Abstract
This paper reports the results of a detailed experimental investigation of fractionation of natural basaltic compositions under conditions of high pressure and high temperature. A single stage, piston-cylinder apparatus has been used in the pressure range up to 27 kb and at temperatures up to 1500° C to study the melting behaviour of several basaltic compositions. The compositions chosen are olivine-rich (20% or more normative olivine) and include olivine tholeiite (12% normative hypersthene), olivine basalt (1% normative hypersthene) alkali olivine basalt (2% normative nepheline) and picrite (3% normative hypersthene). The liquidus phases of the olivine tholeiite and olivine basalt are olivine at 1 Atmosphere, 4.5 kb and 9 kb, orthopyroxene at 13.5 and 18 kb, clinopyroxene at 22.5 kb and garnet at 27 kb. In the alkali olivine basalt composition, the liquidus phases are olivine at 1 Atmosphere and 9 kb, orthopyroxene with clinopyroxene at 13.5 kb, clinopyroxene at 18 kb and garnet at 27 kb. The sequence of appearance of phases below the liquidus has also been studied in detail. The electron probe micro-analyser has been used to make partial quantitative analyses of olivines, orthopyroxenes, clinopyroxenes and garnets which have crystallized at high pressure.
These experimental and analytical results are used to determine the directions of fractionation of basaltic magmas during crystallization over a wide range of pressures. At pressures corresponding to depths of 35–70 km separation of aluminous enstatite from olivine tholeiite magma produces a direct fractionation trend from olivine tholeiites through olivine basalts to alkali olivine basalts. Co-precipitation of sub-calcic, aluminous clinopyroxene with the orthopyroxene in the more undersaturated compositions of this sequence produces derivative liquids of basanite type. Magmas of alkali olivine basalt and basanite type represent the lower temperature liquids derived by approximately 30% crystallization of olivine-rich tholeiite at 35–70 km depth. At depths of about 30 km, fractionation of olivine-rich tholeiite with separation of both olivine and low-alumina enstatite, joined at lower temperatures by sub-calcic clinopyroxene, leads to derivative liquids with relatively constant SiO2 (48 to 50%) increasingly high Al2O3 (15–17%) contents and retaining olivine + hypersthene normative chemistry (5–15% normative olivine). These have the composition of typical high-alumina olivine tholeiites. The effects of low pressure fractionation may be superimposed on magma compositions derived from various depths within the mantle. These lead to divergence of the alkali olivine basalt and tholeiitic series but convergence of both the low-alumina and high-alumina tholeiites towards quartz tholeiite derivative liquids.
The general problem of derivation of basaltic magmas from a mantle of peridotitic composition is discussed in some detail. Magmas are considered to be a consequence of partial melting but the composition of a magma is determined not by the depth of partial melting but by the depth at which magma segregation from residual crystals occurs. Magma generation from parental peridotite (pyrolite) at depths up to 100 km involves liquid-crystal equilibria between basaltic liquids and olivine + aluminous pyroxenes and does not involve garnet. At 35–70 km depth, basaltic liquids segregating from a pyrolite mantle will be of alkali olivine basalt type with about 20% partial melting but with increasing degrees of partial melting, liquids will change to olivine-rich tholeiite type with about 30% melting. If the depth of magma segregation is about 30 km, then magmas produced by 20–25% partial melting will be of high-alumina olivine tholeiite type, similar to the “oceanic tholeiites” occurring on the sea floor along the mid-oceanic ridges.
Hypotheses of magma fractionation and generation by partial melting are considered in relation to the abundances and ratios of trace elements and in relation to isotopic abundance data on natural basalts. It is shown that there is a group of elements (including K, Ti, P, U, Th, Ba, Rb, Sr, Cs, Zr, Hf and the rare-earth elements) which show enrichment factors in alkali olivine basalts and in some tholeiites, which are inconsistent with simple crystal fractionation relationships between the magma types. This group of elements has been called “incompatible elements” referring to their inability to substitute to any appreciable extent in the major minerals of the upper mantle (olivine, aluminous pyroxenes). Because of the lack of temperature contrast between magma and wall-rock for a body of magma near to its depth of segregation in the mantle, cooling of the magma involves complementary processes of reaction with the wall-rook, including selective melting and extraction of the lowest melting fraction. The “incompatible elements” are probably highly concentrated in the lowest melting fraction of the pyrolite. The production of large overall enrichments in “incompatible elements” in a magma by reaction with and highly selective sampling of large volumes of mantle wall-rock during slow ascent of a magma is considered to be a normal, complementary process to crystal fractionation in the mantle. This process has been called “wall-rock reaction”. Magma generation in the mantle is rarely a simple, closed-system partial melting process and the isotopic abundances and “incompatible element” abundances of a basalt as observed at the earth's surface may be largely determined by the degree of reaction with the mantle or lower crustal wall-rocks and bear little relation to the abundances and ratios of the original parental mantle material (pyrolite).
