The Ljubija geothermal field: A herald of the Pangea break-up (NW Bosnia and Herzegovina)

Abstract

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 (veins, veinlets) in phyllites and sandstones. The genesis of the Ljubija ore deposits has been explained as (i) syngenetic sedimentary-exhalative, (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. This contribution presents a set of new data on ore petrology, geochemistry, geology and time of formation. The Ljubija ore field could justifiably be termed the “Ljubija geothermal field”, due to its areal extent and the thermal characteristics of numerous ore deposits and occurrences within the Sana-Una Palaeozoic terrain. The Ljubija geothermal field marks the first signs of thermal instability of Pangea, revealing its breakdown along the deep fractures and heralding incipient intracontinental rifting, the first phase of the new Alpine Wilson cycle. The research reveals novel data on the P-T-X characteristics of ore forming fluids (microthermometry, ion chromatography, Raman spectrometry), sulphur isotopes, maturity of organic matter by vitrinite reflection, and age determination by 40Ar/39Ar and K-Ar methods. It adopts argumentatively all the estimated research parameters that constrain a justified genetic model.