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Victoria University Antarctic Research Expedition Science and Logistics Reports 1980-81: VUWAE 25


The area between the Miers and Salmon Valleys has been remapped in greater detail than before and several corrections have been made to the small scale maps of Blank et al. (1963). A simplification of the stratigraphy of the metasedimentary rocks will be proposed and areas mapped before as undifferentiated granitic intrusions have been mapped as different intrusive events. The initial distinction between different granitic bodies has only been made on field relations and hand specimen inspection at this stage, but this is presently being extended to petrographic and geochemical classification. The area has been extensively sampled and it is hoped that this may provide a basis for a coherent nomenclature of some of the granitic rocks in the dry valley region which is at present somewhat confused. Samples were collected from type areas of Granites in the Wright Valley and these will be used for comparison.

At least 5 distinct granite bodies intrude the area and these can be arranged in a time sequence by field relationships between the different granites and the extent of deformation suffered by the different bodies. Four of these granites are shown to be mutually intrusive in the north wall of the Miers Valley (Plate IVA).

Preliminary thin section petrography has established that most of the 'granites' in the area are granodiorites and diorites rather than true granites with different types often having distinctive mineral assemblages, with the presence or absence of hornblende being one of the most important distinguishing features.

There is little evidence of the mineralogy of the granites being affected by the high grade metamorphic events known to have occurred in the area.

Blank et al. (1963) reported that the metasedimentary rocks of the area had undergone regional metamorphism to amphibolite facies. Preliminary thin section petrography has confirmed this but in the section chosen no minerals suitable for geobarometry or geothermometry were found. The meta-sediments intruded by the later granites show little sign of assimilation and retrogressive metamorphism is uncommon.