GEOLOGICA CARPATHICA, 49, 4, BRATISLAVA, AUGUST 1998
PECULIAR TYPES OF THIN VEINS IN THE MESOZOIC
CARBONATES AND SILICITES OF THE WESTERN CARPATHIANS
Department of Geology and Paleontology, Faculty of Science, Comenius University, Mlynská dolina,
842 15 Bratislava, Slovak Republic
(Manuscript received March 9, 1998; accepted in revised form June 16, 1998)
Abstract: Many veinlets in carbonate rocks considered as open crack fillings, are the result of recrystallization (dashed
veinlets formed by the shear, whitened veinlets). Synsedimentary and early diagenetic veinlets may be folded in a soft
sediment deformation or deformed by brittle fragmentation. They may also fill desiccation cracks, bedding parallel
joints and synsedimentary cracks with internal sediment (microdykes). Synaeretic cracks in bedded silicites and nodular
cherts can be filled with calcite partially infiltrating the still reactive silica mass (pearl-string type veinlets, bordered
veinlets), filled by chalcedony, or can disappear being healed by neighbouring silica mass. Relative dating of veinlets
with regard to the formation of authigenic minerals, formation of chert nodules, conglomerate deposition, calcite
twinning, microstylolites etc. is possible. Authigenic quartz, feldspars, pyrite, illite, baryte, fluorite and galena found
in calcite veinlets are mentioned. From the commonly occurring dedolomitized saddle dolomite in calcite veinlets, the
burial depth of the Krína Nappe was estimated.
Key words: Western Carpathians, Mesozoic, silicites, limestones, dolomites diagenesis, synsedimentary cracks, veinlets.
Veinlets register a lot of the geological history of carbonate and
silicite complexes since their deposition through early diagene-
sis and deep burial up to their final uplift to subsurface depth.
They reflect strain field, tectonic events, render possible the es-
timation of the burial depth, record changes in the composition
of fluids. This contribution is focused upon the types of vein-
lets derived from thin-section study and the perspectives for
further investigations. The types of veinlets recognized in the
following paper are summarized in the Fig. 1.
Questions concerning veins are dispersed in many pa-
pers. A review of them can be found in Groshong (1988).
Types of veinlets
Recrystallization veinlets. According to the current
opinion thin veins in limestones originated by the filling of
opened cracks that is by filling of an empty space. In an older
contribution (Miík 1971) I demonstrated that a considerable
part of these veinlets of millimetres thickness was formed by
recrystallization. That is clear mainly in such cases when
fossils (bioclasts) cross the veinlet without being torn and
both their ends put off, e.g. the aptychus at the Pl. I: Fig. A.
The upper veinlet seems to be formed still in the unlithified
sediment and the fossil could have been torn off the matrix.
Relics of echinoderm plates are frequently preserved in the
recrystallized veinlets (Pl. I: Fig. B). They originated mostly
as so-called dashed veinlets (see in the further text). The pen-
etration of the echinoderm plate into the veinlet on Pl. I:
Fig. C is clearly visible, the recrystallization (removal of in-
clusions) was perfect and the dashed structure totally disap-
peared. Another veinlet (Pl. I: Fig. D) also seems to repre-
sent a normal filled crack but it branches by entering the
crinoidal plate and so betrays its origin by the coalescence
of thin veinlet array.
Several veinlets caused only lightening of the crossed part
of fossil (aptychus Pl. I: Fig. E, echinoderm plates and
ooids Pl. I: Fig. F), see further as whitened veinlets. The
fibrous calcite aggregate of the veinlet crossed by undis-
turbed juvenile bivalves (Pl. II: Fig. A) also belong to the re-
Dashed veinlets (definition by Miík 1971) originated by
recrystallization, by amalgamation of an array of subparallel
hair-thin veinlets formed by the shear. Their origin was later
explained by Ramsay (1980) by the crack-seal-mechanism (re-
peated cracking and sealing). Bons & Jessell (1997) suggested
an alternative explanation of fibrous veins, formed by diffu-
sional transport, by dissolution-precipitation creep, without
fracturing. Our cases indicate the origin of dashed veins from
an array of thin subparallel cracks which is not compatible
with the process supposed by Bons & Jessell (1997).
A considerable part of the thickness of dashed veins pro-
ceeds from the recrystallization of the micritic host rock. The
remnants of micrite dividing former subparallel veinlets are
concentrated in stripes or only as inclusion trails parallel to
the vein (Pl. II: Figs. BE; Pl. III: Fig. A). Some larger cal-
cite grains were totally cleaned of these remnants during the
recrystallization (aggrading neomorhism, Folk 1965), while
they are well preserved in the neighbouring grains(Pl. II: Fig.
