Geochemical characteristics of barite occurrences in the Palaeozoic complex of South-eastern Bosnia and their relationship to the barite deposits of the Mid-Bosnian Schist Mountains

In Palaeozoic rocks of South-eastern Bosnia (SEB) there are numerous, but very small vein and replacement barite ore deposits containing up to 10% Pb-Zn-Fe-Cu sulphides. Their geochemical characteristics are compared with large barite monosulphide (Hg-tetrahedrite) ore deposits in Mid-Bosnian Schist Mountains (MBSM). The 87Sr/86Sr isotope ratios in the barites of both areas are very similar, (0.710972 and 0.714170 in SEB, 0.711764 and 0.712548 in MBSM), and indicate the epigenetic hydrothermal origin of the barite ore deposits. This conclusion is supported by the elevated Sr content in barites of both areas (0.48 to 2.83% in SEB, 1.44% in MBSM) and the δ13C and δ18O values in calcite and siderite of barite ore deposits which are shifted toward lower values relative to typical values occurring in the Devonian host rock. The δ18O values in barites from SEB (+14.2‰ to +15.6‰) are remarkably lower than those from MBSM (+15.8‰ to +22.4‰). This can be explained by the lower temperature and lower salinity of mineralisation fl uids in barite ore deposits of SEB. The δ34S values in barites of SEB are positive (+11.6‰ to 17.7‰), and enriched in heavy sulphur isotopes in comparison with sulphides of SEB (–0.41 to +4.26‰), whereas those in tetrahedrites are negative (–4.95 in SEB, –5.50 to –15.40‰ in MBSM) indicating two remarkably different sulphur sources and times of formation. Barite ore deposits of both areas, SEB and MBSM, have been genetically linked to fl uids that originated during Late Variscan S-type magmatism and metamorphism of Upper Proterozoic and Lower Palaeozoic rock complexes. However, later Post Variscan/Eoalpine heating processes affected signifi cant parts of barite ore deposits in MBSM. They caused fl uidization of sulphides in barite deposits, ascension of subcrustal deepseated fl uids enriched in H2S and mercury (± fl uorine), which passed through Upper Proterozoic and Caledonian ore deposits amalgamating their Au and Ag content leading to formation of a new mineral, Hg-tetrahedrite rich in Au (10–50 g/t) and Ag (1000 do 3000g/t).


INTRODUCTION
The biggest barite ore deposits in the whole Dinarides are located in the Mid-Bosnian Schist Mountains (MBSM).This Palaeozoic complex consists mostly of Lower Palaeozoic (Ordovician (?) -Silurian-Devonian) rocks and subordinately of Lower-Middle Carboniferous and Upper Permian rocks.These deposits are, regarding their mineral paragenesis, unique even on a global scale.The main mineral in the mineral paragenesis, in addition to barite and locally siderite, is Hg-Ag-Au-rich antimony tetrahedrite, named schwazite after the Schwaz locality, in Austria.Schneiderhöhn (1942) group ed this type of paragenesis as a separate genetic type.
Barite occurrences in the Palaeozoic complex of Southeastern Bosnia (SEB) represent the most South-eastern outcrops of numerous mineable barite deposits in the Dinarides (Fig. 1).Compared to numerous geochemical data of barites from MBSM only a few geochemical analyses of barites from SEB (PEZDIČ et al., 1977(PEZDIČ et al., /1979;;KUBAT et al., 1979KUBAT et al., / 1980) have been performed.
The aim of this study is to present the more comprehensive geochemical data on barite occurrences in SEB and compare them with those in the MBSM area.A model for the origin of the barite has been developed on the basis of trace elements, 87 Sr/ 86 Sr ratios, isotope composition of sulphur and oxygen in barites, carbon and oxygen in neocarbonates (neocalcite, neodolomite, neosiderite), and sulphur isotope composition in associated Pb, Zn, Cu, Sb and Fe sulphides.dolomitic limestone rock with conodonts.Sedimentation from the Upper Silurian continued into the Lower Devonian, but transitional deposits (S 3 -D 1 ) could not be separated.Sequences are composed of alevrolites, cherts, argilloschists, metasandstones, tuffi tes and marbleized limestone (KULE-NOVIĆ, 1986).
The Lower Devonian consists of alevrolites with chert (either independent small masses or intercalations in alevrolites), layered and bank limestones.This lower part of the Lower Devonian is overlain by sequences composed of cherts, diverse argilloschists, metasandstones and limestones among which very fossiliferous bank limestones occur.Chert breccias, metadiabases, schistose spilites, diabases and some red clastites are locally developed.According to KULE NOVIĆ (1986) granitoides occurring in the Odska River and Osanica, intruded between Lower and Upper Devonian or in the Upper Devonian.
The Upper Devonian is composed of limestone schists, cherts, chert breccias, ferrous sandstone and marbleized limestones.Tabular sericite-quartz schists mark the lower part of the Lower Carboniferous.They are overlain by phyllite schists with intercalations or lenses of schistose sandstones containing fossil fl ora of Lower Visean age.Fossiliferous Lower Carboniferous phyllites with black lydite inter calations are the next deposits in the sequence (KULENOVIĆ, 1986).
The uppermost, unfossiliferous part of the phyllite schists represents, the transition from the Lower to Middle Carboniferous according to KULENOVIĆ (1986).These are discordantly overlain by deposits of Upper Permian sandstones, schists, conglomerates and fossil-rich Bellerophone limestones.KRSTIĆ et al. (1988) discovered olistoliths and olistostromes composed of limestones and clastics in the "Culm fl ysch" in the Prača area.They stated that olistostrome formation is associated with very active tectonic zones, which caused the shearing and movement of large blocks such as Vlaška Stijena, Kiseljak, Klek and some others.ČIČIĆ (2002) and HRVATOVIĆ (2006) presented short over views of the stratigraphic development of quartz-porphyry in SEB.
The most widespread rocks of the Mid-Bosnian Schist Mountains (MBSM) are pre-Devonian metamorphic rocks (SOFILJ et al., 1980).MAJER et al. (1991) determined that they were formed by low grade metamorphism at 350°-Fi gu re 3: Geological map of the area between Fočanska Jabuka and Prača (after KULENOVIĆ, 1986).Circles denote the locations of barite samples analyzed here, whereas rectangles represent locations, which are undergoing analysis.400°C and a pressure of 3-5 kbars.Their crystallization age, obtained by K-Ar dating is 343 ± 13 Ma (PALINKAŠ et al., 1996).Fossiliferous Devonian carbonate rocks overlie this metamorphic complex (ŽIVANOVIĆ, 1972).The uplift of this area is related to the Hercynian orogeny and extrusions of rhyolites.Upper Permian continental and lagoonal deposits that unconformably overlie older Palaeozoic rocks, grade into Lower and Middle Triassic sediments.
Mineralization in the SEB Palaeozoic complex comprises small, but numerous barite deposits.They occur as irregular metasomatic barite bodies and epigenetic veins in the carbonate rocks, and contain traces or accessory amounts of Pb, Zn, and subordinantly Cu and Fe sulphides (Fig 4).Additionally, they occur as epigenetic barite veins located in metaclastites but enriched in sulphides (up to 10%).All sulphides have positive δ 34 S values (0 to +5‰).The rare younger Hg-Ag tetrahedrite is characterized by a negative δ 34 S value (-4.95‰).
The Hg-Ag-Au tetrahedrite deposits in the MBSM represent a peculiar and unique phenomenon in the whole Dinarides (KATZER, 1907;JURKOVIĆ, 1956).The Mačkara vein type is observed in pre-Devonian metamorphic rocks of the Gornji Vakuf area (JURKOVIĆ, 1960;JURKOVIĆ et al., 1994).The Kreševo vein and metasomatic irregular bodies are very widespread in the area composed of Devonian dolomites and limestones (JURKOVIĆ, 1996).
The Trošnik metasomatic type that occurs in the Fojnica-Bakovići area represents, at present, a unique exception among tetrahedrite-bearing barite deposits in MBSM.Its tetrahedrite is neither the main nor the unique sulphide mineral rich in mercury, but is subordinate to pyrite and chalcopyrite and characterized by traces of mercury and positive δ 34 S CDT values (JURKOVIĆ, 1958).

