma containing an admixed high-Sr component. A model for steady-state growth of the chamber is inferred whereby repeated recharge, first by low-Sr then high-Sr andesite (± basalt), builds up a cumulate succession, while derivative liquid fractionates convectively, segregates, and mixes with an incrementally growing silicic volume. The magma chamber at Mount Mazama may provide insight into the evolution of some granitoid plutons.

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Andersen D. J. & Lindsley D. H. 1988. Internally consistent solution models for Fe–Mg–Mn–Ti oxides: Part I. Fe–Ti oxides. AM MINERAL (in press).
Anderson A. T. 1980. Significance of hornblende in calc-alkaline andesites and basalts. AM MINERAL 65, 837851.
Bacon C. R. 1983. Eruptive history of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A. J VOLCANOL GEOTHERM RES 18, 57115.
Bacon C. R. 1985. Implications of silicic vent patterns for the presence of large crustal magma chambers. J GEOPHYS RES 90, 1124311252.
Bacon C. R. 1986. Magmatic inclusions in silicic and intermediate volcanic rocks. J GEOPHYS RES 91, 60916112.
Bacon C. R. 1988. Shoshonite, calcalkaline basalt and andesite, and low-K tholeiite near Crater Lake, Oregon. TRANS AM GEOPHYS UNION 68, 1516.
Bacon C. R. & Druitt T. H. 1988. Compositional evolution of the zoned calcalkaline magma chamber of Mount Mazama, Crater Lake, Oregon. CONTRIB MINERAL PETROL 98, 224256.
Bacon C. R. & Lanphere M. A. 1983. K–Ar chronology of eruptions at Mount Mazama before the formation of Crater Lake caldera (abs.). TRANS AM GEOPHYS UNION 64, 45879.
Barnes C. G. 1983. Petrology and upward zonation of the Wooley Creek Batholith, Klamath Mountains, California. J PETROL 24, 495537.
Bateman P. C. & Chappell B. W. 1979. Crystallization, fractionation, and solidification of the Tuolomne intrusive series, Yosemite National Park, California. GEOL SOC AM BULL 90, 465482.
Blake S. & Campbell I. H. 1986. The dynamics of magma mixing during flow in volcanic conduits. CONTRIB MINERAL PETROL 94, 7281.
Blake S. & Ivey G. N. 1986. Magma mixing and the dynamics of withdrawal from stratified reservoirs. J VOLCANOL GEOTHERM RES 27, 153178.
Bruggman P. E., Bacon C. R., Aruscavage P. J., Lerner R. W., Schwarz L. J. & Stewart K. C. 1987. Chemical analyses of rocks and glass separates from Crater Lake National Park and vicinity, Oregon. US GEOL SURV OPEN-FILE REP 87–57.
Campbell I. H. & Turner J. S. 1986. The influence of viscosity on fountains in magma chambers. J PETROL 27, 130.
Cantagrel J.-M., Didier J. & Gourgaud A. 1984. Magma mixing: origin of intermediate rocks and “enclaves” from volcanism to plutonism. PHYS EARTH PLANET INT 35, 6376.
Chen C. F. & Turner J. S. 1980. Crystallization in a double-diffusive convective system. J GEOPHYS RES 85, 25732593.
Druitt T. H. & Bacon C. R. 1986. Lithic breccia and ignimbrite erupted during the collapse of Crater Lake caldera, Oregon. J VOLCANOL GEOTHERM RES 29, 132.
Druitt T. H. & Bacon C. R. 1988. Petrology of the zoned calcalkaline magma body at Mount Mazama (Crater Lake), Oregon, (subjudice)
Eichelberger J. C. 1980. Vesiculation of mafic magma during replenishment of silicic magma reservoirs. NATURE 288, 446450.
Flood R. H. & Shaw S. E. 1979. K-rich cumulate diorite at the base of a tilted granodiorite pluton from the New England batholith, Australia. J GEOL 87, 417425.
Freundt, A. & Tait S. R. 1987. The entrainment of high-viscosity magma into low–viscosity magma in eruption conduits. BULL VOLCANOL 48, 325339.
Fridrich C. J. & Mahood G. A. 1984. Reverse zoning in the resurgent intrusion of the Grizzly Peak Cauldron, Sawatch Range, Colorado. GEOL SOC AM BULL 95, 779787.
Hildreth W. 1981. Gradients in silicic magma chambers: implications for lithospheric magmatism. J GEOPHYS RES 86, 1015310192.
Huebner J. S. & Sato M. 1970. The oxygen fugacity-temperature relationships of manganese oxide and nickel oxide buffers. AM MINERAL 55, 934952.
Huppert H. E., Sparks R. S. J. & Turner J. S. 1983. Laboratory investigation of viscous effects in replenished magma chambers. EARTH PLANET SCI LETT 65, 377381.
Irvine T. N. 1980. Magmatic infiltration metasomatism, double-diffusive fractional crystallization, and adcumulate growth in the Muskox Intrusion and other layered intrusions. In Hargraves R. B. (ed.) Physics of magmatic processes, 245306. Princeton: Princeton University Press.
Irvine T. N. 1982. Terminology for layered intrusions. J PETROL 23, 127162.
