Palinkas.indd 93 � AB STRA CT Samoborska Gora Mts. is situated within the westernmost part of the Zagorje–Mid–Transdanubian zone of the Inter- nal Dinarides. The Samoborska Gora Mts. predominantly consists of Permian unmetamorphosed siliciclastic sedi- ments and evaporites, overlain by Lower Triassic sediments. Rude mineralisation is hosted by Permian siliciclastic sediments, below gypsum and anhydrite strata. The central part of the deposit consists of a 1.5 km long stratabound mineralisation, grading laterally into ferruginous sandstone and protruding vertically into a gypsum–anhydrite layer. Siderite–polysulphide–barite–quartz veins are located below the stratabound mineralisation. The stratiform part of the deposit is situated above the stratabound and consists of haematite layer with barite concretions and veinlets. Late stage galena–barite veins overprint earlier types of mineralisation. The Rude ore deposit was generated by predominantly NaCl ± CaCl2–H2O solutions. Detrital quartz from stratiform mineralisation contains fl uid inclusions with salinities between 7 and 11 wt. % NaCl equ., homogenizing between 150 °C to 230 °C. Stratabound/siderite–polysulphide–barite–quartz vein type mineralisation was derived from solutions with salinities between 5 and 19 wt. % NaCl equ., homogenizing between 60 °C and 160 °C, while late stage galena– barite veins were precipitated from solutions with salinities between 11 and 16 wt. % NaCl equ., homogenizing be- tween 100 °C to 140 °C. Fluid inclusion bulk leachate chemistry recorded Na+>Mg2+>K+>Ca2+>Li+ and Cl–>SO4 2– ions. Sulphur isotope composition of barites and overlying gypsum stems from Permian seawater sulphate, supported by increased Br– content, which follows successively the seawater evaporation line. The sulphur isotopic composition of sulphides varies between –0.2 and +12.5 ‰, as a result of thermal reduction of Permian marine sulphate. Ore–forming fl uids were produced by hydrothermal convective cells (refl ux brine model), and were derived primarily from Permi- an seawater, modifi ed by evaporation and interaction with Permian sedimentary rocks. Rude deposits in Samoborska Gora Mts. may be declared as a prototype of the Permian siderite–polysulphide–barite deposits (products of rifting along the passive Gondwana margin), in the Inner Dinarides, and their equivalents extending northeastward into the Zagorje–Mid–Transdanubian Zone and the Gemerides, and southeastward to the Hellenide–Albanides. Keywords: Rude siderite–polysulphide–barite–haematite deposit, Early intracontinental rifting, SEDEX, Feeder zone, Evaporites, Shock quartz, Planar deformation feature, PDFs, Zagorje–Mid–Transdanubian zone, Internal Dinarides Permian–polysulphide-siderite–barite– haematite deposit Rude in Samoborska Gora Mts., Zagorje–Mid–Transdanubian zone of the Internal Dinarides � Ladislav A. Palinkaš1, Sibila Borojević Šoštarić1, Sabina Strmić Palinkaš1, Walter Prochaska2, Jorge Spangenberg3, Stela Cuna4 and †Boris Šinkovec5 1 Faculty of Science, University of Zagreb, Horvatovac 95, HR-10000 Zagreb, Croatia; (lpalinkas@geol.pmf.hr; phone: +385-1-465-971; fax: +385-1-4605-988) 2 Institut für Geowissenschaften, Montanuniversität, Peter-Tunner-Strasse 5, A–8700 Leoben, Austria 3 Institute of Mineralogy and Geochemistry, University of Lausanne, BFSH–2, CH-1015 Lausanne, Switzerland 4 National Institute for Research and Development of Isotopic and Molecular Technologies, 65–103 Donath, RO-400293 Cluj-Napoca, Romania 5 Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb, Croatia doi: 104154/gc.2010.06 Geologia Croatica 63/1 93–115 30 Figs. 4 Tabs. Zagreb 2010 Geologia CroaticaGeologia Croatica Geologia Croatica 63/1Geologia Croatica 94 nica Mts. can be grouped into four main units. Autochthon: 1) Tectonized ophiolite mélange, including all lithological members, from sediments, to basic and ultrabasic igneous components, 2) Palaeozoic–Triassic magmatic–sedimentary complex overprinted by Early Cretaceous metamorphism, 3) Late Cretaceous–Palaeocene fl ysch, and Allochthon: 4) Triassic and younger sequences belonging mainly to carbon- ate platform facies (ŠIKIĆ et al., 1978; 1979; BASCH, 1981; ŠIKIĆ, 1995). The Autochthon of Samoborska Gora Mts. consists only of: 1) Palaeozoic unit, composed of Late Carboniferous dark gray schists, shales and sandstones. Shallowing of the sedi- mentary basin evolved into a dry-land phase, followed by deposition of fi ne to coarse–grained sandstones, interlayered with conglomerates, dolostones and evaporites (HERAK, 1956). These deposits are unconformably overlain by an Early Triassic clastic–carbonate unit, followed by Middle and Late Triassic carbonate–marl sediments, with occasional appearances of cherts; 2) Cretaceous mélange is predomi- nantly composed of basalts and diabases within shal es, gray- wackes, conglomerates, radiolarites and limestones of dif- ferent Mesozoic ages, covered by Neogene sediments. The volcanics, often as basalt–spilite pillow lavas, might be prod- ucts of a Triassic rifting stage, and Allochthon: 3) is repre- sented by Mesozoic carbonate platform lithotypes. The basic difference in geology of the Samoborska Gora Mts. in relation to Medvednica Mts. geology is the absence of the Palaeozoic–Triassic magmatic–sedimentary complex overprinted by Early Cretaceous metamorphism in the form- er, and the presence of ultrabasic members in the ophiolitic mélange of the latter (ŠIKIĆ et al., 1979; TOMLJENOVIĆ, 2000). The common feature is the presence of siderite–poly- sulphide–barite–quartz deposits, at Rude (Samoborska Gora Mts.) and Bistra (Medvednica Mts.) within the Permian non– metamorphosed clastics. The deposits are confi ned to Early intracontinental rifting in the northwestern sector of Neo- Tethys and were emplaced along the passive continental mar- gin of Gondwana (PALINKAŠ, 1990; PALINKAŠ et al., 2008). 3. MINERALISATION The Rude siderite–polysulphide–barite–haematite ore de- posit is located within the valley of Gradna creek, in the vil- lage of Rude, 25 km west of Zagreb. The mineralisation is hosted by Permian siliciclastic sediments, overlain by gyp- sum and anhydrite deposits (Fig. 2), and consists of three epithermal ore types (low to intermediate temperature): 1) siderite–polysulphide–barite–quartz veins (Fig. 3A), 2) stra- tabound siderite–pyrite–barite–quartz ore beds (Fig. 3B), 3) and late stage barite–galena–quartz veins (Fig. 3C), and two stratiform ore types, 4) stratiform haematite–barite–quartz beds (Fig. 3D), and 5) gypsum and anhydrite layers (Fig. 3E). 1) Siderite–polysulphide–barite–quartz veins are below the stratabound siderite-barite-quartz ore bodies on the east- ern side of the Gradna valley (Fig. 2) The sulphide veins cut the Palaeozoic sandstones (Fig. 3A). The veins are most 1. INTRODUCTION The study focuses on the genesis of siderite–polysulphide– barite–haematite mineralisation of Rude, Samoborska Gora Mts., supported by geological observation, fl uid chemistry, and isotope composition of sulphides and sulphates. Siderite –polysulphide–barite–quartz deposits (SPBQ) of the Samo- borska Gora, Trgovska Gora, and Petrova Gora Mts. are re- markably comparable in geology, mineralogy, geochemistry of fl uids and nature of metal sources. SPBQ deposits can be well correlated with similar SPBQ deposits hosted within non–metamorphosed units of the Internal Dinarides. These include Ljubija (NW Bosnia), those in the Zagorje–Mid– Transdanubian zone, Rudabanya (northernmost Hungary, Lower Triassic), siderite–magnesite deposits in the Gemeri- des (Rudnyani, Nižna Slana, Jelšava and others), and sider- ite deposits in the Eastern Alps (PROCHASKA & HENJES- KUNST, 2007; RADVANEC et al., 2004; PALINKAŠ et al., 2008; STRMIĆ PALINKAŠ et al., 2009). The SPBQ deposits of the Samoborska Gora, Trgovska Gora and Petrova Gora Mts. were described by JURKOVIĆ (1958, 1959, 1960, 1961, 1962); JURKOVIĆ & DURN (1988) and ŠINKOVEC (1971). The deposits have a variable appearance, epigenetic veins, stratabound and stratiform characteristics. Replacement ore is present where the Carboniferous carbonates are the host rocks (Trgovska Gora Mts. and Ljubija deposit). According to PALIN KAŠ (1985, 1988, 1990); PALINKAŠ et al. (2003, 2008); BOROJEVIĆ ŠOŠTARIĆ (2004); BOROJEVIĆ ŠOŠ- TARIĆ et al. (2009), these deposits were formed by sub-ter- restrial hydrothermal convective cells (sensu HARDIE, 1990), or the refl ux brine model (sensu LEACH et al., 2005), along the passive continental margin, during the Permian Early in- tracontinental rifting. Sulphur isotopes point to the dominant contribution of the Permian evaporitic sea water, as an ore– forming fl uid, modifi ed by interaction with the host rocks. It rules out a Carboniferous distal volcano–exhalative geneti- cal model (JURKOVIĆ, 1988), and linkage with the Alpine type stratabound epigenetic Pb–Zn sulphide deposits, (e.g. Mežica–Bleiberg types in the Alps), as argued for by lead isotopes (KÖPPEL, 1983; PALINKAŠ, 1985). They also dif- fer remarkably in sulphate isotope composition from the Middle Triassic Dinaridic deposits, as do their prominent representatives at Vareš (SEDEX) and Idrija (epigenetic hy- drothermal and SEDEX), (PALINKAŠ, 1985, 1988, 1990; PALINKAŠ et al., 2003, 2008). 