Extremely low PGE concentrations of the Permian continental flood basalts in the Tarim Basin,northwest China:Implication for the evolution of the Tarim Large Igneous Province

摘要

Permian continental flood basalts (CFB) in the Tarim Large Igneous Province (TLIP) possess extremely low PGE concentrations (ΣPGE = 0.051–0.723 ppb).They exhibit a marked increase in Cu/Pd ratios (>105) albeit with a narrow range of lower Pd/Ir ratios (<50),indicating that their parent magmas were significantly depleted in chalcophile elements.The Tarim CFB magmas are estimated to have formed by <5％ partial melting of the mantle source.The calculated SCSS indicate that they were probably S-saturated during very low-degree partial melting,leaving a substantial volume of residual sulfide in the source region.The degree of partial melting should play an important role on the PGE geochemistry and potential PGE–(Ni–Cu) ore deposits in the TLIP.