Lidstrom J. W. Jr., 1971. A new model for the formation of Crater Lake Caldera, Oregon. Ph.D. Thesis, Oregon State University, Corvallis.
Marsh B. D. 1981. On the crystallinity, probability of occurrence, and rheology of lava and magma. CONTRIB MINERAL PETROL 78, 8598.
McBirney A. R. 1968. Compositional variation in the climactic eruption of Mount Mazama. In Dole H. M. (ed.) Andesite Conference Guidebook. OREGON DEP GEOL MINER IND BULL 62, 5356.
McBirney A. R., Baker B. H. & Nilson R. H. 1985. Liquid fractionation. Part I: Basic principles and experimental simulations. J VOLCANOL GEOTHERM RES 24, 124.
McCarthy T. S. & Groves D. I. 1979. The Blue Tier batholith, northeastern Tasmania. CONTRIB MINERAL PETROL 71, 193209.
Myers J. & Eugster H. P. 1983. The system Fe–Si–O: oxygen buffer calibration to l,500K. CONTRIB MINERAL PETROL 82, 7590.
Nabelek P. I., Papike J. J. & Laul J. C. 1986. The Notch Peak granitic stock, Utah: Origin of reverse zoning and petrogenesis. J PETROL 27, 10351069.
Nilson R. H., McBirney A. R. & Baker B. H. 1985. Liquid fractionation. Part II: Fluid dynamics and quantitative implications for magmatic systems. J VOLCANOL GEOTHERM RES 24, 2554.
Noble D. C., Drake J. C. & Whallon M. K. 1969. Some preliminary observations on compositional variation within the pumice- and scoria-flow deposits of Mount Mazama. In McBirney A. R. (ed.) Proceedings of the Andesite Conference. OREGON DEP GEOL MINER IND BULL 65, 157164.
Perfit M. R., Brueckner H., Lawrence J. R. & Kay R. W. 1980. Trace element and isotopic variations in a zoned pluton and associated volcanic rocks, Unalaska Island, Alaska: a model for fractionation in the Aleutian calcalkaline suite. CONTRIB MINERAL PETROL 73, 6987.
Ragland P. C. & Butler J. R. 1972. Crystallization of the West Farrington Pluton, north Carolina. J PETROL 13, 381404.
Reid J. B. Jr., Evans O. C. & Fates D. G. 1983. Magma mixing in granitic rocks of the central Sierra Nevada, California. EARTH PLANET SCI LETT 66, 243261.
Ritchey J. L. 1980. Divergent magmas at Crater Lake, Oregon: products of fractional crystallization and vertical zoning in a shallow, water-undersaturated chamber. J VOLCANOL GEOTHERM RES 7, 373386.
Sakuyama M. 1984. Magma mixing and magma plumbing systems in island arcs. BULL VOLCANOL 47, 685703.
Smith R. L. 1979. Ash-flow magmatism. GEOL SOC AM SPEC PAP 180, 527.
Snoke A. W., Quick J. E. & Bowman H. R. 1981. Bear Mountain igneous complex, Klamath Mountains, California; an ultrabasic to silicic calc-alkaline suite. J PETROL 22, 501552.
Sparks R. S. J., Huppert H. E. & Turner J. S. 1984. The fluid dynamics of evolving magma chambers. PHILOS TRANS R SOC LONDON 310, 511534.
Sparks R. S. J., Huppert H. E., Kerr R. C., McKenzie D. P. & Tait S. R. 1985. Postcumulus processes in layered intrusions. GEOL MAG 122, 555568.
Sparks R. S. J. & Marshall L. 1986. Thermal and mechanical constraints on mixing between mafic and silicic magmas. J VOLCANOL GEOTHERM RES 29, 99124.
Spera F. J., Yuen D. A., Greer J. C. & Sewell G. 1986. Dynamics of magma withdrawal from stratified magma chambers. GEOLOGY 14, 723726.
Stormer J. C. 1983. The effects of recalculation on estimates of temperature and oxygen fugacity from analyses of multicomponent iron-titanium oxides. AM MINERAL 68, 586594.
Taubeneck W. H. 1967. Petrology of the Cornucopia Tonalite Unit, Cornucopia Stock, Wallowa Mountains, northeastern Oregon. GEOL SOC AM SPEC PAP 91.
Tindle A. G. & Pearce J. A. 1981. Petrogenetic modelling of in situ fractional crystallization in the zoned Loch Doon pluton, Scotland. CONTRIB MINERAL PETROL 78, 196207.
Vernon R. H. 1983. Restite, xenoliths, and microgranitoid enclaves in granites. J PROC R SOC NEW SOUTH WALES 116, 77103.
Wager L. R., Brown G. M. & Wadsworth W. J. 1960. Types of igneous cumulate. J PETROL 1, 7385.
Wiebe R. A. & Wild T. 1983. Fractional crystallisation and magma mixing in the Tigalak layered intrusion, the Nain anorthosite complex, Labrador. CONTRIB MINERAL PETROL 84, 327344.
Williams H. 1942. The geology of Crater Lake National Park, Oregon. CARNEGIE INST WASHINGTON PUBL 540.
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