2. GEOLOGICAL SETTING The Samoborska Gora and Medvednica Mts. represents the westernmost part of the Zagorje Mid–Transdanubian zone (ZMTZ), (sensu PAMIĆ & TOMLJENOVIĆ, 1998; TOM- LJE NOVIĆ, 2002) or the Sava Composite unit (sensu HAAS et al., 2000; Figs. 1A, B). Units in the ZMTZ show Alpine and Dinaridic characteristics, including elements of both the External and Internal Dinarides. The ZMTZ is fl anked be- tween two prominent fault zones, the Periadriatic–Balaton and the Zagreb–Zemplin lineament systems. The mountains are composed of Palaeozoic, Mesozoic–Palaeogene and Neo- gene formations. Tectonostratigraphic units of the Medved- Palinkaš et al.: Permian–polysulphide-siderite–barite–haematite deposit Rude in Samoborska Gora Mts... Geologia Croatica 95 In the Kokel and Sv. Trojstvo corridors, a massive sider- ite bed together with ferruginous sandstones, represents the stratabound ore, formed by infi ltration of hydrothermal so- lutions through the footwall sandstones, and partly through the overlying evaporite beds (Figs. 2 and 4). Mineralisation consists predominantly of coarse–grained siderite and quartz aggregates, and minor pyrite, mica and rutile. Siderite min- eralisation is underlain by iron–rich sandstones intercalated with 5–20 cm thick layers of clays, marl clays, cherts and siderite. The upper part of the siderite body is represented by iron rich and iron poor gray sandstones with clay inter- calations. Quartz pervasively replaces siderite in these ores (Fig. 3B). Widespread silicifi cation, and irregular veining, and in places the anastomosing appearance of quartz aggre- gates, suggests a hydrothermal origin, as evidenced by fl uid inclusion studies (presented in the forthcoming paragraph) rather than diagenetic recrystallization of silica. commonly cms to dms in thickness, but they can reach up to 3 m in some places (ŠINKOVEC, 1971). Veins predate, are contemporaneous with, and postdate formation of the strat- iform–stratabound mineralisation. The vertical extent of the vein–type mineralisation is not more than 40 to 50 m. Quartz and pyrite, are severely fractured, crushed and brecciated in the veins. However, aggregates of marcasite, pyrite and chalcopyrite, in contrast, show little ductile de- formation, due to compensation of the strain by the softer parts of the parageneses. The major vein mineral is siderite, which precipitated earlier than quartz, sulphides and barite. 2) The stratabound siderite–pyrite–barite–quartz ore consists of an iron ore layer extending more than 1.5 km in the NE–SW direction. The central part of the deposit is com- posed of a yellow–brownish siderite ore body, 180 m long, 80 m wide and up to 8 m thick (average 3–4 m) which dips 25–35° toward the NW (Fig. 2; ŠINKOVEC, 1971). Fi gu re 1: Overview of the major tectonic units of the Zagorje Mid–Transdanubian zone, with geological sketch map of Samoborska Gora Mts. and the loca- tion of the Rude mineralisation (PAMIĆ & TOM LJE- NOVIĆ, 1998; TOMLJENOVIĆ, 2002). A B Geologia Croatica 63/1Geologia Croatica 96 Fi gu re 2: Simplifi ed cross–section through the Rude ore deposit. The principle ore types are: siderite–polysulphide (Cu, Pb, Zn)–barite–quartz veins (des- ignated on the fi gure as Cu–Fe ore veins), stratabound siderite–barite–quartz beds (on the fi gure as siderite), stratiform haematite–barite beds (on the fi gure haematite), and gypsum and anhydrite beds (on the fi gure as evaporites). Old mining corridors were drawn as trapezoidal openings. The cross– section is in realistic scale based on the mining maps (ŠINKOVEC, 1971). Fi gu re 3: Structure of the principal ore types: A) Con- tent of the vein mineralisation: siderite (Sd)–chal- copyrite (Cpy)–pyrite (Py)–barite (Brt)–quartz (Qtz); B) Stratabound massive siderite (Sd) with irregular patches of quartz (Qtz); C) Successive growth of ga- lena (Gn) and barite (Brt) in the late stage veins; D) Stratiform beds of haematite (Hm) with detrital, heavily fractured quartz (Qtz); E) Gypsum (Gp) with highly contorted bends, coloured with iron and manganese oxy–hydroxides (Hm). A B C D E Palinkaš et al.: Permian–polysulphide-siderite–barite–haematite deposit Rude in Samoborska Gora Mts... Geologia Croatica 97 A change to more oxidizing condition can be deciphered by the presence of barite (Fig. 4) at sites 6, 10, 11, and 12. Pyrite is highly cataclased (Fig. 6; site 10). The massive siderite ore layer laterally grades into the ferruginous sand- stone. The siderite cement of the sandstone is gradually con- verted to a haematitic one, by a process synchronous with mineral precipitation. It is evidenced by the intimate inter- growth of quartz grains and haematitic cement, as well as the absence of traces of box-work or any other supergenic texture, even on a microscopic scale (sites 9 and 13). In con- trast to simultaneous precipitation, elsewhere, siderite ore underwent oxidation and attained a micro–brecciated struc- ture. The exposed siderite sandstones are oxidized by super- genic conditions and quartz grains are coated by colloform goethite, forming garlands, with a cockade ore texture, while a box–work texture developed in the oxidized massive sider- ite (Figs. 18, 19, 20). 3) Late stage, low-intermediate temperature, galena–bar- ite veins consisting predominantly of galena, barite and mi- nor sphalerite and quartz, cut Upper Palaeozoic sandstones These are the youngest veins in the Rude ore deposit, and thus they overprint earlier types of mineralisation (Fig. 3C). Maximum thickness is 20–30 cm, and the veins usually end in a network of horstail veinlets. 4) The stratiform haematite–barite–quartz ore (Fig. 3D) consists of small lenticular ore bodies, 5 to 30 m in length, and 1 to 4 m thick. Vertically and laterally this kind of ore passes gradually into ferruginous sandstones with 8 to 30 wt. % iron content. The old mining site and outcrops of the haematite–barite–quartz ore are exposed at the Klassenbruch locality, at the upper riverhead of the Gradna stream. The stratiform haematite–barite–quartz ore has a ho- mogenous structure (Fig. 3D). The major ore mineral is hae- matite. In places, barite veinlets, no longer than 4 mm, and barite concretions, mm-cm in size, accompany the major mineral. Quartz is ubiquitous, and sometimes rhythmically alternates with haematite. Haematite conglomerates, with rounded and angular quartz clasts, are matrix– and clast– supported (from a micro– to cm– scale). The origin of quartz is ambiguous, either chemogenic or detrital (Figs. 3D, 21, 22). The problem of detrital quartz in the stratiform ore type was questioned and indicated in the original paper of ŠIN- KOVEC (1971). Detrital quartz is marked by a mosaic suture along the grain boundaries (Figs. 21, 22). The shape and sharp contours of the grains, attest little or no transport. Quartz agglomera- tions, show conical organization of grains, resembling shat- tered cones. The quartz grains are severely frac tured, radially or across the grain boundaries. Jigsaw-fi t structures are com- mon (Fig. 21). The deformation features, no wider than 0.1–1 μm, cut across the grains as planar or bent lamellae, closely spaced, following crystallographic planes, usually decorated by fl uid and/or mineral inclusions as a result of annealing and healing (FRENCH, 1998). Plastic deformations are eas- ily observed in the form of undulatory extinction on rotation of the stage of the polarizing microscope, which follows the same inclusion-bearing tracks visible in plane polarized light (Fig. 22). They are referred to as possible shock metamorphic phe- nomena, induced by meteorite impact at the P/T boundary (KIEFFER, 1971; KIEFFER et al., 1976; GRIEVE et al., 1996; FRENCH, 1998). There are two possibilities for how quartz entered the ore and sedimentary environment of evaporation. One is be- ing washed into the basin from an already impacted paleore- lief, or introduced as an instantaneous impact load into the soft, iron rich mud (the future stratiform ore). Filling of fi ne jigsaw-fi t fractures with haematitic cement, suggests the lat- ter mechanism. More detailed elaboration requires further Fi gu re 4: Sketch map of the Sv. Trojstvo and Kokel pits with old mining works (ŠINKOVEC, Mining report, 1954). The numbers and spots mark the sites examined by microscopy. Stratabound siderite–barite–polysulphide ore, below a gypsum layer, con- sists of massive yellow–brownish siderite, with pyrite, intensively silicifi ed and partly oxidized (sites, 1., 2., 3., 4., 5., 7.). The reducing conditions during precipitation gradually changed to more oxidizing, evidenced by the pres- ence of barite (sites, 6., 10., 11. and 12.). Stratabound ore in the form of fer- ruginous quartz sandstones, with siderite cement, partly hematized, mi- crobrecciated, is the lateral extension of the siderite layer. Siderite–sulphide veins intersect or cross the siderite layer. Geologia Croatica 63/1Geologia Croatica 98 research efforts, and the Rude deposits may be an interesting object for the international audience regarding P/T bound ary phenomena. 