GEOLOGICA CARPATHICA, 51, 6, BRATISLAVA, DECEMBER 2000
407412
GEOLOGICAL CONDITIONS AND ROCK RADIOACTIVITY
IN THE SPELEOTHERAPY MEDICAL FACILITY
IN THE ZLATÉ HORY ORE DISTRICT (THE CZECH REPUBLIC)
JIØÍ ZIMÁK
1
and JINDØICH TELCL
2
1
Department of Geology, Faculty of Science,
Palacký University, Tø. Svobody 26, 771 46 Olomouc, Czech Republic
2
Dept. of Mineralogy, Petrology and Geochemistry, Faculty of Science, Masaryk University, Kotláøská 2, 611 37 Brno, Czech Republic
(Manuscript received February 25, 2000; accepted in revised form October 17, 2000)
Abstract: An abandoned mine located in the Zlaté Hory ore district is now used for speleotherapy. A detailed petro-
graphical study along with extensive gamma-ray spectrometry measuring concentrations of naturally occurring ra-
dioactive elements (K, U and Th) was conducted in the mine in order to analyze the interrelationship between modal
composition and radioactivity of the rocks. Authors warn of a potentially higher concentrations of
222
Rn in the subsur-
face atmosphere of the speleotherapeutic medical facility.
Key words: Zlaté Hory ore district, speleotherapy, petrography, natural radioactive elements.
Introduction
The childrens speleotherapy medical facility in Zlaté Hory
is located in one of the abandoned mines of the Zlaté Hory
ore district. It is the Czech Republics only speleotherapy
medical facility apart from those situated in natural karst
caves shaped in carbonate rocks or adits excavated in such
rocks. Whereas carbonate rocks generally register low radio-
activity (e.g. Solecki 1997), non-carbonate rocks in aban-
doned mines may contain an increased amount of naturally
occurring radioactive elements. In these cases, their in-
creased radioactivity represents a potentially significant
health risk both to the staff and to the patients, which inevita-
bly reduces time spent in the mine. Due to this possible
health hazard, Zlaté Horys medical facility was evaluated
for potentially harmful levels of radioactivity.
Short characteristics of the Zlaté Hory ore district
The Zlaté Hory ore district is situated in the northern part
of the Jeseníky Mts., close to the Czech-Polish border. From
the geological point of view, the ore district is situated in the
NE part of the Bohemian Massif, within the Vrbno Group
a volcanic-sedimentary formation of Devonian age that was
epizonally to mesozonally metamorphosed during the
Variscan orogeny (e.g. Souèek 1978). Individual orebodies of
the Zlaté Hory ore district are situated predominantly in
quartzites and/or quartz keratophyres (paleorhyolites and
their tuffs) or near the contact of such rocks with underlying
or overlying pelitic schists. The ore minerals (mainly pyrite,
chalcopyrite, sphalerite, galena and pyrrhotite) form either
parallel streaks and bands within stratiform orebodies, gener-
ally parallel with schistosity of the host-rock, or form dis-
seminated to locally massive accumulations. The ore which
is composed mainly of chalcopyrite and pyrrhotite has been
partially remobilized from stratiform layers to form veiny
orebodies. In the western part of the Zlaté Hory ore district
the sulphide ore contains a considerably high concentration
of gold.
Apart from panning for gold in the alluvial deposits as well
as mining of gold of hydrothermal and also cementary origin
since the 13th century (lumps of gold weighing up to 1.7 kg
were found in placers north of the primary deposits in the
16th century), sulphides were also occasionally dug in the
19th century.
From 1965 till 1993, the ores were intensively mined at the
deposits of Zlaté Hory-South (Cu-ores), Zlaté Hory-Kozlín
(Cu-ores), Zlaté Hory-Hornické skály (Cu-ores), Zlaté Hory-
East (Pb, Zn-ores) and Zlaté Hory-West (Zn, Au-ores).
More details on the geology, petrography, ores and mining
history of the Zlaté Hory ore district can be found in papers
by Bernard (1991), Constantinides & Pertold (1974), Èabla
et al. (1979), Fediuk et al. (1974), Fiera & Souèek (1974),
Kalenda & Grygar (1993), Patoèka (1987a), Patoèka & Vrba
(1989). The natural conditions of the Zlaté Hory speleothera-
py medical institution were described by Sas et al. (1998),
telcl & Zimák (1998), Zimák & telcl (1999).
