Zircon U-Pb dating and geochemistry of Sarkhar and Bermani granitic rocks, East of Sangan iron mine, Khaf


Department of Geology, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, Iran


The Sarkhar and Bermani granitic rocks is located 300 km southeast of Mashhad, east of Sangan Mine, and northeastern Iran. Granitoid rock intruded older rocks such as crystalline limestone and dolomite and metavolcano-sedimentary rocks in the pre-Carbonifer age, and slate, quartzite, and conglomerate in the Carbonifer age. Monzogranite and syenogranite are two main intrusive rocks exposed in the study area. Biotite monzogranite porphyry and biotite microgranite are found mainly as dike cutting the intrusive rocks. The results of U-Pb zircon age dating of the monzogranite and syenogranite is 41 Ma (Middle Eocene). These intrusive rocks are older than granitoid associated with the Sangan mineralization. The texture of these rocks is hypidiomorphic granular and quartz, plagioclase, K-feldspar, hornblend, and biotite are the main minerals. Chemically, intrusive rocks are meta-aluminous to moderately peraluminous and shoshonitic. These intrusive rocks based on: K2O/Na2O= 1.3 to 2.2, Zr>200ppm, Nb>20 ppm, Ce>100 ppm, Y>30 ppm, Ga>20 ppm, and strong enrichment in REE specially in LREE plot in the field of A-type granite. However, the ratio of FeOt/FeOt+MgO is low (0.5 to 0.9) and they are magnesian character. Spider diagram normalized with average continental crust show enrichment in HFSE, Zr, Nb, Ga, Ta, Y, Hf and depletion in Ba and Sr. They belong to post orogenic granitoid. Granitoid associated with the magnetite mineralization at Sangan mine are I-type and originated from subduction zone. Granitoid rocks within the study area (east of Sangan mine) belonging to A2 group and generated by the magma from the continental crust.