GEOCHRONOLOGY OF TESCHENITIC INTRUSIONS IN THE OUTER
WESTERN CARPATHIANS OF POLAND CONSTRAINTS FROM
Ar AGES AND BIOSTRATIGRAPHY
, LESZEK KRZEMIÑSKI
, PIOTR NESCIERUK
, ANDRZEJ SZYD£O
, ZOLTÁN PÉCSKAY
and ARTUR WÓJTOWICZ
Polish Geological Institute, Rakowiecka 4, 00-975 Warszawa, Poland; firstname.lastname@example.org
Polish Geological Institute, Carpathian Branch, Skrzatów 1, 31-560 Kraków, Poland
Institute of Geological Sciences, Polish Academy of Sciences, Senacka 1, 31-002 Kraków, Poland
Institute of Nuclear Research, Hungarian Academy of Sciences, Bem ter. 18c, 4001 Debrecen, Hungary
Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin, Poland
(Manuscript received October 25, 2002; accepted in revised form June 23, 2003)
Ar datings for teschenitic rocks in the Silesian Unit of the Outer Western Carpathians in Poland are
presented. Several petrological varieties of intrusions were studied in 5 localities. Dating was performed on monomineral
separates of biotites and amphiboles as well as on whole rock samples. The biotite ages (137.9133.1 Ma Valanginian)
are significantly older than those of amphiboles (112.589.9 Ma AlbianTuronian). Whole rock ages are consider-
ably spread between those two clusters, being concordant either with biotite or amphibole dates or much younger.
Interpretation of data poses some problems because evidence exists for hydrothermal alterations, which might influence
Ar content in both minerals. Older, biotite ages are interpreted as more reliable crystallization ages, since they are close
to the age of surrounding sediments and are concordant with field observations that intrusions in some cases are almost
surficial. Amphibole ages are probably affected by Ar loss due to hydrothermal activity. Comparison with recently
Ar datings implies that the duration of the teschenitic and related magmatism in the Silesian Basin was
probably from Valanginian up to BarremianAptian (ca. 15 Ma).
Key words: Cretaceous, Outer Western Carpathians, Silesian Unit, teschenitic rocks,
The Outer Western Carpathians constitute a thin-skinned fold
and thrust belt. They consist of several nappes (Fig. 1) which
comprise uppermost JurassicLower Miocene sediments
which were thrust onto the European platform in the early
Neogene (for review see e.g. Oszczypko & l¹czka 1985;
Roca et al. 1995). Magmatic rocks are extremely rare in the
Outer Western Carpathians. Among them teschenitic rocks
or teschenite association rocks comprise variegated basic alka-
line rocks of lamprophyre, limburgite, diabase, syenite and te-
schenite type (Smulikowski 1930, 1980; Mahmood 1973;
Kudìlásková 1987). They occur exclusively within the west-
ern part of the Silesian Unit of the Polish and Moravian seg-
ments of the Outer Western Carpathians (Fig. 1). Numerous
geochemical data indicate affinity to within plate basalts or
ocean island basalts (Narêbski 1990; Hovorka & Spiiak
1993; Dostal & Owen 1998; Luciñska-Anczkiewicz 2000).
The age of the teschenitic rocks, discussed since their first
description by Hohenegger (1861), was interpreted between
Cretaceous and Miocene (Wieser 1971; Konior 1977). The
opinion on their Early Cretaceous age (e.g. Hovorka & Spiiak
1993) has been finally established because: (i) they mostly
form sills in the TithonianNeocomian strata (Smulikowski
1930) (ii) hypabyssal and sub-volcanic bodies are associated
with surface volcanism in the Lower Cretaceous sediments
(Matejka & Roth 1953; mid 1962; Roth 1967; Gucwa et al.
1971) (iii) redeposited fragments of teschenitic rocks were re-
ported, in a single locality, from the Albian sediments (Geroch
et al. 1978). However, until recently no radiometric data were
available to constrain the time of the intrusions. The first
Ar data on amphiboles by Luciñska-Anczkiewicz et al.
(2002) gave plateau ages of 122120 Ma (Barremian). In this
Ar results from typical varieties of teschenitic
rocks are presented, together with updated biostratigraphical
ages of contact rocks.
