GEOLOGICA CARPATHICA
, AUGUST 2018, 69, 4, 335–346
doi: 10.1515/geoca-2018-0020
www.geologicacarpathica.com
Cummingtonite-bearing volcanic rocks: first evidence
in the Central Slovak Volcanic Field
KATARÍNA ŠARINOVÁ
1,
and SAMUEL
RYBÁR
2
1
Department of Mineralogy and Petrology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina, Ilkovičova 6,
842 15 Bratislava, Slovakia;
sarinova@fns.uniba.sk
2
Department of Geology and Paleontology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina, Ilkovičova 6,
842 15 Bratislava, Slovakia
(Manuscript received August 30, 2017; accepted in revised form May 31, 2018)
Abstract: Within the framework of reinterpretation of the depositional evolution of the Komjatice depression, presence
of cummingtonite in weakly lithified sediment has been detected. The sediment is formed by volcanic lithoclasts and
phenocrysts with a small admixture of non-volcanic grains. The different mineral composition and various degrees of
alteration of volcanic lithoclasts, together with structural features point to epiclastic origin. Therefore, the studied
samples can be described as volcanic paraconglomerate and sandstone. The cummingtonite is found in rusty coloured
volcanic lithoclasts and in the heavy fraction. Cummingtonite-bearing volcanic rocks have not been described so far from
the Slovak Neogene volcanic fields. Therefore its presence in the studied samples represents the first indication of such
volcanic rock in Slovakia. The aim of the article is to invoke interest for finding these volcanic rocks in situ.
Keywords: cummingtonite, provenance, Komjatice depression, Danube Basin.
Introduction
The studied samples come from the Zlaté Moravce-1 well
(ZM-1). The ZM-1 well is situated in the NE part of the Kom-
jatice depression (Fig. 1; 48°22’25.75” N, 18°22’16.35” E)
and was drilled in 1968–1969 during hydrocarbon prospec-
tion. Today, new petrographical and sedimentological research
is taking place, with the aim of reinterpretation of the deposi-
tional history of the Danube Basin. On this occasion, Nafta
Petroleum Company provided all the archive well cores for
re-evaluation.
The Neogene marine sediments start at the depth of 1410–
1405 m of ZM-1 well. They consist of mudstone, sandstone,
volcanic conglomerate, volcanic-rich paraconglomerate to sand -
stone and bentonite layers (Šarinová et al. 2018). The objects of
this study are sandy conglomerates to sandstones from the depth
of 1005–1010 m and 1046–1051 m. These sediments were
originally assigned to the late Badenian (early Serravallian)
based on the Bul.-Bol. foraminiferal assemblages (Biela
1978). New biostratigraphic results assign the sediments from
the depth of 1410–1046 m (core 12) to NN6 Zone (late
Badenian–Sarmatian / Serravallian; Ozdínová 2012; Šarinová
et al. 2018). But well core 11 from the depth of 1010–1005 m
contains index Pannonian (Tortonian) fossils (Šarinová et al.
2018). Correlation of volcanic lithoclasts with their expected
provenance is significant for this paper. Coarse-grained vol-
canic conglomerates from the depths 1346–1351 and 1099–
1104 m are composed of sub-rounded pebbles to cobbles
of biotite–amphibole andesites ± Px, Qz with tuffaceous matrix
(Šarinová et al. 2018). The petrographic composition of
conglomerates, together with the age range of surroundings
sediments (NN6 Zone) allows the search for their provenance
in the Studenec Fm. In the original works, the Studenec Fm. is
formed by Bt–Amp andesite to dacite (SiO
2
57–68 %; Konečný
et al. 1998a; Chernyshev et al. 2013). The Studenec Fm.
forms the 3
th
evolutional stage of the Štiavnica stratovolcano
(e.g., Konečný et al. 1998a, 2001; Konečný & Lexa 2001;
Chernyshev et al. 2013). The presence of volcanic conglo-
merate and bentonite points to a dominance of the Štiavnica
stratovolcano provenance at the time of sedimentation of
the studied samples. High content of fresh amphibole in
the analysed samples has led to explicit research connected
with provenance analyses. In addition, fresh amphibole
allowed for indirect K–Ar dating of sediments by dating vol-
canic activity. The aim of the paper is to bring information
about the presence of cummingtonite-bearing volcanic litho-
clasts in Neogene sediments. However, the main aim is to
inspire volcanologists to discover their in situ occurrence
among rocks of the Štiavnica stratovolcano.
Occurrence of cummingtonite and hornblende together in
volcanic rocks has been described from a large number of
felsic volcanic rocks and tephras. Cummingtonite with horn-
blende, orthopyroxene and biotite were described in rhyolites
of the Okataina Volcanic Centre of New Zealand (Ewart &
Green 1971; Ewart et al. 1975; Nicholls et al. 1992; Smith et
al. 2005). Dacite Yn tephras of Mount St. Helens also contain
cummingtonite with plagioclase, hornblende, magnetite and
ilmenite in highly vesiculated microlite-free glass (Mullineaux
1986; Geschwind & Rutherford 1992). It was also described
from andesites of the Narcondam volcano in the Andaman Sea
336
ŠARINOVÁ and RYBÁR
GEOLOGICA CARPATHICA
, 2018, 69, 4, 335–346
Fig. 1. a — Generalized geological map of Slovakia; b — schematic geological map showing the localization of the Zlaté Moravce-1 well
(modified from the digital geological map of Slovakia, Káčer et al. 2013).
(Pal et al. 2007), from Iceland dacites at Króksfjördur volcano
(Pedersen & Hald 1982), dacites from Martinique (d’Arco et
al. 1981), Japan tephras (Matsu’ura et al. 2012) and other
places. Moreover, the cummingtonite-bearing tephras are
widely used in tephrostratigraphy (after Lowe & Hunt 2001),
because they form only a low percentage of tephras and so can
be used as correlation horizons (e.g., Matsu’ura et al. 2012).
This fact can also be used for provenance studies, for example,
of cummingtonite-bearing tephras connected with Mount
St. Helens (Smith & Leeman 1982; Mullineaux 1986).
Methods
For the documentation of sedimentary structures well cores
were cut in half, scanned and digitalized. Thin sections of well
cores were analysed under polarization microscope. Two sam-
ples from the depth of 1046–1051 m and one sample from the
depth of 1005–1010 m were used for heavy mineral analyses.
Samples were washed in water and sieved to the fraction
0.25–0.10 mm. Heavy minerals were separated using heavy
liquid and analysed under binocular microscope. Polished sec-
tions of heavy fraction and thin sections of studied sedimen-
tary rock were analysed using WDS analysis of microprobe
Cameca SX 100 (State Geological Institute of Dionýz Štúr),
accelerating voltage 15 keV, probe current 20 nA. Raw analy-
ses were recalculated to weight percent of oxide using ZAF
correction. Inclusions of melt and mineral inclusion were
determined by EDAX analyses. Only one melt inclusion was
large enough for WDS analysis. Amphiboles were calculated
after Hawthorne et al. (2012) using the Excel spreadsheet by
Locock (2014). Pyroxene was calculated on the base of 6 anions,
content of Fe
3+
was calculated from stoichiometry after Dropp
(1987). Plagioclase was calculated on the base of 8 anions.