ANALYTICAL METHODS
Ore samples were collected from seven outcrops in SEB and ten outcrops in MBSM.Barites were hand-picked under binocular microscope and then crushed and powdered for chemical analyses in an agate mortar.
Trace elements were analysed by inductively coupled plasma (ICP) mass spectrometry in Acme Analytical Laboratories (Vancouver) Ltd in Canada.In order to use X-ray powder diffractometry (XRD), barite samples were powdered in an agate mortar.Diffractograms were recorded by a Philips diffractometer with counter and Cu-K α radiation at U =40 kV and I = 20 mA at the Institute of mineralogy, petrology and mineral resources at Faculty for Mining, Geology

Trace element composition of barite samples
Trace elements were analysed in six samples of pure barite from the Prača-Foča area in SEB and in one sample of pure barite from the Glumac deposit in the Kreševo area (K) in MBSM.Barite samples in SEB were collected in the Šarulje (Š), Jabukovik (J), Pale (P), Datelji (D), Dragosin Potok (DP) and Fočanska Jabuka (FJ) barite deposits.
The trace element contents of the analysed barites are listed in Table 1.They are generally present in very low concentrations.The values of 15 trace elements (Be, Ga, Nb, Sn, Th, U, W, Ho, Lu, Ag, As, Cd, Bi, Ti, Se) are below the detection limits of the analytical method in both areas.Five trace elements (Cs, Co, Nd, Mo, Er) only occur in the Glumac deposit (MBSM), whereas Au (1.2 ppm) is only detected in the Šarulje deposit (SEB).Of the 24 trace elements detected in the barites of both areas, 16 show similar values in both SEB and MBSM, 6 are slightly higher in MBSM and 2 trace elements (Zn and Ni) are signifi cantly higher in MBSM (Table 1).REEs are present in very low concentrations.Maximum total REE contents range from 5.25 to 12.17 ppm.(Table 1).The chondrite normalized (SUN & MC-DONOUGH, 1989) REE patterns of all analysed barites are shown in Fig. 5.The REE patterns are characterized by an enrichment of the LREE against the HREE such as Ho, Er, Tm, Yb and Lu (minimal La N /Yb N = 13.15 to 31.38).The Tm values in all barite deposits excluding Jabukovik and Dragosin Potok deposits are an exception to this statement.The REE patterns of all barite samples display a negative Ce anomaly (Ce/Ce* = 0.08 to 0.47).Signifi cant difference in the REE patterns of studied barites is visible only in Eu anomaly.Barites of the Jabukovik, Datelji and Šarulje de-posits are characterised by a negative Eu anomaly (Eu/Eu* = 0.45; 0.46 and 0.91 respectively), whereas those of the Dragosin Potok, Pale, Fočanska Jabuka and Kreševo deposits show positive anomaly (Eu/Eu* = 5.97; 24.17; 23.04; 19.08 respectively).

