GeolCarp_Vol66_No4_303

www.geologicacarpathica.com

GEOL

EOL

EOLOGICA CARPA

OGICA CARPA

OGICA CARPATHICA

THICA

, AUGUST 2015, 66, 4, 303—310 doi: 10.1515/geoca-2015-0027

Introduction

When studying the mineralogy of the products of weathering
of bedded sideritic mudstones in the Czech part of the Mora-
vian-Silesian Beskydy Mountains (Fig. 1) some microparti-
cles consisting of native selenium were detected in fissures of
these sediments. Native selenium is a relatively rare mineral
that is bound by its origin mainly to the oxidation of Se-rich
organic matter in sandstones of uranium and uranium-vanadi-
um mineral deposits, to the sublimation products of volcanic
fumaroles and to gaseous products of burning heaps from coal
mining (Anthony et al. 1990; Jianming et al. 2004). The min-
eral is trigonal trapezohedral with space group P3

21 or P3

(Anthony  et  al.  1990).  It  usually  forms  opaque  needle-like
crystals. Selenium is an essential biogenic microelement that
shows considerable toxicity at only slightly higher concentra-
tions.  Its  geochemical  behaviour  in  the  geosphere  has  been
summarized  by  Malisa  (2001),  Plant  (2013),  and  in  soil  by
Strawn et al. (2002) and by Tolu et al. (2014).

The occurrence of native selenium in common sedimentary

sequences is an interesting finding that requires clarification
of the conditions controlling its formation. If a more com-
mon occurrence of this mineral is proved, then models of the
geochemical behaviour and character of selenium in the pro-
cess of weathering will have to be modified and the possibil-
ity of its accumulation in the form of Se(0) needs to be taken
into account.

There is only minimal data in the literature on the occur-

rence of native Se in sedimentary sequences or about its ori-

The origin of native selenium microparticles during the

oxidation of sideritic mudstones in the Veřovice Formation

(Outer Western Carpathians)

DALIBOR MATÝSEK and PETR SKUPIEN

Institute of Geological Engineering, VŠB – Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava-Poruba,

Czech Republic; dalibor.matysek@vsb.cz; petr.skupien@vsb.cz

(Manuscript received December 1, 2014;

accepted in revised form June 23, 2015)

Abstract: Microparticles of native selenium were detected in weathered sideritic mudstones of the Veřovice Formation
(Aptian) of the Silesian Unit (Outer Western Carpatians, NE part of the Czech Republic). This mineral forms small
needle-like crystals with lengths of up to 20 µm, and is confined to fissures in sideritic mudstones covered by goethite
or rarely also by hydrated Mn-oxide minerals. The oxidized sideritic mudstones show zonal structure and resemble the
initial stage of the formation of the so-called rattle stones. From the superposition of phase diagrams of selenium and
Fe-oxyhydroxides, Fe apparently occupies a large field in which Se(0) and FeOOH and/or Fe(OH)

can co-exist. The

reduction of selenites or selenates by pyrite or by any other phase, capable of charge transfer, is likely to have been
responsible for the formation of microparticles of native selenium. The crucial factor controlling the origin of these
particles is the extremely low solubility of Se(0). The source of Se is not obvious. It can be released in trace concentra-
tions during the weathering of pyrite. Sediments of the Veřovice Formation correspond to the anoxic event OAE1b and
accumulation of siderophile elements in similar sediments is very probable. A probable mechanism for the origin of
Se microcrystals is gradual crystallization from solution.

Key words: Western Carpathians, Lower Cretaceous, sideritic mudstones, native selenium.

gin during the process of weathering. In the area of the West-
ern Carpathians there is only one reference to the occurrence
of  microparticles  of  selenium  sitting  on  a  crystal  of  pyrite
(Szełęg  et  al.  2013).  Here  selenium  forms  needle-like  crys-
tals with a maximum length of 30 µm growing together with
barite on a (001) crystal plane of partly oxidized pyrite about
4 mm in size. This occurrence comes from low-temperature
hydrothermal veins of the Godula Formation of the Silesian
Unit  (Senonian).  The  aim  of  the  paper  is  to  document  two
new occurrences of native selenium in sideritic mudstones of
the  Veřovice  Formation,  Outer  Western  Carpathians  and  to
discuss their origin.

