GEOLOGICA CARPATHICA, 51, 6, BRATISLAVA, DECEMBER 2000
383397
ROZTOKY INTRUSIVE CENTRE IN THE ÈESKÉ STØEDOHOØÍ MTS.:
DIFFERENTIATION, EMPLACEMENT, DISTRIBUTION,
ORIENTATION AND AGE OF DYKE SERIES
JAROMÍR ULRYCH
1
and KADOSA BALOGH
2
1
Institute of Geology, Academy of Sciences of the Czech Republic, Rozvojová 135, CZ-165 02 Praha 6, Czech Republic
2
Institute of Nuclear Research, Hungarian Academy of Sciences, Bemtér 18/C, H-4026 Debrecen, Hungary
(Manuscript received June 16, 2000; accepted in revised form October 17, 2000)
Abstract: The Roztoky Intrusive Centre (RIC) is formed by a trachytic crater vent, hypabyssal intrusions, together
with more than 1000 almost radially arranged dykes and more rare cone sheets. Hypabyssal Weakly Alkaline Series of
essexite (3331 Ma)monzodiorite (3330 Ma)sodalite syenite (3028 Ma) and two coexisting weakly [camptonite
(31 Ma)/gauteite I?sodalite syenite porphyrygauteite II? (24 Ma)/trachyte?] and strongly alkaline dyke series
[camptonite (28 Ma)/monchiquite (26 Ma)phonolite/tinguaite (26 Ma)/nepheline syenite porphyry cone sheet (30
Ma)] were recognized. Four principal dyke groups were distinguished: I lamprophyres (58 %) dominated over II
semilamprophyres (28 %), minor III basaltic rocks (6 %) and IV felsic derivatives (9 %). Both radial steeply
dipping dykes of lamprophyres, semilamprophyres, basaltic and rare phonolitic rocks and flat dipping cone sheets of
trachyte and phonolite/nepheline syenite porphyry are present. Dykes of (semi)lamprophyres, and basaltic rocks show
similar preferred strikes of 90° and 0°; felsic derivatives of 330° and 0°. Majority (9198 %) of dykes (100 % of felsic
dykes) are present within a distance of 7 km from the Roztoky main centre. Joint and dyke patterns are controlled by
the regional paleostress field existing in the upper crust during magma ascent, by orientations of pre-existing fracture
sets in the region and by the superimposed local stress field exerted by the rising intrusion. For the interval of 3126
Ma in the RIC, the analysis of dyke geometries indicates the dominance of regional stress characterized by NS
tension (lamprophyres
≈
semilamprophyres > basaltic rocks > felsic derivatives).
Key words: N Bohemia, Èeské støedohoøí Mts., Cenozoic Roztoky Intrusive Centre, dyke rocks, differentiation,
orientations, age relations.
Introduction
The Ohøe (Eger) Rift (OR) is an integral part of the Cenozoic
Central European Rift System (Wimmenauer 1974). The
Èeské støedohoøí Mts. (CSM) represent the most significant
region of Cenozoic intraplate alkaline volcanism within the
OR (Hibsch 1926; Kopecký 1978; Ulrych 1998). The Roztoky
(Rongstock) Instrusive Centre (RIC) is the largest and the best
known polyphase volcanic centre of central type in the CSM
(Kopecký 1977, 1987; Ulrych et al. 1983; Ulrych 1998;
Jelínek et al. 1989; Mrlina 1998). The Atlantic Province of
Becke (1903) type area of alkaline volcanic rocks were
recognized in this very region.
Dykes associated with volcanic apparatus are found in sev-
eral places. They reach their highest concentration in dyke
swarms, which may be radial or parallel. Radial dykes invari-
ably converge on a volcanic centre or an igneous intrusion.
The principal problem in the development of central-type in-
trusions accompanied by systems of radial and concentric
dykes is the interpretation of differentiation, emplacement,
distribution, orientation, and age relations of individual rock
series. A regular system of radially orientated joints filled with
dykes is usually interpreted as resulting either from an active
role of basement structures or the active role of magmatic dia-
pirism of hypabyssal intrusions.
Kaiserstuhl represents the sole similar volcanic centre with
central hypabyssal intrusions in the Cenozoic Central Europe-
an Volcanic Province (CEVP). Despite the presence of ad-
vanced carbonatite differentiates Kaiserstuhl volcanism (Wim-
menauer 1974) reveals a more simple history of development.
Intrusions of central type were also developed in the Permi-
an Oslo Rift (Dons & Larsen 1978). Structural development of
the Alnö carbonatite intrusion (Sweden) was studied by Ecker-
mann (1966). Based on new structural and geophysical data,
Kresten (1980) reinterpreted individual dyke systems associat-
ed with the central carbonatite intrusions. The older concep-
tion of emanation of radial dyke swarms from a single distinct
centre and a simple diapiric genetic evolved into a conception
of emplacement-induced up-doming of the overlying country
rock accompanied by radial dykes with several centres and
two sets of cone sheets. The stress field created by the upward
movement of magma gave rise to the formation of two sets of
joints: tensional joints and cone sheets and shear joints. The
shear joints seems to contain no magmatic fill. Two preferred
strikes (NS and EW) are most typical for the radial dyke set.
Predisposition of the dyke system by fracturing pattern in the
host rock and major structural inhomogeneities of the area is
highly probable. The emplacement of radial dykes is associat-
ed with intrusive stage of the RIC history and up-doming of
the whole area. Pairs of mutually perpendicular joints evolved
in two independent systems. Joint formation is associated with
the mechanism of magmatic diapirism, however, the dyke em-
placement (sensu Kresten 1980) associated with intrusive
stage (radial dykes and cone sheets) and subsidence stage (ring
384 ULRYCH
and BALOGH
dykes and cone sheets). A depth of the roof of magma cham-
ber is supposed to be less than 2 km in the time of emplace-
ment.
Analogous intrusions of central type and associated dyke
swarms were also found in the late Cretaceous Serra de Mon-
chique, Mount Ormode Complexes (Rock 1982) and Algarve
Littoral Province, Portugal (Martins 1999). Igneous provinces
of the Monteregian Hills (Canada) and the near White Moun-
tains (USA) of Mesozoic age (Eby 1985, 1987) also reveal
features in differentiation development similar to those of the
RIC. Distribution, orientation and ages of mafic dyke systems
were presented by McHone (1978).
Geological setting
The CSM represents the largest erosional relict of the Ceno-
zoic volcanosedimentary complex (4216 Ma) within the OR.
About 60 vol. % are represented by massive volcanics only.
Volumetrically dominant relicts of superficial volcanics (45
vol. %) are formed primarily by primitive volcanic products of
an alkali basalt affinity. The following volcanostratigraphical
formations were recognized on the basis of volcanological and
geochemical investigations in the central CSM (Cajz et al.
1999): (i) the Lower Formation lavas and volcaniclastites
of basanitic character (3626 Ma), (ii) the Upper Formation
lavas and pyroclastics of trachybasaltic composition (3125
Ma) and the problematic (iii) Uppermost Formation flows
of basanite (24 Ma). The more differentiated shallow Intrusive
Complex (4316 Ma) is represented (Ulrych et al. 1997; Ul-
rych et al. 1999) by two coeval rock associations of the pre-
vailing weakly alkaline series WAS (basanite/trachybasalt
trachyte) and the minor strongly alkaline series SAS
(olivine-poor nephelinite/tephritephonolite). The boundary
drawn by Shrbený (1995) for Cenozoic volcanics of the Bohe-
mian Massif was used for the discrimination of trachytepho-
nolite in TAS diagram.
The RIC lies according to Kopecký (1978) at the intersec-
tion of hypothetical central faults of the OR (ENEWSW) and
the Labe Tectono-Volcanic Zone (WNWESE). A deeply
eroded central part of the RIC formed by an elliptic crater vent
(3 by 1.5 km) is filled with trachytic breccia with carbonate ce-
ment and presumed hidden carbonatite intrusion (Kopecký
1987). However, the extent of the polyphase RIC including an
olivine nephelinite intrusion at Dobkovice and mondhaldeite
breccia at Netìmice is probably even larger than 6 by 2.5 km
as supposed by Kopecký (1977).
The occurrences of hypabyssal stocks and particularly the
above mentioned dense (more than 1000) dyke swarms make
the RIC an important structure. Dykes associated with the in-
trusive centre reveal to some degree a radial, fan-shaped ar-
rangement to the centrally located crater vent and associated
hypabyssal intrusions (Hibsch 1926, 1936) of monzodiorite
essexite (Fig. 1). Nevertheless, the hypabyssal bodies of
monzodioriteessexitesodalite syenite series are also partly
linear-arranged, forming two subparallel lines striking NNW
SSE in the central part of the CSM, transverse to the course of
the OR (ENEWSW), see Strnad (1965), Kopecký (1978) and
Ulrych & Novák (1989).
Strongly differentiated dyke rocks form a predominantly ra-
dially orientated dyke system reaching to a distance of 1015
km from the RIC. The dyke system of the RIC is composed of
mafic derivatives (semi)lamprophyres totally prevailing
over felsic derivatives and basaltic dykes (Ulrych 1998). Hy-
pabyssal Weakly Alkaline Series and two coexisting dyke se-
ries Weakly Alkaline and Strongly Alkaline Series were rec-
ognized by Ulrych (1998). Monzodiorite (rongstockite of
Tröger 1935) forms a singular hypabyssal strongly tectonized
intrusion located at Roztoky (Rongstock). Three elliptic stocks
of essexite near Malé Bøezno and three laterally positioned so-
dalite syenite bodies (Malé Bøezno, Svádov, Zubrnice) repre-
sent rocks of the Hypabyssal Weakly Alkaline Series
(HWAS). Hornblendite is a typical cumulate in the sodalite sy-
enites, camptonites and gauteites semilamprophyres sen-
su Wimmenauer (1973). The Roztoky crater vent with a tra-
chytic filling is younger than the subvolcanic body of
monzodiorite and (semi)lamprophyre dykes with the exception
of felsic dykes penetrating the trachyte breccia.
