CORRELATION BETWEEN THE WONOMINTA AND THE BROKEN-HILL BLOCKS IN WESTERN NEW-SOUTH-WALES - EVIDENCE FROM ND ISOTOPE STUDIES OF METASEDIMENTS

Nd isotope studies of the oldest metasedimentary rocks from the Wonomi nta Block, western New South Wales reveal that these samples have a mo del age (TDM) Of 1780-2010 Ma, slightly younger than that of low-grade Willyama Supergroup metasediments (1920-2160 Ma), and significantly y ounger than those ages previously reported from high-grade rocks of th e Broken Hill Block (2200-2300 Ma). These differences have important i mplications for tectonic reconstruction in this region and support a m odel of transitional tectonics from the Broken Hill to Wonominta Block s, as suggested by earlier geochemical studies of mafic rocks. Those s tudies revealed that the mafic rocks from the basal sequence of the Wo nominta Block may have formed in a backarc basin, developed from a pro pagating rifting, an environment contiguous to that in which Willyama Supergroup was deposited. These results also carry significant implica tions for tectonic reconstruction of eastern Australia.