Metallogeny of the Ljubija ore region Grubić, Aleksandar; Milošević, Aleksej; Cvijić, Ranko ...
Mining and Metallurgy Engineering Bor,
2021, Letnik:
2021, Številka:
3-4
Journal Article
Recenzirano
Odprti dostop
The Ljubija ore region is a part of the Triassic, regional, internal metallogenetic zone of the Middle Dinarides. It is located approximately in the middle of this larger metallogenetic unit and has ...many characteristics in common with its other parts. After many wanderings in the interpretation of the genesis of iron ore in Ljubija, it was definitely determined that the metallogeny of iron is of the Triassic age, then, that it is associated with the deep rift dislocations, which allowed the circulation of hydrothermal solutions originating from the Upper mantle, that the primary economic concentrations of iron are found only in the Olistostromic member of the Javorik flysch formation and the secondary ones, redeposited in the Neogene-Quaternary lake sediments of the Prijedor-Omarska basin. Based on the distribution of mineralization in the Ljubija ore region, two ore subregions, one polymetallic ore zone and a group of ore fields with barite, were identified. All the above knowledge, along with the analysis of control factors of mineralization and the main prospective indications, enabled the division of entire region into areas with various categories of perspectives according to the justification of further research. Based on the results of many years of research, this work presents the results of metallogenetic analysis of the Ljubija ore region. All results of the future research should continuously supplement, correct and improve the metallogenetic and prognostic map and our metallogenetic knowledge about the region.
The Žune Ba-F epithermal deposit is situated in the Ljubija ore field (NW Bosnia and Herzegovina), within Upper Palaeozoic dolostone. A typical ESE-WNW Variscan vergency fault zone separates the ...dolostone from Lower Triassic schists and sandstones. External and internal pseudo-bedding, with massive, homogenous structure and partial limonitization characterizes the dolostone. Its geochemical composition exhibits low SiO2 (1.33 – 2.06 mass. %), Al2O3 (0.27 –0.38 mass. %), BaO (0.02 – 0.83 mass. %), ƩREE (5.7 – 9.4 ppm), Sr (61.7 – 120.4 ppm), Sm (0.3 – 2.2 ppm) and Eu (0.1 – 0.6 ppm), while having high CaO (30.24 – 32.38 mass. %), MgO (16.47 – 17.35 mass. %) and LOI (44.6 – 45.58 mass. %). The dolostone-mineralization contact zone consists of metasomatically recrystallised host dolostone with quartz and pyrite, where the presence of accessory tremolite, magnesiochloritoid and pyknite indicates peak formation conditions in the pre-mineralization phase with temperatures above 300°C. Two ore types are described: (i) Ba-F vein-type mineralization composed of barite – fluorite ± quartz, and (ii) hydrothermal breccia composed of coarse-grained fluorite and barite, surrounding fragments of dolostone, and occupying ≈20 % of the deposit. Mineralized samples show slightly elevated SiO2 (2.20 – 5.53 mass. %) and Al2O3 (0.24 – 0.74 mass. %), low MgO (below 0.02 mass. %) and LOI (0.3 – 3.1 %), with high BaO (up to 50.74 mass. %), CaO (up to 66.03 mass. %), ƩREE (20 – 166 ppm), Sr (exceeding 1 mass. %), Sm (up to 118 ppm) and Eu (up to 44 ppm). Elevated Sr can be correlated to other barite epigenetic hydrothermal deposits in the Dinarides, interpreted as BaSr substitution in the barite crystal lattice. Fluorite-rich samples are characterized by Y (0.6 –49.2 ppm) and HREE enrichment, accompanied by depletion of LREE. The Ba-F deposit Žune, having variable REE concentration and a negative cerium and ytterbium anomaly corresponds geochemically to world-class fluorite deposits associated with carbonate sedimentary rocks.
