The genetic link between iron oxide-apatite and iron skarn mineralization in the Beizhan deposit, Western Tianshan, NW China: Evidence from magnetite and gangue mineral geochemistry

Hengxu Li,Zhaochong Zhang,Bingxiang Liu,Yilun Jin,M Santosh

doi:10.1016/j.jseaes.2022.105460

Hengxu Li, Zhaochong Zhang + Show 3 more

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https://doi.org/10.1016/j.jseaes.2022.105460

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Abstract

• We identify coexisting IOA ore and iron skarn ore in the Beizhan deposit. • IOA and iron skarn ore could form from a single magmatic-hydrothermal system. Multiple types of deposits could form from a single magmatic hydrothermal system. Thus, identification of the temporal, spatial and genetic link among different styles of deposits is crucial to understand the evolution of magmatic-hydrothermal systems and helpful in ore deposit exploration. Iron oxide-apatite (IOA) ores sometimes coexist with iron skarn ores in the same region, but whether these two iron ore styles could form from the single magmatic-hydrothermal system remains poorly understood. The Beizhan deposit is the largest-scale iron deposit (468 Mt, with an average of 41% Fe) in the Awulale Metallogenetic Belt (AMB) in Western Tianshan, and was previously considered to be submarine volcanic-hosted iron deposit or iron skarn deposit. In this study, we identify coexisting IOA ore and iron skarn ore in the orebody proximal to a dioritic-granitic intrusion in the Beizhan deposit. Combined with the geochemistry of magnetite and gangue minerals, we suggest that the IOA ores are consistent with formation from a high-temperature hydrothermal fluid sourced from a dioritic magma. In contrast, the iron skarn mineralization originated from a relatively low-temperature and more evolved hydrothermal fluid compared with the IOA ores. We propose the consecutive precipitation of an evolving magmatic-hydrothermal system during the two stages of iron mineralization at Beizhan, that resulted through compositional evolution of the fluid during magma differentiation. The coexisting two ore types identified in the Beizhan deposit provides insights into the evolution of the intermediate-felsic magmatic-hydrothermal systems and the genetic model of the similar ore type associations in the other deposits.

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