Metallogenic differences between sedimentary metamorphic iron deposits in the Luanxian and Qianxi groups in the eastern Hebei, China: Constraints from the chemical compositions of magnetites

The Luanxian and Qianxi groups are key ore-hosting strata for the Banded Iron Formation (BIF) deposits in the eastern Hebei, with obviously different metallogenic characteristics. In this paper, by taking typical representatives of the Sijiaying and Shuichang iron deposits as the research object, we have carried out a comparative study on the petrography and magnetite geochemistry of these two deposits, and have revealed main influencing factors of the metallogenic differences between them. The results show that most ores of both the Sijiaying and Shuichang iron deposits have banded structure. Magnetites of the Sijiaying deposit occurred in relatively fine grains, associated with actinolite and amphibole. They have relatively high contents of Mn, Cu, and Zn. Magentites of the Shuichang deposit occurred in relatively coarse grains, associated with pyroxene. They have relatively high contents of Al, Ti, Sn and relatively high Ti/V ratios. It is believed that the Sijiaying iron deposit was formed in a place relatively close to a submarine hydrothermal source and had experienced relatively low metamorphism. Due to the relatively small proportion of metamorphic iron-bearing silicate minerals in the ore, the influence on the proportion of the magnetite mineral phase is also small. Overall, the original sedimentation is the main influencing factor controlling the scale and grade of sedimentary metamorphic iron ores of relevant deposits in the eastern Hebei.