Occurrences of cognate xenoliths and xenocrysts in basalts are considered in relation to the experimental data on liquid-crystal equilibria at high pressure. It is inferred that the lherzolite nodules largely represent residual material after extraction of alkali olivine basalt from mantle pyrolite or pyrolite which has been selectively depleted in “incompatible elements” by wall-rock reaction processes. Lherzolite nodules included in tholeiitic magmas would melt to a relatively large extent and disintegrate, but would have a largely refractory character if included in alkali olivine basalt magma. Other examples of xenocrystal material in basalts are shown to be probable liquidus crystals or accumulates at high pressure from basaltic magma and provide a useful link between the experimental study and natural processes.
Similar content being viewed by others
References
Bartholomé, P.: Co-existing pyroxenes in igneous and metamorphic rocks. Geol. Mag. 98, 346–348 (1961).
Birch, F.: Elasticity and constitution of the earth's interior. J. Geophys. Research 57, 227–286 (1952).
Boyd, F. R., and J. L. England: Apparatus for phase equilibrium measurements at pressures up to 50 kb and temperatures up to 1750° C. J. Geophys. Research 65, 741–748 (1960a).
—: The quartz-coesite transition. J. Geophys. Research 65, 749–756 (1960b).
—: Effect of pressure on the melting of diopside, CaMgSi2O6 and albite NaAlSi3O8 in the range up to 30 kb. J. Geophys. Research 68, 311–323 (1963).
— and B. T. C. Davis: Effects of pressure on the melting and polymorphism of enstatite, MgSiO3. J. Geophys. Research 69, 2101–2109 (1964).
—, and J. F. Schairer: The system MgSiO3-CaMgSi2O6. J. Petrology 5, 275–309 (1964).
Brothers, R. N.: Olivine nodules from New Zealand. Rept. Intern. Geol. Congr. 21st Session Norden 13, 68–81 (1960).
Clark, S. P., and A. E. Ringwood: Density distribution and constitution of the mantle. Rev. Geophys. 2, 35–88 (1964).
Compston, W., I. McDougall, and K. S. Heier: Geochemical comparison of the Mesozoic basaltic rocks of Antarctica, South Africa, South America and Tasmania. Geochim. et Cosmochim. Acta (1966) (in press).
Coombs, D. S.: Trends and affinities of basaltic magmas and pyroxenes as illustrated on the diopside-olivine-silica diagram. Min. Soc. Am. Special Paper 1, 227–250 (1963).
Davis, B. T. C.: The system enstatite-diopside at 30 kilobars pressure. Carnegie Inst. Wash. Year Bk. 62, 103–107 (1963).
—: The system diopside-forsterite-pyrope at 40 kilobars. Carnegie Inst. Wash. Year Bk. 63, 165–171 (1964).
—, and F. R. Boyd: The join Mg2Si2O6-CaMgSi2O6 at 30 kilobars pressure and its application to pyroxenes from kimberlites. J. Geophys. Research 71, 3567–3576 (1966).
—, and J. F. Schairer: Melting relations in the join diopside-forsterite-pyrope at 40 kilobars and at one atmosphere. Carnegie Inst. Wash. Year Bk. 64, 123–134 (1965).
Den Tex, E.: Gefügekundliche und geothermometrische Hinweise auf die tiefe, exogene Herkunft lherzolithischer Knollen aus Basaltlaven. Neues Jahrb. Mineral. Monatsh. 9/10, 225–236 (1963).
