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, FEBRUARY 2012, 63, 1, 71—82 doi: 10.2478/v10096-012-0005-7
Sapphires related to alkali basalts from the Cerová
Highlands, Western Carpathians (southern Slovakia):
composition and origin
PAVEL UHER
1
, GASTON GIULIANI
2
, SÁNDOR SZAKÁLL
3
, ANTHONY FALLICK
4
, VLADIMÍR
STRUNGA
5
, TOMÁŠ VACULOVIČ
6
, DANIEL OZDÍN
1
and MARGARÉTA GREGÁŇOVÁ
1
1
Department of Mineralogy and Petrology, Faculty of Natural Sciences, Comenius University, Mlynská dolina G, 842 15 Bratislava,
Slovak Republic; puher@fns.uniba.sk
2
GET/IRD and CRPG/CNRS, 15 rue Notre Dame des Pauvres, BP 20, 54501 Vandceuvre-l
e
s-Nancy Cedex, France
3
Department of Mineralogy and Petrology, University of Miskolc, H-3515 Miskolc-Egyetemváros, Hungary
4
Isotope Geosciences Unit, S.U.E.R.C., Rankine Avenue, East Kilbride, Glasgow G75 0QF, United Kingdom
5
Department of Geological Sciences, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
6
Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
(Manuscript received December 13, 2010; accepted in revised form September 30, 2011)
Abstract: Blue, grey-pink and pink sapphires from the Cerová Highlands, Western Carpathians (southern Slovakia)
have been studied using CL, LA-ICP-MS, EMPA, and oxygen isotope methods. The sapphire occurs as (1) clastic heavy
mineral in the secondary sandy filling of a Pliocene alkali basaltic maar at Hajnáčka, and (2) crystals in a pyroxene-
bearing syenite/anorthoclasite xenolith of Pleistocene alkali basalt near Gortva. Critical evaluation of compositional
diagrams (Fe, Ti, Cr, Ga, Mg contents, Fe/Ti, Cr/Ga, Ga/Mg ratios) suggests a magmatic origin for clastic blue sap-
phires with lower Cr and Mg, but higher Fe and Ti concentrations in comparison to the grey-pink and pink varietes, as
well as similar compositional trends with blue sapphire from the Gortva magmatic xenolith. Moreover, blue sapphires
show similar
18
O values: 5.1 ‰ in the Gortva xenolith, 3.8 and 5.85 ‰ in the Hajnáčka placer, closely comparable to
mantle to lower crustal magmatic rocks. On the contrary, pink and grey-pink sapphires show higher Cr and Mg, but
lower Fe and Ti contents and their composition points to a metamorphic (metasomatic) origin.
Key words: Western Carpathians, Slovakia, Hajnáčka, Gortva, CL, LA-ICP-MS, EMPA, oxygen isotopes, placer,
alkali basalts, anorthoclasite xenolith, corundum, sapphire.
Introduction
Sapphire, usually a blue transparent variety of corundum is
one of the most important coloured gemstones, together with
diamond, ruby and emerald. It is found in three main geologi-
cal environments (e.g. Simonet et al. 2004; Giuliani et al.
2007; Graham et al. 2008; Sutherland et al. 2009): (1) mag-
matic, mainly as xenocrysts and in xenoliths of alkali basalts,
syenites, monzonites, and lamprophyres; (2) metamorphic,
mainly in marbles, skarns, granulites, cordieritites, gneisses to
migmatite rocks, mafic-ultramafic metamorphites and as xe-
nocrysts in basalts; and (3) secondary alluvial sedimentary de-
posits. In Europe, there are occurrences of sapphires in the
monchiquite dike from Loch Roag, Scotland (Jackson 1984),
syenite and anorthoclasite xenoliths connected with basaltic
volcanism (Scotland, northern Britain, Ireland – Upton et al.
1983, 2009), anorthoclasite xenoliths in trachytes at Menet,
French Massif Central (Brousse & Varet 1966), syenitic peg-
matites in the Southern Urals and Khibiny, Russia (Kievlenko
2003), pegmatitic albitite dikes in Urdach and Espech
è
re,
western Pyrenees, France (Monchoux et al. 2006), or in granit-
ic pegmatite xenolith from Karpacz, Karkonosze Mts, Poland
(Kozłowski & Sachabiński 2007). Alluvial sapphire occur-
rences related to alkali basalts were described in several Euro-
pean regions, for example in the Massif Central, France
(Giuliani et al. 2009, 2010) and Jizerská Louka, Czech Repub-
lic (Malíková 1999).
Sapphire from Hajnáčka in the alkali basalt area of the
Cerová Highlands, southern Slovakia has been known for
over one hundred years (Szádeczky 1899). However, addi-
tional sapphire specimens from Hajnáčka and near Gortva
occurrences were obtained and briefly described only recently
(Uher et al. 1999, 2006). The aim of our study is a detailed
description of this sapphire and associated minerals based on
current new analytical data (cathodoluminescence image,
electron-microprobe and LA-ICP-MS analyses, oxygen iso-
topes), and discussion on their likely origin.
Corundum within the Cenozoic volcanic fields of
the Western Carpathians
Blue corundum (sapphire) occurs as an accessory mineral
from several Neogene volcanic areas in the Western Car-
pathians, namely: in andesites and its pyroclastic rocks near
Sklené Teplice and Dolné Hámre, Štiavnica Mountains
(Hvož ara & Činčár 1972), in cordierite hornfels with silli-
manite and spinel in andesites near Dobrá Niva, Štiavnica
Mountains (Fiala 1954), in hornfels with sillimanite, an-
dalusite and cordierite from the KR-3 borehole near Kremnica,
è
è
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Kremnica Moutains (Böhmer & Šímová 1976), in sekani-
naite (Fe > Mg cordierite) xenoliths of andesites from Vechec,
Slanské Mountains (Ďu a et al. 1981), as well as in the
Börzsöny and Visegrád Mountains (Szakáll et al. 2002). Co-
rundum also occurs in Al-Si metasomatites connected with
Neogene andesitic volcanism in Kapka, Vihorlat Mountains
(Derco et al. 1977) and Víg ašská Huta, Javorie Mountains
(Marková & Štohl 1978). Moreover, alluvial corundum oc-
curs in the placers near the Neogene andesites of the Slan-
ské, Börzsöny and Visegrád Mountains (Ďu a et al. 1981;
Szakáll et al. 2002). All these corundum and/or sapphire oc-
currences occur in Miocene to Pliocene (15 to 10 Ma), sub-
duction-related andesitic activity in the West Carpathian area
and they have no direct genetic relationships with the sap-
phires related to the alkali basalts in Hajnáčka and Gortva
described in the present study.
