The Ore Genesis of Kalatongke Cu-Ni Sulfide Deposits,West China:Constrains from Volatile,Petrogeochemical and C-Sr-Nd Isotopic Compositions

摘要

The ore genesis of Kalatongke Cu-Ni sulfide deposits in the Central Asian Orogenic Belt (CAOB) has been investigated based on volatiles and petrogeochemical compositions as well as C-Sr-Nd isotopic compositions.Kalatongke intrusions show similar geochemical characters to coeval Santanghu basalts,implied their genetic relation.Primary magma was produced by 7-8％ partial melting of depleted mantle peridotite,ore-forming parental magma experienced ～15％ of olivine crystallization and crustal contamination.The dominant H2O (av.～92 mol％) with high contents of H2,CO2,H2S and SO2 in volatiles of ore-forming magma suggested a high fO2 condition associated with subduction.Supercritical state of CO2 may play a key role for the enrichment of Cu and Ni elements under mantle high temperature and pressure.Olivine fractional crystallization at depth,selective assimilation of crustal sulfur and high CO2 oxidized volatile media may trigger sulfur saturation and sulfide segregation in the parental magma of the Kalatongke intrusions.PGE depletion in the sulfide ores is most likely due to sulfide retention in the source mantle because of a relatively low degree of partial melting.