PGE rich 2.45 Ga mafic dykes in Northern Finland:implications for the origin of PGE mineralization in the associated layered intrusions
The Karelian craton contains abundant 2.45 Ga mafic dykes that are spatially and temporally related to PGE-mineralized mafic-ultramafic layered intrusions.The mafic dykes include boninites,cumulate textured gabbronorites,Ti-poor tholeiite and Fe-tholeiite.The Nd isotope and trace element geochemistry of the mafic dykes suggests that the tholeiites are derived from a depleted asthenospheric mantle,partially molten in a mantle plume,followed by different degrees of crustal contamination.The mantle source of the boninites and gabbronorites is less clear;They are variably and often highly enriched in incompatible trace elements and have negative εNd (-1 to -3),suggesting either relatively enhanced crustal contamination,or a mantle source in the metasomatised sub-continental lithospheric mantle.Most dyke types show a trend of high Pt and Pd abundances and mantle-like Cu/Pd ratios in the more primitive members,suggesting sulphide undersaturation both at the source and en route to the surface.Sulfide saturation was achieved in the more evolved magmas,and in many cases the sulfides were entrained by the magma,resulting in high Cu and PGE contents,creating some of the world’s most PGE rich basalts.The data indicate that all 4 dyke types are prospective for PGE mineralization.
Fang-Fang Guo Wolfgang D.Maier Jouni Vuollo Hanna Junttila
Department of Geosciences,University of Oulu,P.O.box 3000,FI 90014,Finland Fangfang Geological Survery of Finland,Romaniemi,Finland Department of Geosciences,University of Oulu,P.O.box 3000,FI 90014,Finland
国际会议
贵阳
英文
108-111
2012-06-16（万方平台首次上网日期，不代表论文的发表时间）