Diabase dykes from Bogazkale (Corum), Central Anatolia: Geochemical insights into the geodynamical evolution of the northern branch of Neotethys

Balc U., SAYIT K.

GEOCHEMISTRY, cilt.80, sa.2, 2020 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 80 Sayı: 2
  • Basım Tarihi: 2020
  • Doi Numarası: 10.1016/j.chemer.2020.125602
  • Dergi Adı: GEOCHEMISTRY
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Aerospace Database, Aquatic Science & Fisheries Abstracts (ASFA), Artic & Antarctic Regions, Chemical Abstracts Core, Geobase, INSPEC, Civil Engineering Abstracts
  • Anahtar Kelimeler: Izmir-Ankara-Erzincan suture, Northern Neotethys, Ophiolitic melange, Geochemistry, Petrography, Ar-40-Ar-39 geochronology, METAMORPHIC SOLE ROCKS, ERZINCAN SUTURE ZONE, BORNOVA FLYSCH ZONE, LESSER CAUCASUS, SOUTHERN TURKEY, OPHIOLITIC MELANGE, ANKARA MELANGE, VOLCANIC-ROCKS, MAFIC DYKES, FRACTIONAL CRYSTALLIZATION
  • Orta Doğu Teknik Üniversitesi Adresli: Evet

Özet

In the Bogazkale region (Corum, Central Anatolia), pieces of Neotethyan oceanic lithosphere are found in an ophiolitic melange. Within the melange, there are occurrences of isolated diabase dykes that intrude serpentinized and carbonatized ultramafics. The diabases are phaneritic, holocrystalline and equigranular, and consist of plagioclase and hornblende as the main primary mineral phases. They have all undergone low-grade alteration, to varying extents, as reflected by the presence of secondary minerals, including chlorite, epidote, prehnite and actinolite. Immobile trace element systematics suggest that all diabases are of subalkaline basalt composition and display negative Nb anomalies in the N-MORB-normalized plots. They also display flat to slightly LREEdepleted patterns in chondrite-normalized diagrams. The relative Th (and La) enrichment coupled with NMORB-like HFSE composition of the diabases suggests their derivation from a depleted mantle source metasomatized by slab-derived fluids/melts. Overall trace element characteristics are consistent with an oceanic backarc origin. 40Ar-39Ar radiometric dating on the hornblende grains extracted from the two diabase dykes yield ages of 176.30 +/- 0.52 Ma and 178.82 +/- 0.80 Ma (Toarcian, Early Jurassic). This suggests the existence of an intra-oceanic subduction zone within the Izmir-Ankara-Erzincan (IAE) Ocean during the Early Jurassic, which can also be traced along the western (Vardar Zone) and the eastern (Sevan/Akera ophiolites) extensions of the Northern Neotethys. This result requires the presence of a Northern Neotethyan oceanic crust of pre-Early Jurassic age, which in turn may suggest that oceanization of the IAE Ocean have occurred during the Late Triassic or earlier.