Groundmass in rusty coloured volcanic lithoclasts was also
analysed. In this case, groundmass was replaced by secondary
minerals. Their analyses were normalized to 44 total cation
charges, to balance O
20
(OH)
4
and all Fe was considered as
Fe
3+
. Groundmass analyses of these lithoclasts must be taken
as informative, because the thin sections were not prepared
and measured with respect to clay minerals. Whole rock
chemical analysis of volcanic lithoclasts from Bt–Amp ande-
site (depth 1346–1351 m and 1099–1104 m) was done using
ICP-ES (major oxides) and ICP-MS (trace elements) in Bureau
Veritas mineral laboratories, Canada. Mineral abbreviations
follow Whitney & Evans (2010).
Results
The studied core samples from the depth of 1046–1051 m
(core 12) are typically rusty coloured and consist of two diffe-
rent lithological groups. The first is represented by poorly
sorted, sandy paraconglomerate (Fig. 2b, d) with occasionally
armoured mud intraclasts and indistinct synsedimentary folds.
The clasts populate the full spectrum of roundness from poorly
to well-rounded and reach up to 5 cm in diameter. Clasts are
mostly of volcanic origin, and are highly varied in colour, in
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CUMMINGTONITE-BEARING VOLCANIC ROCKS IN THE CENTRAL SLOVAK VOLCANIC FIELD
GEOLOGICA CARPATHICA
, 2018, 69, 4, 335–346
roundness and in the level of lithification. Some of these clasts
are highly altered and have a tendency to weather out and so
generate secondary porosity (Fig. 2b). The second group is
represented by sandstones and mudstones with abundant ero-
sional contacts, synsedimentary folds, faults and indistinct
ripples (Fig. 2c). The core samples from the depth of 1005–
1010 m (core 11) are very similar (Fig. 2a). But the content of
non-volcanic clasts is higher and the sediment is occasionally
better sorted. Matrix is less lithified.
In the depth 1046–1051 m, the gravel fraction (up to 2 mm)
is composed of volcanic lithoclasts and phenocrysts of idio-
morphic plagioclase. Non-volcanic admixture is present only
in samples with observed muddy intraclasts. In the sandy frac-
tion (2–0.06 mm) plagioclase phenocrysts together with vol-
canic lithoclasts strongly dominated, but quartz grains, heavy
minerals, mudstone and sandstone lithoclasts are also present.
Microscopic study of the thin sections documented idiomorphic
to hypidiomorphic plagioclase, biotite, brown-green amphi-
bole, pyroxene, poly- and monocrystalline quartz, opaque
grains and lithoclasts. Lithoclasts are represented by volcanic
rocks, but shale, sandstone and low grade Qz+Fs metasedi-
ments are also found together with foraminifera and mollusc
shells. Planimetry was not done, but the amount of quartz
grains and non-volcanic lithoclasts does not exceed ∼ 10 %.
Volcanic lithoclasts can be divided into two main types.
The first type is represented by sub-rounded to rounded,
lithified andesite clasts of greenish grey and light purple
colour (Fig. 2b). Their porphyritic texture consists of pheno-
crysts of plagioclase and mafic minerals, which are often fully
replaced by secondary minerals. However, large phenocrysts
of brown, opacitized amphibole and biotite are observed
(Fig. 3b), whereas quartz phenocrysts are rare. The first type
of volcanic lithoclast groundmass is microcrystalline and is
composed of K-feldspar, Pl and Qz. Rusty colouration is
typical for the second type of volcanic lithoclast (Fig. 2b, d).
The second type of lithoclast is porphyritic, rarely pilotaxitic
and consists of phenocrysts of plagioclase, brown-green
amphibole, biotite and pyroxene. Sometimes, pseudomorphs
filled by secondary minerals are present. The presence of fresh
pyroxene together with pyroxene shaped pseudomorphs in one
Fig. 2. Scanned well core samples: a —depth 1005 m, note the Bt–Amp andesite clast; b — depth 1046 m, note the rounded, andesite volcanic
lithoclasts (first type) and rusty coloured, friable volcanic lithoclasts (second type); c — depth 1047 m, fossiliferous sandstones with indistinct
ripples; d — depth 1051 m, the arrows point to rusty coloured volcanic clasts (second type).
338
ŠARINOVÁ and RYBÁR
GEOLOGICA CARPATHICA
, 2018, 69, 4, 335–346
Fig. 3. a — Rusty coloured volcanic lithoclasts (second type; depth of 1046–1051 m), PPL; b — the first type of volcanic lithoclasts (depth
1046–1051 m), PPL; c — thin section of studied sediment with marked position of analysed cummingtonite-bearing lithoclasts (depth
1046–1051 m), scan; d — clast no. 1 (see c), BSE; e — clast no. 2 (see c), BSE; f — clast no. 3, BSE; g — zonal pyroxene from the heavy
fraction, BSE; h — cummingtonite from the heavy fraction, BSE.
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CUMMINGTONITE-BEARING VOLCANIC ROCKS IN THE CENTRAL SLOVAK VOLCANIC FIELD
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clast indicates two pyroxene types, where more stable clino-
proxene is preserved and orthopyroxene is decomposed.
The second type is characterized by rusty coloured groundmass
of lithoclasts that is composed of secondary minerals. However,
part of these grains showed inhomogenity in the groundmass
colouration (Fig.3a). Association is completed by clasts com-
posed of vitroclasts and phenocrysts that are described as
vitro-crystalloclastic tuffs. These results are confirmed by
probe study of three rusty coloured volcanic lithoclasts of
the second type. The studied clast number 1 (Fig. 3c, d.) with
porphyritic texture and reddish colouration is composed of
phenocrysts of cummingtonite (Table 1), plagioclase, biotite,
apatite, titanomagnetite and ilmenite. Pl, Ilm, Ap and Ti-rich
Mag are also present as mineral inclusions in cummingtonite
phenocrysts (Fig. 3d). Plagioclase phenocrysts are zonal from
An
84
in the core to An
50
in the rim (Table 2, Fig. 4). The indica-
tive composition of the groundmass most closely corresponds
to the Fe
3+
-rich minerals of the smectite group (Table 1). Studied
lithoclast number 2 (Fig. 3c, e) consists of vitroclasts, litho-
clasts, plagioclase phenocrysts (An
73–50
; Table 2, Fig. 4),
magnesio-ferri-hornblende, cummingtonite (Table 1, Fig. 5),
biotite and ilmenite. The combination of phenocrysts, vitro-
clasts and lithoclasts in Si-rich microlitic matrix enable us to
classify the studied clast as a tuff. The analysed porphyritic,
rusty coloured volcanic clast number 3 is composed of
phenocrysts of zonal plagioclase (An
90–60
; Table 2, Fig. 4)
and pheno crysts of mafic minerals, that are fully replaced.