Methods of investigation

The crystals of selenium were identified during a brief

study  of  the  products  of  weathering  of  sideritic  mudstones
using electron microscopy and energy dispersive microanaly-
sis  carried  out  on  untreated  flat  samples.  The  nature  of  the
crystals does not allow preparation of polished thin sections
or their metal coating using the sputtering process in a plasma
environment. It was also found that, when carrying out elec-
tron  probe  microanalyses,  some  damage  to  analysed  grains
may occur including their burning through, which leads dur-
ing  the  analysis  to  a  gradual  increase  in  the  content  of  ele-
ments  originating  from  the  substrate,  which  may  not  be
present in the analysed grains. These mainly include the con-
tents of oxygen and iron and/or manganese. A typical EDX

304

MATÝSEK and SKUPIEN

GEOL

EOL

EOLOGICA CARPA

OGICA CARPA

OGICA CARPATHICA

THICA

THICA, 2015, 66, 4, 303—310

(Energy Dispersive X-ray Spectroscopy) spectrum of sele-
nium particles is shown in Fig. 2. Therefore, the only avail-
able solution is to minimize the time needed to carry out the
EDX analysis. The WDA analyses (Wave dispersion) do not
provide reliable results. The crystals of selenium can be re-
moved by simple washing of the samples.

The electron microscopy and EDX microanalyses were per-

formed on a FEI Quanta-650 FEG instrument equipped with

EDAX  detectors  –  EDAX  Galaxy,  WDA—EDAX  LEXS,
EBSD—EDAX TSL and CL – Gatan MonoCL4. The energy
dispersive  microanalysis  carried  out  under  the  above  condi-
tions must be considered only semi-quantitative. Only simple
analyses without using appropriate standards were carried out
but  applying  correction  of  the  contents  of  light  elements  on
the  basis  of  a  set  of  standard  materials  under  the  following
conditions: voltage 15 kV, current of 8—10 nA, beam diameter

Fig. 2. A characteristic EDX spectrum taken on the crystal plane of a selenium particle. In addition to the dominant lines of Se, lines of Fe,
Mn, Ca and O are also present, which come from the substrate of the crystal. Locality 2 (Soběšovice).

Fig. 1. A – Tectonic map of the Outer Western Carpathian area of the Czech Republic with localities, B – Location of the discoveries of
the native selenium: locality 1 – Kunčice pod Ondřejníkem, locality 2 – Soběšovice.

305

Se MICROPARTICLES IN SIDERITIC MUDSTONES, VEŘOVICE FORMATION (OUTER W CARPATHIANS)

GEOL

EOL

EOLOGICA CARPA

OGICA CARPA

OGICA CARPATHICA

THICA

THICA, 2015, 66, 4, 303—310

5.5 µm, reduced pressure in the vacuum chamber 50 Pa, sam-
ples without coating.

Powder X-ray diffraction analyses were carried out to char-

acterize the overall composition of the samples and to identify
the products of weathering of sideritic mudstones. Analyses
were made on a Bruker-AXS D8 Advance instrument with
2

θ/θ reflection geometry measurements, equipped with a

semiconductor – silicon strip detector- model LynxEye. Mea-
surements were carried out under the following conditions: ra-
diation CoK

α/Fe, voltage 40 kV, current 40 mA, step mode

with a step of 0.014 2

θ, time at step 0.25 sec., summation of

3—5 measurements, the angle range 5—80° 2

θ. Software Bru-

ker – AXS Diffrac or Diffrac. EVA and database of diffrac-
tion  data  PDF  2/JCPDS,  version  2011  were  used  for  the
measurements and qualitative evaluation of the obtained val-
ues. A semi-quantitative evaluation was performed by means
of  the  Rietveld  method  and  using  the  program  TOPAS,  ver-
sion 4.2. Input structural data were taken from the Bruker Struc-
tural  Database.  Both  electron  microscopy  and  XRD  analysis

were performed in the laboratories of Institute of Clean Tech-
nologies for Mining and Utilization of Raw Material for Energy
Use (VŠB-TU Ostrava, Faculty of Mining and Geology).

Geological setting and description of the identified

mineralization

Microparticles of selenium were found at two localities

(Fig. 1). Locality 1 lies in the cadastre of the Kunčice pod On-
dřejníkem  village  (GPS 49°32’46.313” N,  18°16’33.461” E)
and is represented by the NE wall of an abandoned and par-
tially  flooded  quarry  (Fig. 1).  Locality 2  is  situated  on  the
cadastral  boundary  of  the  municipalities  of  Lučina  and
Soběšovice (GPS 49°43’18.012” N, 18°27’53.240” E). This
is a flat outcrop on the beach of the Žermanice dam (Fig. 1)
only exposed at low water levels.

Both studied localities represent outcrops which by micro-

fossil dating belong to the Veřovice Formation of the Sile-

Fig. 3. Morphology of selenium crystals on the surface of fissures in slightly weathered sideritic mudstones. BSE images. A, B – Locality
Kunčice pod Ondřejníkem, C, D – Locality Soběšovice.

