Jökull - 01.01.2019, Síða 86

Eyjafjallajökull ankaramites, South Iceland
-19.4°-19.6°-19.8°
63.65°
63.60°
63.55°
5 km
Road 1
Hvammsmúli
Brattaskjól
Fimmvörðuháls
2010 lava
50 km
SEVZ
1 mm
b
1 mm
c
a
Brattaskjól Hvammsmúli
Eyjafjallajökull
Figure 1. a) Map of the Eyjafjallajökull volcano with sampled locations and the 2010 Fimmvörðuháls lava flow field. In-
set shows map location (red rectangle) and the southern tip of the Eastern Volcanic Zone (SEVZ) in yellow. The active
plate boundary and the locus of the Iceland mantle plume (Wolfe et al., 1997) are marked with grey and black stippled
lines, respectively. b) Photomicrograph (in cross-polarized light) showing the texture of the Brattaskjól ankaramite sam-
ple. The large crystal on the left is olivine (3rd order blue interference colour) and the large crystal on the right (1st order
orange) is augite. c) Backscattered electron image of an augite crystal in a Hvammsmúli ankaramite sample. – a) Kort
af Eyjafjallajökulseldstöðinni sem sýnir sýnastaði og staðsetningu hraunsins sem myndaðist í gosi á Fimmvörðuhálsi árið
2010. Innfellda myndin sýnir staðsetningu kortsins (rauður ferhyrningur) og suðurenda eystra gosbeltisins (SEVZ) með
gulum lit. Virku flekamótin eru merkt með gráum strikalínum og útlínur möttulstróksins (Wolfe o.fl., 1997) með svörtum
strikalínum. b) Smásjárljósmynd (tvískautað ljós) sem sýnir textúr í ankaramítsýni frá Brattaskjóli. Stóri kristallinn til
vinstri er ólivín (blár bylgjuvíxllitur af þriðju röð) og stóri kristallinn hægra megin er ágít (gulur litur af fyrstu röð). c)
Endurkastsrafeindamynd af ágítkristal í ankaramítsýni frá Hvammsmúla.
these outcrops as ankaramites. These ankaramites
are highly porphyritic with abundant (∼30 vol%,
see Steinthórsson, 1964) olivine and clinopyroxene
macrocrysts in near equal amounts. Hvammsmúli
also has minor amounts of plagioclase macrocrysts,
not observed in Brattaskjól. As macrocrysts, we con-
sider crystals that are >0.3 mm in length and precede
groundmass minerals. Hvammsmúli has been dated to
587±31 ka (Wiese, 1992), but the exact age of Bratta-
skjól is unknown. An age of 500–720 ka for Bratta-
skjól is probable, however, judging from its strati-
graphic position (Loughlin, 1995) and normal mag-
netic polarity.
JÖKULL No. 69, 2019 85