The Eldivan ophiolite and volcanic rocks in the Izmir-Ankara-Erzincan suture zone, Northern Turkey: Geochronology, whole-rock geochemical and Nd-Sr-Pb isotope characteristics


ÇELİK Ö. F. , CHIARADIA M., MARZOLI A., Billor Z., MARSCHIK R.

LITHOS, cilt.172, ss.31-46, 2013 (SCI İndekslerine Giren Dergi) identifier identifier

Özet

Gabbros and dolerite dikes of the Eldivan ophiolite and basaltic volcanic rocks of the ophiolitic melange in the central part of the Izmir-Ankara-Erzincan (IAE) suture zone were investigated for their Ar-40/Ar-39 age and whole-rock-major-trace element and Sr-Nd-Pb isotope compositions. Based on geological and geochemical characteristics basaltic volcanic rocks in the ophiolitic melange are subdivided into two groups (Groups I and II) with ocean island basalts or enriched mid-ocean ridge basalt characteristics, respectively. Gabbros and dolerite dikes of the Eldivan ophiolite (Groups III and IV) have instead geochemical compositions indicative of a subduction-related environment. The volcanic rocks of Group I have Sr-87/Sr-86((i)) between 0.7037 and 0.7044, (Nd(i)-DM) of -4.5 to -5.6, and Pb-206/Pb-204((i)) ranging between 18.35 and 18.75. Group II volcanic rocks have higher Sr-87/Sr-86((i)) values (0.7049-0.7055), (Nd(i)-DM) ranging between -5.4 and -6.0, and Pb-206/Pb-204((i)) between 18.14 and 18.62. The Nd isotopic signatures and Pb-207/Pb-204((i)) values of the volcanic rocks of both groups point to a different source with respect to those of the Eldivan ophiolite. The low Pb-206/Pb-204((i)) values relative to the ophiolitic rocks seem to exclude a significant contribution from a HIMU reservoir, whereas the Pb-207/Pb-204((i)) values slightly above the NHRL might indicate some contribution from an EM2-type reservoir. Gabbros (Group III) of the Eldivan ophiolite and dolerite dikes (Group IV) cross-cutting the uttramafic part of the ophiolite show Sr-87/Sr-86((i)) between 0.7038 and 0.7053, (Nd(i)-DM) from -2 to -3.6 and Pb-206/Pb-204((i)) between 18.10 and 18.80. The gabbros yield ca. 150 Ma Ar-40/Ar-39 amphibole-plateau ages, which, together with the geochemical data, indicate that they were produced above subducted oceanic lithosphere in the IAE ocean domain in Late Jurassic times. Therefore, the Eldivan ophiolite in the IAE suture zone constitutes a link between the Hellenide-Dinaride ophiolite belts to the west and the Armenian-Iranian ophiolites to the east. (C) 2013 Elsevier B.V. All rights reserved.