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    Geochemical characteristics of cretaceous collision-related plutonism in Turkey
    (Pergamon-Elsevier Science Ltd, 2002) Ilbeyli, N; Pearce, JA
    [Abstract Not Available]
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    Petrogenesis of collision-related plutonics in Central Anatolia, Turkey
    (Elsevier Science Bv, 2004) Ilbeyli, N; Pearce, JA; Thirlwall, MF; Mitchell, JG
    Central Anatolia exhibits good examples of calc-alkaline and alkaline magmatism of similar age in a collision-related tectonic setting (continent-island arc collision). In the Central Anatolia region, late Cretaceous post-collisional plutonic rocks intrude Palaeozoic-Mesozoic metamorphic rocks overthrust by Upper Cretaceous ophiolithic units to Make up the Central Anatolian Crystalline Complex. In the complex, three different intrusive rock types may be recognised based on their geochemical characteristics: (i) calc-alkaline (Behrekdag, Cefalikdag, and Celebi) (ii) subalkaline-transitional (Baranadag); and (ii) alkaline (Hamit). The calc-alkaline and subalkaline plutonic rocks are metaluminous I-type plutons ranging from monzodiorite to granite. The alkaline plutonic rocks are metaluminous to peralkaline plutons, predominantly A-type, ranging from nepheline monzosyenite to quartz syenite. All intrusive rocks show enrichment in LILE and LREE relative to HFSE, and have high Sr-87/(SR)-S-86 and low Nd-143/Nd-144 ratios. These characteristics indicate an enriched mantle Source region(s) carrying a subduction component inherited from pre-collision subduction events. The tectonic discrimination diagram of Rb vs. (Y+Nb) suggests that the calc-alkaline, subalkaline, and alkaline plutonic rocks have been affected by crustal assimilation combined with fractional crystallisation processes. The coexistence of calc-alkaline and alkaline magmatisin in the Central Anatolian Crystalline Complex may be attributed to mantle source heterogeneity before collision. The former carries a smaller intraplate component and pre-subduction enrichment compared to the latter. Either thermal perturbation of the metasomatised lithosphere by delamination of the thermal boundary layer (TBL), or removal of a subducted plate (slab breakoff) is the likely mechanism for the initiation of the post-collisional magmatism in the Complex. (C) 2003 Elsevier B.V. All rights reserved.
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    Petrogenesis of igneous enclaves in plutonic rocks of the Central Anatolian Crystalline Complex, Turkey
    (Taylor & Francis Inc, 2005) Ilbeyli, N; Pearce, JA
    The Central Anatolian Crystalline Complex (CACC) contains Paleozoic-Mesozoic, medium-high grade metamorphic rocks overthrust by Upper Cretaceous ophiolitic units and intruded by a number of plutons (around 79.5 to 66.6 Ma). Central Anatolia exhibits good examples of calc-alkaline and alkaline magmatism of similar age in a collision-related tectonic setting. Igneous enclaves are widespread in these calc-alkaline plutonic rocks of the CACC. Two types of igneous enclave have been recognized in the calc-alkaline Behrekdag, Cefalikdag, and Celebi (BCC) (metaluminous I-type ranging front monzodiorite to granite) plutons of Central Anatolia: (I) fine-grained (Type-I); and (2) medium-grained to porphyritic with feldspar megacrysts (Type-II). Most abundant are Type-I enclaves with quartz dioritic to quartz monzodioritic compositions (SiO2 = 55 to 66 wt%) and fine-grained margins indicating chilling against the host rocks. Less common are Type-II enclaves with quartz dioritic to gabbro compositions (SiO2 = 42 to 59 wt%) and cumulate to porphyritic textures, 2 reflecting accumulation of early precipitating phases. Both sets of enclave have mineral phases similar to that, of the host rocks, but, with different mineral proportions. The origin and evolution of the enclaves are strongly linked to those of their host rocks. For example, mafic to intermediate Type-I enclaves (originated from magma mixing/mingling) in the BCC plutonic rocks indicate interaction between silicic magmas and mantle-derived melts. Their presence could imply that the host plutonic rocks have undergone hybridization to a greater or lesser extent. In contrast, mafic Type-II enclaves (formed as cumulates of early crystallized minerals) provide information on the parental magma of the plutonic rocks.