5) The gypsum and anhydrite layers, heavily contorted with red–green–gray–white bands are part of the ore series and are present in the hanging wall of the ore body together with dark dolomite, chert and fi ne and coarse grained silici- clastics (ŠINKOVEC, 1971, Fig. 3E). The sulphur isotope values suggest their Permian age mimicking the secular var- iation of the standard Permian sea water. A wide scatter of δ34S values in some gypsum specimens, however, indicates a signifi cant contribution of an extraneous source of sulphate ions (ŠIFTAR, 1989), as does a high content of lead. 4. MATERIALS AND METHODS OF STUDY The samples for ore petrography were prepared by a stan- dard procedure. Cut ore samples were embedded into plastic rings 2–4 cm in diameter, greased, ground (using 120, 240, 400, 600, 800, 1200 mesh quartz powders) and polished (us- ing 6, 3, 1 and 1/2 μm diamond and aluminium powders). A Zeiss Axioplan microscope equipped with a digital camera at Etvös Lorand University, Budapest was used to determine ore minerals, paragenetic successions and distinct textures. Microthermometric measurements were performed on 0.3–0.5 mm thick wafers of quartz on a Leitz–Wetzlar mi- croscope with objectives P25/0.50 for freezing and UM 32/0.30 for heating runs by a Chaixmeca cooling and heat- ing stage, operating between –180 and +600 °C. A Linkam THMS 600 stage was mounted on the Olympus BX 51 mi- croscope using 10x and 50x Olympus long–working distance objective lenses for visible light. Two synthetic fl uid inclu- sion standards (SYN FLINC; pure H2O, mixed H2O–CO2), were used to calibrate the equipment. The precision of the system was ±2.0 °C for the homogenisation temperature, and ±0.2 °C in the temperature range between –60 and +10 °C. Primary fl uid inclusions were determined on the base of their petrography, according to procedure described by ROED- DER (1984) and SHEPERD et al. (1985). Fluid inclusions were measured in: i) quartz associated with stratabound siderite–pyrite–barite–quartz mineralisa- tion; ii) detrital quartz associated with stratiform mineralisa- tion; and iii) barite associated with late stage galena–barite vein mineralisation. The salinity was calculated from ice and hydrohalite melting temperatures using the FLUIDS compu- ter program developed by BAKKER (2003), and according to the procedure described by NADEN (1996). Isochores were calculated using the computer program ISOC (BAKKER, 2003), from the equation of state by ZHANG & FRANTZ (1987), and corrected for the volumetric properties of quartz. The bulk ion compositions of trapped fl uids were ana- lysed by ion chromatography at Montanuniversität Leoben by the technique modifi ed after BOTTRELL et al. (1988). A Dionex DX–500 system was used for analyses of halogens. Cations were analyzed in the aliquots of the same solution using standard atomic absorption spectrometry. The bulk crush–leachate analysis was performed on: i) quartz, haem- atite and barite associated with stratiform mineralisation; ii) quartz and siderite associated with stratabound mineralisa- tion; and iii) barite and galena associated with late stage ga- lena–barite vein mineralisation. The sulphur isotope compositions of sulphide (n=9) and barite (n=2) samples were determined at the Institute of Min- eralogy and Geochemistry at the University of Lausanne us- ing the Carlo Erba 1108 elemental analyzer (EA), connected to the Thermo Fischer Scientifi c Thermoquest/Finnigan Mat Delta S IRMS (EA/IRMS). Barite and gypsum samples were collected from i) stratiform mineralisation. Pyrite, chalcopy- rite, sphalerite, galena and barite were sampled from ii) siderite –polysulphide–barite–quartz vein mineralisation, and galena and barite from iii) late stage galena–barite vein mine ralisa- tion. The isotope values are reported relative to the Vienna– Fi gu re 5: Ore petrography with photomicrographs: A) Coarse grained euhedral siderite I (Sd I), with patches of pyrite II (Py II), accompanied by coge- netic quartz II (Qtz II) and followed by idiomorphic to hypidiomorphic marcasite (Mrc) and fi ne grained subhedral siderite II (Sd II). Plain polarized light; B) Polars crossed. The photo shows marcasite (Mrc) with expressive anisotropic eff ects and pyrite II. Because the rate of direct nucleation of FeS2 is insignifi cant in slightly acidic solutions below 300 °C, most of the pyrites and marcasites in hydrothermal ores form via the conversion of an FeS precur- sor. Marcasite can form in excess of 300°C and it can persist on a geological time scale only below 160°C. It has repercussion on the assessment of meta- morphic grade of the autochtonous Palaeozoic–Mesozoic formation of Samoborska Gora Mts., which has not been registered yet. 5A 5B Palinkaš et al.: Permian–polysulphide-siderite–barite–haematite deposit Rude in Samoborska Gora Mts... Geologia Croatica 99 Canyon Diablo troilite standard (V–CDT). The reproducibil- ity, assessed by replicate analyses of the laboratory standard (pyrite, working value = +6.1 ‰; synthetic mercury sul- phide, working value = +15.5 ‰; barium sulphate, working value = +12.5 ‰ δ34S) was better than 0.2 ‰. Additional sulphur isotope compositions of sulphide (n=4) and barite (n=2) were determined at the National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj–Napoca, Romania. Major, trace elements and REE in one sample of gypsum from stratiform mineralisation are determined by XRF and ICP-MS at the Bundesanstalt für Geowissenschaften und Rohstoffe in Hannover. 5. PETROGRAPHY Microscopy of the hydrothermal ore samples from the stra- tabound and vein type mineralisations determined the fol- lowing primary minerals: siderite, quartz, pyrite, marcasite, greigite (melnikovite), chalcopyrite, sphalerite, galena, tet- rahedrite, linnaeite, barite and chlorite. Secondary minerals are: bornite, chalcocite, covellite, cuprite, and goethite (ŠIN- KOVEC, 1971). There are two generations of siderite. Siderite I (Sd I) is a coarse grained and forms euhedral to subhedral crystals (Figs. 5A, 6, 7), often with annealing effects, with an approximate 120° interfacial angle. Sd I is the major constituent of the vein and stratabound minerali- sation, growing simultaneously with quartz I (Qtz I) and py- rite I (Py I) which is often cataclased (Fig. 6). Siderite II (Sd II) is fi ne grained, usually euhedral and is associated with marcasite (Mrc) and pyrite II (Py II) (Figs. 5A, B). As the rate of direct nucleation of FeS2 is insignifi - cant in slightly acidic solutions below 300°C, most of pyrite and marcasite in hydrothermal ores form via conversion of an FeS precursor (SCHOONEN & BARNES, 1991). The pyrite to marcasite ratio from the sulphidation reactions is strongly dependent on pH. Marcasite is the predominant pro- duct below pH 5 at 25°C, whereas pyrite is dominant in neu- t ral and alkaline solutions (MUROWCHICK & BARNES, 1986). The same trend is observed at higher temperatures. However, although marcasite can form at temperatures in excess of 300°C, it can only persist on a geological time scale below 160°C (RISING, 1973). It has previously unrecog- nized repercussions for assessment of the metamorphic grade of the autochthonous Palaeozoic–Mesozoic formation of the Samoborska Gora Mts. Quartz, beside siderite, is the most abundant mineral in the vein–type mineralisation. There are three generations of quartz: Quartz I (Qtz I) is cogenetic with siderite I (Fig. 6). Quartz II (Qtz II) pervasively infi lls the fractures in siderite I, coprecipitating with pyrite II. (Figs. 3, 9A, B). Quartz III (Qtz III) is a product of widespread silicifi ca- tion and coexists with all other sulphide minerals and barite (Figs. 11A, B). Fi gu re 6: Coarse euhedral grains of siderite I (Sd I), quartz I (Qtz I), and py- rite I (Py I). The pyrite is highly cataclased. Plain polarised light. Fi gu re 7: Coarse subhedral grains of siderite I (Sd I), with cogenetic euhe- dral pyrite I (Py I), and later chalcopyrite (Cpy) within inter–granular space. Plain polarised light. Fi gu re 8: A veinlet of cataclased and idiomorphic pyrite II (Py II), embed- ded in the quartz II (Qtz II). The silicifi ed siderite host was pervasively penet- rated by copper rich solutions. Chalcopyrite (Cpy) resorbed pyrite, produc- ing corroded, granular and rounded interfaces. The pyrite faces, embedded in the quartz stayed perfectly unaff ected by advancing replacement. Plain polarised light. 