Ca content in barites
Minor substitution of Ca for Ba in the crystal lattice of barite is often observed.In the studied barites, the highest Ca content is found in the barite from the Šarulje deposit (1.31 %).The barite from the Datelji deposit contains 0.05 % Ca, in Kreševo area 0.03 % Ca and the barite from Dragosin Potok only 0.01 % Ca.Other studied barites are characterized by a Ca content which is below the detection limits of 0.01 % (Table 1).The X-ray analyses of the barites from Šarulje, Datelji and the Kreševo area reveal the presence of calcite as individual phase only in the barite from the Šarulje deposit (3.24 % CaCO 3 ).The Ca content in other Ca bearing barites is most probably substituted for Ba in the crystal lattice.Consequently, the barite from the Datelji deposit contains 0.17 % CaSO 4 , 0.10% in the Kreševo area and the barite from Dragosin Potok has 0.03 % CaSO 4 component.

Sr content in barites
In comparison to other foreign elements in the crystal lattice of barite, Sr is evidently enriched in all the studied barite.Its content varies from 0.48 to 2.83 % in the barites of SEB and in the barite from MBSM it is 1.44 % (Table 2).The Sr content of barites in Table 2 is additionally expressed as a SrSO 4 component.The obtained Sr value for barite of MBSM is in agreement with Sr values for 22 barite samples already published by Jurković et al. (1997), which range from 0.48 to 3.15% Sr (average 2.0%).The X-ray analyses of the barites revealed that their Sr content is the lowest in Šarulje deposit, the middle in Kreševo area and the highest in Fočanska Jabuka deposit, and demonstrated that strontianite (SrCO 3 ) as an individual phase does not exist in the barites.Accordingly, the presence of Sr in the barites could be explained by its substitution for Ba in the crystal lattice, and expressed as a SrSO 4 component.
Such a relatively high Sr content is typical for an ascending hydrothermal type of mineralization, whereas a low Sr content characterizes the volcano-sedimentary type of barite deposits.

Isotopic composition of sulphur (as sulphate) and oxygen in barites
The isotopes are analysed not only in the barites of previously mentioned localities in SEB and Kreševo area, but also in some other barite deposits in MBSM (Table 3).Sulphur isotope data in Table 3 are expressed relative to Canon Diablo troilite and oxygen isotope data relative to Vienna Standard Mean Ocean Water.
The sulphur isotopes (δ 34 S) in the barites from SEB span a narrow range, from +11.6‰ to +17.7‰ (mean +14.4‰).The only available δ 34 S analysis of the barite from the Šarulje deposit (PEZDIČ et al., 1977(PEZDIČ et al., /1979;;KUBAT et al., 1979KUBAT et al., , 1980) ) has a value of 12.4‰ and fi ts very well into the range determined here.Barites from MBSM also display a narrow range of δ 34 S values, varying between +10.1‰ and +16.8‰ (mean value = +11.8‰).This data is in accordance with the earlier published δ 34 S values from 22 barite samples from MBSM (JURKOVIĆ et al., 1997), which vary from +8.05‰ to +18.48‰ (mean value = +11.5‰).Regarding only the mean values, the barites from MBSM are characterized by a slight enrichment of the light sulphur isotope compared to the barites from SEB.
The oxygen isotope values (δ 18 O) shown in Table 3 represent the fi rst δ 18 O data for selected barites in the Dinarides.The barites from SEB have δ 18 O values within a narrow range, from +14.2‰ to +15.6‰ (mean +14.7‰).The barite samples from MBSM reveal remarkably higher δ 18 O values ranging from +15.8‰ to +22.4‰ (mean +18.47‰).The sulphur and the oxygen isotope data of the barites investigated in this study are summarized in Fig. 6.

Isotopic composition of carbon and oxygen in neominerals from SEB
The carbon (δ 13 C) and oxygen (δ 18 O) isotope ratios in the neominerals of the barite deposits from SEB are represented in Table 4.
The δ 13 C values are expressed relative to the Vienna Peedee Belemnite Standard (VPDB) and the δ 18 O values relative to both the Vienna Peedee Belemnite Standard (VPDB) and the Vienna Standard Mean Ocean Water (SMOW).
The values of δ 13 C measured in the microcrystalline siderite from Šarulje deposit and in the "red spar" siderite from Ljaljice (Fočanska Jabuka) deposit are -7.60‰ and -3.22‰ respectively.The coarse crystallised calcite from the Dragosin potok deposit has a positive δ 13 C value (+0.19‰).The δ 18 O VPDB values are negative for all examined minerals and range from -6.5‰ to -9.90‰ (Table 4).
The data are in agreement with previously published δ 13 C and δ 18 O values for neominerals occurring in the Devonian host rock of other deposits in Bosnia.For the purpose of comparison, data published by JANJIĆ & ĐORĐEVIĆ (1985) and JURKOVIĆ et al. (1997) are listed in Table 4.

Strontium isotope ratios in the barites and the metarhyolite
The strontium isotope ratios ( 87 Sr/ 86 Sr) in the barites are listed in Table 5.The 87 Sr/ 86 Sr values in the barites of SEB are 0.710972 and 0.714170 and are very similar to those in the barites from MBSM (0.711764 and 0.712548).Such Sr ratios in the barites from both areas are more radiogenic, when compared to the values between 0.70680 and 0.70925, which characterize coeval seawater, rocks and fossils from Lower Cambrian to Upper Permian (GRADSTEIN et al., 2006).
The 87 Sr/ 86 Sr value of the metarhyolite from the Vranica Mountain in MBSM is extremely high (0.776995).
Typical Devonian barite deposits with Pb, Zn, and Fe sulphides in the Palaeozoic area of Graz (Austria) belong to the synsedimentary volcanogenic type of barite deposit and were used here as geochemical parameter to distinguish syngenetic from hydrothermal-epigenetic type of barite deposits.

