Complex compositional zoning in clinopyroxene in Late Cretaceous potassic-alkaline volcanic rocks from northern Turkey
Waters, Frank E
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Textural signatures and compositional variations in major, minor, and trace elements within individual phenocrysts are strong indicators of changing conditions in a crystallizing magma chamber, potentially caused by open system processes. The clinopyroxenes from a series of mafic potassic lava flows and dikes from north-central Turkey show exceptional examples of such textural and chemical zonation patterns. The lava flows and dikes come from a Late Cretaceous continental magmatic arc on the southern edge of Laurasia formed from the subduction of Neotethyan oceanic crust. Two main rock groups were observed in the mafic potassic rocks: leucitites and minettes. The leucitites display more complex intra-phenocryst textural features including repeating layers of differing compositions and have more varied clinopyroxene populations. The observed textural and compositional variations in the clinopyroxenes suggest the influence of magma mixing induced convection in the evolution of the mafic potassic rocks of the Pontide Arc.