The RIC is accompanied by the Tertiary PbZnCu(Ag,Te)
hydrothermal mineralization (Pivec et al. 1984, 1998).
Methods of study
The average data on chemical composition of principal rock
types of the RIC were modified from Ulrych (1989). Chemical
analyses were performed by wet methods, trace element con-
centrations were analysed by XRF and INAA methods. For
conditions of measurement see Ulrych (1989).
K-Ar ages were measured at the Institute of Nuclear Re-
search of the Hungarian Academy of Sciences, Debrecen.
Crushed rock samples were washed and their aliquots were
pulverized for K determination. The samples were degassed
by high-frequency induction heating, the usual getter materials
(titanium sponge, getter pills of SAES St 707 type) were used
for cleaning of Ar. The
38
Ar spike was introduced to the sys-
tem from a gas-pipette before the degassing was started. The
cleaned Ar was directly introduced into the mass spectrometer.
The mass spectrometer was a magnetic sector type of 150 mm
radius and 90° deflection operating in static mode. The argon
extraction line and the mass spectrometer were constructed at
the Institute of Nuclear Research. Potassium concentrations
were measured by flame photometry using Na and Li as buff-
ers and internal standards. The interlaboratory standards Asia
1/65, HDB1, LP6 and GLO as well as atmospheric Ar
were used for controlling and calibrating the determinations.
Details of the instruments, the applied methods and results of
calibration were described by Balogh (1985) and Odin et al.
(1982).
Geochemical characteristics of subvolcanic rocks
series
The mineral, petrographic and geochemical characteristics,
including Sr and Nd isotope studies, of the individual subvol-
canic rocks of the RIC were presented by Ulrych et al. (1983,
1998, 2000) and Jelínek et al. (1989). For chemical composi-
ROZTOKY INTRUSIVE CENTRE: DIFFERENTIATION AND AGE OF DYKE SERIES 385
tions of the rocks see Table 1a,b,c. Three main alkaline
rock series of the RIC were recognized by Ulrych (1998)
and the fourth series by Ulrych et al. (2000) see TAS dia-
gram in Fig. 2:
Hypabyssal weakly alkaline plutonic series (HWAS)
formed by essexitemonzodioritesodalite syenite is charac-
terized by D.I. = 4664, Mg # = 4452, A.I. = 0.600.78; a
dyke of leucomonzonite is the most highly differentiated prod-
uct of monzodiorite (D.I. = 80; Mg # = 32; A.I. = 0.81); horn-
blendite cumulates are the most mafic products of the RIC
suite (D.I. = 30; Mg # = 60; A.I. = 0.53). The A.I. increases in
the monzodioritesodalite syeniteleucomonzonite hypabys-
sal rock series (0.600.81) and from mafic to felsic types in
both dyke series. The fO
2
value of mineral assemblages in-
creases with decreasing depth of their crystallization level in
the (monzodioriteessexitesodalite syenite)-dyke rock series
(Ulrych et al. 1983).
Weakly alkaline dyke series (WAS) formed by (trachy-
basalt ?)camptonite/gauteite Isodalite syenite porphyry
gauteite II(trachyte ?) (D.I. = /39/6581; Mg # = 3241; A.I.
= 0.570.75).
Strongly alkaline dyke series (SAS) composed of
(tephrite/basanite?)camptonite/monchiquite(tephriphono-
litephonolite/tinguaite/nepheline syenite porphyry ?) (D.I. =
/39/4787; Mg # = 1650/55/; A.I. = /0.53/0.571.04). Coex-
isting SAS and WAS are similar to rock associations described
from Cantal, Massif Central, France by Wilson et al. (1995),
Siebengebirge, Germany by Vieten et al. (1988) and the Teplá
Highland, Bohemia by Pivec et al. (in print).
Old felsic series (OFS) (42.738.2 Ma) formed by bos-
tonite Inepheline phonolite corresponding to older phono-
lite of Hibsch (1926). Rhyolites known as xenoliths (?) in
bostonite I dykes originated by melting of gneisses from the
crystalline basement (Ulrych et al. 2000).
Fig. 1. A sketch of the Roztoky Intrusive Centre with special attention to dyke distribution (Hibsch 1930 adapted). Map sheets 1 : 25,000. 1
RoztokyPodmokly, 2 Beneov nad Plouènicí, 3 Velké Bøezno, 4 Verneøice.
386 ULRYCH
and BALOGH
Table 1a: Average chemical composition of hypabyssal rock series of the Roztoky Intrusive Centre.
E essexite, MD monzodiorite, LM leucomonzonite, SS sodalite syenite, H hornblendite, SMS sodalite monzosyenite; x mean, s standard deviation,
n number of samples. (D.I. differentiation index sensu Thornton & Tuttle 1960; Mg# = Mg/(Mg + Fe2+); Fe3+/Fe = 0.15; A.I. alkalinity index sensu Shand 1922).
Rock
E
MD
LM
SS
H
SMS
wt. %
x
s
n
x
s
n
x
s
n
x
s
n
x
s
n
x
s
n
SiO
2
46.40
0.94
16
47.03
2.14
11
54.23
0.91
2
51.06
1.44
13
42.42
1.23
14
49.83
1.30
14
TiO
2
3.24
0.62
16
2.46
0.57
11
1.20
0.04
2
1.76
0.43
13
4.34
0.70
14
1.73
0.27
14
Al
2
O
3
14.61
1.96
16.68
0.68
11
17.68
0.26
2
16.25
1.34
13
11.91
1.35
14
17.21
0.79
14
Fe
2
O
3
5.57
1.78
16
5.35
1.08
11
3.78
0.97
2
5.56
1.04
13
5.50
0.78
14
2.94
0.24
14
FeO
5.30
1.20
16
5.11
1.17
11
1.69
1.10
2
2.36
0.59
13
7.06
1.01
14
3.78
0.27
14
MnO
0.21
0.06
16
0.26
0.05
11
0.09
0.05
2
0.28
0.20
13
0.22
0.53
14
0.16
0.04
14
MgO
5.13
1.02
16
3.79
0.49
11
1.15
0.03
2
2.70
0.68
13
8.60
1.65
14
1.94
0.46
14
CaO
9.32
1.20
16
8.80
0.64
11
3.49
0.60
2
6.53
1.44
13
11.83
0.68
14
6.40
0.62
14
Na
2
O
3.88
0.79
16
4.00
0.42
11
4.99
0.05
2
5.25
1.01
13
2.93
0.77
14
4.14
0.82
14
K
2
O
3.28
0.56
16
3.18
0.51
11
5.63
0.57
2
3.78
0.54
13
1.42
0.43
14
3.98
0.23
14
P
2
O
5
0.59
0.20
16
0.95
0.95
11
0.32
0.05
2
0.43
0.16
13
1.37
0.22
14
0.53
0.07
14
H
2
O
+
1.54
1.02
16
1.45
0.60
11
2.14
0.09
2
3.08
0.95
13
1.42
0.51
14
2.28
0.60
14
H
2
O
0.50
0.33
16
0.42
0.24
11
0.48
0.25
2
0.73
0.45
13
0.99
0.60
14
1.70
0.99
14
CO
2
0.31
0.24
10
0.72
0.37
8
2.87
1.03
2
1.00
0.67
9
0.77
0.23
14
2.91
1.48
10
F
0.10
0.02
10
0.13
0.03
8
0.05
0.03
2
0.08
0.03
9
0.15
0.02
14
0.10
0.03
10
S
0.03
0.01
6
0.15
0.13
5
0.31
0.06 2
0.04
0.02
5
0.08
0.03
5
0.05
0.01
4
Total
100.01
100.48
100.10
100.89
99.44
99.68
Q
2.39
2.43
C
3.77
2.42
Or
19.83
19.13
34.29
23.06
8.54
24.64
Ab
17.51
24.72
43.42
35.43
17.80
36.62
An
13.00
18.43
0.83
9.87
15.37
10.75
Ne
8.67
5.23
5.60
4.00
Ac
Ns
Di
22.36
12.38
11.22
24.44
Hy
2.96
7.11
Ol
2.04
3.70
1.24
8.54
Mt
8.25
7.89
2.33
3.52
8.11
4.46
Hm
2.29
3.31
Il
6.29
4.75
2.35
3.45
8.38
3.44
Ap
1.32
2.11
0.97
3.04
1.21
Li ppm
28.00
1.00
3
23.00
3.00
7
27.00
1
39.00
1.00
3
10.00
1.00
3
31.00
4.00
6
Rb
74.00
14.00
7
58.00
11.00
7
114.00
1
98.00
29.00
13
9.40
6.30
3
108.00
4.00
10
Cs
0.85
0.09
3
1.30
1.10
4
1.90
1
2.20
0.30
3
0.11
0.03
3
22.00
0.40
6
Sr
970.00
287.00
7 1,012.00
168.00
7
575.00
1 1,518.00 237.00
13
330.00
165.00
3 1,350.00
95.00
10
Ba
1,035.00
113.00
7
936.00
57.00
7
485.00
1 1,296.00 137.00
13
558.00
33.00
3 1,407.00
50.00
10
Ga
19.00
5.80
3
18.30
1.30
7
21.10
1
21.00
1.00
3
11.00
1.10
3
19.00
1.70
3
Pb
2.30
5.80
3
1.50
1.70
7
