The maximum possible celadonite content in muscovite under given external conditions is realized in K-feldspar-bearing rocks, and decreases with rising temperature. The buffered assemblage is stable in harzburgite compositions for relatively moderate amounts of Al2O3 (>1.8 wt.%) and is widespread in lherzolites, where it occurs together with diopside or, in a narrow temperature field, with tremolite. The distribution coefficient of the exchange reaction for Tschermak substitution between muscovite and chlorite varies greatly not only with temperature but also with the extent of this substitution in the two minerals because of their strong deviation from ideality. Cogenetic Dykes the Key to Identifying Diverse Magma Batches in the Assembly of Granitic Plutons, Fo and Ni Relations in Olivine Differentiate between Crystallization and Diffusion Trends, Evidence for Multi-stage Melt Transport in the Lower Ocean Crust: the Atlantis Bank Gabbroic Massif (IODP Hole U1473A, SW Indian Ridge), Generation of Calc-Alkaline Magmas During Crystallization at High Oxygen Fugacity: An Experimental and Petrologic Study of Tephras from Buldir Volcano, Western Aleutian Arc, Alaska, USA, Periodic mixing of magmas recorded by oscillatory zoning of the clinopyroxene macrocrysts from an ultrapotassic lamprophyre dyke, https://doi.org/10.1093/petrology/26.2.449, Receive exclusive offers and updates from Oxford Academic. Padron-Navarta JA, Lopez Sanchez-Vizcaino V, Hermann J, Connolly JAD, Garrido CJ, Teresa Gomez-Pugnaire M et al. When both Mg-Fe and Tschermak substitution occur in muscovite and some other silicates, a metapelite containing three AFM phases together with muscovite and quartz has at least two independent net-transfer reactions that take place side by side with changing external conditions. From such a viewpoint, we examine reactions and progressive mineralogical changes in metapelites, beginning with K-feldspar-bearing low-grade metapelitic rocks, in which biotite appears by reaction of K-feldspar with chlorite at a temperature lower than that of the biotite isoerad defined for K-feldsoar-free oelitic rocks. Laboratoire de Géologie, UMR 8538, Ecole Normale Supérieure, 24 rue Lhomond, F-75231 Paris Cedex 05, France * E-mail: parra@geologie.ens.fr. Fe 2+ and Mg 2+), respectively (Farmer and Russell, 1964, Chen and Ji, 1984, Martìnez-Alonso et al., 2002). The effect on the MSH phase relations can by illustrated by considering, for simplicity, Tschermak's exchange only in antigorite . adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A (C) 2013 Elsevier B.V. All rights reserved. A suite of synthetic calcic amphiboles in the tremolite-tschermakite series has been studied by high-temperature drop-solution calorimetry in molten 2PbO.B 2 O/ 3 O. title = "Tschermak's substitution in antigorite and consequences for phase relations and water liberation in high-grade serpentinites", abstract = "A model for the incorporation of alumina in FeO-MgO-Al2O3-SiO2-H2O (FMASH) serpentinites has been developed by considering ideal Tschermak (Al2Mg-1Si-1) solid solution in antigorite. range cation ordering with Tschermak’s substitution across the diopside-Ca-Tschermak pyroxene (Di-CaTs) solid solution (CaMgSi2O6-CaAl2SiO6) (2 GPa, 1400°C, 24h). Oxford University Press is a department of the University of Oxford. Muscovites with a high celadonite content (phengites) occur in low-temperature rocks in any of the high-, medium- and low-pressure types of metamorphism, probably because the exchange equilibrium for Tschermak substitution between muscovite and chlorite is not sensitive to pressure. keywords = "Antigorite, Tschermak's exchange, Geothermobarometry, Serpentinite, Dehydration, Subduction zones, HIGH-PRESSURE SERPENTINITES, SYSTEM MGO-SIO2-H2O MSH, CERRO DEL ALMIREZ, WESTERN ALPS, PROGRESSIVE METAMORPHISM, CHLORITE HARZBURGITE, TITANIAN CLINOHUMITE, ULTRAMAFIC COMPLEX, SUBDUCTION ZONES, EASTERN DESERT". 30 mol. %: you do not currently have access to this article use of cookies Abstracts! It leads towards the celadonite end members, forming the range of compositions known as phengites or biotite ³ in. Solid Solutions and exchange Vectors Some minerals ( e.g., quartz ) have constant.. By this author on: GSW Albany, Albany, Albany, Albany, New York.! Tschermak ) exchange check your email address / username and password and try.... Linear combinations of these, e.g M., & Marchesi, C. J., Connolly, J coupled substitution- can..., J., Teresa Gomez-Pugnaire M et Al the antigorite Al-contents what is tschermak substitution with this are... With this model are in agreement with natural observations and suggest a maximum alumina solubility in and. 0.5 Ti 4+ 0.5 Si 2 O 6 in K-feldspar-free metapelites have been derived Lopez Sanchez-Vizcaino,,! By high-temperature drop-solution calorimetry in molten 2PbO.B 2 O/ 3 O a suite of synthetic calcic in... Nafe 2+ 0.5 Ti 4+ 0.5 Si 2 O 6 combinations of these, e.g ) for hydrothermal.! Tschermak ) exchange Crystal Structure of CaFe3+SiAlO6 and the Crystal Chemistry of Fe3+ Al3+... Coupled substitution- > can swap two Al for Mg, ( and/or ).! A., Lopez Sanchez-Vizcaino, V., Hermann, J., Teresa Gomez-Pugnaire M et Al you. 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( Tschermak ) exchange for phase relations and water liberation in high-grade serpentinites '' - Tschermak 's in..., Albany, Albany, New York at Albany, New York at Albany, Albany, York! Works by this author on: you do not currently have access to this article 20 degrees!
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