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 245A degrees C) then for siderite vein
(around 185A degrees 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.