REE
The low total REE concentrations, light REE enriched chondrite normalized REE patterns and negative Ce anomaly de-termined in the barites are usually interpreted as an indication of a hydrothermally infl uenced seawater fl uid component in the barite origin (GUICHARD et al., 1979;MURRAY et al., 1990).
The most signifi cant difference in the shape of REE patterns is expressed in the Eu-anomaly that is positive for barites from Dragosin Potok, Pale, Fočanska Jabuka and Kreševo area, and negative for the barites from the Šarulje, Datelji and Jabukovik deposits.This indicates the presence of two different sources of hydrothermal fl uids.
Spatially large (up to 1 km long) but poor barite ore deposits associated with siderite and Fe-, Cu-, Pb-, Zn-and Sbsulphides in the area of Šarulje, Mastilove Stijene, Kamenička River and Milotina, are especially interesting from the genetic point of view.According to KULENOVIĆ (1987), these are stratabound types of deposits.The 87 Sr/ 86 Sr ratio of barite from Šarulje (Table 5) indicates an epigenetic type of formation.The investigation will try to resolve the ambiguity based on more precious REE analyses and 87 Sr/ 86 Sr ratios in barite and host rock (Devonian dolomite).

87 Sr/ 86 Sr ratio
The Rb/Sr ratios in the investigated barites from both the, SEB and MBSM, are very low (Table 1).Accordingly, the initial 87 Sr/ 86 Sr ratios of the barites have not signifi cantly increased since the time of crystallization and refl ect the composition of the host fl uids.
The signifi cantly higher 87 Sr/ 86 Sr ratios of the barites from SEB and MBSM (0.710972 to 0.714170) relative to those of contemporaneous seawater, rocks and fossils from Lower Cambrian to Upper Permian (0.70680 and 0.70925, after GRADSTEIN et al., 2006), suggest hydrothermal fl uids and an epigenetic origin of Bosnian barites.The higher recorded 87 Sr/ 86 Sr ratios of the rocks through which hydrothermal fl uids have circulated suggest an evolved crustal source for Ba, Sr and Rb.An extremly high 87 Sr/ 86 Sr ratio of metarhyolite (0.776995) indicates a crustal source for the rhyolite magma (S-type of granitoid magma).The comparison of 87 Sr/ 86 Sr ratio in barites from SEB and MBSM and those from the Brixlegg, Graz and Rudnany deposits are shown in Fig. 7a.

SrSO 4 content in barite
The relationhips between the SrSO 4 content in barites of Bosnia and some other worldwide known barite deposits are shown in Fig. 7b.The SrSO 4 content in barites depends signifi cantly on the genetic type of barite deposit.For instance, the Palaeozoic barites from Graz (Austria) belong to the synsedimentary volcanogenic type of barite deposit and have low SrSO 4 contents (0.6 to 1.6 wt%).Devonian barites of the same genetic type in Meggen and Rammelsberg deposits, also have low SrSO 4 contents (0.23-0.59 wt%).In contrast, barites of Bosnia and also those of the Brixlegg (BX) deposit in Austria and the Rudnany (RD) deposit in Slovakia are characterized by considerably higher SrSO 4 contents (0.9 to 5.01 wt% and 0.8 to 3.2 wt%, respectively), which are typical for hydrothermal epigenetic deposits.Extended rang es of SrSO 4 contents could be the result of partial remobilization processes during the Hercynian and Alpine orogeny.
Hg-tetrahedrite also occurs in the barite deposits in SEB, but as a minor component.Its δ 34 S values are also negative (-4.95%, Fočanska Jabuka).The main ore minerals are galena, sphalerite and pyrite, and chalcopyrite is subordinate.According to KUBAT et al. (1979KUBAT et al. ( /1980) the δ 34 S values of these sulphides range from -0.5 to +4.5‰ (Table 6).Compared to these data, the δ 34 S values in barites are enriched by heavy sulphur isotope (as in the barite deposits in MBSM).
Two isotopically different types of sulphide also occur in the Rudnany deposit.The main ore minerals are Hg-tetrahedrite and chalcopyrite, which have markedly negative δ 34 S values (Fig. 10).In contrast, pyrite and cinnabar have positive δ 34 S values (CAMBELL et al., 1985).According to ŽAK et al. (1991) andGRECULA et al. (1991) negative δ 34 S values in tetrahedrite and chalcopyrite are consequences of isotope fractionation between H 2 S, (derived from deepseated fl uids) and SO 4 2-, (derived from the Permian sea water).
In Palaeozoic strata of Graz, galena, sphalerite and pyrite occur, and they exhibit relatively high positive δ 34 S values ranging from +2.5‰ to +13.2‰ (PAK et al., 1980).Data are not available for the Brixlegg deposit where Hg-tetrahedrite is the sole ore mineral and other sulphides only occur as accessory minerals δ 34 S. Analysis of tetrahedrite from Schwaz, Tyrol (obtained from Professor PROHASKA (Leoben) revealed a negative δ 34 S value (-1.60‰).
Comparison of the sulphur isotopic composition in sulphide minerals from different barite deposits in SEB, MBSM, Graz and Rudnany is shown in Figs.10a and 10b.Positive δ 34 S values in sulphides of both barite deposits from SEB (Table 6) and polymetallic sulphide deposits from MBSM (KUBAT et al., 1979(KUBAT et al., /1980)), and also positive δ 34 S values in barites from barite deposits in SEB and MBSM indicate that one of the sources of the sulphur in these deposits could be older Lower Palaeozoic stratiform volcano-sedimentary sulphide deposits.Studies of such a type of sulphide deposit were undertaken on the Lower Palaeozoic series of Gemericum in Slovakia.They revealed δ 34 S values ranging between +2‰ to +15‰ (KANTOR & RYBAY, 1970;RADVANEC et al., 1992).There are still no measurements of δ 34 S values in Lower Palaeozoic stratiform volcano-sedimentary sulphide deposits in the Dinarides.
Variscan metamorphism caused the circulation of hydrothermal fl uids that remobilized sulphur from the Lower Palaeozoic and older stratiform volcano-sedimentary sulphide deposits and led to the formation of the younger sulphide deposits.The obvious enrichment of heavy sulphur isotopes in barites compared with those in sulphides in the barite deposits of both, SEB and MBSM, indicates retrograde Variscan metamorphism and infl uence of the sulphate derived sulphur from the Permian sea.

