Geochemistry of Bezow-Daghi volcanic rocks, Urmia adakitic magmatism in the Uromieh-Dokhtar magmatic belt


Department of Geology, Faculty of Sciences, Urmia University, Urmia, Iran


The Bezow-Daghi area is located in the west side of Urmia Lake and northeast of Urmia Town. In the area an individual volcanic dome is observed which is accompanied by different pyroclastic and volcanic products (acidic to intermediate composition) mainly dacite. The major minerals are plagioclase and amphibole set in the microlitic to hyaline matrix. Geochemical studies show that the rocks are dacite with high potassic calc-alkaline to shoshonitic affinity. LREE/HREE ratio is high (La N/Yb N≈20). Depletion in HREE, HFSE and TNT contrary to LILE and Sr enrichment and VAG setting are the significant features of these rocks. Detail investigations on the rocks studied confirmed that the dacites are HSA type adakite and its magma is generated as a result of partial melting of subducted slab (eclogite) and overlying sediments during post-collisional period. All geochemical characteristics reported for adakite, in the petrologic literatures, are well consistent with those of Bezow-Daghi adakites i.e. Sr>400 ppm, MgO15% and SiO2>56%, enrichment in LREE and LILE, depletion in HREE and Y and high ratio of La/Yb>20 and Sr/Y>40.