Application of mineralogical and textural evidence forrecognition of alkaline metasomatism in Dodebak granitoidstock (NE Mabalat)

Dodehak granitoid stock with tonalite to granodiorite compos ition is exposed south of Dodehak vi llage, north of Ab-e-Gann (Mahalat) in Urumieh-Dorhtar volcanic belt of Iran. Based on petrography and point analysis (EPMA). plagioclase crystals show nonnal zoning with graph ic tex.ture is present. Samples from SE of the intrus ion are different and myrmekite texture is present in the rocks, while graph ic texture is absent and plagioc lases have lost their zon ing. In samples from SE of the area. mynnekite is rim type and plagioc lases show cross shape twinning. Based on whole rock XRF analyses, Rb-S i~ and K20 -Na10 diagrams show nonlinear trends and EPMA analysis indicate that plagioc lases are homogeneous albite. Such petrographical and geochemical features are evidence for alkaline metasomatism in SE of the Dodehak intrus ion.