Geological setting of Hajnáčka and Gortva
sapphires
The Hajnáčka and Gortva sapphires are connected with
Pliocene to Pleistocene within-plate volcanic activity in the
Cerová Highlands area, southern Slovakia (Fig. 1). The stud-
ied area belongs to the Cerová Basalt Formation, formed by
products of intraplate alkali basalt volcanism of Pliocene to
Pleistocene age (ca. 5 to 1 Ma; Vass et al. 2000). Besides
lava flows, cinder cones, diatremes, necks and dikes, several
phreatomagmatic eruptions (maars) are present (Konečný &
Lexa in Vass et al. 1992a,b; Vass et al. 2000).
The Hajnáčka sapphire occurs as isolated crystals or their
fragments in secondary psammitic sediments deposited in a
maar structure situated at Kostná valley or Kostný Jarok, ca.
600 m north of the Matrač Hill (410 m a.s.l.), 1 km SE of
Hajnáčka village, and ca. 12 km SE of Fi akovo town (Fig. 1).
The partly eroded maar is an elliptical structure, ca. 500 to
370 m in diameter with primary and secondary sedimentary
filling, which intruded older Eggenburgian sandstones of the
Fi akovo Formation. The Kostná valley or Kostný Jarok
(Bone Gorge) or locality was named after numerous findings
of Pliocene mammal bones in the secondary maar filling; it is
one of the type localities of the European Mammal time scale
Zone MN16 (Vass et al. 2000). Relicts of the primary volcanic
ring are preserved on the NW rim of the maar structure,
formed by alkali basaltic lapilli tuff layers with fragments and
blocks of sandstone. The central depression of the maar struc-
ture is filled by a primary and secondary lacustrine maar fill-
ing which consists of tuffitic siltstones to sandstones and
resedimented sand (Vass et al. 2000). The sapphires were dis-
covered together with other heavy minerals and remnants of
mammal skeleton fragments in the secondary sandy filling.
Correlation of magnetostratigraphic and paleontological data
indicate an age of phreatomagmatic volcanic activity and maar
formation at 3.3 to 3.55 Ma, whereas paleontological data
constrain the age of the secondary maar filling to Villafran-
chian (the latest Pliocene), within the MN16a Zone, between
2.8—3.3 Ma (Vass et al. 2000).
The first corundum found in Hajnáčka, Kostná valley is a
grey-blue flat tabular crystal, 7 mm across, cemented by a
yellow-brown weathered crust of basalt (Szádeczky 1899).
New specimens of sapphire crystals were described in the
psammitic sedimentary filling of the Hajnáčka maar (Uher et
al. 1999). The sapphire associates with other heavy minerals
identified in sandy filling of the Hajnáčka maar structure
such as spinel, magnetite, magnesiochromite, ilmenite, titan-
ite, forsterite, zircon, almandine, allanite-(Ce), augite, diop-
side, enstatite, pargasite, and kaersutite (Uher et al. 1999;
Gregáňová 2002).
The sapphire from Gortva forms euhedral crystals en-
closed in syenitic/anorthoclasitic rock xenolith in alkali ba-
salt (Szakáll et al. 2002; Uher et al. 2006). The locality is
situated on Guda (Buda) Hill (413 m a.s.l.), 1800 m N of
Gortva settlement and ca. 6 km N of the Hajnáčka, Kostná
Fig. 1. Simplified geological map of studied area with location of
sapphire occurrences (Vass et al. 1992a, adapted). Explanations:
1 – Quaternary sediments (sands, loess, gravels, clays, loams),
2 – Miocene sandstones; Pliocene—Pleistocene: 3 – basalt lava
flows, 4 – agglomerates, tuffs and lapilli tuffs, diatreme fill (shales,
sandstones and tuffs with non-volcanic material), 5 – lava necks and
dikes, 6 – sample location: Hajnáčka, Kostná valley (placer) and
Gortva, Guda Hill (xenolith).
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valley sapphire locality. The adjacent alkali basalts form a
lava flow, locally with small xenoliths (usually 1 to 5 cm
across) of felsic magmatic rocks. The K-Ar whole-rock dating
of alkali basalt from the Gortva, Guda Hill gave Pleistocene
age of 1.73 ± 0.1 Ma (Vass et al. 2000).
An additional finding of corundum has been reported in a
syenitic xenolith in alkali basalt from the Pliocene maar at
Pinciná near Lučenec town in the northern part of the Cerová
Highlands (Hurai et al. 1998).
Experimental methods
Sapphire crystals were isolated from the heavy mineral as-
semblage of ca. 1000 kg sand portion from secondary maar
filling of the Hajnáčka, Kostná valley. In addition, a sap-
phire-bearing xenolith in alkali basalt from Gortva, ca. 6 km
N of Hajnáčka, deposited in the Herman Ottó Museum, Mis-
kolc, Hungary (inv. No. 14035), and mentioned by Szakáll
et al. (2002) was investigated here.
The internal texture of the sapphire crystals was studied
using cathodoluminescence at the Dionýz Štúr State Geolo-
gical Institute, Bratislava, using an acceleration voltage of
18 kV and a sample current of 80 nA.
Electron-microprobe analyses (EMPA) were carried on the
CAMECA SX100 probe at the Dionýz Štúr State Geological
Institute, Bratislava. The following operating conditions
were used: acceleration voltage of 15 kV, beam current of
20 nA (10 nA for analcime), beam diameter between 3 to
10 m, and a collection times of 20 to 40 s in wavelength
dispersive mode. Standards and lines included wollastonite
(Si K , Ca K ), TiO
2
(Ti K ), Al
2
O
3
(Al K ), chromite
(Cr K ), fayalite (Fe K ), rhodonite (Mn K ), MgO
(Mg K ), SrTiO
3
(Sr L ), barite (Ba L ), albite (Na K ),
orthoclase (K K ), Rb
2
ZnSi
5
O
12
glass (Rb L ) and LiF (F K )
for the other minerals. The detection limits of measured ele-
ments range from 0.02 to 0.1 wt. %, and statistical errors
from 0.02 to 0.1 wt. % (1 ), depending on the elemental
concentration. The PAP routine (Pouchou & Pichoir 1985)
was applied for data correction.
