166-7 Decoding Critical Element Transport in Iranian Iron Oxide-Apatite (IOA) Systems: Insights from Petrographic, Elemental, and Novel Analyses of Apatite

Session: Mineralogical Characterization of Economic Resources: From Critical Minerals to Gemstones

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Abstract:

Critical elements are in-demand materials for modern technologies but are subject to supply risks. Among these, rare earth elements (REEs) are important due to their extensive use in advanced technologies and their key role in the transition toward sustainable energy. IOA deposits are important sources of iron, phosphorus, and potentially REEs hosted within apatite minerals. This study examines and compares two IOA metallogenic provinces in Iran: Tarom and Bafq. The aim of this research is to elucidate REE transport and concentration processes in IOA systems through apatite petrography and mineral chemistry. This work uses a novel approach of combining hyperspectral cathodoluminescence (HyCL) with scanning electron microscopy (SEM), as it illuminates geochemical variation that is invisible with all other methods.

The Tarom (42-41 Ma) and Bafq (474-539 Ma) deposits occur in different geologic regions of Iran. A comparative analysis incorporating mineralogy, textures, and geochemistry with previously published research will determine how tectonomagmatic setting governs mineralization style and REE behavior in Iranian IOA deposits. Petrography on apatite from three Tarom deposits (Zaker, Eskand, GolestanAbad) indicates at least three distinct generations, each with a range of REE-bearing mineral inclusions. SEM-HyCL analysis revealed diverse geochemical textures including coupled dissolution-reprecipitation, patchy zoning, oscillatory zoning, and hydrothermal brecciation. The main activators identified in SEM-HyCL spectra that correspond to variations in texture include Nd³⁺, Ce³⁺, Sm³⁺, Eu³⁺, Dy³⁺, and Mn²⁺. These results reflect dynamic fluid histories at each deposit, and REE behavior is quantified in apatite and its inclusions by laser ablation inductively coupled plasma mass spectrometry.

Among the Tarom deposits, Zaker and Eskand experienced similar fluid evolution, as shown by similar HyCL spectra, dominant dissolution-reprecipitation textures, and Ca-Fe alteration assemblages. GolestanAbad has limited apatite occurrence, pervasive alkalic alteration, and oscillatory zoning in associated plagioclase, which indicate better preservation of magmatic textures. In two Bafq deposits (Esfordi, Gazestan), four apatite generations with similar parageneses were identified, suggesting similar fluid histories to the deposits of Tarom. Based on the SEM-HyCL data from the Tarom province and the first pass petrography from the Bafq deposits, we suggest both sets of deposits, though temporally distinct, underwent similar complex magmatic-hydrothermal processes likely related to emplacement and post-emplacement tectonism.  

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10595

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