پتروژنز سنگ‌های آتشفشانی پلیوسن- کواترنری در استان اصفهان: با نگرشی برماگماتیسم آداکیتی

The Pliocene calc-alkaline volcanic rocks are exposed in two areas in southeast and northwest of Isfahan and consist of andesites and dacites. Based on geochemical data and multi- elements pattern, these rocks are medium to high calc-alkaline suite and they show LILE and LREE enriched normalized multi-element patterns, and negative Nb and Ti. Condrite-normalized REE patterns display a steep decrease from LREE to HREE without any Eu anomaly. They have higher SiO2 and Sr content and Sr/Y and La/Yb ratios and low MgO, Mg#, Y and Yb contents than the normal calc-alkaline volcanic rocks. These volcanic rocks show adakite characteristics. These features are consistent with ratios obtained from orogenic related volcanic rocks. These rocks may have been produced by partial melting of thickened lower continental crust or slab probably transformed to eclogite or garnet -amphibolite. HREE and Y depleted pattern suggest the existence of garnet and amphibole as a residue in the source.