δ 18 O VPDB, SMOW in barites and fl uid inclusions
The δ 18 O values in barites in SEB (+14.2‰ to +15.6‰) are very similar to those in the Brixlegg and Rudnany barite de-   posits (Fig. 7).Remarkably higher δ 18 O values occur in barite samples from MBSM (+15.8‰ to +22.4‰ ).According to RAMOVIĆ E. ( 1991) the only fl uid inclusion study in barite deposits in SEB was that of BLEČIĆ (1983), who discovered primary fl uid inclusions in the barite in the Pb-Zn deposit in Ranoprge (Fočanska Jabuka) and determined T h between +110ºC and +140ºC and a salinity of 10 wt% NaCl equ.
In the last 15 years, numerous fl uid inclusion studies were carried out in ore deposits (mostly barite deposits) of Palaeozoic complexes in MBSM (PALINKAŠ & JURKOVIĆ, 1994;JURKOVIĆ & PALINKAŠ, 1999;STRMIĆ et al., 2000;PALINKAŠ et al., 2001;JURKOVIĆ & PALINKAŠ, 2002;PALINKAŠ et al., 2008).The results of all these studies demonstrated higher salinity 24.2 do 26.3 wt% NaCl equ. in Kreševo and 32.6 to 32.9 wt% NaCl equ. in Raštelica.Analyses of fl uid inclusions of these authors in barites of barite deposits in MBSM revealed higher homogenisation temperatures (+210ºC to +310ºC in Kreševo area, +230ºC to 270ºC and 320º to +350ºC in the Raštelica deposit.There is a clear correlation between lower δ 18 O values and lower T h of fl uid inclusions in barite deposits from SEB relative to higher δ 18 O values and higher T h of fl uid inclusions in barite deposits from the MBSM.This is in agreement with the statement of HOEFS (1997) who stated that mineralisation fl uids of higher temperature are characterized by higher salinity and higher δ 18 O values.The process of barite mineralisation in the Brixlegg deposit took place at temperatures ranging from +70ºC to 130ºC (FRIMMEL, 1991).In Rudnany, (a vein ore deposit consisting of siderite, barite, tetrahedrite and chalcopyrite), the study of fl uid inclusions determined T h varying between +150ºC and +300ºC (RADVANEC et al., 2004).

Origin of the barium-strontium bearing hydrothermal fl uids
The 87 Sr/ 86 Sr ratios determined in the barites (0.710972 to 0.714170) from both SEB and MBSM are high.The high Ba content and high 87 Sr/ 86 Sr ratio in the mineralisation fl uid could be achieved by hydrothermal leaching of Rb-rich altered felsic rock.According to FRIMMEL & PAPESCH (1990) the high 87 Sr/ 86 Sr ratios are typical for fl uids being connected to S-type magmatism and/or being crustal contaminated by circulation through Rb-rich clastites and extrusive magmatic rocks.
Until 1969 or 1972 respectively it was believed that the carbonate sequences of Jezero (Jajce) and Vranica Mountain were of Upper Carboniferous to Lower Permian age (KATZ ER, 1926).Rhyolitic magmatism occurred in the Middle and Upper Permian and partly in the Triassic (KATZER, 1926).JURKOVIĆ & MAJER (1954) found signs of contact metamorphism at the contact between the rhyolite and these carbonate rocks on the Vranica Mountain and Sinjakovo, concluding that the rhyolite is of Upper Carboniferous to Middle Permian age.MUDRENOVIĆ et al. (1969) however, found Silurian-Devonian conodonts in limestones in the Jezero area (Jajce).Based on Devonian fossils on the Vranica Mountain, however, the age boundary of rhyolite to Middle-Upper Carboniferous-Lower Permian has been revised (ŽIVANOVIĆ, 1972).According to HRVA TOVIĆ (1996TOVIĆ ( , 2006) ) rhyolites are the product of two stage volcanic activity.Most of them are synsedimentary with metasediments of presumed Silurian age.Some hypabyssal rhyolites intruded into Late Silurian and Early Devonian limestones, which also occur as xenoliths within the volcanic bodies.HRVATOVIĆ marked the Upper Permian as the upper boundary of rhyolite age, while he observed a large quantity of quartz-porphyry pebbles in basal breccias and conglomerates of discordant Upper Permian Formation of Kruščica Mt.The basal discordant breccias, with quartz-porphyry fragments, were previously observed by JEREMIĆ (1963).Petrological studies of the rhyolites of Sinjakovo and Vranica Mt. were undertaken by JURKOVIĆ & MAJER (1954) and MAJER & GARAŠIĆ (2001).JURKOVIĆ & MAJER (1954) determined the leucogranite or albite granitic character of the rhyolite magma.MAJER & GARAŠIĆ (2001) identifi ed the peraluminous character of the rhyolite of Vranica Mountain (PI = 1.9-4.1).The low content of compatible trace elements and high contents of incompatible trace elements indicate a crustal magmatic origin.Additionally, the authors concluded that relationships between Rb, Y and Nb suggest a syncollisional origin of the rhyolite magma.
In the same sample of metarhyolite being studied by MAJER & GARAŠIĆ (2001) we determined an extremely high 87 Sr/ 86 Sr ratio (0.776995 ±2s), confi rming the hypothesis of a crustal origin of the rhyolite magma.In Slavonian S-granites (Psunj, Papuk and Krndija Mountain), LAN-PHERE & PAMIĆ (1992) discovered that the 87 Sr/ 86 Sr ratio corresponds to a value of 0.72539±17, while in the Moslavačka Mountain it is 0.74302±5.An unusual spectrum of paragenetic types of ore deposits (JURKOVIĆ, 1956) sup- ports the presence of an S-type granite in MBSM.Ore deposits of Ba and subordinately of Fe (barite, siderite, ankerite, pyrite and stibnite) dominate.All other ore deposits of Cu, Pb, Zn and As are very small and their minerals are subordinate to barite and siderite ore deposits.Metals, typical for I-type magma (Sn, W, Mo, F, B, Li) occur very rarely, only as occurrences of mineralogical importance.

