Research progress of nickel isotope in high-temperature magmatic system and its implications to ore deposit
The variations of Ni isotopes have been identified as high as 4‰ in high-temperature magmatic systems,which breaks the traditional view that the larger the large number of elements,the smaller the relative isotopic fractionation.The massive isotopic fractionation generated in high-temperature magmatic system may be caused by the superposition of multiple equilibrium isotope fractionation processes and/or dynamic fractionation and therefore has also been applied to magmatic Ni-Cu sulfide deposits.The current understanding of the Ni isotope fractionation mechanism in high-temperature magmatic processes includes:(1)The Ni isotope composition of basalt cannot represent the mantle value.(2)Partial melting of the mantle and recycling of crustal materials result in limited Ni isotope fractionation,and mantle metasomatism is the main reason for the heterogeneity of Ni isotope in the mantle.(3)The involvement of sulfides in high-temperature magmatic systems is the main controlling factor for the Ni isotope changes,especially for the large Ni isotope fractionation identified in high-temperature magmatic sulfide ore-forming systems,for example,the dissolution,crystallization,segregation and interaction with silicate magma of sulfides.At present,the research and application of Ni isotopes in high-temperature geological processes are still in the development stage,and parameters such as isotopic fractionation coefficients and reduced partition function ratios need to be determined.This requires more accurate simulation calculations and more reasonable high-temperature and high-pressure experiments to solve the problem.Uncovering the isotopic fractionation mechanism during mantle metasomatism is expected to accurately identify the mantle rock type and the detailed metasomatic processes.The combination of Cu and Ni isotopes has great potential in the study of metal enrichment mechanisms and geodynamic environments in magmatic Ni-Cu sulfide deposits.
Ni isotopeIsotopic fractionationMantle metasomatismMagmatic Ni-Cu sulfide depositHigh temperature geological processes
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