306

MATÝSEK and SKUPIEN

GEOL

EOL

EOLOGICA CARPA

OGICA CARPA

OGICA CARPATHICA

THICA

THICA, 2015, 66, 4, 303—310

sian  Unit  affected  by  weathering  in  the  deeper  parts  of  the
soil profile. There are black and grey, usually strongly silici-
fied aleurites and pelites with accessoric proportion of beds
of sideritic mudstones or sandstones. Judging from the iden-
tified non-calcareous dinoflagellates, the local sediments are
of Aptian age (pers. obs. Skupien) or more accurately belong
to  the  latest  Aptian.  Sediments  of  the  Veřovice  Formation
are  characterized  by  their  non-calcareous  nature,  but  other-
wise are rich in organic carbon (TOC 2—3.5 wt. % – Pavluš
& Skupien 2014). The conditions during sedimentation can be
associated with an anoxic environment, and the Veřovice For-
mation can be correlated with the oceanic anoxic event desig-
nated as OAE1b (Skupien et al. 2013; Kaim et al. 2013).

Samples at both localities were taken from a depth of

about  1.5—2 m  below  the  present  surface.  The  exposed  sec-
tion at both sites is very similar. It consists of isolated beds
of  sideritic  mudstone  10—20 cm  thick,  enclosed  in  black-
grey,  crispy  aleurites  and  pellites  that  disintegrated  into
blocks or cubes. The beds of mudstones were tectonically seg-
mented  into  polygonal,  generally  wedge-shaped  fragments
of a size of 20

×20 cm. These sediments suffered from strong

weathering along the primary jointing that is manifested by a
significant concentric structure of the fragments.

Results

Microparticles of native selenium identified by EDX spectra

(Fig. 2) occur in the form of very thin, needle-like crystals and
their aggregates on the surface of fissures in weathered sid-
eritic mudstones. The crystals always occur on a coating
formed by oxyhydroxides of Fe (goethite), and also rarely as

at  locality 2  (Soběšovice),  on  thin  lamellar  coatings  of  hy-
drated  Mn-oxide  minerals.  Needles  of  selenium  occur  either
as isolated crystals or are intergrown to form bundles and ag-
gregates (Fig. 3). Only rarely is it possible to observe signs of
hexagonal crystal planes. The crystals are rarely 20 µm long,
but  usually  are  max.  5 µm  in  size.  The  thickness  of  crystals
ranges in general in tenths of a micrometer, max. 0.5—1 µm.

Associated minerals in mudstone fissures

Microparticles of selenium in the fissures of sideritic mud-

stones  at  both  localities  are  associated  with  goethite  forming
coatings consisting of irregularly lobated particles, fibres and
needle-like  crystals.  At  Kunčice  pod  Ondřejníkem  relatively
abundant  barite  occurs  in  the  form  of  tabular  crystals  up  to
2 µm in size (Fig. 4A). Rare black, highly vitreous coatings of
lepidocrocite  form  of  prismatic  crystals  have  max.  5 µm
(Fig. 4B).  Hydrated  Mn  oxide  minerals,  specifically  todoro-
kite and lithiophorite (Fig. 4C) were identified in separate fis-
sures.  Todorokite  forms  coatings  comprising  intergrowths  of
extremely thin tabular crystals, whereas lithiophorite occurs as
globular  aggregates  consisting  of  oriented  intergrowths  of
pseudohexagonal  tabular  crystals  and  was  found  only  rarely.
Both hydrated oxide minerals of Mn and Fe, as well as lepi-
docrocite were detected and proved by powder X-ray diffrac-
tion.  The  main  diffraction  lines  and  refined  cell  dimensions
for hydrated Mn-oxide minerals are shown in Table 1.

EDX microanalysis of the lithiophorite [(Al, Li)Mn

(OH)

]

displays a high content of Al. With regard to the fact that elec-
tron microanalysis does not allow the determination of Li, one
cannot comment more closely on the content and behaviour of

Lithiophorite — Kunčice p. Ondřejníkem locality

Diffraction lines (hkl – d [nm]): (003) – 0. 9483; (006) – 0.7417; (009) – 0.31611; (00–12) – 0.5496; (00–15) – 0.1897
Refined cell parameters: a

= 0.29275(35) nm, c

= 2.8450(10) nm

Published cell parameters for comparison (Post & Appleman 1994): a

= 0.29247(4), c

= 2.8169(6) nm

Todorokite — Kunčice p. Ondřejníkem locality

Diffraction lines (hkl – d [nm]): (100) – 1.05169; (001) – 0.94812; (002) – 0.47406; (003) – 0.31604
Refined cell parameters: a

