Abstarct: The ۴۳ Ma Gapdan pluton located at NW of Zahedan is a part of Sistan Suture zone, Eastern Iran. The pluton is lithologically heterogeneous, and consists of granodiorite at center and biotite granite at margin, which were cut by several microdiorite dykes. The pluton consists of plagioclase, quartz, K-feldspar, biotite, Fe-Ti oxide, zircon, apatite and alanite. The Gapdan rocks are mainly granular in texture, although they also show poikilitic, perthite and myrmekitic textures. Its country rocks are low to medium grade mextamorphic rocks dominantly include biotite schist with subordinate amphibolite. Moreover, the Gapdan pluton hosts lots of enclaves from igneous and sedimentary origins that concentrate mostly in pluton margin. They are often surmicaceous and have an enrich laxyer of biotite in their margins. The enclaves are fine grain and consist of plagioclase+quartz+biotite ± epidote. Biotite is the only ferromagnesian mineral in the Gapdan granitoids, crystallized in ~ ۸۵۰˚C and suggests the granitoids are calc-alkaline and I-type, formed in an arc-related tectonic setting. baxsed on AlT in biotite, the Gapdan biotite granites crystallized in ۴-۵.۴ Km depth and granodiorites in ۱.۷- ۳.۳ km, supported by calculated depth for the Gapdan country rocks baxsed on Al-in-hornblende barometer. Plagioclase in the Gapdan biotite granites are mainly andesine, and in granodiorites are from oligoclase to labradorite. Two-feldspar thermometry indicates the temperatures of and ~۷۳۴- ۷۴۷˚C for crystallization of biotite granites and ۵۵۵-۶۶۱˚C for granodiorites. The obtained temperatures for granodiorites are lower than granite solidus and might be related to feldspar reequilibrium in sub-solidus field. baxsed on the field and petrography observations and mineral chemistry, it seems that the basaltic magma produced by partial melting of the mextasomatised mantle peridotites, intruded in the continental crust and provided a sufficient heat for partial melting of the crustal materials. Mixing of the differentiated basaltic and granitic melts produced hybrid magma(s). The hybrid magma(s) contaminated a lot with crustal sediments during ascending and especially at the emplacement stage, support by lots of mextasedimentary enclaves of schist and surmicaceous presented in the pluton. The analyzed amphiboles belong to calcic amphibole, in which they are mostly kaersutite and magnesio-hestingsite in dykes and magnesio-hornblende in amphibolites. Al in amphibole thermo-barometers suggest the initial crystallization temperature and pressure are ۸۹۴ °C at a depth of ۲۳.۳km for magnesio-hastingsite in dykes which followed by kaersutite crystallization during the decreasing temperature up to ۷۴۴ °C at ۱۲.۳ km depth.