Determining the physical crystallization condition of Lakhshak granodiorite pluton and its dykes

The Lakhshak pluton, a part of Zahedan-Saravan granitoid belt, is located about 15 km NW of the Zahedan city. The plutonic rocks are granodiorite in composition and are cut by a numerous of microdiorite and dacite dykes. The rocks of Lakhshak pluton consist of plagioclase (oligoclase-andesine), K-feldspar, quartz, biotite, amphibole (pargasite - edenite), sphene, apatite and opaque minerals. In this research, the composition of these minerals have been considered as the geo-thermometer and geo-barometer, hence they have good potential for calculating crystallization and emplacement conditions of a magma and tectonic setting. The presence of calcic amphiboles and primary biotite are evidence of Lakhshak pluton igneous origin (I). The amount of Altot in the pluton amphiboles are 1.02 to 1.32 representing the pluton emplacement at the depth of 3.8 to 8.4Km; while the core of those amphiboles analyzed from dikes contain Altot = 1.9-2.3 showing the depth of magma chamber in middle-lower crust (16.9-23 Km) as these dykes are thin and cooled fast after emplacment. The thermometry done on Lakhshak pluton and its dykes indicated cessation of exchange and equilibrium of minerals temperatures 645-732ºC for pluton, 730-824ºC for dacite dikes and for andesitic dikes are 808-945ºC. Moreover, biotites were plot in calc-alkaline field of Abdul Rahmans diagram, which represents the Lakhshak pluton might be formed in an active continental margin during the subduction of Sistan oceanic lithosphere beneath Afghan Block.