6 7 8 Geologia Croatica 63/1Geologia Croatica 100 Fi gu re 9: A) Growth zoning; Unobstructed zonal growth of pyrite I (Py I) was gradually retarded by the simultaneous precipitation of quartz II (Qtz II), which converted growth of pyrite into sectorial growth. Plain polarised light; B) The sectorial texture allowed easy penetration of the copper rich solu- tion, through a sieve-like assemblage of quartz and pyrite, and replacement of pyrite grains by chalcopyrite. Replacement of pyrite proceeded by galena (upper right corner). Plain polarised light. Fi gu re 10: A) Cataclastic pyrite II (Py II), and marcasite (Mrc) minutely disintegrated, and cemented with interstitial quartz II (Qtz), underwent massive re- placement by chalcopyrite (Cpy). Predominantly brittle cataclasis of pyrite and marcasite grains, gradually changed to ductile deformation observed at the right corner of the photo. Plain polarised light; B) Advanced stage of pyrite replacement by chalcopyrite. The quartz II (Qtz II) and pyrite II (Py II) re- main as relics of the former veinlet. Pyrite severely cataclasted with crystal faces entirely rounded. Plain polarised light. Fi gu re 11: A) Crustifi cation texture. Siderite host crosscut by a symmetrical, crustifi ed veinlet showing successive inward precipitation of minerals, from the open fi ssure walls: siderite II (Sd II) – quartz III (Qtz III) – pyrite II (Py II) – sphalerite (Sph) – barite (Brt). Central part of the veinlet is fi lled with barite. Plain polarised light; B) The same microphoto. Crossed polars. 11A 11B 10A 10B 9A 9B Palinkaš et al.: Permian–polysulphide-siderite–barite–haematite deposit Rude in Samoborska Gora Mts... Geologia Croatica 101 Marcasite; a fi ne grained aggregates of marcasite usu- ally follows pyrite II, and mark a slight change in the pH of the hydrothermal fl uid (Figs. 5A, B). Greigite (melnikovite) forms colloform spherulites, in places with garland texture (Figs. 12A, B) and represents a late stage phase, however, predating galena and barite. Be- low 300°C pyrite and marcasite form via an FeS precursor (SCHOONEN & BARNES, 1991). Chalcopyrite (Cpy) rarely develops idiomorphically, but regularly replaces pyrite and marcasite or just infi lls the frac- tured grains (Figs. 7, 10, 13). Sphalerite (Sph) is rare and is associated with barite (Brt) and galena (Gn) (Figs. 11A, B). Tetrahedrite (Tet) post–dates and replaces pyrite, like- wise chalcopyrite. It occurs before galena but has not been observed as having been replaced by it (Fig. 14). Galena (Gn) is the youngest member of the paragenesis. It replaces pyrite and chalcopyrite effi ciently (Figs. 12A, 13, 15), or infi lls intergranular spaces in the siderite–quartz host, forming a disseminated style of mineralisation (Figs.16, 17). Linnaeite (Ln) is mostly euhedral, regularly embedded in chalcopyrite or occurs as individual grains (Fig. 16). Barite (Brt) is the youngest mineral phase in the veins, infi lling inter–granular spaces induced by fractures (Figs. 11A, B). In the area of Klassenbruch, at the end of the Gradna valley, it forms 10 to 20 cm thick barite–galena (±pyrite, quartz) veins cutting the host sandstones. Fi gu re 12: A) Greigite or melnikovite (Grg) forms colloform globular textures, with spheruloids and garlands consisting of radial aggregates. It growths over diff erent nucleation seed cores, usually quartz II (Qtz II). Galena (Gn) post–date greigite and partly or completely replaces it. Plain polarised light; B) Detailed image of the greigite globular texture. The zonal texture consists of bends, with random, radial or crustifi ed arrangement of aggregate elements. In the cent- er is a quartz grain, serving as a nucleation site. The greigite probably developed over a FeS precursor, gradually converting to pyrite at the outer rims of the globule. The globule is dissected by a galena veinlet, with clear sign of resorption of iron sulphide, and partially infi lled by galena. Plain polarised light. Figure 13: The host, coarse grained siderite (Sd I), experienced several suc- cessive replacement events: fi rst silicifi cation and pyritization (Qtz II, Py II), then copper metasomatism, and resorbption of pyrite grains, while the galena (Gn) stage is the last one. The cleavage pits in galena are post–dep- ositional features. Plain polarised light. Figure 14: A hypidiomorphic grain of tetrahedrite (Tet) resorbed a pyrite (Py II) grain. The next precipitating phase was galena which penetrated the siderite host, but did not aff ect the trahedrite grain boundary. Plain polar- ised light. 12A 12B 13 14 Geologia Croatica 63/1Geologia Croatica 102 6. RESULTS 6.1. Fluid inclusion study 1) Quartz associated with stratabound mineralisation contains the following fl uid inclusion types with different degree of fi lling (PALINKAŠ et al., 2003; BOROJEVIĆ ŠOŠTARIĆ, 2004): i) primary, liquid–rich inclusions, occasionally con- taining anisotropic daughter mineral, predominates greatly (L+V±SA), ii) pseudosecondary, metastable, liquid rich inclusions, so- metimes with anisotropic daughter mineral (L±V±SA). Since the vapor bubble develops after cooling runs, the meta-stability might be induced by ice extension. iii) rare vapor rich inclusions (V+L±SA), (Figs. 23E, F). Inclusions are spherical and irregular in shape, and range in size between 5 and 20 µm. During freezing, the following melting sequence was observed (in the presence of a vapour Figure 15: Atoll texture; Resorption of euhedral pyrite by galena in quartz veinlet. The host is siderite I (Sd I). At the bottom of the atoll–Pyrite a tiny grain of pyrite is almost completely replaced. Plain polarised light. Figure 16: Corona texture; Idiomorphic crystals of pyrite (Py II) and lin- naeite (Ln) in the quartz (Qtz II) veinlet, are hosted between walls of coarse crystalline siderite I (Sd I). At the bottom of the large galena grain (Gn) a linnaeite grain (Ln) is replaced by a shapeless aggregate. An idiomorphic crystal of linnaeite, however, persisted to keep a euhedral shape, but a re- juvenated galena veinlet, cut the linnaeite grain diagonally along the former veinlet path, and embraced the linnaeite crystal, forming a corona– like galena rim. Plain polarised light. Figure 17: Siderite I (Sd I) host experienced pervasive silicifi cation and py- ritization (Py II). Galena (Gn) precipitated next, infi lling inter–granular spac- es and producing disseminated galena mineralisation. Curved cleavage pits have developed as a result of post–precipitation deformation. Galena replaces all former sulphides. Pyrite II highly corroded. Plain polarised light. Figure 18, 19: Ferruginous sandstone with siderite cement, oxidized to goethite (Gt), which forms colloform rims around quartz grains (Qtz) in the form of garlands making cockade textures. Plain polarised light. 15 17 16 18 19 Palinkaš et al.: Permian–polysulphide-siderite–barite–haematite deposit Rude in Samoborska Gora Mts... Geologia Croatica 103 phase), I + Hy + A → I + Hy + A +Le → I + Hy + L → I +L →L, where I = Ice, Hy = hydrohalite, A = antarcticite, Le = eutectic liquid and L = Liquid. First melting (Te) in a predominant number of liquid– vapour inclusions was observed between –65 °C and –45 °C, indicating the presence of divalent cations in inclusion liq- uids (Ca2+, Mg2+; CRAWFORD, 1981; DAVIS et al., 1990). Hydrohalite melting (Tm hyd), was observed at temperatures between –50.0 °C to –23.5 °C. Ice melting temperatures (Tm ice) are from –15.5 °C to –3.2 °C. Homogenisation to a liquid phase (Th) occurred at temperatures between 56 °C and 158 °C. Higher homogenisation temperatures, between 263 °C and 286 °C, were observed only in two inclusions Bulk composition was calculated by the melting tem- perature of ice and hydrohalite. Salinity of fl uid inclusions varies between 0.3 to 7.5 mass % NaCl + 4.3 to 14.5 mass % CaCl2, with a mass ratio of NaCl/(NaCl+CaCl2) ranging from 0.07 to 0.76, and the total salinity ranges from 5.3 to 19.2 wt. % NaCl equ. Several vapour rich inclusions showed high salinity (17.9 to 18.9 wt. % NaCl equ.) and very high homogenisa- tion temperatures (between 352 °C to 449 °C) to the vapour state (Figs. 24A, C, D). The inclusion behaviour is inter- preted as a result of leakage. 2) The following fl uid inclusion types were found in barite associated with late stage galena–barite vein mineralisation: i) primary, metastable liquid rich inclusions (L±V), ii) pseudo-secondary liquid inclusions (L). Inclusions with very small sizes (1–3 µm), occurring in clusters within healed fractures, are interpreted as pseudo- secondary (ROEDDER, 1984, Figs. 23G, H, I). The last melting of ice was registered at temperatures from –12.2 °C to –7.8 °C. The homogenisation to liquid occurs at tempera- tures between 102 °C and 140 °C. The total salinity of fl uid inclusions was estimated to be between 11.5 and 16.2 wt. % NaCl equ. (Table 1, Figs. 24B, C). 