1.00
1
8.00
1.70
3
-
-
3
5.00
1.30
3
As
10.00
1.00
3
10.70
2.70
7
9.20
1
7.70
1.20
3
18.00
1.40
3
6.00
1.00
3
Sc
17.30
1.40
3
13.00
2.20
5
5.10
1
4.80
0.40
3
73.00
12.00
3
6.80
0.30
6
Y
22.00
2.00
3
25.00
3.00
4
27.00
1
33.00
1.00
3
7.50
4.30
3
21.00
2.00
10
La
65.00
2.00
3
52.00
6.00
5
79.00
1
114.00
3.00
3
24.00
3.30
3
85.00
3.00
6
Ce
145.00
6.00
3
128.00
30.00
5
171.00
1
224. 00
11.00
3
81.00
14.00
3
150.00
5.00
6
Pr
1
Nd
55.00
6.00
3
42.00
21.00
5
65.00
1
50.00
1.00
3
35.00
4.00
3
41.00
5.00
6
Sm
9.10
0.50
3
9.60
2.80
5
9.90
1
10.50
0.30
3
7.20
1.90
3
9.00
0.33
6
Eu
2.50
0.10
3
2.60
3.50
5
2.70
1
2.90
1.60
3
2.60
0.60
3
2.60
0.05
6
Gd
6.60
0.40
3
6.50
0.60
5
6.90
1
7.80
0.40
3
6.22
0.50
2
6.90
0.40
3
Tb
0.97
0.07
3
0.89
0.14
5
1.00
1
1.02
0.06
3
0.93
0.10
3
0.96
0.04
6
Dy
1
Ho
1.02
0.16
3
0.98
0.50
4
1.10
1
1.13
0.23
3
0.85
0.25
2
1.04
0.21
6
Er
1
Tm
0.39
0.14
3
0.36
0.23
4
0.40
1
0.47
0.08
3
0.21
0.11
3
0.22
0.10
6
Yb
2.40
0.10
3
1.90
0.40
4
2.50
1
2.50
0.20
3
1.01
0.21
3
1.80
0.20
6
Lu
0.40
0.10
3
0.51
0.01
4
0.48
1
0.44
0.07
3
0.22
0.17
3
0.16
0.10
6
Th
11.10
3.20
7
7.10
1.20
5
10.20
1
15.60
3.80
13
0.89
0.20
3
12.40
0.40
6
U
4.10
0.80
3
2.50
0.70
4
4.40
1
6.00
0.20
3
0.14
0.10
3
3.00
0.90
6
Zr
369.00
85.00
7
330.00
66.00
7
402.00
1
519.00
35.00
13
112.00
17.00
3
314.00
13.00
10
Hf
10.20
0.40
3
8.00
1.70
5
10.00
1
10.00
0.50
3
1.80
0.50
3
8.70
0.20
6
V
243.00
37.00
7
211.00
21.00
7
181.00
1
143.00
48.00
13
434.00
73.00
3
122.00
27.00
3
Nb
74.00
31.00
7
71.00
15.00
7
110.00
1
140.00
14.00
13
48.00
14.00
3
185.00
15.00
10
Ta
5.90
0.30
3
5.30
1.40
4
7.20
1
9.40
0.50
3
2.90
1.80
3
14.00
0.10
6
Cr
27.00
6.00
3
16.90
4.80
7
5.10
1
4.70
1.20
3
40.00
6.00
3
6.90
3.20
6
Co
31.00
18.00
7
41.00
26.00
7
19.00
1
22.00
14.00
13
47.00
17.00
3
6.60
1.90
10
Ni
8.70
1.50
3
7.10
2.20
7
2.90
1
3.00
1.00
3
209.00
44.00
3
4.10
0.60
3
Cu
35.00
5.00
3
17.10
4.60
7
7.10
1
11.30
0.60
3
32.00
11.00
3
12.70
3.10
3
Zn
89.00
19.00
7
97.00
26.00
7
7.30
1
91.00
17.00
13
60.00
7.00
3
91.00
6.00
6
D.I.
46.02
49.09
80.10
64.09
30.34
63.68
C.I.
36.95
28.72
7.63
19.43
49.47
15.20
Mg
51.06
44.47
32.14
43.67
60.02
20.63
A.I.
0.68
0.60
0.81
0.78
0.53
0.65
K/Rb
368.00
455.00
414.00
320.00
1,254.13
318.00
Rb/Sr
0.08
0.06
0.20
0.05
0.03
0.08
Th/U
2.71
2.84
2.32
2.60
6.36
4.13
Zr/Hf
41.30
36.20
40.20
51.90
62.22
36.10
Nb/Ta
12.54
13.40
15.28
14.89
16.55
13.21
Ti/V
69.90
79.80
39.70
73.80
60.00
85.00
5 REE
288.38
245.34
340.18
414.76
159.24
298.68
(La/Yb)
19.43
19.63
22.67
32.71
17.04
36.95
Eu/Eu*
0.94
0.95
0.95
0.94
1.16
0.97
ROZTOKY INTRUSIVE CENTRE: DIFFERENTIATION AND AGE OF DYKE SERIES 387
Table 1b: Average chemical composition of dyke rocks of the WAS of the Roztoky Intrusive Centre.
Tb
trachybasalt, Mh - mondhaldeite, SSP
sodalite syenite porphyry, G
gauteite, Bo
bostonite, T
trachyte, R
rhyolite.
Rock
Tb
Mh
SSP
G
Bo
T
R
wt. %
x
s
n
x
s
n
x
s
n
x
s
n
x
s
n
x
s
n
x
1
SiO
2
45.59
1.58
3
46.87
0.34
2
47.20
0.32
2
53.26
2.78
20
55.41
0.85
5
55.23
3.59
15
66.70
TiO
2
2.84
0.33
3
2.78
0.09
2
1.76
0.78
2
1.66
0.47
20
1.38
0.44
5
0.88
0.60
15
0.35
Al
2
O
3
14.28
1.05
3
17.24
0.04
2
18.54
0.21
2
18.04
2.31
20
17.75
0.97
5
19.15
1.57
15
16.25
Fe
2
O
3
5.95
1.94
3
5.18
0.11
2
3.20
1
3.78
1.42
12
4.19
0.95
5
2.82
1.69
11
0.06
FeO
5.68
0.58
3
3.54
0.13
2
2.64
1
2.54
1.34
12
1.40
1.75
5
1.50
1.22
11
1.65
MnO
0.20
0.79
3
0.18
0.01
2
0.16
0.01
2
0.18
0.08
20
0.25
0.20
5
0.12
0.07
15
0.02
MgO
4.97
1.86
3
2.23
0.04
2
1.22
0.04
2
1.97
0.77
20
1.32
0.63
5
0.91
0.81
15
0.55
CaO
10.92
1.72
3
5.76
0.25
2
7.00
0.27
2
5.04
1.33
20
4.45
0.66
5
3.12
1.47
15
2.90
Na
2
O
3.33
0.19
3
4.02
0.02
2
4.66
0.07
2
4.48
1.36
20
5.15
0.68
5
4.74
1.08
15
4.15
K
2
O
2.43
0.69
3
3.77
0.06
2
4.47
0.15
2
5.12
1.25
20
4.42
0.77
5
5.77
1.34
15
2.70
P
2
O
5
0.81
0.34
3
0.60
0.02
2
0.35
0.01
2
0.38
0.11
20
0.47
0.21
5
0.17
0.14
15
0.03
H
2
O
+
2.63
1
1.33
0.09
2
3.82
1
2.25
1.06
7
0.65
0.69
5
3.07
1.23
11
3.55
H
2
O
0.62
1
0.56
0.02
2
0.51
1
0.49
0.37
7
2.33
0.47
5
0.66
0.54
11
1.25
CO
2
0.18
1
4.83
0.15
2
3.45
1
1.19
1.58
12
1.46
0.96
5
2.22
1.97
11
F
0.10
0.03
7
S
0.10 0.08
7
Total
100.43
98.89
98.98
100.38
100.63
100.56
100.16
Q
6.78
2.29
4.19
25.37
C
7.46
2.14
0.79
5.09
1.34
Or
14.79
22.99
27.93
31.03
26.77
35.32
16.75
Ab
18.84
35.03
35.62
38.17
44.57
41.46
36.78
An
17.29
1.98
11.51
14.20
10.35
0.48
14.91
Ne
5.49
3.23
0.34
Ac
Ns
Di
25.45
1.13
Hy
5.75
3.38
2.35
4.00
Ol
1.48
2.26
3.17
Mt
8.88
4.05
4.15
4.06
1.36
2.77
0.09
Hm
2.54
0.52
1.08
3.35
1.01
Il
5.55
5.45
3.53
3.23
2.69
1.73
0.70
Ap
1.82
0.81
0.85
1.05
0.38
0.07
Li ppm
Rb
67.00
24.04
3
145.00
12.00
2
124.50
14.85
2
112.77
37.93
15
115.50
20.51
4
145.71
19.21
10
61.00
Cs
1.40
1
1.50
0.42
2
4.10
1
1.53
Sr
1192.50 342.95
3
794.50
21.92
2
1258.00 195.16
2
899.12 171.22
15
1012.50 194.50
4
812.86 391.35
3
677.00
Ba
1349.50 338.72
3
1146.00
93.34
2
1010.00
14.14
2
1190.77 303.19
15
1154.50
24.75
4
1287.50 286.79
10
1194.00
Ga
37.00
1
24.00
1
23.00
0.00
2
26.20
3.27
7
18.00
1
26.00
1
18.00
Pb
5.33
2.08
3
10.50
3.54
2
8.50
0.71
2
10.25
9.02
8
23.50
2.12
2
14.00
1
21.00
As
6.50
0.50
2
1.50
1
13.00
Sc
6.17
1
3.80
1
7.44
1.07
2
5.19
1.26
2
3.40
Y
26.00
8.48
3
32.00
1
23.00
2
23.75
5.40
15
30.50
0.71
2
20.00
1
22.00
La
61.00
1
81.00
1
65.00
1
61.30
2.40
2
58.50
1.41
2
93.00
1
137.00
Ce
129.00
1
161.00
1
173.00
1
134.50
21.92
2
163.50
0.71
2
109.00
1
82.00
Pr
Nd
47.80
1
52.00
1
59.00
11.30
2
63.50
3.54
2
20.00
Sm
10.10
1
10.40
1
10.40
2.55
2
15.00
0.00
2
3.90
Eu
2.98
1
2.50
1
2.60
0.14
2
2.50
0.06
2
1.00
Gd
7.90
1
6.90
1
6.80
0.22
2
6.00
0.17
2
2.60
Tb
1.00
1
0.79
1
0.83
0.04
1
0.90
0.09
2
0.37
Dy
1
4.30
1
5.40
1
Ho
0.99
1
0.90
1
0.88
1
1.05
2.13
2
Er
2.10
1
Tm
0.30
1
0.24
1
0.21
1
Yb
1.80
1
1.10
1
1.20
0.14
2
1.00
0.15
2
0.90
Lu
0.31
1
0.15
1
0.12
0.17
2
0.14
0.02
2
0.12
Th
12.00
4.24
3
11.50
1
12.00
1.41
2
15.83
5.04
7
14.80
3.11
2
11.20
1
27.00
U
3.00
0.24
3
2.50
2.12
2
4.00
2
2.50
2.12
3
3.10
0.17
2
2.80
2.12
3
3.50
Zr
395.50
34.65
3
420.00
38.18
2
549.00
2
434.50
80.28
15
452.50
28.73
4
556.86 100.68
10
239.00
Hf
6.20
1
8.60
9.10
0.71
2
6.90
1
5.00
V
260.00
1
245.00
7.07
2
230.00
2
205.71
35.52
7
150.50
41.72
4
225.71
59.68
10
170.00
Nb
81.00
1
71.00
1
110.00
1
88.00
25.13
7
119.00
1
125.00
21.21
10
21.00
Ta
4.00
1
4.60
1
5.30
0.57
2
5.50
1
0.60
Cr
41.50
2.12
3
22.50
9.19
2
9.00
1.41
2
16.31
8.05
15
10.50
0.71
4
11.00
6.53
10
24.00
Co
32.33
0.58
3
21.00
2.83
2
10.50
6.36
2
13.71
4.56
15
17.00
3.15
4
11.86
11.31
10
2.10
Ni
25.33
9.29
3
15.00
1.41
2
2.50
0.71
2
10.25
9.02
7
6.05
2.83
4
5.89
3.76
10
22.00
Cu
49.67
0.17
3
19.50
6.36
2
12.50
7.78
2
17.00
13.06
15
10.51
0.73
4
3.71
1.98
10
12.00
Zn
80.67
2.08
3
70.50
28.99
2
69.50
41.75
2
69.13
13.14
15
90.50
7.78
4
35.43
11.96
10
40.00
D.I.