The chemical composition of its groundmass is the same as in
the clast 1 (Table 1), but some parts are not altered (Fig. 3f).
They are formed by microcrystals of quartz, K-feldspar and
Species
magnesio-ferri-hornblende
cummingtonite
groundmass
Clast no.
Clast 2
mineral grain
Clast 1
Clast 2
Clast 1
Clast 2
Clast 3
Anal.
6
17
7
24
1
2
3
4
5
18
16
23
36
SiO
2
46.81
47.12
46.94
46.10
53.01
53.61
52.41
53.31
52.53
53.34
SiO
2
50.63
87.02
49.44
TiO
2
1.00
1.15
1.31
1.14
0.33
0.23
0.36
0.26
0.34
0.27
TiO
2
0.15
0.09
0.12
Al
2
O
3
7.92
7.92
8.13
8.30
2.21
1.92
2.90
2.16
2.58
2.04
Al
2
O
3
8.60
6.40
8.60
Cr
2
O
3
0.03
0.01
0.00
0.00
0.00
0.00
0.00
0.01
0.00
0.03
Cr
2
O
3
0.02
0.04
0.02
MnO
0.40
0.33
0.31
0.50
0.70
0.73
0.78
0.79
0.77
0.81
MnO
0.24
0.02
0.24
FeO
16.85
15.45
16.32
17.32
22.44
23.18
23.63
22.38
22.53
21.74
FeO
17.04
1.66
15.85
NiO
0.00
0.02
0.00
0.03
0.01
0.00
0.00
0.00
0.00
0.01
NiO
0.00
0.01
0.01
MgO
12.23
12.76
12.18
11.73
16.89
16.77
15.89
16.88
16.18
17.23
MgO
12.66
1.26
11.52
CaO
10.02
10.42
10.62
10.28
1.48
1.02
1.24
1.66
1.85
1.58
CaO
2.31
0.38
2.65
Na
2
O
1.20
1.31
1.33
1.35
0.33
0.29
0.44
0.30
0.41
0.33
Na
2
O
0.31
0.46
0.22
K
2
O
0.36
0.42
0.53
0.42
0.01
0.00
0.01
0.00
0.01
0.00
K
2
O
0.33
1.37
0.32
F
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
F
0.00
0.00
0.00
Cl
0.13
0.12
0.16
0.14
0.05
0.04
0.03
0.04
0.04
0.03
Cl
0.06
0.02
0.12
Init. tot
96.91
96.99
97.78
97.27
97.44
97.79
97.67
97.78
97.24
97.40
Total
92.35
98.72
89.09
*FeO
12.81
11.40
12.55
12.59
21.85
23.00
22.87
21.89
21.81
21.24
Si
7.279
7.341
*Fe
2
O
3
4.49
4.50
4.19
5.26
0.65
0.21
0.84
0.55
0.80
0.56
Al
0.721
0.659
*H
2
O
+
2.01
2.02
2.00
2.00
2.05
2.04
2.04
2.05
2.04
2.06
T subtot
8.000
8.000
Tot.
99.37
99.46
100.20
99.80
99.56
99.85
99.80
99.88
99.36
99.52
Al
0.736
0.846
Si
6.918
6.920
6.882
6.815
7.760
7.833
7.694
7.777
7.724
7.789
Ti
0.016
0.013
Al
1.082
1.080
1.118
1.185
0.240
0.167
0.306
0.223
0.276
0.211
Fe
3+
1.366
1.312
Ti
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Mg
2.713
2.550
Fe
3+
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Mn
0.029
0.030
T subtot
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
Cr
0.002
0.002
Ti
0.111
0.127
0.144
0.127
0.036
0.025
0.039
0.029
0.037
0.029
Ni
0.000
0.001
Al
0.297
0.291
0.287
0.262
0.140
0.163
0.197
0.148
0.170
0.139
M subtot
4.863
4.753
Cr
0.004
0.001
0.000
0.000
0.000
0.001
0.000
0.001
0.000
0.004
Ca
0.355
0.421
Fe
3+
0.501
0.497
0.462
0.585
0.072
0.022
0.094
0.060
0.089
0.062
K
0.061
0.061
Ni
0.000
0.002
0.000
0.003
0.002
0.000
0.000
0.000
0.000
0.001
Na
0.088
0.064
Fe
2+
1.394
1.288
1.445
1.437
1.063
1.136
1.194
1.091
1.157
1.013
I subtot
0.504
0.546
Mg
2.693
2.794
2.662
2.585
3.686
3.653
3.477
3.670
3.547
3.752
C subtot
5.000
5.000
5.000
4.999
4.999
5.000
5.001
4.999
5.000
5.000
Mn
2+
0.050
0.041
0.039
0.062
0.087
0.090
0.096
0.097
0.096
0.100
Fe
2+
0.188
0.113
0.095
0.119
1.611
1.674
1.614
1.579
1.524
1.580
Ca
1.586
1.639
1.669
1.628
0.232
0.159
0.195
0.260
0.291
0.247
Na
0.176
0.207
0.198
0.190
0.070
0.076
0.095
0.064
0.089
0.072
B subtot
2.000
2.000
2.001
1.999
2.000
1.999
2.000
2.000
2.000
1.999
Na
0.167
0.166
0.179
0.195
0.024
0.007
0.031
0.020
0.029
0.020
K
0.067
0.079
0.099
0.079
0.002
0.000
0.001
0.000
0.003
0.000
A subtot
0.234
0.245
0.278
0.274
0.026
0.007
0.032
0.020
0.032
0.020
O
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
OH
1.967
1.971
1.960
1.965
1.989
1.990
1.992
1.989
1.990
1.992
F
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Cl
0.033
0.029
0.040
0.035
0.011
0.010
0.008
0.011
0.010
0.008
W subtot
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
Cat Sum
15.234
15.245
15.279
15.272
15.025
15.006
15.033
15.019
15.032
15.019
X
Fe
0.407
0.421
0.435
0.404
0.413
0.393
Table 1: The composition of amphiboles from volcanic lithoclasts and mineral grains, together with an indicative composition of groundmass
from volcanic lithoclasts (the thin section was not prepared with respect to clay mineral analysis); * values were calculated according to Locock
(2014), X
Fe
= Fe / (Fe + Mg + Mn + Ca).
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GEOLOGICA CARPATHICA
, 2018, 69, 4, 335–346
plagioclase (An
40
). With the exception of volcanic lithoclasts,
some mineral grains of plagioclase (An
85–51
) and amphibole
(Hbl) are also analysed (Tables 1, 2).