= 1.0055(5), b

= 0.2723(11), c

= 0.9511(14) nm, β = 94.53(33)

Published cell parameters for comparison (Post et al. 2003): a

= 0.9769, b

= 0.28512, c

= 0.9560 nm, β = 94.47

Manganite — Soběšovice locality

Diffraction lines (hkl – d [nm]): (1–1–1) – 0.34077; (020) – 0.2397; (111) – 0.25243; (200) – 0.24162; (1–2–1) – 0.22718; (022) – 0.17822
Refined cell parameters (in space group P2

/c): a

= 0.53071(33), b

= 0.52794(7), c

= 0.53071(60) nm, β = 114.42(16)

Published cell parameters for comparison (PDF 60-041-1379, P2

/c): a

= 0.5300, b

= 0.5278, c

= 0.5307 nm, β = 114.36(16)

Pyrolusite — Soběšovice locality

Diffraction lines (hkl – d [nm]): (110) – 0.31211; (011) – 0.24032; (020) – 0.22070; (211) – 0.16255
Refined cell parameters: a

= 0.4414(2), c

= 0.2865(4) nm

Published cell parameters for comparison (PDF 00-024-0735): a

= 0.4399, c

= 0.2874 nm

Lepidocrocite — Kunčice p. Ondřejníkem locality

Diffraction lines (hkl – d [nm]): (020) – 0.62611; (021) – 0.32934; (130) – 0.24725, (150) – 0.19403; (151) – 0.17347
Refined cell parameters: a

= 0.306886(7), b

= 1.25221(3), c

= 0.38724(1) nm

Published cell parameters for comparison (PDF 01-070-8045): a

= 0.3072, b

= 1.2516, c

= 0.388 nm

Goethite — Kunčice p. Ondřejníkem locality

Diffraction lines (hkl – d [nm]): (101) – 0.41805; (301) – 0.26925; (210) – 0.25822; (111) – 0.24482; (211) – 0.22524 nm
Refined cell parameters: a

= 0.9955(2), b

= 0.30204(5), c

= 0.46063(8) nm

Published cell parameters for comparison (Yang et al. 2006): a

= 0.9951, b

= 0.30178, c

= 0.45979 nm

Table 1: Main diffraction lines and refined cell dimensions of manganese and iron minerals from weathered sideritic mudstones.

308

MATÝSEK and SKUPIEN

GEOL

EOL

EOLOGICA CARPA

OGICA CARPA

OGICA CARPATHICA

THICA

THICA, 2015, 66, 4, 303—310

this element in the localities under study. Todorokite is char-
acterized by tunnel structures and is common as well. Diffrac-
tion records of todorokite show the limited size of diffracting
domains, and as a result of this, the broadening of diffraction
lines for this mineral (estimated domain size is 8 µm).

The EDX microanalysis also showed probable schwertman-

nite (hydrated Fe oxide mineral with elevated content of sul-
phur) and yet unspecified oxyhydroxide of Al. In the case of
locality 2  (Soběšovice)  the  association  of  secondary  oxides
and Mn oxyhydroxides (Fig. 4D) is somewhat different. Goet-
hite in the fissures is covered with relatively rare max. 50 µm
large crystals of manganite (Fig. 4E) and pyrolusite (Fig. 4F),
and  also  abundant  coatings  composed  of  warped,  extremely
thin tabular grains. While manganite and pyrolusite were veri-
fied by powder X-ray diffraction analysis, coatings consisting
of tabular grains are likely to be amorphous. Considering the
elevated  Ca  content  in  EDX  microanalyses  it  is  possible  to
speculate on the occurrence of ranciéite.

Oxidation alterations in sideritic mudstones

Within the clasts of weathered mudstones, three zones can

be distinguished. The outer zone is formed by a crust 1—2 cm
thick, consisting of brown, relatively massive, macroscopi-
cally slightly thin-bedded material. According to the results
of powder X-ray diffraction analysis, the major goethite is
accompanied by chlorite and quartz. Microscopically, when
compared with central parts of non-altered samples, the goet-
hite forms pseudomorphs after siderite crystals. The content
of pyrite is negligible.

The next is a 0.5—1 cm thick zone consisting of disintegrat-

ing powdery material of beige, beige-brown or reddish-brown
colour shades. This zone also comprises intergrowths of goet-
hite or hematite with an admixture of quartz, pyrite and chlorite.