Selected trace elements of sapphire were investigated by
LA-ICP-MS at the Department of Chemistry, Faculty of
Science, Masaryk University, Brno, using a laser ablation
system UP 213 (New Wave, USA) and an ICP-MS spec-
trometer Agilent 7500 CE (Agilent, Japan). A commercial
Q-switched Nd: YAG laser ablation device works at a wave-
length of 213 nm. A sample was placed in the SuperCell
(New Wave, USA). The ablated material was carried with
helium (carrier gas), which transported the laser-induced
aerosol to the inductively coupled plasma (1 l/min). A sam-
ple gas flow of argon was admixed to the helium carrier gas
flow after the laser ablation cell. Therefore, the total gas flow
was 1.6 l/min. Optimization of LA-ICP-MS conditions (gas
flow rates, sampling depth, electrostatic lenses voltages of
the MS) was performed with the glass reference material
NIST SRM 610 in respect to maximum S/N ratio and mini-
mum oxide formation (ThO
+
/Th
+
counts ratio 0.2 %, U
+
/Th
+
counts ratio 1.1 %). The LA-ICP-MS measurements used a
single hole drilling mode for the duration of 60 seconds for
each spot. Laser ablation was performed with laser spot dia-
meter of 100 m, laser fluency of 12 J · cm
—2
and repetition
rate of 10 Hz. All element measurements were normalized
on
27
Al (526,609 ppm Al = 99.5 wt. % Al
2
O
3
; this value ap-
proximates to the real composition of the studied sapphire).
Oxygen isotope values of sapphire were determined at the
SUERC, Glasgow, United Kingdom, using the laser fluori-
nation technique described by Sharp (1990). The method in-
volves complete reaction of ~ 1 mg of powdered sapphire,
heated by a CO
2
laser, with ClF
3
as the fluorine reagent. The
released oxygen is passed through an in-line Hg-diffusion
pump before conversion to CO
2
on platinized graphite. The
yield is measured by a capacitance manometer and the gas-
handling vacuum line is connected to the inlet system of a
dedicated VG PRISM3 dual inlet isotope ratio mass spec-
trometer. Precision and accuracy on quartz standards are
± 0.1 ‰ (1 ) and duplicate analyses of sapphire sample con-
firm this error range. Data are reported in the conventional
delta notation (
18
O, expressed as
18
O/
16
O, ‰) relative to the
Vienna Standard Mean Ocean Water (V-SMOW).
Results
Physical properties, internal zoning and mineral associa-
tion of sapphires
Sapphire crystals or their fragments in psammitic sedi-
mentary filling of the Hajnáčka maar show common hexago-
nal prismatic {1010} and pinacoidal {0001} faces, locally
also with {1011} dipyramids. Locally, basal cleavage along
the (0001) plane is visible (Fig. 2d). Optical photomicro-
graphs and especially CL images show apparent fine oscilla-
tory zoning along the (1010) plane of the sapphire (Figs. 2
and 3). Sapphire crystals are transparent with glassy to dia-
mond lustre. The Hajnáčka sapphires have three basic co-
lours: the most common are light to dark blue, scarcer are
grey-pink and pale pink crystals (Fig. 2). Some pink crystals
show concentric colour zoning with a darker bluish or violet
central zone and pale pink external zone (Fig. 2c) and visible
pleochroic (dichroic) colour change from darker to lighter
pink. Locally, sapphire contains tiny inclusions of zircon,
rarely ilmenite, and hercynite to spinel overgrowths. One blue
sapphire crystal also contains inclusions of monazite-(Ce),
iron sulphide (pyrrhotite?), and Y-U-Th-Nb-Ta oxide mineral,
probably euxenite-(Y)? (Uher et al. 1999).
Sapphire in the Gortva syenite/anorthoclasite xenolith
forms 0.5 to 3.5 mm euhedral hexagonal deep blue crystals
( ~ 5—10 vol. %) in white several cm-sized syenite to
anorthoclasite xenolith in alkali basalt (Fig. 2a). Under CL
image, the sapphire shows fine oscillatory zoning along the
(1010) plane. The composition of the alkali feldspar is
Ab
63—67
An
24
Or
10—13
(Table 1). Fibres of the Al
2
SiO
5
-phase,
probably sillimanite form a corona 0.1 to 0.4 mm thick be-
tween the sapphire and the feldspar (Fig. 4a,b). It probably
formed during post-magmatic contact re-equilibration be-
tween corundum and alkali feldspar, possibly during heating
of the xenolith by the hot alkali basalt lava. Leucite occurs as
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Fig. 2. Photographs of sapphire: a – Blue sapphire crystals (0.5 to 3.5 mm across) with white corona of sillimanite (?) in syenite/anortho-
clasite xenolith in alkali basalt, Gortva; b – Blue sapphire crystal (3 mm across) with colour oscillatory zoning, Hajnáčka placer; c – Pink
sapphire crystal (2 mm across) with fine colour oscillatory zoning, Hajnáčka placer; d – Pink sapphire with bluish-violet central part
(4 mm in size) and apparent basal cleavage along the (0001) plane, Hajnáčka placer.
Fig. 3. CL images of sapphire crystals with apparent fine oscillatory zoning: a – Blue sapphire, Hajnáčka placer; b – Pink sapphire with
tiny white zircon inclusions, Hajnáčka placer.
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Table 1: Representative electron-microprobe compositions of minerals in syenite/anorthoclasite xenolith in alkali basalt from Gortva (wt. %).
subhedral crystals (0.1 to 0.5 mm in size) in association with
K-feldspar, pyroxene and Ti-rich magnetite. Feldspar com-
position in leucite- and pyroxene-rich areas changes to
Na,K-rich,
anorthoclase
or
sanidine-like
members
(Ab
51—59
An
02—07
Or
34—46
), enriched in Ba (0.5 to 1.3 wt. %
BaO – Table 1). Pyroxene forms 20 to 150 m long colum-
nar crystals of diopside (wollastonite
47—51
, clinoenstatite
34—43
,
clinoferrosilite
09—19
; Table 1). Locally, analcime forms fill-
ings in feldspar + pyroxene groundmass (Fig. 4a). The pre-
vailing Na,K-feldspar, the lack of quartz and the presence of
pyroxene indicate a syenitic or anorthoclasitic character for
the sapphire-bearing xenolith. Unfortunately, the small size
of the studied xenolith precludes making a more detailed
petrographic and whole-rock geochemistry investigation.
