Zirconolite, CaZrTi_2O_7, re-examined from its type locality at Afrikanda, Kola Peninsula, Russia and some Synroc Implications

摘要

Zirconolite of BORODIN et al. (1956) from type locality at Afrikanda, Kola Peninsula, Russia, consists of a core of cal-zirtite and baddeleyite, and a rim composed of an initial CaZrTi_2O_7 phase and various secondary minerals. This initial phase is both sector zoned and oscillatory zoned, and has variable composition. The principal substitutions are as follows: REE + Ti mutually impiles Ca + Me~(5+); Me~(6+) + Me~(2+) mutually impiles 2Ti; ACT~(4+) + Me~(2+) mutually impiles Ca + Ti. Alteration of the initial phase is characterised by introduction of Si, H_2O, Ba, Th and U, loss of Ca, Fe, Ti and Zr, and little change in Nb and REE. Zirconolite is an important constituent of Synroc, and it could easily be replaced by Si-bearing phases that concentrate U and Th much more then in initial ceramic material.