08 garasic.indd Garašić and Jurković: Geochemical characteristics of diff erent iron ore types from the Southern Tomašica deposit, Ljubija, NW Bosnia 255 � AB STRA CT Pulverized limonite ore from a Pleistocene–Quaternary lake deposit and compact limonite ore from the Olistostrome member of the Javorik fl ysch formation, in the Southern Tomašica iron ore deposit, were investigated and compared with different types of siderite and ankerite, limestone and carbonate shale from the same location in order to deter- mine their possible protolith. Two limonite types display a notably distinct REE pattern, REE fractionations, Eu anomalies and other trace element and main oxide content. The REE pattern of compact limonite is characterized by relatively low light ((La/Sm)N = 2.87), heavy ((Gd/Yb)N = 0.98) and total ((La/Yb)N = 3.19) REE fractionations, a strong positive Eu anomaly (Eu/Eu* = 2.11) and weakly expressed negative Ce anomaly (Ce/Ce* = 0.82). The com- pact limonite and siderite REE patterns almost overlap suggesting a common REE source. The same is valid for their Zr/TiO2 ratios (0.040 in the compact limonite, 0.033–0.053 in the siderites). Pulverized limonite shows remarkably different REE patterns and the highest REE concentrations, (up to 6 to 13 times higher relatively to the other sam- ples). Its REE fractionation pattern ((La/Sm)N = 3.68, (Gd/Yb)N = 1.58, (La/Yb)N = 9.41, Eu/Eu* = 1.10 and Ce/Ce* = 0.81) is very similar to those in the carbonate shale, identifying it as the possible protolith of pulverized limonite. The same is valid for the Zr/TiO2 ratios (0.025 in pulverized limonite and 0.017 in carbonate shale). The REE pattern of fi ne grained ankerite ((La/Yb)N = 2.15, Eu/Eu* = 1.95, Ce/Ce* = 0.78) and its Zr/TiO2 ratio (0.030) are similar to those in siderite, and could, assuming extensive contamination of pulverized limonite, also represent its protolith. However, the REE patterns of coarse grained ankerite exhibit remarkable depletion of LREE over HREE and a strong reverse LREE pattern ((La/Yb)N =0.05–0.20, (La/Sm)N = 0.04–0.10, (Gd/Yb)N = 1.77–1.91). They have (similar to the other studied samples), a positive Eu anomaly (Eu/Eu* = 2.16–2.75) and negative Ce anomaly (Ce/Ce* = 0.32–0.83). Their Zr/TiO2 ratio (0.004–0.010) excludes coarse grained ankerite as the possible protolith of pulver- ized limonite. Keywords: compact limonite, pulverized limonite, REE pattern, siderite, ankerite, Southern Tomašica Geochemical characteristics of diff erent iron ore types from the Southern Tomašica deposit, Ljubija, NW Bosnia � Vesnica Garašić and Ivan Jurković Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb, Pierottijeva 6, HR-10000, Croatia; (vesnica.garasic@rgn.hr) doi: 104154/gc.2012.16 Geologia Croatica 65/2 255–270 21 Figs. 3 Tabs. Zagreb 2012 Geologia CroaticaGeologia Croatica 1. INTRODUCTION Southern Tomašica is one of the four opencast mines (Ada- muša, Vidrenjak, Tomašica and Omarska) in the Ljubija iron ore fi eld, situated approximately 200 km northwest of Sara- jevo, in Bosnia and Herzegovina. Southern Tomašica is a large deposit of siderite, ankerite, compact limonite and pul- verized limonite laying 18 km southeast of Prijedor. It is lo- cated on the northern side of the mountain system of Ljepo- vica (+678 m) and Mačkovac (+474 m) and bordered to the west by the Velika Gradina plateau (Fig. 1). Geologia Croatica 65/2Geologia Croatica 256 The origin and time of formation of the iron deposits in the Ljubija iron ore fi eld are matters of considerable debate. GRUBIĆ & PROTIĆ (2003) clearly distinguishes an older siderite-limonite formation and a younger ankerite-limonite formation. According to them, siderite occurring as lenses and alternating with black argillaceous schist in the siderite- limonite formation, originated as primary non-magmatic hy- drothermal marine sediment in the Lower to Middle Carbo- niferous. The fi rst evidence of the synsedimentary origin of this siderite was provided by JURKOVIĆ (1961). JURIĆ (1971) shared the same opinion. GRUBIĆ & PROTIĆ (2003) discovered fi ssures fi lled with iron and manganese minerals in Upper Flysch, Permian and Werfenian sediments of South- ern Tomašica. Therefore they concluded that ankerite replac- ing carbonate rock fragments in fl ysch and small siderite bodies, associated with the carbonate olistoliths in the Olis- tostrome Member of the Javorik fl ysch formation, was pre- cipitated from hydrothermal solutions partly associated with porphyrite volcanism in the Middle Triassic. STRMIĆ PA- LINKAŠ et al. (2009) regarded iron deposits within the Lju- bija fi eld as stratabound Fe carbonate ore bodies, hosted by marine limestones, and as siderite-sulfi de veins within Car- boniferous shales. They concluded that Fe mineralization occured through hydrothermal-metasomatic processes in the Permian, in accordance with the earlier opinions of PA LIN- KAŠ (1988, 1990), PALINKAŠ et al. (2003) and BORO JE- VIĆ ŠOŠTARIĆ (2004). Figure 1: The location of the studied area. Later in geological time, siderite and ankerite ore bod- ies were partly oxidized and hydrated to various types of li- monite ore (JURKOVIĆ, 1961; JURIĆ, 1971; GRUBIĆ & PROTIĆ, 2003). Although the mineralogy and major ele- ment chemistry of different limonite ore types from the Sou- thern Tomašica mine have been described earlier (JUR- KOVIĆ, 1961; ŠARAC, 1981), their REE patterns are still unknown. The aims of this study are to present the results of more detailed geochemical analyses for two different limonite ore types and compare them with the REE distribution patterns of ankerite, siderite, host limestone and carbonate shale, from the Olistostrome Member of the Javorik fl ysch formation, in order to establish their possible genetic relationships. 