Abstract
The CaO-MgO-Al2O3-SiO2-Na2O multicomponent system was experimentally studied at 7.0 and 8.5 GPa using an anvil-with-hole toroidal high-pressure apparatus to examine two binary joins: pyropegrossular and grossular-Na-majorite. These and literature data were employed to simulate the liquidus surface of the pyrope-grossular-Na-majorite system. The liquidus surface of garnet of predominantly pyrope composition is dominant in the diagram, and the garnet contains much of the Na2MgSi5O12 end member. Melting was observed in this region at temperatures above 1900°C, and the solidus of the system occurs at temperatures below 1550°C. The pyrope-grossular system shows a miscibility gap at 50–65 mol % of the pyrope component and two series of garnet solid solutions. The dominant phase at grossular and Na-majorite mixing is pyroxene, and garnet crystallizes within a fairly narrow field in the grossular-rich region. All garnets synthesized in the systems have elevated Si and Na concentrations and belong to the majorite series, for which a uniform mechanism of isomorphism (Mg, Ca) + Al = Si + Na was proved.
Similar content being viewed by others
References
M. Akaogi and A. Akimoto, “Pyroxene-garnet solid-solution equilibria in the systems Mg4Si4O12-Mg3Al2Si3O12 and Fe4Si4O12-Fe3Al2Si3O12 at high pressures and temperatures,” Phys. Earth. Planet. Inter. 15, 90–106 (1977).
R. J. Angel, T. Gasparik, N. L. Ross, L. W. Finger, C. T. Prewitt, and R. M. Hazen, “A silica-rich sodium pyroxene phase with six-coordinated silicon,” Nature 335, 156–158 (1988).
R. Berman, “Mixing properties of Ca-Mg-Fe-Mn garnets,” Am. Mineral. 75, 328–344 (1990).
A. V. Bobrov, Yu. A. Litvin, L. Bindi, and A. M. Dymshits, “Phase relations and formation of sodium-rich majoritic garnet in the system Mg3Al2Si3O12-Na2MgSi5O12 at 7.0 and 8.5 GPa,” Contrib. Mineral. Petrol. 156, 243–257 (2008b)
A. V. Bobrov, H. Kojitani, M. Akaogi, and Yu. A. Litvin, “Phase relations on the diopside-hedenbergite-jadeite join up to 24 GPa and stability of Na-bearing majoritic garnet,” Geochim. Cosmochim. Acta 72, 2392–2408 (2008a)
A. V. Bobrov, A. M. Dymshits, and Yu. A. Litvin, “Conditions of magmatic crystallization of Na-bearing majoritic garnets in the Earth mantle: evidence from experimental and natural data,” Geochem. Int. 47(10), 951–965 (2009).
A. V. Bobrov, A. M. Dymshits, Yu. A. Litvin, and L. Bindi, “The Mg3Al2Si3O12-Na2MgSi5O12 system at pressures of 7.0 and 8.5 GPa and a temperature of 1300–1800°C: phase relationships and crystallization of Na-bearing majoritic garnet,” Mosc. Univ. Geol. Bull. 67(5), 289–297 (2012).
V. G. Butvina, A. V. Bobrov, and Yu. A. Litvin, “The pyrope-grossular-almandine system at 6.5 GPa and 1500–1900°C: an experimental study,” Dokl. Earth Sci. 379A, 709–712(2001).
R. M. Davies, W. L. Griffin, S. Y. O’ Reilly, and T. E. McCandless, “Inclusions in diamonds from the K14 and K10 kimberlites, Buffalo Hills, Alberta, Canada: diamond growth in a plume?,” Lithos 77, 99–111 (2004).
A. M. Dymshits, A. V. Bobrov, L. Bindi, Yu. A. Litvin, K. D. Litasov, A. F. Shatskiy, E. Ohtani, “Na-bearing majoritic garnet in the Na2MgSi5O12-Mg3Al2Si3O12 join at 11–20 GPa: phase relations, structural peculiarities and solid solutions,” Geochim. Cosmochim. Acta 105, 1–13 (2013).
T. Gasparik, “Transformation of enstatite-diopside-jadeite pyroxenes to garnet,” Contrib. Mineral. Petrol. 102, 389–405 (1989).
