Greinar (Vísindafélag Íslendinga) - 01.01.1977, Page 93

91
Fig. 15. A section through the smoothed topographic mound of Iceland and
the corresponding isostatic root. Further explanation in the main text.
mineralogical considerations be less basic than primary basal-
tic magma (54).
What we know, is that differentiation takes place in Iceland
during incubation time in a magma reservoir (Hekla), that
it also takes place in “inferred vertical reservoirs” during “in-
ferred incubation time” and that the maximum differentiation
increases regularly towards the top of a smoothed Iceland
mound that is in isostatic equilibrium and, by any reasonable
assumption must have a root, so that the real crustal section
through the top of the mound is similar to that of Fig. 15.
We then infer from this that “acidic” material is most likely
found in the lowest part of the Icelandic crust, as we can not
now see that gravitative differentiation would easily lead to
Fig. 12.
We seem then to have obtained a very important insight
into volcanic chemistry in Iceland in particular.1) In considera-
1) As a by-product, we see that it is easy to interpret geochemical data
without postulating a “plume” from the Low velocity layer, the chemical
composition of the latter also being postulated.