Petrogenisis of Mafic- intermediate Magmatism, East of Sanandaj; A New approach with careful monitoring of geochemical evidences

Abstract

The East Sanadaj magmatic rocks of the northern Sanandaj-Sirjan Zone, part of Zagros Orogen, comprise several intrusive bodies that were generated during northeastward subduction of Neo-tethys beneath the Iranian sector of the Eurasian plate. From the east Sanadaj to Galali, mafic- intermediate intrusions of Late Jurassic age, have significant out crops in Kangareh, Saranjianeh, Ghorveh, Shanevareh and Galali. These rocks are calc-alkaline, metaluminous (ASI=0.51-0.95) and mostly magnesisan. As SiO2 increases, the chemistry of rocks changes to ferroan and high-K. These rocks present enrichment of LILE relative to HFSE, the low LREE/HREE fractionation ((La/Lu)N=1.5-14.6) considerably flatter chondrite-normalized REE profiles, Eu positive anomaly (Eu/Eu*= +0.63-+3.75). Primitive features of Sr - Nd isotopes Combined with HFSE and REE ratios, as source indicators, prove the mantle derived magma as a source of these rocks. Geochemical modelings indicate mafic- intermediate rocks of east Sanadaj, originated from spinel lherzolithic magma with hydrous components such as amphibole. Fractionation of these hydrous minerals have important role in evolution of magma. The combined monitoring of geochemical data and REE patterns, isotopic data were performed in order to unravel the compositional changes from calc-alkaline-magnesisn rocks to high alkaline-ferroan rocks of this area. The results denied bimodality of source magma and confirmed the important role of differentiation in magma evolution.

Keywords

• mafic magmatism
• geochemistry
• ree
• nd-sr isotopes
• petrogenesis
• east of sanandaj
• sanandaj-sirjan zone