Petrogenesis of Igneous Enclaves in Plutonic Rocks of the Central Anatolian Crystalline Complex, Turkey

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 from monzodiorite to granite) plutons of Central Anatolia: (1) 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 finegrained 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, 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