2. GEOLOGICAL SETTING The area of Southern Tomašica consists mainly of sedimen- tary rocks of Carboniferous, Permian, Werfenian and Qua- ternary age (Fig. 2), which were metamorphosed, folded and faulted during the Variscan and Alpine orogenies (Fig. 3). Carboniferous rocks belong to the Javorik fl ysch forma- tion, and the Permian rocks to the Tomašica clastite forma- tion. The most detailed stratigraphic column of this area was drawn by GRUBIĆ et al. (2000) and GRUBIĆ & PROTIĆ (2003) on the basis of fi eld work (M 1:1000) and core de- scriptions from 520 wells (Fig. 4). According to GRUBIĆ & PROTIĆ (2003) the Javorik fl ysch formation consists of six members. The oldest member is the Lower Flysch char- acterized by dark green argillaceous schists, alternating with medium-grained sandstone. It is followed by the Siderite- Limonite member which is up to 30 m thick, becoming thin- ner at the margins. This member contains massive siderite alternating with black argillaceous schist. Siderite is partly transformed to limonite. The Wild Flysch member, (<50 m thick), overlies the Siderite-Limonite member. It consists of two black argillaceous phyllite packets and one sandstone packet. It exhibits characteristic spheroidal and tube-like ol- istolithes at the decimetre-level on the surface. The Wild Flysch member is overlain by the Middle Flysch member which is about 60 m in thickness, consisting of alternations of argillaceous schist, (subfl ysch), sandstone (argillaceous eufl ysch) and sandstone (coarse fl ysch). It contains variably sized olistostrome lenses with mineralized limestone frag- ments, sandstone banks and rare microconglomeratic se- quences. The Middle Flysch member is overlain by an Olis- tostrome member, which is 800 m long and 50 to 150 m wide, consisting of fl ysch matrix in which carbonate olistolithe fragments, blocks and their mineralized parts are embedded. The Flysch groundmass of the Olistostrome member is mainly sandstone fl ysch, the lower and upper parts of which are composed of grey and dark grey medium-grained sand- stones, and black laminated siltstones, respectively. Carbon- ate fragments and blocks of the Olistostrome member in- clude black micrites, dark grey organogenic sparites (rich in fossils), dolomite limestones, dolomites, ankeritic limestone and ankerite. The occurrence of pulverized limonite, which in larger blocks represents the transition from ankerite and Garašić and Jurković: Geochemical characteristics of diff erent iron ore types from the Southern Tomašica deposit, Ljubija, NW Bosnia Geologia Croatica 257 Figure 2: Geological units of the Tomašica area (GRUBIĆ & PROTIĆ, 2003). Figure 3: Geological profi le I-I’ (Fig. 2) of Southern Tomašica (GRUBIĆ & PROTIĆ, 2003). Sampling locations are marked. dolomite limestones into fossiloferous limestones, is impor- tant. Typically, up to 3–4 m large isolated, spheroidal and irregular bodies of partly comb-textured ankerite and dolo- mite limestone, completely enclosed by pulverized limonite occur in this member. They appear in groups of several bod- ies in pulverized limonite profi les having a thickness of seve- ral tens of metres. In addition to this description of GRUBIĆ & PROTIĆ (2003), STRMIĆ PALINKAŠ et al. (2009) dis- covered in the Olistostrome member, dark massive siderite being locally weathered to porous, but compact limonite, while the present authors observed numerous dark lime- stones cut by veins of siderite, ankerite and calcite. In the Geologia Croatica 65/2Geologia Croatica 258 fl ysch groundmass of the Olistostrome member, carbonate shale occurs as a small isolated body. According to GRUBIĆ & PROTIĆ (2003), the last and the youngest member of the Javorik formation is the Upper Flysch, being located on the northern side of the opencast. It is 700 m long, 140 m wide and 70 m thick. The lower part of this member is particularly black in colour, and mostly composed of sandstone-siltstone fl ysch. The black colour comes from Mn oxides and hydrox- ides, and is more weakly expressed in the upper part, where sequences are at the centimetre scale. The Tomašica clastite formation is located on the west- ern side of the opencast mine, in the area of Velika Gradina. GRUBIĆ & PROTIĆ (2003) recognized fi ve members of this formation: a) Bobovica breccias, b) white sandstones, c) white and red sandstones, d) polygenous conglomerates and e) red sandstones and siltstones. The southern part of the Southern Tomašica opencast mine consists of marls, marl limestone, siltstones, sandstones and breccia-like intercalations of Werfenian age, which reach a thickness of around 70 m. According to JURIĆ (1967) and PODUBSKI (1969), the rocks of the Javorik formations are metamorphosed at the highest grade of the greenschists facies. During the Tertiary, after uplift of the Upper Palaeozoic complex, the oxidation processes of primary iron ore (sider- ite, ankerite and ankeritized carbonate rocks) in Ljubija had begun and limonite gossans had been formed “in situ”. Ac- cording to JURKOVIĆ (1961), gossans developed by weath- ering of siderite were compact and stable, while those de- rived from massive ankerite were more mobile. Later, due to erosion, gravity, mechanical and chemical leaching and solution, different aureoles of secondary limonite ore were developed. In the Pliocene–Quaternary period remarkable part of this limonites were further transported by rain, river or wind, and redeposited in palaeovalleys, palaeobasins and lakes, partly as detrital limonite, partly as pulverized limonite or “brand” (termed by Jurković in publications). On this oc- casion limonites became more or less contaminated. Reworked deposits of limonites and pulverized limonites in the Pliocene–Quaternary sequences of Jezero and Buvač near Omarska were described by JURIĆ (1969) and ŠARAC- VITALJIĆ (1973), and those in the Blatnjak deposit by JURIĆ (1971). The best description of reworked deposits of limonite and pulverized limonite in the area of Tomašica (Southern Tomašica, Northern Tomašica, Šiljezi, Stankovići, Dabića Brdo, Tevanovići, Bojići) was by CVIJIĆ (1986, 2001). The ore bodies are mainly characterized by lense-like or cone- like shapes, rarely irregular layers, reaching thicknesses of 10–30 m, locally up to 50 m, rarely more than this. The bor- ders of ore bodies are not sharp. 3. PREVIOUS STUDIES OF LIMONITES IN TOMAŠICA Laboratory and commercial studies by LOGOMERAC (1960) have shown that pulverized limonite is a suitable ore- grade raw material for sintering, pelletizing and bricketizing in the production of raw iron. The granulometric composi- tion of pulverized limonite was characterized by 26.8 wt.% of particles fi ner than 60 μm, 46.8 wt.% of particles ranging between 60 and 100 μm, 16.3 wt.% of particles laying be- tween 100 and 400 μm and 10.0 wt.% of particles from 400 to 1500 μm diameter. The specifi c and volume weights were 3.3 g/cm3, and 1.38 g/cm3, respectively. The LOI was equal to 8.15% and H2O– to 6.8%. The fi rst laboratory, physico-chemical and optical stud- ies of limonite samples from the Southern Tomašica ore dis- trict (Točak, Gradina, Stojančići and Klimenta localities) were performed by JURKOVIĆ (1961). The XRD analyses of pulverized limonite (brand) from Stojančići show mostly the presence of micro-cryptocrystallized goethite (70 wt.