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Published March 1971 | public
Journal Article

Experimental Studies of Igneous Rock Series: The Kungnat Syenite Complex of Southwest Greenland


The melting relationships of five rocks from the alkaline igneous complex at Kungnat, southwest Greenland, were determined in the presence of 25 wt percent water at pressures to 3 kbar. Run durations varied between 4 and 27 days. The rocks studied are samples from the two layered syenite bodies comprising the complex and from late granite sheets intruding the syenites. The experimental results are consistent with the petrogenetic hypothesis that there were four magma portions tapped from an already differentiated magma chamber, with each subsequently differentiating along independent paths after emplacement. They suggest that the magmas were emplaced at low water pressures at temperatures about 1,000°C, with water pressure reaching about 1.5 kbar in the stages of crystallization when amphibole was precipitated as reaction rims around pyroxenes. The phase relationships in the syenites differ from those previously reported for calc-alkaline plutonic series from tonalite to granite mainly by (1) the wide temperature interval for crystallization of two feldspars (feldspars did not reach equilibrium compositions) and (2) the absence of amphibole through the melting interval because of the low dissociation temperature of the amphibole. All rocks investigated are at least 75 percent melted at temperatures 100°C above the solidus.

Additional Information

© 1971 University of Chicago Press. Manuscript received May 22, 1970; revised June 17, 1970. We are grateful for the support by National Science Foundation grants GA-923 and GA-10459, and for some assistance from the Advanced Research Projects Agency grant to the Division of Physical Sciences; to the Greenland Geological Survey for the rock specimens, and to B.G.J. Upton for a critical review of manuscript drafts and helpful discussions about the field relationships and petrogenesis of these rocks. Dr. Upton should not be held responsible for our interpretations of the experimental data.

Additional details

August 23, 2023
October 17, 2023