Mineralogy and Geochemistry of a Basanite to Phonolite Sequence at Hut Point Peninsula, Antarctica, based on Core from Dry Valley Drilling Project Drillholes 1, 2 and 3

• Published in: Journal of Petrology
• Main Author: KYLE, PHILIP R.
• Format: Text
• Language: English
• Published: Oxford University Press 1981
• Subjects: Articles; Ross Island; Hut Point; Hut Point Peninsula; Antarc*; Antarctica
• Online Access: http://petrology.oxfordjournals.org/cgi/content/short/22/4/451; https://doi.org/10.1093/petrology/22.4.451

The Dry Valley Drilling Project (DVDP) cored three holes (DVDP 1, 2 and 3) at Hut Point Peninsula (HPP) on Ross Island, Antarctica. DVDP 1 reached 201 m and penetrated 40 stratigraphic units, mainly basanite and Ne-hawaiite lava flows and associated pyroclastic rocks. DVDP 2 and 3 are nearly identical. DVDP 3 reached 381 m and penetrated 15 stratigraphic units. The lower unit is a 214 m thick basanite hyaloclastite, this is overlain by flows and pyroclastic rocks of basanite, Ne-hawaiite, and then alternating Ne-mugearite and Ne-benmoreite flows. Phonolite stratigraphically overlies the drill site. Primary olivine (Fo 88 -Fo 74 ) is confined to the basanites, although xenocrysts occur in other rock types. Calcium-rich clinopyroxene is ubiquitous but shows little variation in terms of Ca, Mg, Fe2+. Kaersutite is common in all lavas except the basanites and shows very little compositional variation. It is believed to have crystallized at temperatures below 1100 °C and at pressures between 1·5 and 10 kb. Rhönite, a titanosilicate is a common groundmass phase in some basanite lavas. Oxide minerals show a wide range of compositions; spinel and chromian spinel occur as inclusions in olivine in the basanites. Titano-magnetite occurs in most samples examined. Labradorite is the predominant feldspar in the basanite, with andesine and oligoclase important in all other rock types. DVDP and HPP samples show a well-defined sequence of basanite-Ne-hawaiite-Ne-mugearite-Ne-benmoreite-phonolite, termed the DVDP lava lineage. Differentiation of the lineage has been modeled using major element least squares mass balance models. Over 75 per cent of the evolution from basanite to phonolite occurs in the initial step from basanite to Ne-hawaiite, which represents a 43 per cent residual. The phonolite is only a 25 per cent residual from a basanite parent; thus even though Ne-mugearite and Ne-benmoreite are common, they represent only minor steps in the differentiation sequence. The mass balance models indicate that olivine, ...