%), and some amorphous clay, having no peaks on the Debye diagram. DTA has given endothermic effects, which were strong at +200°C (goethite) and 350°C (partly amorphous limonite) and weak at temperatures from +550°C to +650°C (clay). TGA shows weight loss of 8% in the range between +100°C and +400°C (goethite-limonite), and 4 % between +550°C and +650°C (illite clay). The results of XRD, DTA and TG analyses reveal that the brand consists of a mixture Figure 4: Stratigraphic column of Southern Tomašica (GRUBIĆ & PROTIĆ, 2003). Garašić and Jurković: Geochemical characteristics of diff erent iron ore types from the Southern Tomašica deposit, Ljubija, NW Bosnia Geologia Croatica 259 of cryptocrystalline and partly amorphous goethite and al- lophanoid amorphous clay (68.25 and 8.65 wt.% respec- tively). The studied sample was prepared in Plexiglas and investigated under refl ected light microscopy (Fig. 5). Pul- verized limonite (brand) consists of pizoliths having diam- eters in the range of 30 and 300 μm, on average between 100 and 200 μm. Pizoliths are spheroidal, rarely oval and consist of an intimate mixture of cryptocrystalline goethite and amor phous or cryptocrystalline clay masses. In refl ected light they have considerably lower lustre than goethite, are isotropic, and in crossed polars show diffusely scattered brown inner refl ections. ŠARAC (1981) analyzed pulverised limonite samples, discovering a very high content of SiO2 (15.56%) and Al2O3 (3.40%) compared to compact limonite. Studies in the Boris Kidrič Institute in Ljubljana and in Firma Bayer have shown that ore deposits of pulverised li- monite in Tomašica represent a natural mineral pigment with a high content of natural chromofore (up to 80 %) which is applicable to the colour and varnish industry and in the in- dustry of anticorrosive coating and coloured building mate- rials. On the basis of these studies, a natural pigments factory was built in Tomašica using pulverised limonite raw mate- rial from the Southern Tomašica deposit and the Blatnjak deposit. Detailed petrological characteristics of compact limonite have been described by JURKOVIĆ (1961). Using XRD analyses, he identifi ed goethite as the main mineral inti- mately intergrown with illite which has sheets up to 10, and rarely up to 30 μm or more and with quartz crystals, occur- ring in bipyramidal prisms, with diameters in the range be- tween 30 and 300 μm, or in alotriomorphic masses. There are oxidized pyrite relics and minor lepidocrocite in massive goethite. Additionally, fi ne microscopic tiny veinlets of cryp- tocrystalline pyrolusite and microcrystalline pyrolusite in pores are also present in goethite. Cryptocrystalline or fi - brous psilomelane also occur replacing goethite or being transformed into pyrolusite. The manganese minerals were most likely formed as a weathering product of siderite, which contains up to 2.55 wt.% of MnO. Elemental silver was ob- served in the goethite pores. Mineral intergrowths are fre- quent and fi ne-grained, or rare and coarse-grained. 3.1. Samples and analytical methods All samples were collected within the Olistostrome member of the Javorik fl ysch formation excluding pulverized limo- nite (TBRA) which was found on an ancient mine heap at Stojančići representing relics of one Pleistocene–Quaternary lake limonite deposit. Levels of the quarry containing the Siderite-limonite member have been submerged some years ago since mining operations ceased and it was impossible to collect samples from this part of the Javorik fl ysch formation. Ten representative samples from the Southern Tomašica opencast mine and one from the Adamuša opencast mine have been studied in detail: compact limonite (TLIM) rep- resenting gossan formed in situ on siderite, pulverized li- monite or “brand” (TBRA), limestone (TVAP1), carbonate shale (TVAP2), white-gray coloured ankerite (TMIX), white coarse grained ankerite (TANK, TANMIC), dark fi ne grained ankerite (TANK1), reddish coarse grained siderite (TCOR), dark fi ne-grained siderite (TMIC) and yellow coarse grained siderite (AD-2). The sample of compact limonite (TLIM) represents a gossan formed “in situ” on siderite. It occurs in the form of black and shiny, kidney shaped concretions, and glassy nee- dles (Fig. 6). Microscopic investigations show that the con- cretions have an internal radiating structure (Fig. 7) and the main mineral is goethite. Other minerals in the paragenesis are quartz, clay minerals and muscovite. This is in accord- Figure 5: Spheroidal pizoliths consist of a mixture of cryptocrystalline goethite and amorphous or cryptocrystalline clay. White thin intergranular fi lms of crypto- to microcrystalline goethite surround the pizolites. The black area is a hole. Magnifi cation: x55 (after JURKOVIĆ, 1961). Figure 6: Black and shiny kidney shaped concretions and glassy needles in compact limonite (sample TLIM). Geologia Croatica 65/2Geologia Croatica 260 ance with the former more specifi c petrographic investigati- ons of compact limonites performed by JURKOVIĆ (1961). Pulverized limonite or “brand” (TBRA) from the Sto- jančići locality (Fig. 8) have also been studied in detail by JURKOVIĆ (1961) and therefore no new microscopic in- vestigations of this sample have been made. Common characteristics of the limestone sample (TVAP1) are veins bearing brown siderite, pale yellow an- kerite, and tiny white calcite veinlets (Fig. 9). Macroscopic and microscopic structural relationships suggest that the siderite was partly replaced by ankerite, whereas calcite rep- resents the youngest occurrence (Fig. 10). The limestone is dark gray micrite containing rare quartz grains, (up to 0.12 mm) and muscovite, (up to 0.06 mm). Only vein and veinlet free parts of the limestone were taken for chemical analysis. The studied sample of carbonate shale (TVAP2) is com- posed of clay-sized grains, and is a dark, fi ssile, and lami- nated rock (Fig. 11). Microscopic study revealed that it con- sists of clay minerals, detrital quartz, muscovite and variously sized spherical and oval-shaped calcispheres, which are char- acteristically 60 to 300 µm in diameter (Fig. 12). The sample of white-gray coloured ankerite (TMIX) shown in Figure 13 consists of an intimately associated white area of coarse grained ankerite crystals, with regular grain boundaries and a gray area of fi ne to medium grained anker- ite with black lobate grain boundaries, and interstitial places fi lled with a clayey-carbonaceous substance and quartz ag- Figure 7: Photomicrograph of the internal radiating structure of goethite concretions (N) in compact limonite (sample TLIM). Figure 8: Pulverized limonite or “brand” (sample TBRA). Figure 9: Brown siderite and pale yellow ankerite veins and tiny white cal- cite veinlets that cut the studied limestone (sample TVAP1) . Figure 10: Photomicrographs of siderite (Sd), ankerite (Ank) and calcite (Cal) veins that cut limestone (sample TVAP1). Partial breakdown of siderite along cracks results in haematite occurrence (N+). Figure 11: Dark fi ssile laminate carbonate shale (sample