C). The new-formed aggregates use to have a columnar or fi-
brous structure with fibres normal to the veinlet walls. The
origin of the asbestos-like calcite aggregate could probably
have been initiated by the process of forming the array of
very thin veinlets as can be seen in Pl. III: Figs. B, C. Some
of dashed, originally fibrous veinlets can acquire after re-
crystallization an aspect of elongated-blocky veins of Fisher
& Brantley (1992).
The mutually cut dashed veinlets register the change in the
direction of extension (Pl. II: Fig. F). The dashed veinlets are
sometimes folded (Pl. III: Fig. D), perhaps contraction af-
fected still semiconsolidated and later compacted sediment.
The dashed veinlets also occur in dolomites. In the two fol-
lowing cases the remnants of dashed structure were preserved
due to authigenic quartz replacing a part of the veinlet before
its final recrystallization (e.g. in a Carboniferous dolomite
Pl. II: Fig. E and the Triassic dolomite Pl. III: Fig. F).
These examples again show that the recrystallized veinlets are
much more wide spread than was estimated before, because
frequently no phantoms of their dashed nature were preserved.
Recrystallized dashed veinlets also occur in silicites, e.g.
quartz veinlet in Triassic radiolarites (Pl. IV: Figs. A, B), cal-
cite veinlet in Oxfordian radiolarites (Pl. IV: Figs. CE). An
albitic dashed veinlet was exceptionally found in the acid tuf-
fites. Similar veinlets were illustrated by Ramsay & Huber
from greywackes (1987, Fig. 25.16) and calcareous phyllites
(Fig. 25.17). Augustithis (1973, Fig. 12.12) illustrated dashed
veinlets from granites; he explained them surprisingly as col-
Bordered veinlets belong to a rare type. They represent a
combination of normal veinlet with recrystallization veinlet.
Their central part originated by filling of an empty space
(open crack) and lacks inclusions. The recrystallization part
was developed along both sides by replacement of the sedi-
ment and therefore is full of inclusions. Bordered veinlets
were found in limestones (Pl. IV: Fig. F), radiolarites (Pl. IV:
Fig. G), and chert nodules (Pl. V: Fig. A).
Whitened veinlets. In these cases the recrystallization is
manifested by whitening (removal of inclusions during the
recrystallization) of the matrix, ooids and bioclasts crossed
by the veinlet in limestone (Pl. I: Fig. F). In another case the
recrystallization veinlet cleared an aptychus by removing of
its pigment without tearing it (Pl. I: Fig. E).
Limpid phantom veinlets occur very frequently in the do-
lomites (Pl. V: Fig. B). They possess sharp boundaries but
pass independently of the new-formed mosaic of larger
grains (aggrading neomorphism). They are phantoms of nor-
mal veinlets filled with clear dolomite cement which lost
their individuality during the recrystallization of the dolo-
mite rock. The same explanation was suggested by Bose
(1979, p. 690, Fig. 8F).
Granulation veinlets in dolomites, in contrast to the pre-
ceding category, originated by degrading neomorphism (Folk
1965). They represent thin zones of the tectonic trituration of
a coarser-grained dolomite (Pl. V: Fig. C). The pseudodolo-
micritic matrix of dolomite tectonic breccias originated by
increasing the amount of their products.
Syngenetic (or very early diagenetic) veinlets deserve spe-
cial attention. Five types of them will be described.
Veinlets folded by compaction are frequent in marls and
marly limestones (Pl. III: Fig. D), but also occur in rapidly
accumulated silicites. Two examples will be mentioned. Tri-
Plate I: Thin-section microphotographs in plane-polarized light.
Fig. A. Aptychus crosses the upper recrystallization veinlet without
being disturbed; it was partly dislocated in the lower one. Upper Ti-
thonian limestone, Manín Unit, klippe Butkov, 6. gallery. Magn.
. Fig. B. Recrystallization veinlet formed by the coalescence of
parallel hairline cracks shown by the remnants of dashed structure
in the place where it is crossed by the crinoidal plate. Liassic lime-
stone, Krína Nappe, Donovaly, Nízke Tatry Mts. Magn. 55
Fig. C. Partial penetration of an echinoderm plate in a calcite re-
crystallization veinlet shows that it did not originate from an open
crack. Upper Tithonian limestone, Manín Unit, Butkov, borehole
LC-5, 25 m. Magn. 55
. Fig. D. Recrystallization veinlet penetrat-
ing the crinoidal plate. The ghosts of its pore structure and preced-
ing thin veinlets array are visible inside the veinlet. Liassic lime-
stone, Krína Nappe, Donovaly, Nízke Tatry Mts. Magn. 43
Fig. E. Recrystallization veinlet crossed by aptychus. At the cross-
ing the aptychus lost pigment during the recrystallization (whitened
veinlet). Tithonian limestone, Krína Nappe, Padlá Voda near Smo-
lenice, Malé Karpaty Mts. Magn. 43
. Fig. F. Whitened veinlets
with phantoms of crossed ooids and bioclasts (their pigment was
partly removed during the recrystallization). Rhaetian limestone,
Krína Nappe, loc. 114 near Rajec, Malá Fatra Mts. Magn. 20
Fig. 1. Described types of veinlets.
