Geochemical characteristics and genetic analysis of BIF iron deposit background of Xincai iron deposit in He'nan Province

The Xincai iron deposit is located in the middle part of the Wuyang-Huoqiu iron ore belt on the southern margin of the North China Craton.The ore body is hosted in the Late Archean Taihua Group metamorphic rock series.The iron ore body is mainly lamellar and partially lenticular.The ore structure is mainly banded, with a small amount of disseminated and massive ores.iron ore is mainly composed of TFe₂O₃ and SiO₂, followed by MgO and CaO, and Al₂O₃ and others such as Na₂O, K₂O, P₂O₅, TiO₂ and MnO are mostly less than 0.1%。Trace and rare earth element analytical results show that large ionic lithophile element such as Sr, high field strength elements such as Nb, Ta, Zr, Hf and Ti are significantly depleted, in addition, Rb, U, La, Pb, Eu elements are abnormal, and the average Ti/V ratio is 24.13, the total amount of rare earth elements is relatively low, and the average ∑REE is 12.8×10^-6.After being standardized by PAAS, iron ore shows enrichment in light rare earth elements ((La/Yb) _PAAS=0.43~0.79, average 0.55), with obvious La positive anomaly (La/La_PAAS^* average 1.15), Eu positive anomalies (Eu/Eu^* average 2.88), Y abnormalities (Y/Y_PAAS^* average 1.68), and weak Ce negative anomalies (Ce/Ce_PAAS^* average 0.90).A relatively high Y/Ho value (average of 44) indicates that iron-bearing formation was formed in a relatively hypoxic palaeo-marine environment, and the ore-forming materials were mainly derived from the mixing of high-temperature hydrothermal fluids and seawater associated with volcanic activity on the sea floor.The results for the ore-bearing amphibolite analysis and the tectonic setting for the formation of the orebodies show that the protolith of amphibolite should be a post-arc basin basalt, which represents the tectonic setting of the amphibolite formed in the back-arc basin.The tectonic environment of the amphibolite also basically represents the tectonic environment when the iron-bearing formation was deposited in this area。According to the comprehensive analysis, Xincai iron mine belongs to Algoma type BIF closely related to volcanic activities in the back-arc basin.