Sillimanite? Plagioclase Anorthoclase Diopside Diopside Diopside Leucite Analcime
SiO
2
36.87 61.89 64.09 52.69
51.46
50.41
55.60
56.47
TiO
2
0.00
0.82
1.28
1.62
0.14
Al
2
O
3
62.06 23.52 19.77 1.66
2.42
1.82
22.58
23.02
Cr
2
O
3
0.05
0.04
0.02
0.00
Fe
2
O
3
0.24
0.00
0.29
0.34
0.27
FeO
5.75
6.19
10.95
MnO
0.03
0.20
0.18
0.33
MgO
0.00
0.00
0.00
15.15
14.46
11.57
0.00
CaO
0.00
5.05
1.30
23.81
23.34
22.27
0.02
0.22
SrO
0.27
BaO
1.25
Na
2
O
0.00
7.26
6.57
0.48
0.47
0.61
0.08
11.04
K
2
O
0.03 2.28 5.75 0.06
0.03
0.21
21.12
1.33
Rb
2
O
0.04
Total
99.28 100.00 99.33 100.66
99.85
99.79
99.74
92.49
Anions pfu
5
8
8
6 6 6 6 6
Si
1.002
2.762
2.921
1.937
1.912
1.917
2.022
2.042
Ti
0.000
0.023
0.036
0.046
0.004
Al
1.987
1.237
1.062
0.072
0.106
0.082
0.968
0.981
Cr
0.001
0.001
0.001
0.000
Fe
3+
0.005
0.000
0.010
0.009
0.007
Fe
2+
0.177
0.192
0.348
Mn
0.001
0.006
0.006
0.011
Mg
0.000
0.000
0.000
0.830
0.801
0.656
0.000
Ca
0.000
0.241
0.063
0.938
0.929
0.908
0.001
0.009
Sr
0.007
Ba
0.022
Na
0.000
0.628
0.580
0.034
0.034
0.045
0.006
0.774
K
0.001
0.130
0.334
0.003
0.001
0.010
0.980
0.061
Rb
0.001
Cation sum
2.997
4.998
5.000
4.021
4.018
4.023
3.986
3.878
Fig. 4. BSE images of the sapphire-bearing syenite/anorthoclasite xenolith from Gortva: a – Corundum (sapphire) crystal (Crn) rimmed
by a sillimanite (?) corona (Sil) associated with anorthoclase (Fls), diopside (Di) and analcime (Anl); b – Detail of sillimanite (?) fibres
(Sil) formed at the contact between anorthoclase (Fls) and the sapphire (Crn).
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Table 2a: LA-ICP-MS analyses of sapphire (ppm). Clastic sapphire from sedimentary filling of the Hajnáčka maar.
Chemical composition and oxygen isotopic characteristics
of sapphires
The concentrations of Mg, Ti, V, Cr, Mn, Fe, Ga, and Zr in
the coloured sapphires from the Hajnáčka placer and the sap-
phire-bearing syenite/anorthoclasite xenolith from Gortva
are given as LA-ICP-MS spot analyses (Table 2):
Iron shows the highest concentrations in coloured sapphires
from the Hajnáčka placer: ca. 830 to 2300 ppm; and averages
1550, 1930, and 1000 ppm Fe for blue, grey-pink and pink vari-
eties, respectively (Table 2a). The blue sapphires contain higher
Ti (mean ~ 510 ppm) in comparison to the grey-pink and espe-
cially the pink varieties ( ~ 420 and ~ 290 ppm in average). The
pink sapphires show the highest average concentrations of Cr
and V, 191 and 37 ppm, in comparison to 93 and 32 ppm in the
grey-pink, and < 39 (usually < 2 ppm) and 12 ppm in the blue
sapphires, respectively (Table 2a). Average Mg concentrations
attain 16, 49, and 27 ppm in blue, grey-pink and pink varieties,
respectively. Contents of Ga are similar in the all colour variet-
ies (42 to 45 ppm in average). The concentrations of Be, Mn, Zr
and other measured elements (Li, B, Sc, Co, Y, and Hf) were
usually below the detection limit of LA-ICP-MS.
Blue sapphires from the Gortva syenite/anorthoclasite xe-
nolith have iron contents between ca. 2100 and 3400 ppm
(mean ~ 2700 ppm), Ti concentrations vary between ~ 130
and averages ~ 2400 ppm, ~ 1200 ppm (Table 2b). The con-
tents of Cr are <2 ppm and those of Ga are constant in the
range 71—97 ppm (mean 82 ppm). Vanadium contents are
between 40 and 94 ppm (58 ppm on average) and Mg be-
tween 16 and 148 ppm (mean 61 ppm).
The
18
O-values (V-SMOW) of two blue sapphires from
the placer of Hajnáčka are 3.80 and 5.85 ± 0.1 ‰ respective-
ly. The
18
O-value of the blue sapphire from the syenite/an-
orthoclasite xenolith of Gortva is 5.1 ± 0.1 ‰ (n = 3).
