Jökull - 01.01.2017, Blaðsíða 23

Svavarsdóttir et al.
Figure 1. The Bárðarbunga volcanic system with its subglacial central volcano and its extensive fissure swarm
(strippled outline). The Veiðivötn fissure swarm extends to the southwest of the Bárðarbunga central volcano.
Box 1 denotes the location of Bárðardalur valley and box 2 the Þjórsárhraun lava. Map from Larsen and Guð-
mundsson (2016). – Kort af eldstöðvakerfi Bárðarbungu sem sýnir sprungusveim (brotalína) og megineldstöð
kerfisins, ásamt hraunum sem eru talin tengjast kerfinu og runnið hafa til strandar norðanlands og sunnan.
Hraun sem runnið hafa eftir landnám eru í ljósari lit.
Jakobsson (1979) used major and minor elements
to assign lava units to their source, and this method
has been widely adopted to trace the origin of tephra
layers in Iceland (e.g., Larsen and Eiríksson, 2008).
When adopting this "fingerprint" method, it is impor-
tant to keep in mind that crustal processes affecting
the melt after it has left its source may strongly mod-
ify its primary chemical characteristics, adding further
complexities to inherent heterogeneity of the erupted
magma (e.g., Maclennan et al., 2003; Shorttle et al.,
2013). However, radiogenic isotopic tracers should,
in theory, not be modified during transport of a melt
from its source to the surface, particularly when con-
sidering long-lived isotopes with half-lives exceeding
the age of the Icelandic crust (e.g., Sr, Nd, Hf, and Pb).
This is particularly true when magmas do not need to
bypass a seawater-altered crust in which radiogenic
Sr enrichment can occur. Thus, measured isotope
18 JÖKULL No. 67, 2017