De Roever, W. P.: Mantelgesteine und Magmen tiefer Herkunft. Fortschr. Mineral. 39, 96–107 (1961).
—: Ein Versuch zur Synthese der verschiedenen Ansichten zur Herkunft der Mafitknollen vom Maarvulkan Dreiser Weiher in der Eifel. Neues Jahrb. Mineral. Monatsh. 9/10, 243–250 (1963).
Eaton, J. P., and K. J. Murata: How volcanoes grow. Science 132, 925–938 (1960).
Elsasser, W. M.: Early history of the earth, chap. 1, p. 1–30. In: Earth science and meteoritics in honour of F. G. Houtermans, edited by J. Geiss and E. Goldberg. Amsterdam: North Holland Publ. Co. 1963.
Engel, A. E. J., and C. G. Engel: Composition of basalts from the Mid-Atlantic Ridge. Science 144, 1330–1333 (1964a).
—: Igneous rocks of the East Pacific Rise. Science 146, 477–485 (1964b).
—, and R. G. Havens: Chemical characteristics of oceanic basalts and the upper mantle. Bull. Geol. Soc. Am. 76, 719–734 (1965).
Engel, C. G., R. L. Fisher, and A. E. J. Engel: Igneous rocks of the Indian Ocean Floor. Science 150, 605–610 (1965).
Faure, G., and P. M. Hurley: The isotopic composition of strontium in oceanic and continental basalts: application to the origin of igneous rocks. J. Petrology 4, 31–50 (1963).
Frechen, J.: Die Genese der Olivinausscheidungen vom Dreiser Weiher (Eifel) und Finkengebirg (Siebengebirge). Neues Jahrb. Mineral. Abh. 79A, 317–406 (1948).
—: Kristallisation, Mineralbestand, Mineralchemismus und Förderfolge der Mafitite vom Dreiser Weiher in der Eifel. Neues Jahrb. Mineral. Monatsh. 9/10, 205–225 (1963).
Furumoto, A. S., N. J. Thompson, and G. P. Woollard: The structure of Koolau Volcano from seismic refraction studies. Pacific Sci. 19, 306–315 (1965).
Gast, P. W.: Terrestrial ratio of potassium to rubidium and the composition of the earth's mantle. Science 147, 858–860 (1965).
—: Isotope geochemistry of volcanic rocks, to be published in: Basaltic rocks H. H. Hess, (ed.). New York: J. Wiley & Sons — Interscience 1966.
—, G. R. Tilton, and C. E. Hedge: Isotopic composition of lead and strontium from Ascension and Gough Islands. Science 145, 1181–1185 (1964).
Green, D. H.: Alumina content of enstatite in a Venezuelan high temperature peridotite. Bull. Geol. Soc. Am. 74, 1397–1402 (1963).
—: The petrogenesis of the high temperature peridotite in the Lizard area, Cornwall. J. Petrology 5, 134–188 (1964).
—: The origin of basaltic magmas; to be published in: Basaltic rocks H. H. Hess, (ed.). New York: J. Wiley & Sons — Interscience 1967.
—: The origin of the “eclogites” from Salt Lake Crater, Hawaii. Earth and Planetary Sci. Letters 1, 414–420 (1966b).
-, and J. Easton: A contribution to mineralogy of lherzolite inclusions in alkali olivine basalts from western Victoria (in preparation) 1966.
—, and A. E. Ringwood: Mineral assemblages in a model mantle composition. J. Geophys. Research 68, 937–945 (1963).
—: Fractionation of basalt magmas at high pressures. Nature 201, 1276–1279 (1964).
- - - An experimental investigation of the gabbro to eclogite transformation and its petrological applications. Geochim. et Cosmochim. Acta (1967) (in press).
Green, T. H.: High pressure experiments on the genesis of anorthosites. (In preparation, 1966).
Green, T. H., D. H. Green, and A. E. Ringwood: The origin of high-alumina basalts and their relationships to quartz tholeiites and alkali basalts. Earth and Planetary Sci. Letters 2, 41–52 (1967).
—, A. E. Ringwood, and A. Major: Friction effects and pressure calibration in a pistoncylinder apparatus at high pressure and temperature. J. Geophys. Research 71, 3589–3594 (1966).
