ISOTOPIC INHOMOGENEITY OF SOURCES OF LATE PALEOZOIC INTRAPLATE MAGMATISM IN CENTRAL-ASIA (BASED ON SR AND ND ISOTOPE DATA FOR BASALIS OF BIMODAL ASSOCIATIONS)

Study is given to isotope composition (Sr, Nd) of basalts of bimodal a ssociations of the Late Paleozoic rift system in Central Asia. It has been established that this composition is relatively stable in the str ike of separate rift zones and in significantly different zones. Varia tions of isotope compositions are estimated in the context of mixing o f two isotope sources with drastically different isotope parameters in chambers of magma generation. It is shown that the regional crust cou ld not influence changes of isotope composition, Therefore, it is supp osed that the melt source was the MORB-type depleted mantle and the EM -II-type mantle enriched mainly in Sr-87.