MANGANESE HARDGROUNDS IN LIMESTONES OF THE WESTERN CARPATHIANS 317
GEOLOGICA CARPATHICA, 54, 5, BRATISLAVA, OCTOBER 2003
317328
MINERAL AND CHEMICAL COMPOSITION OF MANGANESE
HARDGROUNDS IN JURASSIC LIMESTONES
OF THE WESTERN CARPATHIANS
IGOR ROJKOVIÈ
1
, ROMAN AUBRECHT
2
and MILAN MIÍK
2
1
Department of Mineral Deposits, Faculty of Natural Sciences, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovak Republic;
rojkovic@nic.fns.uniba.sk
2
Department of Geology and Paleontology, Faculty of Natural Sciences, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovak
Republic; aubrecht@nic.fns.uniba.sk
(Manuscript received June 6, 2002; accepted in revised form March 11, 2003)
Abstract: Manganese crusts and nodules in Jurassic limestones correspond to those formed on recent submarine pelagic
or hemipelagic non-deposition surfaces and hardgrounds. The ore mineralization is represented by pyrolusite, romanèchite,
manganite, and iron hydroxides. The structure of the manganese minerals, Mn/Fe and Si/Al ratio and Co, Cu, Ni and REE
distribution in the ores indicate hydrogenetic and diagenetic accumulation of manganese minerals. Later, Cretaceous
supergene accumulation filled fissures and cavities in the limestones.
Key words: Tethys, Jurassic, manganese minerals, hardgrounds, chemical composition.
Introduction
Jurassic sections in the Alpine-Mediterranean region show
transitions from Bahama-type carbonates through red nodular
limestones (Rosso Ammonitico), to deep oceanic pelagic
limestones and radiolarites. Manganese nodules and crusts
formed near the continental margin on seamounts during high
sea-level are characteristic for the Jurassic period in the North-
ern Calcareous Alps, Sicily, Betic Cordillera and other parts of
the Tethys region (Jenkyns 1970; German 1972; Drittenbass
1979; Jenkyns et al. 1991; Roy 1980; Vera & Martín-Algarra
1994; Jimenez Espinosa et al. 1997; DiStefano & Mindszenty
2000).
Manganese in pelagic carbonates indicates major tectonic
events during geodynamic evolution of the Jurassic continen-
tal margin of the Tethys-Ligurian Sea. The main transgressive
phases (Early Toarcian, Late Aalenian to Bajocian and Late
Bathonian to Callovian) are marked by a manganese content
increase whereas the regressive phases (Late Pliensbachian,
Late Toarcian to Middle Aalenian, Early Bathonian to Middle
Bathonian, Oxfordian) are characterized by decreasing trends
(Corbin et al. 2000). Such occurrences are common in the Ju-
rassic limestones of the Western Carpathians (Rakús 1987).
Black manganese crusts (hardgrounds) of small extent
and mostly several centimetres thick are known in the Klippen
Belt near Vratec, Babiná, Boleov, Kyjov-Pusté Pole and
Drieòová hora Hill (Miík 1979, 1994; Miík & Sýkora 1993).
The crust from Babiná contains Mn-Fe oxides with 17 % of
MnO and 15 % of Fe
2
O
3
(Miík et al. 1994). In the Bole-
ovská dolina Valley, between Nemová and Pruské, Aubre-
cht et al. (1998) have described Fe-Mn crust (hardground
and nodules) 15 cm thick in the Upper Callovian-Lower Ox-
fordian limestone near Boleov in the Czorsztyn Unit. They
identified here ranciéite, goethite and hematite with the help
of X-ray diffraction.
Other important occurrences of manganese ores were ex-
ploited during the First World War near Mikuovce. Manga-
nese ore with ammonites occurs in deep pelagic to shallow
neritic sea sediments (Andrusov et al. 1955). Two types of
manganese ores were identified in the area of Mikuovce (An-
drusov et al. 1955) and later in Lednica castle within the Pien-
iny Klippen Belt (Miík & Rojkoviè 2002). The first one is
low-grade ore and belongs to syngenetic accumulations of the
hardground type in red nodular Callovian-Oxfordian lime-
stones. The second one represents high-grade ore filling clefts
in the crinoidal Bathonian limestones at the locality Mikuo-
vce and small caverns in the Kimmeridgian-Lower Tithonian
limestone at the locality Lednica (Miík & Rojkoviè 2002).
Pyrolusite, psilomelane and wad were found in the ore (An-
drusov et al. 1955). Èechoviè (1942) proposed sedimentary
origin of the deposit with later metasomatic alteration of lime-
stone. However, cherts as well as manganese ores were of sed-
imentary-diagenetic origin according to Andrusov et al.
(1955). Formation of the ore was contemporaneous with the
accumulation of ammonites in the Upper Dogger and Lower
Malm and filling of fissures in the Bajocian was either of hy-
drometasomatic or infiltration origin (Andrusov et al. 1955).
The aim of this paper is to include new data and ideas on man-
ganese mineralization in the limestones of this region since the
last paper was published in 1955.
Geological setting
Jurassic manganese hardgrounds in the Western Car-
pathians are related to periods of transgressions and sea-level
highstands. Such were the periods of Late Sinemurian, Toar-
cian and CallovianOxfordian. The Liassic hardgrounds are
mostly ferroan; the manganese hardgrounds were only found
in the Nedzov Nappe of the Èachtické Karpaty Mts (Chtelnica
318 ROJKOVIÈ, AUBRECHT and MIÍK
south. It is composed of Jurassic, Cretaceous and Paleogene
sequences. This zone was affected by at least two major defor-
mation phases. The first phase, which formed Laramian nappe
structure occurred in the latest Cretaceous and earliest Paleo-
gene. The second one, which disturbed the previous structure,
was an Oligocene-Early Miocene orogenic phase, dominated
by lateral movement and transpressional deformation in a
large shear-zone. This process created the recent, unique klip-
pen structure, where limestone successions (mostly Jurassic to
Early Cretaceous) form blocks and tectonic slices enveloped
by softer marlstones and claystones (predominantly Late Cre-
taceous). The crystalline basement of these sedimentary units
is not known; it was most probably consumed by underthrust-
ing beneath the Central Carpathian block. Despite this exten-
sive tectonic deformation, the Pieniny Klippen Belt has almost
no metamorphic or thermal overprint and its sequences have
perfectly preserved fossils and sedimentary structures.
