Hostname: page-component-7479d7b7d-fwgfc Total loading time: 0 Render date: 2024-07-11T06:28:41.437Z Has data issue: false hasContentIssue false
  • English
  • Français

The roedderite-chayesite series from Spanish lamproites: crystal-chemical characterization

Published online by Cambridge University Press:  05 July 2018

E. Alietii ,
M. F. Brigatti ,
S. Capedri  and
L. Poppi
E. Alietii
Affiliation:
Dipartimento di Scienze della Terra, Università di Modena, Via S. Eufemia, 19, I-41100 Modena, Italy
M. F. Brigatti
Affiliation:
Dipartimento di Scienze della Terra, Università di Modena, Via S. Eufemia, 19, I-41100 Modena, Italy
S. Capedri
Affiliation:
Dipartimento di Scienze della Terra, Università di Modena, Via S. Eufemia, 19, I-41100 Modena, Italy
L. Poppi
Affiliation:
Dipartimento di Scienze della Terra, Università di Modena, Via S. Eufemia, 19, I-41100 Modena, Italy
Get access Rights & Permissions [Opens in a new window]

Abstract

Members of the roedderite-chayesite series in lamproites from Cancarix (SE Spain), crystallized from late magmatic residua under low PH2O, high temperature (∼ 1100°C), oxidizing conditions. They exhibit the following main chemical variations: 0.14 ⩽ Na ⩽ 0.62 atoms per formula unit (apfu); 0.80 ⩽ K⩽ 1.00 apfu; 2.97 ⩽ Mg ⩽ 4.33 apfu; 0.00 ⩽ Fe2+ ⩽ 1.19 apfu; 0.42 ⩽ Fe3+ ⩽ 0.87 apfu; they are hexagonal (10.120 ⩽ a ⩽ 10.135 Å, 14.305 ⩽ c ⩽ 14.326 Å), P6/mcc. The characteristic chemical substitution is: Fe3+ + □ ⇌ Fe2+ + (K+Na)+. Six crystal structures have been refined to 0.020 ⩽ Robs ⩽ 0.026. They have the osumilite/milarite-type structure, with Si entering the double tetrahedral T1 six-membered rings, and Mg and Fe entering both the ring-linking T2 tetrahedra, and the A octahedra. The 12-coordinated C site, located between two double rings of T1 tetrahedra, is occupied mainly by K and subordinately by Na. Furthermore, Na occupies the partially empty nine-fold coordinated B site which occurs both in the ideal (z = 0) and in a split-atom position along the c direction.

Keywords

roedderitechayesitemilarite grouplamproiteCancarixSpain
Type
Mineralogy
Information
Mineralogical Magazine , Volume 58 , Issue 393 , December 1994 , pp. 655 - 662
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1994

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Abraham, K., Gebert, W., Medenbach, O., Schreyer, W. and Hentschel, G. (1983) Eifelite, KNa3Mg4Sii203o, a new mineral of the osumilite group with octahedral sodium. Contrib. Mineral. Petrol, 82, 252–8.CrossRefGoogle Scholar
Armbruster, T. (1989) Crystal chemistry of double-ring silicates: structure of roedderite at 100° and 300° K. Eur. J. Mineral, 1, 715–8.CrossRefGoogle Scholar
Armbruster, T. and Oberhansli, R. (1988a) Crystal chemistry of double-ring silicates: structural, chemical and optical variation in osumilites. Amer. Mineral, 73, 585–94.Google Scholar
Armbruster, T. and Oberhansli, R. (1988b) Crystal chemistry of double-ring silicates: structure of sugilite and brannockite. Amer. Mineral, 73, 595–600.Google Scholar
Brigatti, M.F., Contini, S., Capedri, S. and Poppi, L. (1993) Crystal chemistry and cation ordering in Pseudobrookite and armalcolite from Spanish lamproites. Eur. J. Mineral, 5, 73–94.CrossRefGoogle Scholar
Contini, S., Venturelli, G., Toscani, L., Capedri, S. and Barbieri, M. (1993) Cr-Zr-armalcolite-bearing lamproites of Cancarix, SE Spain. Mineral. Mag., 57, 203–16.CrossRefGoogle Scholar
Fleischer, M. and Mandarino, J.A. (1991) Glossary of mineral species. Mineralogical Record, Tucson.Google Scholar
Hawthorne, F.C. and Smith, J.V. (1986) Enumeration of 4-connected 3-dimensional nets and classification of framework silicates. 3D nets based on insertion of 2-connected vertices into 3-connected plane nets. Zeit. Krist., 175, 15–30.Google Scholar
Hawthorne, F.C, Mitsuyoshi, K., Cerny, P., Ball, N., Rossman, G. R. and Grice, J.D. (1991) The crystal chemistry of the milarite-group minerals. Amer. Mineral, 76, 1836–56.Google Scholar
Khan, A.A., Baur, W.H. and Forbes, W.C. (1972) Synthetic magnesian merrihueite, dipotassium penta-magnesium dodecasilicate: tetrahedral mag-nesiosilicate framework crystal structure. Ada Cryst., B28, 267–72.Google Scholar
Liebau, F. (1985) Structural chemistry of silicates. Springer-Verlag, BerlinCrossRefGoogle Scholar
North, A.C.T., Phillips, D.C. and Mathews, F.S. (1968) A semi-empirical method of absorption correction. Ada Cryst., A24, 351–9.Google Scholar
Robinson, K., Gibbs, G.V. and Ribbe, P.H. (1971) Quadratic elongation: A quantitative measure of distortion in coordination polyhedra. Science, 172, 567–70.CrossRefGoogle ScholarPubMed
Sheldrick, G.M. (1976) SHELX-76. Programme for crystal structure determination. Univ. Cambridge, England.Google Scholar
Velde, D., Medenbach, O., Wagner, C. and Schreyer, W. (1989) Chayesite, K(Mg,Fe+2)4Fe3+Si1203o: a new rock forming silicate mineral of the osumilite group from the Moon Canyon (Utah) lamproite. Amer. Mineral, 74, 1368–73.Google Scholar
Wagner, C. and Velde, D. (1986) The mineralogy of K-bearing lamproites. Amer. Mineral, 71, 17–37.Google Scholar
Zoltai, T. (1960) Classification of silicates and other minerals with tetrahedral structures. Amer. Mineral, 45, 960–73.Google Scholar