The Jurassic volcanic rocks in the centre of the northern zone (south of Trabzon City) provide important constraints on the evolution of Pontides. The investigated volcanic rocks form a transitional series between tholeiitic and calc-alkaline, and is dominated by basalt, basaltic andesite and andesite. Geochemically, they are enriched in LILE and LREE contents and depleted in HFSE [(La/Yb)_N= 2.2 - 8.5; (Nb/La)_N= 0.1 - 0.77)] compared to mid-ocean ridge basalts and have radiogenic Nd isotope ratios of \epsilonNd(210 Ma)= -0.72 to 3.24. These trace element and isotope data suggest that these rocks were derived from low degrees of partial melting of spinel lherzolite that was metasomatized by subduction-related fluids and further underwent a degree of fractional crystallization in magma chambers before being extruded at the surface.
ŞEN, CÜNEYT (2007) "Jurassic Volcanism in the Eastern Pontides: Is it Rift Related or Subduction Related?," Turkish Journal of Earth Sciences: Vol. 16: No. 4, Article 6. Available at: https://journals.tubitak.gov.tr/earth/vol16/iss4/6