西昆仑老并铁矿床磁铁矿矿物化学组成特征及其对成矿作用的约束OA

The Taxkorgan area is an important iron metallogenic belt in western China.The Laobing iron de-posit,one of the typical deposits in this belt,is characterized by the assemblage of magnetite,gypsum and sul-fides,serving as an ideal proxy for investigating the iron mineralization processes in this region.Based on de-tailed field geological investigation,this study presents LA-ICP-MS in situ trace element analyses of three types of magnetite with different occurrences from the Laobing iron deposit,aiming to constrain the ore-forming mate-rial sources,physicochemical conditions and deposit genesis.The results show that the three types of magnetite display consistent trace element spider diagram patterns,which are comparable to those of high-temperature hy-drothermal deposits,indicating that the ore-forming materials were derived from submarine high-temperature hydrothermal fluids.The(Al+Mn)-(Ti+V)geothermometer and Ga-MgO diagram indicate that Mag-1 and Mag-2 crystallized at approximately 300℃,whereas Mag-3 was modified by post-ore metamorphism,recording high-er re-equilibration temperatures.The pronounced enrichment of Al,Ti and V,together with elevated Ni/Cr ra-tios and low Ti/V ratios in magnetite,jointly suggest crystallization under relatively reducing conditions,with oxygen fugacity exhibiting a systematic decrease from Mag-1 to Mag-3.The V+Ti and Al+Mn+Ca contents of magnetite from the Laobing deposit are significantly higher than those of BIF-type magnetite,while being more comparable to hydrothermal-type magnetite.Combined with the presence of abundant gypsum-bearing layers re-lated to marine sedimentation in the mining area,this study proposes that the Laobing deposit formed in a sub-marine high-temperature hydrothermal system during the Early Cambrian,experiencing early submarine hy-drothermal iron precipitation and late restricted basin gypsum-salt deposition,followed by post-ore regional metamorphic overprinting.