Classification and Generation of the Enclaves in Karapınar-Karacadağ Volcanic Rocks

Abstract

Karapınar-Karacadağ Volcanic Rocks (KKVR) have very complex magmatic history and outcropped the southwestern part of the Cappadocia Volcanic Province (Central Anatolia). Here we present the petrography and whole-rock chemistry of the enclavebearing rocks to constrain their source and evolution history. These petrographic observation and geochemical data reveal that the enclaves in the Karapınar-Karacadağ volcanic rocks are magma mixing/mingling enclaves (MME), magma segregation enclaves (MSE), and xenoliths. Here we discriminated these enclaves into eight different types according to their mineral composition and textural features. The magma mixing/mingling enclaves (Type 1, 7, 8) are the mixing products of coeval more felsic and mafic magmas. They show hypocrystalline porphyritic, holocrystalline granular, and intergranular textures, and rich in mafic minerals, and have characteristic petrographic features such as quenched amphibole, bladed biotite, ocelli-quartz, sieved and cellular plagioclases. In andesites they range from basalt to andesite in composition. However, in basalts, they are in basaltic composition. The magma segregation enclaves (Type 2, 4, 5, 6), which are observed in almost all the KKVRs, are cognate xenolith because of plucking from the different parts of the magma chamber. They are holocrystalline and granular in texture. The magma segregation enclaves contained in the andesitic host rocks are hornblende gabbro and pyroxene gabbro in composition, whereas in the basaltic host rocks they are dunite, lherzolite, and basalt in composition. The xenolithic enclaves (Type 3) are observed in the basalts as quartz, plagioclase, biotite, and amphibole xenocrysts. Major oxides and trace element data of the studied rocks indicate that the MSEs are more primitive than their host rocks, and all of the enclaves (MME-MSE) are in accordance with their hosts. According to petrographic observations and geochemical data we propose that fractional crystallization, magma mixing and assimilation processes have a key role in the evolution of the KKVRs and their enclaves.