Depth-related variation of tourmaline in the breccia pipe of the San Jorge porphyry copper deposit,Mendoza, Argentina |
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| Institution: | 1. Dipartimento Scienze della Terra, Sapienza Università di Roma, Piazzale Aldo Moro, 5, I-00185 Roma, Italy;2. Dipartimento Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, Cagliari, Italy;3. CNR-Istituto di Geologia Ambientale e Geoingegneria, Sede Secondaria di Cagliari, via Marengo 2, 09123 Cagliari, Italy;4. Dipartimento Chimica e Farmacia, Università degli Studi di Sassari, via Piandanna 4, 07100 Sassari, Italy;5. CNR-Istituto di Geologia Ambientale e Geoingegneria, Sede Secondaria di Roma “Sapienza”, Piazzale Aldo Moro 5, I-00185 Roma, Italy;6. Department of Geosciences, Swedish Museum of Natural History, Box 50007, SE-10405 Stockholm, Sweden;1. Departamento de Geología, División de Ciencias Exactas y Naturales, Universidad de Sonora, Blvd. Rosales y L. Encinas, Hermosillo, Sonora 83000, México;2. Estación Regional del Noroeste, Instituto de Geología, Universidad Nacional Autónoma de México. L.D. Colosio S/N y Madrid, Col. Los Arcos, Hermosillo, Sonora 83240, México;3. GEO Digital Imaging de México, S.A. de C.V., Hermosillo, Sonora, México;1. China University of Geosciences, Beijing 100083, China;2. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;3. Department of Earth Sciences, Kunming University of Science and Technology, Kunming 650093, China;1. School of Earth and Ocean Sciences, University of Victoria, Victoria, BC, Canada;2. Department of Biology, University of Victoria, Victoria, BC, Canada;1. Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China;2. Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China;3. Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, University of Chinese Academy of Sciences, Beijing 100029, PR China;4. Key Laboratory of Computational Earth Dynamics, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China;5. Innovation Academy for Earth Sciences, CAS, Beijing 100029, PR China;6. University of Chinese Academy of Sciences, Beijing 100049, PR China;7. Development and Research Center of China Geology Survey, Beijing 100037, China;1. GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany;2. Beralt Tin & Wolfram (Portugal) S.A., Barroca Grande, 6225-051 Castelo Branco, Portugal;3. Institute of Earth Sciences (ICT), Pole of University of Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal;4. Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA;5. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton T6G2E3, Canada |
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| Abstract: | The San Jorge porphyry copper deposit in Mendoza, Argentina in some parts contains breccia pipes that are strongly enriched with tourmaline of the dravite–schorl solid solution series with some quartz, muscovite, orthoclase, kaolinite, Cu sulfides and arsenopyrite. The overall composition of tourmaline is rather homogeneous with an intracrystalline variation of the Fe/Mg ratio reflected by its texture, its core-rim zonation of tourmaline and by the statistical variation of the Fe/Mg ratio. The depth-related intracrystalline changes are best interpreted as a hydrothermal collapse breccia which formed as a result of the reaction of primary hydrothermal B–Fe-enriched fluids with the country rocks enriched in Mg. The chemical composition attests to only small-scale interaction of tourmaline with silicate fragments within the tourmaline breccia itself. Tourmaline as one of the ultrastable heavy minerals in stream sediment offers a potential tool to discriminate between Cu-bearing and barren breccia pipes, using the Fe/Mg ratio of the boron silicate for distinction. Fertile breccias reveal a significantly better correlation between Fe and Mg than barren tourmaline breccias. |
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