Contributions to Mineralogy and Petrology

, Volume 83, Issue 3–4, pp 247–258 | Cite as

Crystal-chemistry and cation ordering in the system diopside-jadeite: A detailed study by crystal structure refinement

  • Giuseppe Rossi
  • David C. Smith
  • Luciano Ungaretti
  • M. Chiara Domeneghetti


The Nybö eclogite pod in Norway is characterized by a great variety of clinopyroxene compositions with Jd contents ranging from less than 5% up to nearly 80%, whilst Ac+Hd contents remain almost constant (mostly within 10±5%).

Unconstrained X-ray structure refinement has been carried out on 16 pyroxene crystals (8 with C2/c and 8 with P2/n space group) from the Nybö eclogite, and also on one omphacite crystal (from Lago Mucrone in the Sesia-Lanzo Zone, Western Alps) which displays the highest degree of cation ordering yet described. The final discrepancy factors range from 0.014 to 0.029. The population of the sites has been determined on the basis of bond length considerations and of the results of the site occupancy refinement. Six of these crystals were subsequently analysed by electron microprobe.

The tetrahedral sites are occupied by Si with negligible amounts of Al. Al, Mg, Fe3+ and Fe2+ occur at the octahedral sites; in the ordered P2/n crystals Al and Fe3+ are concentrated at the M11 site, whilst Mg and Fe2+ are concentrated and the M1 site. The eight-coordinated sites contain Ca and Na with negligible amounts of Fe and/or Mg. Ordering of Ca and Na takes place in the P2/n samples in such a way that in the most ordered crystal the M2 site contains almost exactly 0.75 Na+0.25 Ca and the M21 site 0.25 Na+0.75 Ca.

Some geometrical features of the tetrahedra as well as of the octahedra (e.g. tetrahedral quadratic elongation and TILT angle) are not a simple linear function of composition, even when no change in space group occurs. The crystals evidently do not behave like a binary system of the two components, Di and Jd, but behave rather as if the composition Di0.50 Jd0.50 was a distinct end member.

The boundaries between disordered and ordered phases in the Nybö pyroxenes fall at about 0.35 and 0.65 Jd/(Di+ Jd), in close agreement with the previous TEM investigations.

The degree of order varies with composition following a bell-shaped curve: different coaxial bell-shaped curves can be drawn for crystals which have similar compositions but come from different metamorphic environments. The order vs composition diagrams may be useful for the interpretation of the P-T-t histories of the host rocks.