Discussion
Composition of sapphires: magmatic versus metamorphic
origin
The Fe, Ti, Cr, Ga, Mg contents and chemical ratios such as
Ga/Mg, Fe/Ti, Fe/Mg and Cr/Ga of the corundum xenocrysts
or corundum-bearing xenoliths carried by continental alkali
Crystal Colour Spot
Mg Ti V Cr Mn Fe Ga Zr
Fe/Ti
Cr/Ga
Ga/Mg
Fe/Mg
1
blue
1
9
618
5
<2
<2
1455
42
<0.2 2.4
4.8
164
1
blue
2
11
770
5
<2
<2
1512
42
0.5 2.0
3.8
136
1
blue
3
15
907
5
<2
4
1789
45
<0.2 2.0
3.0
119
1
blue
4
17
735
6
<2
<2
2301
53
0.4 3.1
3.1
135
1
blue
5
21
600
10
<2
<2
1522
50
1.0 2.5
2.4
74
4
blue
1
7
309
9
8
<2
1283
43
<0.2 4.2
0.18
5.9
177
4
blue
2
9
51
10
16
<2
1410
44
<0.2 27.4
0.36
5.1
164
4
blue
3
13
24
12
31
<2
1598
49
<0.2 67.3
0.62
3.7
121
4
blue
4
13
23
10
32
<2
1445
47
<0.2 64.0
0.68
3.6
112
4
blue
5
13
21
11
39
<2
1517
48
<0.2 71.3
0.81
3.7
118
4
blue
6
6
201
8
17
<2
1250
42
<0.2 6.2
0.41
6.7
199
5
blue
1
4
798
5
<2
28
1670
36
0.2 2.1
9.8
456
5
blue
2
4
839
5
<2
20
1717
32
0.2 2.0
8.8
469
5
blue
3
4
934
5
<2
67
1868
29
<0.2 2.0
6.9
437
5
blue
4
5
1107
7
<2
62
2181
38
<0.2 2.0
7.6
432
3
blue
1
29
475
23
<2
<2
1318
40
<0.2 2.8
1.4
46
3
blue
2
31
525
25
<2
<2
1417
41
<0.2 2.7
1.3
46
3
blue
3
43
677
25
<2
6
1462
41
<0.2 2.2
1.0
34
3
blue
4
35
599
23
<2
<2
1277
37
<0.2 2.1
1.1
37
3
blue
5
29
451
22
<2
<2
1318
39
<0.2 2.9
1.3
45
3
blue
6
22
335
21
<2
<2
1359
43
<0.2 4.1
1.9
62
3
blue
7
18
196
19
<2
<2
1335
42
<0.2 6.8
2.4
75
6
grey-pink
1
31
208
26
82
8
1722
40
<0.2 8.3
2.03
1.3
56
6
grey-pink
2
61
584
39
119
24
1975
49
0.2 3.4
2.44
0.8
32
6
grey-pink
3
67
529
34
33
12
2079
47
<0.2 3.9
0.70
0.7
31
6
grey-pink
4
38
362
29
139
<2
1925
44
<0.2 5.3
3.14
1.2
50
2
pink
1
10
45
24
162
<2
828
42
<0.2 18.2
3.83
4.3
84
2
pink
2
11
73
26
173
<2
959
39
<0.2 13.1
4.42
3.7
89
2
pink
3
13
113
29
187
<2
981
42
<0.2 8.7
4.43
3.3
77
2
pink
4
36
742
39
164
<2
1099
48
<0.2 1.5
3.44
1.3
31
2
pink
5
44
306
56
308
<2
1131
49
<0.2 3.7
6.23
1.1
26
2
pink
6
41
318
52
256
<2
1096
45
<0.2 3.4
5.64
1.1
27
2
pink
7
53
547
48
153
<2
1124
50
<0.2 2.1
3.08
0.9
21
2
pink
8
28
401
33
161
<2
991
45
<0.2 2.5
3.56
1.6
35
2
pink
9
11
83
26
155
<2
847
37
<0.2 10.2
4.17
3.3
75
detection limit
2
9
1
2
2
6
1
0.2
blue sapphire (average)
16
509
12
<39
<67
1546
42
<1.0 12.9
0.1
4.1
96
grey-pink sapphire (average)
49
421
32
93
<24
1926
45
<0.2 5.2
2.1
1.0
39
pink sapphire (average)
27
292
37
191
<2
1006
44
<0.2 7.0
4.3
2.3
37
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basalts are used to discuss their magmatic versus metamorphic
origin (e.g. Sutherland et al. 2002, 2009; Garnier et al. 2005;
Zaw et al. 2006; Peucat et al. 2007). Generally, Fe and Ga re-
veal higher concentrations in magmatic sapphires ( ~ 1800 to
13,000 ppm Fe and ~ 70 to 570 ppm Ga), than in metamor-
phic ones which have Fe and Ga contents less than 3000 and
75 ppm, respectively. In contrast, low Cr and Mg contents are
typical for magmatic sapphires (both usually < 40 ppm),
whereas gem corundum of metamorphic origin is enriched in
these elements (both generally > 60 ppm). Therefore, the
Ga/Mg ratio is commonly > 6 in magmatic sapphires and < 3
in metamorphic ones. Conversely, the Cr/Ga ratio is < 0.1 for
magmatic sapphires and > 1 for metamorphic sapphires. The
Fe/Ti ratio is generally higher in magmatic than metamorphic
sapphires. The Fe/Mg ratio is significantly higher for magmatic
sapphires (Fe/Mg > > 100) and lower for metamorphic and
metasomatic ones (Fe/Mg < 100; Peucat et al. 2007).
The sapphires from the Hajnáčka placer and the Gortva sy-
enite/anorthoclasite show relatively low to medium Fe and
Ga contents, indicating a rather metamorphic affinity despite
the petrological evidence of a magmatic origin for the syen-
ite/anorthoclasite xenolith. The low Mg concentrations of
Hajnáčka (4 to 67 ppm) are more characteristic of magmatic
Table 2b: LA-ICP-MS analyses of sapphire (ppm). Sapphire from syenite/anorthoclasite xenolith in alkali basalt from Gortva.
suites while those of Gortva (16 to 148 ppm) suggest meta-
morphic ones (Table 2a—b). The Cr contents are comparable
both to magmatic and metamorphic groups (commonly
< 2 ppm for blue, 33—140 ppm for grey-pink, and 153—
308 ppm for pink varieties).
The range and mean Fe/Ti, Cr/Ga, Ga/Mg, and Fe/Mg val-
ues also indicate bimodal origins, with stronger affinity of
blue sapphires (both Hajnáčka and Gortva) to magmatic do-
main, and of grey-pink and pink sapphires more related to
the metamorphic one. The Ga/Mg vs. Fe diagram (Peucat et
al. 2007; Sutherland et al. 2009) shows both magmatic and
metamorphic origins for the Hajnáčka and Gortva sapphires
(Fig. 5a). The Fe/Ti vs. Cr/Ga diagram (Sutherland et al.