Though the Zlaté Hory ore district has been studied thor-
oughly with respect to its economic importance, only a little
data on Th and U concentrations in the local rocks is available.
From 69 samples of the Zlaté Hory pelitic schists (muscovite,
biotite and quartzose schists) taken from a single deep bore-
hole, the average contents of Th and U were 7.2 ppm and 1.7
ppm respectively (see Patoèka 1987b, 1988). In the aforesaid
papers the concentrations of both elements were determined
by INAA located in the Central Laboratories of the Czechoslo-
vak Uranium Industry in Strá pod Ralskem.
408 ZIMÁK and TELCL
Petrography and rock radioactivity of the
speleotherapy institution
The Zlaté Hory speleotherapy medical facility is situated
in an adapted part of the 2nd level of the Zlaté Hory-South
ore deposit, which is accessible through an adit 700 m long.
The speleotherapy medical facility is divided into eight sec-
tors marked with Roman letters from A to H (see Fig. 1a,
only the terminal part of the entrance adit is figured) as fol-
lows: A = active part (reserved for active physical training of
patients); B = classroom and nurses quarters; C = bedroom
ward; D, E, F and G = corridors; H = entrance adit. The pa-
tients enter the speleotherapy institution through the entrance
adit (sector H) and then move around the sectors A, B, C, E
and F. (Patients are billeted in sectors A, B and C.)
Two major rock groups can be discerned within the speleo-
therapy facility: (1) quartzites (so-called massive quartz-
ites), in places passing gradually into muscovite quartzites
and chlorite quartzites, (2) chlorite-muscovite schists and
muscovite schists (often quartzose or rich in carbonate), that
appear below and above the quartzite horizon on the 2nd lev-
el of the Zlaté Hory-South ore deposit (see Fig. 1b).
The light-grey coloured quartzites have microscopically
indistinct foliation planes. The quartzites have granoblastic
texture; only locally those parts with a higher proportion of
sheet silicates pass gradually into lepidogranoblastic texture.
The sheet silicates comprise mainly muscovite, in places to-
gether with chlorite (see Table 1). Acid plagioclase and bari-
um feldspar (celsian?) are present in accessory proportion.
Typical accessory minerals include rutile and leucoxene
(which, in some cases evidently originated from ilmenite al-
teration). Zircon is scarce. Opaque constituents comprise sul-
phides (mainly pyrrhotite and pyrite) and rarely also il-
menite.
Most often the schists are grey to green-grey, dark-grey to
almost black in colour. The schists have a distinct planar-par-
allel fabric. Locally, especially the dark-grey to black (gra-
phitic) schists are highly disaggregated (which was the rea-
son for lagging of large sections of the entrance adit).
The schists have lepidogranoblastic or lepidoblastic tex-
ture. They are distinctly banded: light coloured bands with
predominance of quartz alternate with darker bands with a
considerable proportion of sheet silicates comprising espe-
cially muscovite and in some parts also chlorite which may
infrequently predominate over the muscovite (see Table 1).
Carbonate is present in variable proportions in the schists,
causing the schists to pass gradually into marbles rich in non-
carbonate minerals (sample 307). The schists contain small
amount of acid plagioclase (probably albite). Rutile is
present in particular in the muscovite-rich bands. Opaque
constituents comprise mainly pyrite and pyrrhotite. Graphitic
substance has been found in some samples. Whereas in sam-
ples 210 and 212 the percentage of graphitic substance varies
between 1 and 3, it reaches an anomalous value in sample
232 (up to about 10 vol. %). With increasing percentage of
quartz the schists pass into quartzose schists and in places
even to quartzites that create up to several dm thick layers
within the schists.
Concentrations of natural radioactive elements (potassium,
uranium and thorium) were measured in the subsurface of the
Fig. 1. a Ground plan of the speleotherapy medical institution. b Schematic geological map of the 2
nd
level of the Zlaté Hory-South
ore deposit including the area of the speleotherapy medical institution (after Janák & Augusta 1969 and Janák 1970). 1 quartzites with
very small contents of muscovite and/or chlorite (massive quartzites), 2 quartzites rich in muscovite and/or chlorite, 3 chlorite-
muscovite schists and muscovite schists (mainly quartzose).
