MATCHING GONDWANALAND FRAGMENTS - THE SIGNIFICANCE OF GRANITOID VEINSAND TECTONIC STRUCTURES IN THE CAPE LEEUWIN-CAPE NATURALISTE TERRANE,SW AUSTRALIA

There are many generations of leucocratic neosome in the Late Pan-Afri can gneissic terrane between Cape Leeuwin and Cape Naturaliste at the southwestern extremity of Australia. In polyphase-deformed amphibolite -granulite facies rocks, successively-formed neosomes are expressed as early lit-par-lit veins and diffuse patches followed by agmatite and, later in the structural evolution, by at least four phases of pegmati te injection. These neosomes have been integrated into the structural succession and contribute to the tectonic fingerprint of the terrane. Late Pan-African granite-aplite-pegmatite also occurs in both NE India and East Antarctica, which represent other fragments of Gondwanaland, previously juxtaposed with SW Australia. Furthermore, in the Eastern Ghats, India there is evidence for reheating (to > 500 degrees C) at 5 50 Ma and crustal cooling to ca 350 degrees C at 500 Ma. A model to ac count for correspondence of the igneous histories of these marginal pa rts of the three Gondwanaland fragments is that of (1) the emplacement at depth of granitoid complex(s) at ca 550 Ma followed by (2) intrusi on at higher levels of neosome formed during progressive deformation a nd metamorphism of the then crystallized plutonic complexes, and then (3) the uplift of the Leeuwin block. The tectonic fingerprint of the L eeuwin block could be a major factor in further refining Gondwanaland matching if corresponding tectonic fingerprints were to be recognized in coeval parts of the previously contiguous Antarctic and Indian segm ents.