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Geoscience ›› 2025, Vol. 39 ›› Issue (01): 96-114.DOI: 10.19657/j.geoscience.1000-8527.2025.003

• Mineral Deposit • Previous Articles     Next Articles

Types and Genesis of Magnetite in the Sijiaying Banded Iron Formation-hosted Iron Deposit, Eastern Hebei Province: Insights into Mechanisms of High-Grade Iron Mineralization

ZHANG Meinuo1(), SHI Kangxing2,3(), QIU Kunfeng1, DENG Jun1   

  1. 1. School of Earth Sciences and Resources,China University of Geosciences (Beijing), Beijing 100083, China
    2. College of Earth Sciences, Hebei GEO University, Shijiazhuang, Hebei 050031, China
    3. Hebei Province Collaborative Innovation Center for Strategic Critical Mineral Research (Hebei GEO University), Shijiazhuang, Hebei 050031, China
  • Online:2025-02-10 Published:2025-02-20
  • Contact: SHI Kangxing

Abstract:

The Sijiaying banded iron formation (BIF)-hosted deposit, located in eastern Hebei Province, is a significant occurrence of iron ore within a suite of Neoarchean low-grade metamorphic rocks of amphibolite-greenschist facies. The metallogeny of the high-grade Fe mineralization at Sijiaying remains a subject of debate. This study presents a comprehensive investigation of the petrology, mineralogy, and geochemistry of ores from the Sijiaying BIF-hosted iron deposit to elucidate their genesis. The deposit predominantly comprises massive high-grade Fe ore and banded low-grade BIF. The ores are characterized by three distinct types of magnetite: First, magnetite from the original sedimentary-metamorphic stage (Mt1), which exhibits a banded distribution and occurs as irregular or rounded granular forms, characterized by the smallest particle size found within the low-grade BIF. Second, magnetite from the hydrothermal alteration stage (Mt2), which manifests as irregular granular configurations and frequently coexists with pyrite, occasionally containing well-developed pyrite grains, predominantly within the low-grade BIF. Third, magnetite from the iron remobilization and re-enrichment stage (Mt3), which appears as subhedral to euhedral granules with well-formed crystal shapes, typically found in massive high-grade Fe ore. Both Mt1 and Mt2 are associated with the magnetite within the banded low-grade BIF, with Mt2 displaying clear characteristics of hydrothermal alteration. Conversely, Mt3 is indicative of magnetite originating from the massive high-grade Fe ore, resulting from remobilization and re-precipitation processes. It is concluded that the high-grade Fe mineralization of the Sijiaying deposit is primarily attributed to the remobilization and re-precipitation processes affecting the iron within the BIF.

Key words: magnetite, mineral geochemistry, high-grade iron mineralization, Sijiaying deposit, Eastern Hebei Province

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