All the PKB localities studied herein belong to the Czorsz-
tyn Unit, which formed a pelagic swell during the Jurassic pe-
riod (a hypothetical Czorsztyn Swell sensu Miík 1994; = Ridge
sensu Birkenmajer 1986, 1988). In the Aalenian, the sedi-
mentary area lacked vertical contrast and deposition of marl-
stones and claystones was dominant at that time (Harcygrund
Shale and Skrzypny Shale Formations according to Birkenma-
jer 1977). Uplift of the Czorsztyn Swell was strongly accentu-
ated in the Bajocian and resulted in deposition of a white
crinoidal limestone (Smolegowa Limestone Formation) fol-
lowed by red crinoidal limestone (Krupianka Limestone For-
mation). After a gradual sea-level rise during the latest Bajo-
cian and Bathonian to Oxfordian, the deposition of the
crinoidal limestone gave way to pelagic red nodular Ammonit-
ico Rosso-type limestones of the Czorsztyn Limestone Forma-
tion, which was widespread in the Czorsztyn Unit between the
Callovian and Late Tithonian. Some non-nodular equivalents
of the Czorsztyn Limestone Formation are locally observed
Fig. 1. Location of the studied manganese hardgrounds in the
Western Carpathians.
Fig. 2. Jurassic lithostratigraphy of the Nedzov Nappe.
Late Sinemurian, Hruové, Bzince pod Javorinou Toar-
cian). The Callovian-Oxfordian manganese hardgrounds are
common in the Czorsztyn Unit of the Pieniny Klippen Belt
(localities Boleov, Horné Sànie, Mikuovce and Vratec,
Fig. 1). For comparison, a few samples of Albian age (Ka-
menica and Jarabiná, both Czorsztyn Unit) were studied. The
Albian hardgrounds in the Czorsztyn Unit were formed in
similar eustatic regime as the Middle Jurassic ones. Their de-
velopment was also characterized by rapid sea-level rise, with
condensed sedimentation and formation of phosphatic, man-
ganese and ferroan stromatolitic crusts.
The Nedzov Nappe belongs to the Hronic Unit, but has
common features with originally more southern units of the
Silicicum (Mello in Salaj et al. 1987). The Jurassic-Lower
Cretaceous sequence, named as Hruové Group, represents
sediments deposited in a relatively shallow-water environ-
ment. The Liassic is represented by cherty crinoidal lime-
stones. Later, the Fe-Mn condensed crust was formed in the
Toarcian (Fig. 2). It is overlain by pseudonodular limestones
with cherts (Middle-Upper Jurassic). The Upper Jurassic is
represented by micritic limestones with layers of allodapic
limestones (Barmstein Limestones Miík & Sýkora 1982).
The Pieniny Klippen Belt (PKB) is the most complicated
tectonic unit of the Western Carpathians. It is a narrow belt
extending from the Vienna Basin for over 600 km, through
southern Poland, eastern Slovakia and Transcarpathian
Ukraine as far as northern Romania. This zone is less than
15 km wide. It is tectonically separated from the Flysch Belt
to the north and from the Central Western Carpathians to the
MANGANESE HARDGROUNDS IN LIMESTONES OF THE WESTERN CARPATHIANS 319
(Andrusov 1945, p. 17). This relatively uncondensed variety
was later named the Bohunice Limestone Formation by Miík
et al. (1994). The time of the sedimentation regime change
from crinoidal limestones to Czorsztyn or Bohunice Lime-
stones was associated with condensed sedimentation, mainly
at the base of the latter formations. At this time, pronounced
formation of manganese crusts took place (Fig. 3).
Studied localities
Chtelnica
The locality occurs 2.5 km north of the village of Chtelnica,
on the NW slope of Holý vrch Hill. The locality was found by
Perel (1966). Poor outcrops do not allow a complete recon-
struction of the Liassic sequence. There are probably three
units: 1. Grey to greenish, fine-grained crinoidal limestone
with glauconite and numerous ammonites (Sinemurian), 2.
pink, brownish to grey organodetrital micritic limestones (Up-
per Lotaringian), 3. pink micritic limestone (probably Toar-
cian). Most likely, Fe-Mn crust debris and nodules found in
the lower part of the slope belong to the latter unit (Fig. 4.1).
In the crust, some recrystallization features, bivalve borings
(Fig. 4.2) and brecciation were observed.
Hruové
The locality is an abandoned quarry in the Rubanina Valley
in the Èachtické Karpaty Mts, 500 m SSE from the village
Hruové. A hardground consisting of a crust about 5 cm thick
has been known for a long time. The beds are tectonically
overturned. Jurassic of the Choè Nappe is uncovered in the
quarry. Hanáèek (in Salaj et al. 1987) attributed this succes-
sion to Hruové Group of the Nedzov Nappe. More recently,
the locality was described by Kullmanová & Gapariková
(1983, p. 56), where a stratigraphic position of these deposits
is mentioned. The stratigraphic base is represented by white
and pink crinoidal biosparites (Liassic, maximum Lower
Toarcian). The hardground occurs at the boundary between
the crinoidal limestones (at the contact with Mn-hardground,
the crinoidal ossicles have scalenohedral edges) and red nodu-
lar to pseudonodular limestones (equivalent of Klaus or Reit-
mauer Limestone Formation). The original, lower part of the
hardground crust is black (manganese), whereas the original
upper part is brown (ferroan, Fig. 4.3). Their boundary is un-
dulated, reminding plastic deformation. The brown part is
structureless or it forms a stromatolitic structure up to 4 cm
thick. It contains abundant encrusting foraminifers. The hard-
ground crust yielded the following Late Toarcian to Middle
Bajocian fossils (Kullmanová & Gapariková 1983): Phyllo-
ceras cf. kunthi, Ptychophylloceras sp., Caliphylloceras sp.,
C. cf. connectens, Lytoceras sp., Pseudogrammoceras falla-
ciosum, ?Leioceras sp., Tmetoceras scissum, Chondroceras
sp. and Toarcian gastropod Pleurotomaria mulsanti (Thiol-
liere). The overlying red nodular limestone yielded an ammo-
nite Leptoceras (Vermisphinctes) which ranges from Bajocian
to Early Bathonian.
Bzince pod Javorinou
A quarry near the village of Bzince pod Javorinou was illus-
trated by Hanáèek (in Salaj et al. l987). Directly overlying Lias-
sic crinoidal limestones, a limonitized limestone layer occurs,
with Fe-Mn oncoids. Algal and bivalvian borings are present in
the hardground. The hardground forms a basis for the pseudon-
odular Adnet Limestone (Kullmanová & Gapariková 1983).
The probable age of the hardground is Late Toarcian.
Boleov
A klippe of the Czorsztyn Unit occurs at the end of the
Boleovská dolina Valley west of Boleov village in the Mid-
dle Váh Valley. It was for the first time described by Salaj
(1987, 1990, 1997) and later by Aubrecht et al. (1998). Over a
thick bedded to massive, white to yellowish sandy crinoidal
limestone (Smolegowa Limestone, BajocianLower Callov-
ian) a dark violet to black-reddish limestone occurs with a 1
5 cm thick brown to black crust (Fe-Mn hardground). The
hardground contains Fe-Mn stromatolites, rarely domatic with
radial partition and oncoids (Upper CallovianLower Oxford-
ian). Higher up, it is followed by pink-violetish limestone with
black-coated (Mn oxides) bivalve shells (Bohunice Lime-
stone). This limestone is overlain by creamy micritic lime-
stone (Sobótka Limestone) with red-coated tiny intraclasts
(Upper Tithonian).