39.12
64.79
66.80
69.53
73.64
80.96
78.90
C.I.
41.36
15.25
9.94
11.58
7.42
6.85
4.78
Mg
48.57
36.31
31.67
41.01
34.87
32.09
40.36
A.I.
0.57
0.57
0.67
0.72
0.75
0.73
0.60
K/Rb
301.10
215.85
298.07
376.93
317.70
328.75
367.47
Rb/Sr
0.06
0.18
0.10
0.13
0.11
0.18
0.09
Th/U
4.00
4.60
3.00
6.33
4.77
4.00
7.71
Zr/Hf
67.74
63.84
47.75
65.58
47.80
Nb/Ta
17.75
23.91
16.60
21.64
35.00
Ti/V
65.48
68.02
45.87
48.38
54.97
23.37
12.34
5 REE
190.00
315.18
317.28
285.34
312.09
202.00
247.89
(La/Yb)
N
32.28
42.39
36.64
41.96
109.19
Eu/Eu*
0.80
0.85
0.89
0.68
0.74
388 ULRYCH
and BALOGH
Table 1c: Average chemical composition of dyke rocks of the SAS of the Roztoky Intrusive Centre.
Te/Ba
tephrite/basanite, M
monchiquite, C
camptonite, Tp
tephriphonolite, TiP
tinguaite porphyry, NSP
nepheline syenite porphyry, P
phonolite, Ti
tin-
guaite, TiA
anomalous tinguaite.
Rock
Te/Ba
M
C
Tp
TiP
NSP
P
Ti
TiA
wt. %
x
s
n
x
s
n
x
s
n
x
1
x
s
n
x
s
n
x
1
x
s
n x
1
SiO
2
43.12
1.90
3
44.01
1.81
24
45.78
2.30
30
50.43
52.93
2.30
3
53.13
0.37
3
54.85
56.54
0.80
4
59.32
TiO
2
2.87
1.10
3
3.02
0.75
24
2.65
0.47
30
1.27
1.22
0.08
3
0.85
0.35
3
0.47
0.41
0.18
4
0.27
Al
2
O
3
15.81
2.87
3
15.09
1.50
24
16.21
1.43
30
18.22
18.07
1.46
3
19.58
1.19
3
20.88
20.08
0.87
4
18.30
Fe
2
O
3
5.07
0.40
3
5.72
1.35
18
5.31
0.69
24
2.64
3.82
2.12
3
1.96
0.22
3
2.13
1.53
0.61
4
1.45
FeO
5.53
0.25
3
5.14
1.20
18
4.46
0.90
24
2.41
2.57
0.78
3
1.73
0.40
3
1.24
1.53
0.43
4
1.04
MnO
0.20
0.03
3
0.21
0.08
24
0.18
0.04
30
0.19
0.24
0.11
3
0.34
0.31
3
0.19
0.22
0.16
4
0.30
MgO
6.03
1.67
3
4.81
1.23
24
4.34
1.21
30
1.03
0.79
0.21
3
0.80
0.15
3
0.46
0.34
0.14
4
0.05
CaO
9.91
2.05
3
9.62
1.86
24
9.07
1.68
30
5.29
4.50
0.69
3
3.26
0.35
3
2.83
2.13
0.59
4
1.06
Na
2
O
3.31
0.48
3
3.93
0.61
24
3.34
1.29
30
6.31
6.77
0.48
3
7.72
1.14
3
7.99
7.81
1.43
4
8.49
K
2
O
2.78
0.65
3
3.37
1.08
24
3.46
0.93
30
4.86
4.91
0.19
3
4.16
0.26
3
5.40
5.69
0.48
4
4.95
P
2
O
5
0.57
0.15
3
0.68
0.18
24
0.63
0.18
30
0.27
0.24
0.04
3
0.08
0.02
3
0.10
0.15
0.10
4
0.04
H
2
O
+
2.66
1.17
3
2.27
1.34
8
2.34
0.42
14
4.96
1.69
0.36
3
3.59
0.72
3
2.29
0.97
0.33
4
0.65
H
2
O
0.83
0.38
3
1.58
1.21
8
0.78
0.26
14
0.98
0.63
0.17
3
0.45
0.21
3
0.39
1.57
1.34
4
2.81
CO
2
0.55
0.14
3
1.75
1.43
18
0.95
1.11
24
0.39
1.80
2.01
3
1.57
1.04
3
0.28
0.87
0.98
4
0.32
F
S
0.04
0.01
3
0.07
0.04
8 0.08
1
0.14
1
Total
99.28
101.27
99.58
99.25 100.18
99.22
99.50
99.84
99.05
Q
15.42
30.21
C
0.21
Or
17.17
20.48
21.23
30.85
29.68
25.84
32.00
43.77
30.63
Ab
12.09
17.53
21.13
31.62
37.63
43.42
39.44
An
20.92
13.91
19.68
7.50
4.47
6.19
5.12
Ne
9.28
8.99
4.42
13.88
11.30
13.60
15.29
Ac
5.54
4.38
Ns
13.91
16.32
Di
18.33
15.31
13.18
5.97
4.12
2.67
3.63
2.78
Hy
2.59
0.78
Ol
6.23
3.76
3.61
0.80
2.09
Mt
7.68
8.52
7.55
0.67
5.65
3.02
3.09
Hm
0.30
5.25
0.01
Il
5.70
5.89
5.22
2.37
1.70
0.89
0.78
0.54
Ap
1.30
1.52
1.43
0.63
0.54
0.18
0.22
0.33
0.09
Li ppm
Rb
47.00
1
75.50
26.80
10
82.29
35.51
23 111.00 133.00
12.73
2 162.00
1 138.00 168.00
1
733.00
Cs
3.10
1.41
2
0.91
1
10.20
1
6.20
1
3.00
1
Sr
1058.00
1 872.33 260.94
10 927.10 218.21
23 1403.00 912.00 305.47
2 1830.00
1 1969.00 1315.00
1
92.00
Ba
1210.00
1 760.40 257.35
19 1038.57 357.57
23 1180.00 1429.00
2 1581.00
1 1668.00 1154.00
1
23.00
Ga
29.00
1
25.33
3.25
10
23.67
2.83
10
27.00
31.00
1
33.00
1
28.00
29.00
1
51.00
Pb
3.00
1
8.94
3.70
19
9.87
4.59
23
15.00
20.50
10.61
2
14.00
1
17.00
42.00
24.09
2
76.00
As
2.00
1
Sc
12.77
1.46
2
15.58
4.43
4
141.00
1
1.81
1
2.25
1
Y
19.00
1
27.44
6.00
10
25.05
4.65
23
22.00
22.00
5.66
2
20.00
1
33.00
30.00
1
29.00
La
57.00
1
60.00
12.52
4
54.88
7.96
4
97.00 100.00
1
87.00
1 110.00
94.60
1
198.00
Ce
89.00
1 147.33
40.67
4 135.25
14.59
4 131.00 147.00
1 181.00
1 134.00 137.00
1
213.00
Pr
18.40
1
14.45
0.49
2
11.90
1
Nd
66.00
16.37
4
53.00
8.04
4
31.50
1
39.00
1
20.00
1
Sm
11.90
3.54
4
11.70
3.65
4
3.40
1
7.50
1
4.64
1
Eu
2.67
0.55
4
2.68
0.19
4
1.00
1
1.70
1
1.43
1
Gd
6.25
0.35
4
6.50
2.17
4
2.50
1
5.10
1
4.70
1
Tb
0.73
0.04
4
0.96
0.35
4
0.42
1
0.70
1
0.81
1
Dy
4.20
1
5.38
0.35
2
2.40
1
Ho
0.88
1
1.02
0.94
4
0.50
1
1.20
1
Er
2.20
1
2.52
0.25
2
1.60
1
Tm
0.31
1
0.31
0.28
2
0.30
1
0.15
1
Yb
2.33
0.67
4
1.75
1.06
4
2.30
1
2.30
1
3.10
1
Lu
0.30
1
0.30
0.00
2
0.40
1
0.43
1
Th
10.00
1
11.50
3.55
10
13.00
5.38
10
13.00
16.00
1
19.00
1
17.00
23.20
1
146.00
U
2.00
1
3.00
0.00
2
3.00
0.00
3
2.00
6.00
1
3.00
1
4.00
4.30
1
38.00
Zr
354.00
1 363.67
83.18
10 355.24
85.10
10 481.00 550.50
21.92
2 598.00
1 584.00 639.00
1 1479.00
Hf
6.85
1.34
4
6.56
1.06
2
8.50
1
8.60
1
11.90
1
V
310.00
1 270.00
64.03
10 222.78
58.48
10 200.00 245.00
77.78
2 110.00
1 190.00
64.00
1
Nb
63.00
1
70.83
17.83
10
95.29
47.85
10
86.00 131.00
1 118.00
1
75.00 113.00
1
721.00
Ta
1
5.30
0.42
4
4.65
0.21
2
6.30
1
3.00
1
4.10
1
Cr
11.00
1
35.94
23.18
19
30.78
2.00
23
5.00
5.00
0.00
2
15.00
1
19.00
6.00
2.83
2
4.00
Co
55.00
1
33.37
8.81
19
24.35
7.01
23
5.00
9.50
1.73
2
8.20
1
4.00
6.00
5.66
2
7.00
Ni
23.00
1
15.24
8.64
19
20.18
8.28
23
3.00
4.50
2.12
2
6.00
1
3.00
2.00
1.41
2
8.00
Cu
32.00
1
47.82
35.03
19
36.61
16.28
23
8.00
11.50
6.39
2
17.00
1
8.00
11.10
0.72
2
9.00
Zn
75.00
1
71.18
23.36
19
78.00
22.36
23
75.00
70.75
35.54
2 102.00
1
55.00 110.00
16.97
2
251.00
D.I.