3) Fluid inclusions in detrital quartz associated with stra- tiform type of mineralisation Detrital quartz intergrown with haematite was separated from haematite–barite–quartz samples (Fig. 3 d) from the sedimentary part of the Rude deposit and the following types of fl uid inclusion were observed in them: i) secondary, metastable liquid rich inclusions (L±V), ii) secondary liquid inclusion (L), (Figs. 21, 22, 23A, B, C, D). Microthermometric measurements were performed only on inclusions that nucleated vapour bubble after cooling runs. Due to the very small size of the inclusions (1–4 µm), during cryometric measurements, only the last melting of ice (Tm ice) was registered at temperatures from –7.5 °C to –1.1 °C (Table 1). The homogenisation to liquid (Th) occurred at temperatures between 150 and 231 °C. The total salinity of fl uid inclusions is between 7.2 and 11.1 wt.% NaCl equ. (Ta- ble 1; Figs. 24B, C). High temperature of homogenisation (Th), with salini- ties between 7.2 and 11.1 wt. % NaCl equ. would suggest an Figure 20: Box–work texture of goethite (Gt) developed after oxidation of massive siderite cement. Plain polarised light. Figure 21: Detrital quartz in the stratiform haematite beds, has developed mosaic suture joints. Planar deformation features (PDFs) cross the grain boundaries. Jigsaw–fi t feature on the central grain postdate the PDFs. Plain polarised light. Figure 22: PDFs in detrital quartz are decorated by solid and fl uid inclu- sions visible under high magnifi cation only. 20 21 22 Geologia Croatica 63/1Geologia Croatica 104 Table 1: Microthermometric data grouped according to the inclusion types in quartz from stratabound siderite-barite-quartz mineralisation, detrital quartz associated with stratiform mineralisation, and in barite from the late stage galena–barite veins. Quartz, stratabound/vein type ore FI type F Te (oC) Tm hyd (oC) Tm ice (oC) Th (oC) s (wt.%NaCl equ.) ρ (g/cm3) Molality wt.% NaCl wt.% CaCl2 NaCl/NaCl+CaCl2 L+V 0.95 –65.0 –50.2 –10.1 122.5 14.1 1.040 2.807 1.0 13.8 0.07 L+V 0.90 –40.8 –12.5 115.0 16.5 1.060 3.388 2.0 14.0 0.13 L+V 0.90 –49.0 –44.0 –11.1 112.0 15.1 1.056 3.053 1.5 14.5 0.09 L+V 0.95 –48.8 –45.3 –10.8 132.5 14.8 1.038 2.980 1.3 13.8 0.08 L+V 0.95 –27.4 –7.4 263.5 0.878 2.112 5.5 5.8 0.49 L+V 0.95 –26.8 –9.6 158.0 13.6 1.017 2.682 7.5 6.0 0.56 L+V 0.98 –6.8 132.8 10.2 1.006 1.952 L+V 0.90 –6.1 286.0 0.833 1.762 L+V 0.95 –6.1 9.3 L+V 0.98 –27.0 –6.0 9.2 5.3 4.3 0.55 L+V 0.98 –27.0 –5.7 8.8 5.0 4.3 0.54 L+V 0.98 –27.0 –5.7 8.8 5.0 4.3 0.54 L+V 0.95 –48.0 –6.2 124.0 9.5 1.007 1.789 0.5 9.8 0.05 L+V 0.98 –5.8 114.4 8.9 1.011 1.680 L+V 0.98 –3.8 109.0 6.1 0.996 1.120 L+V 0.98 –3.2 137.4 5.3 0.969 0.947 L+V 0.98 111.8 L+V 0.98 –45.0 –34.0 –5.0 112.4 7.9 1.005 1.458 2.0 6.8 0.23 L+V 0.95 –62.2 –38.0 –5.7 139.0 8.8 0.991 1.653 1.0 8.8 0.10 L+V 0.95 –61.0 –36.2 –5.2 137.5 8.1 0.998 1.514 1.0 8.0 0.11 L+V 0.95 –60.7 –38.5 –5.2 126.5 8.1 0.997 1.514 0.8 8.8 0.08 L+V 0.98 –62.5 –49.1 –11.2 114.1 15.2 1.054 3.078 0.8 15.0 0.05 L+V 0.95 –62.5 –33.5 –6.9 10.4 2.5 8.0 0.24 L+V 0.98 –58.1 –38.0 –4.4 112.0 7.0 1.000 1.290 0.8 6.3 0.11 L+V 0.98 –57.6 –38.5 –4.4 110.3 7.0 1.001 1.290 0.3 6.3 0.04 L+V 0.95 –66.5 –4.7 7.4 L+V 0.95 –47.5 –23.5 –6.2 9.5 7.3 2.3 0.76 L+V 0.85 –52.0 –27.1 –6.3 9.6 5.3 4.5 0.54 L+V 0.98 –53.0 –31.3 –13.1 107.4 17.1 1.073 3.528 5.5 4.5 0.55 L+V 0.95 –55.5 –29.6 –15.5 19.2 4.0 14.3 0.22 L+V 0.98 –36.2 –5.2 120.4 8.1 1.000 1.514 1.8 7.3 0.19 L+V 0.98 –58.8 –38.5 –5.2 121.8 0.8 8.8 0.08 L+V 0.95 148.8 L+V 0.95 122.0 L+V+SA 0.98 125.6 L+V+SA 0.95 –58.7 –38.5 –4.8 7.6 0.8 7.5 0.09 V+L 0.15 –46.2 –31.5 –14.8 18.6 0.842 3.914 5.8 12.0 0.32 V+L 0.15 –32.0 –14.0 17.9 0.697 3.734 5.3 12.3 0.30 V+L 0.25 –31.5 –15.0 18.8 0.821 3.959 6.0 12.5 0.32 L±V 0.98 –56.0 –33.2 –8.5 78.3 12.3 1.059 2.401 3.5 9.0 0.28 L±V 0.98 –45.0 –34.0 –5.1 97.0 8.0 1.016 1.486 2.0 7.0 0.22 L±V 0.98 –62.2 –36.2 –5.1 56.0 8.0 1.040 1.486 1.8 7.5 0.19 L±V 0.95 –9.7 96.0 13.7 L±V 0.95 –9.4 94.0 13.3 L±V 0.98 –51.2 –30.1 –4.5 83.6 7.2 1.019 1.318 2.3 4.0 0.36 L±V 0.98 –54.5 –32.4 –9.2 81.0 13.1 1.064 2.580 L±V –28.8 –6.1 97.0 9.4 1.025 1.762 L±V –28.8 –5.2 86.0 8.1 1.024 1.514 L±V –55.0 –30.6 –5.5 90.0 8.5 1.024 1.597 L±V –55.0 –29.8 –5.1 102.0 8.0 1.013 1.486 Palinkaš et al.: Permian–polysulphide-siderite–barite–haematite deposit Rude in Samoborska Gora Mts... Geologia Croatica 105 unrealistic pressure of fl uids originating in a shallow depo- sitional environment. It suggests another origin of fl uid in- clusions, as well as their resemblance to PDFs. 6.2. Bulk crush–leach analysis The bulk crush-leach analysis was undertaken on the fl uid inclusions in anticipation that the primary inclusions were the predominant group, as attested to by fl uid inclusion (FI), microscopy. Detrital quartz in the stratiform ore, however, contains mostly secondary FIs, following the deformation features, not wider than 0.1–1μm, cross-cutting the grains as planar or bent lamellae. 1) Samples associated with stratabound/vein sulphide mineralisation Data obtained in quartz and siderite from the vein type siderite–polysulphide–barite–quartz mineralisation show dominant Na+ and Mg2+ cations, followed by K+ and Ca2+. The dominant anion is Cl– (Table 2). The data confi rmed the presence of divalent Mg2+ and Ca2+ cations within fl uids, pre- dicted by cryometry. The mass balance shows an excess of cations (Q+/Q– from 2.4 to 8.2), similar to the samples from the stratiform part of the deposit. 2) Samples associated with late stage galena–barite veins Barite and galena were analyzed from the late stage ga- lena–barite vein mineralisation. The dominant cations are Na+ and Mg2+, while the dominant anion is chlorine within barite, and sulphate within galena. The mass balance (Q+/Q–) ranges from 0.8 to 1.4 (Na+>Mg2+>K+>Ca2+>Li+, Table 2). Late stage barite–galena veins were precipitated from mod- erate salinity–low temperature fl uids (salinity between 11.5 and 16.2 wt. % NaCl equ., Th between 102 °C and 140 °C). 3) Samples associated with stratiform mineralisation The bulk crush–leach analysis was performed on detri- tal quartz, haematite and barite associated with the haematite mineralisation. Calculated ion ratios reveal the presence of predominantly Na–Mg–Ca–K chloride solutions. The amount of SO4 2– is increased in haematite samples (ratio Cl–/SO4 2–, from 0.1 to 0.4). Leachate of the haematite samples confi rms a Mg–K–Ca–Na sulphate rich solution. The mass balance (Q+/Q–) ranges from 1.0 to 7.1. Several samples show an ex- cess of cations (up to 9.6), attributed to a possible high CO3 2– and/or HCO3 – concentration within bulk fl uids (due to the onset of siderite precipitation), which were not measured during the procedure (Table 2). 6.3. Sulphur isotopes 1) Siderite–polysulphide–barite–quartz veins Fifteen sulphide samples from the siderite–polysulphide– barite–quartz veins were analyzed. Their isotopic composi- tions range between –0.2 and +12.5 ‰ V–CDT. Pyrite varies between –0.2 and +11.1 ‰, chalcopyrite between –0.2 and +1.2 ‰, galena between +1.7 and +7.3 ‰ and sphalerite from +11.3 to +12.5 ‰. Values increased from chalcopyrite towards galena and sphalerite (Fig. 26, Table 3). 2) Stratiform mineralisation The δ34S values of sulphates (gypsum and barite) in the stratiform mineralisation span between +3.2 and +13.6 ‰ V–CDT (Fig. 26). 3) Late stage galena–barite vein type mineralisation Two pairs of barite and galena samples were analyzed from the late stage galena–barite vein type mineralisation. Isotopic values vary from +1.7 to +4.6 ‰ for galena and be- tween +5.8 and +8.7 ‰ for barite samples (Fig. 26). Quartz, stratiform ore FI type F Te (oC) Tm hyd (oC) Tm ice (oC) Th (oC) s (wt.%NaCl equ.) ρ (g/cm3) Molality wt.% NaCl wt.% CaCl2 NaCl/NaCl+CaCl2 L±V 0.98 73.0 L±V 0.95 –7.5 191.0 11.1 2.135 L±V 0.98 155.0 9.2 L±V 0.98 –1.1 155.0 9.2 0.959 0.333 L±V 0.98 150.0 9.2 L±V 0.98 –6.1 9.3 1.762 L±V 0.95 –4.5 231.0 7.2 0.890 1.318 Barite, late Brt–Gn veins FI TYPE F Te (oC) Tm hyd (oC) Tm ice (oC) Th (oC) s (wt.%NaCl equ.) ρ (g/cm3) Molality wt.% NaCl wt.