Petrogenesis of dunites of the Guli ultrabasic massif (northern Siberian Platform)

Abstract

Abstract New data on silicate melt inclusions in accessory Cr-spinel have given an insight into the physicochemical conditions of petrogenesis of dunites of the Guli massif (northern Siberian Platform). Studies of the inclusions demonstrate the contribution of high-Mg (16-22 wt.% MgO) alkali-picritic and picrobasaltic melts to the crystallization of these ultrabasic rocks. During the intrachamber crystallization of the Guli massif dunites, the composition of magmatic systems evolved from picrite–meimechite (with olivine forming at 1500–1380 °C and Cr-spinel forming at 1420–1360 °C) to picrobasalt. Comparison with well-known associations of ultrabasic igneous rocks has shown that melt inclusions in Cr-spinel from the Guli massif dunites are similar to inclusions in olivine phenocrysts from meimechites in the contents of most petrochemical components and in the distribution of indicator trace and rare-earth elements. In general, the new information on melt inclusions testifies that the Guli massif dunites formed with the participation of high-temperature high-Mg melts similar in composition to meimechite magmas.