Original scientific paper

Permian–polysulphide-siderite–barite–haematite deposit Rude in Samoborska Gora Mts., Zagorje–Transdanubian zone of the Inner Dinarides

Sibila Borojevic Sostaric ; Department of Geology, Faculty of Science, University of Zagreb
Ladislav Antun Palinkaš ; Department of Geology, Faculty of Science, University of Zagreb
Sabina Strmić Palinkaš ; Department of Geology, Faculty of Science, University of Zagreb
Walter Prochaska ; Institut für Geowissenschaften, Montanuniversität Leoben
Jorge Spangenberg ; Institute of Mineralogy and Geochemistry, University of Lausanne
Stella Cuna ; National Institute for Research and Development of Isotopic and Molecular Technologies
Boris Šinkovec ; Faculty of Geology, Mining and Petroleum Engineering, University of Zagreb

Abstract

Samoborska Gora Mts. is situated within westernmost part of the Zagorje–Mid–Transdanubian zone of the Inner Dinarides. The Samoborska Gora Mts. consists dominantly of Permian unmetamorphosed siliciclastic sediments and evaporites, overlain by Lower Triassic sediments. Rude mineralization is hosted by Permian siliciclastic sediments, beneath gypsum and anhydrite strata. Central part of the deposit consists of 1.5 km long stratabound mineralization, grading laterally into ferruginous sandstone and protruding vertically into a gypsum–anhydrite layer. Siderite–polysulfide–barite–quartz veins are located underneath the stratabound mineralization. Late stage galena–barite veins overprints the formerly formed mineralization types.

The Rude ore deposit was generated by NaCl±CaCl₂–H₂Osolutions. Stratabound mineralization was precipitated from solutions with salinities between 7 and 11 wt. % NaCl equ., homogenizing between 150°C to 230°C. Vein type mineralization derived from solutions with salinities between 4 and 20 wt. % NaCl equ., homogenizing between 80°C and 160°C, while late stage galena–barite veins were precipitated from solutions with salinities between 11 and 16 wt. % NaCl equ., homogenizing between 100°C to 140°C. Fluid inclusions bulk leachate chemistry recorded Na+>Mg2+>K+>Ca2+>Li+ and Cl–>SO₄2– ions. Sulfur isotope composition of barites and overlying gypsum steams from the Permian seawater sulfate, supported by increased Br– content, which follows successively the seawater evaporation line. The sulfur isotopic composition of sulfides varies between –0.2 and +12.5 ‰, as a result of thermal reduction of Permian marine sulfate. Ore–forming fluids were produced by hydrothermal convective cells (reflux brine model) and derived primarily from Permian seawater,- modified by evaporation and interaction with the Permian sedimentary rocks. Rude deposits in Samoborska Gora Mts. may be declared as a prototype of the Permian siderite–polysulfide–barite deposits, products of the rifting along the passive Gondwana margin, in the Inner Dinarides, and their equivalents in extension northeastward into Zagorje–Transdanubian Zone and Gemerides, and southeastward to Hellenide–Albanides.<-->

Samoborska Gora Mts. is situated within the westernmost part of the Zagorje–Mid–Transdanubian zone of the Inner Dinarides. The Samoborska Gora Mts. predominantly consists of Permian unmetamorphosed siliciclastic sediments and evaporites, overlain by Lower Triassic sediments. Rude mineralization 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 mineralization, grading laterally into ferruginous sandstone and protruding vertically into a gypsum–anhydrite layer. Siderite–polysulphide–barite–quartz veins are located below the stratabound mineralization. The stratiform part of the deposit is situated above the stratabound and consists of haematite lajer with barite concretions and veinlets. Late stage galena–barite veins overprint earlier types of mineralization.

The Rude ore deposit was generated by predominantly NaCl ±} CaCl₂–H₂O solutions. Detrital quartz from stratiform mineralization was precipitated from solutions with salinities between 7 and 11 wt. % NaCl equ., homogenizing between 150 °C to 230 °C. Stratabound/siderite–polysulphide–barite–quartz vein type mineralization was derived from solutions with salinities between 5 and 19 wt. % NaCl equ., homogenizing between 80 °C and 160 °C, while late stage galena–barite veins were precipitated from solutions with salinities between 11 and 16 wt. % NaCl equ., homogenizing between 100 °C to 140 °C. Fluid inclusion bulk leachate chemistry recorded Na+>Mg2+>K+>Ca2+>Li+ and Cl–>SO₄ 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 ‰, 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 precursor? 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–Transdanubian Zone and the Gemerides, and southeastward to the Hellenide–Albanides.

Keywords

Rude siderite–polysulphide–barite–haematite deposit; Early intracontinental rifting; SEDEX; Feeder zone; Evaporites; Shock quartz; Planar deformation feature; PDFs; Zagorje–Mid–Transdanubian zone; Internal Dinarides

Hrčak ID:

56934

URI

https://hrcak.srce.hr/56934

Publication date:

27.2.2010.

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