Structure Refinement Composition Diagram Crystal Structure Refinement Simple Linear Function Clinopyroxene Composition 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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  1. Aldridge LP, Bancroft GM, Fleet ME, Herzberg CT (1978) Omphacites studies: II. Mössbauer spectra of C2/c and P2/n omphacites. Am Mineral 63:1107–1115Google Scholar
  2. Busing WR, Martin KO, Levy HS (1962) ORFLS, a Fortran crystallographic least-squares program. U.S. National Technical Information Service, ORNL-TM-305Google Scholar
  3. Cameron M, Papike JJ (1981) Structural and chemical variations in pyroxenes. Am Mineral 66:1–51Google Scholar
  4. Cameron M, Sueno S, Prewitt CT, Papike JJ (1973) High temperature crystal-chemistry of acmite, diopside, hedenbergite, jadeite spodumene and ureyite. Am Mineral 59:594–618Google Scholar
  5. Carbonin S, Molin GM, Munno R, Rossi G (1982) Crystal-chemistry of Ca-rich clinopyroxenes from alkaline and “transitional” volcanic series (Cristallochimica di clinopirosseni ricchi in Ca di serie vulcaniche alcaline e “transizionali”). CR Società Italiana di Mineralogia e Petrologia, AbstractGoogle Scholar
  6. Carpenter MA (1980) Mechanism of exsolution in sodic pyroxenes. Contrib Mineral Petrol 71:289–300Google Scholar
  7. Carpenter MA (1981a) Time-temperature-transformation (TTT) analysis of cation disordering in omphacite. Contrib Mineral Petrol 78:433–440Google Scholar
  8. Carpenter MA (1981b) Omphacite microstructures as time-temperature indicators of blueschist- and eclogite-facies metamorphism. Contrib Mineral Petrol 78:441–451Google Scholar
  9. Carpenter MA, Smith DC (1981) Solid solution and cation ordering limits in high temperature sodic pyroxenes from the Nybö eclogite pod, Norway. Mineral Mag 44:37–44Google Scholar
  10. Carswell DA, Krogh E, Griffin WL (1981) Petrogenetic implications of calculated equilibration conditions for Norwegian orthopyroxene eclogites. Terra Cognita 1:39Google Scholar
  11. Clark JR, Appleman DE, Papike JJ (1969) Crystal-chemical characterization of clinopyroxenes based on eight new structure refinements. Mineral Soc Am, Spec Pap 2:31–50Google Scholar
  12. Clark JR, Papike JJ (1968) Crystal-chemical characterization of omphacites. Am Mineral 53:840–868Google Scholar
  13. Coppens P, Hamilton WC (1970) Anisotropic extinction in the Zachariasen approximation. Acta Crystallogr A26:71–83Google Scholar
  14. Dal Negro A, Carbonin S, Molin GM, Cundari A, Piccirillo EM (1982) Intracrystalline cation distribution in natural clinopyroxenes of tholeitic, transitional and alkaline basalts. In: SK Saxena (ed) Advances in physical geochemistry, Vol. 2, Springer, New York, pp 117–150Google Scholar
  15. Deer WA, Howie RA, Zussman J (1978) Rock-forming minerals, Vol 2A, Single Chain Silicates. Longman, LondonGoogle Scholar
  16. Dollase WA, Gustafson WI (1982) 57Fe Mössbauer spectral analysis of sodic clinopyroxenes. Am Mineral 67:311–327Google Scholar
  17. Domeneghetti MC, Rossi G, Smith DC, Ungaretti L (1981) Pyroxene-amphibole association in a grospyditic xenolith from the kimberlite of Zagadochnaya, Yakutia, Siberia (Associazione pirosseno-anfibolo in un incluso grospiditico della kimberlite di Zagadochnaya, Yukatia, Siberia). Abstract CR Società Italiana di Mineralogia e Petrologia, Vol 37, p 993Google Scholar
  18. Essene EJ, Fyfe WS (1967) Omphacite in californian rocks. Contrib Mineral Petrol 15:1–23Google Scholar
  19. Fleet ME, Herzberg CT, Bancroft GM, Aldridge LP (1978) Omphacites studies: I. The P2/n → C2/c transformation. Am Mineral 63:1100–1106Google Scholar
  20. International Tables for X-ray Crystallography (1974) Kynoch Press, Birmingham G.B., Vol IV, pp 99–101Google Scholar
  21. Kechid SA, Smith DC (1982) Nyböite-katophorite et taramite-pargasite dans la lentille d'eclogite de Liset, Region du Gneiss de 1'Ouest, Norvège. IX Réunion Annuelle de Sciences de la Terr, Univ. P et M Curie, Paris, p 333Google Scholar
  22. Lappin MA, Smith DC (1978) Mantle-equilibrated orthopyroxene eclogite pods from the basal gneisses in the Selje District, Western Norway. J Petrol 19:530–584Google Scholar
  23. Lappin MA, Smith DC (1981) Carbonate-silicate relationships in some eclogites from Sunnmore and Nordfjord, Norway. Trans Royal Soc Edinburgh, Earth Science 72:171–193Google Scholar
  24. Matsumoto T, Tokonami M, Morimoto N (1975) The crystal structure of omphacite. Am Mineral 60:634–641Google Scholar
  25. Morimoto N, Nakajima Y, Syono Y, Akimoto S, Matsui Y (1975) Crystal structures of pyroxene type ZnSiO3 and ZnMgSi2O6. Acta Crystallogr B31:671–676Google Scholar
  26. North ACT, Phillips DC, Mathews FS (1968) A semi-empirical method of absorption correction. Acta Crystallogr A24:351–359Google Scholar
