EXPERIMENTAL-STUDY OF URANIUM-LEAD ISOTOP E SYSTEM BEHAVIOR IN ZIRCONIN MELT UNDER DIFFERENT PHYSICAL-CHEMICAL CONDITIONS

Experimental study of zircon - granite and zircon - basalt systems has been undertaken in quartz ampoules at the temperature 1225 and 1280 d egrees C and atmospheric pressure (28 and 36 hours) as well as in plat inum ampoules at the temperature 1250 and 1300 degrees C, 3 kbar (8, 1 2, 17, and 32 hours). The goal of this investigation was to study the influence of physical-chemical parameters of magmatic melt on behavior of U-Pb isotope system of accessory zircons. It has been shown that a partially metamict zircon was recrystallized in the melt independent on the melt composition, T, P, and run duration. This recrystallizatio n is accompanied by impurities self-refining, especially radiogenic le ad. After the zircon recrystallization the retained Pb is well preserv ed in the structure and determines isotope memory of zircon xenocrysts age. This allows to solve genetic questions of melt evolution.