2009) is the equivalent of the Fe
2
O
3
/TiO
2
vs. Cr
2
O
3
/Ga
2
O
3
diagram proposed by Sutherland et al. (1998) for classifica-
tion of corundum in the alkali basalts domain. The diagram
separates efficiently the metamorphic from the magmatic co-
rundum (Sutherland et al. 2003), it indicates that the Gortva
sapphires differs from the Hajnáčka ones, and they plot obvi-
ously in the field of the magmatic sapphires in agreement
with their petrological nature (Fig. 5b). The Gortva sapphires
have a Ga content in the range of the magmatic sapphires
( > 70 ppm) but their Mg content is too high (up to 148 ppm)
Crystal Colour Spot Mg
Ti
V
Cr
Mn
Fe
Ga
Zr
Fe/Ti Cr/Ga Ga/Mg Fe/Mg
1 blue 1 96 1603 94 <0.2 9.4 3181 96 1.59 2.0
1.0 33
1 blue 2 98 1651 91 0.2 10.9 3304 97 0.76 2.0 0.002 1.0 34
1 blue 3 107 1800 86 0.4 5.7 3415 95 0.64 1.9 0.005 0.9 32
1 blue 4 86 1475 80 <0.2 1.7 3118 92 0.44 2.1
1.1 36
1 blue 5 78 1936 63 0.3 6.8 2992 85 0.32 1.5 0.003 1.1 38
1 blue 6 75 1808 65 0.5 4.2 2984 85 0.17 1.7 0.006 1.1 40
1 blue 7 72 2240 59 0.4 0.7 2857 83 0.12 1.3 0.005 1.2 40
1 blue 8 71 2356 57 0.4 1.5 2841 81 0.18 1.2 0.005 1.1 40
1 blue 9 66 2053 54 <0.2 1.8 2634 78 0.13 1.3
1.2 40
1 blue
10 62 1826 53 0.3 1.3 2666 83 0.09 1.5 0.004 1.3 43
1 blue
11 45 1092 44 0.7 0.3 2577 76 0.08 2.4 0.009 1.7 57
1 blue
12 50 1423 49 0.6 0.5 2582 78 0.10 1.8 0.008 1.6 52
1 blue
13 52 1559 52 0.6 0.5 2595 77 0.08 1.7 0.008 1.5 50
1 blue
14 46 1177 57 1.6 <0.2 2643 80 0.04 2.2 0.020 1.7 57
1 blue
15 34 778 56 2.5
<0.2
2436 76 0.03
3.1
0.032 2.3 72
1 blue
16 16 174 46 6.8
<0.2
2185 74 <0.01
12.5
0.092 4.6 137
1 blue
17 16 127 41 2.6
<0.2
2073 76 0.01
16.3
0.034 4.8 132
1 blue
18 75 1669 66 0.3 2.4 2838 84 0.25 1.7 0.004 1.1 38
1 blue
19 106 2385 83 0.3 2.7 3339 95 1.16 1.4 0.003 0.9 31
1 blue
20 92 1611 74 <0.2 <0.2 3297 94 0.33 2.0
1.0 36
1 blue
21 82 947 60 0.3
<0.2
3034 92 0.06
3.2
0.003 1.1 37
1 blue
22 64 944 66 0.4
<0.2
3106 91 0.04
3.3
0.005 1.4 49
2 blue
1 31 606 46 0.6 0.5
2417 78 0.05
4.0
0.008 2.5 77
2 blue
2 69 535 44 1.2 0.3
2451 80 0.02
4.6
0.015 1.2 36
2 blue
3 21 300 40 1.0
<0.2
2320 76 <0.01
7.7
0.013 3.6 110
2 blue
4 23 357 42 1.3 0.3
2404 78 <0.01
6.7
0.016 3.4 106
2 blue
5 35 734 45 1.8 0.3
2515 78 0.04
3.4
0.023 2.2 71
3 blue
1 37 910 53 3.1 0.4
2495 71 0.04
2.7
0.044 1.9 67
3 blue 2 148 1019 54 2.4 0.3 2626 77 0.04 2.6 0.031 0.5 18
3 blue 3 60 1847 57 1.4 <0.2 2781 79 0.06 1.5 0.018 1.3 47
3 blue
4 27 506 47 3.6
<0.2
2369 75 0.01
4.7
0.048 2.8 88
3 blue
5 29 241 45 2.4
<0.2
2292 78 0.00
9.5
0.031 2.7 79
3 blue 6 48 1187 56 6.7 3.8 2245 77 0.33 1.9 0.088 1.6 47
3 blue 7 41 1092 57 3.0 <0.2 2680 81 0.03 2.5 0.037 1.9 65
detection limit
0.1 0.6 0.1 0.2 0.2
0.4 0.04 0.01
average
61
1234
58
1.6 2.6
2714
82
0.23
3.5
0.021
1.8
57
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to assure a Ga/Mg ratio typical of a magmatic origin. The
blue sapphires from Bo Phloi in Thailand have shown a sim-
ilar trend, namely both metamorphic and magmatic domains
(Peucat et al. 2007) despite their magmatic origin.
The Fe—Mg*100—Ti*10 triangular diagram defined by
Peucat et al. (2007) indicates a metamorphic affinity for the
whole sapphires (Fig. 5c). Conversely, the Cr*10—Fe—Ga*100
triangular diagram (Sutherland et al. 2009) shows a magmatic
origin for the blue sapphires from both studied occurrences,
and an undefined origin for the grey-pink and pink sapphires
from Hajnáčka, out of the defined magmatic or metamorphic
fields (Fig. 5d). Therefore, both diagrams using Ga/Mg ratio
or Mg (Fig. 5a,c) reveal different results in comparison to the
diagrams which apply Cr and Ga as discriminating elements
(Fig. 5b,d). Consequently, the Hajnáčka and Gortva sap-
phires belong to the “problematic” or “debatable origin”
group (Peucat et al. 2007), related to magmatic environment
but with both magmatic and metamorphic or metasomatic
geochemical features. Similar occurrences include mixed
metamorphic/magmatic sapphire suites from eastern Austra-
lia (Sutherland et al. 2002), Rio Mayo sapphires, Colombia
(Sutherland et al. 2008), as well as lamprophyre-related
Yogo Gulch (Montana, USA), and basalt-related Bo Phloi
(Thailand) sapphires (Peucat et al. 2007). In such cases,
contents of some trace elements, especially Mg, did not
effectively differentiate magmatic from metamorphic
blue sapphires.
