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Abstract
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The Lake Siah iron±apatite deposit is situated in the Bafq Mining District (BMD), Central Iran. The iron±apatite orebodies are hosted by succession of rhyolite, rhyolitic tuff, trachyandesite, and andesite with Lower Cambrian age. The host rock has undergone widespread alteration and mineralization stages includes Na (albite-quartz), followed by Na-Ca (albite-calcite-amphibole-magnetite±quartz±epidote), magnetite-apatite, K (biotite±K-feldspar), hydrolytic (sericite-quartz) and argillic (kaolinite-montmorillonite±dickite), respectively. Electron microprobe analyses (EPMA) from magnetite and hematite have significant variations of trace elements. Based on Ni/Cr+Mn and Ca+Al+Mn versus Ti+V diagrams, majority of magnetite samples is belong to Kiruna-type deposits. At least, three generation of fluid inclusions, including solid-bearing (L+V+S) (Type I), liquid-rich (L+V) (Type II-A), vapor-rich (L+V) (Type II-B), and liquid or vapor mono-phase (Type III), are recognized in quartz and apatite. The solid-bearing fluid inclusions in quartz completely homogenized at temperatures of 150 to >530 °C with salinities of 30 to 58 wt% NaCl equiv. Liquid-rich fluid inclusions in apatite homogenized to a liquid phase at 175 to 210 °C, whereas the vapor-rich fluid inclusions homogenized to a vapor at 335 to 350 °C. Oxygen isotope were carried out on quartz and magnetite. The hydrogen and oxygen isotopic compositions of quartz (δ18Ofluid values of 7.57 to 11.04‰) show that with progress in time the ore-forming solutions gradually evolved from a magmatic to meteoric-dominated source.
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