Jurassic metabasic rocks in the Kizilirmak accretionary complex (Kargi region, Central Pontides, Northern Turkey)


Celik O. F. , CHIARADIA M., MARZOLI A., Ozkan M., BILLOR Z., Topuz G.

TECTONOPHYSICS, cilt.672, ss.34-49, 2016 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 672
  • Basım Tarihi: 2016
  • Doi Numarası: 10.1016/j.tecto.2016.01.043
  • Dergi Adı: TECTONOPHYSICS
  • Sayfa Sayıları: ss.34-49

Özet

The Kiztlirmak accretionary complex near Kargi is tectonically bounded by the Jurassic and Early Cretaceous metamorphic massives of the Central Pontides. It consists mainly of serpentinite, serpentinized peridotite, gabbro, basalt, metabasite and deep-marine sedimentary rocks. The metabasites in the Kizilirmak accretionary complex are tectonically located within a serpentinite, radiolarian chert, spilitized basalt, gabbro association and commonly display a steep contact with serpentinites. Amphiboles from metabasites yielded robust Ar-40/Ar-39 plateau ages ranging between 159.4 +/- 0.4 Ma and 163.5 +/- 0.8 Ma. These are interpreted as cooling ages of the metabasites. The metabasites have Sr-87/Sr-86((i)) between 0.7035 and 0.7044 and Pb-206/Pb-204((i)) ranging between 18.18 and 18.92. The gabbros have higher Sr-87/Sr-86((i)) between 0.7044 and 0.7060 and (206)pb/(204)pb((i)) ranging between 17.98 and 18.43. Three basalt samples display Sr-87/Sr-86((i)) between 0.7040 and 0.7059. Their (206)pb/Pb-204 (0 are unrealistically low (15.42 and 15.62), suggesting, most likely, Pb loss which results in over-corrected values for decay through time. Pb-Sr-Nd isotopic compositions for all samples consistently plot between the fields of MORB or the Depleted MORB Mantle reservoirs and enriched mantle reservoirs (EMII rather than EMI). All the samples (except one dolerite dike) have negative epsilon Nd-DM(t (= 160 Ma)) values, suggesting derivation from a reservoir more enriched than the depleted mantle. The protoliths of metabasites correspond to-diverse sources (N-MORB, E-MORB, OIB and IAT) based on whole rock major and trace element composition. An IAT-like protolith for the metabasites indicates that the Izmir-Ankara-Erzincan ocean domain was subducting and the tectonic regime was compressional during Late Jurassic and before. The protoliths of these rocks were metamorphosed during the subduction/accretion processes, as observed in the metamorphic rocks located along the Balkan, Northern Turkey and Armenia/Iran ophiolites and/or accretionary complexes.