14.1 MCMURDO VOLCANIC GROUP

Ryan JG, Kyle PR (2000) Lithium isotope systematics of McMurdo volcanic group lavas, and other intraplate sites. EOS Trans, Am Geophys Union 81 E1371... 

Kyle P. R., Wright A., and Kirsch 1. (1987) Ultramafic xenoliths in the late Cenozoic McMurdo volcanic group, western Ross Sea embayment, Antarctica. In Mantle Xenoliths (ed. P. H. Nixon). Wiley, New York, pp. 287-294. 

McMurdo Volcanic Group Ferrar and Kirkpatrick groups Beacon Supergroup Kukri Unconformity... 

The Cenozoic volcanic rocks of the Transantarctic Mountains form the McMurdo Volcanic Group which is subdivided on the basis of geographic location into four provinces (LeMasurier and Thomson 1990) ... 

The ages of the Cenozoic volcanic rocks of the McMurdo Volcanic Group were determined by Armstrong (1978), Fleck et al. (1972), Forbes et al. (1974), Wright-Grassham (1987), and others by the whole-rock K-Ar method. Under ideal circumstances, these dates indicate the crystallization ages of late Cenozoic volcanic rocks that cooled rapidly after they were erupted on land, provided they were not hydro-thermally altered and provided that all " Ar was out-gassed from the lava at the time eruption. 

Fig. 16.6 (a) The Sr/ Sr ratios of Cenozoic alkali-rich lavas of the McMurdo Volcanic Group in the Erebus volcanic province have a unimodal distribution between 0.7030 and 0.7035. One sample of trachyte has an Sr/ Sr ratio of 0.70501 and a... 

In conclusion, Berg (1991) pointed out that ultra-mafic inclusions that contain orthopyroxene resemble the two-pyroxene granulite inclusions and, in some cases, are interbedded with them in the largest specimens. However, as noted before, the ultramafic inclusions are not genetically related to the Ferrar Dolerite or to the Cenzoic alkalic lavas of the McMurdo Volcanic Group (McGibbon 1991). 

The Cenozoic volcanic rocks of the Transantarctic Mountains are collectively referred to the McMurdo Volcanic Group. These rocks were erupted by volcanoes located in four volcanic provinces described in this chapter. The Erebus volcanic province includes Mt. Erebus, Mt. Terror, and Mt. Bird on Ross Island as well as Mt. Discovery and Mt. Morning on the mainland of southern Victoria Land. Volcanic rocks of Cenozoic age occur widely on the other off-shore islands as well as on Minna Bluff, the Brown Peninsula, the Royal Society Range, and the ice-free valleys. 

Kyle PR (1986) Mineral chemistry of late Cenozoic McMurdo Volcanic Group from the Pleiades, northern Victoria Land. Antarctic Research Series, vol. 46. American Geophysical Union, Washington, DC, pp 305-337 Kyle PR (1990a) Erebus volcanic province Summary. In LeMasuiier WE, Thomson JW (eds) Volcanoes of the Antarctic Plate and Southern Ocean. Antarctic Research Series, vol. 48. American Geophysical Union, Washington, DC, pp 81-88... 

Kyle PR (ed) (1995) Volcanological and environmental studies of Mt. Erebus, Antarctica. Antarctic Research Series, vol. 66. American Geophysical Union, Washington, DC Kyle PR, Cole JW (1974) Structural control of volcanism in the McMurdo Volcanic Group, Antarctica. Bull Volcanologique 38(1) 16-25... 

Fig. 19.20 The Cenozoic volcanic rocks of the McMurdo Volcanic Group in the Wright, Taylor, and Ferrar valleys of southern Victoria Land were erupted between 5.0 and 1.5 Ma (Pliocene), whereas the eruptions in the ice-free valleys north of the Koettlitz Glacier (Fig. 19.19) started at 3.0 Ma and lasted well into the Pleistocene. The eruptions in both areas were subaerial rather than subglacial and occurred after the Transantarctic Mountains of southern Victoria Land had been overridden by the East Antarctic ice sheet (Data from Armstrong 1968 Fleck et al. 1972 Barrett et al. 1992 Wilch et al. 1993b HaU et al. 1993)...

The Peleus till covers the floor of east-central Wright Valley up to an elevation of about 1,150 tn (Prentice 1982 Hall et al. 1993), but it does not form moraines or other kinds of glacial landforms. It consists of a pale yellow to yellowish brown diamicton with a silty or sandy matrix containing clasts of dolerite, granitoids, and metasedimentary rocks, as well as of orthoquartzite and porphyritic dike rocks, all of which occur within the Wright Valley. However, the Peleus till does not contain clasts of late Cenozoic basalt of the McMurdo Volcanic Group. Evidently the Peleus till was deposited before the start of volcanic eruptions in the area. 

Armstrong RL (1978) K-Ar dating Late Cenozoic McMurdo Volcanic Group and dry valley glacial history, Victoria Land, Antarctica. New Zealand J Geol Geophys 21(6) 685-698... 

Kyle PR (1981) Glacitil history of the McMurdo Sound area as indicated by the distribution and nature of McMurdo Volcanic Group rocks. In McGinnis LD (ed) Diy Valley Drilling Project. Antmctic Research Series, vol. 33. American Geophysical Union, Washington, DC, pp 403 12 LaveUe M (1998) Strontium-isotope stratigraphy of the CRP-1 drill hole, Ross Sea, Antarctica Terra Antartica 5(3) 691-696... 

These statements by Wilson remind us that the Transantarctic Mountains contain not only the silica-saturated basalt flows and dolerite sills of the Middle Jurassic Ferrar Group, but also late Tertiary alkali-rich volcanic rocks of the McMurdo Volcanics. Behrendt (1991a, b) combined the presence of these volcanic rocks with geophysical data to define the Cenozoic West Antarctic Rift system. 

Hart SR, Kyle PR (1993) The geochemistry of McMurdo Group volcanic rocks. Antarctic J US 28 14-16 Hoefs J (1997) Stable isotope geochemistry, 4th edn. Springer, Heidelberg, Germany... 

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