تأثیر هوازدگی بر کانی‌شناسی و ژئوشیمی گرانیتوئیدهای ده نو (شمال شرق الیگودرز)

The Dehno Granites are located 20 Km northeast of Aligudarz. They are one of the four separated plutonic masses, exposed in the Sanandaj – Sirjan Zone. These rocks are composed of granodiorite and tonalite covered by granite arens. The main minerals of these rocks are quartz, plagioclase, biotite, muscovite and accessory minerals such as sphene, apatite, epidote, zircon, rutile and opaques. By using equation of change percentage (%change=[(RW-RP)/RP]100), the changes of the elements content in the weathered and fresh rocks were determined and compared. According to this equation, the Si, Al, Na, K, P, Ba, Rb, Zr, Ta, Fe3+, Nb, Y and U concentrations are decreased whereas Mg is increased. Fe2+, Sr and Ca show various trends in the weathered samples compare to the parent rocks. The elements such as Hf, Y and Ta display the least changes in different depths. The chondrite – normalized REE's show decreasing trend indicating that the LREE's content in comparison to HREE's are enriched and concentrated in the weathering products rather than in fresh rocks. This may be due to surface absorption of clay minerals. In the weathered samples, Eu and Ce show depletion and slightly positive anomaly respectively. Depletion in Eu is likely caused by alteration of feldspars.