The Ljubija ore deposits are the loci typici of siderite-barite-polysulphide deposits within the Inner Dinarides, Gemerides and Eastern Alps. Numerous sites of ore outcrops, smaller or larger ore ...bodies of mineralization, consisting of Fe carbonates, sulphides, barite and fluorite are scattered over an area of 150 square km. The half billion tons of iron ore resources occur as replacement in dolostones and limestones, and as open-space fillings in phyllites and sandstones. The genesis of the Ljubija ore deposits has been explained as (i) syngenetic sedimentary-exalative, (ii) hydrothermal-metasomatic in Middle Triassic time or (iii) hydrothermal replacement of sedimentary carbonates in Permian time. Basically two alternatives Variscan or Alpine metallogeny, frame the time of genesis from the Middle Carboniferous to the Middle Triassic. Genetic interpretation of the Ljubija ore deposits required convincing arguments based on recent achievements of plate tectonics. It adopts argumentatively all the estimated research parameters that constrain a justified genetic model.
The Ljubija siderite deposits, hosted by a Carboniferous sedimentary complex within the Inner Dinarides, occur as stratabound replacement-type ore bodies in limestone blocks and as siderite–sulfides ...veins in shale. Three principal types of ore textures have been recognized including massive dark siderite and ankerite, siderite with zebra texture, and siderite veins. The ore and host rocks have been investigated by a combination of inorganic (major, trace, and rare earth element concentrations), organic (characterization of hydrocarbons including biomarkers), and stable isotope geochemical methods (isotope ratios of carbonates, sulfides, sulfates, kerogen, and individual hydrocarbons). New results indicate a marine origin of the host carbonates and a hydrothermal–metasomatic origin of the Fe mineralization. The differences in ore textures (e.g., massive siderite, zebra siderite) are attributed to physicochemical variations (e.g., changes in acidity, temperature, and/or salinity) of the mineralizing fluids and to the succession and intensity of replacement of host limestone. Vein siderite was formed by precipitation from hydrothermal fluids in the late stage of mineralization. The equilibrium fractionation of stable isotopes reveals higher formation temperatures for zebra siderites (around 245°C) then for siderite vein (around 185°C). Sulfur isotope ratios suggest Permian seawater or Permian evaporites as the main sulfur source. Fluid inclusion composition confirms a contribution of the Permian seawater to the mineralizing fluids and accord with a Permian mineralization age. Organic geochemistry data reflect mixing of hydrocarbons at the ore site and support the hydrothermal–metasomatic origin of the Ljubija iron deposits.
U radu se analizira promjena korištenja zemljišta i dinamika stanovništva dvaju ruralnih područja definiranih kontaktnim krškim izvorima, odnosno njihovim slijevnim područjima. Slijev izvora Ljubija ...u sjeveroistočnom dijelu Slovenije i slijev izvora Gradole, vodom najbogatiji izvor u Istri u sjeverozapadnoj Hrvatskoj, istraženi su kroz okolišne, društvene i povijesne aspekte korištenja zemljišta.
U analizi su korišteni statistički podatci i geografski informacijski sustavi (GIS). U okviru multidisciplinarnoga pristupa utvrdili smo: 1) oba područja su pod određenim stupnjem zaštite (upravljanja) zbog resursa pitke vode, Gradole s 9,8 % i Ljubija s 8,9 % zaštićene površine; 2) podatci o društvenim značajkama pokazali su da ljudski pritisak nije značajno narušavao prirodne uvjete i ranjivost vodoopskrbe. Područje izvora Ljubija rjeđe je naseljeno od slijevnoga područja izvora Gradole (1,4 stan./km2 prema 38,7 stan./km2), ali Ljubija ima izraženiji rast broja kućanstava – I2020/1948 = 115 naprema I2020/1948 = 88,1 kod izvora Gradole. Ograničene regeneracijske sposobnosti krških vodnih tijela sačuvane su 3) prevladavajućim udjelom šuma; podatci o korištenju zemljišta pokazali su 84,8 % u području Ljubije i 34,4 % u području izvora Gradole.
PDF
