Evolution of anorthoclase phonolite, Mt. Erebus, Antarctica

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6273553

Moore, J A; Kyle, P R

Over the last 1 m.y. Mt. Erebus (3794 m) has erupted mainly anorthoclase phonolite (AP) and lesser trachyte, kaersutite phonolite and intermediate differentiates. An active convecting AP lava lake, identical in composition to the older lavas, existed from 1972 until late 1984. Most of the rocks define a strongly undersaturated continuous sodic differentiation series, composed of basanite, Ne-hawaiite, Ne-mugearite, Ne-benmoreite and AP. The main phenocryst phases and their ranges are: olivine (Fo 81-43), clinopyroxene (Wo 50-44, En 42-24, Fs 11-30), opaque oxides (Usp 52-79) and feldspar. Major, trace and REE analyses exhibit smooth trends on variation diagrams. REE are strongly LREE enriched and increase from La/sub N/=220 in the basanites to 400 in AP. There are no significant Eu anomalies. Published isotopic data show derivation of the basanite parental magmas from a depleted (/sup 87/Sr//sup 86/Sr=0.703) heterogeneous mantle source similar to that for oceanic island basalts. Crustal contamination is insignificant except in the trachytes. Evolution of the Erebus lineage by fractional crystallization of the above phases plus apatite is supported by mass balance models. Differentiation probably occurred in larger, hotter and lower P/sub H20/ magma chambers compared to the basanite to kaersutite phonolite DVDP lineage (Kyle, 1981) of the neighboring Hut Point Peninsula. Mt. Erebus may mark the site of a major mantle upwelling.

• Research Organization: New Mexico Institute of Mining and Technology, Socorro (USA)
• OSTI ID: 6273553
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
580400 -- Geochemistry-- (-1989)
ANTARCTIC REGIONS
ANTARCTICA
CHEMICAL COMPOSITION
CHEMISTRY
ERUPTION
FELDSPARS
GEOCHEMISTRY
GEOLOGIC HISTORY
GEOLOGY
IGNEOUS ROCKS
ISOTOPE RATIO
LAVA
MAGMATISM
MINERALOGY
MINERALS
MOUNTAINS
PETROGENESIS
PETROLOGY
POLAR REGIONS
ROCKS
VOLCANIC ROCKS
VOLCANOES