Petrology
manijeh Asadpour; Soraya Heuss
Abstract
Acidic patches with alkali-granite nature have been intruded within the mafic rocks of the Qushchi complex (70 Km north of Urmia city). This area is northwestern part of the SSz zone with Precambrian basement. These granits have high amounts of K2O and SiO2 (over 70 wt%). Dating by U-Pb age of zircon ...
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Acidic patches with alkali-granite nature have been intruded within the mafic rocks of the Qushchi complex (70 Km north of Urmia city). This area is northwestern part of the SSz zone with Precambrian basement. These granits have high amounts of K2O and SiO2 (over 70 wt%). Dating by U-Pb age of zircon grains show 303.4 ± 2.2 Ma, indicating late Carboniferous - early Permian magma activity. The presence of older cores in some of zircon grains with age between 400 to 600 Ma, indicate presence of older rocks in the study area. The whole-rock isotopic analysis show negative initial Nd (t) = -1.3 with TDM = 1.61. These data provide evidence for partial melting of crust (with Neoproterozoic- Cambrian age) in early Permian. The 87Sr/86Sr = 0.752348 and εNd = -1.4 of whole rock and Th/U (>0.5) values in zircons show the involvement of more crustal and less mantle components, during the opening of Neo-Tethys Ocean. Due to the same mineralogical and geochemical composition and homogeneity with Qushchi granite, it is inferred that these patches are genetically related to Qushchi granite and are A type granite.