PLATE I 273
274 PLATE II
PECULIAR TYPES OF THIN VEINS IN THE MESOZOIC CARBONATES AND SILICITES 275
assic radiolarites of the Meliata Unit are sometimes associ-
ated with hematite and baryte deposits proceeding from hy-
drotherms penetrating through the ocean bottom. Deforma-
tions of the net of chalcedony veinlets caused by the
movement of non-consolidated mass have been found at the
locality Bradlo (Pl. V: Fig. D). Another case is represented
by the Oxfordian radiolarites (Pl. V: Fig. E), from the locali-
ty Trstená bowling alley (Miík et al. 1991a). The participa-
tion of hydrotherms in the silica accumulation was docu-
mented there by rare baryte crystals, roof-like lifting of
radiolarite laminae by ascending fluids (Pl. V: Fig. F) and
large spheroids (their sole locality in Slovakia). From the
folded vertical veinlet (Pl. V: Fig. E) compaction at least 20
% can be deduced. In other localites radiolarites were depos-
ited slowly (about 5 mm/1000 y) and do not contain such
Extremely folded calcite veinlets were found in a Mn-crust
from the Oxfordian limestone (Pl. VI: Figs. A, B). It is an ex-
ceptional case for Mn-crust. The early filled dehydratation
cracks were deformed by the movement of semiconsolidated
colloidal mass rapidly accumulated by supposed hydrotherms.
Fragmented veinlets originated by breaking of a rigid
veinlet within the semiconsolidated mass. The doubling of
part of a veinlet may be documented from the above men-
tioned radiolarite locality Bradlo (Pl. VI: Fig. C). The second
locality for radiolarites at Trstená bowling-alley also con-
tains fragmented syngenetic veinlets (Pl. VI: Fig. E). Such
broken veinlets also illustrated Soták & Ovoldová (1993,
pl. XXXII: Figs. 12) from the radiolarites of the Car-
pathian Flysch Belt and Hattori et al. (1996, Fig. 6A, p. 169)
from the Japanese Miocene silicites. Fragmented syngenet-
ic veinlets rarely occurred in spiculite limestone (Pl. VI:
Fig. D) and fresh-water Upper Cretaceous limestone (Pl. VI:
Fig. E with imbricated fragments).
Desiccation veinlets were formed during temporary emer-
sion, e.g. circular veinlets from dehydratation cracks in
fresh-water limestone (Pl. VI: Fig. G), or from cracked litho-
clasts in the Keuper Dolomite (Pl. VII: Fig. C). Veins paral-
lel to the bedding filled with prismatic or fibrous calcite ag-
gregate were named sheet cracks by Fischer (1964, p.114).
In the Western Carpathians they occur in dolomites (Pl. VII:
Fig. D); the cases of their partial erosion support their origin
near the surface.
Dewatering veinlets and voids may be formed within the
covered sediment, e.g. circular cracks in a coal fragment (Pl.
VII: Fig. A), in limestone (Pl. VII: Fig. B perhaps
formed due to fluid overpressure). Subaqueous shrinkage
cracks were described Donovan & Foster (1972).
Veinlets from the dehydratation of opal-chalcedony
mass. Shrinkage cracks sealed usually by chalcedony occur
in radiolarites (Pl. V: Fig. D) or chert nodules (Pl. VII: Fig.
E some parts of the veinlets are filled with calcite, others
with chalcedony). More examples will be demostrated fur-
ther by discussing syngenetic veinlets in chert nodules.
Syngenetic neptunic microdykes also represent the prod-
ucts of syngenetic cracking of sediment. If such cracks were
partly filled by sediment and the remaining space by calcite,
a polarity structure originated (Pl. VII: Fig. F). Neptunian
microdykes filled with sediment of a different age (Pl. VIII:
Fig. A) are not the subject of this contribution. A special case
was registered in Pl. VII: Fig. G where the infilling of a mi-
crodyke was repeatedly cracked forming an array of very
thin veinlets parallel to the microdyke walls.
Timing of veinlet formation
Timing of veinlets in the conglomerates. It is possible to
discern three groups of veinlets: (1) preconglomerate veinlets
occur only in the pebbles, they reflect older tectonic process-
es (Pl. VIII: Fig. D), (2) synchronous with the deposition
these veinlets proceed from the cracking of pebbles under the
load (Miík et al. 1991a,b,c), the matrix was entrained in the
cracks and the rest eventually filled by calcite cement (Pl.
