Writers : Kheirkhah.M
Refference : Geosciences Scientific Quarterly Journal,No.:37-38,P.:60
Publishing Year : 1380

Abstract :

The Tudeshk area in southeastern part of Nain, Central Iran is located in Urmiyeh- Dokhtar magmatic belt and is a part of Kajar 1:100,000 map of GSI.
The stratigraphic sequnce is composed of Mesozoic and Cenozoic strata, consisting of Cretaceous limestone, Tertiary volcanic rockr (lavas and pyroclastics) and also Quaternary deposits.
The Neogene section is indicated by Upper Red Formation (URF), and a dacitic (Ngd(, unit. The rock type variations in Neogene volconics along with the geochemical and petrographic evidences indicate a kind of sodic character. Mixing and fractional crystalization ir magmas, are important, phenomena which has been resulted in this study.
Along with the above processes, the associated basic rocks have been strongly altered, caused by fluid pressures, high temperaturer
and the nature of late fumarolic fluids. This area has been subjected to a fault and fracture system with a NW-SW trend, indicates that th area has passed a brittle type tectonic regime, which followes the main trend of Urmiyeh-Dkhtar magmatic belt. This kind of extensiona tectonic regime controlled the emplacement of igneous rocks The geochemical characteristics of basalts in Tudashak area (drown as spide diagrams in special cases) has been compared with the basaltic rock-typs in orther places of the world as: Parana (South America), Ric Grande (North America), Deccan (India) and Ethiopia. All of analyis results plot in subalkaline field of diagram, indicating contamination witf amphibolitic genisses of sialic crust during the initial stages of ascending. similarity with the Tudashak Neogene basalts show a considerabh similarity with the Rio Grande Basalts and form this point of view. It could be deduced that the partial melting of a depleted mantle ir responsible for the formation of this basalts, and has a similarity to the steans Basalts of North America Basin and Range

Subject List : , volcanic rocks