Abstract
Phase relations have been determined at one atmosphere and an oxygen fugacity of 10−8 atmospheres for a number of rocks from two differentiated ultrabasic dykes. It is demonstrated that these are consistent with other petrological evidence and that they support the view that the dykes were differentiated mechanically during intrusion. Crystal-liquid relations during the equilibrium crystallization of one of these rocks were determined by electron probe microanalysis. Over part of the temperature range where the three phase assemblage olivine+spinel+liquid exists an “anomalous” relationship was found. Immediately below the liquidus crystallization is normal with the olivine and liquid both becoming relatively enriched in iron as temperature decreases. When spinel starts to crystallize the iron enrichment in the liquid is suppressed and the forsterite content of the olivine actually increases until at lower temperatures a normal trend of iron enrichment is resumed. This phenomenon is tentatively attributed to the crystallization of the spinel under conditions of constant oxygen fugacity.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Anderson, F. W., Dunham, K. C.: The geology of northern Skye. Mem. Geol. Surv. Scotland 1–216 (1966).
Bowen, N. L.: The evolution of the igneous rocks. Princeton: Univ. press 1928.
Brown, G. M.: Melting relations of Tertiary granitic rocks in Skye and Rhum. Mineral. Mag. 33, 533–562 (1963).
—, Schairer, J. F.: Melting relations of some calc-alkaline volcanic rocks. Carnegie Inst. Wash. Year bk. 67, 460–467 (1967).
Darken, L. S., Gurry, R. W.: The system iron-oxygen, I. The wustite field and related equilibrium. J. Amer. Chem. Soc. 67, 1398–1412 (1945).
Drever, H. I., Johnston, R.: The petrology of picritic rocks in minor intrusions, a Hebridean group. Trans. Roy. Soc. Edinburgh 63, 459–497 (1958).
—: A natural high-lime silicate liquid more basic than basalt. J. Petrol. 7, 414–420 (1966).
—: Picritic minor intrusions. In: Ultramafic and related rocks, Wyllie, P. J. ed. p. 71–82. New York: J. Wiley and Sons 1967.
Fudali, R. F.: Oxygen fugacities of basaltic and andesitic magmas. Geochim. Cosmochim. Acta 29, 1063–1075 (1965).
Gibb, F. G. F.: Flow differentiation in the xenolithic ultrabasic dykes of the Cuillins and the Strathaird Peninsula, Isle of Skye, Scotland. J. Petrol. 9, 411–443 (1968).
—: Cognate xenoliths in the Tertiary ultrabasic dykes of south-west Skye. Mineral. Mag. 37, 504–514 (1969).
—, Henderson, C. M. B.: The magmatic oxygen fugacity of an ultrabasic dyke. Contr. Mineral. and Petrol. 30, 119–124 (1971).
Hamilton, D. L., Anderson, G. M.: Effects of water and oxygen pressures on the crystallization of basaltic magmas. In: V2 of Basalts, the Poldervaart treatise on rocks of basaltic composition, H. H. Hess and A. Poldervaart, eds., p. 445–482. New York: Interscience 1967.
Harker, A.: The Tertiary igneous rocks of Skye. Mem. Geol. Surv. Scotland 1–481 (1904).
Muan, A.: Silver palladium alloys as crucible material in studies of low melting iron silicates. Bull. Amer. Cer. Soc. 42, 344–347 (1963).
Mueller, R. F.: System Fe-MgO-SiO2-O2 with applications to terrestrial rocks and meteorites. Geochim. Cosmochim. Acta 29, 967–976 (1965).
Murata, K. J., Richter, D. H.: Chemistry of the lavas of the 1959–60 eruption of Kilauea volcano, Hawaii. U. S. Geol. Surv. Profess. Paper 537-A (1966).
Osborn, E. F.: Role of oxygen pressure in the crystallization and differentiation of basaltic magma. Am. J. Sci. 257, 609–647 (1959).
Presnall, D. C.: The join forsterite-diopside-iron oxide and its bearing on the crystallization of basaltic and ultramafio magmas. Am. J. Sci. 264, 753–809 (1966).
Roeder, P. L., Osborn, E. F.: Experimental data for the system MgO-FeO-Fe2O3-CaAl2Si2O8-SiO2 and their petrologic implications. Am. J. Sci. 264, 428–480 (1966).
Shaw, H. R.: Rheology of basalt in the melting range. J. Petrol. 10, 510–535 (1969).
Speidel, D. H., Nafziger, R. H.: P-T-fO2 relations in the system Fe-O-MgO-SiO2. Am. J. Sci. 266, 361–379 (1968).
Tilley, C. E., Yoder, H. S., Schairer, J. F.: Melting relations of igneous rock series. Carnegie Inst. Wash. Year bk. 67, 450–457 (1967).
Wilshire, H. G.: The Prospect alkaline diabase-picrite intrusion, New South Wales, Australia. J. Petrol. 8, 97–163 (1967).
Wyllie, P. J.: The system CaO-MgO-FeO-SiO2 and its bearing on the origin of ultrabasic and basic rocks. Mineral. Mag. 32, 459–470 (1960).
—: Fusion of Torridonian sandstone by a picrite sill in Soay. J. Petrol. 2, 1–37 (1961).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Gibb, F.G.F. Crystal-liquid relationships in some ultrabasic dykes and their petrological significance. Contr. Mineral. and Petrol. 30, 103–118 (1971). https://doi.org/10.1007/BF00372250
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00372250