% CaCl2 NaCl/NaCl+CaCl2 L±V 0.98 –12.2 102.0 16.2 1.059 3.316 L±V 0.98 –10.3 122.0 14.3 1.029 2.856 L±V 0.98 –7.8 108.0 11.5 1.018 2.216 L±V 0.98 –9.0 138.0 12.9 1.008 2.529 L±V 0.98 –9.0 128.0 12.9 1.015 2.529 L±V 0.98 –10.0 140.0 14.0 1.015 2.782 L±V 0.98 –9.0 117.0 12.9 1.022 2.529 Table 1: continued Geologia Croatica 63/1Geologia Croatica 106 Figure 23: A, B, C, D, E, F, G) Photomicrographs of fl uid inclusion (FIs) in: 23A, B) Quartz associated with stratiform haem- atite mineralisation. High temperature of homo- genisation and salinities indicate an unrealistic pressure of fl uids originating in a shallow depo- sitional environment. It suggests another origin of fl uid inclusions, as well as their resemblance to PDFs. 23C, D) Quartz associated with stratabound si- de rite–barite–quartz mineralisation; shows trails of secondary, liquid rich FIs. 23E, F, G) Quartz associated with late stage ga- lena–barite veins with trails of pseudo-second- ary, liquid rich FIs, in addition to the primary, liq- uid rich FIs. A B C D E F G Palinkaš et al.: Permian–polysulphide-siderite–barite–haematite deposit Rude in Samoborska Gora Mts... Geologia Croatica 107 Figure 24: Chemical and microthermometric data of studied fl uid inclusions: A) Temperature of eutecticum (Te), melting of hydrohalite (Tm hyd), melting of ice (Tm ice) in FIs of quartz from stratabound ore; B) Temperature of melting of ice (Tm ice) in quartz from the late stage galena–barite veins, and detrital quartz from the stratiform mineralisation; C) Salinity vs. temperature of homogenisation (Th) in quartz from stratabound ore, detrital quartz (PDFs) in stra- tiform mineralisation, and barite in late stage galena–barite veins; D) Three component diagram H2O–NaCl–CaCl2 of melting of the last solid phase (ice). Table 2: Bulk crush–leachate data of siderite, barite, haematite and quartz from stratiform, stratabound and late stage galena–barite veins from Rude. Sample No. Mineral Location Li+ (µmol/l) Na+ (µmol/l) K+ (µmol/l) Mg2+ (µmol/l) Ca2+ (µmol/l) Cl– (µmol/l) I– (µmol/l) Br– (µmol/l) SO4 2– (µmol/l) Q+/ Q– K+/ Na+ (Br–/Cl–) *1000 SO4 2–/ Cl– S3/B Quartz Stratiform ore 0.12 113.92 14.71 96.32 6.72 83.36 1.90 0.30 15.93 2.85 0.13 3.65 0.19 S6/B Quartz Stratiform ore 0.18 102.99 14.71 94.09 402.49 88.33 1.68 0.44 12.31 9.66 0.14 5.03 0.14 S5/A Barite Stratiform ore 0.29 176.51 14.46 92.08 96.01 169.42 0.68 0.47 177.90 1.08 0.08 2.78 1.05 S7/B Barite Stratiform ore 0.33 110.48 11.06 93.07 26.49 111.08 1.97 0.57 55.07 1.61 0.10 5.13 0.50 S6/A Haematite Stratiform ore 0.41 44.73 123.81 82.29 1.95 21.11 3.55 71.02 2.02 2.77 3.36 S5/B Haematite Stratiform ore 0.91 41.86 71.97 110.43 470.20 26.96 2.87 74.76 7.11 1.72 2.77 S7/A Haematite Stratiform ore 0.80 23.36 60.06 99.98 28.45 7.96 2.36 74.62 2.14 2.57 9.38 S3/A Haematite Stratiform ore 0.33 51.06 62.95 82.29 24.68 22.32 2.58 52.79 2.52 1.23 2.37 S9/B Quartz Stratabound/ vein type ore 0.54 83.46 34.84 91.92 1.95 118.19 1.33 0.39 3.07 2.43 0.42 3.30 0.03 77a Quartz Stratabound/ vein type ore 0.24 74.03 24.07 90.63 1.29 82.68 1.71 0.32 6.17 2.91 0.33 3.85 0.07 S9/A Siderite Stratabound/ vein type ore 0.37 117.76 16.86 364.84 30.33 112.29 1.79 0.37 21.06 5.91 0.14 3.32 0.19 S10 Siderite Stratabound/ vein type ore 0.35 113.42 11.17 414.60 145.41 119.86 2.75 0.51 14.06 8.23 0.10 4.29 0.12 S8/B Barite Late Ba-Gn veins 0.37 214.88 13.54 91.46 5.46 193.75 1.39 0.49 56.09 1.37 0.06 2.52 0.29 S8/A Galena Late Ba-Gn veins 0.47 71.11 18.55 195.11 15.19 40.06 4.33 278.07 0.85 0.26 6.94 A B C D Geologia Croatica 63/1Geologia Croatica 108 6.4. Geochemistry of a selected gypsum sample Major elements (XRF, %), trace elements (ICP-MS, ppm) and REE (ICP-MS, ppm) of the selected gypsum sample from the stratiform mineralisation are presented in Table 4. 7. DISCUSSION Fluid inclusion data indicate differences in precipitation con- ditions for the stratiform and stratabound/ vein types of min- eralisation (Fig. 24C). The vein/stratabound mineralisation precipitated from fl uids with highly variable salinities (between 5.3 to 19.2 wt. % NaCl equ.), and homogenisation temperatures between 56 °C and 158 °C (Fig. 24C). Late stage barite–galena veins precipitated from moder- ate salinity–low temperature fl uids (salinity between 11.5 and 16.2 wt. % NaCl equ., and Th between 102 °C and 140 °C. All measured salinities are increased relative to seawa- ter, and the predominant portion of salinities corresponds to the composition of seawater that passed the gypsum and an- hydrite precipitation point (Figs. 24C, 25A, B). At some point, meteoric water entered into the system, causing dilu- tion down to 5.3 wt. % NaCl equ. The intrusion of meteoric water is a plausible explana- tion for coexistence between low salinity and a high Br–/Cl– ratio. Fresh water with low concentrations of Br– and Cl– would have not affected their ratio but would have decreased the salinity. The chemistry of the late stage galena-barite vein changed to become more sodic in comparison to the strati- form ore which shows an expressive calcic character. The bromine/chlorine concentration ratio in quartz and barite leachates corresponds to 6.5–10.5 % of recent seawa- ter evaporation. Some part of the samples follow a seawater evaporation trend (SET) to a high percentage of seawater evaporation (Figs. 25A, B). The Br/Cl ratios demonstrate clustering of data between 15 and 35 % of seawater evapo- ration, but the high excursion of K/Na ratios, exceeding 2 to 3 times the evaporitic concentration, is probably due to hy- drothermal water/rock interactions (McCAFFREY et al., 1987). Ore forming fl uids underwent different degrees of evaporation, whereas a maximum degree of 35 % (accord- ing to Br/Cl ratios) indicates that brines locally passed the halite saturation point. These is in disagreement with the ob- Figure 25: Composition of fl uids obtained from bulk crush/leachate ionic chromatography on barite, and detrital quartz from stratiform mineralisation, siderite and quartz from stratabound mineralisation and late stage galena–barite veins from Rude: a) K/Na vs. Br/Cl; b) K/Na vs. SO4/Cl. Evaporation trend of sea water after McCAFFERY et al., 1987; composition of Permian seawater after HORITA et al., 1991. Table 3: Sulphur isotope values (δ34S, ‰) of sulphides and sulphates. Sample No. Mineralisation type Mineral δ34S (‰) Reference SG 1 gypsum strata gypsum 13.4 Šiftar, 1989 SG 2 gypsum strata gypsum 13.6 Šiftar, 1989 SG 3 gypsum strata gypsum 13.4 Šiftar, 1989 SG 4 gypsum strata gypsum 10.8 Šiftar, 1989 SG 5 gypsum strata gypsum 11.8 Šiftar, 1989 SG 6 gypsum strata gypsum 10.5 Šiftar, 1989 SG 7 gypsum strata gypsum 6.7 Šiftar, 1989 SG 8 gypsum strata gypsum 3.2 Šiftar, 1989 SG 9 gypsum strata gypsum 7.2 Šiftar, 1989 SG 10 gypsum strata gypsum 6.2 Šiftar, 1989 SG 11 gypsum strata gypsum 3.6 Šiftar, 1989 SG 12 gypsum strata gypsum 8.4 Šiftar, 1989 SG 13 gypsum strata gypsum 9.6 Šiftar, 1989 SG 18 gypsum strata gypsum 11.1 This study SG 14 stratiform (haematite) gypsum 7.1 Šiftar, 1989 SG 100 stratiform (haematite) barite 6.0 This study SG 15 stratabound/vein type* barite 11.6 Šiftar, 1989 SG 16 stratabound/vein type* galena 3.0 Šiftar, 1989 SG 104 stratabound/vein type* galena 7.3 This study SG 306-1 stratabound/vein type* pyrite 1.2 This study SG 304-1 stratabound/vein type* pyrite 1.1 This study SG 105 stratabound/vein type* pyrite –0.2 This study SG 301-2 stratabound/vein type* pyrite 9.9 This study SG 303-2 stratabound/vein type* pyrite 11.1 This study SG 304-2 stratabound/vein type* chalcopyrite 0.6 This study SG 306-2 stratabound/vein type* chalcopyrite 1.2 This study SG 17 stratabound/vein type* chalcopyrite 0.6 Šiftar, 1989 SG 103 stratabound/vein type* chalcopyrite –0.2 This study SG 303-1 stratabound/vein type* sphalerite 12.5 This study SG 305-1 stratabound/vein type* sphalerite 11.3 This study SG 102 late Brt-Gn veins barite 5.8 This study SG 302-2 late Brt-Gn veins barite 8.7 This study SG101 late Brt-Gn veins galena 1.7 This study SG 302-1 late Brt-Gn veins galena 4.6 This study * quartz-polymetallic-siderite Palinkaš et al.: Permian–polysulphide-siderite–barite–haematite deposit Rude in Samoborska Gora Mts... Geologia Croatica 109 served fl uid salinities (max. 20 wt. % NaCl equ.; e.g. under- saturated solution) and the existence of gypsum–anhydrite strata precipitated at 3.8–10.6 % of seawater evaporation. Undersaturation to 20 wt. % NaCl equ. or lower values of salinity were achieved by intrusion of meteoric water, with preservation of the high Br/Cl ratio. Enrichment of sulphate (SO4 2–/Cl– ratio) is interpreted as the contribution of an extraneous source, which might have been oxidation of sulphide ions brought by hydrotherms, or from the host black shale by discharge of organically bounded sulphur or dissolution of sedimentary pyrite. Oxidation of sulphide ions is evidenced in lowering of δ34S values in evap- orites to +3 ‰. As a corollary, the dominant portion of fl uid was evapo- rated seawater, which temporarily did pass the halite pre- cipitation point, and was modifi ed by evolved hydrothermal water and intrusion of meteoric water. The result was spoil- ing of the SET line, by raising K/Na and increasing the SO4 2–/ Cl– ratio of the fl uids. Detrital quartz in the stratiform mineralisation had a puz- zling habit, not corresponding to the common sedimentary origin. The uncommon but ubiquitous jigsaw–fi t structure of the detrital quartz, as well as planar deformation features across the quartz grains, PDFs, (KIEFFER et al., 1976; Figs. 21; 22), provide evidence of two distinctive episodes during formation of the stratiform ore. The fi rst one, responsible for the trails of liquid and solid inclusions across the chert ag- gregates, is a shock phenomenon (PDFs, high Th, 150–231 °C, and higher Cl– concentration; Figs. 21, 22, 24C). The second is sedimentation of massive haematite ore accompa- nied