Geology Reference
In-Depth Information
(1)
the East Eifel region occurring around Laacher See (30 km in diameter), which
covers an area of 400 km
2
with 70 eruptive centres, and
600 km
2
with 200 eruptive
centres, which lie about 25 km to the west of East Eifel region.
(2)
the West Eifel covering an area of about 500
-
SE direction from Bad
Bertrich at the Mosel River to Ormont near the Belgian border. The centres are
sometimes located 1 km apart and their number increases towards the centre of both
the
The latter is extended for a distance of 50 km along NW
-
fields.
In the West Eifel region, the total volume of ma
c magmas was less than
0.5 km
3
and may be less in the East Eifel region, but the volume of leucite-bearing
phonolitic to tephritic magma might have been more than 2 km
3
. According to them
the K/Ar and
14
C ages available suggest that the last eruption in East Eifel took
place 11,000 years B.P. and in the West Eifel 8,000 year B.P.
The K/Ar age determination of basanites and nephelinites lavas in the East Eifel
region suggests an age of 0.35
0.69 and 2.7 Ma in the West Eifel region.
According to Schminke and Duda volcanism in this area started in early Pleis-
tocene and culminated during Late Quaternary and as the last activity took place
10,000 years ago, the region can be considered as active. They consider that West
Eifel volcanism was associated with Maar Volcano. The craters are now water-
-
filled
surrounded by a rim of pyroclasts. There is enough evidence to suggest that the
volcanism in the centres was phreatomagmatic. They further suggested that
Strombolian/Hawaiian type of eruption mechanism was predominant in most cinder
cones and 10
flows. Plinian type of
eruption took place in Rieden, Wehr and Laacher See. Analyses of K-rich rocks
from Germany are summarized in Table
4.15
.
Basanites are dominant rock types in East Eifel, but nephelinites, melilite nep-
helinites and leucitites are common in West Eifel. In the latter area, basanitic lavas
are reported from Bad Bertrich-Wartgesberg. It is observed that K
2
O/Na
2
Ois
30 % of the centres in both
fields produced lava
-
≈
1in
West Eifel, but >1 in East Eifel. One interesting aspect of East Eifel volcanic
field is
the presence of many eruptive centres of intermediate and more evolved silica-
undersaturated alkalic rocks. There is however, paucity of any such rocks in the
West Eifel region. Peridotite nodules of large dimensions are common. Some of
the xenoliths in the volcanoes from West Eifel might suggest that the magmas in the
West Eifel region ascended relatively rapidly (Duda and Schminke 1978). Peri-
dotitic xenoliths are small and rare in East Eifel volcanoes. In some of the East Eifel
localities, they are found in such localities as Kempenich, Heider Kopf and
Sattelberg (Duda and Schminke 1978). According to Lloyd and Bailey (1969,
1975) amphibole and phologopite-bearing pyroxenite xenoliths in Eifel show evi-
dence of mantle metasomatism in the source rocks.
The volcanic centres of pumiceous tuffs originally covered an area, approximately
120 km long and 40 km wide area. Highly potassic rocks of the East Eifel region
occur as massive or vesicular lava
flow, associated with tuffs and scoria, and lapilli-
filled layers, often containing bombs with chilled margins. Leucitic rocks occur at
Steinraush (near Hill Shein), Erntsberg (near Hiterweiln), Hardt (near Mahren),
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