Leka Steinsenter - in the middle of Norways Geological National Monument.
At Leka Steinsenter the rocks and minerals are displayed and explained.
The Leka ophiolite complex is an exotic fragment
of oceanic crustal material in this part of
Norway, where rocks of typical continental type
predominate. Thus, on the mainland
(Gutvik/Austra) there are mainly granitic
gneisses (old basement c. 1800 million years
old). These gneisses represent original granitic
rocks that were deformed and transformed due to
high pressure and temperature.
Sedimentary rocks that were deposited in
continental basins and on the continental shelf,
were folded and metamorphosed together with the
older basement rocks during the Caledonian
orogeny, when Baltica collided with Laurentia.
On Solsem°yene there are metamorphosed
sedimentary rocks of this kind. Some of these
rocks reached great enough depths that parts of
them started to melt. Now and then melts from
the mantle intruded these environments. The
melts solidified as plutonic rocks such as
granite, syenite and gabbro. In Horta, gabbro,
diorite, monzonite, syenite and granite occur
together with metamorphosed sedimentary rocks,
and at Sklinna there is granite. All these rocks
are older than c. 400-450 million years.
Similar to most places along the Norwegian
coast, there are few unconsolidated Quaternary
sediments at Leka. However, by the path up to
Solsemhula a very young serpentinite
conglomerate is exposed. It is poorly
consolidated and may be the youngest rock in
Norway, formed from local scree material after
the last glacial period (< c. 10 000 years old).
originally formed in the mantle are exposed on
the northern and western parts of Leka (Fig. 5).
They are most easily studied on the northern
side, where also the ancient Moho is exposed.
Four different rock types are common in the
mantle section. The most common is
which has a chocolate-coloured surface due to
weathering. Fresh surfaces are dark green.
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