بررسی منطقه ای گرانیتوئیدهای ترشیری زون البرز-آذربایجان نگرشی ویژه بر پتروژنز آنها

Alborz-Azarbaijan granitoids in north of <?xml:namespace prefix = st۱ ns = "urn:schemas-microsoft-com:office:smarttags" />iran۱:place>۱:country-region> were emplaced discontinuously along East-West trend during several magmatic pulses. The main rock types are granodiorite and monzonite and others such as granite and diorite are rare.Plagioclase, K-feldspar, quartz, hornblende and occasionally clinopyroxene are the main minerals of these rocks and accessory phases are titanite, apatite, zircon and magnetite. Classification by the Al Saturation index (ASI=molar Al_۲O_۳/Na_۲O+K_۲O+CaO) of the Chappell and White (۱۹۷۴) for this rocks indicates metaluminous to mildly peraluminous character that consistents with I-type and A-type granites. Alborz-Azarbaijan granitoids were formed in Arc Related (AR) tectonic setting and Y verses Zr diagram of Muller (۱۹۹۷), confirms this character. Distingshing of tectonic setting from Y verses SiO_۲ diagram of Pearce et al., (۱۹۸۴), indicates both VAG and WPG fields for these rocks. Similar result obtained from Rb verses Y+Nb diagram, that consistents with post collision granite field of Pearce (۱۹۹۶). On the bases of geological, petrographical and mineralogical evidence of Alborz-Azarbaijan granitoids, the simplest model is suggested for origion of these rocks, is post-collision. Eocene-Oligocene Post-collision magmatism of Alborz-Azarbaijan is occurred after ending of subduction and continental collision of Neo-tethys in Upper Cretaceous-Paleocene. The basic magma is generated from partial melting of metasomatised mantle then in the way up to continental crust, it melt the crustal rocks and acidic rocks are formed. Differentiation of magma and mixing of basic and acidic melts induced generation of various rocks with different compositions.

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