Original paper

Geochemical and isotopic constraints on the genesis of the Late Palaeozoic Deliktas and Sivrikaya granites from the Kastamonu granitoid belt (Central Pontides, Turkey)

Nzegge, O.M.; Satir, M.; Siebel, W.; Taubald, H.


The Late Palaeozoic Sivrikaya and Deliktaş granitoids of the Kastamonu granitoid belt (KGB) are of sub-alkaline affinity, belong to the high-K calc-alkaline series and display features of transitional to S-type granites. Sivrikaya granitoid is host to biotite-hornblende granodiorite-tonalite and minor two-mica granites. The rocks are 303-300 Ma old, have low initial 87Sr/86Sr ratios (0.7041-0.708), moderately low εNd(t) values (−1 to −3.8) and young TDM model ages (0.75 to 1.08 Ga). All these characteristics, combined with low Al2O3/(FeO + MgO + TiO2) and (Na2O + K2O)/(FeO + MgO + TiO2) and δ18O values of 10-11.6‰ point to dehydration melting of heterogeneous protoliths dominated by amphibolite and greywackes-type sources with mantle contribution. Chondrite-normalized REE patterns of the Sivrikaya rocks are characterized by concave-upward patterns suggesting that amphibole played a more significant role than garnet during magma segregation. The main portion of the Deliktaş granitoid consists of peraluminous muscovite-rich monzogranite. Compared to Sivrikaya, rocks from this pluton have higher initial Sr ratios (0.7109-0.7185), older Nd model ages (1.2 to 2.2 Ga) and similar εNd(t) values (−2.0 to −4.7). U-Pb zircon analyses give an age range of 295-275 Ma. The nearly constant δ18O values (∼11.5 to 11.7‰) in conjunction with the chemical characteristics indicate a predominantly pelitic source similar to the basement, which consists of felsic high-grade granulite-facies metasedimentary rocks, of continental origin.


nw turkeycentral pontideskastamonu granitoid beltpalaeotethyshercynian magmatismgenesisvagvolcanic-arc granitoidssrndo-isotopes