Writers : Soltani Dehnavi; Azam; Ghorbani, Mohammad Reza
Refference : 27th Symposium on geosciences and the 13th symposium on geological society of Iran-Tehran
Publishing Year : 1388

Abstract :

Tertiary volcanic rocks of the Southeastern part of Mashkan volcanic belt, NW Neyshabur, include caicalkaline rocks that embrace the compositional spectrum of trachybasalts, basaltic andesites, andesites and dacites. The rocks are characterized by high TiO2, P2O5, Zr abundances, no negative Eu anomalies and high Na/K, Nb/U, Nb/La ratios. The basaltic andesites have unusually high Nb concentrations so, we can call them Nb-enriched basaltic andesites. Normalized trace element patterns of the Mashkan basic volcanic rocks are comparable to the trace element patterns of subduction-related NEBs. There is an adakitic tendency in the medium to felsic range of Mashkan volcanic rocks; this implies that the adakitic melt has metasomatized the source mantle wedge of Nb-enriched basalts. In addition, the continuous compositional variation between adakites and NEBs confirms slab melt (adakitic melt) interaction with mantle peridotite. Low Sm/Yb and La/Yb contents do not confrim the present of amphibole in the sourse. While, partial melting of a garnet bearing spinel lehrzolite mantle look a reasonable model for the occurrence of these rocks.

Subject List : Andesit