Jökull - 01.01.2019, Page 90

Eyjafjallajökull ankaramites, South Iceland
Brattaskjól
Hvammsmúli
Matthews et al. 2016
0
10
20
30
40
50
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70
80
90
30 40 50 60 70 80 90 100
C
r#
s
p
l
Mg#spl
0.00
0.05
0.10
0.15
0.20
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0.30
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30 40 50 60 70 80 90 100
F
e
/F
e
3
+
to
t
Mg#spl
0.01
0.1
1
10
0 10 20 30 40 50
T
iO
2
(w
t%
)
Al O (wt%)2 3
a b c
LIP
OIB
MORB
Figure 3. a) Cr number (Cr#spl = cation fraction 100Cr/(Cr+Al)) against Mg number (Mg#spl = cation fraction
100Mg/(Mg+Fe2+)) in spinel. 2σ analytical error is smaller or equal to the symbol size. b) The ratio of ferric iron to
total iron (Fe3+/Fetot) vs. Mg# in spinel. The amount of Fe3+ is calculated based on stoichiometry. c) Spinel TiO2 vs.
Al2O3 diagram; spinel discrimination fields are after Kamenetsky (2001). Spinel compositions from the Northern Rift
Zone of Iceland (Matthews et al., 2016) are shown for comparison (black crosses). – a) Cr-tala (Cr#spl = katjónahlutfallið
100Cr/(Cr+Al)) sem fall af Mg-tölu (Mg#spl = katjónahlutfallið 100Mg/(Mg+Fe2+2)) spínils. 2σ óvissa í efnagreiningum
er minni eða jafnstór og sýnatáknin. b) Hlutfall ferríjónar af heildarmagni járns (Fe3+/Fetot) á móti Mg# spínils. Magn
Fe3+ er reiknað út frá efnaformúlu spínils. c) Styrkur TiO2 á móti styrk Al2O3 í spínli; aðgreiningarsvæði fyrir spínil eru
frá Kamenetsky (2001). Efnasamsetningar spínils frá Norðurgosbelti (Matthews o.fl., 2016) eru sýndar til samanburðar
(svartir krossar).
Table 1. Representative melt inclusion (MI) compositions* (in wt%) from Brattaskjól and Hvammsmúli olivine
macrocrysts. All melt inclusions from Brattaskjól reported here were homogenized at 1200◦C. – Dæmigerðar
efnasamsetningar (% af massa) bráðarinnlyksna (MI) í ólivíndílum frá Brattaskjóli og Hvammsmúla. Allar bráð-
arinnlyksur frá Brattaskjóli sem rætt er um í greininni voru gerðar einsleitar með því að bræða þær við 1200◦C.
SiO2 TiO2 Al2O3 FeOtot MnO MgO CaO Na2O K2O P2O5 SO3 Cl Total PEC%a Mg#b Foc Typed
Brattaskjól
Ol14_mi1_2 46.39 2.54 15.11 11.21 0.16 8.82 12.27 2.36 0.44 0.30 0.32 0.03 99.9 – 60.9 80.9 alk. bas.
Ol17_mi1 46.99 2.31 16.11 9.75 0.16 7.99 13.28 2.24 0.53 0.34 0.27 0.03 100.0 – 61.9 82.4 alk. bas.
Ol10_mi1 45.60 2.69 15.71 10.27 0.17 8.91 13.31 2.23 0.43 0.36 0.30 0.02 100.0 – 63.2 82.9 alk. bas.
Ol7_mi1 46.33 2.32 15.55 9.72 0.16 9.09 12.91 2.25 0.53 0.45 0.29 0.04 99.6 – 65.0 83.0 alk. bas.
Ol25_mi1_2 48.02 2.07 15.25 8.27 0.12 8.87 14.19 2.29 0.44 0.28 0.25 0.02 100.0 – 68.0 86.0 alk. bas.
Ol33_mi1 47.81 2.27 16.06 7.84 0.12 8.60 14.21 2.46 0.40 0.21 0.20 0.03 100.2 – 68.5 87.0 alk. bas.
Ol11_mi1 49.31 2.87 13.46 7.60 0.11 9.06 13.60 2.34 0.64 0.58 0.21 0.03 99.8 – 70.2 87.9 ol. tho.
Ol1_mi1_2 48.58 3.56 12.97 7.29 0.15 9.96 15.79 0.89 0.18 0.24 0.03 0.00 99.6 – 73.0 88.6 tho.
Ol9_mi1 47.27 2.44 16.29 9.56 0.17 6.25 13.28 2.68 0.53 0.32 – – 98.8 6.7 56.4 81.6 alk. bas.
Ol9_mi2_2 46.86 2.54 16.56 9.57 0.11 6.17 13.44 2.73 0.49 0.27 – – 98.7 9.5 56.1 81.6 alk. bas.
Ol23_mi2_2 51.11 2.65 15.10 6.27 0.13 6.98 14.62 2.14 0.28 0.14 – – 99.4 3.9 68.8 87.9 tho.
Ol29_mi1 53.91 2.31 14.69 5.86 0.15 7.46 12.88 1.76 0.38 0.06 – – 99.4 -0.6 71.6 88.7 bas. and.
Hvammsmúli
Ol3_mi1_1160_3 49.48 2.40 14.37 6.25 0.11 7.63 11.87 3.62 0.96 1.64 0.10 0.06 98.5 not calc. 70.7 79.6 alk. bas.
Ol1_mi1_1200_1 47.94 3.35 13.71 6.18 0.09 8.38 13.86 3.26 0.76 0.52 0.07 0.04 98.2 not calc. 72.9 85.6 alk. bas.
Compositions in wt%. aPEC% = percentage of post-entrapment olivine crystallization in MI
bMg# = 100Mg/(Mg+0.9Fetot) cFo = forsterite content (100Mg/(Mg+Fe2+)) in host olivine
dMI type according to normative mineralogy
JÖKULL No. 69, 2019 89