U–Pb zircon dating, Sr-Nd whole-rock and Lu-Hf zircon isotope analyses of the Eocene Arslandede pluton, Eastern Pontides, NE Turkey: Implications for mantle source and magma evolution

Abstract

The Eastern Pontide Orogenic Belt (EPOB) hosts numerous plutonic bodies with different dimensions, compositions and ages ranging from Paleozoic to Late Eocene in NE Turkey. U-Pb zircon dating suggests that the Arslandede pluton crystallized at 44.50 ± 0.29 Ma, corresponding to the Lutetian (Middle Eocene) period. Rocks of this pluton have monzonitic character, with compositions ranging from monzodiorite to granite (SiO₂ = 49˗71 wt%). The studied monzonitic rocks have I-type, metaluminous and shoshonitic character and are enriched in large-ion lithophile elements (LILEs). The rare earth elements (REEs) have concave up shape (La_N/Yb_N = 6.64–11.57) and show negative to slightly positive Eu anomalies (Eu_N/Eu* = 0.37–1.24). ⁸⁷Sr/⁸⁶Sr_(i) values of 0.704801–0.705102 and εNd_(i) values of 1.01–1.34 correspond to the mantle series on isotope ratio diagrams. Positive εHf_(i) values (5.01–14.91) plot between the depleted mantle and the chondritic evolution lines. The petrological features of the rocks from the Arslandede pluton show that fractional crystallization with low rates of assimilation and/or magma mixing were effective during crystallization. All data show that the magma source of the pluton derived from an enriched lithospheric mantle and emplaced into the crust after differentiation in a deep seated magma chamber contaminated by relatively small proportions of crustal rocks.