The behaviour of trace and rare earth elements (REE) during hydrothermal alteration in the Rangan area (Central Iran) |
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| Authors: | A. Parsapoor M. Khalili M.A. Mackizadeh |
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| Affiliation: | 1. Dipartimento di Scienze della Terra e del Mare, Università degli Studi di Palermo, Via Archirafi, 22, 90123 Palermo, Italy;2. UPMC-Sorbonne Universités, Institut des Sciences de la Terre de Paris, 4 place Jussieu, F75005 Paris, France;3. Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Via U. La Malfa, 153, 90146 Palermo, Italy;1. Dipartimento di Scienze della Terra e del Mare, Università degli Studi di Palermo, Via Archirafi, 22, 90123 Palermo, Italy;2. UPMC-Sorbonne Universités, Institut des Sciences de la Terre de Paris, 4 place Jussieu, F75005 Paris, France;3. Servicio Geologico Colombiano, Observatorio Vulcanologico y Sismologico de Manizales, Avenida 12 de Octubre, 15-47 Manizales, Colombia;4. Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Via U. La Malfa, 153, 90146 Palermo, Italy;1. Earth and Environmental Division, Los Alamos National Laboratory, P.O. Box 1663, M.S. J535, Los Alamos, NM 87545, United States;2. Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal H3A 0E8, Canada;3. School of Earth, Atmosphere and Environment, Monash University, 9 Rainforest Walk, VIC 3800, Australia;1. Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;2. China University of Geosciences (Beijing), Beijing 100083, China |
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| Abstract: | The rhyolitic dome in the Rangan area has been subjected to hydrothermal alterations by two different systems, (1) A fossil magmatic–hydrothermal system with a powerful thermal engine of a deep monzodioritic magma, (2) An active hydrothermal system dominated by meteoric water. Based on mineralogical and geochemical studies, three different alteration facies have been identified (phyllic, advanced argillic and silicic) with notable differences in REE and other trace elements behaviour. In the phyllic alteration zone with assemblage minerals such as sericite, pyrite, quartz, kaolinite, LREE are relatively depleted whereas HREE are enriched. The advanced argillic zone is identified by the presence of alunite–jarosite and pyrophyllite as well as immobility of LREE and depletion in HREE. In the silicic zone, most of LREE are depleted but HREE patterns are unchanged compared to their fresh rock equivalents. All the REE fractionation ratios (La/Yb)cn, (La/Sm)cn, (Tb/Yb)cn, (Ce/Ce1)cn and (Eu/Eu1)cn are low in the phyllic altered facies. (Eu/Eu1)cn in both advanced and silicic facies is low too. In all alteration zones, high field strength elements (HFSE) (e.g. Ti, Zr, Nb) are depleted whereas transition elements (e.g. V, Cr, Co, Ni, Fe) are enriched. Geochemically speaking, trace and rare earth elements behave highly selective in different facies. |
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