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

Abstract

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 kilometresize blocks of metamorphic rocks. Precise 40 Ar-39 Ar 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.

Linking the NE Anatolian and Lesser Caucasus ophiolites: evidence for large-scale obduction of oceanic crust and implications for the formation of the Lesser Caucasus-Pontides Arc

“…Tectonic map of Mesozoic Ophiolites and ophiolitic mélanges from the Tethyan realm in Turkey and adjacent areas (modified after Stampfli, 2000) and representative geochronological data from rocks of the ophiolitic mélanges as well as from metamorphic soles (modified after Çelik et al, 2011). All data are from 40 Ar/ 39 Ar analyzes except where stated otherwise: (1) Dilek, Thy, Hacker, and Grundvig (1999); (2) Parlak and Delaloye (1999); (3) Çelik, Delaloye, and Feraud (2006); (4) Chan, Malpas, Xenophontos, and Lo (2007); (5) Galoyan et al (2009); (6) Önen (2003); (7) Harris, Kelley, and Okay (1994); (8) Dimo-Lahitte, Monié, and Vergély (2001); (9) Spray, Bébien, Rex, and Roddick (1984); (10) Roddick, Cameron, and Smith (1979); (11) Koepke, Seidel, and Kreuzer (2002), K-Ar age data; (12) Hatzipanagiotou and Pe-Piper (1995), K-Ar age data; (13) Lanphere, Coleman, Karamata, and Pamić (1975), K-Ar age data; (14) Rolland et al (2010); (15) fore-or back-arc origin, suggest the existence of an intra-oceanic arc. The structural and geochemical processes leading to their formation are almost identical, except for less important subduction contamination for back-arc tholeiites.…”

Kinematics of Late Cretaceous subduction initiation in the Neo‐Tethys Ocean reconstructed from ophiolites of Turkey, Cyprus, and Syria

“…There is no direct age for the crustal section of the Baer‐Bassit ophiolite. 40 Ar‐ 39 Ar ages on hornblende of 88.9 ± 0.8 Ma from the metamorphic sole beneath the Baer‐Bassit ophiolite [ Chan et al , ] are consistent with other metamorphic sole ages from the Hatay and surrounding ophiolites. Based on these similarities, a Late Cretaceous crustal age for the Baer‐Bassit ophiolite is generally assumed.…”

“…It is widely perceived that the Troodos ophiolite of Cyprus (Figure ) forms the westward continuation of the Hatay and Baer‐Bassit ophiolites. The Troodos ophiolite has crustal ages of 92–90 Ma [ Mukasa and Ludden , ], similar to the ages retrieved from metamorphic sole relics in the juxtaposed Mamonia Complex [ Chan et al , ]. The Mamonia Complex is an accretionary prism including ocean and continental passive margin‐derived rocks with ages ranging from Triassic to Early Cretaceous [e.g., Bailey et al , ].…”

The Ayyubid Orogen: An Ophiolite Obduction-Driven Orogen in the Late Cretaceous of the Neo-Tethyan South Margin

“…Since then a huge amount of work has been carried out on the different members of this ophiolitic crescent, all members of which have been shown to be suprasubduction zone ophiolites (e.g. general: Şengör and Natal'in 1996;Oman: Lippard et al 1986;Kermanshah: Whitechurch et al 2013, Neyriz: Babaei et al 2005Cilo: Yılmaz 1985;Kızıldağ: Tekeli and Erendil 1986;Baer-Bassit: Al-Riyami et al, 2000, 2002Chan et al 2007;Troodos: Miyashiro 1973;Pearce and Robinson 2010;Antalya Okay and Özgül, 1984). What is of primary interest from the viewpoint of this paper is the timing of obduction of each of these large ophiolite nappes.…”