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The Longzhoushan and Ertan basalts in the Pan-Xi area were generated by relatively low degrees of partial melting (< 7%), during which Ir, Ru, and Rh are compatible while Pt and Pd are incom- patible. Most of these samples have high PGE con- centrations and much higher Pd/Ir and Cu/Pd ratios than those of primitive mantle. A small amount of sulfides (~0.007%) remained in the mantle source during partial melting, whereas part of the magmas reached sulfide saturation and segregated PGE-rich sulfides (~0.020%―0.033%) during ascent period. Osmium, Ir, and Pt could form platinum-group metal- lic alloys hosted in chromites or sulfides during frac- tional crystallization process, leading to the decoup- ling of Pt and Pd contents and considerable varia- tions of Ir contents. Sulfides segregated from the basaltic magmas may provide important material sources for the formation of the Cu-Ni-PGE deposits (mineralization) in the mafic-ultramafic intrusions near the magma conduits.
The Longzhoushan and Ertan basalts in the Pan-Xi area were generated by relatively low degrees of partial melting (<7%), during which Ir, Ru, and Rh are compatible while Pt and Pd are incompatible. Most of these samples have high PGE con- centrations and much higher Pd / Ir and Cu / Pd ratios than those of primitive mantle. A small amount of sulfides (-0.007%) remained in the mantle source during partial melting, but part of the magmas reached sulfide saturation and Segregated PGE-rich sulfides (~ 0.020% -0.033%) during the same period. Osmium, Ir, and Pt could form platinum-group metal- hosted rare earths in chromites or sulfides during frac- tional crystallization process, leading to the decoupling of Pt and Pd contents and able varia tions of Ir contents. Sulfides segregated from the basaltic magmas may provide important material sources for the formation of the Cu-Ni-PGE deposits (mineralization) in the mafic-ultramafic intrusions near the magma conduits.