38.55
47.00
46.78
76.35
78.60
82.87
86.73
59.20
60.84
C.I.
37.94
33.49
29.56
6.63
12.21
6.80
6.65
7.00
4.09
Mg
55.61
49.50
49.62
31.09
21.61
32.44
23.41
15.63
4.28
A.I.
0.53
0.67
0.57
0.86
0.91
0.88
0.91
1.04
1.06
K/Rb
491.05
370.57
349.07
363.49 306.49
213.19
324.86 281.18
56.06
Rb/Sr
0.04
0.09
0.09
0.08
0.15
0.09
0.07
0.13
7.97
Th/U
5.00
3.83
4.33
6.50
2.67
6.33
4.25
5.40
3.84
Zr/Hf
53.09
54.15
64.76
69.53
53.70
Nb/Ta
13.36
20.49
20.79
39.33
27.56
Ti/V
55.50
67.06
71.31
38.07
29.85
46.33
14.83
38.41
5 REE
146.00
323.50
290.70
228.00 305.22
324.30
244.00 268.06
411.00
(La/Yb)
N
18.47
22.49
31.19
27.13
21.89
Eu/Eu*
0.85
0.85
1.13
1.20
1.13
ROZTOKY INTRUSIVE CENTRE: DIFFERENTIATION AND AGE OF DYKE SERIES 389
Principal dyke rock characteristics
The study of the distribution of dyke rocks in the RIC was
based on field measurements and geological maps 1: 25,000
of Hibsch (18971927). Four principal dyke rock types were
distinguished by Hibsch (1936) in the central part of the
CSM: I (L) lamprophyres, II (SL) semilamprophyres,
III (BR) basaltic rocks and IV (FD) felsic derivatives.
Emplacement of dykes
Geological setting of the RIC showing central arrangement
is similar to that of the Alnö Complex (Kresten 1980). Tra-
chytic breccia of the Roztoky crater vent, with hidden hy-
pabyssal body/ies together with forceful diapiric essexitic
and syenitic intrusions (with signs of magmatic stoping),
caused up-doming of the overlying country rocks and forma-
tion of several systems of joints. The passive intrusions are
represented by the radial dyke system dominating the RIC,
representing fillings of radial joints around the central
intrusion(s). Tensional joints and, to a limited extent, proba-
bly also shear joints originated during the upward movement
of magma. After mass reduction and degassing of the volcanic
system (p
magma chamber
< p
overlying rocks
), subsidence of the wall-
rocks occurred being associated with an another set of tension-
al and shear joints above the central intrusion. These two
paired joint systems (sensu Kresten 1980) may be intruded by
magma forming ring dykes, and cone sheets. However, these
systems in the RIC are scarce. Cone sheets dipping to the pre-
supposed centre at moderate or steep dip angles are rare in the
RIC. Kopecký (1977, 1987) suggested that the ring dykes
are represented by the moderately dipping (50°30°) dykes of
trachytic composition. However, the presence of ring dykes
was not approved. Rare cone sheets are formed by young fel-
sic derivatives (trachyte, phonolite, nepheline syenite porphy-
ry, and tinguaite?). Their strikes are mostly straight and char-
acteristic semicircular forms are absent. They do not represent
classical cone sheets and rather correspond to the definition of
tangential dykes of Heinrich (1966). It is noteworthy that no
ring dykes and cone sheets have been recognized in Kaiserstu-
hl (Keller & Schleicher 1990).
Moderate dip angles (50°) of a group of nepheline syenite
porphyries (up to 13 m thick) would bring cone sheets to a
common shallow focus about 3 km below the present surface.
Taking erosion into account, the depth of the focus would be
not deeper than 3.6 km. The depth of the top of the magma
source is, however, estimated generally at deeper than 6.5 km
(at the time of intrusion), an exception being the unusual cone
sheet-like structures associated with the Homa Mountain car-
bonatite complex in Kenya (King et al. 1972), where the focus
lies at a depth of 12 km and the cone sheets appear to have
been emplaced by explosive activity. Trachytic cone sheets of
irregular geometries in the RIC commonly display dip angles
between 30° and 45°. There is probably a tendency for the in-
clination to be lower towards the outer side of the set and high-
er towards the centre of the complex.
Quantitative distribution
Dykes presented in the geological maps by Hibsch (1897
1927) were affiliated to the above mentioned principal rock
types (IIV), and dyke strikes and dips were verified in out-
crops. However, less than 70 % of dykes from the maps were
found in outcrops and are measurable today. New, yet un-
known dykes (20) were found in new artificial outcrops. Maxi-
mum dyke concentration (more than 94 % of dykes) is ob-
served on four map sheets (see Fig. 1) of Hibsch (1899; 1897;
1902; 1910), figures in parentheses denote the numbers of
dykes present: RoztokyPodmokly/RongstockBodenbach
(221), Beneov nad Plouènicí/Bensen (70), Velké Bøezno/
Großpriesen (344) and Verneøice/Wernstadt (144). Dyke rocks
occur less frequently also on 9 other map sheets of Hibsch
(18971927). The concept of genetic association of all dykes
in the central part of the CSM with the RIC (Hibsch 1930,
1936), including the MìruniceTøebenice sheet with dykes 27
km from the centre, is disputable. An overview of principal
dyke rocks types (altogether 816 dykes) recognized in the
CSM (according to Hibsch 1930 associated with the RIC ?) is
presented in Table 2.
The properties of dykes of the individual types (IIV) of
Hibsch (1936) revealed:
I (L) dominance of lamprophyric rocks (sensu Rock
1991) camptonite, monchiquite, mondhaldeite (58 %).
II (SL) marked presence of semilaprophyric rocks
(sensu Wimmenauer 1973) gauteite, bostonite II and I?
(28 %).
III (BR) minor presence of basaltic rocks (with sodalite
group minerals) sodalite/hauyne tephrite/basanite tra-
chybasalt (6 %).
IV (FD) minor presence of young felsic derivatives
trachyte, phonolite, tinguaite, tinguaite porphyry, nepheline
syenite porphyry (9 %).
Fig. 2. Position of rocks from the RIC in TAS diagram (Le Maitre
Ed. 1989) showing three differentiation series. Dykes of SAS: (Ba/
Te basanite/tephrite?), M monchiquite, C camptonite, Tp
tephriphonolite, TiP tinguaite porphyry, Ti tinguaite, TiA
anomalous tinguaite, NSP nepheline syenite porphyry. Dykes
of WAS: (Tb trachybasalt?), Mh mondhaldeite, SSP so-
dalite syenite porphyry, SMS sodalite-bearing monzosyenite, G
gauteite, (Bo bostonite I? and II), T trachyte, (R rhyo-
litexenolith?) (small symbols). Hypabyssal series: H hornblen-
dite, E essexite, MD monzodiorite, SS sodalite syenite,
Lm leucomonzonite (large symbols). Dashed line discriminates
alkaline from subalkaline fields.
390 ULRYCH
and BALOGH
The study of quantitative distribution of dyke rocks associ-
ated with the RIC was performed on four map sheets men-
tioned above in two modes: (i) not considering the alongstrike
lengths of dykes, (ii) considering the alongstrike lengths of
dykes. The quantitative distributions of dykes into four rock
types using the two methods are presented in Table 3 and Fig.
