Hostname: page-component-84b7d79bbc-7nlkj Total loading time: 0 Render date: 2024-07-30T17:54:49.025Z Has data issue: false hasContentIssue false
  • English
  • Français

Crystal chemistry and intracrystalline relationships of orthopyroxene in a suite of high pressure ultramafic nodules from the ‘Newer Volcanics’ of Victoria, Australia

Published online by Cambridge University Press:  05 July 2018

Gianmario Molin  and
Marilena Stimpfl
Gianmario Molin
Affiliation:
Dipartimento di Mineralogia e Petrologia, Universita' di Padova, Corso Garibaldi 37, 35100 Padova, Italy
Marilena Stimpfl
Affiliation:
Dipartimento di Mineralogia e Petrologia, Universita' di Padova, Corso Garibaldi 37, 35100 Padova, Italy
Get access Rights & Permissions [Opens in a new window]

Abstract

A suite of orthopyroxenes from spinel Iherzolite xenoliths associated with basanites occurring in the Victorian (Australia) post-Pliocene ‘Newer Volcanics’ province was investigated by means of a crystal chemical methodology which provides accurate site occupancy and site configuration parameters.

The M1 configuration is essentially constrained by AlVI rather than Fe2+. In addition, Fe3+, Cr3+ and Ti4+ are confined to M1 (Molin, 1989) and AlIV to TB. M2 is controlled by FeM22+ ⇌ MgM2, constrained by (Fe2+ + Ca)M2 > 0.14 atoms per formula unit (p.f.u.). Cation substitution in TB and M2 constrains the sum of the volumes of the respective polyhedra VTB+VM2 to remain essentially constant. Therefore, M2 favours the retention of the large Fe2+ up to melting-point, causing non-ideality of this iron-depleted orthopyroxene. As a consequence, the investigated orthopyroxene can be considered an ultimate Fe2+ carrier during partial mantle melting.

Keywords

orthopyroxenecrystal chemistryspinel Iherzolite
Type
Petrology
Information
Mineralogical Magazine , Volume 58 , Issue 391 , June 1994 , pp. 325 - 332
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

Brown, G. M. (1967) Mineralogy of basaltic rocks. In Mineralogy of Basaltic Rocks. I. Basalt, H. H. Hess and A. Poldevaart, eds., Interscience, New York. pp. 103-62.Google Scholar
Cundari, A., Dal Negro, A., Piccirillo, E. M., Delia Giusta, A. and Secco, L. (1986) Intracrystalline relationships in olivine, orthopyroxene, clino-pyroxene and spinel from a suite of spinel lherzolite xenoliths from Mt Noorat, Victoria, Australia. Comparison with related suites. Contrib. Mineral. Petrol, 94, 525–32.CrossRefGoogle Scholar
Dal Negro, A., Carbonin, S., Molin, G. M., Cundari, A. and Piccirillo, E. M. (1982) Intracrystalline cation distribution in natural clinopyroxenes of tholeiitic, transitional, and alkaline basaltic rocks. In Advances in Physical Geochemistry, Saxena, S. K., ed., Springer Verlag, Berlin, Heidelberg, New York, 2, 117-50.Google Scholar
Dal Negro, A., Carbonin, S., Domeneghetti, C, Molin, G. M., Cundari, A. and Piccirillo, E. M. (1984) Crystal chemistry and evolution of the clinopyroxene in a suite of high pressure ultra- mafic nodules from the Newer Volcanics of Victoria, Australia. Contrib. Mineral. Petrol., 86, 221–9.CrossRefGoogle Scholar
Domeneghetti, M. C, Molin, G. M. and Tazzoli, V. (1985) Crystal-chemical implications of the Mg2+—Fe2+ distribution in orthopyroxenes. Amer. Mineral, 70, 987–95.Google Scholar
Ellis, D. J. (1976) High pressure cognate inclusions in the Newer Volcanics of Victoria. Contrib. Mineral Petrol, 58,149-80.Google Scholar
Frey, F. A. and Green, D. H. (1974) The mineralogy, geochemistry and origin of lherzolite inclusions in Victorian basanites. Geochim. Cosmochim. Acta, 38, 1023–59.CrossRefGoogle Scholar
Ganguly, J. and Ghose, S. (1979) Aluminous orthopyroxene: order-disorder, thermodynamic properties and petrologic implications. Contrib. Mineral. Petrol., 69, 375–8.CrossRefGoogle Scholar
Irving, A. J. (1974) Pyroxene-rich ultramafic xenolith in the Newer basalts of Victoria, Australia. Neues Jahrb. Mineral., Abh., 120, 147–67.Google Scholar
James, F. and Ross, M. (1975) MINUIT, a system for function minimisation and analysis of the parameter errors and correlations. Computer Physics, 10 343-7, CERN/DD, International Report 75/20. Google Scholar
Molin, G. M. (1989) Crystal chemical study of cation disordering in Al-rich and Al-poor orthopyroxenes from spinel lherzolite xenoliths. Amer. Mineral, 74, 593–8.Google Scholar
O'Reilly, S. Y., Nicholls I. A. and Griffin, W. L. (1989) Xenoliths and megacrysts of mantle origin. In Intraplate Volcanism in Eastern Australia and New Zealand (Johnson, R. W., ed.), Cambridge University Press, 254-74.Google Scholar
Papike, J. J., Prewitt, C. T., Sueno, S. and Cameron, M. (1973) Pyroxenes: comparision of real and ideal structural topologies. Zeits. Krist., 138, 254–73.CrossRefGoogle 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
Saxena, S. K. and Ghose, S. (1971) Mg2+-Fe2+order—disorder and the thermodynamics of the orthopyroxene-crystalline solution. Amer. Mineral, 56, 532–59.Google Scholar
Shannon, R. D. (1976) Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Cryst. A32, 751-67.Google Scholar
Virgo, D. and Hafner, S. S. (1970) Fe2+, Mg order-disorder in heated orthopyroxenes. Amer. Mineral, 55, 201–23.Google Scholar