SM-ND AGE AND GEOCHEMISTRY OF GRANULITES FROM THE CENTRAL PART OF ANABAR SHIELD

Geochemistry and isotopic systems of Sm-Nd and Rb-Sr in rocks and mine rals from the Daldyn series of Anabar Shield metamorphosed in granulit e stage were studied. Petrochemical and isotope-geochemical data show that komatiites may serve as a pre-metamorphic substrate for metaultra basites of the shield. As can be concluded from the contents and, dist ributions of petrogenic, rare earth and other immobile elements the to leiitic metabasites can be compared with modem basalts of spreading zo nes. Eight whole rock samples of toleiitic and subalkaline metabasites , metaultrabasites and plagiogneises define an isochrone (3085 +/- 75 m.y., epsilon(Nd)T = 3.1 +/- 1.4) corresponding to the age of the magm atic protolith eruption. Low initial Sr-87/Sr-86 values (less-than-or- equal-to 0.702) measured for three of these samples show their mantle sources or insignificant role of crustal material in their genesis. Th e age of regressive metamorphism of these rocks (1870 +/- 20 m.y.) is determined by using the Sm-Nd mineral isochrone for metabasites (pyrox ene, plagioclase, garnet, WR).