409
GEOLOGICAL CONDITIONS AND ROCK RADIOACTIVITY IN SPELEOTHERAPY MEDICAL FACILITY
speleotherapy medical facility proper and in the entrance adit.
A field gamma-ray spectrometer GS-256 manufactured by
Geofyzika Brno, Czech Republic was used. Measurements to-
talling 264 points are summarized in Table 2.
Since various natural elements contribute in various pro-
portions to the total gamma-ray activity of rocks (besides the
sum of their concentrations a mutual ratio of particular con-
centrations is of essential importance, too) the K, U and Th
concentrations were converted to mass activity of
226
Ra
equivalent (a
m
) in order to present the gamma-ray activity of
the locality in question see Table 2 and Fig. 2. Conversion
coefficients commensurate with the UNSCEAR recommen-
dation from 1996 were used to calculate the a
m
value (the ra-
dium equivalent mass activity):
1 % K in rock = 313.00 Bq . kg
1 40
K
1 ppm U in rock = 12.35 Bq . kg
1 226
Ra
1 ppm Th in rock = 4.06 Bq . kg
1 232
Th
Radium equivalent mass activity was calculated using the
following formula (U and Th contents are indicated in ppm,
K content is indicated in wt. %):
a
m
= 12.35U + (1.43
×
4.06Th) + (0.077
×
313K).
Radium equivalent mass activity allows the evaluation of
potential risks of a given environment with respect to rock ra-
dioactivity in a more objective way. Average values a
m
for the
individual sectors vary between 80 and 222 Bq.kg
1
. Our mea-
surements suggest that values of about 200 Bq.kg
1
can be
considered as anomalous (in the studied area). Such values
have been measured mainly in sectors B and H, therefore, de-
tailed petrographie evaluations were done only there (see
above). Evidently, the elevated concentrations of natural radio-
active elements (and, consequently, relatively high values of
a
m
) are spatially related to those rocks containing a high pro-
portion of sheet silicates, as evidenced in parts of sector B. Lo-
cally elevated concentrations of the monitored elements in
quartzites may be connected with hydrothermal alteration
(higher contents of U and Th were noted in places with fre-
quent occurrence of quartz veins, but not always).
The distribution of K, U and Th contents and radium equiv-
alent mass activity (a
m
) in the area of the speleotherapy medi-
Sample No.
78
302
254
257
261
303
82
201
210
83
232
212
204
238
307
Quartz
86.75
77.60
84.35
94.15
85.40
25.65
27.00
37.75
45.10
55.40
15.35
56.60
23.80
44.60
37.50
Muscovite
1.60
2.65
5.20
5.25
13.20
56.45
36.60
17.95
26.25
31.60
72.15
13.60
45.70
17.05
6.40
Chlorite
6.65
-
0.50
-
-
2.80
-
1.00
-
8.20
2.95
-
11.45
30.20
-
Carbonate
0.05
1.75
0.15
-
-
0.25
28.20
41.05
25.05
2.05
0.50
9.05
13.10
0.15
55.65
Acid plg.
-
-
-
-
0.20
-
-
1.15
-
-
-
-
-
-
-
Ba-feld spar
-
-
0.30
-
-
-
-
-
-
-
-
-
-
-
-
Opaque
4.60
18.00
8.75
0.45
0.85
14.10
6.25
0.45
3.35
1.40
7.35
17.05
2.85
5.60
0.40
Rutile
0.35
-
0.75
0.15
0.35
0.75
1.95
0.65
0.25
1.35
1.70
0.05
3.10
2.40
0.05
Limonite
-
-
-
-
-
-
-
-
-
-
-
3.65
-
-
-
Table 1: Modal compositions of rocks (in vol. %) in the sectors B (Samples Nos. 78, 82, 83, 302, 303 and 307) and H (Samples Nos. 201,
204, 210, 212, 232, 238, 254, 257 and 261) 78, 302, 254 and 257 quartzites; 261 muscovite quartzite; 303 muscovite schist; 82, 201
and 210 carbonate-muscovite schists; 83 quartzose muscovite schist; 232 graphite-muscovite schist; 212 graphite-carbonate-
muscovite quartzose schist; 204 carbonate-chlorite-muscovite schist; 238 muscovite-chlorite schist; 307 marble rich in quartz and
muscovite.
