Neybaz Metamorphic Core Complex, Western Domain of the Central Iranian Microcontinent: Tectonics, Petrostructural Properties and Geochemical Analysis

Abstract

Abstract: The Neybaz Metamorphic Core Complex (NMCC), situated in the West Central Iranian Microcontinent, is a high-grade metamorphic zone composed of diverse lithologies ranging from Precambrian to Cenozoic in age. It has undergone multiple deformation phases, evidenced by tight isoclinal, overturned, and recumbent folds, boudins, fold interference patterns, and significant variation in fold geometry. The region displays signs of both compressional and extensional tectonics: intense folding and thrusting reflect contraction, while boudinage indicates extension. Shear-related fabrics such as sigma- and delta-structures and sheath folds further suggest concurrent shearing. Quantitative fold analysis reveals an average shortening of 72.43%, pointing to intense deformation. Metamorphism peaked at granulite facies, with widespread migmatitization resulting from partial melting of gneisses and amphibolites. While most rocks have a magmatic protolith, some exhibit sedimentary origins. Melt formation depths vary, extending beyond 40 km. Geochemical signatures, including trace element and Rare Earth Elements (REE) anomalies, suggest a mixed mantle-crustal source influenced by subduction, crustal assimilation, fractional crystallization, and partial melting. The tectonic settings of rock emplacement span magmatic arcs, mid-ocean ridges, and orogenic belts, underscoring the NMCC’s complex, multi-stage evolution. Unlike classical Cordilleran core complexes, the Neybaz Complex reflects both contractional and extensional tectonic regimes, classifying it as a transitional core complex. © Pleiades Publishing, Ltd. 2025.