Hostname: page-component-76fb5796d-wq484 Total loading time: 0 Render date: 2024-04-25T12:06:30.364Z Has data issue: false hasContentIssue false
  • English
  • Français

Low-T formation of high-Cr spinel with apparently primary chemical characteristics within podiform chromitite from Rayat, northeastern Iraq

Published online by Cambridge University Press:  05 July 2018

S. Arai ,
Y. Shimizu ,
S. A. Ismail  and
A. H. Ahmed
S. Arai*
Affiliation:
Department of Earth Sciences, Kanazawa University, Kanazawa 920-1192, Japan
Y. Shimizu
Affiliation:
Department of Earth Sciences, Kanazawa University, Kanazawa 920-1192, Japan
S. A. Ismail
Affiliation:
Geology Department, Salahiddin University, Erbil, Iraq
A. H. Ahmed
Affiliation:
Geology Department, Helwan University, Cairo, Egypt
*
*E-mail: ultrasa@kenroku.kanazawa-u.ac.jp
Get access Rights & Permissions [Opens in a new window]

Abstract

Chemical modification of chromian spinel at low-T alteration was examined in detail for a podiform chromitite from a Tethyan ophiolitic mélange belt at Rayat, northeastern Iraq. The chromitite is highly brecciated and the matrix has been completely altered, producing chlorite and carbonate (dolomite and calcite). High-Cr, low-Fe3+ spinel has formed along the margins and cracks of chromian spinel grains throughout the alteration, associated with unaltered primary spinel and magnetite without ferritchromite. In associated harzburgites, only ferritchromite is found instead of the high-Cr, low-Fe3+ spinel. The high-Cr, low-Fe3+ secondary spinel apparently has chemical properties of mantle origin, plotted at the extension of ordinary mantle spinels on compositional spaces. The character is due to subtraction of Al as chlorite with the addition of an amount of magnetite component from the silicate matrix, which is small in volume relative to peridotite and composed of highly magnesian olivine (up to Fo97). We should treat high-Cr chromian spinels with caution in highly altered mantle-derived rocks, especially chromitite and other rocks with highly magnesian olivine, as well as in detrital particles for provenance study.

Keywords

Cr-rich spinelalterationchromititeRayatIraq
Type
Research Article
Information
Mineralogical Magazine , Volume 70 , Issue 5 , October 2006 , pp. 499 - 508
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2006

