Jökull - 01.12.1977, Page 15

Fig. 6. Weight percent TiOa (linear) vs. weight
percent P2Ob (logarithmic) in the analyses re-
ported in Tables II and III. Asterisks: micro-
probe analyses of glasses from the Bárdarbunga
core, Circles: whole-rock analyses of various
tephras and lavas. Note the clustering of the
asterisks, and the relatively greater scatter of the
circles.
Mynd 6. Þyngdarprósent titans (línulegar
kvarði) móti fosfór (lógarithmiskur kvarði) í efna-
greiningunum i 11. og III. töflu. Stjörnur eru
greiningar gerðar á gleri Bárðarbungulaganna
með örgreini (electron microprobe), hringir eru
greiningar á ýmsutn vel þekktum gjóskulögum
og hraunum. Takið eftir því, hvernig stjörnurn-
ar mynda þrjá hópa, en hringirnir dreifast.
1 Ti02 I i 1 I I 1 1 I l 1
♦ Table III O Table II * 0
- 1 ■fc. 0 0 0 0
• 1*1 **0 * O o •
* 1 0 -** p2o5 1 1 1 1 1 1 1 1 1 1
0-1 0-2 0-3 05 07 1* 2-
TABLE Ií.
Whole-rock analyses of samples from volcanoes potentially shedding tephras 011 Bárdarbunga
1 2 3 4 5 6 7 8 9 10 11 12
sío2 .... 50.31 61.80 50.75 49.73 49.80 49.61 50.05 47.30 47.60 49.97 56.06 49.70
ai2os ... 13.10 15.90 13.95 14.80 13.87 11.49 14.19 12.82 13.54 13.88 14.17 14.60
tío2 .... 2.98 0.95 2.88 2.51 2.83 2.94 1.49 4.20 4.31 2.65 1.47 1.97
FeoO:) . . . 1.93 1.84 1.78 3.10 1.84 4.66 1.27 1.50 1.42 1.16 3.37 3.05
FeO 13.68 6.75 12.12 11.53 12.38 11.33 11.55 13.56 13.06 12.22 10.27 9.97
MnO .... 0.23 0.15 0.23 0.15 0.16 0.26 0.31 0.22 0.28 0.23 0.36 0.25
MgO .... 4.88 1.53 4.13 4.92 4.92 5.55 7.20 4.56 4.88 5.90 1.41 4.90
CaO .... 8.87 5.44 10.14 9.55 9.75 9.66 11.18 10.00 9.25 10.25 5.41 10.35
NaoO . . . 2.86 3.82 2.90 2.86 3.17 2.45 2.30 2.90 2.88 2.74 4.20 2.23
KoO 0.53 1.66 0.44 0.52 0.55 0.33 0.17 0.86 0.80 0.44 1.48 0.35
PoO.-, .... 0.27 0.40 0.33 0.23 0.22 0.32 0.20 0.73 0.60 0.27 0.61 0.23
h2o .... 0.34 0.30 0.09 0.48 0.51 1.18 0.28 1.07 0.18 0.10 0.90 0.88
99.98 100.55 99.74 100.38 100.00 99.78 100.17 99.72 98.80 99.82 99.70 98.48
1. Askja 1901 (Thorarinsson ir Sigvaldason 1962)
2. Hekla 1947 (H 47 - 1Gb, Sigualdason 1974)
3. Grímsvötn 1934. Coll. Gudmundur Einarsson. New analysis, Sci. Inst. SAL 51)
4. Grímsvötn 1934. Collected in l’apey. (Barth 1937)
5. Grímsvötn 1922. Collected in Papey. (Barth 1937)
6. Þórdarhyrna 1903. Coll. 011 ship off Langanes (M. L. Mouritzen & A. Noe-Nygaard 1950)
7. Tröllahraun 1862—64 (Thorarinsson ir Sigvaldason 1972)
8. Katla 1918. Collected at Kirkjubæjarklaustur. New analysis, Sci. Inst. SAL 49
9. Katla 1755. Collected at Hólmsárbrú. New analysis, Sci. Inst. SAL 46
10. Laki 1783. New analysis. Sci. Inst. SAL 9
11. Öræfajökull 1727 (Thorarinsson 1958)
12. Layer “a” (Thorarinsson 1958; probably Kverkfjöll 1477. New analysis. Sci. Inst. SAL 53)
JÖKULL27. ÁR 13