Rit (Vísindafélag Íslendinga) - 01.06.1967, Qupperneq 96

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total variation in field intensity from the bottom of the nega-
tive anomaly to the top of the positive anomaly is ahout
3000 gammas (1 gamma = 10“5 oersteds). This anomaly is
linear all the way across the survey area, a distance of 430
km. On hoth sides of the axial anomaly there is a number
of smaller anomalies, parallel to the ridge, which can be
traced all the way across the survey area. These anomalies
show a remarkahle degree of symmetry about the axial ano-
maly.
According to Heirtzler et al. (1966) the central anomaly
could be caused hy a block 20 km wide and 6 km thick with
magnetization of 0.008 emu in direction of the earth’s field
if it is surrounded by nonmagnetic material. If the block is
embedded in material with equally strong magnetization as
the block itself but opposite polarity a magnetization of 0.004
emu will produce the same anomaly. Most likely the ma-
terial causing the magnetic anomalies has similar composi-
tion as basalt. Judging from the natural magnetization of
surface basalts it seems unlikely that the hulk magnetization
of the material responsible for the magnetic anomalies could
be as high as 0.008 emu, whereas 0.004 emu might be a rea-
sonable guess. Actually the hlock will not be surrounded hy
nonmagnetic material. If this material is magnetized in the
same direction as the block it will reduce the anomaly pro-
duced hy the block alone. Therefore it seems likely that hoth
normal and reversed magnetizations are involved in produc-
ing the magnetic anomalies accompanying oceanic ridges.
For the same reason the magnetic material causing the cen-
tral anomaly should not be less than several kilometers
thick. On the other hand Heirtzler et al. (1966) come to the
conclusion that the Curie isotherm should be at a depth of
6 km under the ridge thus excluding magnetized material
at a greater depth.
Another extensive aeromagnetic survey was carried out in
the summer of 1965 by a group from Dominion Observatory
in Canada under direction of Dr. Poul H. Serson. The sur-