The inner part of clasts is composed of unaltered matter of

sideritic mudstone. Here, the siderite prevails and is accompa-
nied by quartz. The content of chlorite and pyrite is lower than
in  the  middle  zone.  Microscopically  the  samples  of  sideritic
mudstone exhibit sparitic texture and consist of subhedral sid-
erite crystals enclosed in the matrix. This matrix, according to
the  results  of  X-ray  diffraction,  is  formed  by  chlorite  and
quartz. The latter mineral is also present as subhedral grains in
the  centre  of  siderite  crystals.  Pyrite  is  relatively  abundant.
This mineral in samples from locality 1 (Kunčice pod Ondřej-
níkem)  is  euhedral  forming  irregular  grains  up  to  50 µm  in
size, while samples from locality 2 contain framboidal pyrite.
Moreover, in samples from locality 2 (Soběšovice) thin layers
with admixture of clastic material (silty grains of quartz) can
be  observed  in  some  places.  The  powder  X-ray  diffraction
analyses of sideritic mudstones from both localities indicate a
presence  of  two  differently  substituted  siderites  (splitting  of
diffraction lines of siderite).

Discussion

The geochemical character of selenium largely resembles

that of sulphur. Its form and/or its oxidation state in the sys-

tem is determined by the pH-p

ε and/or (Eh) (De Cannière

2010). Based on the published pH-p

ε diagrams of the Se-O

system  (e.g.  Olin  et  al.  2005;  Cornelis  et  al.  2008)  selenium
may occur in four oxidation states, namely as Se(VI), Se(IV),
Se(0) and Se(-II). Selenates and selenites are usually highly
soluble  in  water  and  can  be  adsorbed  on  oxyhydroxides  of
Fe and Mn. In contrast, elemental Se(0) is characterized by
an  extremely  low  solubility.  For  instance,  using  thermody-
namic modelling with software PhreeqC (Parkhurst & Appelo
1999, 2013) and with the LLNL database, it is possible to es-
timate  the  equilibrium concentration of  10

—15

mol/l of Se(0)

in pure water, pH = 7 and p

ε=0.

The superposition of pH-p

ε diagrams of prevailing phases

of both systems (Se-O, and/or Fe-O; see Fig. 5) shows a rel-
atively large area of probable coexistence of crystalline
Se(0) and goethite or Se(0) and amorphous Fe(OH)

. This

area lies in the section of geochemically quite realistic condi-
tions (pH > 6 and pe approximately —3 to + 5). A crucial factor
responsible for the origin of Se is the maintaining of appro-
priate redox conditions, such as buffering by Fe

/Fe

ions.

Mingliang et al. (2011) refer to an interesting possibility

for the origin of native Se(0). According to these authors,
during an interaction between the solution containing seleni-

Fig. 5. Projection of pH-p

ε diagram of the Se-O system into the Fe-O

system. Data for the system Se-O were taken from Olin et al.
(2005), and apply to the total concentration of Se = 10

—6

mol. The

Fe-O  system  was  constructed  by  using  PhreeqC  and/or  Phreeplot
program  based  on  data  from  the  LLNL  thermodynamic  database
(Parkhurst & Appelo 1999, 2013; Kinninburgh & Cooper 2011) and
applies  to  the  total  concentration  of  10

—4

mol/l Fe. Fields of pre-

dominance of solid phases (crystalline Se(0)) or goethite, amor-
phous Fe(OH)

, Fe

(OH)

, and Fe

) are highlighted in both

overlapping pH-p

ε diagrams. Lines bounding the field of stability

of H

O (line H

O/H

, resp. H

O/O

) are also included.

309

Se MICROPARTICLES IN SIDERITIC MUDSTONES, VEŘOVICE FORMATION (OUTER W CARPATHIANS)

GEOL

EOL

EOLOGICA CARPA

OGICA CARPA

OGICA CARPATHICA

THICA

THICA, 2015, 66, 4, 303—310

tes with pyrite, a reduction to Se(0) takes place in laboratory
conditions. Similarly, it can also occur in some other phases
capable of electron transfer, such as siderite, some other sul-
phides of Fe, magnetite or aluminosilicates containing Fe

(Brugemann 2005; Charlet 2007; Scheinost 2008). Scheinost
& Charlet (2008) stated that the reduction of selenites or sel-
enates by green rust, pyrite and ions of Fe

absorbed on

montmorillonite  is  slow,  kinetically  limited  (reaction  that
takes  weeks);  the  reduction  of  selenites  by  mackinawite  or
magnetite  with  nanometric  size  is  very  quick  (within  one
day).  Scheinost  &  Charlet  (2008)  also  stated,  that  a  portion
of  selenites  in  solution  may  also  be  reduced  by  siderite  of
micron sizes. These authors also observed the occurrence of
different reaction products (red and grey elemental Se, FeSe
and  Fe

). On the other hand, Mitchell et al. (2013) state

that the crucial point and role in removing Se(IV) from solu-
tion in the presence of mineral phases is by adsorption, but
no change in the oxidation state of Se was observed.