Geological setting and sampling
Teschenitic rocks outcrop between Nový Jièín and Bielsko
Bia³a (Fig. 1) in a single tectonic element called the Cieszyn
Nappe. The nappe comprises sedimentary rocks of Upper Ju-
rassicLower Cretaceous age. The oldest member is the Low-
er Cieszyn Shales, which constitute the detachment horizon of
the Cieszyn Nappe in the studied area (Fig. 2). Their age was
determined as Kimmeridgian(?)/Tithonian (Nowak 1968,
1976; Szyd³o & Jugowiec 1999) and they attain a thickness of
ca. 300 m. They are overlain by the turbiditic complex of
Cieszyn Limestones. Their age is well constrained as Late Ti-
thonianBerriasian and their maximum thickness attains
250 m (Ksi¹¿kiewicz 1964; Nowak 1976). They pass upwards
into the Upper Cieszyn Shales of ValanginianHauterivian
age and reach 300 m in thickness (Koszarski & l¹czka 1976;
GEOLOGICA CARPATHICA, 54, 6, BRATISLAVA, DECEMBER 2003
386 GRABOWSKI et al.
S³omka 1986). Overthrust zone between the Godula Nappe
and the Cieszyn Nappe is noted in the Grodziszcze-Verovice
Beds (HauterivianLower Aptian, 6080 m), (Fig. 2).
Hand and drill samples were taken from several varieties of
teschenitic rocks from Miêdzyrzecze, Rudów, wiêtoszówka,
Puñców, and ¯ywiec (Fig. 1). The outcrop in Miêdzyrzecze is
their northernmost occurrence. It was mentioned by Smu-
likowski (1930) as the richest in olivine in the Cieszyn area.
Samples were collected from the abandoned quarry, from hard
blocks of apparently fresh rock surrounded by completely al-
tered ones. Samples in Rudów (Nowak & Wieser 1978) were
taken from the series of outcrops in the Piotrówka stream,
from the same intrusion as sample C-200 of Luciñska-Anczk-
iewicz et al. (2000). Teschenitic rocks in Puñców (Nowak &
Wieser 1978; Lemberger 1971) occur in a small outcrop in a
Puñcówka creek, north of the church. Samples were taken
from the older teschenite, which hosts the syenite vein sam-
pled (sample C-53) by Luciñska-Anczkiewicz et al. (op.cit.).
Samples in wiêtoszówka were collected from the southern
part of the £añski creek, south of the BielskoSkoczów mo-
torway (see Wieser 1985, fig. 7). In ¯ywiec, two intrusions of
teschenitic rocks were sampled along the famous, well ex-
posed section along the So³a river (l¹czka & Kamiñski
1998). The entire sequence, intensely folded, crops out at the
eastern margin of the ¯ywiec tectonic window, where the Sub-
Silesian Unit is exposed from beneath the Silesian Unit, at the
contact with the Fore-Magura and Magura units (Fig. 1).
K-Ar dating was carried out using whole rock (WR) sam-
ples and monomineral concentrates of biotite and amphiboles.
The samples were crushed and sieved. The 0.20.3 mm frac-
tion was divided for analysis of its potassium content by the
XRF method and for the radiogenic argon content by means of
the static-vacuum mass spectrometry. Mineral separates of the
m fraction were prepared according to standard
procedures (e.g. Geyh & Schleicher 1990) including magnetic
and hydrodynamic separation. Handpicking was applied at the
final stages to eliminate grains with intergrowths of other min-
erals (e.g. pyroxene). The determination of the potassium con-
tent was made in the Central Chemical Laboratory, Polish
Geological Institute, on the Philips PW 2400 spectrometer.
