Extreme Closed System Fractionation of Volatile-Rich, Ultrabasic Peralkaline Melt Inclusions and the Occurrence of Djerfisherite in the Kugda Alkaline Complex, Siberia

C. M. B. Henderson1, L. N. Kogarko2 and D. A. Plant1
1 Department of Earth Sciences, University of Manchester, M13 9PL, UK
2 Vernadsky Institute of Geochemistry, Academy of Sciences, Moscow 117975, Russia

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

Mineralogical Magazine; June 1999 v. 63; no. 3; p. 433-438; DOI: 10.1180/002646199548529
© 1999, The Mineralogical Society
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