Recently Giuliani et al. (2010) proposed the use of the
FeO—Cr
2
O
3
—MgO—V
2
O
3
vs. FeO + TiO
2
+ Ga
2
O
3
diagram
(Fig. 6a) for the classification of primary deposits. This dia-
gram uses Fe (FeO) as a major or a minor trace element of
corundum; the FeO content enables us to discriminate
between the two main types of ruby namely iron-poor rubies
in marbles and iron-rich rubies in mafic-ultramafic rocks
(Pham Van et al. 2004). The second device used for the
discrimination of ruby and sapphire is the addition (parame-
ter on the X-axis) or subtraction to FeO (parameter on the
Y-axis) of trace elements associated preferentially with ruby
(Cr
2
O
3
, V
2
O
3
, and MgO) or sapphire (TiO
2
and Ga
2
O
3
). The
different types of gem corundum deposit are: for ruby, mar-
ble (R1); John Saul Ruby Mine (Kenya) type (R2); mafic
and ultramafic rocks (R3); metasomatites (R4); for sapphire,
syenitic rocks (S1); metasomatites (S2); xenocrysts in alkali-
basalt and lamprophyre (S3). The domains of R4 and S2
which correspond to metasomatic-metamorphic corundum
are overlapping.
The FeO—Cr
2
O
3
—MgO—V
2
O
3
vs. FeO + TiO
2
+ Ga
2
O
3
dia-
gram (Fig. 6a—b) suggests a metasomatic-metamorphic ori-
gin for the Hajnáčka alluvial sapphires (field S2). The
chemical composition fits into the domain of sapphires
(Fe > Cr) related to biotitite developed in gneisses within
Fig. 5. Positions of blue, grey-pink and pink sapphires from
Hajnáčka placer in comparison to blue sapphire from Gortva
syenite/anorthoclasite xenolith in magmatic versus metamorphic
discrimination diagrams. Modified after Peucat et al. (2007) and
Sutherland et al. (2009), values are in ppm: a – Ga/Mg vs. Fe; b –
Fe/Ti vs. Cr/Ga; c – Fe—Mg*100—Ti*10; d – Cr*10—Fe—Ga*100.
79
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Fig. 6. a – FeO—Cr
2
O
3
—MgO—V
2
O
3
versus FeO+TiO
2
+Ga
2
O
3
diagram (in
wt. %) used for the geological classification of the corundum deposits. The
main fields defined for these different types of deposit worldwide are reported
(Giuliani et al. 2010); b – Chemical distribution of the coloured sapphires
from Hajnáčka and Gortva in the diagram.
shear zones such as the Sahambano and Zazafotsy deposits,
Madagascar (Rakotondrazafy et al. 2008), blue sapphires
from the skarn deposit of Andranondambo, Madagascar
(Giuliani et al. 2007), and sapphires in plumasites, that is de-
silicated pegmatites in ultramafic-rocks from Umba in Tan-
zania (Seifert & Hyršl 1999). They are clearly outside of the
field of sapphires associated with syenites but they plot in
the field of corundum xenocrysts associated with alkali-ba-
salts worldwide (field S3) and towards the low Cr-Mg-V-Ti
and Ga-bearing sapphires in metasomatites.
The sapphires from the Gortva xenolith do not plot in the
S1 magmatic domain defined for syenites (Fig. 6a) in con-
trast to the blue sapphires from the anorthoclasites
of Menet in the French Massif Central and Kian-
janakanga in central Madagascar (Rakotosamiza-
nany 2009a,b). The representative points of the
Gortva sapphires indicate a trend crosscutting the
domains S2 (metasomatic) and S3 (xenocrysts in
alkali-basalt and lamprophyre). Consequently, the
FeO—Cr
2
O
3
—MgO—V
2
O
3
vs. FeO + TiO
2
+ Ga
2
O
3
diagram ambiguously indicates metasomatic or
magmatic origin of the Hajnáčka and Gortva sap-
phires again.
Different geochemical diagrams applied to the
Hajnáčka and Gortva sapphires illustrate the com-
plexity of the use of classification for sapphires
which have special composition and representa-
tive chemical field overlapping the limits of meta-
morphic and magmatic domains (Figs. 5a—d, 6).
The diagrams are the result of the combination of
the chemical composition with the type of deposit
which is sometimes not well defined.
Oxygen isotopes of sapphire
The
18
O value in gem corundum represents a
useful tool for deciphering its geological origin
(Yui et al. 2003, 2006; Giuliani et al. 2005, 2007,
2009; Garnier et al. 2005; Zaw et al. 2006; Suther-
land et al. 2009). As the mantle and crustal rocks
show distinct oxygen isotope compositions, the
18
O value enables us to investigate the origin and
source of corundum. Several principal genetic
groups can be subdivided based on sapphire
18
O
values (Giuliani et al. 2007): pink sapphires host-
ed in cordieritite (
18
O = 1.7 to 2.9 ‰), coloured
and blue sapphires in lamprophyre (
18
O = 5.4 to
6.8 ‰), in syenitic rocks (4.4 to 8.3 ‰), in desili-
cated pegmatites associated with amphibolites and
pyroxenites (4.2 to 7.5, locally to 11.2 ‰), in bi-
otitite in gneiss (4.6 to 9.0 ‰), in calc-silicates
and skarns (7.7 to 10.7 ‰), in desilicated pegma-
tites in marble (15.5 to 15.9 ‰), and blue-reddish
sapphire with ruby in marble (16.3 to 22.3 ‰).
The
18
O measurements of blue sapphires from
Hajnáčka (3.80 and 5.85 ‰) fit into the ranges of
sapphires originating from mantle-related magmat-
ic rocks such as lamprophyres and syenitic rocks,
as well as desilicated pegmatites in mafic rocks or
biotitite in gneiss. The
18
O values are different from those of
sapphires in Ca-rich metamorphic rocks, mainly skarns and
marbles (
18
O > 9 ‰; Giuliani et al. 2005, 2007; Zaw et al.
2006). Additional O-isotopic composition of sapphires from
biotitites in gneiss from Madagascar are presented in order to
complete an earlier database (Giuliani et al. 2005, 2007,
2009). The sapphires from Ionavo located in the south of the
Sahambano deposit have
18
O of 4.5, 4.0 and 3.3 ‰ respec-
tively (Fig. 7). The
18
O measurements of both Hajnáčka sap-
phires overlap the
18
O-range of sapphires in (i) biotitite
formed in gneiss such as those of the Sahambano, Zazafotsy
and Ionaivo deposits in Madagascar (
18
O = 3.3 to 9.0 ‰,
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mean
18
O = 6.1 ± 1.8 ‰, n = 11) or (ii) plumasite in ultramafic
rocks such as the Umba deposit in Tanzania (
18
O = 5.4 to
6.7 ‰; n = 3; Giuliani et al. 2005).