Fig. 2. Distribution of potassium contents in rocks of the speleo-
therapy institution (in wt. %).
cal facility is represented on Figs. 2, 3 and 4 (the area shown in
all of the six partial figures is the same as that of Fig. 1a,b).
A 122 m long section, located in the northern wall of the en-
trance adit, has been investigated in detail (distance between
410 ZIMÁK and TELCL
Sector
Potassium (wt. %)
Uranium (ppm)
Thorium (ppm)
a
m
(Bq.kg
1
)
range
avg.
range
avg.
range
avg.
range
avg.
A
0.9-3.5
1.6
1.0-3.5
2.1
2.8-12.7
5.5
50-201
97
B
1.6-5.1
3.6
1.6-6.1
4.1
5.0-13.8
10.0
99-278
200
C
1.1-3.2
2.0
1.2-3.2
2.1
3.8-9.4
5.8
63-171
103
D
0.9-2.8
1.5
1.3-2.9
2.0
4.0-8.4
5.5
65-125
91
E
0.8-6.9
2.7
1.2-6.4
2.8
3.4-19.0
9.0
54-356
152
F
0.9-3.4
1.8
1.3-5.5
2.8
3.5-12.2
7.2
58-221
120
G
0.7-2.4
1.3
1.2-3.1
1.7
3.0-7.3
4.6
49-139
80
H
1.3-6.7
3.6
1.9-15.8
6.1
4.5-24.7
13.1
81-479
222
Table 2: Naturally radioactive elements contents in rocks of the individual sectors and the calculated radium equivalent mass activity.
Fig. 4. Distribution of thorium contents in rocks of the speleother-
apy institution (in ppm).
the points of measurement is approximately 2 m). The sec-
tion can be divided in two parts, each with different petrogra-
phy. The section between points 254 and 262 is composed of
quartzites. The section between points 201 and 253 is domi-
nated by various kinds of schists passing gradually to quartz-
ites. The results from gamma-ray spectrometry measure-
ments and calculated values of a
m
are shown in Fig. 5.
Fig. 3. Distribution of uranium contents in rocks of the speleother-
apy institution (in ppm).
Whereas in the quartzites the contents of Th and U are very
low (a
m
under 200 Bq.kg
1
) the same contents are moderate-
ly elevated in the schists (calculated a
m
values in individual
section points reached the limit value of 370 Bq.kg
1
). As
the results indicate, the highest contents of thorium (and
probably also uranium) are related to occurrence of graphitic
schists.
411
GEOLOGICAL CONDITIONS AND ROCK RADIOACTIVITY IN SPELEOTHERAPY MEDICAL FACILITY
Fig. 5. Results from detailed gamma-ray spectrometry measurement of natural radioactive element contents in the section situated in the
northern wall of the entrance adit (U and Th values on the vertical axis are indicated in tens of ppm, a
m
values are indicated in Bq.kg
1
).
Conclusions
The gamma-ray spectrometry measurements showed
slightly increased concentrations of naturally occurring ra-
dioactive elements when compared to their occurrence in
natural caves and mine drifts excavated in carbonate rocks
(e.g. in the Moravian Karst and Javoøíèko Karst, the Czech
Republic). However, the U and Th concentrations may still
be considered relatively low. The average values of radium
equivalent mass activity in separate parts of the speleothera-
py medical facility fall within the prescribed state standards
of 370 Bq.kg
1
. Whereas U and Th concentrations in the ex-
posed quartzite in the former mine areas used for speleother-
apy are relatively low, the concentrations of U and Th are
highly variable and often moderately increased in the pelitic
schists and even higher in the exposed graphitic rocks in the
entrance adit. On the basis of our gamma-ray spectrometry
measurements, it is our opinion that even long-term stays at
the speleotherapy medical facility in Zlaté Hory should not
pose any health risk to either patients or the staff.
The relatively higher contents of uranium in the exposed
rocks in the entrance adit (chlorite-muscovite schists and
muscovite schists, often graphitic) and strong tectonic defor-
mation of such rocks may result in elevated concentrations of
222
Rn in the ambient atmosphere. Relatively higher concen-
trations of uranium can be expected in the schists lying be-
low the quartzite horizon in which the speleotherapy medical
facility is located, together with consequent generation of ra-
don that can migrate upwards to diffuse into the subsurface
atmosphere of the medical facility. Consequently, we consid-
er radon monitoring in the speleotherapy medical facility im-
perative.
