Erebus Volcanic Province

We begin this chapter with descriptions of the lava flows that were erapted by the volcanoes of the Erebus volcanic province because they are accessible from McMurdo Station and Scott Base on Ross Island, because Mt. Erebus in Fig. 16.1 is the only active volcano in all of Antarctica, and because the volcanoes on Ross Island were discovered in January 1841 by James C. Ross and R.M. Crozier who named Mt. Erebus and Mt. Terror after their small wooden sailing ships. Even at that time, Mt. Erebus was active and has remained so to the present (Section 1.1). The first description of the volcanic activity on the summit of Mt. Erebus was provided by Ross (1847, p. 216, 220-221) on January 28,1841  

Faure and T.M. Mensing, The Transantarctic Mountains Rocks, Ice, Meteorites and Water, DOI 10.1007/978-90-481-9390-5 16, Springer Sdence+Busdness Media B.V. 2010 

At 4 p.m. Mount Erebus was observed to emit smoke and flame in unusual quantities... The bright red flame that flUed the mouth of the crater was clearly perceptible and some of the officers believed they could see streams of lava pouring down its side. 

The largest exposures of alkali-rich volcanic rocks in the Erebus volcanic province occur on Ross Island and in the Discovery subprovince (i.e., Mt. Discovery, Mt. Morning, Minna Bluff, and the Brown Peninsula in Fig, 16.1). The principal volcanoes on Ross Island 

These early reports were followed by investigations that were published after the IGY (1957-1958) Forbes (1963), Beck (1965), Cole and Ewart (1968), and Cole et al. (1971). Recent summaries of the geology, chemical composition, and isotope geochemistry of the Cenozoic volcanic rocks in the Erebus volcanic province are contained in b x ks edited by McGinnis (1981), LeMasurier and Thomson (1990), and Kyle (1995). 

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The volcanic rocks of the Erebus volcanic province were described by Treves (1967,1971) and by Goldich et al. (1975). The principal rock types recognized by them were Basanitoid, trachybasalt, anorthoclase pho-nolite, mafic phonolite, and trachyte. Although the nomenclature has changed, the rock descriptions by Treves (1967) and Goldich et al. (1975) still convey useful information. 

Mafic phonolite occurs in the form of small plugs and flows throughout Ross Island and elsewhere within the Erebus volcanic province. For examples. Post Office Hill at Cape Crozier and Observation Hill at McMurdo Station are composed of this rock type. Their chemical compositions are quite variable. Normative nepheline can be as high as 30%. Most samples contain more augite and kaersutite than the anorthoclase phonolites. 

The lavas of the Erebus volcanic province are alkali-rich and silica undersatured and are classified most effectively on the total alkali-silica diagram of Le Bas et al. (1986) in Fig. 16.3. However, Kyle et al. (1979) preferred the classification of Coombs and Wilkinson (1969) and identified most Cenozoic lavas in the Transantarctic Mountains as basanite, phonolite, or trachyte. Goldich et al. (1975, 1981), Sun and Hanson (1975,1976), Stuckless andEricksen (1976), Stuckless et al. (1981), and Weiblen et al. (1981) classified the lavas as trachybasalt and identified low-silica varieties as basanitoids. We will use the classification of Le Bas et al. (1986) which was also preferred by LeMasurier (1990). 

The chemical compositions of volcanic rocks of the Erebus volcanic province reported by Goldich et al. (1975) and Stuckless et al. (1981) range widely in Fig. 16.4 from low-silica basanites (Bn) to tephrites (Tp), phonotephrites (Ptp), tephriphonolites (Tpp), benmoreites (Bm), and phonolites (P). The silica concentrations of these rocks range from 41.3% (basanite. Brown Peninsula) to 58.1% (benmoreite. Cape Royds, Ross Island). The basanites in Fig. 16.4 have low... 

Fig. 16.3 The alkali-rich volcanic rocks of the Erebus volcanic province are classified on the total alkali-silica diagram of Le Bas et al. (1986). The rocks in this diagram can be arranged into three series with decreasing alkali content (1) Basanite (Bn), tephrite (Tp), phonotephrite (Ptp), tephriphonolite (Tpp), and phonolite (P) (2) Hawaiite (H), mugearite (M), benmoreite (Bm), and trachyte (T) (3) Basalt (B), basaltic andesite (Ba), andesite (A), and dacite (D). The boundary between the alkali-rich and subalkalic rocks defined by Macdonald and Katsura (1964) is shown as a dashed line (Adapted from LeMasurier (1990) and Wilson (1989))...