Genetic model for the formation of the baritesulphide deposits in the Palaeozoic complexes of MBSM and SEB
On the basis of geological and geochemical data comprising former investigations and data determined in this study, it can be concluded that barite ore deposits in SEB and MBSM had been formed by hydrothermal fl uids,linked to magmatic and metamorphic processes and infl uenced by Permian seawater.
The following phases of hydrothermal mineralisation have been recognized in the SEB and MBSM area: a) Early Variscan phase which is not the subject of this study; b) Late Variscan phase which is responsible for the origin of barite ore deposits containing Fe-, Cu-, Zn-, Pb-and Sb-(As) sulphides with positive δ 34 S CDT values; c) Post-Variscan (Early Eoalpine) phase which affected the existing Late Variscan barite ± siderite ore deposits with mercury-bearing fl uids associated with the processes of degassing of the Upper mantle, and leading to formation of Hg-, Ag-and Au-rich tetrahedrites showing negative δ 34 S CDT values.Degassing pro cesses were linked to the early phase of the Permo-Triassic intercontinental rifting.

Late Variscan phase.
In the whole of the Dinarides, barite ore deposits were formed in the late stage of the Variscan cycle and are located in the Upper Silurian, Devonian, Carboniferous and Permian rocks.Ore mineralisation in the clastites is usually present in the form of veins or impregnations, whereas in carbonate rocks it occurs as irregular bodies or replacement nests.Barite is the dominant mineral, quartz is subordinate and siderite and calcite occur only locally.Sulphides of Fe, Cu, Zn, Pb, Sb and As occur in very variable mutual relationships, ranging from trace amounts up to 10 %, but all have positive δ 34 S values.The form of occurrence and geochemical data of the studied barite ore deposits indicate their epigenetic nature and origin, caused by circulation of hydrothermal fl uids which were related to late stage Variscan metamorphism and magmatism and infl uenced by Permian seawater.The bulk of the Late Variscan barite ore deposits were formed most likely in Lower Permian time.
Most of the barite ore deposits in MBSM experienced processes of regeneration and remobilisation in the Post-Variscan stage.Only rare barite deposits have been partly or completely preserved.The Trošnik deposit is a very good example of a preserved type of barite ore deposit, located near Fojnica in the NE part of MBSM.It occurs in a pre-Devonian complex of rocks.The paragenesis of the deposits contain pyrite and chalcopyrite as the main minerals, whereas siderite and quartz occur as gangue minerals.Sb-and Fe-rich tetrahedrite occurs too, but contains only traces of Hg and has positive δ 34 S values (+3.23‰ to +3.73‰, KUBAT et al., 1979KUBAT et al., /1980)).A very similar result (+4.0‰) was produced in the current analysis of this tetrahedrite.
Barite ore deposits in SEB, however, have been almost completely preserved in their primary state.They are small but numerous, characterized by Fe-, Cu-, Zn-, Pb-and Sbsulphides, but do not contain Au, only small amounts of Ag.A post-Variscan overprint characterized by the formation of Au-, Hg-tetrahedrite having negative δ 34 S values (-4.95‰) is only locally present (Fočanska Jabuka, Šarulje).
Geochemical differences between barite ore deposits in MBSM and SEB are summarized in Table 7. Monosulphide Hg-tetrahedrite barite ore deposits in MBSM differ from polysulphide barite ore deposits in SEB in having: a) more positive δ 18 O values in barites, b) lower δ 34 S values in barites, c) pronouncedly negative δ 34 S values in Hg-tetrahedrite, d) signifi cantly higher homogenisation temperature and higher salinity in fl uid inclusions of barites, quartzes and fl uorites.
Regarding the connection of other ore deposits in Dinarides with the Late Variscan phase, it should be emphasized that at the end of the Lower Permian, continental or shallow marine clastic sediments of the Grödener Formation were formed under a warm arid climate.These sediments are widespread in the Dinarides and are according to JURKOVIĆ & PALINKAŠ (1996) bearers of uranium (Žirovski Vrh, Slovenia), copper (Cerkno-Sava Fold, Slovenia; Vitez-Ustiprača, Monte Negro) and low manganese haematite ore deposits (Mokronog-Hrastno, Slovenia; Rude, Croatia; Bukovica, Croatia).These deposits are described by DROV-ENIK et al. (1980), ŠINKOVEC (1971), ČOP et al. (1998), and KULENOVIĆ (1987).The Middle Permian sediments grade upwards into the Upper Permian shallow marine evaporite and carbonate sediments, (the Bellerophon Formation), or locally into the Sabkha transition zone or continental red beds.An early diagenetic Sabkha type deposit is described by PALINKAŠ et al. (1993).Most of the Upper Permian evaporites occur on tectonic lines along the Una, Sana, Vrbas and Bosna rivers, and in the Mostar, Sinj, Knin and Drniš areas.Upper Permian evaporites are characterized by a mean δ 34 S value of + 11‰ (JURKOVIĆ & ŠIFTAR, 1995).
The post-Variscan/ Eoalpine phase.Strong magmatic activity (rhyolites, keratophyres, diabases) took place during the Permian period, especially in the Asslian-Sakmarian stages.PAMIĆ et al. (2004) using K-Ar method determined the age of metadiabase (287.8 ± 11.1 Ma) and ortho-greenschist (268.7 ± 10.2 Ma) at Bradine (Ivan Mt., MBSM) and connected their results to post-Variscan magmatism.Using the same method on the same rock types, the authors determined a cooling phase which lasted until the Triassic (247.0 ± 9.5 Ma; 238.4 ± 9.2 Ma).The results support the heating event during Upper Permian time in the MBSM.
Heating of some parts of the crust in the Dinarides during the Middle/Upper Permian enabled lateral (extensional) movements of the continental crust and the rise of upper mantle fl uids.The optimum geotectonic environments in the Dinarides developed along a Permo-Triassic intracontinental rift.Contemporaneously, former Late Palaeozoic faults, the western Voljevac fault and eastern Busovača fault, as well as a dense framework of faults of lower order between them, had been reactivated.The geotectonic conditions facilitated penetration of mercury (± fl uorine)-bearing fl uids from deep levels of the Upper mantle to higher levels of the crust.KA-RAMATA et al. (1995) emphasized that the highest concentration of mercury in former Yugoslavia occurred in the Triassic mineralization of the Dinarides (mercury deposits Idrija, Tršće, Spič, Draževići, Kovač Mt).Independently of this statement, JURKOVIĆ & PALINKAŠ (1996) wrote "Fluorine and mercury bounded to the Hg-tetrahedrite in the MBSM were probably derived at least partially from the uppermost zone of the mantle".On their way to upper levels fl uids passed through Upper Proterozoic and Caledonian Auand Ag-bearing ore deposits, and Hg being present in fl uids amalgamated with the Au and Ag.At still higher levels, these fl uids reached barite ore deposits being formed in the Late Variscan phase.There, most of the primary sulphides have been fl uidized, and a new mineral, Hg-tetrahedrite, rich in Au (10-50 g/t) and Ag (1000 do 3000g/t) was formed.
Results of 183 mercury-bearing minerals analysed from the ore deposits of the Dinarides suggested the conclusion that isomorphic substitution of mercury into the host miner-als decreased in the following order: sphalerite → tetrahedrite → gold/silver → pyrite → galena → realgar → antimonite (KARAMATA et al., 1995).This is in agreement with the situation in the MBSM.
Strongly negative δ 34 S values of Hg-tetrahedrite in MBSM ore deposits were explained by remobilization of isotopically light sulphur of biogenic origin from the Middle/Upper Permian stratiform U-Cu (±Fe) ore deposits in the Dinarides and/or from older similar genetic types of ore deposits.The role of isotope fractionation between ascending deep-seated H 2 S and descending SO 4 2-from Permian seawater is not excluded.

