EREBUS VOLCANO
Mt. Erebus is the only active volcano in
Antarctica. Samples from Erebus Volcano are difficult to acquire, but
here are two anorthoclase crystals weathered & eroded from lava exposed on
the summit cone.
The summit cone of Erebus has a nice anorthoclase
phenocryst gravel lag. Erebus erupts kenyte, the 2nd-rarest lava
type on Earth (see also Mt. Kenya volcano). Kenyte is a porphyritic
phonolite having anorthoclase feldspar phenocrysts and a glassy to
cryptocrystalline groundmass. The kenyte from which these anorthoclase
crystals are derived is highly vesiculated and glassy. There's a coating
of that material on the crystals shown below.
Erebus is a 1.3 million year old, polygenetic
stratovolcano in the West Antarctic Rift System. It has erupted basanite,
trachyte, tephriphonolite, and phonolite (kenyte) lavas during its history.
Locality:
Mt. Erebus Volcano, western Ross Island, Ross Sea,
Antarctica (77º 31’ 51” South, 167º 08’ 40” East).
Anorthoclase phenocrysts ((Na,K)AlSi3O8) having a
weathered, highly vesiculated, glassy phonolite coating (kenyte). These
are from a phenocryst lag deposit on the summit cone of Mt. Erebus
Volcano. The lava from which these crystals derive is Late Pleistocene or
Holocene in age (I'm not sure which).
Anorthoclase phenocryst derived from kenyte lava erupted from Mt. Erebus
Volcano, Antarctica.