The
18
O-value of 5.1 ‰ obtained for the blue sapphire in
the syenite/anorthoclasite xenolith from Gortva fits into the
18
O-range of sapphires associated with syenites/anorthocla-
sites, and it is in agreement with the
18
O-values of 4.4 and
4.5 ‰ (Giuliani et al. 2005, 2009), respectively obtained for
the blue sapphires of Menet (France) and Kianjanakanga
(Madagascar) anorthoclasites (Fig. 7). This
18
O-value also
corresponds to the
18
O values obtained for olivine from
mid-ocean ridge (
18
O = 5.16 ‰), ocean island basalt
(
18
O = 5.17 ‰) and continental flood basalt (
18
O = 5.16 ‰;
Eiler et al. 1997; Baker et al. 2000). Sapphire genesis in fel-
sic melts by partial melting and/or metasomatism of mantle
spinel lherzolite with an original
18
O isotope composition
(5 to 6 ‰), has been proposed by several authors (Oakes et
al. 1996; Yui et al. 2003; Pin et al. 2006).
Possible genetic scenario of sapphire origin:
a summary
The oxygen isotopic composition of sapphire from the
Gortva syenite/anorthoclasite indicates that it was derived
from an igneous reservoir in the sub-continental spinel lher-
zolitic mantle. In the lithospheric mantle, felsic melts crystal-
lized to form anorthoclasites, the most evolved peraluminous
variant of the alkaline basaltic melt. This hypothesis is in
agreement with the genesis proposed for the anorthoclasitic
sapphires of Menet, France and Kianjanakanga, Madagascar
(Giuliani et al. 2009; Rakotosamizanany 2009a,b). However,
the chemistry of the sapphires from Hajnáčka and Gortva is
different from those of Menet and Kianjanakanga (Fig. 6a)
Fig. 7. Oxygen isotope values (
18
O) of sapphires from Hajnáčka placer and
Gortva syenite/anorthoclasite xenolith, with reference to the worldwide
18
O
database (Giuliani et al. 2005, 2007, 2009, this work). The diamond symbols
indicates the rubies (white), coloured sapphires and sapphires (black).
V-SMOW – Vienna Standard Mean Ocean Water.
especially for iron: they contain 2 or 3 times less
iron than the sapphires of the French and Mala-
gasy anorthoclasites. Their origin is similar but
the evolution of their parent magma is probably
quite different. The final product is an anorthocla-
site rich in Si, Al, K and Na but the quantity of iron
was probably different due to the precipitation of
iron-rich phase such as Ti-rich magnetite and bi-
otite. In the French Massif Central, Brousse &
Varet (1966) described different types of anortho-
clasite with diverse modal composition for iron-
bearing phases (maghemite-, almandine-, and
corundum-bearing anorthoclasite). Early mag-
matic precipitation of Fe-rich phases can explain
an origin of fractionated, iron depleted felsic melt
and crystallization of relatively Fe-poor sapphire
in the Hajnáčka and Gortva occurrences. The be-
haviour of the other elements, such as Ti, Ga, Cr,
V and Mg in the sapphires, could be discussed in
the same way by analysing their content in the dif-
ferent minerals of the host syenite/anorthoclasite.
The control of the final composition of the mag-
matic sapphires by the behaviour of the parent
magma during its crystallization can generate dis-
crepancies with the use of the chemical diagrams
of corundum classification as illustrated by the Hajnáčka and
Gortva sapphires.
Assuming our data, the blue sapphire from Gortva and
mostly also from Hajnáčka solidified from a fractionated
melt, probably in the upper mantle or lower crust before their
transport to the surface as syenite/anorthoclasite xenoliths
(or corundum xenocrysts) by alkali basalt lava. This model is
consistent with an origin of analogous felsic syenitic xeno-
liths from the nearby Pinciná maar, southern Slovakia, where
a fluid-inclusion and petrological study indicated a pressure
around 600 MPa (ca. 22 km of lithostatic load) and liquidus
temperature of inclusion melts at ~ 1080 °C (Huraiová et al.
1996). Similar models for corundum origin from upper man-
tle to lower crustal, fractionated syenitic/anorthoclasitic
magma are also proposed for other sapphire occurrences
(e.g. Coenraads et al. 1995; Sutherland et al. 1998, 2009;
Upton et al. 1999, 2009; Graham et al. 2008).
The genetic scenario of pink and grey-pink sapphires from
Hajnáčka is still unresolved, but their composition (mainly
higher Cr and Mg content) suggest a metamorphic (metaso-
matic) origin comparable to compositions of sapphires from
plumasites, skarns or biotitites developed in gneisses (Seifert
& Hyršl 1999; Giuliani et al. 2007; Rakotondrazafy et al.
2008). Xenoliths of Paleozoic gneisses and migmatites of the
Veporic Superunit in andesites from the vicinity of Hajnáčka
(Hovorka & Lukáčik 1972) indicate such a possility.
Acknowledgments: The authors thank reviewers Lin
Sutherland and Milan Novák, as well as Igor Broska, journal
editor, for their constructive criticism that improved the
manuscript. We also acknowledge Martin Ondrejka for tech-
nical support during figure draving. This work was support-
ed by the VEGA Grant No. 1/0287/08; TV and VS gratefully
acknowledge the Ministry of Education, Youth and Sports of
81
SAPPHIRES RELATED TO ALKALI BASALTS FROM THE CEROVÁ HIGHLANDS (S SLOVAKIA)
GEOLOGICA CARPATHICA
GEOLOGICA CARPATHICA
GEOLOGICA CARPATHICA
GEOLOGICA CARPATHICA
GEOLOGICA CARPATHICA, 2012, 63, 1, 71—82
the Czech Republic for supporting the research project with
RP identification code MSM0021622411 and Masaryk Uni-
versity rector’s grant MUNI/G0124/2009/SAMAS. Financial
support was also provided to SSz by Grant No: TÁMOP-4.2.1.
B-10/2/KONV-2010-0001.
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