Samoborska Gora Mts. is situated within the westernmost part of the
Zagorje-Mid-Transdanubian zone of the Internal Dinarides. The Samoborska
Gora Mts. predominantly consists of Permian unmetamorphosed
siliciclastic sediments 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 +/-
CaCl(2)-H(2)O solutions. Detrital quartz from stratiform mineralisation
contains fluid inclusions with salinities between 7 and 11 wt. % NaCl
equ., homogenizing between 150 degrees C to 230 degrees 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 degrees C and 160 degrees C, while late
stage galenabarite veins were precipitated from solutions with
salinities between 11 and 16 wt. % NaCl equ., homogenizing between 100
degrees C to 140 degrees C. Fluid inclusion bulk leachate chemistry
recorded Na(+)> Mg(2+)>K(+)>Ca(2+)>Li(+) and Cl-> SO(4)(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 parts per
thousand , as a result of thermal reduction of Permian marine sulphate.
Ore-forming fluids were produced by hydrothermal convective cells
(reflux brine model), and were derived primarily from Permian seawater,
modified 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.