CONCLUSION
Geochemical investigations of barites revealed: (1) Trace element compositions in barites from both area (SEB and MBSM) are very similar indicating a unique ore bearing area with the infl uence of seawater on hydrothermal barite origin.
(2) Barites of both areas show elevated Sr content (0.48 to 2.83% in barites from SEB, 1.44% in barite from MBSM), typical for epigenetic hydrothermal barite ore deposits.The Sr substitues for Ba in the crystal lattice.
(3) The 87 Sr/ 86 Sr isotope ratios in the barites of both areas are similar (0.710972 and 0.714170 in barites from SEB, 0.711764 and 0.712548 in barites from MBSM) and are more radiogenic in comparison with values which characterize coeval seawater, rocks and fossils from Lower Cambrian to Upper Permian (0.70680 to 0.70925).This also indicates an epigenetic hydrothermal origin of barite ore deposits., derived from the Permian evaporites.(8) In both ore areas of Bosnia, SEB and MBSM, two paragenetic types of barite ore deposits were determined.The older type originated in the Late Variscan phase (Lower Permian) and the younger one in the Post Variscan/Early Eoalpine phase.The older type of barite ore deposit contains more than 90% barite, small amounts of quartz, locally siderite and calcite, and polysulphides (Fe-, Cu-, Pb-, Zn-and Sb(As)-sulphides), the amount of which depends on the host rock (5-10% in clastites, 1-2% in carbonate rocks).This type dominates in SEB, and very rarely shows signs of the Post-Variscan overpint.In the MBSM area, it only occurs in the Trošnik deposit and partly altered in the Jezero area (Jajce).All other barite ore deposits in MBSM (Kreševo, Kiseljak, Zec and Pogorelica Mt., Gornji Vakuf, Medenik) were overprinted during the Post-Variscan phase and have the genetic characteristics of a younger regenerated type of barite ore deposit.The younger type of barite ore deposit is characterized by monosulphide (Au-, Ag-and Hg-rich tetrahedrite).Other sulphides, mainly Cu-sulphosalts, only occur in trace amo unts.This tetrahedrite has been formed by regeneration and fl uidization of sulphides of older types of barite ore deposit with a supply of Hg, Au, Ag and F from the mantle and/ or amalgamation of Au and Ag from Caledonian and older ore deposits.The younger type of barite ore deposit occurs only sporadically in SEB (Fočanska Jabuka) and then as younger barite veins and nests with Hg tetrahedrite having negative δ 34 S (-4.95‰).

