Quick Search:    advanced search

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

Geological Magazine

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 ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by CHAN, G. H.-N. Articles by LO, C.-H. Search for Related Content GeoRef GeoRef Citation

Timing of subduction zone metamorphism during the formation and emplacement of Troodos and Baer–Bassit ophiolites: insights from ⁴⁰Ar–³⁹Ar geochronology

GAVIN HEUNG-NGAI CHAN^*,, JOHN MALPAS^*, COSTAS XENOPHONTOS^* and CHING-HUA LO

^* Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China
Department of Geosciences, National Taiwan University, 245 Choushan Road, Taipei 106, Taiwan

Author for correspondence: Department of Earth Sciences, Oxford University, Parks Road, Oxford, OX1 3PR, UK; e-mail: gavin.chan{at}earth.ox.ac.uk

The Troodos ophiolite in Cyprus and Baer–Bassit ophiolite in Syria together form part of the Tethyan ophiolite belt. They were generated in a supra-subduction zone setting in Late Cretaceous times. As with many of the ophiolite occurrences in this belt, the sequences are closely associated with tectonic ‘coloured mélange’ zones, which contain, among a variety of lithologies, metre- to kilometre- size blocks of metamorphic rocks. Precise ⁴⁰Ar–³⁹Ar laser step-heating experiments performed on four amphibolites from SW Cyprus and six from NW Syria, yield plateau ages ranging from 75.7 ± 0.3 Ma to 88.9 ± 0.8 Ma in Cyprus and 71.7 ± 0.5 to 88.4 ± 0.4 Ma in Syria. The older limits of these time spans are coeval with the age of the formation of the associated ophiolites. Unlike other metamorphic sole rocks which seem to form in relatively short time spans, these metamorphic rocks found in Cyprus and Syria are interpreted to have formed in Late Cretaceous times by accretion below the overriding Troodos and Baer–Bassit crust for a period of 15–18 Ma. The metamorphic complexes were exhumed by extension and crustal thinning associated with subduction roll-back and the rotation of the overriding plate until the cessation of subduction in Maastrichtian times. In Cyprus, the exhumed metamorphic complex was incorporated into an accretionary prism constructed primarily of the collapsed Mamonia passive margin sequence intercalated with rocks of the Troodos ophiolite during plate collision in the Maastrichtian. Concomitantly, in Syria, the Baer–Bassit ophiolite and subcreted metamorphic complex were emplaced onto the Arabian passive margin and fragmented into blocks and knockers, forming the Baer–Bassit mélange.

Key Words: Troodos ophiolite • Baer–Bassit ophiolite • Ayia Varvara • ⁴⁰Ar–³⁹Ar

This article has been cited by other articles:

				G.H.-N. CHAN, J. MALPAS, C. XENOPHONTOS, and C.-H. LO Magmatism associated with Gondwanaland rifting and Neo-Tethyan oceanic basin development: evidence from the Mamonia Complex, SW Cyprus Journal of the Geological Society, May 1, 2008; 165(3): 699 - 709. [Abstract] [Full Text] [PDF]