TVAP1). Garašić and Jurković: Geochemical characteristics of diff erent iron ore types from the Southern Tomašica deposit, Ljubija, NW Bosnia Geologia Croatica 261 gregates (Fig. 14). Relics of fi ne grained ankerite with lobate black grain boundaries have been observed within the white coarse grained ankerite. Ankerites of both, white and gray areas are characterized by undulose extinction. Due to the intimate association of the white and gray areas of this sam- ple, one chemical analysis of a mixed area was made. White coarse grained ankerite (sample TANK), occurs in the form of an irregular nest (Fig. 15) in the matrix of dark fi ne grained ankerite (sample TANK 1). White coarse grained ankerite is characterized by regular grain boundaries and grains free of inclusions. In contrast, grain boundaries of dark fi ne grained ankerite are highly irregular, and the inter- stitial space is fi lled with a clayey-carbonaceous substance containing usually small quartz grains and rarely muscovite (Fig. 16). Dark fi ne ankerite grains show locally tiny quartz inclusions. The undulose extinction is typical for both coarse and fi ne grained ankerite. Different parts of this non-homo- geneous rock sample were carefully separated from each other for chemical analysis. White coarse grained ankerite (sample TANMIC) also occurs in the form of an irregular nest, but this time in a ma- trix of reddish coarse grained siderite (sample TCOR), which Figure 12: Photomicrograph of carbonate shale consisting of clay miner- als, detrital quartz, muscovite and variously sized spherical and oval- shaped calcispheres (N+). Figure 13: Intimately associated white coarse grained area and gray fi ne to medium grained area of ankerite (sample TMIX). Figure 14: Photomicrograph of the fi ne to medium part of an ankerite sample TMIX with quartz aggregates fi lling interstitial places between an- kerite grains having lobate grain boundaries (N+). Figure 15: White coarse grained ankerite (sample TANK) occurs in form of an irregular nest in the matrix of dark fi ne grained ankerite (sample TANK1). Figure 16: Photomicrograph of the boundary area between coarse grained ankerite (sample TANK) and fi ne grained ankerite (sample TANK 1). Grain boundaries of fi ne grained ankerite are highly irregular, the interstitial space is fi lled with a clayey-carbonaceous substance (N+). is surrounded by dark fi ne grained siderite (sample TMIC) as shown in Fig. 17. Various parts of this non-homogeneous rock sample were carefully separated for chemical analysis. Geologia Croatica 65/2Geologia Croatica 262 interstitial spaces fi lled with a clayey-carbonaceous sub- stance and disseminated quartz grains. Partial breakdown of both types of siderite results in the occurrence of haematite along grain boundaries, cleavage and cracks in the siderite (Fig. 18). Ankerite and both type of siderite are character- ized by undulose extinction. The sample of yellow coarse grained siderite (sample AD-2) irregularly embedded in a matrix of reddish fi ne grai- ned siderite was collected in the Adamuša opencast mine (Fig. 19). Again, fi ne grained mineral is characterized by ir- regular boundaries and interstitial spaces fi lled with a clayey- carbonaceous substance and disseminated quartz grains, whe reas the coarse grained mineral consists of polygonal grains. Chemical analysis of yellow coarse grained siderite was undertaken, although due to the intimate association of yellow and reddish siderite it is possible that a minor quan- tity of reddish siderite was included in the analysis. Careful examination of mineral thin-sections using trans mitted polarized light enabled separation of the fresh and weathered samples, and the different parts of non-ho- mogeneous samples to be distinguished. Selected samples were crushed, hand–picked under binocular microscope and powdered in an agate mortar for chemical analysis. Major, minor and trace element contents were deter- mined by inductively coupled plasma mass spectrometry (ICP-MS) in the Acme Analytical Laboratories (Vancouver) Ltd in Canada. In the same laboratory the total organic car- bon (TOT/C) and total sulphure (TOT/S) of all six samples were measured too. 4. ANALYTICAL RESULTS 4.1. Main oxides The concentrations of many main oxides (SiO2, Al2O3, TiO2, Na2O, K2O) in compact limonite are slightly higher but very similar to those in siderite, limestone and dark fi ne grained ankerite (Table 1). Slightly lower concentrations of these oxides, (but still similar to those in siderite and limestone) are displayed in the white coarse grained ankerite. Pulver- ized limonite on the other hand differs signifi cantly, relative to compact limonite. The SiO2 component in pulverized li- monite is enriched by 3 times, Al2O3 component by 10 times, Na2O component by 7 times, K2O component by 4 times and the P2O5 component by 20 times compared to compact limo- nite (Table 1). These elevated values are mostly comparable to carbonate shale which is even more enriched in the SiO2 component (27.10 wt % compared to 16.73 wt % of pulver- ized limonite), but depleted in Al2O3 (only 4.99 wt % in com- parison with 11.78 wt% of pulverized limonite). There are positive correlations between the Al2O3, K2O and TiO2 con- tents and the aluminosilicate fraction of the samples. The Fe2O3 and MgO contents in siderite vary from 3.09 and 5.11 wt%, to 51.66 and 58.34 wt% respectively. In ankerite, the Fe2O3 content ranges from 13.94 to 21.35 wt%. Its MgO con- tent is between 9.29 and 10.41 wt%. MnO values are posi- tively correlated with Fe2O3 in all samples. The highest MnO content is present in siderite (2.15 to 2.55 wt%). Ankerite Figure 17: White coarse grained ankerite (sample TANMIC) occurs in the form of an irregular nest in a matrix of reddish coarse grained siderite (sam- ple TCOR) which is surrounded by dark fi ne grained siderite (sample TMIC). Figure 18: Photomicrograph of fi ne grained siderite (sample TMIC) with ir regular grain boundaries and interstitial spaces fi lled with a clayey-carbo- naceous substance and disseminated quartz grains. Red haematite occurs along cracks and cleavage of siderite because of weathering processes (N). Figure 19: Yellow coarse grained siderite (sample AD-2) irregularly em- bedded in a matrix of reddish fi ne grained siderite from the Adamuša opencast mine. White coarse grained ankerite and reddish coarse grained siderite are characterized by regular grain boundaries, whereas those of dark fi ne grained siderite are irregular with Garašić and Jurković: Geochemical characteristics of diff erent iron ore types from the Southern Tomašica deposit, Ljubija, NW Bosnia Geologia Croatica 263 shows lower MnO values (0.88 to1.10 wt%) and limestone has the lowest MnO value (0.10 wt%). The highest CaO con- tent in siderite is found in the red coarse grained TCOR sam- ple (3.98 wt%) in the immediate vicinity of the ankerite nests. The CaO content of the other two siderite samples var- ies from 1.34 to 1.63 wt%. Ankerite is characterized by a CaO content varying between 26.87 and 28.59 wt%. The greatest chemical differences between pulverized limonite and carbonate shale is visible in the content of Fe2O3 (3.27 wt% in carbonate shale and 53.87 wt% in pulverized limo- nite) and CaO (31.60 wt% in carbonate shale and 0.23 wt% in pulverized limonite). 