by barite, documented by their higher sulphate content (ion chromatography data, Table 2), and incorporation of de- trital quartz. According to ŠIFTAR (1989), the δ34S values of overly- ing gypsum from Samoborska Gora Mts. are between +3.2 and +13.6 ‰ (Fig. 26, Table 3). Most of the values (between +9 and +11 ‰) fall within the range of Permian marine sul- phates (CLAYPOOL et al., 1980). Lower values, between +3 and +7 ‰, are controlled by oxidation of the ascending ore forming fl uids, rich in sulphide species. Increased values (up to +13.5 ‰) are interpreted as representing deposition of gypsum from the ascending sulphate already modifi ed by the thermochemical reduction of seawater which produced isotopic light sulphides and fractionated sulphates, heavier than those of the Permian evaporitic water. These data overlaps with the δ34S value of sulphates in the barite from the stratiform mineralisation (+6.0 ‰), indi- cating the strong infl uence of the Permian seawater sulphate, slightly modifi ed by sulphate formed by oxidation of hydro- thermal sulphide. Isotopic composition of sulphides from the vein miner- alisation varies between –0.2 and +12.5 ‰ (Fig. 26). A gen- eral trend of increasing isotopic values toward the late stage of mineralisation is observed (chalcopyrite < galena < spha- lerite). Maximum values of sulphide overlap with the values within overlying gypsum strata, proposing progressive ther- mochemical reduction, to completion, of the Permian sea- water sulphate. Sulphides did seemingly precipitate under non–equilibrium conditions. The virtual non–equilibrium be- tween sulphate and sulphide within the ore forming fl uid, and increasing trend of sulphide isotopes, is a result of suc- cessive precipitation from Malcopyrite to sphalerite, with a gradual rise in sulphide isotope composition. Pyrite shows Figure 26: Sulphur isotope data of Cu–Fe–Pb–Zn sulphides, barite and overlying gypsum in relation to Per- mian sea water sulphates, for explana- tion see text (CLAYPOOL et al., 1980). Figure 27. The composition of the sulphur source for the late galena–barite veins was determined on the δ34Sbarite/galena vs. Δ34Sbarite–galena plot. Ore form- ing fl uid from which barite and galena precipitated had δ34SΣS value of +6.2 ‰, and the ratio sulphate/sulphide RSO4/H2S = 0.5, is determined by the slope of the line δ34Sgalena vs. Δ34Sbarite–galena. Geologia Croatica 63/1Geologia Croatica 110 scatter of values in responds to precipitation from the earli- est to the latest phases, as Py I, Py II and Py III. The succes- sions are clearly observed by ore microscopy, and progres- sive replacement stages (Figs. 4 to 20, OHMOTO & RYE, 1979; OHMOTO & LASAGA, 1982). The composition of the sulphur source for the late ga- lena–barite veins was determined from the isotopic values of galena and barite plotted on the δ34Sbarite/galena vs. Δ34Sbarite– galena plot. Ore forming fl uid from which barite and galena precipitated had an δ34SΣS value of +6.2 ‰ (Fig. 27). The ra- tio sulphate;sulphide, R SO4/H2S = 0.5, was determined by the slope of the line δ34Sgalena vs. Δ34Sbarite–galena. The sample of gypsum collected at the old hameatite mining site of Klassenbruch has a value of +11.1 δ34S, which approximates to the well known negative peak on the curve of secular variation of Permian sea water. The gypsum sam- ple, on the other hand, has an unusually high lead (258 ppm), Ba (534 ppm), V (3.4 ppm), Ni (3.4), and Cr (2.1) content (Table 4), which speaks in favour of the contribution of metal rich brines, issuing intermittently into the evaporitic ponds. It was already evidenced by the existence of low sulphate isotope values in some gypsum samples (ŠIFTAR, 1989). High Pb (534 ppm) and the relatively low content of Zn (31.5 ppm) and Cu (2.1 ppm) is due to the low mobility of PbSO4, and dissipation of the other two ore metals, which are mo- bile in a Cl– and SO4 2- rich environment. Concentrations of REE are highly enriched relative to standard ocean water (SOW) by a factor 105 to 106 (MARTIN & WITHFIELD, (1983; Fig. 28). The fl at, REE diagram, normalized to SOW, supports the open marine origin of evaporating water, with little or no infl uence from potential dry land run–off (PLAYA et al., 2007). Lack of a negative Ce/Ce* anomaly and posi- tive Eu/Eu* is further evidence of hydrothermal input into the evaporitic ponds. Figure 28: REE in a gypsum sam- ple from the Klassenbruch haema- tite mining site, normalized to the standard sea water (MARTIN & WHITFIELD, 1983), and Phanero- zoic greywacke (TAYLOR & MC- LEN NAN, 1985). The sea water is also normalized to the greywacke (analyses were undertaken in the Bundesanstalt, Hannover, by V. MARCHIG). Table 4: Geochemistry of a selected gypsum sample: a) Major elements (XRF, %); b) trace elements (ICP-MS, ppm), sulphur isotope (δ34S, ‰); and c) REE (ICP-MS, ppm). a) Major elements (XRF, %) SiO2 TiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O P2O5 SO3 Cl F LOI Summ 0.55 0.022 0.33 0.12 0.01 0.26 31.73 0.1 0.06 0.02 44.59 0.004 0.258 21.7 99.76 b) Trace elements (ICP-MS, ppm), sulfur isotope (δ34S ‰) Ba Zn Pb Cu Cr Mn Ni Sr Ti V δ34S (‰) 534.0 31.5 258.0 2.1 2.7 17.4 3.4 891.0 57.7 3.4 11.1 c) REE (ICP-MS, ppm) La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 0.580 1.200 0.150 0.570 0.100 0.074 0.093 0.016 0.092 0.018 0.050 0.007 0.058 0.009 Palinkaš et al.: Permian–polysulphide-siderite–barite–haematite deposit Rude in Samoborska Gora Mts... Geologia Croatica 111 Lead isotope values obtained on galena from siderite– polysulphide–barite–quartz deposits of Samoborska Gora Mts., Trgovska Gora Mts. and Ljubija, yield coherent model ages of 275, 285 and 280 Ma respectively, by use of iso- chrones on the DOE–ZARTMAN (1979) multistage growth curves (PALINKAŠ, 1985; 1988). The Pb–isotope evolution diagram with growth curves, (broken curve, μ = 9.56; Fig. 29), represents (according to DOE & STACEY, 1974), the evolution of average crustal lead. The 207Pb/204Pb – 206Pb/204Pb values of the three deposits are marked on the plot and oc- cupy the area between Orogen, Mantle and Lower Crust. The Pb–Zn deposits in Triassic host rocks, Bleiberg–Kreuth, Raibl, Mežica, Salafossa, including Pb-Zn deposit Sv. Jakob on Medvednica, fall in the area marked by the broken line, designating the Upper Crustal reservoir (KÖPPEL, 1983; ZARTMAN & HEINES, 1988). One can distinguish two lead provinces, the Inner Dinarides with siderite–polysul- phide–barite–quartz deposits, including Rude, and a younger one with Pb–Zn deposits in carbonates like Bleiberg and Mežica, within the pre-existing Triassic carbonate platform. The lead incorporated in galena of the two distinctly differ- ent ore types, originated from the basement greywackes, rich in feldspars (bearer of the common lead) by interaction with mineralizing fl uids. The radiogenic Pb–rich source for the Upper Palaeozoic deposits, related to the rifting processes, is placed as shallow, affected by sub–terrestrial hydrother- mal cells, fl ashed by heated evaporitic sea water. In contrast, ore forming fl uids for the Triassic Pb–Zn deposits are deep seated brines, remobilized from deeper parts of the Gond- wana basement, with older but more radiogenic lead. The genetic model of the Rude ore deposit had been pro- posed by Šinkovec (1971) supported by detailed undergro- und and surface geological mapping. The model relies on the geosyncline concept, and fi eld observations, and suggests the major physical processes engaged in the ore formation. The research presented here, sheds more light on the geo- chemistry of chemical processes, introducing global tectonic elements in order to establish the model and to answer the unresolved questions regarding tectonic environment, ther- mal regime, and the source of the metal and sulphur. The Upper Permian and the P/T boundary, was a transi- tion time between the Early intracontinental and Advanced rifting stages in the formation of Neotethys, as marked by thermal doming and extensional tectonics. Dry land facies, evaporite ponds, a disturbed thermal regime in the incipient rifts, due to rifting magmatism, created favourable ore form- ing conditions for hydrothermal ore deposits (SEDEX) with a well developed feeder zone in the subterrestrial level. Hy- drothermal convective cells along the passive continental margin of Gondwana, demarcating the future opening of the Neotethys, produced numerous siderite-barite-polysulphide deposits in the Alps, Dinarides, Hellenides and Albanides. Fig. 30 depicts a genetic model with basic physico-che- mical processes, which governed the ore formation. The Rude ore deposit is a SEDEX (volcano-sedimen- tary) hydrothermal deposit with a genetically linked feeder zone below the stratiform and stratabound ore bodies. The rifting tectonic regime, comprised thermal disturbance, caus ed by wide-spread magmatic activity, and reaching paroxysm in the Middle Triassic. While the