VIII: Figs. A, C), (3) post-depositional veinlets formed after
the solidification of the conglomerate; they cross not only
pebbles but also the matrix in parallel systems.
Timing of veinlets formation in chert nodules. Three
groups can be defined:
(1) Pre-chert calcite veinlets limit in straight lines the
chert nodules in thin sections; they represented an obstacle to
the growth of the nodule and stopped the migrating silica so-
lutions (Pl. VIII: Figs. E, F). They are very frequent. The op-
posite case of pre-chert shear joints serving for the small
chert accumulations was observed only once (Pl. IX: Fig. A).
It might be a case of diastasis cracks (Cowan & James 1992)
originated by differential mechanical behaviour of interlay-
ered stiff mud under stress.
(2) Syngenetic veinlets, already mentioned (Pl. VII: Fig.
E), were formed in the stage when silica accumulation con-
tained a considerable amount of water and was still reactive.
Solutions of calcium bicarbonate penetrated in the submicro-
scopic synaeretic cracks, calcite rhombs grew from them as
if hanging on a string (Pl. IX: Figs. C, E) pearl-string
type of veinlets (Miík 1971, 1993). Radiolarians were filled
by calcite monocrystal but only in their immediate neigh-
bourhood (Pl. IX: Fig. D).
Plate II: Fig. A. Shells of juvenile bivalves cross the recrystalliza-
tion veinlet, formed by fibrous calcite, without being torn in two
pieces. Middle Triassic limestone, Choè Nappe, quarry near Èierna,
Stráovské vrchy Mts. Magn. 43
. Fig. B. Dashed veinlets with par-
allel inclusions of the marly micritic limestone, originated by re-
crystallization from parallel hairline fractures (crack-seal mecha-
nism). Neocomian limestone, Manín Unit, Butkov. Magn. 43
Fig. C. Vestige of dashed structure; the impurities were partly re-
moved by aggrading crystallization. The same locality. Magn. 43
Fig. D. Rare remnants of the dashed structure make it possible to
identify a recrystallization veinlet. Thin section from a pebble of
Barremian Lower Aptian limestone in the Cenomanian conglom-
erate. Shear cracks with the following recrystallization veinlet were
formed in the time span Upper Aptian Albian. Manín Unit,
Praznov. Magn. 43
. Fig. E. Remnants of dashed structure near the
lower margin of the veinlet and neighbouring parallel hairline vein-
lets betray the recrystallization. Neocomian marly limestone, Kysu-
ca Unit of the Klippen Belt, Horné Sànie. Magn. 43
. Fig. F. Array
of subparallel veinlets penetrated by a dashed veinlet. Neocomian
limestone, Manín Unit, Butkov, gallery 6, 32 m. Magn. 23
276 PLATE III
PLATE IV 277
278 PLATE V
PLATE VI 279
280 PLATE VII
PECULIAR TYPES OF THIN VEINS IN THE MESOZOIC CARBONATES AND SILICITES 281
Plate III: Fig. A. Another thin vein which did not originate by the filling of an open crack. The true extension was only about half the thick-
ness of this dashed veinlet. Pebble of the Upper Tithonian limestone from the Eocene Strihovce Conglomerate, Magura Unit of the Flysch
Belt. Starina. Magn. 30
. Fig. B. New-formed calcite fibres approximately perpendicular to the array of hairline veinlets. Pebble of the Se-
nonian limestone from the Lower Miocene Jablonica Conglomerate. Prievaly. Magn. 30
. Fig. C. Calcite fibres (pseudosparite) grown per-
pendicularly to the array of hairline cracks. Norian Hallstatt Limestone, Silica Nappe, Silická Brezová. Magn. 55
. Fig. D. Folded dashed
veinlet indicates that the crack-and-seal mechanism took place still in a non-consolidated sediment. Lower Tithonian marly limestone, up-
permost nappe, quarry in ipkovský Haj near Krajné, Èachtické Karpaty Mts. Magn. 30
. Fig. E. Thin calcite vein partially replaced by au-
thigenic quartz (white). Remnants of the dashed structure are preserved only in quartz due to the early replacement. Upper Visean Lower
Namurian dolomite, Gemeric Superunit, Ochtiná. Magn. 30
. Fig. F. Part of a carbonate veinlet in dolomite was early replaced by the authi-
genic quartz; its dashed structure was preserved only there. Pebble of Triassic dolomite in the Albian Ludrová Conglomerate, Tatric Super-
unit, Malá Magura Succession. Èavoj-20. Stráovské vrchy Mts. Magn. 95
Plate IV: Fig. A. Quartz dashed veinlet in the radiolarite. Ladinian-Carnian of the Meliata Unit, Bradlo, South-Slovak Karst. Magn. 55
B. The same in cross-polarized light; perpendicularly recrystallized quartz grains are clearly visible. Fig. C. Dashed calcite veinlet in the ra-
diolarite, formed by coalescence of hairline cracks. Oxfordian radiolarites of the Pieniny Succession, Klippen Belt, Dúbrava near Stará Turá.
