Authors
1
Department of Geology, University of Isfahan, Isfahan, Iran
2
Department of Geology, University Isfahan, Isfahan, Iran
3
Geochemistry Research Group, Academic Center for Education, Culture and Research (ACECR) on IUT, Isfahan, Iran
4
Geology Department, Faculty of Science, Isfahan University
Abstract
The study area is located in northwestern Nain (western central Iran), Isfahan province. The dominant igneous rocks in this locality comprise Tertiary volcanic units including basaltic andesite, andesite, and rhyolite, accompanied by pyroclastic deposits composed of tuff and ignimbrite. The presence of enriched large-ion lithophile elements (LILE) and light rare earth elements (LREE), and depleted high-field-strength elements (HFSE) in these rocks suggests a magmatic setting related to volcanic arc subduction. Petrological and geochemical investigations indicate that processes such as fractional crystallization (fractionations of plagioclase and, to a lesser extent, clinopyroxene), magma mixing, assimilation, and contamination play a significant role in the evolution of magmas in this area. The depletion in elements such as Nb, Ti, Ta, and Zr, as well as the low Ce/Pb and Nb/U ratios, along with high Ba/Nb and La/Nb ratios, are consistent with the effects of crustal contamination on the magmas. According to the geochemical findings, the primary magmas responsible for the volcanic rocks in the southern Shahrab area are most likely derived from the partial melting of the lithospheric mantle, which has been influenced by fluids derived from the subducted oceanic crust. During the ascent to shallower crustal levels and subsequent emplacement in a magmatic chamber before an eruption, these primary magmas interacted with basaltic magmas, resulting in the formation of various types of rocks in the area through fractional crystallization, assimilation, and contamination processes.
Keywords
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