Horné Sànie
A manganese crust with stromatolites was found in Bohu-
nice Limestone within the easternmost of the quarries of
Horné Sànie cement factory, at Ostrá hora Hill. The limestone
contains numerous foraminifers Globuligerina sp. and calcar-
eous dinocysts Colomisphaera fibrata Nagy indicating an Ox-
fordian age for the manganese crust.
Fig. 3. Lithostratigraphic scheme of the Czorsztyn Unit.
320 ROJKOVIÈ, AUBRECHT and MIÍK
Mikuovce
The locality near Mikuovce was recently described by
Miík & Rojkoviè (2002). An abandoned, collapsed mine gal-
lery occurs SW of Mikuovce village (Za Skalkou locality), at
the altitude 420 m above sea-level. According to Andrusov et
al. (1955), this is the so-called Upper Deposit. High-grade
manganese ore is found at the entrance to the gallery, filling a
cleft in the Middle Jurassic crinoidal limestones. The cleft is
oriented 110115
°
/60
°
towards NNE. The thickness of the
massive ore is about 1030 cm. East of the gallery, about
100300 m west of a local creek, is the mine waste dump. In
limestone material, manganese ore can be found locally,
mainly along the southern margin of the dump.
The base of the klippe at the mine gallery is formed by spot-
ty limestone and marlstone (Aalenian Opalinum Beds),
overlain by crinoidal limestone (Smolegowa and Krupianka
Formation BajocianBathonian) and red nodular to mas-
sive micritic limestone (Czorsztyn Limestone Callovian
Oxfordian). In this micritic limestone, lenses of manganese
ores are developed. The Malm is represented by pale massive
bioherm limestone (Vratec Limestone).
Vratec
The locality occurs in the part of the Vratec Klippen
(Czorsztyn Unit) north of the road cutting the Vratec Saddle,
about 600 m SW from the elevation point 898 m (Javorník
Hill). The locality was studied in detail by Aubrecht et al.
(2000). A black manganese crust (hardground) and oncoids
occur in a position which is not yet clear. The thickness of the
crust varies from 15 to 40 cm but its lateral extension is cov-
ered by debris and vegetation. Below the hardground there are
pale crinoidal limestones of Bajocian?Bathonian age; the
overlying strata are problematic. There is red mudstone, most
probably Upper Jurassic, with layers of crinoidal limestone.
Microfacies analysis shows that they represent biomicrites
with planktonic crinoids Saccocoma, crinoidal ossicles, Glob-
ochaete alpina, foraminifers Lenticulina sp., ostracods, di-
nocysts and common lithoclasts. The only stratigraphically
valuable microfossil is Saccocoma indicating most likely a
Kimmeridgian to Early Tithonian age. The ammonite fauna
indicate that the time span of the hardground formation is Ox-
fordian to Lower Tithonian. The hardground comprises en-
crusting foraminifers Bullopora tuberculata and serpulids
Fig. 4. 1 Manganese nodule. Chtelnica, sample Cht1. 2 Aragonite shell of ammonite (white) was dissolved shortly after the deposition
and the mold was filled with micrite containing small bioclasts. Hardground was formed as a result of rapid lithification and then perforated
by a boring organism. The boring was filled with grey, pure micrite. Chtelnica, transmitted light, parallel polars. 3 Manganese crust
(black, top) overlying Fe crust (light grey). Hruové, sample Hru1, polished slab. 4 Detail of the serpulid microreef, colonizing the hard-
ground. The serpulid tubes are affected by microborings and impregnated by Mn-oxides. Vratec, transmitted light, parallel polars.
MANGANESE HARDGROUNDS IN LIMESTONES OF THE WESTERN CARPATHIANS 321
(Fig. 4.4). The manganese crust is commonly penetrated by
ptygmatitically folded calcite veinlets that testify an initial
plasticity of the manganese crust. Hedbergelid foraminifers
likely to be of Albian age occur in tiny lenses of microbreccia
within the hardground. Their presence may be explained by
occurrence in the filling of younger neptunian microdykes.
Methods
Minerals were studied by polarizing microscope in both
transmitted and in reflected light and by scanning electron mi-
croscope (SEM). They were analysed by wave-dispersion X-
ray microanalysis (WDX) and by X-ray diffraction analysis
(XRD). WDX analyses of Al, Ba, Ca, Fe, K, Mg, Mn, Na, Si
and Sr were carried out on a JEOL-733 Superprobe X-ray mi-
croprobe (Geological Survey of the Slovak Republic). Natural
and synthetic standards were used to calibrate the systems:
Al
2
O
3
, BaSO
4
, wollastonite, rhodonite, hematite, orthoclase,
MgO, albite, SiO
2
and SrTiO
3
. Electron beam was stabilized
at 1518 nA, with 15 and 20 kV accelerating voltage. Counts
were acquired for 100 seconds, and recalculated using XPP
quantitative correction. The electron beam was focused on 2
5 micrometers. Detection limits were better than 0.1 wt. %.
Relative standard deviation ranged from ±5 % (for 1 wt. %) to
±25 % (for 0.1 wt. %). Chemical composition was calculated
using the Minfile programme.
X-ray diffraction (XRD) analyses were done on a Philips
PW 1710 diffractometer. Samples with high content of Fe
were analysed by CoK
α
radiation (
λα
1
= 1.78896
×
10
10
m,
λα
2
= 1.79285
×
10
10
m), and CuK
α
radiation (
λα
1
=
1.54060
×
10
10
m,
λα
2
= 1.54439
×
10
10
m) was used in the
case of other samples. Accelerating voltage of 35 kV and
beam current of 20 mA were used in the range 4 to 60
°
23,
with shift 0.02
°
23.
Chemical composition of rocks was determined by X-ray
fluorescence analysis (XFA) for major elements of the rocks,
and by colorimetry for P
2
O
5
. Major elements were analysed
on the X-ray spectrometer Philips PW 1410/20. Instrumental
conditions: X-ray tube with Rh anode (voltage 40 kV, current
40 mA), gas flow detector with Ar/CH
4
= 90/10 filling, crystal
LiF 200 for Fe, Mn, Ti, Ca, K and TlAP for Si, Al, Mg, Na.
