Magmatic Evolution And Mineralization Of The Segment â…£ Ore-bearing Rock Body Of Jinchuan Nickel-copper Sulfide Deposit

Segment IV of the Jinchuan intrusion is composed mainly of lherzolite, plagioclaselherzolite, peridotite containing pyroxene, and plagioclase peridotite containing pyroxene, thedistribution characteristics of lithofacies reflect the feature of multiple injections of magma.The main ore-bearing lithofacies are lherzolite, and plagioclase lherzolite, different lithofaciesare the products which evolves the homologous magma crystallization differentiation; Basedon the petrography relationships between the minerals of various rock facies，the paper thinkthat the crystallization sequence of the rock-forming minerals in Segment IV is (spinel)olivine，orthopymxene，clinoyroxene and plagioclaseï¼›In the evolution process of magma, themagma both experienced the assimilation and contamination of upper crust material, andexperienced the assimilation and contamination of lower crust materialï¼›By studying on PGEcharacteristics, the total concentrations of PGE in rock and ore samples is low, their dominantelements are PPGE, compared with primitive mantle the PGE is depleted; The PGEdistribution patterns of rock and ore samples belong to the Pt-Pd type, reflecting theirmaterial source is consistent; The Cu/Pd ratio of rock and ore samples are much higher thanthe Cu/Pd ratio of the primitive mantle, moreover, the Cu/Zr ratio of rock and ore samples arelower than the Cu/Zr ratio of the primitive mantle, these features show that the magma hadexperienced minor sulfide segregation, causing the parental magma PGE to be depletedduring magma rising process. Unifying the macroscopic geological feature, the petrology andpetrochemistry fact of the segment IV of the Jinchuan intrusion, comparing with segment II,the authors think that the segment IV and II are the identical rock, and conclude that themineralization process of the segment IV of the Jinchuan intrusion: initial magma (high-Mgbasaltic magma and undepleted PGE)â†'olivine, spinel and pyroxene fractionalcrystallization and assimilation and contaminationâ†'sulfide pre-segregationâ†'metallogenicparent magma(PGE depleted)â†'olivine and pyroxene fractional crystallization andassimilation and contaminationâ†'sulfide secondary segregationâ†'residual metallogenic parentmagma(PGE depleted again)â†'magma ascend and intrude,then crystallization differentiationand mineralization.