gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/002646199548529 Letter Extreme Closed System Fractionation of Volatile-Rich, Ultrabasic Peralkaline Melt Inclusions and the Occurrence of Djerfisherite in the Kugda Alkaline Complex, Siberia Henderson C. M. B. 1 Kogarko L. N. 2 Plant D. A. 1 Department of Earth Sciences, University of Manchester, M13 9PL, UK Vernadsky Institute of Geochemistry, Academy of Sciences, Moscow 117975, Russia 6 1999 63 3 433 438 2 3 1999 1 4 1999 Copyright © 1999, The Mineralogical Society 1999 Abstract

Djerfisherite [K6(Cu,Fe,Ni)25S26Cl] has been found as a daughter mineral in melt inclusions in melilite from a Kugda melilitolite. The inclusion mineral assemblage includes pyrrhotite, pentlandite, forsterite, diopside, monticellite, phlogopite, wollastonite, nepheline, sodalite, combeite, calcite, Na-K-Ca carbonate, and hydrated calcium silicates. The djerfisherite is Ni-rich rather than Cu-rich consistent with an ultimate upper mantle magma source. The djerfisherite-bearing assemblage formed from primary carbonate/alkali-rich, melilititic melt inclusions which underwent extreme, closed-system, magmatic to postmagmatic fractionation over a temperature range of >1000° to <500°C.

 Keywords fractionation peralkaline inclusions djerfisherite Kugda Siberia