Hydrothermal alteration of Lower Ordovician granitoids and Devonian Beacon Sandstone at Taylor Glacier,McMurdo Sound, Antarctica

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Abstract
In Kukri Hills, McMurdo Sound, Antarctica,Lower Ordovician Irizar Granite is altered along fractures where it is intruded by Jurassic Ferrar Dolerite.Hematite mineralisation associated with dolerite intrusion has caused reddening of K-feldspars in the granite; therefore, definition ofbasement granitoids according to feldspar colour is not as useful as thought previously. At Windy Gully, Lower Ordovician Larsen Granodiorite and granodioritic boulders in over- Iying Devonian Beacon Sandstone are altered pervasively. Sericite and andalusite are common alteration minerals in the granodiorite wh ich is enriched locally with hematite.An alteration temperature of 350°C is inferred.Textures in overlying Beacon Sandstone also indicate hydrothermal alteration. Convective hydrothermal circulation is thought to have been generated during intrusion of Ferrar Dolerite; as weil as reddening feldspars in Irizar Granite, it may have been responsible for resetting the detrital remanent magnetism of Beacon Sandstone so as to yield Jurassic pole positions.