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

Abzalov, M. Z. (1998) Chrome-spinels in gabbro-wehrlite intrusions of the Pechenga area, Kola Peninsula, Russia: emphasis on alteration features. Lithos, 43, 109–134.CrossRefGoogle Scholar
Ahmed, A. H., Arai, S. and Attia, A. K. (2001) Petrological characteristics of the Pan African podiform chromitites and associated peridotites of the Proterozoic ophiolite complexes, Egypt. Mineralium Deposita, 36, 72–84.CrossRefGoogle Scholar
Ahmed, A. H., Arai, S., Abdel-Aziz, Y. M. and Rahimi, A. (2005) Spinel composition as a petrogenetic indicator of the mantle section in the Neoproterozoic Bou Azzer ophiolite, Anti-Atlas, Morocco. Precambrian Research, 138, 225–234.CrossRefGoogle Scholar
Arai, S. (1978 a) Formation of the chlorite corona around chromian spinel in peridotite and its significance. Geoscience Reports of Shizuoka University, 3, 9–15 (in Japanese with English abstract).Google Scholar
Arai, S. (1978 b) Chromian spinel lamellae in olivine from the Iwanai-dake peridotite mass, Hokkaido, Japan. Earth and Planetary Science Letters, 39, 267–273.CrossRefGoogle Scholar
Arai, S. (1980) Dunite-harzburgite-chromitite complexes as refractory residue in the Sangun-Yamaguchi zone, western Japan. Journal of Petrology, 21, 141–165.CrossRefGoogle Scholar
Arai, S. (1994 a) Characterization of spinel peridotites by olivine-spinel compositional relationships: Review and interpretation. Chemical Geology, 113, 191–204.CrossRefGoogle Scholar
Arai, S. (1994 b) Compositional variation of olivine-chromian spinel in Mg-rich magmas as a guide to their residual spinel peridotites. Journal of Volcanology and Geothermal Research, 59, 279–294.CrossRefGoogle Scholar
Arai, S. and Okada, H. (1991) Petrology of serpentine sandstone as a key to tectonic development of serpentine belts. Tectonophysics, 195, 65–81.CrossRefGoogle Scholar
Arai, S. and Yurimoto, H. (1994) Podiform chromitites of the Tari-Misaka ultramafic complex, southwestern Japan, as mantle-melt interaction products. Economic Geology, 89, 1279–1288 CrossRefGoogle Scholar
Arai, S., Kadoshima, K. and Morishita, T. (2006) Widespread arc-related melting in the mantle section of the northern Oman ophiolite as inferred from detrital chromian spinels. Journal of the Geological Society, 163, 869–879.CrossRefGoogle Scholar
Barnes, S. J. (2000) Chromite in komatiites, II. Modification during greenschist to mid-amphibolite facies metamorphism. Journal of Petrology, 41, 387–409.CrossRefGoogle Scholar
Barnes, S. J. and Roeder, P. L. (2001) The range of spinel compositions in terrestrial mafic and ultramafic rocks. Journal of Petrology, 42, 2279–2302.CrossRefGoogle Scholar
Dick, H. J. B. and Bullen, T. (1984) Chromian spinel as a petrogenetic indicator in abyssal and alpine type peridotites and spatially associated lavas. Contributions to Mineralogy and Petrology, 86, 54–76.CrossRefGoogle Scholar
Evans, B. W. (1977) Metamorphism of Alpine peridotite and serpentinite. Annual Review of Earth and Planetary Sciences, 5, 397–447.CrossRefGoogle Scholar
Gahlan, H. A., Arai, S., Ahmed, A. H., Ishida, Y., Abdel-Aziz, Y. M. and Rahim, A. (2006) Origin of magnetite veins in serpentinite from the late Proterozoic Bou-Azzer ophiolite, Anti-Atlas, Morocco: an implication for mobility of iron during serpentinization. Journal of African Earth Sciences, 46, 318–330.CrossRefGoogle Scholar
Hey, M. H. (1954) A new review of the chlorites. Mineralogical Magazine, 30, 277–292.CrossRefGoogle Scholar
Irvine, T. N. (1965) Chromian spinel as a petrogenetic indicator; Part 1, theory. Canadian Journal of Earth Sciences, 2, 648–672.CrossRefGoogle Scholar
Irvine, T. N. (1967) Chromian spinel as a petrogenetic indicator; Part 2, petrologic applications. Canadian Journal of Earth Sciences, 4, 71–103.CrossRefGoogle Scholar
Kubo, K. (2002) Dunite formation processes in highly depleted peridotite: Case study of the Iwanaidake peridotite, Hokkaido, Japan. Journal of Petrology, 43, 423–448.CrossRefGoogle Scholar
Loferski, P. J. and Lipin, B. R. (1983) Exsolution in metamorphosed chromite from the Red Lodge district, Montana. American Mineralogist, 68, 777–789.Google Scholar
Moores, E. M., Kellogg, L. H. and Dilek, Y. (2000) Tethyan ophiolites, mantle convection, and tectonic ‘historical contingency’: A resolution of the ‘ophiolite conundrum’. Pp. 3–12 in: Ophiolites and Oceanic Crust: New Insights from Field Studies and the Ocean Drilling Program (Dilek, Y., Moores, E., Elthon, D. and Nicolas, A., editors). Geological Society of America Special Paper 349.Google Scholar
Roeder, P. L. (1994) Chromite: From the fiery rain of chondrules to the Kilauea Iki lava lake. The Canadian Mineralogist, 32, 729–746.Google Scholar
Sack, R. O. and Ghiorso, M. S. (1991) Chromian spinels as petrogenetic indicators: Thermodynamics and petrological applications. American Mineralogist, 76, 827–847.Google Scholar
Sissakian, V. K. (2000) Geological Map of Iraq. 1:1,000,000. State Company of Geological Survey and Mining, Baghdad, Iraq.Google Scholar
Tamura, A. and Arai, S. (2005) Unmixed spinel in chromitite from the Iwanai-dake peridotite complex, Hokkaido, Japan: A reaction between peridotite and highly oxidized magma in the mantle wedge. American Mineralogist, 90, 473–480.CrossRefGoogle Scholar