3. Minor differences were established in the distribution of in-
dividual dykes using the two methods (cf. Fig. 3).
Space distribution
A plot of strikes for radial dykes from the RIC area shows
several maxima of constructed dyke intersections. The sup-
posed main centre of the RIC is located in the area between the
Roztoky monzodiorite intrusion (Vysoký kopec Hill) and the
near group of essexite bodies forming Líska Hill at Malé
Bøezno and in the trachyte caldera filling (cf. Kopecký 1987).
A minor centre is located at Hraditì Hill at Svádov. The high
number of dyke rock derivatives on map sheet Zálezly (15) in-
dicates the possible presence of a hitherto unknown intrusive
centre; the most distant dyke differentiates (sheet Mìrunice
Tøebenice) lying ca. 27 km from the RIC may be associated
with this centre.
Frequences of individual dyke-rock types (IIV) were cal-
culated for different 10 km wide zones centered around the
Table 2: Distribution of dyke rock types in the Roztoky Intrusive
Centre based on Hibschs (1926) data.
Fig. 3. Distributions of principal dyke rock types (IIV) in the
Roztoky Intrusive Centre. Total n not considering the along-
strike lengths of dykes, cumulative length considering the
alongstrike lengths of dykes. L lamprophyres, SL semilam-
prophyres, BR basaltic rocks, FD felsic derivatives.
Table 3. Distribution of principal dyke rock types (IIV) in the
Roztoky Intrusive Centre.
RIC. With respect to the substantial drop in the number of
dykes at distances exceeding 10 km, such dykes were evalu-
ated as a single category. The numbers and cumulative num-
bers of all dyke-rock types (IIV) and their frequences in the
different zones, total numbers for the individual dyke-rock
types and their proportions are given in Table 4 and Fig. 4 to-
gether with the total and cumulative total number of dykes
(700) and their proportions in percent.
Statistical evaluation of dyke-rock distribution around the
RIC revealed:
small proportions of dykes (25 %) at distances smaller
than 1 km, with the exception of felsic derivatives (20 %);
basaltic dykes do not occur at this distance at all,
the highest proportions of dykes of all groups at dis-
tances between 24 km (5155 %),
strikes of radial dykes indicate the main intrusive centre
in the area of the monzodioriteessexite intrusions (Roz-
tokyMalé Bøezno) and a minor centre in the area of sodalite
syenite intrusions at Svádov,
high frequency (9198 %; felsic derivatives 100 %) of
dykes of all groups at distances smaller than 7 km from the
postulated Roztoky centre; this distance correlates with the oc-
Total n
0
50
100
150
200
250
300
350
400
450
Total n in %
0
10
20
30
40
50
60
70
80
90
100
Cumulative
length in %
0
10
20
30
40
50
60
70
80
90
100
Cumulative length
0
100
200
300
400
500
600
700
800
900
1000
IV
(FD
)
IV (FD)
I (S)
II (SL)
III (BR)
III
(BR
)
II
(SL
)
I (
L)
IV
(FD
)
III
(BR
)
II
(SL
)
I (
L)
IV
(FD
)
III
(BR
)
II
(SL
)
I (
L)
Dyke rock types
Number of dykes Number of dykes
n
in
Camptonite
52
6.37
Monchiquite
460
56.37
Hauyne monchiquite
25
3.06
Leucite monchiquite
11
1.35
Mondhaldeite
10
1.23
Total dark derivatives
558
68.38
Gauteite
161
19.73
Sodalite gauteite
28
3.43
Bostonite
65
7.97
Sodalite bostonite
3
0.37
Leucomonzosyenite
1
0.12
Total light derivatives
258
31.62
Total
816
100.00
Along strike
Rock type
dyke length (m)
I(L) II(SL) III(BR) IV(FD)
Total IIV
Number of dykes n
0100
122
37
5
6
170
100200
176
100
23
35
334
200300
72
42
4
13
131
300400
9
9
4
4
26
400500
18
4
2
4
28
500600
2
2
0
1
5
600700
4
0
1
0
5
700800
1
0
0
0
1
Total
404
194
39
63
700
Total ()
57.71
27.70
5.60
9.00
100.01
Cumulative length
864
431
96
157
1548
Cumulative length
55.81
27.84
6.20
10.14
99.99
ROZTOKY INTRUSIVE CENTRE: DIFFERENTIATION AND AGE OF DYKE SERIES 391
quantitative distribution of dykes of all groups at differ-
ent distances from the RIC centre is similar for all types of
dyke rocks with the exception of felsic derivatives, which oc-
cur at distances of < 5 km only, with a cumulative maximum
(85 %) within the range of 4 km; other dyke groups reveal
cumulative maximum (8283 %) within the range of 5 km
only high viscosity may cause the lower mobility of acid
magma.
Dyke orientations
Strikes of the dykes were estimated with a precision of 10°
from the above mentioned four map sheets 1: 25,000; strikes
of less than 70 % of dykes only could be tested in the field.
Dips of the radial dykes can be measured only rarely (15 %
of dykes), with totally prevailing dip angles of 9080°. Pre-
currences of sodalite syenite bodies which, according to Ko-
peckýs (1977) interpretation, have signs of ring-dyke arrange-
ment,
accumulation of foid (semi)lamprophyres, to a lesser
extent also of sodalite bostonites I (and sodalite trachyba-
salts), are spatially associated (Hibsch 1926) with sodalite
syenite bodies,
dyke differentiates at distances of >1520 km can be
hardly associated with the RIC a problem of opening of
joints and penetration of liquids at such distances,
another volcanic centre in the CSM with differentiated
dyke suite is the Býèkovice Intrusive Centre (Ulrych & Novák
1989); the most distant dyke differentiates in the Mìrunice
Tøebenice area may be associated with a yet unknown volcanic
centre located on the neighbouring map sheet Zálezly, with a
higher concentration of dyke derivatives,
Fig. 4. Distributions of principal dyke rock types (IIV) given by their frequencies of different distances from the Roztoky Intrusive Cen-
tre. L lamprophyres, SL semilamprophyres, BR basaltic rocks, FD felsic derivatives.
I(L)
0
10
20
30
40
50
60
70
80
90
100
0 - 1
2 - 3
4 - 5
6 - 7
8 - 9
over 10
km
%
II(SL)
0
10
20
30
40
50
60
70
80
90
100
0 - 1
2 - 3
4 - 5
6 - 7
8 - 9
over 10
km
%
III(BR)
0
10
20
30
40
50
60
70
80
90
100
0 - 1 2 - 3 4 - 5 6 - 7 8 - 9
over 10
km
%
IV(FD)
0
10
20
30
40
50
60
70
80
90
100
0 - 1
2 - 3
4 - 5
6 - 7
8 - 9
over 10
km
%
Total (I-IV)
0
10
20
30
40
50
60
70
80
90
100
0 - 1
2 - 3
4 - 5
6 - 7
8 - 9
over 10
km
%
392 ULRYCH
and BALOGH
Table 5: Preferred orientation of principal dyke rock types (IIV).
Table 4: Distribution of principal rock types (IIV) given by their frequencies at different distances from the Roztoky Intrusive Centre.
ferred orientations at the individual dyke groups are given in
Table 5; all measured strikes of the dykes are presented in
rose diagrams (Fig. 5). Strikes of dykes exposed on the right
and the left banks of the Labe River (Souèek et al. 1985) are
shown in the same figure. Variations in strikes of all dyke
groups in all four sectors of the RIC (Hobl 1987 data are
used) are presented in Fig. 6.
Analysis of the Tertiary paleostress history obtained from
field work and paleostress analysis of shear faults in the re-
gion of the central part of the Ohøe Rift in the CS was made
by Adamoviè & Coubal (1999). The mechanical model of
magma emplacement into an elastic host rock formulated by
Pollard (1973) based on Andersons presumption was used
by the above mentioned authors as a basis for the determina-
tion of the direction of maximum principal stress component
from the intrusion shape in horizontal cross section. Magma
inhibition and solidification occurred after magma pressure
equilibrated with the regional stress in the host rock. The
present geometries of intrusive bodies result from this equil-
ibrated stress field, thus giving evidence of the effects of
both the magma pressure and regional stress (Pollard et al.
1975; Delaney & Pollard 1981). Adamoviè & Coubal (1999)
distinguished b extension-dominated period in the Ohøe Rift
in the Middle Eocene to Middle Miocene:
b
1
paleostress field characterized by EW to NE
SW extension, effective in the eastern part of the Ohøe Rift in
the interval of 4026 Ma,
b
2
paleostress field characterized by NS extension
progressively spreading from its central part in the Most Ba-
sin (onset at 34 Ma) to its eastern part (onset at 26 Ma), and
b
3
paleostress field characterized by NWSE exten-
sion, commenced at 24 Ma.
