AndraditeMt Melbourne, Transantarctic Mts, Victoria Land, Eastern Antarctica, Antarctica
Latitude: 74°24'S
Longitude: 164°42'E
Active stratovolcano (trachyandesite to trachyte) on the margin of the Ross Sea.
Present activity is fumarolic.
Trachyte from the northern side of Mt Melbourne is garnet-bearing.
Garnet is intergrown with groundmass feldspar, producing an oikocrystic texture.
The formation of garnet result from localized gas-streaming in
the lava, reacting Ca-rich residual melt according to the reaction: augite + magnetite + glass + O2 = andradite (above 700 °C).
Ref. Goldschmidt Conference Abstracts 2005
Environmental Geochemistry/Mineralogy
http://www.the-conference.com/2005/gold2005/web_pdfs/G07.pdf [Link dead. Nov 2011]
Melbourne volcanic province stretches across the Transantarctic Mountains in northern Victoria Land and ranges in age from 0 to 7 m.y. A Central Suite of intermediate and trachytic lavas form stratovolcanoes, cones and plugs, while many small basanite outcrops constitute a Local Suite. Three lava lineages, resulting from differentiation, are recognised. 1) Lavas at The Pleiades and Mt Overlord consist of a mildly potassic trachyandesite-tristanite-K-trachyte-peralkaline K-trachyte lineage. Major, trace and rare earth element (REE) data suggest evolution by fractional crystallization of olivine, clinopyroxene, magnetite, apatite and feldspar. 2) A basanite-nepheline hawaiite-nepheline mugearite-nepheline benmoreite lineage, found at The Pleiades is believed to result from fractional crystallization of olivine, clinopyroxene, kaersutite, magnetite, apatite and feldspar. 3) An oversaturated (Q = 0 to 18%) strongly potassic quartz trachyandesite-quartz tristanite-quartz trachyte lineage occurs at only Mt Melbourne.
http://nzresearch.org.nz/index.php/record/viewSchema/43721/3
Mineral List
3 entries listed. 2 valid minerals.
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