Calc-alkaline I-type plutons in the eastern Pontides, NE Turkey: Ux2013;Pb zircon ages, geochemical and Srx2013;Nd isotopic compositions
文摘
The Köprübaşı intrusion from the eastern Pontides of NE Turkey consists of granodiorite and monzogranite, and contains a number of mafic microgranular enclaves (MMEs). We report here Ux2013;Pb zircon age, geochemical and Srx2013;Nd isotopic data for these rocks in order to determining magma sources and magma production processes. On the basis of Ux2013;Pb zircon sensitive high-resolution ion microprobe dating (SHRIMP), the magma emplacement age of the granodiorite is 79.3 ± 1.4 Ma. The rocks of the pluton are calc-alkaline, metaluminous to peraluminous characteristics, and display features of I-type granites. They are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE) with negative Eu anomalies (Eu/Eu* = 0.60x2013;0.76), but are depleted in high field strength elements (HFSE). They have small range of up>87up>Sr/up>86up>Srub>(i)ub> (0.7067x2013;0.7070) and ub>Nd(i)ub> (−3.2 to −4.4) values. Fractionation of plagioclase, hornblende and Fex2013;Ti oxides played an important role in the evolution of the Köprübaşı intrusion. A relatively shallow intrusion depth (2x2013;8 km) was estimated from the Al-in-hornblende geobarometry. All these characteristics, combined with the low values of Kub>2ub>O/Naub>2ub>O, SiOub>2ub>, Alub>2ub>Oub>3ub>/(FeOup>Tup> + MgO + TiOub>2ub>) and (Naub>2ub>O + Kub>2ub>O)/(FeOup>Tup> + MgO + TiOub>2ub>), suggest an origin by dehydration melting from a metabasaltic lower crustal source.