. Fig. D. Dashed calcite veinlet in the radiolarite. Oxfordian of the Pieniny Succession, Klippen Belt, Trstená bowling alley. Magn.
. Fig. E. Calcite dashed veinlet in a radiolarite. Recrystallization of hairline veinlets to perpendicular calcite fibres and prismatic grains
eliminated the dashed structure except for some remnants of host rock in the calcite vein. The same locality. Magn. 30
. Fig. F. Bordered
veinlet in dolomitic limestone. Its pigmented margins were formed by syntaxial growth of calcite grains from the veinlet at the expense of the
host rocks, partially dolomitized limestone. Anisian Gutenstein Limestone, Tatric Succession, Ve¾ký Kriváò, Malá Fatra Mts. Magn. 25
Fig. G. Bordered calcite veinlet in radiolarite. Its clear middle part was formed by the filling of an open fracture with chalcedony. Grey pig-
mented borders were formed by calcite replacing the host Oxfordian radiolarite. Pieniny Klippen Belt. Trstená, bowling alley. Magn. 48
Plate V: Fig. A. Bordered veinlets in the chert nodule are syngenetic with the chert forming process. Their middle limpid parts had been
open cracks filled by calcite. Its grains grew syntaxially through the walls into the surrounding silica mass with high content of water. The
replaced margins are grey, filled by inclusions. Chert nodule in the Upper Tithonian limestones of the Kysuca Succession, Peniny Klippen
Belt, quarry near Brodno. Magn. 55
. Fig. B. Lightened veinlets in dolomite do not disturb the grain mosaic. They are ghosts of normal vein-
lets (open cracks filled by limpid dolomite) in the completely recrystallized dolomitic rocks with grains full or inclusions. Ladinian dolomite
of the Krína Nappe, Demänová, Pod Lúèkami, Nízke Tatry Mts. Magn. 136
. Fig. C. Network of granulation veinlets in dolomite repre-
senting fine cracks filled by cataclastic pseudodolomicrite. Triassic dolomite breccia. Vojtová Valley near Rajec, Stráovské vrchy Mts.
. Fig. D. Synsedimentary folded network of chalcedony veinlets in radiolarite. After the filling of thin synaeretic cracks, sliding
of non-consolidated silica mass took place. The hydrothermal activity caused the rapid accumulation of silica. Ladinian-Carnian radiolarite
of the Meliata Unit, Tri Peniaky, Bradlo, South Slovak Karst. Magn. 14
. Fig. E. Compactional deformation of the chalcedony veinlet in
distal turbidite intercalation within the Oxfordian radiolarites. Pieniny Succession, Klippen Belt, Trstená bowling alley. Magn. 30
. Fig. F.
Vertical veinlet filled with chalcedony penetrating laminated radiolarite. The filling proceeds from a hydrothermal source at the bottom; the
ascending fluids heaved the uppermost part of the sediment which was not yet consolidated. The same locality. Polished section, slightly
Plate VI: Fig. A. Ptygmatic folding of calcite veinlets in a hardground Mn-crust occurred during the Albian. Early filled dehydratation
cracks were deformed by the movement of semiplastic colloidal manganese mass. Czorsztyn Succession, Vratec-castle klippe. Magn. 48
Fig. B. The same. Magn. 16
. Fig. C. Fragmented chalcedony veinlet formed by the breaking of its consolidated filling within still semiplas-
tic silica mass; fragments are partially overthrust. Ladinian-Carnian radiolarites of the Meliata Unit, Bradlo Tri Peniaky. Magn. 43
D. Early vertical calcite veinlet (perpendicular to the lamination) fragmented during compaction. Liassic limestone pebble from the Eggen-
burgian conglomerate, quarry near Podbranè (material of I. Baráth). Magn. 14
. Fig. E. Fragmented veinlet with early consolidated chalce-
dony filling, broken by extension of the still semiplastic silica sediment. Oxfordian radiolarites, Trstená, bowling alley, Pieniny Succession.