The determination of the radiogenic argon content was made
in the Mass Spectrometry Laboratory, Institute of Physics, Lu-
blin University, using the internal spike method on the modi-
fied MS-10 mass spectrometer. One sample (PU6 see Table
1) was processed at the Institute of Nuclear Research in De-
brecen. Aliquots from about 60 mg for the major part of sam-
ples up to about 180 mg for samples, which contain only
about 0.1 % K has been made. Large samples were necessary,
because a relatively low radiogenic argon content was expect-
ed. Each sample was melted in the double-vacuum crucible of
the argon extraction-purification line in temperature of
1300 °C. Pure argon-38 (produced by the Institute for Inor-
ganic and Physical Chemistry, University of Bern) was used
as the spike. The content of the atmospheric argon was deter-
mined by measurement of the argon-36 peak in the mass spec-
trum. After every measurement cycle the blank cycle was per-
formed (at temperature of about 1350 °C) to check if all argon
was extracted from the sample.
Amphibole analyses were carried out using a Jeol JSM-35
electron microprobe equipped with a Link energy-dispersive
spectrometer at the Polish Geological Institute. Accelerating
voltage was 20 kV with a beam current 2 nA and 50 s count
Fig. 1. Tectonic sketch map of the Outer Western Carpathians with sampling localities indicated (after ¯ytko et al. 1989).
TESCHENITIC INTRUSIONS IN THE WESTERN CARPATHIANS OF POLAND 387
time. Natural and synthetic mineral standards were used and
the raw data were reduced with a ZAF correction procedure.
Foraminifers were separated from the samples which were
taken in the vicinity to teschenitic intrusions, in order to check
the stratigraphic age of the host rock (i.e. maximum possible
age of intrusions). Samples localized nearest to these magmat-
ic bodies were always barren. The lack of microfauna was as-
sociated with thermal and metasomatic processes accompany-
ing the intrusions. These processes resulted in dilution and
destruction of foraminiferal shells. Foraminifers were found in
more distant samples (maximum 5 meters from an intrusion).
Biostratigraphical position of the studied samples was based
on specific foraminiferal assemblages, which were partly de-
scribed from the Cieszyn Beds by Geroch (1966), Bielecka &
Geroch (1977), Olszewska (1997), Szyd³o & Jugowiec (1999)
and Szyd³o (2003). Correlation of radiometric dates to stage
boundaries has been performed using the timescales of Grad-
stein et al. (1994) and Channell et al. (1995), which differ sig-
nificantly in placing the Jurassic/Cretaceous boundary.
Petrographic description of samples
Miêdzyrzecze. The rock from this locality was classified as
alkali biotite-pyroxene picrite. It displays strongly porphyritic
texture with large, well-rounded phenocrysts of olivine (up to
7 mm in diameter), totally pseudomorphed by green bowling-
ite, and smaller phenocrysts of augite (Fig. 3), set in a fine- to
medium-grained, occasionally glassy groundmass. Biotite typ-
ically forms large poikilitic grains with abundant inclusions of
augite, olivine (bowlingite), Ti-magnetite, apatite, and altered
glass. It occurs rarely in aggregates of randomly oriented and
somewhat lighter fine blades. This assemblage is accompanied
by anhedral grains of melanite garnet. Titanomagnetite is a
relatively common phase in this rock, while apatite is signifi-
cantly less abundant. Additionally, brown chrome spinel (up
to 1.7 mm) occurs in an accessory amount. It is mantled by
rims of chrome-bearing Ti-magnetite (see W³odyka et al.
1999). Secondary phases include chlorite and carbonate.
Pseudomorphs of bowlingite after olivine with numerous in-
clusions of Ti-magnetite, as well as fine-grained fragments
composed of bowlingite + clinopyroxene + Ti-magnetite as-
semblage, are most probably derived from the fragmentation
of mantle xenoliths.
Rudów. Teschenites of analcite monzonite composition oc-
cur in this locality. These are coarse- to medium-grained rocks
composed of titanium augite (prisms up to 5.5 mm long), alka-
li feldspars, plagioclase and analcite as the major constituents.
Amphibole is a relatively common phase, which frequently
occurs as overgrowths on clinopyroxene (Fig. 4). It contains
inclusions of augite and apatite, and is accompanied by scarce
greenish olive sheet silicates, mainly as small aggregates of
smectite-group mineral, as well as trace amounts of biotite.
The probed amphiboles are high titanium kaersutite or ferro-
kaersutite (0.5080.706 Ti pfu; Table 1), according to Leake
et al.s (1997) classification scheme. Kaersutite rims are usual-
ly slightly enriched in Fe relative to the cores. Moreover, some
grains have narrow rims of magnesio-hastingsite composition.