Fig. 16.4 The silica and total-alkali concentrations of Cenozoic lavas of the McMurdo Volcanics in the Erebus volcanic province range widely and are classifiable as basanite (Bn), tephrite (Tp), phonotephrite (Ftp), tephriphonolite (Tpp), phonolite (P), and benmoreite (Bm). All of the Cenozoic lavas in the diagram are alkali-rich and undersaturated with respect to silica. The alkali-rich Cenozoic lavas are associated with the West Antarctic rift system and occur not only in the Transantarctic Mountains but also in Marie Byrd Land and Ellsworth Land in West Antarctica (Data from Goldich et al. (1975) and Stuckless et al. (1981))...

In the Erebus volcanic province a thick sequence of basanite flows is overlain by more alkali-rich lavas (i.e., tephrites, phonotephrite, and tephriphonolites) which are capped by flows of phonolite. The petrogen-esis of the Cenozoic lavas of the Erebus volcanic province was also discussed by Stuckless et al. (1974), Goldich et al. (1975), Kurasawa (1975), Sun and Hanson (1975, 1976), Stuckless and Ericksen (1976), and Kyle and Rankin (1976). 

Table 16.1 Whole-rock K-Ar dates of lavas exposed at the surface in the Erebus volcanic province (Kyle 1990a)...

Information concerning the origin of the alkali-rich lavas of the Erebus volcanic province is derivable from the isotopic composition of strontium and the concentrations of rubidium and strontium. The first measurements of the Sr/ Sr ratios of the Cenozoic volcanic rocks in the Erebus province by Jones and Walker (1972) ranged from 0.7022 to 0.7048 with a mean of 0.70365 0.0024 (2o). These measurements demonstrated that the Cenozoic lavas are only moderately enriched in radiogenic Sr in marked contrast to the basalt flows and dolerite sills of the Eerrar Group. These results were later confirmed by Stuckless and Ericksen (1976) whose measured Sr/ Sr ratios in Figs. 16.6a, b, and c have a nnimodal distribution with a mean of 0.70332 0.00005 (2. ... 

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... 

The inclusions of crustal rocks in the lava flows of the Erebus volcanic province consist of lower-crustal granulites, upper-crustal basement rocks, and supra-crustal rocks. Berg (1991) described inclusions from 17 sites in the Erebus volcanic province, 7 of which are located in the Royal Society Range (Brandau Vent, Roaring Valley, Foster Crater, Ward Valley, The Bulwark, Lower and Upper Radian Glacier) and five on Ross Island (Cape Crozier, Cape Bame, and at three places on the Hut Point Peninsula). 

We cannot yet answer any of these questions except to assert in agreement with Kyle and Cole (1974) that the volcanic activity is a consequence of deep-seated tectonic processes which have caused patterns of crustal fractures that control the positions of the volcanoes in the Erebus volcanic province and elsewhere in Victoria Land, as well as in Marie Byrd Land (e.g., the Executive Committee Range). 

Fig. 16.16 The chemical compositions of volcanic rocks in DVDP-1 drilled at McMurdo Station on the Hut Point Peninsula range widely on the total alkali-silica diagram from basanite (Bn), to tephrite (Tp), to phonotephrite (Ptp), and to tephriphonolite (Tpp). Therefore, the rocks in this core (201.5 m) are almost as diversified as the McMurdo Volcanics in the entire Erebus volcanic province in Fig. 16.4. Samples of DVDP-2 and 3 are not shown but range just as widely as the rocks of DVDP-1 (Data from Kyle (1981a))...

The volcanic rocks of the Melbourne volcanic province are alkali-rich like those of the Erebus volcanic province although silica concentrations in the Melbourne province range more widely. The representative chemical analyses compiled by the authors of the book edited by LeMasurier and Thomson (1990)... 

