Evidence for Continuous Mixing of Individually Fractionated, Coeval Felsic and Mafic Magmas Forming Synextensional Plutons, the Menderes Core Complex, Western Turkey

The Erigoz and Koyunoba monzogranites in western Turkey contain igneous enclaves that provide important information concerning the magma-forming processes and their petrogenetic origin in a core-complex setting. The Erigoz monzogranite differs from the Koyunoba monzogranite in that it displays a porphyritic texture and contains abundant amphibole and allanite. In addition, two mineralogically contrasting groups of igneous enclaves have also been distinguished in the Erigoz and Koyunoba monzogranites; one group contains both hornblende and biotite, while the only mafic mineral in the other group is biotite. The host rocks and igneous enclaves are compositionally calc-alkaline and metaluminous to slightly peraluminous and belong to the I-type class of granites. The geochemical signatures of the host rocks and igneous enclaves are largely similar, but some enclaves contain high Al2O3, Fe2O3, MgO, CaO, TiO2, MnO, P2O5, Na2O, Mg#, Cu, Zn, Ni, Ga, Nb, V, Ti, and Zr and low SiO2, K2O, and Th contents. The igneous enclaves are strongly depleted in Ba and light rare earth elements (REEs) and moderately depleted in heavy REEs, Nb, P, and Ti with respect to their host rocks. The Koyunoba monzogranite and associated igneous enclaves represent both the most evolved magma and the late stages of crystallization. This study suggests that the progressive fractionation and continuous mixing/mingling of coeval crustal and mantle magmas are important in defining the near-final composition of these granitoid magmas and their igneous enclaves. The host rocks and igneous enclaves have partly overlapping Sr-87/Sr-86(I), epsilon Nd-I, and Pb isotope values that indicate a contribution from crustal assimilation. Development of these processes in synextensional granitoids is consistent with a geodynamic model involving slab rollback-induced asthenospheric upwelling as a heat source, which caused melting and mixing of lower crustal and lithospheric mantle. Rollback-induced extension also played a fundamental role in the generation of conduits for the entry of high-K, mantle-derived mafic melts into the large felsic-magma reservoirs

Petrology, mineral chemistry and Sr-Nd-Pb isotopic compositions of granitoids in the central Menderes metamorphic core complex: Constraints on the evolution of Aegean lithosphere slab

Plutonic associations in the central Menderes metamorphic core complex are suitable rocks in order to understand the magma forming processes in extended terrains. Syn-extensional Salihli and Turgutlu granitoids have granodioritic composition and contain monzonitic and monzodioritic microgranular enclaves. They are transitional metaluminous/peraluminous and high-K calc-alkaline in character and are located on 1- and S-type transition. Salihli and Turgutlu granodiorites are geochemically similar to each other while their microgranular enclave chemistry is in contrast with low SiO2 and high Mg # values. Mineral chemistry data from granodiorites and mafic microgranular enclaves confirm their shallow emplacement at about 7 km. Geochemical modelling suggests that syn-extensional granitoids were derived from the mixing of mantle and lower crustal components, which were finally modified by a significant amount of upper crustal contamination and fractional crystallization processes at shallow crustal levels. Early-Middle Miocene syn-extensional granitoids across the Aegean region form a magmatic belt associated with roll-back of the Aegean lithosphere slab. Roll-back induced magmatism together with ductile deformation in western Turkey ceased after cooling of the Salihli granodiorites at 12.2 Ma. But core-complex related magmatism was continuous in the Cycladic metamorphic core complex during Late Miocene and was followed by an active arc volcanism in the southern Aegean. Such abrupt change from ductile to brittle mode of extension in western Turkey can be explained by opening of a slab window on the Aegean lithosphere slab, which would lead to upwelling of fertile subslab asthenospheric mantle, forming transitional and finally OIB-type basalts. (C) 2013 Elsevier B.V. All rights reserved

Geochemistry of I-type granitoids in the Karaburun Peninsula, West Turkey: Evidence for Triassic continental arc magmatism following closure of the Palaeotethys

Triassic granitoids related to Palaeo- and Neo-Tethyan events occur widely in the metamorphic terranes largely affected by the Alpine orogeny. A first recorded unmetamorphosed plutonic body intruded into the Palaeotethyan melange in western Turkey, called the Karaburun granodiorite, is composed of two small intrusive stocks that were emplaced between 240 and 220 Ma. It is compositionally diverse, ranging from granodiorite and tonalite to diorite. These rocks show heterogeneous compositions with 54 to 65 wt % SiO2 and are calc-alkaline in character. They are also subalkaline with molar ratios of Al2O3/(Na2O + K2O) from 0.74 to 1.00 and are metaluminous. Most samples are diopside-normative (0.36-8.64), with Na2O > K2O. Chondrite normalized rare earth element (REE) patterns show various degrees of light REE (LREE) enrichment, with La-N = 57.79 to 99.59 and (La/Yb)(N) = 5.98-7.85 and Eu negative anomalies (Eu/Eu* = 0.62-0.86). These rocks have coherent patterns in ocean ridge granite (ORG) normalized trace-element plots, marked by variable enrichment in K, Rb, Ba, Th, Ce and depletion in Ta and Nb, similar to I-type granites from subduction zones. In primitive mantle-normalized multi element variation diagrams, the granodiorites show pronounced depletions in the high-field-strength elements (HFSE; Nb, Ta, Zr), Sr, P, and Ti. Trace-element modeling of the Karaburun granodiorite suggests an origin through partial melting of the subduction-modified mantle wedge with minor contribution of crustal components through a process of strong fractional crystallization (FC) combined with slight assimilation-fractional crystallization (AFC). Exposures of typical continental-arc granodiorites in the Karaburun Melange support the validity of the subduction-accretion model that implies the presence of an active continental margin following closure of the Palaeotethyan Ocean during the Triassic

New national and regional bryophyte records, 67

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