The evaluation of dyke strikes of all types (IIV) revealed that:
dyke orientation was controlled (i) by the paleostress
field existing in the upper crust during magma ascent (Adam-
oviè & Coubal 1999), (ii) by orientations of pre-existing
fracture sets in the region, and (iii) by the superimposed local
stress field exerted by the rising intrusion(s). The pre-exist-
ing fracture sets used as pathways for magma ascent were
primarily represented by ruptures formed as reverse faults in
the latest Cretaceous and earliest Tertiary (Sub-Hercynian
and Laramide phases sensu Ziegler (1982)), and later modi-
fied as normal faults. To a lesser degree the dyke strikes may
be controlled by pre-Cretaceous ruptures at deep crustal level
(Saxothuringian Crystalline basement),
similar orientation maxima for steeply dipping radial
dykes (9080°) of the (semi)lamprophyres and basaltic dykes,
with totally prevailing strikes of 90° and 0°; similar preferred
strikes are also present in the Alnö Complex (Kresten 1980).
independent structural plan of the felsic derivatives
(FD) with prevailing dyke strikes of 330° and 90°,
preferred strikes of the (semi)lamprophyres (L and SL)
and basaltic dykes (BD) are neither parallel, nor perpendicu-
lar to the eminent structures of the Roztoky area, i.e. the axis
of the Ohøe Rift (70°), Labe Tectono-Volcanic Zone (300°)
or other structures; FD dykes (330°) reveal structural affinity
to the Zubrnice Fault (320°), and ore veins in the Roztoky
monzodiorite (2030°) and FD dykes (10°) to the fault dislo-
cating the Roztoky monzodiorite body (20°),
partly different strike maxima of the dykes on the right
and the left banks of the Labe River can be probably ex-
plained by the primarily(?) asymmetrical development of the
RIC dykes and/or, more probably, by the different represen-
tation of dykes of the individual groups (IIV) having char-
acteristic strikes on the two Labe River banks. The right
bank poses a relatively better preserved, tectonically subsid-
ed block with a higher number of dykes, however, practically
with no exposed dykes of the youngest LD group.
Rock type
I(L)
II(SL)
III(BR)
IV(FD)
Total (IIV)
Cumulative
total (IIV)
Distance
(km)
n
n in %
5n 5n in % n
n in % 5n 5n in %
n
n in % 5n
5n in % n
n in % 5n 5n in %
n
n in % n
5n
01
20
4.8
20
4.8
3
1.5
3
1.5
8
19.5
8
19.5
31
4.4
31
4.4
12
57
13.8
77
18.6
38
19.9
41
21.4
6
14.6
14
34.1
5
9.1
5
9.1
106
15.1
137
19.6
23
131
31.7
208
50.4
49
25.7
90
47.1
7
17
21
51.2
14
25.5
19
34.6
201
28.7
338
48.3
34
97
23.5
305
73.9
52
27.2
142
74.3
14
34.1
35
85.4
14
25.5
33
60.1
177
25.3
515
73.6
45
39
9.4
344
83.3
16
8.4
158
82.7
6
14.6
41
100.0
12
21.8
45
81.9
73
10.4
588
84.0
56
21
5.1
365
88.4
15
7.9
173
90.6
100.0
4
7.3
49
89.2
40
5.7
628
89.7
67
9
2.2
374
90.6
8
4.2
181
94.8
100.0
5
9.1
54
98.3
22
3.1
650
92.9
78
0
0
374
90.6
2
1
183
95.8
100.0
1
1.8
55
100.0
3
0.4
653
93.3
89
0
0
374
90.6
0
0
183
95.8
100.0
100.0
653
93.3
910
3
0.7
377
91.3
0
0
183
95.8
100.0
100.0
3
0.4
656
93.7
over 10
36
8.7
413 100.0
8
4.2
191 100.0
100.0
100.0
44
6.3
700 100.0
Total
413
191
41
55
700
Dyke rock types
max
"
min.
I(L) lamprophyres
90°
0°
60°
290°
40°
II(SL) semilamprophyres
90°
290°
0°
10°
40°
III(BR) basaltic rocks
330°
90°
290°
10°
50°
IV(FD) felsic derivatives
90°
0°
40°
320°
340°
Dykes total
90°
0°
290°
60°
40°
Dykes on right bank of Labe (SOUÈEK et al. 1985)
90°
300°
0°
60°
Dykes on left bank of Labe (SOUÈEK et al. 1985)
60°
90°
0°
300°
Ohøe Rift (axis)
70°
Labe Volcano-Tectonic Zone (axis)
300°
Zubrnice Fault transverse to the Ohøe Rift
320°
Fault dislocating the Roztoky monzodiorite body
20°
Polymetallic ore veins at Roztoky
2030°
ROZTOKY INTRUSIVE CENTRE: DIFFERENTIATION AND AGE OF DYKE SERIES 393
for the interval of 3126 Ma, the analysis of dyke geome-
tries indicates the dominance of regional stress characterized
by the emplacement of EW-striking dykes (L
≈
SL > BR > FD):
(i) the oldest BA dykes probably associated with the Low-
er Formation basanitic lavas (3129 Ma in the central part of
the CS) reveal, in addition to the prevailing EW strike, also
NS and NWSE strikes,
(ii) younger dykes (3126 Ma) of groups L and SL are
characterized by very similar pattern of dyke distribution
with marked preference of EW-striking dykes and minor N
S strikes,
(iii) a substantially different pattern is characteristic for the
youngest (2624 Ma) LD dykes with prevailing NWSE
strikes together with minor EW, WNWESE and NNE
SSW strikes.
Age relations
Mutual geological age relations between principal dyke-
rock types in the RIC were difficult to determine due to the
absence of relevant outcrops and dyke intersections. Dyke
dip angles are mostly high (8090°) and dykes in individual
outcrops are mostly subparallel. The following time succes-
sion (from older to younger) of the principal dyke-rock types
was established: basanitic (also the adequate extrusive for-
mation including a feeding channel of olivine nephelinite) >
essexitic and syenitic plutonic intrusions > semilampro-
phyres (gauteite) > lamprophyres (camptonite, monchiquite)
> trachybasaltic extrusive formation > felsic derivatives
(bostonite II? > > trachyte
≈
tinguaite). All these field data
are in agreement with radiometric K-Ar ages.
Multiple dykes consisting of several simple dykes adjacent
to one another or intruded alongside or within each are con-
siderably more frequent than classical dyke crossings. Multi-
ple dykes are represented in particular by older gauteite pa-
rental dykes penetrated or paralleled by camptonites, or
bostonite II dykes penetrated by tinguaite with glassy rims.
Older basaltic dykes BA are exclusively cut by all dykes (L
and SL). On the other hand, trachytes cut all dykes. This im-
plies that L and SL intruded into a uniform joint system, old-
er BA dyke groups into a partly different system, while the
youngest FD group into a totally different joint system. No
dyke-rock inclusions in other dykes were observed except of
rhyolite xenoliths in bostonite (Ulrych et al. 2000).
Subvolcanic products of plutonic HWAS and dyke SAS
and WAS represent various magmatic pulses of a crustal vol-
Fig. 5. Rose diagrams of strikes for principal dyke rock types (IIV) in the Roztoky Intrusive Centre. L lamprophyres, SL semilam-
prophyres, BR basaltic rocks, FD felsic derivatives.
Fig. 6. A sketch of the Roztoky Intrusive Centre with rose diagrams
of strikes for all dykes in four principal sectors of the centre.
394 ULRYCH
and BALOGH
canic chamber. However, tephrites/basanites of SAS and tra-
chybasalts of WAS probably belong to the extrusive Lower
and Upper Formations. The pertinence of trachytic rocks to
the WAS is also disputable. The individual above mentioned
rock series may represent products of separate pulses mediat-
ed by a subcrustal magmatic chamber.
K-Ar ages were published for various RIC rocks (Arakely-
anc et al. 1977; Bellon & Kopecký 1977; Wilson et al. 1994)
These data together with sixteen new K-Ar datings (whole-
rock and mineral ages) are presented in Table 6 and in Fig. 7.
The ages of individual dyke groups (IIV) of the intrusive vol-
canic series (sub 46) present in the RIC are distributed within
a relatively narrow interval of 3324 Ma (cf. 1813 Ma Kai-
serstuhl Keller & Streicher 1990; 7965 Ma Oseèná Com-
plex Pivec et al. 1998; 281265 Ma and 273241 Ma plu-
tonic intrusions of two segments of the Oslo Graben
Sundvoll et al. 1990). However, an influence of strong alter-
ation processes (e.g. propylitization of Hibsch 1926) of the
dyke derivatives and thermal effect of various younger intru-
sions can cause a loss of Ar. Excess of Ar can be associated
with crystallization of some minerals interceptors of Ar,
e.g. sodalite. All the above mentioned effects may result in
prolongation of magmatic activity in the RIC.
The following magmatic series were distinguished in the
region of the RIC:
1 Old felsic series (sodalite phonolites, sodalite tra-
chytes Shrbený & Vokurka 1985 and bostonites I) represent
the pre-RIC intrusive activity (42.738.2 Ma) in the central
part of the CSM.
2 Lower Formation (basanitic lavas and volcaniclas-
tites), representing extrusive volcanic products, pre-date
(36.125.5 Ma) the beginning of RIC intrusive activity
(HWAS); feeding channel of massive olivine nephelinite at
Table 6: K-Ar ages of the principal rock types from the Roztoky Intrusive Centre.
Dobkovice revealed the age of 30.929.3 Ma; tephrite/basan-
ite dykes are probably associated with this formation.
3 Upper Formation (trachybasaltic lavas and pyroclas-
tics) represents continued (partly overlapping with the Lower
Formation) extrusive volcanic activity (30.824.7 Ma); a
feeding channel at Vysoký Kámen Hill revealed the age of
27.1 Ma, a relict of the Vrabinec diatreme of 26.8 Ma (Pfe-
iffer et al. 1984); trachybasaltic dykes (with minerals of so-
dalite group) are probably associated with this formation.
4 Hypabyssal Weakly Alkaline Series with simulta-
neous bodies of essexites (33.131.3 Ma), monzodiorite
(32.729.5 Ma) and sodalite syenites (30.328.2 Ma) was
emplaced synchronously with the extrusive volcanic activity;
hornblendite cumulate in sodalite syenite revealed the age of
30.1 Ma.
5 dykes of coeval (30.925.6 Ma), Strongly and Weakly
Alkaline Series: camptonites/(gauteites I?) (30.928.2 Ma),
monchiquites (25.6 Ma), nepheline syenite porphyries proba-
bly forming cone sheets (30.1 Ma), tinguaite porphyries (25.6
Ma) and gauteites II? (23.6 Ma)/trachytes?