Samples from the depth 1005–1010 m show a very similar
composition (Fig. 2a). However, the content of non-volcanic
lithoclasts is higher (∼ 25 % in fraction up to 2 mm). Non-
volcanic lithoclasts are composed of quartz arenite, sandstone,
metasandstone, quartzite, chert, granitoid and polycrystalline
quartz. All previously described volcanic lithoclast types are
also present. Mineral grains are formed by quartz, amphibole,
biotite and plagioclase.
The heavy fractions from the depth of 1046–1051 m contain
mainly amphibole grains (50 %). Ilmenite together with
magnetite forms 36–44 %, pyrite, framboidal pyrite and limo-
nitized pyrite 2.5–6.9 %, apatite 2.5–2.8 %, and pyroxene
1.6 %. The association is supplemented with zircon, tourma-
line, rutile, titanite and garnet (less than 1 %). In the heavy
fraction from the depth of 1010–1005 m amphibole dominates
(79 %). Ilmenite together with magnetite forms 16 %,
pyrite, framboidal pyrite and limonitized pyrite form 2.7 %.
The amount of apatite, pyroxene, zircon, tourmaline, rutile,
titanite and garnet is less than 1 %. Such heavy mineral asso-
ciations are typical for a volcanic source area. Zircon and
tourmaline represented non-volcanic admixture, whereas
framboidal pyrite is an authigenic mineral, which indicates
a marine environment. During the study of heavy mineral
association under the binocular microscope two types of
amphiboles with different colour were distinguished.
Black coloured amphiboles (Hbl) dominated, whereas less
coloured and more transparent amphiboles (Cum) are less
frequent.
The composition of amphiboles from the heavy fraction is
consistent with previous results (Table 3, Fig. 5). From
the Ca-amphibole subgroup, magnesio-ferri-horblende and
minor magnesio-hastingsite are present. Inside the hornblende
grains, inclusions of melts, plagioclase, titanomagnetite and
apatite are observed. Melt inclusions show a rhyolite compo-
sition (Table 3). The Mg–Fe–Mn amphibole subgroup is
repre sented by cummingtonite. In cummingtonite grains no
mineral or melt inclusions have been observed (Fig. 3f). Both
amphibole subgroups are without zonality (Fig. 3h), but
the zonality of augite is determined (Fig. 3g). From core to rim
the Mg content slightly increases and the Fe content decreases
(Table 4). Marginal parts of augite are replaced by carbonate
(Fig. 3g).
Table 2: The composition of feldspar from volcanic lithoclasts and mineral grains; c — core, r — rim, phen — phenocrysts, matrix — micro-
crystals from groundmass of clasts (see Fig. 3f).
Location
Clast 1
Clast 2
Clast 3
Mineral grain
Anal.
10
11
12
13
15
19
20
21
22
30
31
33
35
25
26
Phen.
Phen.
Phen.
Phen.
Phen.
Phen.
Phen.
Phen.
Phen.
Phen.
Phen.
matrix
matrix
Phen.
Phen.
2c
2r
3c
3r
5
6
7c
7r
8
12c
12r
14
15
9c
9r
SiO
2
46.62
54.45
51.04
55.82
54.51
51.80
49.51
55.10
49.54
45.18
53.28
65.22
57.85
46.47
53.48
Al
2
O
3
33.21
28.18
30.76
27.32
28.24
30.08
31.78
27.67
31.11
34.78
29.47
20.40
27.53
33.70
28.83
SrO
0.10
0.09
0.10
0.11
0.07
0.05
0.07
0.12
0.07
0.08
0.07
0.08
0.07
FeO
0.50
0.42
0.22
0.35
0.65
0.48
0.29
0.21
0.27
0.24
0.29
0.30
0.64
0.29
0.32
MgO
0.00
0.00
0.00
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.04
0.01
0.00
BaO
0.80
0.06
CaO
17.24
11.10
13.99
10.30
11.02
13.35
14.97
10.59
14.61
18.50
12.35
0.56
8.34
17.55
12.11
Na
2
O
1.75
4.83
3.77
5.60
5.17
3.85
3.00
5.48
3.23
1.11
4.62
4.32
6.07
1.56
4.41
K
2
O
0.06
0.94
0.15
0.39
0.23
0.20
0.11
0.31
0.12
0.04
0.21
9.99
0.97
0.05
0.51
Tot.
99.46
100.02
100.05
99.89
99.89
99.81
99.74
99.48
98.96
99.93
100.28
101.59
101.52
99.69
99.73
Si
2.161
2.471
2.327
2.523
2.471
2.363
2.270
2.501
2.288
2.089
2.411
2.927
2.565
2.147
2.434
Al
1.814
1.507
1.653
1.455
1.509
1.617
1.717
1.481
1.693
1.895
1.572
1.079
1.439
1.835
1.546
Ti
0.003
0.002
0.003
0.003
0.002
0.001
0.002
0.003
0.002
0.002
0.002
0.000
0.000
0.002
0.002
Fe
0.019
0.016
0.009
0.013
0.025
0.018
0.011
0.008
0.011
0.009
0.011
0.011
0.024
0.011
0.012
Mg
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.003
0.000
0.000
Ba
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.014
0.001
0.000
0.000
Ca
0.856
0.540
0.684
0.499
0.535
0.652
0.735
0.515
0.723
0.917
0.599
0.027
0.396
0.869
0.590
Na
0.157
0.425
0.333
0.490
0.455
0.341
0.267
0.483
0.289
0.099
0.405
0.376
0.522
0.140
0.389
K
0.003
0.055
0.009
0.023
0.013
0.012
0.006
0.018
0.007
0.002
0.012
0.572
0.055
0.003
0.030
Cat sum
5.013
5.016
5.017
5.006
5.009
5.005
5.008
5.008
5.013
5.014
5.012
5.007
5.004
5.007
5.003
Or %
0.32
5.35
0.87
2.23
1.33
1.15
0.61
1.74
0.67
0.25
1.20
58.69
5.65
0.29
2.95
Ab %
15.46
41.71
32.50
48.47
45.32
33.91
26.46
47.54
28.37
9.75
39.87
38.53
53.65
13.82
38.58
An %
84.22
52.94
66.63
49.31
53.35
64.94
72.93
50.72
70.96
90.00
58.93
2.78
40.70
85.89
58.47
Fig. 4. Diagram of feldspar composition; * analyses taken from
Šarinová et al. (2018).
341
CUMMINGTONITE-BEARING VOLCANIC ROCKS IN THE CENTRAL SLOVAK VOLCANIC FIELD
GEOLOGICA CARPATHICA
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For interpretation of amphibole provenance, the composi-
tion of amphiboles from underlying volcanic conglomerates
(depths 1346–1351 m and 1099–1104 m) is also analysed. These
rocks mainly contain magnesio-hastingsite with weak zoning,
but some phenocrysts have magnesio-ferri-hornblende com-
position (Table 5, Fig. 5a). Whole rock chemical analyses of
lithoclasts were made to confirm the provenance of the Bt–Amp
andesite conglomerates in the Studenec Fm. (Table 6). Results
of analyses display andesitic composition, which is similar to
Bt–Amp andesite to dacite of the Studenec Fm. (Fig. 6).
