Abstract
Partitioning of elements between majorite garnet and ultrabasic melt has been studied at 16 GPa and 1950° C. Ca, Ti, La, Sm, Gd, Zr, Hf, Fe, Ni, Mn, K, and Na are enriched in the melt, whereas Al, Cr, V, Sc and Yb are concentrated in majorite garnet. Thus, majorite garnet fractionation by partial melting could produce chemical heterogeneities in these elements deviating from chondritic abundance. Using the partitioning behaviour of elements between majorite garnet and ultrabasic melt, the petrogenesis of komatiite is discussed. A simple model to explain the chemical varieties of komatiites is as follows. Aluminadepleted komatiite was generated by partial melting of the primitive mantle at 200–650 km depth, and alumina-enriched komatiite is the product of remelting of the residual solid at the same depths, whereas alumina-undepleted komatiite was formed by partial melting of the primitive upper mantle at depths shallower than 200 km. We suggest the possibility of large-scale chemical layering or heterogeneity in the early Archean upper mantle as an alternative model for komatiite genesis; shallower mantle depleted in majorite garnet and the underlying mantle enriched in majorite garnet. Alumina-depleted and alumina-enriched komatiites in the early Archean might be generated by a high degree of partial melting of the layered mantle. Such chemical layering could have been homogenized by the late Archean. This explains the observations that alumina-depleted and alumina-enriched komatiites were generally formed in the early Archean but alumina-undepleted komatiite was erupted in the late Archean.
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References
Arndt NT (1986) Komatiites: a dirty window to the Archean mantle. Terra Cognita 6:59–66
Bence AE, Albee AL (1968) Empirical correction factors for electron microanalysis of silicates and oxides. J Geol 76:382–403
Christensen UR, Yuen DA (1984) The interaction of a subducting lithosphere slab with a chemical or phase boundary. J Geophys Res 86:4389–4402
Gruau G, Arndt NT, Chauvel C, Jahn BM (1986) Large scale compositional heterogeneity of the early Archean mantle. Terra Cognita 6:245
Hart SR, Zindler A (1986) In search of a bulk-earth composition. Chem Geol 57:247–267
Herzberg CT, O'Hara MJ (1985) Origin of mantle periditite and komatiite by pertial melting. Geophys Res Lett 12:541–544
Herzberg CT, Ohtani E (1988) Origin of komatiite at high pressures. Earth Planet Sci Lett 88:321–329
Herzberg CT, Feigenson M, Skuba C, Ohtani E (1988) Majorite fractionation recorded in the geochemistry of peridotites from South Africa. Nature 322:823–825
Irving AJ (1978) A review of experimental studies of crystal/liquid trace element partitioning. Geochim Cosmochim Acta 42:743–770
Ito E, Takahashi E (1987) Melting of peridotite at uppermost lower-mantle conditions. Nature 328:514–517
Jahn BM, Gruau G, Glikson AY (1982) Komatiite of Onverwacht Group, South Africa: REE geochemistry, Sm/Nd age and mantle evolution. Contrib Mineral Petrol 80:25–40
Kato T, Kumazawa M (1986) Incongruent melting of Mg2SiO4 at 20 GPa. Phys Earth Planet Inter 41:1–5
Kato T, Ringwood AE, Irifune T (1987) Majorite partition behaviour and petrogenesis of the Earth's upper mantle. Geophys Res Lett 14:546–549
Kato T, Ringwood AE, Irifune T (1988) Experimental determination of element partitioning between silicate perovskites, garnets and liquids: constraints on early differentiation of the mantle. Earth Planet Sci Lett 89:123–145
Kushiro I (1975) On the nature of the silicate melt and its significance in magma genesis: Regularities in the shift of the liquidus boundaries involving olivine, pyroxene, and silica minerals. Am J Sci 275:411–431
McKay GA, Weill DF (1977) Kreep petrogenesis revisited. Proc 8th Lunar Sci Conf, pp 2339–2355
Nagata Y, Ohtani E, Sawamoto H (1987) Melting and phase relations of pyrolite model under high pressure and high temperature conditions. Abstract of the 28th High Pressure Conference of Japan, Kobe, pp 114–115 (in Japanese)
Nesbitt RW, Sun SS, Purvis AC 61979) Komatiite: geochemistry and genesis. Can Mineral 17:165–186
Nisbet EG, Walker D (1982) Komatiites and the structure of the Archean mantle. Earth Planet Sci Lett 60:103–113
Ohtani E (1984) Generation of komatiite magma and gravitational differentiation in the deep uppr mantle. Earth Planet Sci Lett 67:251–272
Ohtani E (1987) Ultrahigh pressure melting of a model chondritic mantle and pyrolite compositions. In: Manghnani MH, Syono Y (eds) High-pressure research in mineral physics. Am Geophys Union Washington, DC, pp 87–93
Ohtani E, Sawamoto H (1987) Melting experiment on a model chondritic mantle composition at 25 GPa. Geophys Res Lett 14:733–736
Ohtani E, Kato T, Sawamoto H (1986) Melting of a model chondritic mantle to 20 GPa. Nature 322:352–353
Ohtani E, Okada Y, Kagawa N, Nagata Y (1987) Development of a new guide-block system and high pressure and temperature generation. Abstract of the 28th High Pressure Conference of Japan, Kobe, pp 222–223 (in Japanese)
Olsen PL, Yuen DA (1982) Thermochemical plumes and mantle phase transitions. J Geophys Res 87:3993–4002
Palme H, Nickel KG (1985) Ca/Al ratio and composition of the earth's upper mantle. Geochim Cosmochim Acta 49:2123–2132
Richter FM, McKenzie DP (1981) On some consequences and possible causes of layered mantle convection. J Geophys Res 89:425–436
Shannon RD (1976) Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Cryst A32:751–767
Shimizu N, Kushiro I (1975) The partitioning of trace elements between garnet and liquid at high pressures: preliminary experiments. Geophys Res Lett 2:413–416
Smith HS, Erlank AJ (1982) Geochemistry and petrogenesis of komatiites from the Barberton green stone belt, South Africa. In: Arndt NT, Nisbet EG (eds) Komatiites. Allen and Unwin, London, pp 347–397
Sun SS (1987) Chemical composition of Archaean komatiites: implications for early history of the earth and mantle evolution. J Vol Geotherm Res 32:67–82
Takahashi E (1986) Melting of dry peridotite KLB1 up to 14 GPa: implications on the origin of peridotite upper mantle. J Geophys Res 91:9367–9382
Viljoen MJ, Viljoen RP (1969) The geology and geochemistry of the lower ultramafic unit of the Onverwacht Group and a proposed new class of igneous rocks. Geol Soc S Afr Spec Publ 2:55–86
Weill DF, McKay GA (1975) The partitioning of Mg, Fe, Sr, Ce, Sm, Eu and Yb in lunar igneous systems and a possible origin of KREEP by equilibrium partial melting. Proc 6th Lunar Sci Conf, pp 1143–1158
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Ohtani, E., Kawabe, I., Moriyama, J. et al. Partitioning of elements between majorite garnet and melt and implications for petrogenesis of komatiite. Contr. Mineral. and Petrol. 103, 263–269 (1989). https://doi.org/10.1007/BF00402913
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DOI: https://doi.org/10.1007/BF00402913