Gunn, B. M.: Differentiation in Ferrar Dolerites, Antarctica. New Zealand J. Geol. Geophys. 5, 820–863 (1962).
—: Layered intrusions in Ferrar Dolerites, Antarctica. Min. Soc. Am. Special Paper 1, 124–133 (1963).
—: K/Rb and K/Ba ratios in Antarctic and New Zealand tholeiites and alkali basalts. J. Geophys. Research 70, 6241–6247 (1965).
—: Modal and element variation in Antarctic tholeiites. Geochim. et Cosmochim. Acta 30, 881–920 (1966).
Hamilton, E. I.: The isotopic composition of strontium in the Skaergaard intrusion, East Greenland. J. Petrology 4, 383–391 (1963).
—: Distribution of some trace elements and the isotopic composition of strontium in Hawaiian lavas. Nature 206, 251–253 (1965).
Harris, P. G.: Zone refining and the origin of potassic basalts. Geochim. et Cosmochim. Acta 12, 195–208 (1957).
Haskin, L. A., F. A. Frey, R. A. Schmitt, and R. H. Smith: Meteoritic, solar and terrestrial rare-earth distributions. In: Physics and Chemistry of the Earth, vol. 7. pp. 167–321 New York: Pergamon 1966.
Hedge, C. E., and F. G. Walthall: Radiogenic strontium-87 as an index of geologic processes. Science 140, 1214–1217 (1963).
Heier, K. S.: Trace elements in feldspars — a review. Norsk. Geol. Tidsskr. 42, 415–454 (1962).
—, W. Compston, and I. McDougall: Thorium and uranium concentrations, and the isotopic composition of strontium in the differentiated Tasmanian dolerites. Geochim. et Cosmochim. Acta 29, 643–659 (1965).
—, I. McDougall, and J. A. S. Adams: Thorium, uranium and potassium concentrations in Hawaiian lavas. Nature 201, 254–256 (1964).
—, and J. W. Rogers: Radiometric determination of thorium, uranium and potassium in basalts and in two magmatic differentiation series. Geochim. et Cosmochim. Acta 27, 137–154 (1963).
Hess, H. H.: Orthopyroxenes of the Bushveld type, ion substitutions and changes in unit cell dimensions. Am. J. Sci. Bowen Volume 173–178 (1952).
- The oceanic crust, the upper mantle and the Mayaguez serpentinized peridotite. In: A study of serpentinite (C. A. Burk, ed.). U. S. National Acad. Science — National Research Council Publ. No. 1188, 169–174 (1964).
Holmes, A., and H. F. Harwood: Petrology of the volcanic fields east and southeast of Ruwenzori, Uganda. Quart. J. Geol. Soc. London 88, 370–442 (1932).
Jamieson, B. G.: Evidence on the evolution of basaltic magma at high pressures. Nature 212, 243–246 (1966).
Kretz, R.: Some applications of thermodynamics to co-existing minerals of variable composition. Examples: orthopyroxene-clinopyroxene and orthopyroxene-garnet. J. Geol. 69, 361–387 (1961).
Kuno, H.: High-alumina basalt. J. Petrology 1, 121–145 (1960).
—: Aluminian augite and bronzite in alkali olivine basalt from Taka-sima, north Kyusyu, Japan. In: Advancing frontiers in geology and geophysics. Hyderabad: Osmania Univ. Press 1964.
—, K. Yamasaki, C. Iida, and K. Nagashima: Differentiation of Hawaiian magmas. Japan. J. Geol. and Geography, Trans. 28, 179–218 (1957).
Kushiro, I.: The liquidus relations in the systems forsterite-CaAl2SiO6-silica and forsteritenepheline-silica at high pressures. Carnegie Inst. Wash. Year Bk. 64, 103–108 (1965).
—, and H. Kuno: Origin of primary basalt magmas and classification of basaltic rocks. J. Petrology 4, 75–89 (1963).
Larsen, E. S.: Petrographic province of central Montana. Bull. Geol. Soc. Am. 51, 887–948 (1940).
Le Maitre, R. W.: Petrology of volcanic rocks, Gough Island, South Atlantic. Bull. Geol. Soc. Am. 73, 1309–1340 (1962).