Fi gu re 4 :
Photographs of white barite occurrences: a) in Permian limestone of Datelji; b) in Carboniferous schists of Pale; c) in Devonian limestone of the Glumac deposit (Kreševo); d) in Devonian limestone of the Dubrave deposit (Kreševo).Note hammer for the scale.
C and δ 18 O VPDB values determined in neominerals of Devonian rocks hosting different barite deposits in Bosnia, have been compared with those being typical for primary Devonian dolomite, and are shown in Figs.8a and 8b.In primary Devonian dolomite the typical δ 13 C values range from +0.5‰ to +3‰ and the δ 18 O VPDB values between -3.5‰ and -7.0‰ (GRADSTEIN et al., 2006).Carbon and oxygen isotope values of all neominerals in the Devonian dolomites are shifted relative to these typical values toward lower values as clearly demonstrated in Fig. 8.This indicates a change in the isotopic characteristics of Devonian host rocks during mineralization and points to the epigenetic origin of barite deposits.The isotopic data of carbon and oxygen of previous investigators, (presented in Table 4), also suggests the same conclusion.The comparison of δ 13 C and δ 18 O SMOW ratio in siderites from SEB and MBSM and those from the Brixlegg, Graz and Rudnany deposits are shown in Figs.9a and 9b.Fi gu re 7: Comparison of 87 Sr/ 86 Sr ratio, SrSO 4 %, δ 34 S and δ 18 O values in barites from SEB and MBSM and those from Brixlegg (BX), Graz (GZ) and Rudnany deposits (RD): a) besides 87 Sr/ 86 Sr ratio in barites, typical values of 87 Sr/ 86 Sr ratio in Devonian dolomite (D) and in strontianite (SrCO 3 ) and in celestine (SrSO 4 ) of Rudnany deposit are shown too; b) the SrSO 4 content in barites; c) measured δ 34 S values in barites where HT = hydrothermal barite; S = sedimentary barite, VS = volcanogenic-sedimentary barite; d) measured δ 18 O values in barite.Fi gu re 8: Comparison of δ 13 C (a) and δ 18 O VPDB (b) values of neominerals in Devonian rocks hosting diff erent barite deposits in Bosnia and those being typical for primary Devonian dolomite.

Fi gu re 9 :
Comparison of δ 13 C (a) and δ 18 O SMOW (b) values in siderites from SEB and MBSM and those from the Brixlegg, Graz and Rudnany deposits where CP = Typical Carboniferous-Permian values.
The early phase of intracontinental rifting: Controversial opinions exist concerning the beginning of the Alpine cycle.CASSINIS et al. (1975)  and WOPFNER (1984) considered that the hiatus between the Lower and Middle Permian sedimentary cycles separates the Variscan cycle from the overlying Alpine cycle.KRAINER (1993) considers the rifting processes during the Middle Triassic as indicating the beginning of the Alpine cycle.The contemporaneous nature of the early phase of the intracontinental rifting and the beginning of the Alpine cycle in the Dinarides is emphasised here, because the Permian/ Triassic boundary (251 Ma) has a well documented suite of

( 4 )
Very high 87 Sr/ 86 Sr isotope ratio (0.776995) determined in a rhyolite sample from Vranica Mt. (MBSM) confi rms the origin of rhyolite magma by crustal anatexis.(5)The δ 13 C and δ 18 O values in calcite, dolomite and siderite of barite ore deposits are shifted toward lower values relative to typical values occurring in Devonian host rock, also indicating an epigenetic origin of barite ore deposits.(6) The δ 18 O values in barites in SEB (+14.2‰ to +15.6‰) are remarkably lower than δ 18 O values of barite samples from the MBSM (+15.8‰ to +22.4‰).This can be explained by a lower temperature and lower salinity of mineralisation fl uids in barite ore deposits of SEB (HOEFS, 1997).

( 7 )
The barite ore deposits of SEB are characterized by δ 34 S values which are positive (+11.6‰ to +17.7‰) and enriched in heavy sulphur isotope in barites in comparison with sulphides (-0.41 to +4.26‰), and negative in tetrahedrite(-4.95‰).This indicates three different sulphur sources for barite ore deposits in SEB.The same is true for δ 34 S values in barite ore deposits of MBSM (+10.1 to +16.8‰ in barites, -9.86 to -0.71‰ in pyrites, -5.50 to -15.40‰ in tetrahedrites).The source of heavy sulphur isotope in Fe, Cu, Zn, Pb, Sb sulphides and in barites is deep seated, linked to Caledonian, Neoproterozoic and Early Palaeozoic sulphide deposits.The δ 34 S values of barites of the Late Variscan deposits have been infl uenced by Permian sea-water sulphate.This infl uence was stronger in the barites of the post-Variscan phase.In contrast the very light sulphur isotope in Hg-tetrahedrites is probably of biogenic origin and/or a consequence of isotope fractionation between H 2 S derived from deeper seated upper mantle fl uids and SO 4 2-

Table 1 :
Trace element contents of barites from SEB and MBSM.

Table 2 :
Content of Sr and SrSO 4 in barite.

Table 4 :
Isotopic composition of carbon and oxygen in the neominerals from SEB and their comparation with already published analyses of the same type in SEB and MBSM.

Table 5 :
Strontium isotope analyses in the barites from SEB and MBSM and metarhyolite.

Table 7 :
Summarized geochemical data from barite ore deposits in SEB and MBSM.scale global shifts to higher δ 18 O values in carbonates indicate a general progressive change from the Late Permian through the Triassic and are interpreted as the result of cooler sea water or a glacial episode suggesting a total cooling of 4°C in tropical seas(WALLMAN, 2001).