Jökull - 01.01.2017, Side 43

Svavarsdóttir et al.
Figure 11. 208Pb/204Pb vs. 206Pb/204Pb isotopic variation of published data for (a) Þeistareykir along with data
for eruptive units found between the Krafla and Þeistareykir volcanic systems (Gæsafjöll group). (b) Krafla
along with data for eruptive units located between the Krafla and Þeistareykir volcanic systems (Gæsafjöll
group). (c) Askja along with data for eruptive units situated in distal parts of the Askja fissure swarm
(Herðubreið group). (d) Bárðarbunga along with data for eruptive units situated between the Bárðarbunga
and Askja volcanic systems (Trölladyngja group). Note that different symbols in the figure denote different
age groups of the volcanic units sampled: square for historical volcanic units, triangle for pre-historic post-
glacial units, and diamond for pre-Holocene units. – 208Pb/204Pb - 206Pb/204Pb breytileiki birtra gagna frá:
(a) Þeistareykjum auk gagna fyrir goseiningar sem staðsettar eru milli Kröflu og Þeistareykja. (b) Kröflu auk
gagna fyrir goseiningar sem staðsettar eru milli Kröflu og Þeistareykja. (c) Öskju auk gagna fyrir goseiningar
sem staðsettar eru utan megineldstöðvarinnar. (d) Bárðarbungu auk gagna fyrir goseiningar sem staðsettar
eru í nágrenni Trölladyngju.
NRZ. For this purpose, it is also important to obtain
data from well characterized lava units only as, for ex-
ample, clear spatial variations in isotopic ratios are ev-
ident along the NRZ (e.g., Hémond et al., 1993; Chau-
vel and Hémond, 2000; Stracke et al., 2003; Thirlwall
et al., 2004; Kokfelt et al., 2006; Peate et al., 2010;
Sims et al., 2013). However, very limited petrochem-
ical data have been published from some areas along
the NRZ, for example from the Fremri Námar vol-
canic system and the Hrúthálsar complex. Detailed
petrochemical studies of these regions are therefore
highly important for future studies.
Temporal variations in major and trace elements
of selected lava fields in Iceland have also been re-
ported. For example, primitive (high-MgO) com-
positions are generally more abundant among early
38 JÖKULL No. 67, 2017