The potassium content in the analysed kaersutites is typical for
this group of amphiboles and comparable with that of amphib-
ole concentrate (Table 2). The slightly lower value in the latter
is due to impurities (clinopyroxene, apatite). Small amounts of
the greenish aegirine-augite locally mantles earlier titanium
augite. Plagioclase mostly forms large tabular crystals, where-
as anhedral grains of alkali feldspar and analcite are localized
in the interstitial spaces. Feldspars are partially altered to phyl-
losilicates, which are also found as an interstitial phase. Anal-
cite has a partially primary nature, but may be formed also at
the expense of feldspars. These light minerals are usually
crowded with fine opaque material and fluid inclusions. Ac-
cessory minerals are represented by apatite, sphene and Ti-
magnetite (most often 12.5 mm in diameter). Titanomagne-
tite is partially replaced by goethite. Abundant secondary
minerals also include chlorite, carbonate, as well products of
the autometasomatic replacement of feldspars: prehnite and fi-
brous aggregates of thomsonite.
Puñców. This locality has porphyritic camptonite-type al-
kaline lamprophyres representing two varieties: mesocratic
and melanocratic. The lighter variety is mainly composed of
euhedral prisms of titanium augite (up to 3 mm long) and large
subhedral grains of brown amphibole (Fig. 5). Clinopyroxene
also forms small grains and microlites in the groundmass. Am-
phibole is represented by kaersutite or ferrokaersutite, the
chemical composition and zonation of which are very similar
to that of Rudów amphibole (Table 1). Their potassium con-
tent is comparable with that of P2, P4 and P5 amphibole con-
centrates (Table 2). Kaersutite grains appear in general fairly
fresh but frequently contain abundant inclusions or inter-
growths of clinopyroxene, apatite, Ti-magnetite and occasion-
Fig. 2. Stratigraphic scheme of the Silesian Unit.
388 GRABOWSKI et al.
ally rounded aggregates of greenish smectite-group mineral
(probably after olivine). In the sample P2, amphibole over-
growths on clinopyroxene are frequently observed. The am-
phibole from this sample is rather poor in inclusions (mainly
relics of clinopyroxene). Reddish brown biotite is consider-
ably less abundant than amphibole. It is optically nearly unal-
tered and contains only a few inclusions of clinopyroxene, Ti-
magnetite (Fig. 6), and traces of secondary smectite-group
mineral. Associated interstitial phases include small amounts
of feldspars, colourless glass commonly altered to chlorite,
analcite or zeolites, and secondary prehnite and carbonate.
Among accessory minerals apatite and Ti-magnetite predomi-
nate, whereas sphene occurs occasionally. Amphibole clearly
prevails with titanium augite and biotite in the melanocratic
lamprophyre, and light minerals (alkali feldspars, analcite)
still less abundant than in the mesocratic type. Irregular, light-
er segregations occur within melanocratic variety. These seg-
regations are largely contaminated by mafic fragments to vari-
¯ywiec. The ¯ywiec samples are metasomatized rocks with
preserved original igneous texture. The large degree of alter-
ation makes it difficult to ascertain their protolith: presumably
it belongs to a monchiquite group (see Smulikowski 1930).
They are characterized by extensive replacement of primary
ferromagnesian minerals by chlorite, pale green cryptocrystal-
line aggregates of smectite-group mineral, and carbonate.
Chlorite-carbonate-titanium oxides (anatase, brookite)
pseudomorphs after clinopyroxene are particularly common.
Apatite, which largely takes the form of long prisms, is very
abundant. Similarly, iron and titanium oxides are common
constituents. Pale brown biotite and secondary quartz are also
found. The biotite is very scarce in the majority of samples
(e.g. sample ¯11), but is locally present in greater amounts
(sample ¯9). Both samples were dated and differ significantly
in potassium content (see Table 2). In ¯9, biotite is accompa-
nied by relic clinopyroxene (Fig. 7). Chloritization and car-
bonatization of the primary igneous rock took place probably
at the stage of hydrothermal metasomatism in the presence of
the Ca-bearing fluids from the surrounding sediments (Smu-
wiêtoszówka. The rock defined as altered dolerite is aphy-
ric with relic intergranular or subophitic texture. It is mainly
composed of plagioclase and secondary chlorite, accompanied
by relic augite and minor biotite (Fig. 8). Titanium oxides are
common accessory constituent, while iron oxides, usually in
association with chlorite and carbonate, are distinctly rarer.