Samples (1.3 g) were fused with Li
2
B
4
O
7
(5.5 g) at 1050
°
C in
Pt-crucible. The accuracy of the analyses with respect to the
certified values of the standard materials is within ±20 % for
light elements (Na, Mg) and Mn and ±510 % for other ele-
ments. Rare earth elements (REE) were analysed by atomic
emission spectroscopy with inductively coupled plasma
(AES-ICP). Samples sintered with Na
2
O
2
were dissolved by
HCl and later by oxalic acid. Samples were analysed by se-
quential atomic emission spectrometer with inductively cou-
pled plasma Liberty 200 VARIAN with ultrasonic nebulizer
CETAC. Detection limits ranged from 0.03 to 1 ppm. Relative
standard deviation ranged from ±3 % (for 0.1 wt. %) to ±20 %
(for 0.001 wt. %). Optical emission spectroscopy (OES) was
used for B, Ba, Co, Cr, Cu, Ni, Pb, Sr and V. The spectra of
samples were recorded by the grid spectrograph PGS-2 in UV
and visual area, with 6 A power arch as activating source.
Measuring time was 90 s. Rock-Eval pyrolysis was used to
determine organic carbon (TOC) content.
Results
Manganese mineralization
Pyrolusite, psilomelane and wad were described mostly
as manganese minerals of oxidic ore in limestone (Andrusov
et al. 1955). This study has confirmed that pyrolusite is ac-
companied by romanèchite, manganite and todorokite. Iron
hydroxides dominate in the brown coloured part of hard-
grounds.
Pyrolusite
β
-MnO
2
is an abundant mineral in the studied
ores. It can be distinguished from other manganese minerals
by its characteristic yellow tint and high reflectivity. Colum-
nar crystals are from several micrometers to 0.01 mm, up to
0.05 mm long. Larger grains can be seen along the fissures in
fine-grained pyrolusite. They form zoned colloform botryoi-
dal to concentric aggregates (about 0.1 mm across) or radial
aggregates about 0.1 mm up to 3 mm across. Pyrolusite re-
places spheroidal foraminifers (Fig. 5.1), bivalves, echino-
derm fragments and ammonites. Columnar microstromatolites
(up to 0.5 mm long and 0.1 mm thick) are often replaced by
pyrolusite in manganese crusts. Manganese nodules are
formed by zoned aggregates of pyrolusite up to 0.5 mm thick.
Pyrolusite also fills traces after fossils (up to 1 cm thick). Thin
zones of pyrolusite (about 0.05 mm thick) are often alternat-
ing with romanèchite and calcite. It replaces, or cuts in thin
veinlets, calcite, romanèchite, manganite and todorokite. Mi-
croscopic identification of pyrolusite is consistent with the
WDX chemical composition (Table 1) and the XRD data.
Romanèchite (Ba,H
2
O)
2
(Mn
++++
,Mn
+++
)
5
O
10
is a common
mineral in the hardgrounds. Colloform zoned aggregates (0.1
to 1.5 mm across) consist of irregular grains (0.01 to 0.05 mm
in size) or needle shaped crystals (up to 0.01 mm long) in the
central part forming a radial texture. Thin zones (up to
No
Sample
MnO
2
Fe
2
O
3
SiO
2
CaO
Total
1
Hr1
98.0
1.6
0.3
0.6
100.5
2
Hr1
99.0
1.4
0.3
0.4
101.1
3
Hr1
96.3
0.9
0.5
0.5
98.1
4
Hr1
96.9
1.3
0.3
0.8
99.2
5
HS1
94.6
2.9
0.7
0.8
99.1
6
HS1
94.4
3.4
0.9
0.9
99.6
7
HS1
95.7
3.6
0.7
0.7
100.8
8
HS1
92.2
2.8
1.0
0.8
96.7
9
Vr1
92.1
2.1
2.3
0.5
97.0
10
Vr1
92.0
2.5
2.0
0.6
97.1
No
Sample
Mn
Fe
Si
Ca
Total
1
Hr1
0.978
0.018
0.004
0.009
1.009
2
Hr1
0.981
0.016
0.004
0.007
1.007
3
Hr1
0.982
0.010
0.007
0.007
1.006
4
Hr1
0.979
0.014
0.004
0.012
1.009
5
HS1
0.959
0.032
0.010
0.013
1.015
6
HS1
0.952
0.037
0.013
0.014
1.017
7
HS1
0.954
0.040
0.011
0.011
1.016
8
HS1
0.955
0.032
0.014
0.013
1.014
9
Vr1
0.944
0.024
0.034
0.009
1.010
10
Vr1
0.944
0.028
0.030
0.010
1.012
Localities (for all tables): Bo Boleov, Bz Bzince pod Javorinou, Hru Hru-
ové, HS Horné Sànie, Ch Chtelnica, and Vr Vratec.
Table 1: Chemical composition of pyrolusite (wt. % of oxides and
atomic proportion of elements O=2).
322 ROJKOVIÈ, AUBRECHT and MIÍK
0.1 mm) are alternated with pyrolusite (Fig. 5.2). Romanè-
chite is easily distinguished by back-scattered electron image
in scanning electron microscope (BEI-SEM) as a lighter phase
due to increased content of Ba, as was confirmed by WDX
analysis (Table 2).
Todorokite (Mn
+2
,Ca,Mg)Mn
+4
3
O
7
×H
2
O is abundant in
some localities. Colloform aggregates are concentric or they
form crusts up to 1 cm thick with columnar microstromatolites
on their surface (Fig. 5.3). Zoning, as well as radial texture,
can be observed in aggregates. Aggregates consist of xenom-
orphic grains (0.01 to 0.05 mm in size). Needlelike crystals
form radial aggregates or bundles (Fig. 5.4). Todorokite com-
pletely replaces fossils (foraminifers). It forms dark cores of
concentric aggregates (up to 0.03 mm across) rimmed with
romanèchite. CaO content ranges from 4.5 to 8.6 wt. % (Ta-
ble 3). Chemical composition is close to todorokite or ran-
ciéite (Ca,Mn
++
)Mn
++++
4
O
9
×3(H
2
O). Ranciéite was identified
in Boleov by XRD (Aubrecht et al. 1998). Todorokite was
also confirmed by XRD.
Manganite
γ
-MnOOH was found in the continental lime-
stone breccia of the Early Cretaceous age. Spherical, radial
and fan-like aggregates up to 3 mm in size replace non-marine
algae. The central part of the aggregates formed by xenomor-
phic grains is overgrown by alternating zones of calcite, ro-
manèchite and manganite with radial texture. Manganite is re-
placed and cut by veinlets of pyrolusite. Identification of
manganite was confirmed by XRD and WDX in remobilized
Fig. 5. 1 Spheroidal aggregate of coarser pyrolusite replacing foraminifers in fine-grained pyrolusite. Hruové, sample Hr1, SEM-
BEI. 2 Colloform zoned aggregates of pyrolusite (pl) and romanèchite (ro) are cut by veinlets of younger calcite (ca). Vratec, sample
Vr6, reflected light, parallel polars. 3 Colloform zonal aggregates of todorokite (light grey) replacing columnar stromatolites. Horné
Sànie, sample HS1, SEM-BEI. 4 Aggregate of todorokite (white) in limestone. Hruové, sample Hru3a, SEM-BEI.
