Partition of Ni between olivine and sulfide: equilibria with sulfide-oxide liquids

✍ Scribed by M. E. Fleet; N. D. MacRae

• Book ID: 104745414
• Publisher: Springer
• Year: 1988
• Tongue: English
• Weight: 926 KB
• Volume: 100
• Category: Article
• ISSN: 0010-7999
• DOI: 10.1007/bf00371375

✦ Synopsis

The partition of Ni between olivine and monosulfide-oxide liquid has been investigated at 1300-1395 ~ C, f02 = 10-8"9-10 -6"8, andfs2= 10-2"~176 over the composition range 20-79 mol. % NiS. The product olivine compositions varied from Fo98 to Fo59 and from 0.06 to 3.11 wt% NiO. The metal/sulfur ratio of the sulfide-oxide liquid increases with increase in fo2, decrease in fs2, and increase in NiS content. The Ni/Fe exchange reaction has been perfectly reversed using natural olivine and pure forsterite as starting materials. The Fen and NiO contents of olivine from runs equilibrated at the samefo2 andfs~ form isobaric distributions with NiS content, which, to a first approximation, are dependent at constant temperature and total pressure on a variable term, -0.5 log (fsjfo). The Ni/Fe distribution coefficient (KD3) exhibits only a weak decrease from 35 to 29 with increase in fo2 from the IW buffer to close to the FMQ buffer. At fo~ values higher than FMQ, the sulfide-oxide liquid has the approximate composition (Ni,Fe)~ __ xS2 : Kn3 ~ 58. The present [s vs O/(S + O) data define a trend which extrapolates to KD3~20 at 10wt% oxygen in the sulfide-oxide liquid. The compositions of olivine and Ni-Cu sulfides associated with early-magmatic basic rocks and komatiites are consistent, at 1400 ~ C, with a value of -log (foJfs) of about 7.7, which is equivalent to 0.0 wt% oxygen in the hypothesized immiscible sulfideoxide liquid. Therefore, KD3 would not be reduced significantly from the 30 to 35 range for sulfide-oxide liquids with low oxygen contents.