Chlorite also occurs fairly commonly as a radial or fan-shaped
aggregates in amygdales, where is frequently associated with
carbonates (Fig. 9) and sometimes with pyrite. Analcite occurs
occasionally in the interstitial areas in some samples (e.g. in
the dated sample SWy).
Results and discussion
As can be seen from the Table 2, the Cretaceous age of the
teschenitic rocks is generally supported by the new K-Ar data
and no Neogene data were obtained. The dates comprise, how-
ever, an unexpectedly broad time interval 148.663.6 Ma
which requires some comments. It is clear that the biotite ages
are significantly older than those of the amphiboles (Table 2).
Mean biotite ages vary between 137.9 and 126.4 Ma (Neoco-
mian) while amphibole ages span between 112.5 and 89.9 (Al-
bianTuronian/Coniacian). Whole rock ages are considerably
Structural formula based on 23 oxygens
Total iron as FeO. Oxide results in wt. %. Fe
partition calculated on the basis of stoichiometry after Droop (1987). Krs kaersutite; Fe-Krs ferro-kaersutite; Mg-Hs
magnesiohastingsite. mg-no. = Mg/(Mg + Fe
Table 1: Representative electron microprobe analyses of amphibole.
TESCHENITIC INTRUSIONS IN THE WESTERN CARPATHIANS OF POLAND 389
Fig. 3. Photomicrograph of alkali biotite-pyroxene picrite from
Miêdzyrzecze (sample MD1). Rounded olivine phenocryst is complete-
ly replaced by bowlingite (p-Ol) and rimmed by biotite (Bt); a large bi-
otite grain contains inclusions of clinopyroxene (Cpx) and Fe-Ti oxides
and is weakly replaced by carbonate (Cal). Plane-polarized light.
Fig. 6. Photomicrograph of an unaltered biotite grain (Bt) with in-
clusions of clinopyroxene (Cpx) and Ti-magnetite (Mgt); analcite
grain is visible near to biotite. Alkaline lamprophyre from Puñców
(sample P5). Plane-polarized light.
Fig. 4. Photomicrograph of teschenite from Rudów (sample RD2).
Brown amphibole (Amp) mantles clinopyroxene (Cpx); interstitial
alkali feldspars (Fs) are strongly altered. Plane-polarized light.
Fig. 7. Photomicrograph of metasomatized rock from ¯ywiec (sam-
ple ¯9c). Numerous biotite grains (Bt) and relics of clinopyroxene
(Cpx) in a matrix of smectite-group mineral (Sm), chlorite (Chl)
and Fe-Ti oxides, with accessory apatite (Ap). Plane-polarized light.
Fig. 5. Photomicrograph of alkaline lamprophyre from Puñców
(sample P4). A large grain of amphibole (Amp) containing inclu-
sions of clinopyroxene (Cpx) and Ti-magnetite (Mgt); fine-grained
groundmass composed of clinopyroxene, analcite (Anl) and Fe-Ti
oxides. Plane-polarized light.
Fig. 8. Photomicrograph of altered dolerite from wiêtoszówka
(sample SWy) composed of abundant secondary chlorite (Chl) with
minor biotite (Bt), relict clinopyroxene (Cpx), plagioclase (Pl) and
analcite (Anl). Plane-polarized light.