4.2. REE content The REE content of ankerite, limestone, siderite and com- pact limonite is low (up to 22.49 ppm), in contrast to pulver- ized limonite (118.45 ppm) and carbonate shale (72.99 ppm), as reported in Table 2. There is a clear positive correlation between the weight percent of the main oxides SiO2 and Al2O3 and REE (Table 1, Table 2) in compact limonite, pul- verized limonite and carbonate shale. This suggests REE concentration dependence of the clay component in the sam- ples. However, the same correlation is not so obvious for carbonates. The REE concentrations of all the studied samples are normalized to C1 chondrite (SUN & McDONOUGH, 1989), in order to compare fractionations of light REE (La/Sm)N, heavy REE (Gd/Yb)N, total REE (La/Yb)N, Eu anomaly (Eu/ Eu* = EuN/√(SmxGd)N and Ce anomaly (Ce/Ce* = CeN/(√La x Pr)N) in different samples (Table 2). The REE pattern of compact limonite is characterized by relatively low light ((La/Sm)N = 2.87), heavy ((Gd/Yb)N = 0.98) and total ((La/Yb)N = 3.19) REE fractionations, a strong positive Eu anomaly (Eu/Eu* = 2.11) and weakly ex- pressed negative Ce anomaly (Ce/Ce* = 0.82) as shown in Table 2 and Fig. 20a. The total concentration of REE is 18.78 ppm. Limestone exhibits slightly lower REE abundance (Fig. 20b) and light REE fractionation (La/Sm)N = 2.29), but more strongly expressed heavy ((Gd/Yb)N = 2.31) and total ((La/ Yb)N = 5.08) REE fractionation compared to compact li- monite. Its Eu anomaly (Eu/Eu* = 1.12) is positive, but very weak, whereas the Ce anomaly (Ce/Ce* = 0.68) is negative and stronger than in compact limonite. The overall REE con- tent is 9.15 ppm. Studied coarse and fi ne siderite samples do not show differences in their REE patterns (Fig. 20c). They all display signifi cant enrichment of LREE over HREE ((La/Yb)N = 3.36–3.91, (La/Sm)N = 1.29–1.97, (Gd/Yb)N = 1.18–2.21), a pronounced positive Eu anomaly (Eu/Eu* = 2.24–3.40) and a small negative Ce anomaly (Ce/Ce* = 0.78–0.87). Their total REE concentrations vary from 13.71 to 13.23 ppm. In contrast to the REE patterns seen in siderite, those in ankerite show a clear distinction between fi ne grained and coarse grained samples (Fig. 20d). The REE pattern of fi ne Table 1: The main element content of the studied samples. Sample MDL TLIM TBRA TVAP1 TVAP2 TMIX TANK TANMIC TANK 1 TCOR TMIC AD-2 mineral/ rock   compact limonite pulverized limonite limestone carbonate shale ankerite ankerite ankerite ankerite siderite siderite siderite white gray fi ne to coarse grained white coarse grained white coarse grained dark fi ne grained red coarse grained dark fi ne grained yellow coarse grained   wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% SiO2 0.01 4.98 16.73 3.51 27.1 2.23 0.31 0.10 4.96 3.64 3.36 1.77 Al2O3 0.01 1.12 11.78 0.28 4.99 0.24 0.05 0.05 0.57 0.49 0.48 0.27 Fe2O3 0.04 79.61 53.87 0.87 3.27 18.41 16.91 21.35 13.94 51.66 54.41 58.34 MgO 0.01 0.13 0.74 0.61 2.08 9.47 10.41 9.29 10.29 4.99 5.11 3.09 CaO 0.01 0.15 0.23 52.24 31.6 27.18 28.59 26.87 28.47 3.98 1.63 1.34 Na2O 0.01 0.03 0.15 0.03 0.12 0.05 0.05 0.04 0.04 0.04 0.03 0.04 K2O 0.01 0.29 1.38 0.08 1.36 0.06 0.01 0.01 0.16 0.13 0.14 0.07 TiO2 0.01 0.05 0.47 <0.01 0.19 <0.01 <0.01 <0.01 0.02 0.01 0.02 0.01 P2O5 0.01 <0.01 0.22 0.02 0.06 <0.01 <0.01 <0.01 <0.01 0.03 0.02 <0.01 MnO 0.01 0.84 0.82 0.10 0.28 1.01 0.97 1.10 0.88 2.19 2.15 2.55 Cr2O3 0.002 <0.002 0.01 <0.002 0.007 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 LOI –5.1 12.70 13.40 42.10 28.80 41.20 42.50 41.10 40.50 32.70 32.60 32.4 Σ 0.01 99.90 99.80 99.84 99.86 99.85 99.80 99.91 99.83 99.86 99.95 99.88 TOT/C 0.02 0.27 0.44 11.74 8.28 11.77 12.22 11.96 11.43 10.40 10.59 10.43 TOT/S 0.02 <0.02 <0.02 <0.02 0.70 <0.02 <0.02 <0.02 0.03 <0.02 <0.02 0.03 Geologia Croatica 65/2Geologia Croatica 264 grained ankerite (sample TANK1) is similar to the siderite pat- terns showing enrichment of LREE over HREE ((La/Yb)N = 2.15), the positive Eu anomaly (Eu/Eu* = 1.95) and the neg- ative Ce anomaly (Ce/Ce* = 0.78). Differences exist in its lower (La/Sm)N ratio (0.89) and greater (Gd/Yb)N ratio (2.46) compared with siderite. Its ΣREE is 11.49 ppm. In contrast, two coarse grained ankerite samples (samples TANK and TANMIC) exhibit remarkable depletion of LREE over HREE ((La/Yb)N = 0.05–0.20), a strong reverse LREE pat- tern ((La/Sm)N = 0.04–0.10) and (Gd/Yb)N ratios ranging from 1.77 to 1.91. The coarse grained ankerite samples are like other studied samples characterized by positive Eu anomaly (Eu/Eu* = 2.16–2.75) and negative Ce anomaly (Ce/Ce* = 0.32–0.83) and their ΣREE vary between 5.54 and 15.25. The TMIX sample consisting of fi ne to coarse grained ankerite possesses the highest REE abundance (ΣREE = 22.49 ppm) among the studied ankerite samples and has characteristics similar to those of fi ne grained anker- ite (slight enrichment of LREE over HREE ((La/Yb)N = 1.22), a positive Eu anomaly (Eu/Eu* = 2.37), negative Ce anomaly (Ce/Ce* = 0.87), low (La/Sm)N ratio (0.47) and greater (Gd/Yb)N ratio (2.60)). In contrast to all other samples, pulverized limonite (Fig. 20a) and carbonate shale (Fig. 20b) show completely differ- ent REE patterns and abundances (up to 6 to 13 times higher relative to other samples) (Fig. 20c,d). Although pulverized limonite is characterized by the highest REE abundance (ΣREE = 118.45) its REE fractionation patterns ((La/Sm)N = 3.68, (Gd/Yb)N = 1.58, (La/Yb)N = 9.41), a slightly posi- tive Eu anomaly (Eu/Eu* = 1.10) and small negative Ce anomaly (Ce/Ce* = 0.81) are similar to those in the carbon- ate shale ((La/Sm)N = 4.09, (Gd/Yb)N = 1.91, (La/Yb)N = 10.63, (Eu/Eu* = 1.04, (Ce/Ce* = 0.89). 