6 trachytic breccia with carbonate cement filling the
main Roztoky crater vent (caldera with pseudotrachyte filling
of Kopecký 1987) contains xenoliths of monzodiorite, lampro-
phyres etc.; however, it is intruded by felsic dyke rocks (dykes
and/or cone sheets tinguaite /porphyry/, trachyte, phonolite,
nepheline syenite porphyry); hydrothermal polymetallic ore
veins penetrating the Roztoky monzodiorite paralleled by bos-
tonite dyke and intersected by younger trachytes.
7 Uppermost Formation (flow/s/ of basanite) repre-
sents continued (partly overlapping the Upper Formation)
extrusive volcanic activity (24.0 Ma).
8 youngest intrusive volcanic activity in the RIC area is
represented by small stocks of nepheline phonolites (17.0 Ma;
No.
Rock type
Locality
Age (Ma)
Method
Source
54
Essexite dark, medium-grained, hbl-cpx
Lícha hill near Malé Bøezno
33.1
hornblende
this work
55
Essexite light, medium-grained, hbl-cpx
Lícha hill near Malé Bøezno
31.3
alkali feldspar
this work
14
Monzodiorite fine-grained, cpx-bi
Roztoky, railway cut
32.7
hornblende
this work
15
Monzodiorite medium-grained, cpx-bi
Roztoky, railway cut
29.5
whole rock
Bellon & Kopecký (1977)
16
Monzodiorite coarse-grained, bi-cpx
Roztoky, railway cut
30.8
hornblende
this work
4
Monzodiorite fine-grained, cpx-bi
Roztoky, railway cut
30.9
clinopyroxene
this work
4
Monzodiorite fine-grained, cpx-bi
Roztoky, railway cut
30.7
biotite
this work
3
Sodalite syenite fine-grained, hbl-cpx
Hraditì Hill near Svádov
28.0
whole rock
Arakelyanc et al. (1977)
59
Sodalite syenite fine-grained, hbl-cpx
Hraditì Hill near Svádov
28.6
analcime
this work
60
Sodalite syenite fine-grained, hbl-cpx
Giegelberg Hill, near Zubrnice, quarry
30.1
analcime
this work
115
Hornblendite coarse-grained, cumulate in sod. syenite
Giegelberg Hill, near Zubrnice, quarry
30.8
hornblende
this work
8
Camptonite with hbl+phl phenocrysts
Dobkovice, quarry
28.2
whole rock
Wilson et al. (1994)
11
Monchiquite with cpx phenocrysts
Dobkovice, quarry
25.6
whole rock
Wilson et al. (1994)
9
Camptonite with hbl+phl phenocrysts
Letina, quarry
30.9
whole rock
Wilson et al. (1994)
99
Gauteite II? with hbl-bi-plag phenocrysts
Tìchlovice, quarry
23.6
whole rock
Wilson et al. (1994)
152
Tinguaite porphyry porphyritic with ne-fsp phenocrysts
Skrytín, water-tower
25.6
magnetic fraction this work
13
Nepheline syenite porphyry coarse-grained
Roztoky, railway cut
30.1
light fraction
this work
195
Bostonite fine-grained
Malé Bøezno, borehole
38.6
whole rock
this work
98
Rhyolite coarse-grained to porphyritic
Malé Bøezno, borehole
43.4
whole rock
this work
19
Olivine nephelinite fine-grained
Dobkovice, quarry
29.3
whole rock
Wilson et al. (1994)
30
Olivine nephelinite fine-grained
Tìchlovice, quarry
30.9
whole rock
Wilson et al. (1994)
17
Tephrite fine-grained
Vysoký kámen Hill near Netìmice
27.1
whole rock
this work
96
Phonolite fine-grained, plg phenocrysts
Kozí hora Hill near Netìmice
42.7
whole rock
this work
24
Sodalite trachyte fine-grained
Radeín Hill near Radeín
29.8
whole rock
this work
ROZTOKY INTRUSIVE CENTRE: DIFFERENTIATION AND AGE OF DYKE SERIES 395
Shrbený & Vokurka 1985) and leucite tephrites (16.1 Ma; Pfe-
iffer et al. 1984 ) lying at transitions to the basanite Late Mi-
ocene Intrusive Formation (139 Ma) known from the Teplice
area, CSM (Ulrych et al. 1999; Cajz et al. 1999).
Discussion and conclusions
The RIC representing the main volcanic centre of the CSM
is structurally predisposed by the intersection of two main
tectono-volcanic structures of the Bohemian Massif (Ko-
pecký 1978). It belongs to characteristic volcanic structures
of central type. The ages of individual intrusive subvolcanic
rock types of the RIC fall within a narrow interval of 3324
Ma: (i) Hypabyssal Weakly Alkaline Series (33.128.2 Ma)
of plutonic intrusions emplaced synchronously with coeval,
(ii) Strongly and Weakly Alkaline Series (30.923.6 Ma) of
dykes and intruded by (iii) felsic dykes and cone sheets (<
23.6 Ma).
The proportions of dykes of the individual rock types IIV (I
lamprophyres, II semilamprophyres, III basaltic
rocks, IV felsic derivatives) indicate a pronounced domi-
nance of (semi)lamprophyres forming together 83 % of all
dykes. Lamprophyres represent potential parental magmas for
hypabyssal intrusions (cf. similar situation in Monteregian in-
trusions Bédard 1989).
87
Sr/
86
Sr and
143
Nd/
144
Nd ratios of
the lamprophyres (0.704050.70435; 0.512627) and hypabys-
sal essexiticsyenitic (0.704460.70363) rocks show the same
upper mantle source with minor crustal contamination (Ulrych
et al., in print) with tephrite/basanite (0.70310.70353;
0.5127380.512849) and trachybasalts (0.704430.70465;
0.5126790.512742) extrusions (Cajz et al. 1999 and Ulrych
et al. in print). Tephrite/basanite and trachybasalt dyke rocks
(6 % of dykes in the RIC) probably associated with the Upper
and Lower Formations sensu Cajz et al. (1999) do not belong
to the RIC proper. Rare augitite represents the most primitive
dyke derivative in the RIC (Jelínek et al. 1989). Minor felsic
derivatives (9 %) of trachyte, and phonolite composition form
Fig. 7. Age histograms for principal rock types (IIV) in the Roztoky Intrusive Centre. E essexite, MD monzodiorite, SS so-
dalite syenite, H hornblendite, M monchiquite, C camptonite, G gauteite, TiP tinguaite porphyry, NSP nepheline syen-
ite porphyry, Tr trachyte, Ba basanite, Tb trachybasalt, Bo bostonite I, Ph phonolite.
396 ULRYCH
and BALOGH
cone sheets and radial dykes representing the younger prod-
ucts of the RIC. Their age is presumably similar to that of
gauteites II? (24 Ma).
Statistical evaluation of the distribution of dyke rocks in
the RIC area indicates low frequency of dykes (25 %) at
distances of < 1 km, with the exception of felsic derivatives
(20 %); basaltic dykes are completely missing within this
distance. Frequency maxima (5155 %) of all dykes charac-
teristically occur at distances of 24 km. Substantial cumula-
tive frequency of dykes of all groups (9198 %; felsic deriva-
tives even 100 %) is in distance up to 7 km from the RIC.
This distance correlates with accumulations of sodalite syen-
ite bodies which according to Kopecký (1977), show signs of
ring-dyke arrangement. Dykes at distances of > 1520 km
(map sheet MìruniceTøebenice) can be hardly genetically
associated with the RIC and may be associated with a yet un-
specified volcanic centre near Zálezly. Other minor volcanic
centres with dyke suite are, e.g., the Býèkovice Intrusive
Centre, CSM (Ulrych & Novák 1989) with associated lam-
prophyre swarm of mostly linear character in the VinnéTøe-
buín Zone.
Strikes of radial dykes indicate that the main intrusive cen-
tre is present in the area between Roztoky and Malé Bøezno
with monzodioriteessexite intrusions with some marginal so-
dalite syenite intrusions, e.g. near Svádov. Dykes of sodalite
(semi)lamprophyres, sodalite bostonites II and sodalite basal-
tic rocks are spatially often associated with the sodalite syenite
bodies (cf. Hibsch 1926). Different strike maxima of the dykes
on the right and the left banks of the Labe River can be proba-
bly explained by the different representation of dykes of the
individual groups (IIV) having characteristic strikes on the
two Labe River banks. The right bank poses a relatively better
preserved, tectonically subsided block with a higher number of
dykes. For the interval of 3126 Ma, the analysis of dyke ge-
ometries indicates the dominance of regional stress character-
ized by the emplacement of EW-striking dykes. The oldest
BA dykes probably associated with the Lower Formation
basanitic lavas (3129 Ma) reveal, in addition to the prevailing
EW strike, also NS and NWSE strikes. The younger dykes
(3126 Ma) of groups L and SL are characterized by very sim-
ilar pattern of dyke distribution with marked preference of E
W-striking dykes and minor NS strikes. A substantially dif-
ferent pattern is characteristic for the youngest (2624 Ma) LD
dykes with prevailing NWSE strikes together with minor E
W, WNWESE and NNESSW strikes.
Acknowlegements: The preparation of the paper was partly
supported by Grant Project of Ministry of Culture CR under
Identification Code RK99P03OMG035 Mineralogy of the
Èeské støedohoøí Mts.. The K-Ar dating was supported by the
Hungarian Science Foundation Projects Nos. T014961 and
T029897. The research was covered by joint Hungarian
Czech Project Comparative volcanostratigraphy of the
Neoidic volcanism of the Bohemian Massif and the Pannonian
Basin. The authors are grateful to P. Kresten, Uppsala, P. Ra-
jlich, and J. Adamoviè, Institute of Geology AS CR, Praha and
Jaroslav Lexa, Slovak Geological Survey, Bratislava for their
stimulating comments on the manuscript and for a thoughtful
review.
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