LA-ICP MS zircon dating, whole-rock and Sr-Nd-Pb-O isotope geochemistry of the Camibogazi pluton, Eastern Pontides, NE Turkey: Implications for lithospheric mantle and lower crustal sources in arc-related I-type magmatism

Abstract

Late Cretaceous I-type plutons are widespread in the Eastern Pontides, NE Turkey. The studied Camibogazi pluton is a composite pluton consisting of diorite, tonalite, monzodiorite, monzonite, quartz monzonite, granite, and mafic microgranular enclaves (MMEs). Laser ablation ICP-MS U-Pb dating of zircon yielded crystallization ages of 76.21 +/- 0.79 Ma, 75.65 +/- 0.50 Ma, 75.04 +/- 0.83 Ma, and 74.73 +/- 0.86 Ma for diorite, monzodiorite, monzonite, and granite, respectively. The rocks of the pluton have I-type, high-K to shoshonitic and metaluminous character, displaying whole-rock geochemical features of arc-related granites. They are enriched in large-ion lithophile and light rare-earth elements, and depleted in high-field-strength elements. Major element variations can be attributed to fractionation of plagioclase, clinopyroxene, homblende, and Fe-Ti oxides. The rocks show considerable variation in Sr-87/Sr-86((i)) (0.70498 to 0.70622), epsilon Nd-(i) (-2.79 to 036), delta O-18 values (+63 to +11.4) and Nd model ages (T-DM) (0.81 Ga to 126 Ga). Besides, they have (Pb-206/Pb-204) = 18.44-19.09, (Pb-207/Pb-204) = 15.64-15.69, and (Pb-208/Pb-204) = 3837-38.89. Although isotope signatures of the mafic microgranular enclaves (MMEs) (Sr-87/Sr-86((I)) = 0.70551 to 0.70622; epsilon Nd-(i) = 2.9 to 1.23; delta O-18 = +83 to + 9.7) are largely similar to the host rocks, MMEs are characterized by relatively high Mg-numbers (32-36), low contents of SiO2 (52-56 wt%) and low ASI (0.7-0.9). Estimated crystallization temperatures for the rocks of the pluton range from 735 +/- 58 C to 844 +/- 24 degrees C and a shallow intrusion depth (< 10 km) is estimated from Al-in-homblende thermobarometry. Whole-rock geochemical and isotopic data suggest magma generation by dehydration melting of an amphibolite-type lower crustal component with additional input of a subcontinental lithospheric mantle component. Furthermore, Sr-Nd isotope mixing model reveals similar to 30% to 40% lower crustal magma contribution to the mantle component C) 2014 Elsevier B.V. All rights reserved.