Jökull - 01.12.1977, Page 47

*
ll
8
96
u
14
2
06
0)
u_
*
S'*
2
Fig. 26. Vaiiation diagram of Hg in the section
at Ofærugil. Samples connected with lines are
all from the greyish-pink purnice.
Mynd 26. Mynd er sýnir mismunandi efna-
S(imsetningu sýna úr i Ófœrugili. Sýni sam-
tengd með strikum eru úr grábleika vikrinum.
according to Sigvaldason, is the trace element
distribution in glass from the three lowermost
nnits of H3 (one sample from each). A maxi-
tnum of Zr was found in the glass from the al-
most aphyric (0.1% crystals) greyish-pink pumice
as compared to glass frorn the relatively pheno-
cryst-rich (4.7% crystals) white pumice and glass
from the more basic brown pumice.
We have no additional data on the trace ele-
■nents, l)ut if zircon or a Zr-ricli crystal phase
from the most silicic liquid was resorbed at the
boundary between it and a hotter, more basic
liquid (i.e. the greyish-pink pumice), a maximum
°f Zr is to be expected in the glass of the latter.
The Zr concentration should be highest at or
near the boundary and then fall off due to
further mixing with the basaltic andesitic end-
rnember.
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JÖKULL 27. ÁR 45