  27. Oberti R, Munno R, Foresti E, Krajewski A (1983) A crystalchemical study on six fassaites from the Predazzo-Monzoni Area. Rendiconti Società Italiana di Mineralogia e Petrologia (in press)Google Scholar
  28. Ohashi Y, Burnham CW, Finger L (1975) The effect of Ca-Fe substitution on the clinopyroxene structure. Am Mineral 60:423–434Google Scholar
  29. Prewitt CT (ed) (1980) Reviews in Mineralogy, Vol. 7, Pyroxenes. Mineral Soc AmGoogle Scholar
  30. Prewitt CT, Burnham CW (1966) The crystal structure of jadeite. Am Mineral 51:956–975Google Scholar
  31. Robinson K, Gibbs GV, Ribbe PH (1971) Quadratic elongation, a quantitative measure of distortion in co-ordination polyhedra. Science 172:567–570Google Scholar
  32. Rossi G, Ghose S, Busing WL (1982) Diopside CaMgSi2O6: refinement of the crystal structure by X-ray and neutron diffraction and preliminary observations on charge density distribution. GSA-MSA Annual Meeting, Abstracts Vol 15, No 7Google Scholar
  33. Rossi G, Smith DC, Ungaretti L, Domeneghetti MC (1983) Comparison of chemical analyses of sodic pyroxenes by X-ray structure refinement and electron microprobe techniques. Periodico di Mineralogia (in press).Google Scholar
  34. Rossi G, Tadini C, Tazzoli V, Munno R (1977) Crystallographic study on clinopyroxenes of the diopside-salite series (Studio cristallografico di clinopirosseni della serie diopside-salite) Abstract. CR Societa Italiana Mineralogia e Petrologia 33:853Google Scholar
  35. Rossi G, Tazzoli V, Ungaretti L (1978) Crystal-chemical studies on sodic clinopyroxenes. XI General Meeting of I.M.A. Abstracts, Vol I:29Google Scholar
  36. Rossi G, Tazzoli V, Ungaretti L (1981) Crystal-chemical studies on sodic clinopyroxenes. Proceedings of the XI General Meeting of I.M.A., Rock-forming Minerals, pp 20–45Google Scholar
  37. Sasaki S, Fujino K, Tackeuchi R, Sadanaga R (1980) On the estimation of atomic charges by the X-ray method for some oxides and silicates. Acta Crystallogr A36:904–915Google Scholar
  38. Smith DC (1980) A tectonic mélange of foreign eclogites and ultramafites in the Basal Gneiss Region, West Norway. Nature 287:366–368Google Scholar
  39. Smith DC (1981) A reappraisal of factual and mythical evidence concerning the metamorphic and tectonic evolution of eclogitebearing terrain in the Caledonides. Abstract, Terra Cognita 1:73–74Google Scholar
  40. Smith DC (1982) On the characterization and credibility of supersilicic, stoichiometric and subsilicic pyroxenes. Abstract, Terra Cognita 2:223Google Scholar
  41. Smith DC, Cheeney RF (1980) Orientated needles of quartz in clinopyroxenes: evidence for exsolution of SiO2 from a nonstoichiometric supersilicic “clinopyroxene”. 26th International Geological Congress, Abstracts, 02.3.1, p 145Google Scholar
  42. Smith DC, Domeneghetti MC, Rossi G, Ungaretti L (1982) Single crystal structure refinements of supersilicic clinopyroxenes from the Zagadochnaya kimberlite pipe, Yakutia, USSR. Terra Cognita 2:223Google Scholar
  43. Smith DC, Mottana A, Rossi G (1980) Crystal-chemistry of a unique jadeite-rich acmite-poor omphacite from the Nybö eclogite pod, Sørpollen, Nordfjord, Norway. Lithos 13:227–236Google Scholar
  44. Smyth JR (1980) Cation vacancies and the crystal-chemistry of breakdown reactions in kimberlitic omphacites. Am Mineral 65:1185–1191Google Scholar
  45. Sobolev NV Jr, Kuznetsova IK, Zyurin NI (1968) The petrology of grospydite xenoliths from the Zagadochnaya kimberlite pipe in Yukutia. J Petrol 9:253–280Google Scholar
  46. Tokonami M (1965) Atomic scattering factor for O2−. Acta Crystallogr 19:486Google Scholar
  47. Ungaretti L (1980) Recent developments in X-ray single crystal diffractometry applied to the crystal-chemical study of amphiboles. Godisnjak Jugoslavenskog Centra za Kristalografiju 15:29–65Google Scholar
  48. Ungaretti L, Smith DC, Rossi G (1981) Crystal-chemistry by X-ray structure refinement and electron microprobe analysis of a series of sodic-calcic to alkali-amphiboles from the Nybö eclogite pod, Norway. Bull Minéral 104:400–412Google Scholar
  49. Vieten K, Hamm HM (1978) Additional notes on the calculation of the crystal-chemical formula of clinopyroxenes and their contents of Fe3+ from microprobe analyses. N Jahrb Mineral Monatsh 2:71–83Google Scholar

Copyright information

© Springer-Verlag 1983

Authors and Affiliations

  • Giuseppe Rossi
    • 1
  • David C. Smith
    • 2
  • Luciano Ungaretti
    • 1
  • M. Chiara Domeneghetti
    • 1
  1. 1.C.N.R. Centre di Studio per la Cristallografia StrutturalePaviaItaly
  2. 2.Laboratoire de Minéralogie, Muséum National d'Histoire NaturelleLabo. Associé au CNRS (LA 286)ParisFrance

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