Rare Earth Elements Mineralization In The Arya Jonoub Iron Oxide-Apatite Deposit , Kashmar-Kerman Belt

The Arya Jonoub iron oxide–apatite (IOA) deposit, located in the southeastern Kashmar–Kerman tectono-magmatic belt in Central Iran, is hosted by a Lower Cambrian volcano-sedimentary sequence and dioritic intrusions formed in a continental arc geodynamic setting linked to Paleo-Tethyan subduction. Despite well-documented IOA deposits in the Bafq district, detailed studies on Arya Jonoub are limited. This study applies an integrated petrographic, mineralogical, and geochemical approach to investigate paragenesis, fluid evolution, and REE enrichment mechanisms. Two-stage mineralization is identified: Stage I (Iron Mineralization) is characterized by Ti-poor magnetite and fluorapatite associated with sodic-calcic metasomatism, with allanite1 as a primary REE mineral (13–20% Ce, up to 10% La). Stage II (Hydrothermal REE Enrichment) shows a late-stage hydrothermal overprint, with ΣREE concentrations up to 1.8 wt.%. Geochemical data exhibit highly fractionated Light REE (LREE) patterns and negative Eu anomalies. Secondary minerals include synchysite (from allanite alteration) and yttriaite-Dy. REE mineralization reflects a transition from magmatic–hydrothermal to late hydrothermal conditions. REE elements, originally sourced from calc-alkaline magmas in apatite and allanite, were remobilized by oxidizing fluids and transported as carbonate–REE complexes, coinciding with magnetite martitization. Elevated La/Yb and Ce/Y ratios are key geochemical indicators for exploring REE-enriched iron deposits in arc-related settings.