4.3. Other trace elements The content of Rb, Cs, Ba and Ga are characterized by a positive correlation with K2O and Al2O3 values, pointing to the aluminosilicate fraction of the samples. Consequently, the pulverized limonite contains the highest values of Rb (74.2 ppm), Cs (14.8 ppm), Ba (227 ppm) and Ga (14.1 ppm). It is also characterized by the highest concentrations of V (104 ppm), Zr (115.2 ppm) and Y (19.3 ppm). Table 2: Rare earth element composition of the studied samples. Sample MDL TLIM TBRA TVAP1 TVAP2 TMIX TANK TANMIC TANK 1 TCOR TMIC AD-2 mineral/ rock compact limonite pulverized limonite limestone carbonate shale ankerite ankerite ankerite ankerite siderite siderite siderite white gray fi ne to coarse grained white coarse grained white coarse grained dark fi ne grained red coarse grained dark fi ne grained yellow coarse grained   ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm La 0.10 3.60 27.3 1.70 16.30 1.40 <0.10 <0.10 1.20 2.20 2.60 1.80 Ce 0.10 5.50 42.6 2.40 27.70 3.90 0.40 0.10 2.30 4.10 5.10 3.80 Pr 0.02 0.75 6.16 0.44 3.55 0.86 0.14 0.06 0.44 0.75 0.86 0.63 Nd 0.30 3.20 22.3 1.80 13.80 4.60 1.00 0.80 2.40 3.10 4.40 2.90 Sm 0.05 0.81 4.79 0.48 2.57 1.91 0.62 1.57 0.87 0.72 0.95 0.90 Eu 0.02 0.61 1.57 0.21 0.87 1.72 0.50 1.91 0.65 0.51 0.74 0.99 Gd 0.05 0.96 3.97 0.67 2.54 2.58 0.81 2.87 1.19 0.67 0.85 0.88 Tb 0.01 0.18 0.63 0.10 0.40 0.45 0.15 0.55 0.18 0.12 0.15 0.13 Dy 0.05 1.06 3.64 0.58 2.14 2.31 0.77 3.09 1.01 0.75 0.97 0.67 Ho 0.02 0.25 0.73 0.13 0.43 0.47 0.15 0.59 0.19 0.17 0.22 0.14 Er 0.03 0.81 2.03 0.32 1.23 1.20 0.43 1.82 0.52 0.50 0.62 0.41 Tm 0.01 0.13 0.34 0.05 0.19 0.16 0.07 0.26 0.08 0.09 0.10 0.07 Yb 0.05 0.81 2.08 0.24 1.10 0.82 0.35 1.34 0.40 0.47 0.53 0.33 Lu 0.01 0.11 0.31 0.03 0.17 0.11 0.05 0.19 0.06 0.08 0.08 0.06 ΣΡΕΕ   18.78 118.45 9.15 72.99 22.49 5.54 15.25 11.49 14.23 18.17 13.71 Eu/Eu* 2.11 1.10 1.13 1.04 2.37 2.16 2.75 1.95 2.24 2.52 3.40 Ce/Ce* 0.82 0.80 0.68 0.89 0.87 0.83 0.32 0.78 0.78 0.84 0.87 (La/Yb)N 3.19 9.41 5.08 10.63 1.22 0.20 0.05 2.15 3.36 3.52 3.91 (La/Sm)N 2.87 3.68 2.29 4.09 0.47 0.10 0.04 0.89 1.97 1.77 1.29 (Gd/Yb)N 0.98 1.58 2.31 1.91 2.60 1.91 1.77 2.46 1.18 1.33 2.21 Garašić and Jurković: Geochemical characteristics of diff erent iron ore types from the Southern Tomašica deposit, Ljubija, NW Bosnia Geologia Croatica 265 Figure 20: Plot of rare-earth elements normalized to C1 chondrites (SUN & McDONOUGH, 1989) in: a) compact and pulverized limonite; b) limestone and carbonate shale; c) siderite; d) ankerite. The Sr content increases with the increasing calcium content of the samples due to the crystal chemical control. Consequently the Sr content increases from siderite (12.3 to 14.9 ppm), and ankerite (42.4 to 79.5 ppm) to being highest in the limestone (1051 ppm). The concentrations of Co, Ni, Pb, Zn and As, show a positive correlation with Fe2O3 in siderite samples, whereas in the ankerite samples such correlation doesn’t exist. The content of Co, Ni and As in ankerite samples are positively correlated with Al2O3 and SiO2 components, whereas the Pb, Zn and Cu contents are most likely linked to the presence of tiny sulphides near the grain boundaries. The highest values of Ni (36.4 ppm), Pb (116.6 ppm), Zn (345 ppm), As (382.8 ppm) and Cu (52.4 ppm) are found in pulverized limonite, whereas the carbonate shale is characterized by the highest content of Co (25.9 ppm). The compact limonite contains elevated concentrations of many trace elements (Cs, Ga, Hf, Rb, Th, V, Zr,Y, Cu, Zn, Ni and Sb) relative to siderite, ankerite and limestone (Table 3). In the same comparison the highest contents of Co (5.60 ppm) and As (4.60 ppm) are found in siderite, of Hg (0.14 ppm) in ankerite and of U (1.60 ppm) and Pb (11.1 ppm) in the limestone. In comparison with compact limonite, siderite, ankerite and limestone the concentrations of Ni, Co, Cs, Ga, Hf, Nb, Rb, Ta, Th, U, V, W. Zr, Y, Mo, Cu, Pb, Zn, As, Sb and Hg are even more elevated in the pulverized limonite and car- bonate shale (Table 3). The only elements having higher con- centrations in the carbonate shale than in pulverized limonite are Co, Bi, Ag, Hg and Se (Table 3). 5. DISCUSSION Geochemical investigations of two limonite ore types show considerable differences in the content of their main ele- ments, REE and other trace elements. In order to constrain their possible lithotype sources, the geochemical character- istics of studied siderite, ankerite, host limestone and car- bonate shale are further discussed. 5.1. REE chemistry of carbonate phases Generally, many factors may infl uence the REE content of carbonate minerals. The most important include the size of sites occupied by REE ions in the crystal lattice, REE chem- istry of mineralizing fl uids and REE partitioning between the precipitating mineral and mineralizing fl uid (MÖLLER, 1983). In addition, according to MÖLLER et al. (2004), REE abundances are higher in hydrothermal than in cold fl uids and increase with decreasing pH (MICHARD, 1989). In acid solutions LREEs are enriched relative to HREEs, Geologia Croatica 65/2Geologia Croatica 266 Table 3: Trace element content of the studied samples. Sample MDL TLIM TBRA TVAP1 TVAP2 TMIX TANK TANMIC TANK 1 TCOR TMIC AD-2 mineral/ rock compact limonite pulverized limonite limestone carbonate shale ankerite anker- ite ankerite ankerite siderite siderite siderite white gray fi ne to coa rse grai ned white coarse grained white coarse grained dark fi ne grained red coarse grained dark fi ne grained yellow coarse grained   ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm Sc 1.0 2.0 12.0 <1.0 5.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 1.0 Ba 1.0 201.0 227.0 26.0 140.0 24.0 5.0 8.0 18.0 17.0 21.0 44.0 Be 1.0 1.0 2.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 Co 0.2 2.7 18.1 0.2 25.9 2.7 0.5 0.8 4.1 3.6 5.6 11.7 Cs 0.1 1.8 14.8 0.4 9.3 0.4 0.2 0.2 0.6 0.7 0.7 0.3 Ga 0.5 3.2 14.1 0.5 7.4 0.6 0.5 0.5 1.0 2.7 3.1 3.9 Hf 0.1 0.5 3.3 0.1 1.0 0.1 0.1 0.1 0.2 0.2 0.2 0.1 Nb 0.1 1.0 10.2 0.3 4.1 0.2 0.1 0.1 0.5 0.3 0.3 0.4 Rb 0.1 11.9 74.2 3.2 55.0 2.4 0.5 0.5 6.3 5.1 5.5 3.2 Sn 1.0 <1.0 3.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 <1.0 Sr 0.5 7.3 42.4 1051.1 357.3 55.1 79.5 42.4 66.5 14.4 12.3 14.9 Ta 0.1 <0.1 0.8 0.1 0.3 0.1 0.1 0.1 0.1 0.1 0.1 <1.0 Th 0.2 1.0 8.9 0.3 4.0 0.5 0.2 0.2 0.3 0.6 0.6 0.5 U 0.1 0.9 5.5 1.6 4.6 0.7 0.1 0.1 0.1 0.4 0.5 2.5 V 8.0 19.0 104.0 8.0 70.0 8.0 8.0 8.0 8.0 8.0 11.0 12.0 W 0.5 <0.5 1,5 0.5 1.2 0.5 0.5 0.5 0.5 0.5 0.5 <0.5 Zr 0.1 20.0 115.2 2.3 31.9 1.6 1.0 0.4 5.9 5.3 6.6 4.4 Y 0.1 7.7 19.3 4.8 14.0 15.3 5.5 17.8 7.8 5.0 5.8 4.8 Mo 0.1 <0.1 2.5 0.1 9.9 0.1 0.2 0.1 0.8 0.2 0.3 0.5 Cu 0.1 9.3 52.4 0.7 22.7 2.6 2.2 30.7 3.5 2.4 1.5 1.6 Pb 0.1 3.4 116.6 11.1 54.3 1.7 1.8 1.8 5.0 1.3 1.5 136.7 Zn 1.0 57.0 345.0 14.0 25.0 14.0 22.0 14.0 17.0 24.0 35.0 46.0 Ni 0.1 10.7 36.4 1.2 35.6 4.3 1.1 1.6 6.3 5.4 7.2 11.6 As 0.5 1.2 382.8 0.5 34.8 4.3 0.5 0.5 6.7 3.6 4.6 5.5 Cd 0.1 <0.1 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 <1.0 Sb 0.1 0.8 3.5 0.3 4.5 0.2 0.1 0.1 1.2 0.1 0.2 0.6 Bi 0.1 <0.1 0.3 0.1 0.9 0.1 0.1 0.1 0.2 0.1 0.1 <1.0 Ag 0.1 <0.1 0.1 0.1 0.8 0.1 0.1 0.1 0.1 0.1 0.1 <1.0 Au* (ppb) 0.5 <0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 1.5 0.5 <0.5 Hg 0.01 0.04 0.52 0.05 0.7 0.05 0.13 0.01 0.14 0.03 0.03 0.09 Tl 0.1 <0.1 0.3 0.1 0.2 0.1 0.1 0.1 0.1 0.1 0.1 <1.0 Se 0.5 <0.5 0.5 0.5 1.9 0.5 0.6 0.5 0.5 0.5 0.5 <0.5 Zr/TiO2   0.040 0.025 >0.023 0.017 >0.016 >0.010 >0.004 0.030 0.053 0.033 0.044 Zr/Nb 20.000 11.290 7.670 7.780 8.000 10.000 4.000 11.800 17.670 22.00 11.000 Nb/Y 0.130 0.530 0.060 0.290 0.010 0.020 0.010 0.060 0.060 0.050 0.080 whereas al kaline solutions exhibit depletion of the LREEs over HREEs usually having La/Lu < 1 (SCHWINN & MARKL, 2005). In the context of crystal chemistry, calcite should be characterized by enrichment of LREE over HREE in contrast to siderite that should display depletion of LREE over HREE. Garašić and Jurković: Geochemical characteristics of diff erent iron ore types from the Southern Tomašica deposit, Ljubija, NW Bosnia Geologia Croatica 267 Ankerite should show intermediate characteristics between these two patterns. The larger Ca ion site in calcite incorpo- rates larger LREEs more easily, whereas the smaller Fe ion site in siderite easily incorporates smaller HREEs. Thus the LREE enrichment in siderite (Fig. 20), and its overall greater REE content (ΣREE = 13.71–18.17 ppm) in comparison with limestone (ΣREE = 9.15 ppm), could not be solely attributed to crystallographic control, but indicates the precipitation of siderite from an LREE enriched parent fl uid. Strong depletion of LREE over HREE ((La/Yb)N = 0.05–0.20) in the two white coarse grained ankerites on the other hand reveals that they were precipitated either from a colder and more alkaline mineralizing fl uid, or from a fl uid with a different source relative to siderite and fi ne grained ankerite. The negative Ce anomaly, being the result of the oxida- tion of Ce3+ to Ce4+ and its consequent removal from the so- lution as CeO2, is typical for marine limestones (HU et al., 1988). The studied limestone exhibits a pronounced nega- tive Ce anomaly (0.68) and weak positive Eu anomaly (1.13). The negative Ce anomaly, although weaker, is present in siderite (0.78–0.87), fi ne grained ankerite (0.78), and also in one coarse grained ankerite (0.83). Its lower values relative to limestone could be explained by lower pH or a lower pO2 of mineralizing fl uids from which siderite and ankerite sam- ples precipitated. The presence of a signifi cant negative Ce anomaly (0.32) in the TANMIC sample (coarse grained an- kerite) indicates more oxygenated conditions for its precip- itation. The additional noticeable feature in the studied carbon- ate REE patterns is a pronounced positive Eu anomaly in siderite (2.24–3.40) and coarse grained ankerite (2.16–2.75). It is weaker in the fi ne grained ankerite (1.95) and weakest in the limestone (1.13). Numerous analyses of REE concen- trations in hydrothermal fl uids along oceanic ridges (MI- CHARD & ALBAREDE, 1986; CAMPBELL et al., 1988) revealed that hydrothermal fl uids are enriched in ΣREE (10– 104 times relative to seawater concentrations), and are char- acterized by a signifi cant positive Eu anomaly (OLIVAREZ & OWEN, 1991). Furthermore, textural evidence (the oc- currence of veins and nests) in the studied siderite and an- kerite samples from the Olistostrome member in Javorik For- mation support the hydrothermal origin. The interaction between some Eu-rich mineralizing fl uid and limestone could be refl ected in the LREE depletion of ankerite, due to effective HREE complexion. Additionally, the strong simi- larity in the content and the fractionation of HREE in fi ne grained ankerite and limestone (Fig. 20) might also indicate the possible involvement of limestone in the origin of anker- ite. The analytical results obtained are in accordance with those published by STRMIĆ PALINKAŠ et al. (2009) who suggested a hydrothermal-metasomatic origin of the Fe min- eralization. However, it should be emphasized that there was more than one hydrothermal stage. This is refl ected in ore texture (fi ne grained, coarse grained, veins, nests), colour (white, gray, red) and chemical features. Signifi cantly lower Al2O3 values occur in white coarse grained ankerite (0.05 wt.%) when compared to those in fi ne grained ankerite (0.57 wt%) and siderite (0.27–0.49 wt%). However, due to the lack of a clear positive correlation between wt% Al2O3 and ΣREE (see Table 1 and 2) it seems that the REEs are not hosted in detrital phases of carbonate samples. 5.2. REE chemistry of compact limonite The REE pattern of compact limonite ((La/Sm)N = 2.87, (Gd/Yb)N = 0.98, (La/Yb)N = 3.19, Eu/Eu* = 2.11, Ce/Ce* = 0.82) and its other trace element content (Table 3), exhib- its the closest genetic relationship with siderite. Chemical wea thering of siderite most probably resulted in its extensive supergene modifi cation and the origin of compact limonite. Textural relationships and fi eld occurrences of siderites and compact limonite support such a concept. It is also in accor- dance with the opinions of earlier investigators in this area (JURKOVIĆ, 1961; GRUBIĆ & PROTIĆ, 2003). The for- mation of limonite due to siderite weathering is observed and documented in many other geological environments (MORRIS, 1980). 5.3. REE chemistry of carbonate shale and pulverized limonite Considering the fractionation of light REE (La/Sm)N, heavy REE (Gd/Yb)N and total REE (La/Yb)N when normalized to chondrite (SUN & McDONOUGH, 1989), the REE pattern of the studied carbonate shale is similar to those of the North American Shale Composite (NASC – GROMET, 1984), and the Post Archean Australian Shale (PAAS – McLENNAN, 1989) as shown in Fig. 21. The most remarkable difference is the absence of the pronounced negative Eu anomaly in the carbonate shale, which is typical for NASC and PAAS. Car- bonate shale displays almost no Eu anomaly (Eu/Eu* = 1.04) and has a small negative Ce anomaly (Ce/Ce* = 0.89). An analogous REE pattern, but with enhanced overall REE content, is shown by pulverized limonite (Eu/Eu* = 1.10; (Ce/Ce* = 0.81). Consequently, the carbonate shale might be one of the suitable lithotypes for providing the REE content to pulverized limonite. GRUBIĆ & PROTIĆ (2003) Figure 21: Plot of rare-earth elements normalized to C1 chondrites (SUN & McDONOUGH, 1989) in compact and pulverized limonite compared with the REE pattern of North American Shale Composite (NASC – GROMET, 1984) and Post Archean Australian Shale (PAAS – McLENNAN, 1989). Geologia Croatica 65/2Geologia Croatica 268 described comb-textured ankerite and dolomite limestone being completely enclosed by pulverized limonite. Therefore they concluded that the weathering of ankerite led to the for- mation of pulverized limonite. The REE pattern of pulve- rized limonite analysed in this study differs strongly from the REE patterns of any ankerite types analysed here and hence would contradict such a conclusion. However, it has to be emphasized that the analysed sample of pulverized li- monite (TBRA) was not taken in its original place of forma- tion, but in the Pleistocene–Quaternary lake limonite deposit (Sto jan čići location). During transportation by rain, river or wind, pulverized limonite could become more or less contamina ted. The enhanced overall REE content in pulver- ized limo ni te (ΣREE = 118.45 ppm) relative to compact li- monite (18.78 ppm), may be explained by such crustal rock contamination. 