Lessing, P., and E. J. Catanzaro: Sr87/Sr86 in Hawaiian lavas. J. Geophys. Research 69, 1599–1601 (1964).
Macdonald, G. A.: Hawaiian petrographic province. Bull. Geol. Soc. Am. 60, 1541–1595 (1949).
—, and T. Katsura: Variations in the lava of the 1959 eruption in Kilauea Iki. Pacific Sci. 15, 358–369 (1961).
—: Chemical composition of Hawaiian lavas. J. Petrology 5, 82–133 (1964).
MacGregor, I. D., and A. E. Ringwood: The natural system enstatite-pyrope. Carnegie Inst. Wash. Year Bk. 63, 161–163 (1964).
Morgan, J. W., and A. D. T. Goode: Potassium abundances in some ultrabasic and basic rocks. Earth and Planetary Sci. Letters 1, 110–112 (1966).
Muir, I. D., and C. E. Tilley: Contributions to the petrology of Hawaiian basalts. I. The picrite basalts of Kilauea. Am. J. Sci. 255, 241–253 (1957).
—: The tholeiitic basalts of Mauna Loa and Kilauea. Pt. 2 of: Contributions to the petrology of Hawaiian basalts. Am. J. Sci. 261, 111–128 (1963).
—: Basalts from the northern part of the rift zone of the Mid-Atlantic Ridge. J. Petrology 5, 409–434 (1964).
Murata, K. J.: A new method pf plotting chemical analyses of basaltic rooks. Am. J. Sci. 258-A (Bradley volume), 247–252 (1960).
—, H. Bastron, and W. W. Brannock: X-ray determinative curve for Hawaiian olivines of composition Fo76–88. U.S. Geol. Survey Profess. Papers 525-C, 35–37 (1965).
—, and D. H. Richter: The settling of olivine in Kilauean magma as shown by lavas of the 1959 eruption. Am. J. Sci. 264, 194–203 (1966a).
—: Chemistry of the lavas of the 1959–60 eruption of Kilauea volcano, Hawaii. U.S. Geol. Survey Profess. Papers 537-A, 1–26 (1966b).
Naughton, J. L., and I. L. Barnes: Geochemical studies of Hawaiian rocks related to the study of the upper mantle. Pacific Sci. 19, 287–290 (1965).
Nixon, P. H., O. von Knorring, and J. M. Rooke: Kimberlites and associated inclusions of Basutoland: a mineralogical and geochemical study. Am. Mineralogist 48, 1090–1132 (1963).
O'Hara, M. J.: Melting of garnet peridotite and eclogite at 30 kilobars. Carnegie Inst. Wash. Year Bk. 62, 71–77 (1963a).
—: The join diopside-pyrope at 30 kilobars. Carnegie Inst. Wash. Year Bk. 62, 116–118 (1963b).
—: Primary magmas and the origin of basalts. Scot. J. Geology 1, 19–40 (1965).
—, and E. L. P. Mercy: Petrology and petrogenesis of some garnetiferous peridotites. Trans. Roy. Soc. Edinburgh 45, 251–313 (1963).
Oxburgh, E. R.: Petrologioal evidence for the presence of amphibole in the upper mantle and its petrogenetic and geophysical implications. Geol. Mag. 101, 1–19 (1964).
Poldervaart, A.: Aspects of basalt petrology. J. Geol. Soc. India 3, 1–14 (1962).
—: Chemical definition of alkali basalts and tholeiites. Bull. Geol. Soc. Am. 75, 229–232 (1964).
Powell, J. L., G. Faure, and P. M. Hurley: Strontium 87 abundance in a suite of Hawaiian volcanic rocks of varying silica content. J. Geophys. Research 70, 1509–1513 (1965).
—, and S. E. De Long: Isotopic composition of strontium in volcanic rocks from Oahu. Science 153, 1239–1242 (1966).
Powers, H. A.: Composition and origin of basaltic magma of the Hawaiian Islands. Geochim. et Cosmochim. Acta 7, 77–107 (1955).
Ringwood, A. E.: A model for the upper mantle. J. Geophys. Research 67, 857–867 (1962a).
—: A model for the upper mantle, 2. J.Geophys. Research 67, 4473–4477 (1962b).