390 GRABOWSKI et al.
*age interpreted as overprinted (see text). **This sample was dated at the Institute
of Nuclear Research, Hungarian Academy of Sciences. WR whole rock.
spread between those two clusters, being concordant either
with biotite (e.g. Miêdzyrzecze, ¯ywiec) or amphibole
dates (Puñców, wiêtoszówka) or much younger (Rudów). It
is impossible that these differences reflect a real time interval
between the crystallization of biotite and amphibole. Both
minerals crystallized from the same melt (Smulikowski 1930,
1980; Mahmood 1973). It is also unlikely that the K-Ar age
differences between biotite and amhibole originated due to ar-
gon loss during a reheating event (which might be shown by
hydrothermal alterations). K-Ar closure temperatures are low-
er for biotite (350400 °C) than for hornblende (500700
(Geyh & Schleicher 1990) and in the case of a regional ther-
mal event rather hornblende would preserve the primary K/Ar
A kind of test for reliability of the K-Ar datings would be
the comparison of the radiometric ages of different fractions
and biostratigraphic ages of host sedimentary rocks giving the
oldest possible age of intrusions (Table 3). All the taxons list-
ed in the Table 3 are new findings and were described by
Szyd³o (2003) from the Cieszyn Beds, close to the contact
with the teschenitic intrusions.
Age of foraminiferal assemblages
Maximum age of
Neotrocholina molesta Gorbachik
Trocholina solecensis Bielecka
age: Late Tithonian
Upper Cieszyn Shales
Ammobaculoides carpathicus Geroch
Bigenerina jurassica (Haeusler)
(Late TithonianLate Valanginian)
Pseudoreophax cisovnicensis Geroch
Trochammina quinqueloba Geroch
Buccicrenata condensa Dulub
age: Late Valanginian
contact zone between
Cieszyn Limestones and
Upper Cieszyn Shales
?Planispirilna flava Sztejn
(Late ValanginianEarly Hauterivian)
Ishnusella burlini (Gorbachik)
Spirilina minima Schacko
(Latest TithonianLower Cretaceous)
age: Latest TithonianHauterivian
lack of foraminifers
Upper Cieszyn Shales
Gaudryina oblonga Zaspelova
Pseudoreophax cisovnicensis Geroch
Buccicrenata condensa Dulub
Verneuilinoides neocomiensis (Mjatliuk)
*Stratigraphical ranges according to Geroch (1966), Dulub (1972), Geroch & Nowak (1984), Sztejn et al. (1984), Kuznecova & Gorbachik (1985), Olszewska (1997),
Szyd³o & Jugowiec (1999), Szyd³o 2003 (in print).
Ages of stratigraphical divisions after Channell et al. (1995) time scale.
Ages of stratigraphical divisions after
Gradstein et al. (1994) time scale.
Table 3: Comparison of K-Ar ages of teschenitic rocks with biostratigraphic ages of surrounding sedimentary rocks.
Table 2: K-Ar ages of studied localities (errors at 2
TESCHENITIC INTRUSIONS IN THE WESTERN CARPATHIANS OF POLAND 391
In Miêdzyrzecze and ¯ywiec, the teschenitic rocks intrude
the Cieszyn Limestones, which are of the Late TithonianBer-
riasian age (Nowak 1976). In Miêdzyrzecze, marly shales in-
terbedding limestones, yielded Trocholina solecensis
Bielecka and Neotrocholina molesta Gorbachik, which sug-
gest Late Tithonian age (Table 3). Three of the obtained K-Ar
data indicate a Valanginian age of intrusion, the fourth ear-
liest Barremian. The Valanginian age is therefore accepted for
the intrusion. The crystalline structure of the dated rock indi-
cates that it must have cooled under some overburden. The
younger age for biotite from the sample MD1 must be consid-
ered as an effect of a low temperature alteration (see Fig. 3).
Foraminifers have not been found in ¯ywiec but calpionellids
indicate that teschenitic intrusions occur within the Berriasian
part of the Cieszyn Limestone (Nowak 1970). The K-Ar ages
obtained in this locality are slightly older than expected. The
age of sample ¯9 falls within the Early Berriasian, but only in
the framework of Gradstein et al. 1994 time scale (Table 2).
Sample ¯11 yielded definitely Tithonian ages. Since the po-
tassium content in the sample ¯11 is very low (Table 2) we
consider the age of sample ¯11 (143.5 Ma) as more reliable.