global lateral extension de- veloped deep water rift basins, and subsequent Jurassic oce- anization, the early rifting phenomena, including the Rude mineral deposit faded gradually, and their products were cov- ered by the stable Mesozoic carbonate platform compiled of mostly carbonate sediments. The convective hydrothermal cell, forced by volcanism, as dues ex machine, (wide-spread but not recorded within the deposit itself), generated ore bearing fl uids. The special chemistry of the fl uid was com- Figure 29: Lead isotope evolution diagram with growth curves according to DOE & STACEY (1974). The curve represents the evolution of the average crustal lead, with an area discriminated for the MORB basalts, Red sea sediments and modern pelagic sediments. DOE & ZARTMAN (1979) growth curves are constr- uct ed for the discrete lead reservoirs, in the Upper and Lower Crust and Mantle. Lead isotope data of Permian siderite depos- its from the Trgovska Gora Mts., Ljubija and Samoborska Gora Mts. are distinctly separate from the Middle Triassic Pb-Zn de- posits in the carbonates (Mežica, Bleiberg, Salafossa, and Sv. Ja- kob, Medvednica Mts.), between the lead growth curves of Oro- gen and Mantle (Lower Crust out of the plot). Geologia Croatica 63/1Geologia Croatica 112 posed of evaporitic brines and meteoric water which sank from the surface into the sub-terrestrial environment and in- teracted with the sedimentary host rocks. The physico-chem- ical change of surfi cial waters includes heating, alteration of redox-potential and pH, leaching of sedimentary sulphur and dispersed metals, while upgrading into the ore forming con- centration. Precipitation of ore minerals started on the way to the surface in the feeder zone, within the porous sediment below the evaporitic pond, forming stratabound ore bodies. At the same time the mineralized water issued into the pond and coprecipitated with evaporites as stratiform ore. The im- pact shock must have been an interregnum event if one ever existed in the ore forming period. 8. CONCLUSION The Rude deposit in the Samoborska gora Mts. is hosted by Permian non–metamorphosed siliciclastic sediments and eva porates, and composed of stratiform haematite–barite ore, stratabound/vein siderite–polysulphide–barite–quartz miner- alisation, and late stage galena–barite veins. Comparative study, of all types of mineralisation, provided a relevant basis for convincing genetic model. Ore forming fl uids were formed by a convective hydrothermal cell over thermal anomalies (HARDIE, 1990), caused by wide-spread rifting magmatism (not recorded within the ore deposit itself). Residual evapor- itic brines, derived primarily from the Permian seawater, were involved and modifi ed by interaction with the Late Palaeozoic sedimentary sequence (LEACH et al., 2005). The following evidence and data support the genetic model: Sulphur isotope composition of overlying gypsum in- volves Permian seawater sulphate. The sample of gypsum collected at the old haematite mining site of Klassenbruch has a value of +11.1 δ34S, what approximates to the well known negative peak on the curve of secular variation of sulphur isotopes in the Permian sea water. A wide variation of sulphate isotope values in gypsum, colored by pinkish and brownish hues, from light 3.2 to heavy 13.6 δ34S ‰, (a hang- ing-wall above the stratabound mineralisation), is explained by the introduction of extraneous sulphate by hydrothermal water into the evaporitic ponds. The light sulphate was formed by oxidation of hydrothermal sulphide ions. The heavy iso- tope ratio was generated by opposite process, reduction of sulphate, which might have been inorganic or organic in ori- gin, and fractionation between sulphide/sulphate. This data overlaps with the δ34S values of sulphates in the barite from the stratiform mineralisation, indicating the strong infl uence of the Permian seawater sulphate, slightly modifi ed by sulphate formed by oxidation of hydrothermal sulphide. The vein/stratabound mineralisation precipitated from fl uids with highly variable salinities (between 5.3 to 19.2 NaCI equ. wt. %). Homogenisation temperatures of fl uid inclusions,wich encapsulated ore forming fl uids, is between 56 °C and 158 °C. Figure 30: The fi gure depicts a genetic model with basic physico-chemical processes which governed the ore formation. The Rude ore deposit is a SEDEX (volcano-sedimentary) hydrothermal deposit with genetically linked feeder zone below the stratiform and stratabound ore bodies. The rifting tectonic regime, followed by thermal disturbance, created a subsurface convective circulation of hot brines over thermal anomalies, as dues ex machine, generated ore bearing fl uids. The fl uid chemistry was derived from that of evaporitic brines and meteoric water which sank from the surface into the sub-terrestrial environment below, and interacted with the sedimentary host rocks. Physico-chemical changes of surfi cial waters include heating, altera- tion of the redox-potential and pH, leaching of sedimentary sulphur and dispersed metals, upgrading into the ore forming concentration. Precipitation of ore minerals began on the way to the surface in the feeder zone, within the porous sediment below the evaporitic pond, forming stratabound ore bodies. The mineralized water issued into the pond and coprecipitated with evaporites as stratiform ore. Palinkaš et al.: Permian–polysulphide-siderite–barite–haematite deposit Rude in Samoborska Gora Mts... Geologia Croatica 113 Late stage barite–galena veins precipitated from moder- ate salinity–low temperature fl uid (salinity between 11.5 and 16.2 NaCl equ. wt.%), which were trapped in fl uid inclusions displaying homogenisation temperature between 102 °C and 140 °C. Ore forming fl uid, which precipitated barite and ga- lena, had an δ34SΣS value of +6.2 ‰, and the ratio sulphate/ sulphide R SO4/H2S = 0.5. Fluid inclusions bulk leachate chem- istry recorded the presence of Na+, Mg2+, K+, Ca2+, Li+ and Cl– and SO4 2– ions in the fl uids. The stratiform type of mineralisation precipitated from predominantly Na–Mg–Ca–K chloride solutions. The amount of SO4 2– is increased in haematite samples, due to fi nely dispersed barite probably (ratio SO4 2–/Cl– from 0.1 to 0.4). Leachate of the haematite samples confi rms Mg–K–Ca–Na sulphate rich solution. The uncommon but ubiquitous jigsaw–fi t structure of the detrital quartz, (mostly chert in origin), as well as planar de- formation features across the quartz grains, PDFs, (KIEFFER et al., 1976; Figs. 21; 22), provides evidence for a possible shock episode induced by meteorite impact at the P/T bound- ary, during formation of the stratiform mineralisation. Isotopic composition of sulphides from the vein miner- alisation varies between –0.2 and +12.5 ‰. The sulphur iso- topic composition is interpreted as a product of the thermo- chemical reduction of Permian marine sulphate. The general trend of increasing isotopic values toward the late stage of mineralisation is as follows: chalcopyrite < galena < sphalerite. The maximum value of sulphur isotopes in sphalerite (+12.5 ‰) overlaps with the values of the over- laying gypsum strata, proposing progressive thermochemi- cal reduction to the completion, of the Permian seawater sulphate. Lead isotope values obtained on galena from Samobor- ska Gora, Trgovska Gora and Ljubija siderite–polysulphide– barite–quartz deposits yield coherent model ages, 275, 285 and 280 Ma respectively, by using isochrones on the DOE– ZARTMAN (1979) multistage growth curves (PALINKAŠ, 1985; 1988). Siderite–polysulphide–barite–quartz deposits of Samo- borska Gora Mts., Trgovska Gora Mts. and Ljubija are remark- ably comparable in geology, mineralogy, geochemistry of fl u- ids and nature of metal sources. Siderite deposits can be easily correlated with similar siderite deposits hosted within non– metamorphosed units of the Inner Dinarides (Ljubija, NW Bosnia), and with those in the Zagorje–Mid–Transdanubian zone. These include; Rudabanya (northernmost Hungary, Low er Triassic), siderite–magnesite-polysulphide deposits in Gemerides (Rudnyani, Nižna Slana, Jelšava and others), and siderite deposits in Eastern Alps (PALINKAŠ et al., 2008; PROCHASKA & HENJES-KUNST, 2007; HURAI et al., 2002; RADVANEC et al., 2004). The Rude deposits with characteristic geotectonic setting, structural geology, chemistry of ore forming fl uids, stable and radiogenic isotope composition of mineral parageneses, rep- resents locus typicus of the Permian siderite -barite-poly sul- phide deposits in the western Tethyan realm. ACKNOWLEDGEMENT This paper is a result of a large scale study and research activity under the projects, 119-0982709-1175, 098-0982934-2742 of the Ministry of Sci- ence, Education and Sports, Republic of Croatia, and the SCOPES Proj- ect No. 7KRPJ065483.01, to whom we express our sincere gratitude. 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