—: The chemical composition and origin of the earth. In: Advances in earth science P. M. Hurley, (ed.), p. 287–356. Boston, U.S.A.: M.I.T. Press 1966a.
—: The mineralogy of the mantle. In: Advances in earth science P. M. Hurley, ed., p. 357–417. Boston, U.S.A.: M.I.T. Press 1966b.
—, and D. H. Green: An experimental investigation of the gabbro-eclogite transformation and some geophysical implications. Tectonophysics 3, 383–427 (1966).
—, I. D. MacGregor, and F. R. Boyd: Petrological constitution of the upper mantle. Carnegie Inst. Wash. Year Bk. 63, 147–152 (1964).
Ross, C. S., M. D. Foster, and A. T. Myers: Origin of dunites and of olivine-rich inclusions in basaltic rocks. Am. Mineralogist 39, 693–737 (1954).
Schilling, J. G., and J. W. Winchester: Rare-earths in Hawaiian basalts. Science 153, 867–870 (1966).
Strange, W. E., G. P. Woollard, and J. C. Rose: An analysis of the gravity field over the Hawaiian Islands in terms of crustal structure. Pacific Sci. 19, 381–389 (1965).
Tatsumoto, M.: Isotopic composition of lead in volcanic rocks from Hawaii, Iwo Jima and Japan. Geophys. Research 71, 1721–1733 (1966a).
—: Genetic relations of oceanic basalts as indicated by lead isotopes. Science 153, 1094–1101 (1966b).
—, C. E. Hedge, and A. E. J. Engel: Potassium, rubidium, strontium, thorium, uranium, and the ratio of strontium-87 to strontium-86 in oceanic tholeiitic basalt. Science 150, 886–888 (1965).
Tilley, C. E.: Some aspects of magmatic evolution. Quart. J. Geol. Soc. London 106, 37–61 (1950).
—, and H. S. Yoder: Pyroxene fractionation in mafic magma at high pressures and its bearing on basalt genesis. Carnegie Inst. Wash. Year Bk. 63, 114–121 (1964).
—, and J. F. Schairer: Melting relations of basalts. Carnegie Inst. Wash. Year Bk. 62, 77–84 (1963).
—: New relations on melting of basalts. Carnegie Inst. Wash. Year Bk. 63, 92–97 (1964).
—: Melting relations of volcanic tholeiite and alkali rock series. Carnegie Inst. Wash. Year Bk. 64, 69–82 (1965).
Upton, B. G., and W. J. Wadsworth: Geology of Reunion Island, Indian Ocean. Nature 207, 151–154 (1965).
Verhoogen, J.: Petrological evidence on temperature distribution in the mantle of the earth. Trans. Am. Geophys. Union 35, 85–92 (1954).
Vilminot, J. C.: Les enclaves de peridotite et de pyroxenolite à spinelle dans le basalt du Rôcher du Lion (Chaine du Deves, Haute-Loire). Bull. soc. franç. minéral. et crist. 88, 109–118 (1965).
White, R. W.: Ultramafic inclusions in basaltic rocks from Hawaii. Beitr. Mineral. u. Petrog. 12, 245–314 (1966).
Wilkinson, J. F. G.: The geochemistry of a differentiated teschenite sill near Gunnedah, New South Wales. Geochim. et Cosmochim. Acta 16, 123–150 (1959).
Wilshire, H. G., and R. A. Binns: Basic and ultrabasic xenoliths from volcanic rocks of New South Wales. J. Petrology 2, 185–208 (1961).
Yagi, K.: Pillow lavas of Keflavik, Iceland, and their genetic significance. J. Fac. Sci., Hokkaido Univ., Ser. IV 12, 171–183 (1964).
Yoder, H. S.: Genesis of principal basalt magmas. Carnegie Inst. Wash. Year Bk. 63, 97–100 (1964).
—, and C. E. Tilley: Origin of basalt magmas: an experimental study of natural and synthetic rock systems. J. Petrology 3, 342–532 (1962).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Green, D.H., Ringwood, A.E. The genesis of basaltic magmas. Contr. Mineral. and Petrol. 15, 103–190 (1967). https://doi.org/10.1007/BF00372052
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00372052