GEOCHEMICAL TYPES OF CRETACEOUS GRANITIC- ROCKS OF NORTHEASTERN RUSSIA

New data on the distribution of trace elements in the rocks of volcano -plutonic associations from the Cretaceous active continental margin o f northeastern Russia were obtained. The volcanic and plutonic facies of the Okhotsk-Chukotka Volcanic Belt (OCVB) are shown to a be geochem ically identical, Both facies form parts of the same differentiation s eries, in which the rocks with the same silica contents have similar t race-element compositions. The abundances of volatile components (F an d B) are critical for the distribution of trace elements in granitic r ocks, The leucogranites of Omsukchan district that are enriched in F a nd B bear a rare metal mineralization. The Rb versus (Nb + Y) plot was used to geochemically discriminate Cretaceous granitic rocks from nor theastern Russia. Subduction-related and intraplate granites were dist inguished. The former display an extremely low Nb content (< 10 ppm), Using geochemical fingerprints, the subduction-related granitic rocks were subdivided into an island-are group (Anadyr' area) and an active continental margin group (OCVB). The comparison of subduction-related granitic rocks from northeastern Russia with their collisional counter parts (the Main Batholithic Belt of eastern Yakutia) has shown that th e subduction-related granites are slightly enriched in Mg and Cr and d epleted in K and Rb. This is because their mineral assemblages origina ted ata higher temperature.