The origin and evolution of skarn-forming fluids from the Phu Lon deposit,northern Loei Fold Belt,Thailand: Evidence from fluid inclusion and sulfur isotope studies |
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| Authors: | Teera Kamvong Khin Zaw |
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| Institution: | 1. Deep Exploration Technology Cooperative Research Centre (DET CRC), University of Adelaide, North Terrace, SA 5005, Australia;2. Centre of Tectonics, Resources and Exploration (TRaX), School of Earth and Environmental Sciences, University of Adelaide, North Terrace, SA 5005, Australia;3. Teale & Associates Pty Ltd., 82 Prospect Road, Prospect, SA 5082, Australia;4. Adelaide Microscopy, University of Adelaide, North Terrace, SA 5005, Australia;1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;2. Department of Geological Sciences, Indiana University, Bloomington, IN 47405, USA;3. Institute of Geological Research, China University of Geosciences, Beijing 100083, China;4. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;1. CODES ARC Centre of Excellence in Ore Deposits, University of Tasmania, Tasmania 7001, Australia;2. Indochine Mining (Cambodia) Ltd., 454 Street 2003, Sang Kat Kakab, Khan Dong Kor, Phnom Penh, Cambodia;3. School of Earth Sciences, University of Melbourne, Victoria 3010, Australia;4. AIRIE Program, Department of Geosciences, Colorado State University, Fort Collins, CO 80523-1482, United States;1. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China;2. Bayerisches Geoinstitut, University of Bayreuth, Bayreuth 95440, Germany;3. Geological Survey of China University of Geosciences, Wuhan 430074, China |
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| Abstract: | The Phu Lon skarn Cu–Au deposit is located in the northern Loei Fold Belt (LFB), Thailand. It is hosted by Devonian volcano-sedimentary sequences intercalated with limestone and marble units, intruded by diorite and quartz monzonite porphyries. Phu Lon is a calcic skarn with both endoskarn and exoskarn facies. In both skarn facies, andradite and diopside comprise the main prograde skarn minerals, whereas epidote, chlorite, tremolite, actinolite and calcite are the principal retrograde skarn minerals.Four types of fluid inclusions in garnet were distinguished: (1) liquid-rich inclusions; (2) daughter mineral-bearing inclusions; (3) salt-saturated inclusions; and (4) vapor-rich inclusions. Epidote contains only one type of fluid inclusion: liquid-rich inclusions. Fluid inclusions associated with garnet (prograde skarn stage) display high homogenization temperatures and moderate salinities (421.6–468.5 °C; 17.4–23.1 wt% NaCl equiv.). By contrast, fluid inclusions associated with epidote (retrograde skarn stage) record lower homogenization temperatures and salinities (350.9–399.8 °C; 0.5–8 wt% NaCl equiv.). These data suggest a possible mixing of saline magmatic fluids with external, dilute fluid sources (e.g., meteoric fluids), as the system cooled. Some fluid inclusions in garnet contain hematite daughters, suggesting an oxidizing magmatic environment. Sulfur isotope determinations on sulfide minerals from both the prograde and retrograde stages show a uniform and narrow range of δ34S values (?2.6 to ?1.1 ‰ δ34S), suggesting that the ore-forming fluid contained sulfur of orthomagmatic origin. Overall, the Phu Lon deposit is interpreted as an oxidized Cu–Au skarn based on the mineralogy and fluid inclusion characteristics. |
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