Geochemistry, U-Pb zircon geochronology, and Fe isotopes of the Shanzhuang banded iron formation in the North China Craton: Implications for genesis and depositional environment

• DOI: 10.1016/j.oregeorev.2023.105541
• Publication Date: 2023-06-15T16:18:07Z
• Authors: Yan Zhang; Xuefeng Yu; Yangming Hu; Yuqin Sun; Jingxiang Tian; Xiaowei Li; Dapeng Li; Ke Geng; Qiang Liu; Pengfei Wei
• Keywords: Banded iron formation; Detritus; Hornblende; Geochronology

The Shanzhuang banded iron formation (BIF) occurs in the Shancaoyu Formation, Taishan Group, western Shandong Province (WSP), eastern North China Craton (NCC). We constrained BIF depositional age of ∼2.50 Ga based on zircon U-Pb dating leptynite interlayers and cross-cutting metagranitoid. After deposition, was subsequently metamorphosed into amphibolite facies at 2.50–2.45 Ga. According to different mineral assemblages, Fe ores can be divided three types: magnetite + quartz ± hornblende (type-1 ore), garnet hematite (type-2 (type-3 ore). In Post-Archean Australian Shale (PAAS)-normalized rare earth element yttrium (REY) patterns, ore types show consistent flat REY curves. All have moderate ƩREY concentrations (27.24–143 ppm), (La/Yb)N values 0.29–2.31, significant positive Eu anomalies (1.05–3.47), slightly negative or Ce (0.87–1.26), Y (1.16–1.48), no apparent fractionation between light REEs (LREEs) heavy (HREEs), indicating mixing hydrothermal fluid seawater. similar patterns isotopes (0.47–1.02‰) suggest a certain amount continental detritus incorporated during precipitation phases Neoarchean-Paleoproterozoic oceans. post-depositional metamorphism did not significantly affect original geochemical signature BIF. are highly pure chemical sediments, but type-1 is relatively more representative sedimentary composition. By contrast, type-3 tends higher δ56Fe ratios (0.74–1.02‰) lower δEu (1.27–1.97‰), implying substantial alteration. deposit an Algoma-type BIF, surrounding rock consists pyroclastic materials. Our model indicates that probably deposited redox stratified paleo-ocean environment.