No Sample MnO
2
Fe
2
O
3
MgO
SiO
2
K
2
O CaO BaO Total
1 Bz1
77.5
0.0
1.2
0.2
0.4
2.6
3.9
85.6
2 Bz1
76.5
1.2
1.4
0.1
0.5
2.6
4.3
86.7
3 Bz1
77.2
1.1
1.2
0.2
0.5
2.4
4.4
87.0
4 Hru3
73.5
2.2
0.3
0.4
0.5
3.3
7.8
88.0
5 Vr2
74.5
3.3
0.0
1.7
2.0
0.6
8.5
90.5
6 Vr2
76.1
3.6
0.0
0.4
2.0
0.6
8.1
90.8
7 Vr2
76.0
3.8
0.0
1.8
2.0
0.6
8.2
92.5
8 Vr2
77.5
4.0
0.0
0.6
2.0
0.6
8.1
92.8
9 Vr6.1 79.1
3.3
0.0
2.2
2.5
0.3
4.8
92.2
10 Vr6.2 76.1
2.8
0.0
2.2
2.4
0.3
5.3
89.2
No Sample Mn
+4
Fe
+3
Mg
Si
K
Ca
Ba
Total
1 Bz1
4.712 0.000 0.154 0.014 0.040 0.240 0.134 5.294
2 Bz1
4.629 0.082 0.177 0.009 0.058 0.247 0.149 5.350
3 Bz1
4.650 0.075 0.155 0.015 0.054 0.225 0.152 5.325
4 Hru3
4.568 0.145 0.039 0.033 0.051 0.318 0.273 5.427
5 Vr2
4.469 0.215 0.000 0.143 0.221 0.055 0.288 5.391
6 Vr2
4.611 0.238 0.000 0.040 0.224 0.057 0.279 5.449
7 Vr2
4.448 0.240 0.000 0.156 0.216 0.053 0.273 5.385
8 Vr2
4.589 0.261 0.000 0.048 0.219 0.052 0.272 5.440
9 Vr6.1 4.503 0.203 0.000 0.179 0.258 0.027 0.156 5.339
10 Vr6.2 4.507 0.181 0.000 0.186 0.266 0.031 0.178 5.349
Table 2: Chemical composition of romanèchite (wt. % of oxides
and atomic proportion of elements O=10).
supergene ore in Lednica and Mikuovce (Miík & Rojkoviè
2002).
Goethite
α
-FeOOH and other iron-hydroxides form crusts
and aggregates disseminated in limestone. Crust of manga-
nese minerals is overgrown by brown and yellow crust of iron
MANGANESE HARDGROUNDS IN LIMESTONES OF THE WESTERN CARPATHIANS 323
hydroxides. Thin zones of iron hydroxides alternate with
manganese minerals and calcite in the Mn-Fe nodules. Goet-
hite also forms veinlets in todorokite and pyrolusite. Their
heterogeneity is documented by back-scattered electron image
in scanning electron microscope (BEI-SEM), and WDX con-
firmed several wt. % of MnO
2
, Al
2
O
3
and SiO
2
.
Calcite CaCO
3
is a dominant mineral of limestone. It is
fine-grained in biomicritic limestone cementing fossils (fora-
minifers, bivalves, echinoderms and ammonites). Coarser
grained calcite (grains up to 0.7 mm) replaces fossils and
forms veinlets. Younger calcite veinlets cut biomicritic lime-
stone as well as the aggregates of manganese minerals. Cores
of the manganese nodules are formed by limestone with
coarse calcite crystals (up to 1 mm), and by fossils. The cores
coated by alternating zones of calcite, pyrolusite and iron hy-
droxides are up to 0.1 mm thick. Syneresis fissures in nodules
are filled with coarser grained calcite. WDX has confirmed up
to 0.6 wt. % of MgO and FeO.
Geochemical characteristics of manganese ore
Typical crusts and nodules with abundant iron hydroxides
(Horné Sànie, Chtelnica and Vratec) show distinctly in-
creased iron content (Table 4). Manganese content in the ore
increases with increasing ratio of supergene pyrolusite (Bole-
ov, Hruové), especially in places of supergene mobilization
and accumulation, where the highest Mn/Fe ratio is noted
(Mikuovce, Lednica, Miík & Rojkoviè 2002). The highest
content of Mn
was found in fissures and cavities of manga-
nese ore in Mikuovce and Lednica, reaching up to 48 wt. %,
with higher Mn/Fe (Nx10) comparing to sedimentary manga-
nese mineralization in the Callovian-Oxfordian red limestone,
with low Mn/Fe ratio (Nx1). Si/Al ratio in average corre-
sponds to 1.84 (Fig. 6).
Ba, Co, Cu and Ni are accompanying trace elements of
manganese mineralization. Presence of romanèchite increases
Ba content over 2000 ppm. Co, Cu and Ni are dominant trace
elements in the studied manganese crusts and nodules. The to-
tal Ni+Co+Cu content in the studied samples reaches up to
0.5 wt. % with maximum values for Ni > 2000 ppm,
Cu > 3000 ppm and Co over 850 ppm (Fig. 7). Ni shows a
positive correlation with Fe and negative with Mn. Co shows
positive correlation with Mn. Increased content of Pb and V
suggests that the elements are bound to iron hydroxides. Sr is
associated with carbonates. The content of organic carbon is
low (average content 0.20 wt. %). REE distribution shows
only slight dominance of light REE (LREE), and distinct posi-
tive Ce anomaly (Table 5, Fig. 8).
No Sample MnO
2
Fe
2
O
3
MgO SiO
2
K
2
O
CaO BaO Total
1
Bo1
78.0
0.0
0.0
0.1
0.4
8.4
0.0
86.9
2
Bo1
77.6
0.0
0.0
0.2
0.3
8.6
0.0
86.7
3
HS1
83.0
0.4
0.5
0.2
1.2
5.1
0.0
90.4
4
HS1
82.3
0.6
0.5
0.3
1.2
4.9
0.0
89.8
5
HS1
80.0
2.5
0.0
0.6
1.1
4.5
0.0
88.7
No Sample Mn
+4
Fe
+3
Mg
Si
K
Ca
Ba
Total
1
Bo1
3.218 0.000 0.000 0.006 0.031 0.537 0.000 3.792
2
Bo1
3.207 0.000 0.000 0.012 0.023 0.551 0.000 3.793
3
HS1
3.277 0.017 0.043 0.011 0.087 0.312 0.000 3.747
4
HS1
3.269 0.026 0.043 0.017 0.088 0.302 0.000 3.745
5
HS1
3.222 0.110 0.000 0.035 0.082 0.281 0.000 3.729
Table 3: Chemical composition of todorokite (wt. % of oxides and
atomic proportion of elements O=7).
Fig. 6. Si/Al plot in the studied manganese ore and limestone.
Fig. 8. REE distribution in the studied manganese hardgrounds
(Hru-1k Hruové, Cht-1 Chtelnica and Vr-4 Vratec).