Worner et al. (1989) reported chemical analyses for 92 samples of volcanic rocks from ten subdivisions of the Melbourne volcanic field. The analyses included major and trace elements and the resulting normative mineral compositions. Without classifying each one of these specimens, it is sufficient to record that their chemical compositions range widely just as they do in the Erebus volcanic province of southern Victoria Land (Fig. 16.4). Worner et al. (1989) also reported isotope... 

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... 

Mawson D (1950) Basaltic lavas of the Balleny Islands. ANARE report. Trans Roy Soc Australia 73 223-231 McGibbon FM (1991) Geochemistry and petrology of ultramafic xenoliths of the Erebus Volcanic Province. In Thomson MRA, Crame JA, Thomson JW (eds) Geological evolution of Antarctica. Cambridge University Press, Cambridge, UK, pp 317-322... 

The volcanoes of the Transantarctic Mountains occur between Cape Hallett in northern Victoria Land and Mount Early (87°04 S, 153°46 W), which is located only 300 km from the South Pole. The volcanic mountains and cinder cones in the Transantarctic Mountains define the McMurdo Volcanic Province which is subdivided into four regions (Kyle 1990). These volcanoes were active in Late Tertiary time starting less than 25 million years ago and continuing to the present as in the case of Mount Erebus. All of them have extruded silica-undersaturated and alkali-rich lavas in marked contrast to the Ferrar Dolerite and Kirkpatrick Basalts of Middle Jurassic age both of which consist largely of silica-saturated tholeiites. These two suites of volcanic rocks are products of quite different petrogenetic processes that nevertheless occurred at different times in the lithospheric mantle underlying the Transantarctic Mountains. The petrogenesis of these different suites of volcanic rocks is the subject of Chapter 12 (Kirkpatrick Basalt) and Chapter 13 (Ferrar Dolerite), and Chapter 16 (Cenozoic Volcanoes). 

Fig. 16.5 Whole-rock K-Ar dates of the McMurdo Volcanics of the Erebus, Hallett, and Melbourne volcanic provinces form an unbroken sequence from the Holocene (0 Ma) to the middle Miocene (10 Ma). The oldest date is 18.0 0.7 Ma (early Miocene) followed by 15.4 0.5, 13.8 0.2, and 13.2 0.4 Ma, all of which are in the Miocene. The pattern of variation of K-Ar dates indicates that the volcanic activity started during the early Miocene and continued without interruption to the present. Early-formed volcanic rocks are removed by erosion and may also be covered by younger flows which explains why the frequency of K/Ar dates decreases with the increasing age of the rocks (Data from Armstrong (1978), Forbes et al. (1974), and Fleck etal. (1972))...

The comparison of the flow stratigraphy of the Erebus volcaific province with the flow sequence on the Hawaiian islands raises questions about the petro-genesis of the volcanic rocks on Ross Island ... 

Armstrong (1978) reported two K-Ar dates of 5.49 0.12 Ma and 6.6 0.4 Ma (late Miocene) for rocks of the Hallett Peninsula. Three samples of basalt Irom Cape Hallett analyzed by Jones and Walker (1972) have Sr/ Sr ratios that range from 0.7037 to 0.7054 and are consistent with the Sr/ Sr ratios of the volcanic rocks of the Erebus and Melbourne volcanic provinces. 

Mt. Erebus, which still maintains a lava lake in a crater on its summit, is the only active volcano in Antarctica. Mt. Melbourne of the Melbourne volcanic province also continues geothermal activity on its summit, and volcanoes in The Pleiades have erupted in the recent past. All other volcanoes in the Transantarctic Mountains are extinct, although geothermal activity still occurs on a few volcanoes in Mary Byrd Land. 

Jones EM, Walker RL (1972) Geochemistry of the McMurdo Volcanics, Victoria Land, Part l Strontium isotope composition. Antarctic J US 7(5) 142-144 Jones LM, Faure G, Taylor KS, Corbatd CE (1983) The origin of salts on Mount Erebus and along the coast of Ross Island, Antarctica. Isot Geosci (Chem Geol) 1 56-64 Jordan H (1981) Tectonic observations in the HaUett volcanic province, Antarctica. Geologisches Jahrbuch, Reihe G,41 111-125... 

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