Discusion
The association of cummingtonite, hornblende, hastingsite
and pyroxene was first observed in the heavy fraction. Rare
presence of hastingsite in heavy fraction can be explained by
reworking of underlying Bt–Amp andesite conglomerates (depth
1346–1351 m and 1099–1104 m; Table 5, Fig. 5), or by their
ongoing erosion in the source area. In the Bt–Amp andesite
hastingsite is present. Observed phenocrysts of brown amphi-
bole in the first type of studied lithoclasts clearly confirmed
this provenance (Fig. 3b). In the Bt–Amp andesite conglome-
rate, hastingsite phenocrysts are dominant and hornblende is
less frequent (Fig. 5a). But, in the studied samples the opposite
situation is observed. The large portion of hornblende with regard
to hastingsite in the studied samples, excludes the provenance
of hornblende strictly from underlying Bt-Amp andesite con-
glomerates. In addition, these conglomerates do not contain
cummingtonite. For this reason, the source of hornblende and
cummingtonite must be found in other volcanic rocks. This
result is supported by the presence of large, relatively fresh
phenocrysts of pyroxene. In the underlying Bt–Amp andesite
conglomerate pyroxene is rare and fully altered.
In the volcanic fields of Slovakia, cummingtonite-bearing
volcanic rocks have never been recorded. Cummingtonite was
described only from the KON-1 well (Javorie Mts.) as a pro-
duct of interaction between magma and Ca-silicate xenoliths
(Hraško et al. 2014) and from the reaction rim of pargasite in
rhyolites of the Strelníky Fm. (Kollárová 2010). These rare
occurrences of microcrystalline cummingtonite associated
with alterations and decay of primary minerals cannot
explain the presence of cummingtonite in the 0.25–0.10 mm
fraction. Cummingtonite was also described in metabasic
rocks (e.g., Faryad & Zábranský 1996; Janák et al. 2001).
However, there are no indications of metabasic rocks in
the petro graphic composition of the studied samples and
surrounding sediments (Šarinová et al. 2018). On the other
hand, detailed probe study of selected volcanic lithoclasts of
the second type (rusty colour) clearly demonstrated volcanic
origin of the cummingtonite phenocrysts (Fig. 3d). The calcu-
lated X
Fe
(Fe/(Fe+Mn+Mg+Ca) of cummingtonite is 0.43–0.39,
which is consistent with published data from cummingtonite
phenocrysts of volcanic origin (0.42–0.33; e.g., Evans &
Ghiorso 1995; Smith et al. 2005). The mineral association in
the studied sediments (plagioclase, pyroxene, hornblende,
cummingtonite, biotite and monocrystalline quartz) is also
consistent with the occurrence of cummingtonite-bearing vol-
canic rocks in the world (Ewart & Green 1971; Ewart et al.
1975; Mullineaux 1986; Nicholls et al. 1992; Geschwind &
Rutherford 1992; Smith et al. 2005; Pal et al. 2007; Fig. 7).
However, the co-occurrence of cummingtonite and hornblende
is documented only in tuff-type lithoclast (Fig. 3e). The com-
position of marginal parts of plagioclase phenocrysts (An
53–49
)
and microcrystalline matrix (An
40
) in volcanic lithoclasts
(second type) is typical for andesitic or dacitic volcanic rocks.
The content of An molecule and zonality of plagioclase pheno-
crysts are very similar to Pl phenocrysts in the under lying
Fig. 5. Amphibole classification diagrams (Hawthorne et al. 2012) shows amphiboles from studied samples and from underlying Bt–Amp
andesite conglomerate: a — the Ca amphibole subgroup; b — Mg–Fe–Mn amphibole subgroup. Note the composition of cummingtonite from
literature (Pedersen & Hald 1982; Smith & Leeman 1982; Oba & Micholls 1986; Pal et al. 2007; Matsu’ura et al. 2012 — average data).
342
ŠARINOVÁ and RYBÁR
GEOLOGICA CARPATHICA
, 2018, 69, 4, 335–346
Bt–Amp andesite conglomerate (Fig. 4). Based on this fact,
the provenance of cummingtonite from volcanic rocks of
rhyo litic composition can be excluded. Red or rusty colou ration
of volcanic lithoclasts of the second type is caused by repla-
cement of volcanic glass by Fe
3+
-rich clay minerals of
the smectite group (Table 1). They are a typical alteration
product of volcanic glass, where the source of Fe and Mg can
be found in the decay of mafic minerals (e.g., Treiman et al.
2014).
Similar mineral and textural composition of the well lithi-
fied volcanic rock of the first type (purple, greenish-grey)
relative to underlying volcanic conglomerate indicated their
older age. Reddish-brown coloured, cummingtonite-bearing
volcanic lithoclasts (type 2) are not present in underlying sedi-
ments and this points to their younger age. Rusty colouration
is typical for rapid cooling of volcanic clasts in oxidizing con-
ditions. If exposed to water, the degree of alteration of some
lithoclasts will cause their disintegration and washout. This
excludes redeposition in a marine environment after their
deposition and alteration. In addition, amphibole and pyro-
xene are unstable heavy minerals with rapid decay during
weathering, transportation and burial depth (e.g., Morton 1984;
Morton & Hallswort 1999; Andò et al. 2012). The presence of
fresh amphibole and pyroxene in mineral grains, as well as
inside the volcanic clasts, points to rapid sedimentation, short
transport and low burial depth. Based on these facts, rusty
coloured volcanic lithoclasts, fresh amphibole and pyroxene
phenocrysts can be considered syn-depositional. As is mentio-
ned earlier, the Bt–Amp andesite conglomerate (1346–1351 m
and 1099–1104 m) corresponds to the Studenec Fm. (3
rd
caldera
stage according to Konečný et al. 1998a; Konečný & Lexa
2001; Konečný et al. 2001). This is supported by similar
chemical composition of Bt–Amp lithoclasts and andesites of
the Studenec Fm. (Fig. 6). Therefore, cummingtonite-bearing
Table 3: The composition of selected amphiboles from heavy fraction; * values were calculated according to Locock (2014), X
Fe
= Fe/
(Fe+Mg+Mn+Ca)
Species
magnesio-ferri-hornblende
magnesio-hastingsite
cummingtonite
melt
Anal.
