Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hajialioghli, R. Articles by Ziemann, M. Search for Related Content GeoRef GeoRef Citation

Serpentine polymorphs and P-T evolution of metaperidotites and serpentinites in the Takab area, NW Iran

¹ Department of Geology, University of Tabriz, 51664 Tabriz, Iran
² School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK
³ Institut für Geowissenschaften, Universität Potsdam, Postfach 601553, D-14415 Potsdam, Germany

^* E-mail: moazzen{at}tabrizu.ac.ir

The Takab meta-ultramafic rocks of northwestern Iran crop out in association with a variety of metamorphic rocks and they can be divided into three types on the basis of dominant mineral assemblage and degree of serpentinization: metaperidotites, talc-serpentine rocks and serpentinites. The peridotite protoliths were mainly spinel-harzburgites and -dunites. The talc-serpentine rocks formed under low-grade conditions and their dominant mineral assemblage is lizardite/chrysotile + talc + calcite/dolomite. Pseudomorphic textures after olivine and pyroxene are typical. Later, lower amphibolite-facies metamorphism produced antigorite, clinochlore and tremolite. Late alteration, assisted by local shearing, produced more antigorite and late lizardite in the metaperidotites. The mineral chemistry of the serpentine polymorphs is variable. Compositions of coexisting spinel and olivine point to an ophiolitic origin. Thermometric estimates from co-existing relict olivine, pyroxenes and spinel are in the range 1000–1200°C; clinopyroxene barometry yields a pressure of 24±2.7 kbar for the mantle conditions. Exhumation and hydration followed, and the stability of lizardite/chrysotile constrains the T and X_CO2 to <280°C and <0.002, respectively. Subsequent prograde regional metamorphism took place in an orogenic setting, reaching peak temperatures in the range 410–540°C at X_CO2 >0.1. A Neoproterozoic–Early Cambrian age for the Takab protoliths is suggested on the basis of correlations with the Central Iran Zone. The strips of ultramafic rock in the Takab complex can be attributed to lithospheric remnants of the Proto-Tethyan ocean which closed during the Pan-African orogeny.

KEYWORDS: serpentine polymorphs, peridotites, P-T path, Neoproterozoic–Cambrian, Proto-Tethys, northwestern Iran

This article has been cited by other articles:

				A. Merlini, G. Grieco, and V. Diella Ferritchromite and chromian-chlorite formation in melange-hosted Kalkan chromitite (Southern Urals, Russia) American Mineralogist, October 1, 2009; 94(10): 1459 - 1467. [Abstract] [Full Text] [PDF]