5.4. Other trace elements Considerably higher concentrations of other trace elements in siderite samples (Co = 3.6–11.7 ppm; Ni =5.4–11.6 ppm; Rb = 3.2–5.5 ppm; Zr = 4.4–6.6 ppm), and fi ne grained an- kerite (Co = 4.1 ppm; Ni = 6.3 ppm; Rb = 6.3 ppm; Zr = 5.9 ppm), relative to those in white coarse ankerite (Co = 0.5–0.8 ppm; Ni = 1.1–1.6 ppm; Rb = 0.5 ppm; Zr = 0.4–1.0 ppm), support the hypothesis of the precipitation of fi ne grained ankerite and white coarsed ankerite from different mineral- izing fl uids. Trace elements are in general depleted in compact li- monite relative to pulverized limonite. The high values of Zr (115.2 ppm) in pulverized limonite indicate the possible presence of a clastic component of igneous origin, whereas high values of Rb (74.2 ppm), Sr (42.4 ppm), Th (8.9 ppm) indicate components derived by weathering from crustal fel- sic rocks. The enhanced concentrations of Cu (52.4 pppm), Pb (112 ppm), Zn (345 ppm) and As (382.8 ppm) may be at- tributed to the presence of components arising from the wea- thering of sulphide minerals. The ratios of some immobile trace elements such as Zr/TiO2 and Nb/Y are regarded as very useful for protolith determination (WINCHESTER & FLOYD, 1977) because they don’t change during weathering processes. The values of the Zr/TiO2 ratio in compact limonite (0.040) and siderite (between 0.033 and 0.053), are in concordance with the pos- tulated origin of compact limonite from siderite. In the fi ne grained ankerite (sample TANK1), the Zr/TiO2 ratio is 0.030, whereas in the coarse grained ankerite it varies between 0.004 and 0.010. As pulverized limonite has a Zr/TiO2 ratio of 0.025, only fine grained ankerite or carbonate shale (0.017) might be regarded as its possible protolith. Similar conclusions could be drawn on the basis of the Zr/Nb ratio which in siderite varies from 11 to 22 and in compact li- monite is 20. In the pulverized limonite, the Zr/Nb ratio is 11.29, in carbonate shale 7.78, in the fi ne grained ankerite 11.8, and in the coarse grained ankerite it ranges between 4 and 10. However, the values of the Nb/Y ratios in pulverized limonite (0.53), carbonate shale (0.29), compact limonite (0.13), siderites (0.05–0.08), fi ne grained ankerite (0.06) and coarse grained ankerite (0.01–0.02) do not support the pos- sibility of the origin of pulverized limonite through the wea- thering processes of ankerites. 5.5. Field relationships and geochemical data The fi eld relationship between siderite and compact limo- nite, is consistent with the conclusion based on REE geo- chemistry, that compact limonite most probably originated by the alteration of siderite. Compact limonite occurs as gos- san formed in situ on siderite. Pulverized limonite occurs in the fi eld as bedded and lensoid shape deposits in palaeolakes, but also enclosing an- kerite relics and ankeritic limestone in the Olistostrome me- mber. The analyzed sample of pulverized limonite from a limonite deposit from the palaeolake exhibits signifi cantly distinct REE patterns relative to any ankerite types studied in this paper. Carbonate shale is part of a fl ysch groundmass of the Olistostrome member in which carbonate olistolith frag- ments, blocks and their mineralized parts are embedded. The remarkable resemblance of its REE pattern with that of pul- verized limonite indicates the possibility that pulverized li- monite may generally originate by the alteration of a carbon- ate shale or fl ysch groundmass. 6. CONCLUSION Two studied types of limonite ore from the Southern To ma- šica mine display a notably distinct REE pattern, REE frac- tionations, Eu anomalies and contents of other trace ele- ments and main oxides. The compact limonite formed in situ on siderite is characterized by remarkable lower overall REE abundances, lower LREE fractionation, lower and opposite HREE fractionation, a more strongly expressed positive Eu anomaly and far lower overall content of other trace ele- ments compared to pulverized limonite. This supports the hypothesis of different protolith material for the two differ- ent limonite ore types. The REE pattern of compact limonite and siderite almost overlap, supporting the interpretation of former investigators (JURKOVIĆ, 1961; GRUBIĆ & PROTIĆ, 2003) who con- cluded that compact limonite originated by the alteration of siderite. The REE pattern of pulverized limonite on the other hand clearly differs from that of ankerite, which GRUBIĆ & PROTIĆ (2003) regarded as the protolith of pulverized limonite. On the basis of the similarity of their REE patterns, other trace element contents and Zr/TiO2 ratios, carbonate shale might be regarded as a potential protolith of pulverized limonite. Alternatively, assuming that the analysed samples of pulverized limonite, collected in the Pleistocene–Quater- nary lake limonite deposit, were contaminated during trans- portation by rain, river or wind, fi ne grained ankerite might also, on the basis of its Zr/TiO2 ratio and Eu and Ce anomaly, be a potential protolith of pulverized limonite. In order to develop full understanding of the formation of all limonite types in this area, the REE pattern and con- Garašić and Jurković: Geochemical characteristics of diff erent iron ore types from the Southern Tomašica deposit, Ljubija, NW Bosnia Geologia Croatica 269 tent of other trace elements in siderite occuring as lenses in the lowest parts of the geological column of Southern To- mašica, and in the superposed limonite (Siderite-limonite member) and in pulverized limonite enclosing ankerite rel- icts (Olistostrome member) remain to be investigated. ACKNOWLEDGEMENT We are gratefull to Nenad RAKOVIĆ and Zorana GRUB- LJE ŠIĆ from Ljubija iron ore mines who, thanks to their extensive fi eld experience and work over many years on iron deposits, helped with locating the most appropriate places for sampling. We also thank Sabina STRMIĆ PALINKAŠ and an anonymous reviewer for their fruitful critical reviews, which have helped improve this paper. REFERENCES BOROJEVIĆ ŠOŠTARIĆ, S. 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