Abstract
Laboratory experiments near 1450° C at 1 bar (QFM) on komatiite bulk composition show olivine and liquid in cumulus textures which evolve with experiment duration. Orthocumulus texture with settled olivine crystals separated by liquid matrix is developed within a day. Experiments quenched after a few days to a week show a progression of textures which include development of columns of olivine crystals separated by channels of liquid. Olivine grain sizes increase with the cube root of time suggesting that dissolution and reprecipitation of olivine may be involved in the organization into columns and channels. Experiments quenched after two weeks have well developed adcumulus texture. The basal polycrystalline granular olivine aggregate forms from the decay of the olivine columns. Melt expulsion from the aggregate can be virtually complete, leaving 1% or less of the melt originally present.
Buoyancy-driven compaction of olivine is not the mechanism responsible for this textural evolution because the final basal aggregate sometimes contains vesicles. An addition proof of the inadequacy of buoyancy is provided by raising the crucible slightly above the thermal symmetry point of the furnace. The aggregate then compacts on top of a crystal-free liquid. The thermal gradients above and below the furnace hot spot are thought to be primarily responsible for the olivine redistributions observed. Diffusion of olivine components in the liquid is driven along a saturation gradient resulting from the temperature gradient. The process, called thermal migration in geological literature, is essentially the same as traveling solvent zone refining in metallurgy. Differential solubility and Soret fractionation both contribute to olivine redistribution to the cold region of the crystal-liquid aggregate. There may be some applications of these results to natural cumulate rock petrogenesis.
Similar content being viewed by others
References
Buchwald VF (1987) Thermal migration III: its occurrence in Cape York and other iron meteorites. Meteoritics 22:343–344
Buchwald VF, Kjer T, Thorsen KA (1985) Thermal migration I: or how to transport iron sulfide in solid iron meteorites. Meteoritics 20:617–618
Campbell IH (1977) Some problems with cumulus theory. Lithos 11:311–321
Gundel P, Buchwald VF, Kjer T, Thorsen (1986) Thermal migration II: small temperature gradients. Meteoritics 21:383–384
Hess HH (1960) Stillwater igneous complex, Montana, a quantitative mineralogical study. Geol Soc Amer Mem 80
Hofmann AW (1980) Diffusion in natural silicate melts: a critical review. In: Hargraves RB (ed) Physics of Magmatic Processes. Princeton Univ Press, pp 385–417
Irvine TN (1980) Magmatic infiltration metasomatism, double-diffusion, fractional crystallization, and adcumulus growth in the Muskox intrusion and other layered intrusions. In: Hargraves RB (ed) Physics of Magmatic Processes. Princeton Univ Press, pp 325–383
Jurewicz SR, Jurewicz AJG (1986) Distribution of apparent angles on random sections with emphasis on dihedral angle measurements. J Geophys Res 91:9277–9282
Kingery WD, Bowen HK, Uhlmann DR (1976) Introduction to Ceramics, 2nd edn. John Wiley and Sons, NY New York, pp 526–530
Langmuir CH (1988) Geochemical consequences of the solidification of magma chambers through in situ crystallization in a boundary layer. Nature (in press)
Lesher CE (1986) Effects of silicate liquid composition on mineralliquid element partitioning from Soret diffusion studies. J Geophys Res 91:6123–6141
Lesher CE, Walker D (1986) Solution properties of silicate magmas from thermal diffusion studies. Geoch Cosmoc Acta 50:1397–1411
Lesher CE, Walker D (1987) Cumulate maturation. EOS 68:429
Lesher CE, Walker D (1988) Cumulate compaction and melt migration in a temperature gradient. J Geophys Res 93 (in press)
Masuda Y, Watanabe R (1980) Ostwald ripening processes in the sintering of metal powders. In: Kuczynski GC (ed) Sintering Processes. Mater Sci Res 13. Plenum Press, New York, pp 3–21
McBirney AR, Noyes RM (1979) Crystallization and layering of the Skaergaard intrusion. J Petrol 20:487–554
Morse SA (1982) Adcumulus growth of anorthosite at the base of the lunar crust. J Geophys Res 87:A10-A18
Morse SA (1986) Convection in aid of adcumulus growth. J Petrol 27:1183–1214
Pfann WG (1958) Zone melting. Wiley, NY, 236 pp
Roeder PL, Emslie RF (1970) Olivine-liquid equilibrium. Contrib Mineral Petrol 29:275–289
Sack RO, Walker D, Carmichael ISE (1987) Experimental petrology of alkalic lavas at 1 atmosphere: constraints on cotectics of multiple saturation in natural basic lavas. Contrib Mineral Petrol 96:1–23
Takahashi E (1986) Melting of a dry peridotite KLB-1 up to 14 GPa: implication on the origin of peridotitic upper mantle. J Geophys Res 91:9367–9382
Toramaru A (1985) Melt segregation under temperature gradient. Abstract at IASPEI meeting, Tokyo, p 541
Wager LR (1963) The mechanism of adcumulus growth in the layered series of the Skaergaard intrusion. Min Soc Amer Spec Paper 1:1–9
Wager LR, Brown GM (1968) Layered Igneous Rocks. Oliver and Boyd, Edinburgh, 558 pp
Walter D, Agee CB (1987) Novel (?) compaction mechanism for ureilite meteorites. Meteoritics 22:521
Walker D, Agee CB (1988) Ureilite compaction. Meteoritics 23 (in press)
Walker D, DeLong SE (1982) Soret separation of MORB magma. Contrib Mineral Petrol 79:231–240
Walker D, Lesher CE, Hays JF (1981) Soret separation of lunar liquid. Proc Lunar Planet Sci Conf 12th:991–999
Walker D, Jurewicz S, Watson EB (1985) Experimental observation of an isothermal transition from orthocumulus to adcumulus texture. EOS 66:362
Whitman WG (1926) Elimination of salt from sea-water ice. Amer J Sci 5th Ser 211:126–132
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Walker, D., Jurewicz, S. & Watson, E.B. Adcumulus dunite growth in a laboratory thermal gradient. Contr. Mineral. and Petrol. 99, 306–319 (1988). https://doi.org/10.1007/BF00375364
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00375364