Geology of the Wisconsin Range batholith, Transantarctic Mountains

Abstract

Abstract The Wisconsin Range consists mainly of a composite batholith of Late Precambrian and Early Paleozoic age. It is one of several batholiths that constitute the core of the Transantarctic Mountains. The batholithic rocks are flanked by the metamorphosed greywackes and argillites of the La Gorce Formation and the metavolcanic rocks of the Wyatt Formation that were deposited in the Ross geosyncline in Precambrian time. The metasedimentary and metavolcanic rocks were metamorphosed and partially reconstituted into granitic rocks during the Late Precambrian Mawson Orogeny. The resultant polygenetic batholithic complex ranges in composition from granite to quartz diorite, and has both foliated and massive facies. Some facies are characterised by abundant porphyroblasts of rapakivi feldspars. Tourmaline granite and porphyritic quartz monzonite make up other facies of the complex. The various facies have both gradational and intrusive relations with each other. Andesite dikes and plugs of hornblendite were intruded after consolidation of the batholith, probably in Early Paleozoic time. Aplitic quartz monzonite and pegmatites were intruded throughout the batholith in Early Ordovician time. This period of intrusion occurred during or after the Ross Orogeny. Foliation in the gneisses, and bedding and cleavage in the rocks of the La Gorce Formation, trend north-east, parallel to the axis of the Transantarctic Mountains. The present topography of the Wisconsin Range is controlled by block-type faults with total vertical displacement of more than half a mile.