. Fig. F. Syngenetic fragmented calcite veinlet with partial imbrication of its fragments, diagonally crossed by a set of thin young-
er veinlets. Fresh-water Coniacian limestone, pebble in the Santonian-Campanian conglomerate. Dobinská ¼adová jaskyòa. Magn. 30
G. Circular veinlets originated by the calcite filling of desiccation cracks in fresh-water Lower Coniacian limestone. Betlanovce, Stratenská
hornatina Mts. Magn. 7
Plate VII: Fig. A. Dewatering circular calcite veinlets (filled desiccation cracks) in a coal fragment. Senonian marlstone with silt lami-
nae. Borehole Gajary G-125, 4842 m, basement of the Vienna Basin. Magn. 13
. Fig. B. Dewatering veinlets synsedimentary cracks
filled with calcite cement and partly by younger micrite. Upper Berriasian limestone of the Horná Lysá Succession, Pieniny Klippen Belt,
Vratec. Magn. 22
. Fig. C. Desiccation veinlets (thin cracks formed during temporary emersion) with dolomitic infilling in a dolomite
intraclast. Norian Keuper dolomite of the Krína Nappe, quarry between diar and Tatranská Kotlina. Magn. 11
. Fig. D. Desiccation
veins of the sheet-crack type. Stratabound joints filled by asbestos-like calcite fibres, locally affected by the erosion. Ladinian Wetter-
stein Limestone, quarry near Krásna Ves, Stráovské vrchy Mts. Polished section, natural size. Fig. E. Network of syngenetic dehydrata-
tion veinlets in a chert nodule. Synaeretic cracks were partially filled with calcite and partially refilled with silica mass. Chert from the
Upper Tithonian limestone of the Kysuca Succession, Pieniny Klippen Belt, quarry near Brodno. Magn. 20
. Fig. F. Neptunic veinlets
(microdykes) syngenetic cracks filled partially by internal micritic sediment; the remaining empty space was sealed by calcite cement.
Polarity structure shows inclination with regard to the laminated infilling of a void, larger than the figure. Callovian-Oxfordian lime-
stone, klippe Kostelec. Magn. 6
. Fig. G. Neptunic microdyke formed as an open vertical fracture in Berriasian limestones with tintin-
nids which was filled by red Albian marl with Hedbergella and Ticinella. The microdyke filling was later disturbed by a set of hairline
veinlets subparallel to the fracture. Czorsztyn Succession, Klippen Belt, quarry near Kamenica. Magn. 30
282 PLATE VIII
PECULIAR TYPES OF THIN VEINS IN THE MESOZOIC CARBONATES AND SILICITES 283
(3) Post-chert veinlets represent younger tectonic phe-
nomena. They originated by cracking of already non-reactive
solidified chert nodules. These open joints were filled with
clear calcite aggregates. Due to the higher plasticity of the
limestone compared to the silicite, the veinlets in chert nod-
ules are always thicker and more frequent (Pl. IX: Fig. B).
Timing of veinlets with regard to authigenic minerals
and other diagenetic phenomena. If the authigenic quartz
or feldspar is younger than the veinlet, it extends from the
rock into the veinlet (Pl. X: Figs. C, D). The veinlet is cut by
the younger stylolite (Pl. IX: Fig. F). A younger vein filled
an opened stylolite after the change of compression into ex-
tension (Pl. X: Fig. A); the opposite explanation is impossi-
ble, because the coarse-grained filling of the veinlet would
not render possible the formation of a stylolite. Similar solu-
tions exist in relation to veinlets and microslickensides. If the
grains of a limestone were affected by pressure twinning, the
veinlets older than twinning will also be affected; the calcite
filling of the younger veinlets would not be disturbed.
Influence of veinlets on the colour of limestones. Calcite
veinlets formed an obstacle to the late diagenetic migration
of pigments (Pl. X: Fig. B). On the other hand, veinlets
younger than the pigment of the red limestones cause the
well-known decoloration (or green coloration) in their imme-
diate surrounding, due to the reducing nature of fluids.
Some other minerals from veinlets
Veinlet minerals other than calcite were not the subject of
this contribution, therefore only some examples from the
Western Carpathians will be presented. Authigenic quartz lim-
ited to the calcite veinlets is not rare; macroscopic crystals oc-
cur in the Liassic Borinka limestones (Turan & Vavro 1970),
Liassic limestone of the Oreany Succession, quarry NW from
Dolany, Malé Karpaty Mts. and in Paleogene sandstones
(Marmarosch diamonds Hurai et al. 1995). Authigenic
feldspar (microscopic size) is exceptional, e.g. Neocomian
limestones, locality Butkov. Pyrite is frequent, baryte rare (e.g.
in Keuper Dolomite, Zázrivá), fluorite exceptional (e.g. Car-
nian Opponitz Limestone, basement of the Vienna Basin,
borehole Závod-93, in the depth 5306 m), galena occurred only
once in a calcite veinlet from Liassic limestones of the Malá
Fatra Mts. (Miík 1964, p. 85). Albite veinlets in radiolarites
are probably connected with postvolcanic activity (Triassic ra-
diolarites of the Meliata Unit, Jaklovce Pl. X: Fig. E, and in
a pebble of Jurassic radiolarites from Strihovce conglomerates,
Flysch Belt Miík et al. 1991b, p. 23, Pl. III: Fig. 1).