2
9
10
11
12
15
6
17
13
14
19
20
21
22
inclusion
SiO
2
46.22
44.95
45.07
46.25
45.43
46.38
42.73
42.91
52.35
52.56
53.30
52.59
53.53
53.02
73.75
TiO
2
0.86
1.13
1.85
1.22
1.38
1.03
1.75
1.66
0.33
0.26
0.21
0.34
0.21
0.25
0.10
Al
2
O
3
8.34
9.23
9.18
8.57
9.01
7.87
12.86
13.88
2.40
2.12
1.58
2.39
1.84
1.74
11.92
Cr
2
O
3
0.01
0.01
0.01
0.01
0.04
0.00
0.12
0.00
0.00
0.00
0.00
0.00
0.00
0.02
0.00
MnO
0.55
0.48
0.35
0.44
0.48
0.45
0.11
0.20
0.92
0.97
0.81
0.89
0.98
0.92
0.08
FeO
17.54
17.83
17.24
17.16
17.44
17.28
9.28
10.79
22.33
22.64
22.51
21.94
22.87
22.71
1.37
NiO
0.00
0.00
0.00
0.00
0.00
0.03
0.00
0.05
0.00
0.00
0.02
0.00
0.00
0.00
0.02
MgO
11.93
11.94
11.58
12.41
11.72
12.73
15.99
14.49
16.97
17.07
17.78
17.25
17.27
17.34
0.10
CaO
10.35
10.51
10.76
10.37
10.56
10.17
11.77
11.78
2.27
1.48
1.40
2.27
1.43
1.45
1.27
Na
2
O
1.22
1.27
1.40
1.33
1.30
1.19
2.13
1.94
0.43
0.33
0.20
0.35
0.26
0.21
2.09
K
2
O
0.38
0.49
0.54
0.45
0.54
0.35
0.45
0.53
0.05
0.00
0.00
0.04
0.00
0.00
3.05
F
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Cl
0.14
0.17
0.14
0.14
0.16
0.13
0.01
0.04
0.05
0.04
0.04
0.05
0.05
0.04
0.21
Init. tot
97.51
97.96
98.08
98.33
98.02
97.58
97.21
98.25
98.10
97.47
97.81
98.10
98.43
97.70
93.96
*FeO
12.03
10.71
12.83
11.55
12.00
11.23
3.81
6.05
20.17
21.24
21.18
20.05
22.00
21.51
*Fe
2
O
3
6.12
7.91
4.90
6.24
6.05
6.72
6.07
5.26
2.41
1.56
1.48
2.10
0.97
1.34
*H
2
O
+
2.00
1.99
1.99
2.00
1.99
2.01
2.08
2.06
2.04
2.04
2.05
2.04
2.04
2.04
Tot.
100.13
100.74
100.56
100.95
100.62
100.27
99.90
100.84
100.38
99.67
100.01
100.35
100.56
99.87
Si
6.805
6.592
6.636
6.743
6.674
6.801
6.146
6.150
7.622
7.701
7.761
7.641
7.769
7.748
Al
1.195
1.408
1.364
1.257
1.326
1.199
1.854
1.850
0.378
0.299
0.239
0.359
0.231
0.252
Sr
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Fe
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Mg
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
Ti
0.095
0.125
0.205
0.134
0.153
0.114
0.189
0.179
0.036
0.029
0.023
0.037
0.023
0.028
Al
0.252
0.188
0.228
0.216
0.234
0.160
0.326
0.493
0.034
0.067
0.032
0.050
0.084
0.047
Cr
0.002
0.001
0.001
0.001
0.005
0.000
0.014
0.000
0.000
0.000
0.000
0.000
0.000
0.002
Fe
3+
0.677
0.873
0.544
0.685
0.669
0.742
0.657
0.568
0.263
0.173
0.161
0.228
0.106
0.147
Ni
0.000
0.000
0.000
0.000
0.000
0.003
0.000
0.006
0.000
0.000
0.002
0.000
0.000
0.000
Fe
2+
1.355
1.202
1.480
1.268
1.374
1.199
0.385
0.660
0.984
1.002
0.926
0.949
1.051
0.999
Mg
2.619
2.611
2.541
2.697
2.566
2.783
3.429
3.094
3.683
3.728
3.858
3.736
3.735
3.777
C subtot
5.000
5.000
4.999
5.001
5.001
5.001
5.000
5.000
5.000
4.999
5.000
5.000
4.999
5.000
Mn
2+
0.068
0.060
0.044
0.055
0.059
0.056
0.013
0.025
0.113
0.121
0.100
0.109
0.120
0.114
Fe
2+
0.127
0.111
0.099
0.140
0.100
0.179
0.073
0.065
1.472
1.599
1.654
1.488
1.618
1.629
Ca
1.633
1.651
1.697
1.620
1.662
1.597
1.814
1.808
0.354
0.233
0.218
0.354
0.222
0.227
Na
0.172
0.178
0.161
0.185
0.179
0.167
0.099
0.102
0.060
0.047
0.028
0.049
0.040
0.029
B subtot
2.000
2.000
2.001
2.000
2.000
1.999
1.999
2.000
1.999
2.000
2.000
2.000
2.000
1.999
Na
0.176
0.182
0.238
0.190
0.192
0.171
0.496
0.438
0.060
0.047
0.028
0.049
0.035
0.029
K
0.071
0.091
0.102
0.083
0.101
0.066
0.082
0.096
0.009
0.000
0.000
0.007
0.000
0.001
A subtot
0.247
0.273
0.340
0.273
0.293
0.237
0.578
0.534
0.069
0.047
0.028
0.056
0.035
0.030
O
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
OH
1.965
1.958
1.966
1.964
1.960
1.969
1.997
1.990
1.987
1.989
1.990
1.987
1.989
1.989
F
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Cl
0.035
0.042
0.034
0.036
0.040
0.031
0.003
0.010
0.013
0.011
0.010
0.013
0.011
0.011
W subtot
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
Cat Sum
15.247
15.273
15.34
15.274
15.294
15.237
15.577
15.534
15.068
15.046
15.028
15.056
15.034
15.029
X
Fe
0.396
0.405
0.396
0.388
0.405
0.403
343
CUMMINGTONITE-BEARING VOLCANIC ROCKS IN THE CENTRAL SLOVAK VOLCANIC FIELD
GEOLOGICA CARPATHICA
, 2018, 69, 4, 335–346
volcanic lithoclasts should be connected with subsequent vol-
canic activity. The age range of the 4
th
evolutionary stage of
the Štiavnica stratovolcano is 12.7 to 12.2 Ma (Chernyshev et
al. 2013). This is consistent with biostratigraphic data from
the studied samples (NN6 Zone, depth 1046–1051 m; Šarinová
et al. 2018). The 4
th
post-caldera stage is represented by Obyce,
Ladzany, Baďany, Biely Kameň, Drastvica, Priesil, Inovec
fms. and by the Humenica, Sitno, Žiar, Jabloňový vrch,
Breznica complexes (Konečný et al. 1998a). However, a lot of
these formations and complexes are composed of pyroxene
andesites. The Ladzany, Biely Kameň and Drastvica fms. are
formed by Px–Bt–Amp dacites to andesites, but the Ladzany
Fm. is only found in the southern parts of the stratovolcano
(Konečný et al. 1998a, b). In addition, experimental works
(Oba & Nicholls 1986; Geschwind & Rutherford 1992;
Table 4: The composition of selected pyroxene from heavy fraction
of Zm-1 well (depth 1005–1010 and 1046–1051 m).
