The origin of ultra-nickeliferous olivine in the Kevitsa Ni-Cu deposit,Lapland,Finland
The mafic-ultramafic Kevitsa Intrusion,located in the Central Lapland greenstone belt,northern Finland,hosts economic Ni-Cu-(PGE) sulfide mineralization in the middle part of the ultramafic lower unit.Two main types of ore are distinguished,namely “normal and “Ni-PGE ore.Olivine in Ni-PGE ore has extremely high Ni contents of up to 14,000 ppm,which is significantly higher than Ni contents of olivine in other mafic-ultramafic igneous rocks globally.Co-existing clinopyroxene and sulfides are also extremely Ni-rich with the latter being represented by a pentlandite-pyrite-millerite paragenesis.The Nicpx/Niolivine is ~0.1-0.2,corresponding to high-T partitioning of Ni between clinopyroxene and olivine.KD of 31 can account for the partitioning of nickel between olivine and the sulfide phase,consistent with magmatic equilibration.These data suggest that olivine,clinopyroxene and sulfides all crystallized from a silicate magma with a very high Ni content ranging from 300–1100 ppm,significantly higher than in the Kevitsa parental magma (<200 ppm Ni).The Ni-PGE ores are spatially associated with komatiitic xenoliths.It is proposed that assimilation within the Kevitsa Intrusion of massive or semi-massive sulfides associated with komatiitic rocks elevated the Ni content of the magma and resulted in the formation of the extremely Ni-rich olivines.
S.H.Yang W.D.Maier E.Hanski M.Lappalainen F.Santaguida S.M(a)(a)tt(a)
Department of Geosciences,P.O.Box 3000,90014 University of Oulu,Finland Shenghong First Quantum Minerals Ltd,FQM FinnEx Oy,99600 Sodankyl(a),Finland
国际会议
贵阳
英文
192-195
2012-06-16（万方平台首次上网日期，不代表论文的发表时间）