Fig. 7. Contents of Co+Cu+Ni in: Bo Boleov, Bz Bzince pod
Javorinou, Hru Hruové, HS Horné Sànie, Cht Chtelnica,
Ka Kamenica, Mi Mikuovce and Vr Vratec compared to
average content in Jurassic shale (shale).
324 ROJKOVIÈ, AUBRECHT and MIÍK
Sample
Bo1
Bo2
Bz1
Hru1a
Hru1k
Hru2
HS1
Cht1
Cht5
Ja1
Ka1
Vr1
Vr4
SiO
2
1.82
3.92
3.65
3.20
5.62
2.72
1.43
5.65
4.80
3.72
8.44
4.55
0.71
Al
2
O
3
0.95
2.32
3.23
0.72
1.60
0.57
0.80
2.65
2.59
1.07
3.18
3.71
0.78
FeO
0.09
1.47
0.12
Fe
2
O
3
*
0.63
5.19
28.98
4.55
3.18
7.85
1.86
10.99
10.76
0.73
2.12
11.03
9.31
MnO
48.08
9.15
3.31
0.41
43.68
0.88
4.97
14.23
23.25
1.41
3.17
12.21
12.61
MgO
1.36
2.31
0.90
0.44
0.05
0.58
0.45
0.81
0.78
0.61
0.92
1.49
0.52
CaO
23.69
43.11
30.73
51.47
23.96
50.33
49.87
34.08
31.07
52.98
45.47
35.19
44.38
Na
2
O
0.21
0.20
0.11
0.01
0.20
0.05
0.13
0.03
0.09
0.13
0.10
0.10
0.06
K
2
O
0.10
1.06
0.32
0.25
0.37
0.63
0.32
0.70
0.96
0.76
2.22
0.76
0.39
TiO
2
0.09
0.11
0.12
0.04
0.14
0.05
0.06
0.29
0.24
0.05
0.13
0.25
0.15
H
2
O-
0.25
0.48
0.61
0.04
0.44
0.04
0.28
0.43
0.44
0.16
0.40
0.19
0.06
LOI
22.25
31.54
27.68
38.57
20.44
35.94
39.52
28.13
24.51
37.88
33.42
30.08
30.80
P
2
O
5
0.14
0.71
0.20
0.19
0.21
0.33
0.16
0.16
0.10
0.79
Total
99.66
99.38
100.35
99.92
99.87
99.64
99.90
99.80
99.66
99.66
99.66
100.48
99.76
B
19
25
154
26
107
21
17
69
79
16
32
55
27
Ba
132
40
92
51
2127
73
222
448
1189
938
630
3100
>3000
Co
155
449
424
46
498
70
177
491
343
19
155
861
362
Cr
4
<3
34
3
2
3
2
9
10
8
9
4
<3
Cu
93
18
300
38
657
40
77
>3000
412
17
269
452
126
Ni
264
400
1342
119
300
114
396
980
881
48
758
2019
446
Pb
39
171
131
64
1100
101
173
187
232
52
50
669
615
Sr
182
271
56
113
244
106
270
252
292
391
105
412
>500
V
28
62
337
38
91
24
34
148
130
32
110
211
148
TC%
11.33
8.65
2.73
11.08
3.98
10.87
10.70
6.53
6.02
9.78
8.26
7.20
9.05
TOC%
0.96
0.08
traces
0.98
0.07
0.10
0.07
0.18
traces
traces
0.10
traces
0.12
TIC%
10.37
8.57
2.73
10.1
0
3.91
10.77
10.63
6.53
6.02
9.78
8.16
7.20
8.93
Locality: Bo Boleov, Bz Bzince pod Javorinou, Hru Hruové, HS Horné Srnie, Cht Chtelnica, Ja Jarabina, Ka Kamenica, and Vr Vratec. Fe
2
O
3
*
total iron if FeO is missing.
Table 4: Chemical composition of manganese ores and limestones.
Discussion
The Jurassic manganese crusts and nodules mostly corre-
spond to the recent submarine hardgrounds. They were mostly
formed on seamounts or other isolated places with low sedi-
mentation rates, and they show association of bacterial stro-
matolites and sessile foraminifers (Jenkyns 1970; Roy 1980;
Ballarini et al. 1994; Dromart et al. 1994). Manganese crusts
accumulate on submarine seamounts and plateaus at depths
>1000 m where bottom currents prevent sediment accumula-
tion and growth occurs mainly at the sediment/water interface
(Glasby 2000).
There are three principal modes of formation of the manga-
nese crusts and nodules: hydrogenetic, diagenetic and hydro-
thermal. Hydrogenetic deposits form directly from seawater in
an oxidizing environment (Glasby 2000). They are character-
ized by slow growth (about 2 mm 10
6
yr
1
) (Glasby 2000).
MnHru-1k
MnCht-1
MnVr-4
La
108.00
68.00
122.00
Ce
1295.00
526.00
960.00
Pr
16.00
12.00
20.00
Nd
93.00
54.00
96.00
Sm
25.00
13.00
20.00
Eu
5.50
2.70
4.00
Gd
15.60
13.50
19.90
Tb
2.00
1.70
2.40
Dy
7.60
11.10
15.90
Ho
2.40
2.50
3.90
Er
2.00
5.40
7.10
Tm
0.50
0.90
1.20
Yb
5.90
5.80
6.60
Lu
0.23
0.95
1.03
Table 5: REE in manganese ore (in ppm).
The hydrogenetic nodules were formed by precipitation from
the sea-water (with possible bacterial mediation) and their
growth also comprehends early diagenetic formation (Bonatti
et al. 1972).
A colloid-chemical model for the hydrogenetic precipita-
tion of ferromanganese crusts on seamounts was proposed
(Koschinsky & Halbach 1995). However the types of re-
actions that occur in the water column and at the precipitation
surface are poorly known. (Hein et al. 1997). In the first
stage Mn
2+
-rich water from the oxygen minimum zone is
mixed with oxygen-rich deep-water, and oxidized Mn(IV)
and other metals like Fe, Ti, Al, and Si form oxide and hy-
droxide colloids phase (Koschinsky & Halbach 1995). These
form mixed colloidal phases and scavenage trace metals by
sorptive processes which are dominated by coulombic and
chemical interactions between colloidal surfaces and dis-
solved metal species phase (Koschinsky & Halbach 1995).
Co, Ni and Cu are present in seawater mainly as hydrated and
labile complexed cations phase (Koschinsky & Halbach
1995). The manganese colloidal phases scavenge these hy-
drated cations via adsorption to the negatively charged surface
of manganese oxides and anions (Hein et al. 1997). Elements
forming carbonate and hydroxide complexes and oxyanions
in seawater like Pb, Mo, V are bound to the slightly positive
charge of the iron hydroxide surfaces (Koschinsky & Halbach
1995; Hein et al. 1997). Ti mainly forms a hydrogenetic
phase, probably consisting of TiO
2
·2H
2
O intergrown with the
amorphous FeOOH phase (Koschinsky & Halbach 1995). In
the second stage, the colloidal phases precipitate on the sub-
strate rocks of the seamounts as ferromanganese oxide encrus-
tations, incorporating the sorbed heavy metals into the miner-
al phases (Koschinsky & Halbach 1995).