grain
1 core
1 rim
2
3
SiO
2
50.92
48.80
50.63
50.85
TiO
2
0.39
0.74
0.67
0.71
Al
2
O
3
1.73
4.48
2.34
2.56
Cr
2
O
3
0.02
0.37
0.02
0.03
FeO
7.72
1.89
9.10
7.87
Fe
2
O
3
3.30
4.87
2.59
3.48
MgO
14.00
15.80
13.98
14.94
MnO
0.38
0.19
0.32
0.37
CaO
20.96
21.43
19.56
19.58
Na
2
O
0.29
0.29
0.37
0.32
Total
99.71
98.86
99.59
100.69
Si
1.914
1.817
1.906
1.887
Al
0.077
0.183
0.094
0.112
Fe
3+
0.009
0.000
0.000
0.001
subtot T
2.000
2.000
2.000
2.000
Al
0.000
0.014
0.010
0.000
Fe
3+
0.093
0.137
0.073
0.097
Ti
0.011
0.021
0.019
0.020
Cr
0.001
0.011
0.001
0.001
Mg
0.784
0.818
0.785
0.826
Fe
2+
0.111
0.000
0.112
0.056
subtot M1
1.000
1.000
1.000
1.000
Mg
2+
0.000
0.059
0.000
0.000
Fe
2+
0.132
0.059
0.174
0.188
Mn
0.012
0.006
0.010
0.011
Ca
0.844
0.855
0.789
0.779
Na
0.021
0.021
0.027
0.023
subtot M2
1.010
1.001
1.001
1.002
depth
1099–1104 m
1346–1351 m
species
magnesio-hastingsite to ferri-sadanagaite
magnesio-hastingsite
magnesio-ferri-hornblende
grain
1
2
3
1
2
3
4 core
4 rim
5
6
7
SiO
2
42.29
42.38
41.87
41.92
42.33
41.95
43.27
43.80
42.92
44.63
46.50
TiO
2
2.52
2.34
2.36
2.06
2.36
2.06
2.44
2.37
2.44
1.61
1.13
Al
2
O
3
13.18
13.59
13.14
12.04
13.19
13.57
11.18
12.25
13.18
9.10
7.67
Cr
2
O
3
0.00
0.04
0.00
0.02
0.04
0.02
0.01
0.04
0.00
0.01
0.02
MnO
0.14
0.12
0.16
0.28
0.15
0.17
0.20
0.21
0.16
0.43
0.52
FeO
10.64
10.18
11.39
13.88
11.43
12.29
14.24
11.06
10.96
18.15
17.56
NiO
0.00
0.00
0.00
0.03
0.00
0.02
0.04
0.02
0.00
0.01
0.01
MgO
15.39
15.17
14.74
12.98
14.28
14.08
13.15
15.51
15.07
11.74
12.30
CaO
11.32
11.36
11.12
11.06
11.65
11.61
11.58
11.63
11.89
10.95
10.55
Na
2
O
2.33
2.17
2.08
3.28
2.23
2.05
2.00
2.10
2.06
1.46
1.79
K
2
O
0.47
0.54
0.63
0.55
0.52
0.59
0.54
0.54
0.58
0.61
0.36
F
0.00
0.00
0.00
0.93
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Cl
0.03
0.02
0.03
0.08
0.03
0.03
0.05
0.04
0.03
0.16
0.13
Init. Tot
98.30
97.93
97.51
98.70
98.21
98.44
98.69
99.56
99.29
98.81
98.52
*FeO
5.01
5.24
5.36
10.85
7.27
6.43
10.09
5.78
5.98
11.92
12.68
*Fe
2
O
3
6.26
5.50
6.69
3.36
4.63
6.51
4.60
5.88
5.54
6.92
5.43
*H
2
O
+
2.07
2.07
2.06
1.56
2.05
2.05
2.02
2.06
2.06
1.98
1.99
Total
101.00
100.55
100.24
100.60
100.72
101.15
101.17
102.21
101.90
101.48
101.05
Si
6.054
6.081
6.056
6.176
6.113
6.042
6.294
6.200
6.102
6.539
6.809
Al
1.946
1.919
1.944
1.824
1.887
1.958
1.706
1.800
1.898
1.461
1.191
T subtot
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
8.000
Ti
0.271
0.253
0.257
0.228
0.256
0.223
0.266
0.252
0.261
0.177
0.124
Al
0.278
0.379
0.297
0.267
0.358
0.345
0.210
0.243
0.310
0.110
0.133
Cr
0.000
0.004
0.000
0.002
0.004
0.003
0.001
0.005
0.000
0.002
0.003
Fe
3+
0.673
0.594
0.729
0.373
0.502
0.706
0.505
0.626
0.593
0.762
0.597
Ni
0.000
0.000
0.001
0.003
0.001
0.002
0.005
0.003
0.000
0.001
0.001
Fe
2+
0.494
0.524
0.539
1.276
0.804
0.698
1.160
0.597
0.642
1.383
1.457
Mg
3.283
3.245
3.178
2.850
3.075
3.024
2.852
3.274
3.194
2.565
2.685
C subtot
4.999
4.999
5.001
4.999
5.000
5.001
4.999
5.000
5.000
5.000
5.000
Mn
2+
0.017
0.015
0.020
0.035
0.018
0.021
0.024
0.025
0.020
0.053
0.065
Fe
2+
0.107
0.104
0.110
0.061
0.075
0.076
0.067
0.086
0.069
0.079
0.097
Ca
1.737
1.747
1.724
1.746
1.803
1.792
1.805
1.763
1.811
1.719
1.656
Na
0.140
0.134
0.147
0.158
0.105
0.111
0.104
0.126
0.101
0.149
0.182
B subtot
2.001
2.000
2.001
2.000
2.001
2.000
2.000
2.000
2.001
2.000
2.000
Na
0.506
0.471
0.437
0.780
0.519
0.462
0.460
0.451
0.468
0.267
0.325
K
0.086
0.099
0.116
0.103
0.096
0.109
0.101
0.097
0.105
0.114
0.067
A subtot
0.592
0.570
0.553
0.883
0.615
0.571
0.561
0.548
0.573
0.381
0.392
O
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
22.000
OH
1.993
1.996
1.992
1.546
1.992
1.992
1.988
1.990
1.992
1.960
1.967
F
0.000
0.000
0.000
0.434
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Cl
0.007
0.004
0.008
0.019
0.008
0.008
0.012
0.010
0.008
0.040
0.033
W subtot
2.000
2.000
2.000
1.999
2.000
2.000
2.000
2.000
2.000
2.000
2.000
Cat sum
15.592
15.569
15.555
15.882
15.616
15.572
15.560
15.548
15.574
15.381
15.392
Table 5: The composition of amphiboles from Bt–Amp andesite to dacite conglomerate; * values were calculated according to Locock (2014).