Illite veinlets do not attract due attention in spite of their
frequency. In the Western Carpathians they occur mainly in
Liassic and Tithonian-Neocomian limestones. They consist
of large light-brown aggregates with uniform extinction, ori-
ented parallel to the walls of veinlets; their birefringence is
comparable with that of the illite. The material from a vein-
let about 1 mm thick from Neocomian limestones was iden-
tified (V. ucha personal communication) by X-ray analysis
as a mixture of illite and chlorite. It is probable that at least
some of the illite veinlets represent microslickensides. The
material for the new-formed illite probably originates from
the tiny submicroscopic clastic illite in limestone, mobilized
during pressure solution.
Veinlets with dedolomitized saddle dolomite. They of-
fer possibility of approximate estimation of temperature.
The temperatures from isotopic study of host limestones are
much lower than those from the calcite of veinlets, for exam-
ple the red nodular Hallstatt Limestone, locality Silická Bre-
zová (Kantor & Miík 1992) had
0 = 0.87 , the calcite
from a veinlet of the same specimen
0 = 7.38 corre-
sponding to the temperature of about 60
The Jurassic and Cretaceous limestones of the Krína
Nappe frequently contain veins (up to 2 cm in thickness) filled
by a mixture of white calcite and brown carbonate grains. In
all the analyzed cases the brown grains belonged to the dedo-
lomitized baroque dolomite (Pl. X: Figs. F, G). The saddle or
baroque dolomite originated under temperatures mostly be-
tween 90 and 160
C (Spötl & Pitman 1992) which reflects
the minimum burial depth. Supposing an average value of 33
C the burial depth could be estimated as 2.34.6 km.
The baroque dolomite with characteristic curved crystal
planes and sweeping exctinction was in all cases dedolo-
mitized, and replaced by secondary calcite. The brown co-
lour proceeds from Fe
isomorphe admixture in Mg
was liberated by the calcification and oxidized. The dedolo-
mitization was caused by groundwaters charged with sul-
phate ions during the erosional uprise to subsurface level.
The modern methods for studying thin veins such as stable
isotope analyses, cathodoluminiscence, microprobe analyses
of calcite, study of inclusions and structural measurements
must be preceded by a serious thin-section study. Various
Plate VIII: Fig. A. Neptunic microdykes cracks in the Oxford-
ian limestone filled with Albian limestone sediment with Hedber-
gella and Ticinella. Czorsztyn Succession, Vratec-castle klippe.
. Fig. B. Veins in synsedimentary cracked pebble filled
with the matrix of the conglomerate. Limestone pebble from the
Paleocene Proè Conglomerate, Pieniny Klippen Belt, Beòatina.
Natural size. Fig. C. Synsedimentary cracks in a limestone pebble
were filled with the not yet consolidated matrix. These clastic
veinlets, synchronous with the deposition of conglomerate, are pe-
culiar for the abundant quartz grains totally absent in the sur-
rounding limestone. Their distal wedging-out parts were filled by
calcite cement. Pebble of the Paleocene biohermal limestone in the
Eocene Strihovce Conglomerate, Flysch Belt. Matiaka. Magn.
. Fig. D. Pre-conglomerate veinlet in the pebble of Middle Tri-
assic limestone from the Coniacian Upohlav Conglomerate of
the Kysuca Succession, Pieniny Klippen Belt. The calcite veinlet
was formed in the time span Upper Triassic Middle Cretaceous
probably during the Cretaceous tectonics in the accretionary
wedge. Zádubnie. Magn. 20
. Fig. E. Pre-chert calcite veinlets
originated in the micritic radiolarian limestone before the forming
of chert nodules. They acted as obstacles for the migrating silica
and limit the chert nodule in straight lines. Neocomian cherty
limestone, Manín Unit, quarry Butkov. Magn. 23
. Fig. F. Another
pre-chert veinlet. Berriasian-Valanginian Horná Lysá Limestone,
Kysuca Succession, Vratec. Magn. 13
284 PLATE IX
PLATE X 285
Plate X: Fig. A. The calcite veinlet is younger than the stylolite. During the compressional phase the stylolite was formed. In the course
of the following extension the stylolite was opened and the crack sealed by coarse-grained calcite aggregate. Tithonian limestone of the
Kysuca Succession, quarry near Brodno. Polished section, natural size. Fig. B. The vertical calcite veinlet was an obstacle for the late di-
agenetic migration of pigment-bearing solutions. Stromatolitic limestone (loferite) with desiccation pores partly filled with internal sedi-
ment. The right side and the left side of the same layer are differently coloured. Norian limestone from the basement of the Vienna Basin.