MANGANESE HARDGROUNDS IN LIMESTONES OF THE WESTERN CARPATHIANS 325
Diagenetic deposits result from diagenetic processes within
the underlying sediments leading to upward supply of ele-
ments from the sediment column and they are characterized
by faster growth rates (10100 mm 10
6
yr
1
, Glasby 2000).
Metals supplied by upward diffusion from deeper reducing
parts of sediments are precipitated close to the sediment/water
interface. Transport of metal in the ionic form (e.g. Mn
2+
,
Ni
2+
, Cu
2+
, Zn
2+
) is typical for early-diagenetic growth (Hal-
bach et al. 1981). The intensity of early diagenetic processes
depends on the sufficiency of organic matter or on the biologi-
cal productivity in the water column (Halbach et al. 1981).
Surficial diagenesis is a significant source of metals to manga-
nese nodules in siliceous ooze areas, where metals are sup-
plied by organic matter through the water column and release
of metals at the seafloor (Müller et al. 1988).
Hydrothermal deposits precipitate directly from hydrother-
mal solutions in areas with high heat flow such as mid-ocean
ridges, back-arc basins and hot spot volcanoes (Glasby 2000).
They are characterized by high to extremely high growth rates
(>1000 mm 10
6
yr
1
) and low, to very low trace element con-
tents (Glasby 2000). They tend to be associated with hydro-
thermal sulphide deposits and iron oxihydroxide crusts (Glas-
by 2000). The important source of manganese in the pelagic
environment is often related to hydrothermal activity associat-
ed with global tectonic processes (Corbin et al. 2000). Volca-
no-sedimentary manganese deposits associated with cherts are
closely related to juvenile solutions of basalts. For example,
the sediments with Fe accumulation of submarine hydrother-
mal origin in the Tyrrhenian Sea contain 12.2 to 45 % of Fe
and low contents of Mn, Cu, Zn, Ni and Co, suggesting hy-
drothermal origin (Savelli et al. 1999).
The chemical composition of the Tethyan Jurassic nodules
with fine lamination of Fe-Mn oxides is variable and, similar-
ly, crusts (2 to 5 mm rarely up to 2 cm thick) show changing
Mn/Fe ratios (Cronan et al. 1999). The colloidal chemical
model enables us to compare the chemical composition of the
studied manganese crusts and nodules with data from cores
and nodules of the recent oceans. Manganese nodules in the
Pacific Ocean have been formed as a result of diagenetic
growth from pore waters, or by hydrogenetic growth from
bottom waters (Halbach et al. 1981). Fe-poor todorokite is
typical for early diagenetic nodules, while
α
-MnO
2
, inter-
grown with FeOOH×H
2
O, is formed by hydrogenetic growth
(Halbach et al. 1981).
Zoned alternation of the studied manganese oxides and hy-
droxides with iron hydroxides and calcite is dominant and in-
dicates hydrogenetic accumulation of Fe-Mn hydroxides and
oxides in the crusts and nodules. Fe-Mn crusts that occur on
most seamounts in the ocean basins have a mean Fe-Mn ratio
of 0.7 for open ocean seamount crusts and 1.2 for continental
margin seamont crusts (Hein et al. 1997). The Fe/Mn ratio in
the studied manganese crusts and nodules range from 0.3 to
0.8. Hydrothermal manganese crusts in the recent oceans are
characterized by high Mn/Fe ratios (from 10 to 4670 Glas-
by 2000). Increased content of Fe, Co, Ti and Mn/Fe ratios
lower than 2.5 are typical for hydrogenetic nodules (Halbach
et al. 1981). The studied hardgrounds and nodules show Mn/Fe
ratios from 1 to 4. This ratio is distinctly higher in a younger
supergene mineralization, where Mn/Fe = 32 (Miík & Roj-
koviè 2002). The high-grade manganese ores, with high Mn/
Fe ratio, correspond to supergene accumulation.
Manganese nodules formed in oxic environments are en-
riched in Ni, Co, Cu and other elements. The presumed source
of Co, Ni and Cu in manganese ores are weathered mafic and
ultramafic rocks on land (Fan et al. 1999). The average con-
tent of the elements in manganese nodules varies in the range
of 1114 % Mn, 6.220 % Fe, 0.161.1 % Ni, 0.171.8 %
Cu, 0.010.7 % Co, and 0.050.25 % Pb (Schweisfurth
1971). Ni, Mo, Cu, Co and Zn are bound to Mn, whereas Ti,
V and Cr are associated with Fe (Goodell et al. 1971). The di-
agenetic nodules rich in Ni and Cu are concentrated in deeper
parts of the sea, below zones of weak to moderate biological
activity (Halbach et al. 1981). Hydrothermal manganese
crusts in the recent oceans are characterized by low contents
of Cu (20 to 1000), Ni (1 to 1403), Zn (1 to 1233), Co (6 to
209) Pb (0 to 93 ppm) and detrital silicate minerals (Glasby
2000).
The increased contents of Ni, Co, Cu, as well as Fe/Mn and
Si/Al ratios in the studied samples indicate the hydrogenetic
to diagenetic origin of the studied ores (Figs. 6, 7).
Ce distribution is closely linked to the redox cycling of
manganese (Palumbo et al. 2001). Chondrite-normalized REE
patterns generally show a positive Ce anomaly and abundant
Σ
REE for hydrogenetic and mixed hydrogenetic-diagenetic
deposits, whereas the Ce anomaly is negative for hydrother-
mal deposits and
Σ
REE contents are low (Matsumoto et al.
1985; Hein et al. 1997; Usui et al. 1997; Kuhn et al. 1998).
Positive Ce anomalies in the distribution patterns reveal pref-
erential uptake of Ce especially in normal hydrogenetic crusts
(Kuhn et al. 1998). Oxidative uptake of Ce and Co by fast
sinking large biogenic particles can more effectively convey
nutrient-type metals involved with them to the sea floor be-
cause of their shorter residence time in oxic water (Ohta et al.
1999). Ce/La ratios of the nodules can be used as redox indi-
cators to trace the oxygen content of the ambient water mass
and the flow path (Kasten et al. 1998).
REE distribution in the studied manganese crusts with
slightly dominant LREE and distinct positive Ce anomaly
corresponds to hydrogenetic to diagenetic origin and it does
not indicate the presence of a volcanic source for the forma-
tion of the studied manganese mineralization (Fig. 8). More-
over, Jurassic volcanic rocks have not been found in the stud-
ied area and distant volcanism in the Meliata Ocean had a
mafic to ultramafic character with different REE distribution.