However, both ¯9 and ¯11 ages overlap within a 2
Teschenitic intrusions in Puñców were noted in the contact
zones between the Cieszyn Limestones and Upper Cieszyn
Shales. Samples from the Upper Cieszyn Shales contain mi-
crofauna from which stratigraphically the most important is
(?)Planispirillina flava Sztejn suggesting Late Valanginian
Early Hauterivian age (Table 3). However, since the determi-
nation of this taxon is problematic, an Early Valanginian or
Late Hauterivian age for the samples cannot be excluded. In
this locality three different fractions have been dated, even in
the same hand sample. The difference between biotite and am-
phibole ages amounts to 2742 Ma. The age of the host rock is
close to the biotite age: in the sample P4 Late Berriasian
Earliest Valanginian, in the sample P5 Valanginian. Lapil-
las, benthontized tuffs and lava breccias occurring in the local-
ity were mentioned (Gucwa et al. 1971). These support the
view that the cooling ages must be coeval rather with the sur-
rounding sediments. For this reason the amphibole (Albian
Late Cretaceous) age is considered unlikely.
The Upper Cieszyn Shales are host rocks for the teschenitic
intrusions in wiêtoszówka and Rudów. Variegated foramin-
iferal assemblages indicate Hauterivian age for the former and
Late Valanginian age for the latter locality (Table 3). Pyro-
clastic rocks were described from wiêtoszówka (Gucwa et al.
1971) and the intrusion itself is regarded as almost surficial
(Wieser 1971), which is also supported by thin section obser-
vation in this study. Therefore its apparent K-Ar AlbianCen-
omanian age (100.393.7) must be rejected too. Lava intruded
into the sediments of Hauterivian age (Table 3) and the age of
subvolcanic rock cannot be much younger. The whole rock
and amphibole ages of the Rudów teschenite are significantly
younger than the host sediments which is concordant with the
coarse crystalline structure of the teschenite, indicating rather
slow cooling. The large difference between the whole rock
and amphibole age suggests that significant Ar loss affected
the whole rock system. However, as the amphibole ages
from Puñców gave a unrealistically young age (Table 2), the
amphibole age from Rudów must also be treated with some
Taking into account all the constraints mentioned above, the
K-Ar ages which might be interpreted as crystallization ages
are derived from biotites and whole rock of Miêdzyrzecze pi-
crite and biotites of Puñców lamprophyre (Table 2). The
whole rock age of teschenitic sill from ¯ywiec is close to the
age of surrounding sediments. However, bearing in mind
strong alterations (chloritization, zeolitization) of the tescheni-
tes in this locality, it might have been affected by hydrother-
mal metasomatism. The K-Ar age is evidently related to ap-
parently fresh biotite, which is abundant in the sample ¯9 with
high potassium content (Table 2; Fig. 7).
A question remains why the ages of amphiboles are system-
atically younger than those of biotites? Two explanations
must be considered:
(1) Amphiboles might contain unrecognized inclusions of
other high K minerals (e.g. K-feldspar, reported by Luciñska-
Anczkiewicz et al. 2002). This must be rejected since the po-
tassium content in the amphiboles from Puñców and
Rudów determined by EDS study is comparable with that of
the amphibole concentrates dated (Tables 1, 2).
(2) Secondary alterations (chloritization, zeolitization),
which affected in variegated degree all studied localities,
caused significant Ar loss in hornblende. This option is a like-
ly explanation. Low temperature hydrothermal changes in the
teschenitic rocks are common (Smulikowski 1930) and were
noted also by Luciñska-Anczkiewicz et al. (2002). Their first
degassing steps indicate apparent ages between 62 and
125 Ma (which embrace the amphibole ages obtained in our
study) and were attributed to disturbance of the K-Ar system
related to secondary alterations.
It is remarkable that the alterations, which most probably af-
fected the K/Ar ratios in the amphiboles, have not influenced
biotite in the same way. Geyh & Schleicher (1990, p. 60) men-
tion that, for example, chloritization of biotite causes loss of
potassium and argon in the same proportions, due to the lay-
Fig. 9. Photomicrograph of altered dolerite from wiêtoszówka
(sample SW11). Vesicles filled with carbonates (Cal) and radial ag-
gregates of chlorite (Chl). Plane-polarized light.