Szełęg et al. (2013) ascribe the formation of selenium

crystals to bacterially induced oxidation of pyrite in a neutral
environment and connect it with the presence of biogenic fi-
brous structures (reportedly bacteria of the genus Leptothrix).
However,  this  genus  includes  strictly  aerobic,  chemoorga-
noheterotrophic  bacteria  which  induce  precipitation  of  Fe
oxyhydroxides  particularly  in  surface  waters  (Spring  2006).
Therefore, the incidence of the occurrence of native selenium
and the oxidation of pyrite with bacteria of the genus  Lepto-
thrix seem unlikely, but the bacterial influence on the origin of
native  Se  at  the  described  locality  cannot  in  general  be  ex-
cluded either (Blum et al. 1998; Biswas et al. 2011).

The primary bond of selenium in rocks of the studied lo-

calities is not obvious, because the contents of Se in relatively
abundant pyrite are below the detection limit of electron mi-
croanalysis. Literary sources state that in sedimentary rocks,
Se is bound to sulphides and/or to organic matter. For exam-
ple, Matamoros-Veloza et al. (2014) found that in shales, Se
is bound especially to euhedral pyrite, in which it isomorphi-
cally replaces sulphur. In somewhat lower contents Se was
found in framboidal pyrite as FeSe

phase.

With regard to the evidently crystalline character of selenium

in fissures, this mineral is probably not produced by interfacial
reactions between a solution and a solid phase or by direct pre-
cipitation.  For  this  reason,  the  authors  incline  to  the  opinion
that  selenium  in  the  studied  localities  is  formed  by  gradual
crystallization.  Very  probably  microcrystalline  barite,  which
was found in the locality of Kunčice pod Ondřejníkem, is a
similarly formed accompanying phase. Barite also has an ex-
tremely  limited  solubility.  It  occurs  very  abundantly  in  fis-
sures of weathered sediments (Matýsek, pers. observation).

The appearance of strongly weathered clasts of sideritic

mudstones is a reminder of the initial stage of the formation
of the so-called rattle stones (Van Loef 2000; Loope et al.
2012). This weathering structure that is relatively rare, espe-
cially in less weathered clasts of sideritic mudstone, is inter-
sected by tiny secondary fissures of which walls are covered
by thin coating of oxyhydroxides of Fe and Mn. Native sele-
nium was detected in these tiny fissures. Changes in oxida-
tion of beds of sideritic mudstones that lead to the formation
of structures similar to the so-called rattle stones can be in-

terpreted as a manifestation of acidification of siderite during
contemporaneous diffusion transport of CO

, Fe

or O

From  the  behaviour  of  siderite  in  the  process  of  sulphidic
weathering it is known that this mineral in oxidizing condi-
tions is acid-base neutral (cf. Paktunc 1999). During the con-
version  of  siderite  to  goethite  the  hydrogen  ions  in  overall
terms are not produced nor consumed. During the alteration
of  siderite  its  dissolution  takes  place  (consumption  of
2 moles  of  H

/1 mol of siderite in formation of H

). In

the subsequent oxidation of Fe

to Fe

, 1 mol H

/1 mol of

is consumed. Finally, during the hydrolysis of Fe

Fe(OH)

three moles of H

are released. Consequently, it is

obvious that when alteration or transition of siderite into goet-
hite takes place, the transport mechanisms of diffusion of H

(starting the dissolution and compensating for the losses of
acidity) are the controlling factors towards the clast, while in
the opposite direction the diffusion of O

or Fe

occurs.

Nevertheless, it should be assumed that these diffusion flows
are responsible for the formation of a concentric structure
that will be stable over time and will be in balance.

Lithiophorite, which occurs in mudstone fissures, is com-

monly found in weathered zones of Mn deposits, ocean-floor
manganese crust, some acid soils and low-temperature hy-
drothermal veins (Post & Appleman 1994; Jiang et al. 2007;
Rao et al. 2010).

Acknowledgments: The study was carried out in the frame-
work  of  the  Project  “Institute  of  clean  technologies  for  the
extraction  and  use  of  energy  resources”,  reg.  No. CZ.1.05/
2.1.00/03.0082,  supported  by  the  Operational  Program  fo-
cused  on  Research  and  Development  for  Innovation,  fi-
nanced from EU structural funds and from the state budget.
ED2.1.00/03.0082.  The  research  was  supported  by  Grant
SP2014/10 financed by the Ministry of Education, Youth and
Sports  of  the  Czech  Republic.  We  would  like  to  thank  Igor
Broska  (Bratislava,  Slovakia),  Eligiusz  Szełęg  (Sosnowiec,
Poland)  and  Pavel  Uher  (Bratislava,  Slovakia)  for  reading
the  manuscript,  which  was  significantly  improved  by  their
critical remarks.