T. Gasparik, “Enstatite-jadeite join and its role in the Earth’s mantle,” Contrib. Mineral. Petrol. 111, 283–298 (1992).
T. Gasparik, “Diopside-jadeite join at 16–22 GPa,” Phys. Chem. Mineral. 23, 476–486 (1996).
T. Gasparik and Yu. A. Litvin, “Stability of Na2Mg2Si2O7 and melting relations in the forsteritejadeite join at pressures up to 22 GPa,” Eur. J. Mineral. 9, 311–326 (1997).
C. A. Geiger, “Thermodynamics of (Fe2+,Mn2+,Mg,Ca)3Al2Si3O12 garnet: a review and analysis,” Mineral. Petrol. 66, 271–299 (1999).
D. L. Hamilton and C. M. B. Henderson, “The preparation of silicate compositions by a gelling method,” Mineral. Mag. 36, 832–838 (1968).
B. Harte and N. Cayzer, “Decompression and unmixing of crystals included in diamonds from the mantle transition zone,” Phys. Chem. Mineral. 34, 647–656 (2007).
T. Irifune, “An experimental investigation of the pyroxene-garnet transformation in a pyrolite composition and its bearing on the constitution of the mantle,” Phys. Earth Planet. Inter. 45, 324–336 (1987).
T. Irifune and E. Ohtani, “Melting of pyrope Mg3Al2Si3O12 up to 10 GPa: possibility of a pressure-induced structural change in pyrope melt,” J. Geophys. Res. 91, 9357–9366 (1986).
Yu. A. Litvin, Physicochemical Studies of Melting of Materials from Deep Earth (Nauka, Moscow 1991) [in Russian].
I. Yu. Malinovskii, A. M. Doroshev, and A. A. Kalinin, “Study of the pyrope-grossular garnet join stability at P = 30 Kbar,” (1983).
R. O. Moore and J. J. Gurney, “Pyroxene solid solution in garnets included in diamonds,” Nature 318, 553–555 (1985).
S. Ono and A. Yasuda, “Compositional change of majoritic garnet in a MORB composition from 7 to 17 GPa and 1400 to 1600°C,” Phys. Earth. Planet. Inter. 96, 171–179 (1996).
A. E. Ringwood, “Phase transformations and their bearing on the constitution and dynamics of the mantle,” Geochim. Cosmochim. Acta 55, 2083–2110 (1991).
V. S. Shatskii, D. A. Zedgenizov, and A. L. Ragozin, “Majoritic garnets in diamonds from placers of the northeastern Siberian Platform,” 432 (2), 835–838 (2010).
N. V. Sobolev, E. S. Efimova, L. F. Reimers, O. D. Zakharchenko, A. I. Makhin, and L. V. Usova, “Mineral inclusions in the garnets from Arkhangelsk kimberlite province,” Geol. Geofiz. 38(2), 358–370 (1997).
T. Stachel, “Diamonds from the asthenosphere and the transition zone,” Eur. J. Mineral. 13, 883–892 (2001).
N. V. Surkov and Yu. G. Gartvich, “Experimental study of phase equilibria in the pyrope-grossular join at a pressure of 30 kbar,” Petrology 8(1), 84–95 (2000).
V. L. Vinograd and M. H. F. Sluiter, “Thermodynamics of mixing in pyrope-grossular Mg3Al2Si3O12-Ca3Al2Si3O12 solid solution from lattice dynamics calculation and Monte Carlo simulations,” Am. Mineral. 91, 1815–1830 (2006).
W. Wang, S. Sueno, E. Takahashi, H. Yurimoto, and T. Gasparik, “Enrichment processes at the base of the Archean lithospheric mantle: observations from traceelement characteristics of pyropic garnet inclusions in diamond,” Contrib. Mineral. Petrol. 139, 720–733 (2000).
Author information
Authors and Affiliations
Corresponding author
Additional information
Original Russian Text © A.M. Dymshits, A.V. Bobrov, Yu.A. Litvin, 2015, published in Geokhimiya, 2015, No. 1, pp. 12–21.
Rights and permissions
About this article
Cite this article
Dymshits, A.M., Bobrov, A.V. & Litvin, Y.A. Phase relations in the system (Mg,Ca)3Al2Si3O12-Na2MgSi5O12 at 7.0 and 8.5 GPa and 1400–1900°C. Geochem. Int. 53, 9–18 (2015). https://doi.org/10.1134/S0016702915010036
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1134/S0016702915010036