Carbonate assimilation in magmas: A reappraisal based on experimental petrology |
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| Authors: | Silvio Mollo Mario Gaeta Carmela Freda Tommaso Di Rocco Valeria Misiti Piergiorgio Scarlato |
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| Institution: | 1. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China;2. Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, ON N2L 3G1, Canada;3. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;4. MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;1. Beijing SHRIMP Center, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, 100037 Beijing, China;2. Institut für Geowissenschaften, Johannes Gutenberg-Universität, Becherweg 21, D-55099 Mainz, Germany;3. Departamento de Geociencias, Universidad de los Andes, Cra 1 No 18A – 70, Bogota, Colombia;4. Research School of Earth Sciences, Australian National University, Canberra, ACT 2601, Australia;5. Departamento de Mineralogía y Petrología, Universidad de Granada, Fuentenueva s/n, 18071 Granada, Spain;6. Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, 18100 Armilla, Granada. Spain;7. Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China;8. Centro de Investigaciones del Petróleo (CEINPET), Washington No169 esq. a Churruca, 12000 Cerro, Ciudad de la Habana, Cuba;9. Science Facilities Department, Imaging and Analysis Center, Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom;1. College of Earth Sciences, Jilin University, Changchun 130061, China;2. Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China;1. Department of Earth and Planetary Sciences, 16 University Avenue, Macquarie University, NSW 2109, Sydney, Australia;2. Institute of Geosciences, J.-J.-Becher-Weg 21, Johannes Gutenberg University, 55099 Mainz, Germany;3. Faculty of Mining and Geology University, Djusina 7, 11000 Belgrade, Serbia;1. Dept of Earth Sciences, Royal Holloway University of London, Egham TW20 0EX, UK;2. Department of Geology, Trinity College Dublin, College Green, Dublin 2, Ireland;3. Department of Sciences, Universita di Roma TRE, L.go S. Murialdo 1, 00146 Roma, Italy;4. Research Laboratory for Archaeology and the History of Art, University of Oxford, Dyson Perrins Building, South Parks Rd, Oxford OX1 3QY, UK;5. Posgrado ESIA-Ticoman, Instituto Politecnico Nacional (IPN), ESIA-Ticomán, Av. Ticomán #600, Mexico, D.F., Mexico;6. GFZ German Research Centre for Geosciences, Potsdam, Germany |
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| Abstract: | The main effect of magma–carbonate interaction on magma differentiation is the formation of a silica-undersaturated, alkali-rich residual melt. Such a desilication process was explained as the progressive dissolution of CaCO3 in melt by consumption of SiO2 and MgO to form diopside sensu stricto. Magma chambers emplaced in carbonate substrata, however, are generally associated with magmatic skarns containing clinopyroxene with a high Ca-Tschermak activity in their paragenesis. Data are presented from magma–carbonate interaction experiments, demonstrating that carbonate assimilation is a complex process involving more components than so far assumed. Experimental results show that, during carbonate assimilation, a diopside–hedenbergite–Ca-Tschermak clinopyroxene solid solution is formed and that Ca-Tschermak/diopside and hedenbergite/diopside ratios increase as a function of the progressive carbonate assimilation. Accordingly, carbonate assimilation reaction should be written as follows, taking into account all the involved magmatic components:CaCO3solid + SiO2melt + MgOmelt + FeOmelt + Al2O3melt → (Di–Hd–CaTs)sssolid + CO2fluidThe texture of experimental products demonstrates that carbonate assimilation produces three-phases (solid, melt, and fluid) whose main products are: i) diopside–hedenbergite–Ca-Tschermak clinopyroxene solid solution; ii) silica-undersaturated CaO-rich melt; and iii) C–O–H fluid phase. The silica undersaturation of the melt and, more importantly, the occurrence of a CO2-rich fluid phase, must be taken into account as they significantly affect partition coefficients and the redox state of carbonated systems, respectively. |
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