Geochemistry of the Cenozoic Volcanic Rocks of Ross Island and Vicinity, Antarctica

Abstract

The Cenozoic volcanic rocks of Ross Island and vicinity, Antarctica, are surface flows, tuffs, breccias, and small intrusives. The prominent rock is basanitoid. Alkali-basalt magma reached the surface over an appreciable length of time and was differentiated to produce a rock series: basanitoid-. trachybasalt-, phonolite. The alkalic, silica-undersaturated rocks are part of a larger petrologic province composed of volcanic centers in a belt nearly 2,000 km long roughly parallel to the Transantarctic Mountains. Two trends of magmatic differentiation are apparent. At depth the fractional crystallization of olivine, clinopyroxene, and opaque oxide minerals, all of which are abundant as phenocrysts in the basanitoid flows, produced trachybasalt magma. At crustal levels, fractional crystallization of clinopyroxene, apatite, opaque oxides, kaersutite, plagioclase, and anorthoclase developed the phonolitic rocks. Alkali enrichment is marked, and the end-member phonolites contain 11% NazO, 5.6% K20, and 57% SiO2. The basanitoids contain relatively large amounts of Ba (~ 400 ppm), Sr (~ 1,000 ppm), and Rb (~ 30 ppm). The concentrations of these and other trace elements in the various rock types support the model of small degrees of partial melting of peridotitic mantle for the derivation of the basanitoid magma, and of magmatic differentiation for the subsequent development of the rock series.

Mineralogy and Geochemistry of Alkali Basalts from Maud Rise|Weddell Sea|Antarctica

“…Alkali basalts found in the Antarctic region include Kerguelen Island (Watkins et al, 1974), Kerguelen Plateau (Storey et al, 1988), the Antarctic Peninsula (Hole, 1988;Smellie, 1987); Ross Island, Antarctica, a part of the volcanic belt that parallels the Transantarctic Mountains (Goldich et al, 1975;Sun and Hanson, 1975), Bouvetoya Island (Imsland et al, 1977) and P-type basalts from several localities at and near the Bouvet triple junction (LeRoex et al, 1983). In addition, preliminary work suggests that some rocks drilled at northeast Georgia Rise during Leg 114 are probably transitional between alkali basalts and tholeiites (M. Perfit, pers.…”

Petrology of the Bull-of-the-Woods intrusive complex

“…oxides, However, Frey et al (1978) state light rare earth element abundances (La, Ce, Sm) that vary by less than a factor of two are 27 consistent with a comagmatic model. Goldrich et al· (1975) (Tables II to VIII (Table II) appear to be comagmatic with each other. Immobile Sc and…”

“…In this study, Andesites display a characteristically limited variability in trace element abundances (Gunn, 1974 effects, however, are minor in andesites, "due to the common coprecipitation of several c.rystal phases" (ibid). Where differentiation occurs, Na, La, Rb, and Ba will increase in concentration, while Fe, Co, Sc, and Cr will decrease (Goldrich et al, 1975).…”

Petrology, geochemistry and age of basanitoids dredged from the Bering Sea continental margin west of Navarin Basin

“…K2O vs. Rb plot shows the basanitoids from the western continental margin on the same general trend as Samoan (S) and Antarctic (A) basanites, however large scatter or multiple trends are observed for the Pribilof Islands. Data for Samoa from Hawkins and Natland (1975) for Ross Island from Goldich et al (1975) and Sun and Hanson (1975). K/Rb ratios of approximately 350, 450 and 750 are shown for reference.…”