References
Bernard J.H. 1991: Empirical types of ore mineralizations in the Bo-
hemian massif. ÚÚG Praha 1991.
Constantinides D. & Pertold Z. 1974: Geological position of the
Zlaté Hory-South deposit. Acta Univ. Carol., Geol., 145154
(in Czech).
Èabla V., Hettler J. & Tomík J. 1979: Deposits of the Zlaté Hory
ore district from the point of view so called Global tectonics
theory. Sbor. GPO 20, 569 (in Czech).
Fediuk F., Pouba Z., René M. & Tomík J. 1974: Quartzites, meta-
silexites and metakeratophyres of the Zlaté Hory ore district.
Acta Univ. Carol., Geol., 185202 (in Czech).
Fiera M. & Souèek J. 1974: Metamorphic rocks of the Vrbno Beds
of the Zlaté Hory area (Devonian, NW Moravia, Czechoslova-
kia). Acta Univ. Carol., Geol., 231257 (in Czech).
Janák J. 1970: Geological settings of the Zlaté Hory-South deposit.
MS. PøF UJEP Brno (in Czech).
Janák J. & Augusta L. 1969: New opinions on development and
evaluation of the Zlaté Hory-South ore deposit. Geol. Prùzk.
11, 3540 (in Czech).
Kalenda F. & Grygar R. 1993: Genetic aspects of the stratigraphic
and structural control of the mineralization of the Zlaté Hory
ore district, northern Moravia, Czechoslovakia. In: Procced-
ings Eight IAGOD Symposium, Ottawa, Canada, August 12
18, 1990, 513522.
Patoèka F. 1987a: The geochemistry of mafic metavolcanics: im-
plications for the origin of the Devonian massive sulfide de-
posits at Zlaté Hory, Czechoslovakia. Mineral. Deposita 22,
412 ZIMÁK and TELCL
144150.
Patoèka F. 1987b: Geochemistry of trace elements in metapelites of
Zlaté Hory ore district. Èas. Slez. Muz., Vìdy Pøír. 36, 149158
(in Czech).
Patoèka F. 1988: Minor element geochemistry of pelitic schists of
the Zlaté Hory ore district, the Jeseníky Mts.: Devonin tectonic
setting of the primary sediment provenance. In: Proceedings of
the 1st Int. Conf. on Bohemian Massif. Prague, Sept. 26Oct.
3, 1988, 218221 (in Czech).
Patoèka F. & Vrba J. 1989: The comparison of strata-bound massive
sulfide deposits using the fuzzy-linguistic diagnosis of the
Zlaté Hory deposits, Czechoslovakia, as an example. Mineral.
Deposita 24, 192198.
Sas D., Navrátil O., Sládek P., Surý J., telcl J. & Zimák J. 1998:
Geological and microclimatologica characteristics of speleo-
therapy medical facility of the 2nd level of the Zlaté Hory-
South ore deposit. Scripta Fac. Sci. Nat. Univ. Masaryk. Brun.,
Geology 25, 3746 (in Czech).
Solecki A.T. 1997: Radioaktywnoæ rodowiska geologicznego.
Acta Universitatis Wratislaviensis 1937, 769 (in Polish).
Souèek J. 1978: Metamorphic zones of the Vrbno and Rejvíz series,
the Hrubý Jeseník Mountains, Czechoslovakia. Tschermaks
Mineral. Petrogr. Mitt. 25, 195217.
telcl J. & Zimák J. 1998: Evaluation of content and distribution of
natural radioactive elements in the speleotherapy medical facil-
ity of the 2nd level of the Zlaté Hory-South ore deposit. Geol.
Výzk. Mor. Slez. v r. 1997, 109112 (in Czech).
Zimák J. & telcl J. 1999: Results of detail petrographical and gam-
maspectrometric investigation of selected parts in the speleo-
therapy medical facility of the 2nd level of the Zlaté
Hory-South ore deposit. Geol. Výzk. Mor. Slez. v r. 1998, 162
164 (in Czech).