344
ŠARINOVÁ and RYBÁR
GEOLOGICA CARPATHICA
, 2018, 69, 4, 335–346
Nicholls et al. 1992; Evans & Ghiorso 1995) suggest that
the full temperature range of cummingtonite (volcanic & meta-
morphic) is ca. 400–800 °C. High water-pressure storage is
also necessary. The presence of cummingtonite in volcanic
rocks is connected with temperature between 700–840 °C,
P ˂ 300 MPa, conditions close to water saturation and shallow
magma chamber (Geschwind & Rutherford 1992; Smith et al.
2005). High water saturation is connected with explosive vol-
canism. From this point of view, Drastvica Fm. is the most
likely source of cummingtonite-bearing lithoclasts. This for-
mation consists of products of amphibole-rich explosive vol-
canism (ignimbrite and pumice tuff of Px–Amp ande site + Bt;
Konečný et al. 1998a) and overlies the Studenec Fm. Both
formations are in close proximity to the ZM-1 well (Konečný
et al. 1998b). The presented results from the studied sam-
ples are consistent with these data. On the other hand,
the Priesil Fm. is composed of Amp–Px andesites with variable
colouration. In this case, the Px versus Amp ratio is in favour
of Px (Konečný et al. 1998a). But this is not consistent with
results from the studied samples, where amphibole dominated.
However, this hypothesis must be confirmed in the future.
The fact, that cummingtonite-bearing volcanic rocks have not
yet been described in the Štiavnica volcanic field may also be
explained by their complete erosion.
The depositional mechanism of the studied samples can be
deduced from textural features and petrographical composi-
tion, but the core samples do not allow a clear interpretation.
Poor sorting, together with variable roundness of lithoclasts,
presence of calcareous fossils, framboidal pyrite, synsedimen-
tary folds, slumps and erosional surfaces indicated deposition
by sediment gravity flows in a marine environment. Crystal
shape of mineral grains and presence of unstable heavy mine-
rals also indicates short transport. The epiclastic origin can be
deduced from mixing of non-volcanic and volcanic grains of
various ages, from roundness of clasts, by presence of mud
intraclasts and fossils. Welding and other thermal effects typi-
cal for hot pyroclastic flows are not observed. Well sorted
sandstones with indistinct ripples are rare and present only on
small portions of the well core. Their deposition can therefore
be explained by traction as well as by turbiditic transport.
Either way, their epiclastic origin is indisputable and so trans-
port by pyroclastic flows can be excluded. In this point of
view, a delta front environment (delta slope morphology)
influenced by volcanic activity is assumed. Sizes of friable,
rusty coloured volcanic fragments (up to 1 cm in diameter)
and epiclastic origin of the studied samples may point to depo-
sition in the middle or distal zone of the volcanic centre. Non-
volcanic admixture is similar to that in underlying sediments
and points to their recycling.
Table 6: Whole rock chemical composition of lithoclasts from Bt–Amp andesite conglomerates; ZM-1/18: depth 1346–1351 m; ZM-1/13:
1099–1104 m; n.d. — under detection limit.
SiO
2
Al
2
O
3
Fe
2
O
3
MgO CaO Na
2
O K
2
O
TiO
2
P
2
O
5
MnO Cr
2
O
3
LOI
sum
Ctot
Zr
Nb
Rb
Sr
Ta
sample
wt. % wt. % wt. % wt. % wt. % wt. % wt. % wt. % wt. % wt. % wt. %
%
%
%
ppm
ppm
ppm
ppm
ppm
ZM-1/18
59.27 17.21
6.17
2.42
5.81
3.13
2.34
0.64
0.18
0.14
n.d.
2.5
99.81
0.17
132.4
14.4
106.8 105.7
1.4
ZM-1/13
58.28 17.33
6.94
2.73
5.75
3.27
2.32
0.65
0.19
0.09
0.002
2.3
99.85
0.21
109.9
13.1
76.5 346.8
0.8
Th
U
Ga
Hf
Y
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
sample
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ZM-1/18
18.2
4.1
14.8
4.3
17.7
34.3
56.5
6.43
20.9
3.76
0.70
3.45
0.54
3.15
0.64
1.97
0.31
2.18
0.33
ZM-1/13
9.8
2.4
15.0
2.9
16.8
28.1
51.9
5.52
19.3
3.53
0.96
3.34
0.53
3.10
0.61
1.91
0.28
1.82
0.29
Fig. 6. Comparison of chemical compositions of Bt-Amp andesite
lithoclasts (depth 1346–1351 m and 1099–1104 m, ZM-1 well) with
data from the Studenec Fm. (Lexa et al. 1997 in Konečný et al. 1998a).
Fig. 7. Ca–Mg–Fe diagram to illustrate the relationship of amphibole
(Hbl and Cum) from the studied samples (1005–1051 m). For com-
parison, the composition of amphibole from Yn tephra of Mount St.
Helens is displayed (data from Smith & Leeman 1982; Geschwind &
Rutherford 1992).
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CUMMINGTONITE-BEARING VOLCANIC ROCKS IN THE CENTRAL SLOVAK VOLCANIC FIELD
GEOLOGICA CARPATHICA
, 2018, 69, 4, 335–346
On the other hand, presence of different, Pannonian
(Tortonian) fossil assemblages in samples from the depth of
1005–1010 m (Šarinová et al. 2018) indicate reworking of
sedi ments from the depth of 1046–1051 m. This is confirmed
by increase of roundness and admixture of non-volcanic
grains. In this depth interval, strongly altered volcanic litho-
clasts of the second type (which produce secondary pore
space) are not present. The redeposition can be linked to sea
level change or to the wide rifting of the Danube Basin in the
Sarmatian–Panonian (Serravallian–Tortonian) stage (e.g.,
Kováč et al. 2017).
Conclusion
The observed mineral association: plagioclase, cumming-
tonite, hornblende and pyroxene, is typical for cumming-
tonite-bearing volcanic rocks for localities all around the world.
The presence of cummingtonite phenocrysts in volcanic litho-
clasts clearly documents its volcanic origin. Based on the suc-
cession of volcanic rocks and biostratigraphic ranking of
sediments (Šarinová et al. 2018), the cummingtonite-bearing
lithoclasts are derived from formations of the 4
th
evolutionary
stage of the Štiavnica stratovolcano (Konečný et al. 1998a, b;
Chernyshev et al. 2013). The Drastvica Fm. corresponds well
to the conditions for production of cummingtonite-bearing
volcanic rocks, as well as to the observed mineral association
and geological structure of the studied area. Finding of paren-
tal rocks of such volcanic lithoclasts will be important for
future study of the Štiavnica stratovolcano evolution, likewise
for provenance analysis and indirect dating of sediments.
Acknowlegements: This research was supported by the Slovak
research and development agency under the contracts No.
APVV-0099-11, APVV-15-0575 & APVV-16-0121. Our
special thanks go to Nafta Petroleum Company management
for allowing access to their well core repository. We express
our gratitude to the editor and to the reviewers for their
insightful comments which improved the manuscript.
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