References

Anthony J.W., Bideaux R.A., Bladh K.W. & Nichols M.C. (Eds.).

1990: Handbook of mineralogy. Volume I. Elements, Sulfides,
Sulfosalts. Mineral Data Publishing, Tuscon, Arizona, 1—813.

Biswas K.C., Barton L.L., Lok Tsui W., Shumana K., Gillespie J. &

Eze Ch.S. 2011: A novel method for the measurement of ele-
mental selenium produced by bacterial reduction of selenite. J.
Microbiol. Meth. 86, 140—144.

Blum J.S., Bindi A.B., Buzzelli J., Stols J.F. & Oremland R.S.

1998:  Bacillus  arsenioselenatis  sp.  nov.,  and  Bacillus  seleni-
tireducens  sp.  nov.:  two  haloalkaliphiles  from  Mono  Lake,
California  that  respire  oxyanions  of  selenium  and  arsenic.
Arch. Microbiol. 171, 19—30.

Bruggeman C., Maes A., Vancluysen J. & Vandemussele P. 2005:

Selenite reduction in Boom clay: Effect of FeS

, clay minerals

and dissolved organic matter. Environ. Pollut. 137, 209—221.

Charlet L., Scheinost A.C., Tournassat C., Greneche J.M., Géhin A.,

Fernández-Martínez A., Coudert S., Tisserand D. & Brendle J.
2007: Electron transfer at the mineral/water interface: Selenium

310

MATÝSEK and SKUPIEN

GEOL

EOL

EOLOGICA CARPA

OGICA CARPA

OGICA CARPATHICA

THICA

THICA, 2015, 66, 4, 303—310

reduction by ferrous iron sorbed on clay. Geochim. Cosmochim.
Acta 71, 5731—5749.

Cornelis G., Johnson C.A., Van Gerven T. & Vandecasteele C.

2008: Leaching mechanisms of oxyanionic metalloid and metal
species in alkaline solid wastes: A review. Appl. Geochem. 23,
955—976.

De Cannière P., Maes A., Williams S., Bruggeman Ch., Beauwens

T., Maes N. & Cowper M. 2010: Behaviour of selenium in
Boom clay. External report of the Belgian Nuclear Research
Centre. SCK.CEN-ER-120, 10/PDC/P-9, 1—328.

Online: http://publications.sckcen.be/dspace/
Jiang X., Lin X., Yao D., Zhai S. & Guo W. 2007: Geochemistry of

lithium in marine ferromanganese deposits. Deep Sea Research
I, 54, 85−98.

Jianming Z., Wei Z., Xiaobing L., Shehong L. & Baoshan Z. 2004:

Occurrence of native selenium in Yutangba and its environ-
mental implications. Appl. Geochem. 19, 461—467.

Kaim A., Skupien P. & Jenkins R.G. 2013: A new Lower Creta-

ceous hydrocarbon seep locality from the Czech Carpathians
and its fauna. Palaeogeogr. Palaeoclimatol. Palaeoecol. 390,
42—51.

Kinninburgh D.G. & Cooper D.M. 2011: User’s guide to Phree-

Plot – Creating graphical output with PHREEQC, 1—588.

Online: http://www.phreeplot.org/
Loope D.L., Kettler R.M., Weber K.A., Hinrichs N.L. & Burgess

D.T. 2012: Rinded iron-oxide concretions: hallmarks of altered
siderite masses of both early and late diagenetic origin. Sedimen-
tology 59, 1769—1781.

Malisa E.P. 2001: The behavior of selenium in geological processes.

Environ. Geochem. Hlth. 23, 137—158.

Matamoros-Veloza A., Peacock C.L. & Benning L.G. 2014: Sele-

nium speciation in framboidal and euhedral pyrites in shales.
Environ. Sci. Technol. 48, 8972—8979.

Mingliang K., Fanrong C., Shijun W., Yongqiang Y., Bruggeman

C. & Charlet L. 2011: Effect of pH on aqueous Se(IV) reduc-
tion by pyrite. Environ. Sci. Technol. 45, 7, 2704—2710.

Mitchell K., Couture R.-M., Johnson T.M., Mason P.R.D. & Van

Cappellen P. 2013: Selenium sorption and isotope fraction-
ation: Iron(III) oxides versus iron(II) sulfides. Chem. Geol. 342,
21—28.