392 GRABOWSKI et al.
ered structure of this mineral and, therefore, do not change its
apparent age determined by the K-Ar method. Thus, as al-
ready indicated, biotite ages might be interpreted as crystalli-
zation ages. However alternatively, an excess Ar in biotite
must be seriously considered, as an explanation for the appar-
ently older biotite ages. Solubility of Ar in biotite is relatively
high (see Kelley 2002 for review). An excess Ar might ap-
pear in metamorphic biotites or in fluid-rich environments in
thrust belts, where fluids are derived from basement rocks. We
cannot totally reject that our biotite ages were affected by ad-
Ar influx. Hydrothermal alterations of teschenitic
rocks are well known (e.g. Wieser 1971). The most affected
teschenitic rock in ¯ywiec yielded ages indeed, slightly older
than expected (i.e. than surrounding sediments), which
might show that extra Ar was introduced.
The results obtained in this study might be compared with
the recently published
Ar datings of Luciñska-Anczk-
iewicz et al. (2002). They dated four amphibole concentrates
from the Rudów, Puñców and Boguszowice intrusions
(Fig. 1). All samples yielded similar (Upper BarremianLow-
er Aptian) ages: teschenites from Rudów and Boguszowice
ca. 122 Ma, syenite dyke from Puñców 120 Ma. Age of
amphibole from Rudów obtained here (112.5 Ma) is younger
than that of Luciñska-Anczkiewicz et al. (op.cit.). In our opin-
ion the Ar-Ar age might be more accurate because this method
eliminates errors resulting from inhomogeneity of the studied
grains (Geyh & Schleicher 1990). The K-Ar ages of biotites
obtained in Puñców are ca. 1518 Ma older than those calcu-
lated by Luciñska-Anczkiewicz et al. (op. cit.). However, as in
the area of Puñców up to four varieties of teschenitic rocks
were described (Smulikowski 1930), Ar-Ar and our K-Ar re-
sults are not comparable because they come from different
kinds of rocks. The syenite dyke dated by Luciñska-Anczk-
iewicz et al. (op. cit.) is definitely younger than the mesocratic
teschenitic intrusions. Our data concern a small, shallowly in-
truding lamprophyre body, which was coeval with the pyro-
clastic rocks described from this locality by Gucwa et al.
(1971). The age 137.9134.9 Ma in Puñców probably reflects
an older phase of alkaline magmatism, almost synchronous
with deposition of Cieszyn Beds. Although we cannot discard
the excess Ar hypothesis, the relatively late (Barremian
Early Aptian) and very short (less than 5 Ma) time of emplace-
ment of the entire teschenite association rocks, as postulated
by Luciñska-Anczkiewicz et al. (2002) does not explain the
presence of extrusive rocks in ValanginianHauterivian sedi-
ments. This early phase of magmatism seems to be supported
by the biotite (133.4126.4 Ma) and whole rock (136.5
133.1 Ma) ages of Miêdzyrzecze picrite. More data is certain-
ly required to reconstruct the evolution of teschenitic magma-
tism. Methods other than K-Ar should be applied, especially
to solve uncertainties concerning Ar mobility and retentivity.
1. New K-Ar dating of teschenitic rocks in the Silesian
Nappe of the Polish Outer Western Carpathians, performed on
amphiboles, biotites and whole rock, confirmed their Creta-
ceous age. The considerable scatter of results (148.663.6 Ma)
is caused by hydrothermal alterations of the rocks. Biotite and
whole rock ages of the olivine picrite from Miêdzyrzecze
(133.4±1.8, 136.5±2.0, 133.1±1.8 Ma), and biotite ages of the
alcalic lamprophyres in Puñców (137.9±2.0, 134.9±3.0 Ma)
are interpreted as most reliable, indicating Valanginian age.
The Early Berriasian (143.5±2.0 Ma) age of teschenitic rocks
in ¯ywiec must be treated with some caution, as the rock is
strongly altered and tectonized and the presence of some ex-
tra Ar in biotite is not unlikely.
2. Radiometric data obtained here indicate that teschenitic
magmatism within the Silesian Unit of the Outer Western Car-
pathians might have started earlier than 122 Ma (Barremian)
(Luciñska-Anczkiewicz et al. 2002). Independent evidence is
supplied by the presence of extrusive rocks in the Valangin-
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