Borehole Studienky-95, 4195 m. Magn. 30
. Fig. C. The authigenic idiomorph quartz is younger than the calcite veinlet. Ladinian Rei-
fling Limestone of the Choè Nappe. Hradkovo, Choè Mts. Magn. 136
. Fig. D. The authigenic feldspar is younger than the calcite vein-
let. Rhaetian limestone pebble from the Cenomanian-Turonian conglomerate of the Klape Unit. Oravský Podzámok. Magn. 136
. Fig. E.
Albite veinlet in the Carnian radiolarite of the Meliata Unit, probably formed by post-volcanic activity of near by diabase (basalt) bodies,
approximately of the same age. Jaklovce. Magn. 30
, crossed polars. Fig. F. Dedolomitized (calcified) grains of saddle dolomite with
curved crystal planes, pigmented by iron hydroxides. They partially replaced the older calcite filling of the veinlet. Liassic limestone of
the Krína Nappe, Kraviarske, Malá Fatra Mts. Magn. 27
. Fig. G. Dedolomitized saddle dolomite grains (dark) replacing the older cal-
cite filling of the vein. Neocomian limestone, Krína Nappe, Motyèky, Nízke Tatry Mts. Magn. 26
Plate IX: Fig. A. Pre-chert veinlets filled with silica. Tensional cracks inclined to the stratification were probably formed in the not yet
consolidated calcareous sediment and immediately used by the migrating silica solutions. Upper Tithonian limestone of the Choè Nappe,
ipkovský háj near Krajné. Polished slab, natural size. The photo is rotated 90
. Fig. B. Set of post-chert calcite veinlets is limited to the
chert nodule. The rigid chert was disturbed by extensional fractures in difference to the more plastic host limestone. Neocomian cherty
limestone, Hradská Valley near Podhradie, Ve¾ká Fatra Mts. Polished slab, natural size. Fig. C. Veinlet of the string-pearl type syngenetic
with the chert. The solutions of calcium bicarbonate penetrated through the synaeretic cracks in the time when the silica mass rich in wa-
ter was still reactive. Calcite grains usually of rhombic shape grew from the cracks replacing the silica mass. Upper Jurassic cherty lime-
stone, Pieniny Succession, Klippen Belt, Lubina. Magn. 55
. Fig. D. Another veinlets syngenetic with the chert nodule. Molds of radi-
olarians in their immediate neighbourhood were also filled by calcite; other radiolarians in the chert were dissolved mostly without any
trace. Tithonian cherty limestone of Kysuca Succession, Klippen Belt, quarry near Brodno. Magn. 43
. Fig. E. Pearl-string type veinlets
syngenetic with the chert nodule in dolomite. They consist of a row of calcite rhombs replacing silica (their calcitic nature was verified
by the staining with alizarine). Red chert nodule in Norian Keuper dolomite. Magn. 95
. Fig. F. Microstylolite is younger than the veinlet
in Middle Jurassic radiolarites of the Meliata Unit. Meliata, near the mill. Magn. 45
types of veinlet are described in this contribution (Pls. IX
and Fig. 1).
It was shown that a lot of veinlets regarded as normal
(open cracks originated by extension) are really the recrystal-
lized veinlets formed by shear. Recrystallized veinlets can
be identified by fossils traversing them without being torn,
by remnants of an array of coalescing hairline shear veinlets
(dashed or crack-and-seal veinlets), by whitening removal
of inclusions during the recrystallization.
Synsedimentary veinlets in carbonate and silicic rocks
may be deformed in the semiplastic state of sediment (duc-
tile deformation) or by brittle fragmentation. Syngenetic
and very early diagenetic veinlets fill desiccation cracks,
beddingparallel joints (sheet cracks), neptunic microdykes
(partly filled with internal sediment), subaqueous dewatering
cracks, synaeretic cracks in silicites (bordered veinlets with
replacement margins and pearl-string type).
We are handicapped by the impossibility of calcite radio-
metric dating (except of Quaternary calcites), therefore nu-
merous possibilities for relative dating of veinlets must be
used: with regard to authigenic minerals, formation of nodu-
lar cherts, deposition of conglomerates, calcite twinning, for-
mation of microstylolites etc.
The large extension of dedolomitized saddle dolomite in
calcite veinlets within the Mesozoic limestones of Krína
Nappe shows the burial depth about 2.34.6 km. The abun-
dance of thin illite veinlets in the studied limestones is su-
prising. The formation of albite veinlets in Triassic radiolar-
ites are considered to be a post-volcanic feature.
A team study of thin veins can substantially contribute to
the deciphering of the diagenesis, subsidence, fluid migra-
tion and tectonic history of carbonate and silicite complexes.
Acknowledgements: The author is indepted to Prof. Franz
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