Olin Å., Noläng Å., Öhman L.-O., Osadchii E. & Rosén E. 2005:

Chemical thermodynamics of selenium. Chemical Thermody-
namics Series Volume 7. Nuclear Energy Agency, Elsevier Sci-
ence, Amsterdam, 1—851.

Paktunc A.D. 1999: Mineralogical constrains on the determination

of neutralization potential and prediction of acid mine drainage.
Environmental Geol. 39, 2, 103—112.

Parkhurst D.L. & Appelo C.A.J. 1999: User’s guide to PHREEQC

(Version 2): A computer program for speciation, batch-reac-
tion, one-dimensional transport, and inverse geochemical cal-
culations. U.S. Geol. Surv.: Earth Science Information Center.
Water-Resources Investigations Report 99—4259, 1—326.

Parkhurst D.L. & Appelo C.A.J. 2013: Description of input and

examples for PHREEQC version 3-A computer program for

speciation, batch-reaction, one-dimensional transport, and in-
verse geochemical calculations: U.S. Geol. Surv. Techniq. and
Methods, Book 6, Chap. A43, 1—497.

Online: http://pubs.usgs.gov/tm/06/a43/
Pavluš J. & Skupien P. 2014: Lower Cretaceous black shales of the

Western Carpathians, Czech Republic: Palynofacies indication
of depositional environment and source potential for hydrocar-
bons. Mar. Petrol. Geol. 57, 14—24.

Plant J.A., Kinniburgh D.G., Smedley P.L., Fordyce F.M. & Klinck

B.A. 2013: Arsenic and selenium. In: Holland H.D. & Turekian
K.K. (Eds.): Treatise on geochemistry. Vol. 9.02. Elsevier,
New Orleans, 17—66.

Post J.E. & Appleman D.E. 1994: Crystal structure refinement of

lithiophorite. Amer. Mineralogist 79, 370—374.

Post J.E., Heaney P.J. & Hanson J.C. 2003: Synchrotron X-ray dif-

fraction study of the structure and dehydration behavior of
todorokite. Amer. Mineralogist 88, 142—150.

Rao D.S., Nayak B.K. & Acharya B.C. 2010: Cobalt-rich lithio-

phorite from the Precambrian Eastern Ghats manganese ore de-
posit of Nishikhal, south Orissa, India. Mineralogia 41, 1—2,
11—21.

Scheinost A.C. & Charlet L. 2008: Selenite reduction by mackinaw-

ite, magnetite and siderite: XAS characterization of nanosized
redox products. Environ. Sci. Technol. 42, 1984—1989.

Scheinost A.C., Kirsch R., Banerjee D., Fernández-Martínez A.,

Zaenker H., Funke H. & Charlet L. 2008: X-ray absorption and
photoelectron spectroscopy investigation of selenite reduction
by FeII-bearing minerals. J. Contam. Hydrol. 102, 228—245.

Skupien P., Smaržová A. & Měchová L. 2013: Palaeoenvironmental

change in the Early Cretaceous Silesian Basin of the Western
Carpathians (NE Czech Republic) inferred from palynological
data. Rev. Palaeobot. Palynol. 197, 143—151.

Spring S. 2006: The genera Leptothrix and Sphaerotilus. In: Dworkin

M., Falkow S., Rosenberg E., Schleifer K.-H. & Stackebrandt
E. (Eds.): Prokaryotes. A handbook on the biology of bacteria.
Vol. 5. Proteobacteria: Alpha and Beta Subclasses, Chapter
3.2.11. Springer, New York, 758—777.

Strawn D., Doner H., Zavarin M. & McHugo S. 2002: Microscale in-

vestigation into the geochemistry of arsenic, selenium, and iron in
soil developer in pyritic shale materials. Geoderma 108, 237—257.

Szełęg E., Janeczek J. & Metelski P. 2013: Native selenium as a

byproduct of microbial oxidation of distorted pyrite crystals:
the first occurrence in the Carpathians. Geol. Carpathica 64, 3,
231—236.

Tolu J., Thiry Y., Bueno M., Jolivet C., Potin-Gautier M. & Le

Hécho I. 2014: Distribution and speciation of ambient sele-
niumin contrasted soils, from mineral to organic rich. Sci. Total
Environ. 479—480, 93—101.

Van Loef J.J. 2000: Composition and genesis of rattlestones from

Dutch soils as shown by Mössbauer spectroscopy, INAA and
XRD. Geol. En. Mijnb. N.J.G. 79, 1, 59—71.

Yang H., Lu R., Downs R.T. & Costin G. 2006: Goethite,

a-FeO(OH), from single-crystal data. Acta Crystallographica
E62, i250—i252.