Hydrothermal crust La/Ce ratios are similar to sea water La/Ce
ratio 2.8 and all other deposits are enriched in Ce relative to
sea-water approaching an apparent lower limit of La/Ce ~0.25
(Toth 1980). La/Ce ratios in our samples ranging from 0.08 to
0.13 are very different from crusts of hydrothermal origin
which are close to ratio 2.8 of the sea-water.
The average content of organic carbon in deep ocean nod-
ules is 0.17 %, while on the continental shelf forms it is about
2.1 % (Manheim 1965). The average organic carbon content
in the studied samples is 0.20 wt. %.
Association of the studied manganese mineralization with
microstromatolites is distinct and we have to take into account
a role of microorganisms in manganese deposition. Present-
day submarine hardgrounds are developed in places of pe-
326 ROJKOVIÈ, AUBRECHT and MIÍK
lagic and hemipelagic oozes (cf. hardground near Barbados,
Roy 1980). Encrusting bryozoa and worm tubes at the surface
and foraminifers, sponge spicules and manganiferous nodules
with corals, coccoliths and calcareous serpulid tubes have
been reported from the Pacific Ocean (Roy 1980).
Various living or dead microorganisms as bacteria, algae,
mosses, fungi etc. played a particularly great ore-generating
role in the formation of ancient deposits of manganese. Their
geochemical activities, including transporting action were as-
sociated with the physiologícal processes of manganese ex-
traction from solutions, its oxidation and concentration in, and
around, plant cells (Serdyuchenko 1980). Some microorgan-
isms corresponding to ultra-microfossils reported by Zhang et
al. (1997) can also be considered as constructors of the pelag-
ic manganese nodules. Mn
+4
is probably the primary product
of bacterial Mn
+2
oxidation spores of the marine Bacillus
(Bargar et al. 2000). The microbes change the conditions of
oxidation and reduction in the system, and their effect on the
element precipitation is much stronger than the chemical ac-
tions and accelerates the enrichment of Fe and Mn (Yan et al.
1999). After the death of the microbes, their bodies are accu-
mulated on the sediment/seawater interface and form polyme-
tallic nodules. On the walls of some mineralized microbial
cells there are sheaths of Fe and Mn oxides (Yan et al. 1999).
Microbial Mn oxidation is a ubiquitous process in oxygenated
marine environments (Moffett 1997). Diagenetic ferromanga-
nese nodules in an oxic deep-sea sedimentary environment
grew from remobilized metal ions as well as reprecipitated
Mn-oxide grains, which were supplied to the nodules episodi-
cally during the stirring of bottom sediments by benthic fauna
and intermittent strong bottom current flow (Jung & Lee
1999). Post-depositional modifications of the nodules can be
controlled by accreted biogenic remains as indicated by their
progressive dissolution with increasing depth from nodule
surfaces, their pseudomorphic replacement by todorokite and
the later growth of phillipsite and todorokite in the microfossil
molds (Banerjee et al. 1999).
The manganese hardgrounds of small extent examined in
this study, occurring in the Pieniny Klippen Belt (mainly at
the base of the Czorzstyn Limestone), represent sediments of
pelagic up to shallow neritic marine facies (Fig. 9) with abun-
dant remnants of ammonites (Andrusov et al. 1955). They are
very often associated with microstromatolites.
Manganese mineralization filling the fissures and cavities
represents later supergene mobilization and oxidation by me-
teoric waters (Mikuovce). Manganese ores in these places
show higher Mn/Fe ratio than the Fe-Mn crusts (Miík &
Rojkoviè 2002). The secondary high-grade ore was formed in
fissures and cavities by meteoric water transport from the
manganese hardgrounds of dissolved Callovian-Oxfordian
red limestone during the BarremianAptian time.
Conclusions
The manganese hardgrounds of small extent examined in
this study, occurring both, in the Pieniny Klippen Belt (main-
ly at the base of the Czorzstyn Limestone) and in the Central
Western Carpathians (Nedzov Nappe), represent sediments of
pelagic up to shallow neritic marine facies with abundant rem-
nants of ammonites.
Manganese-iron crusts and nodules in the Jurassic lime-
stones in the studied area of the Western Carpathians corre-
spond to the recent submarine hardgrounds. They are repre-
sented by pyrolusite, romanèchite, manganite, todorokite and
goethite. Zoned alternation of the studied manganese oxides
and hydroxides with iron hydroxides and calcite is dominant
and indicates hydrogenetic accumulation.
The increased contents of Ni, Cu, Co (up to 0.5 wt. %), as
well as Mn/Fe ratios (1 to 4) and Si/Al ratios, indicate the hy-
drogenetic to diagenetic origin of the studied ores. Fe/Mn ra-
tios in the studied manganese crusts and nodules (0.3 to 0.8)
are closer to the recent open ocean seamount crusts than to the
continental margin seamont crusts. The average organic car-
bon content in the studied samples (0.20 wt. %) is also closer
to the deep ocean nodules than to the continental shelf forms.
REE distribution in the studied manganese crusts with dis-
tinct positive Ce anomaly corresponds to hydrogenetic to di-
Fig. 9. Model of Jurassic manganese hardground formation in a
transgressive oceanic regime. A rapid sea-level rise resulted in
drowning of the shallow-water carbonate platform and in succeed-
ing starvation of the sedimentary area. The latter, together with bot-
tom currents with increased CO
2
contents resulted in formation of
omission surfaces and hardgrounds. A condensed sedimentation of
Ammonitico Rosso limestones followed afterwards.
MANGANESE HARDGROUNDS IN LIMESTONES OF THE WESTERN CARPATHIANS 327
agenetic origin and it does not indicate the presence of a vol-
canic source for the formation of the studied manganese min-
eralization.
Association of the studied manganese mineralization with
microstromatolites is distinct and we have to take into account
the role of microorganisms in manganese deposition.
The younger manganese mineralization, filling fissures and
cavities, consist of dominant manganite and pyrolusite. It rep-
resents later supergene mobilization and oxidation by meteor-
ic waters. Manganese ores in these places show higher Mn/Fe
ratio than the Mn-Fe crusts. This high-grade ore was formed
by meteoric water transport from the manganese hardgrounds
of dissolved Callovian-Oxfordian red limestone during the
BarremianAptian time.
Acknowledgments: The study was supported by Grants 160
of VTP GP and 1/7293/20 of VEGA. Critical comments of
the reviewers S. Kasten (Universität Brehmen), K.P. Krajews-
ki (ING PAN Warszawa, Poland), and J. Soták (SAV Banská
Bystrica, Slovakia) significantly helped to improve the manu-
script. We thank ¼. Pukelová (Geological Institute of the Slo-
vak Academy of Sciences) for the analyses of a part of rocks
and minerals and D. Ozdín (Geological Survey of the Slovak
Republic).
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