FORMATION MECHANISMS OF FE-MN CONCRETIONS IN THE VIJENAC QUARRY, DINARIC OPHIOLITE ZONE

• Published in: Rudarsko-geološko-naftni zbornik Vol. 33; no. 3; pp. 63 - 74
• Main Authors: Bevandić, Srećko, Brenko, Tomislav, Babajić, Elvir, Borojević Šoštarić, Sibila
• Format: Journal Article
• Language: English
• Published: Zagreb University of Zagreb 01.01.2018
• Subjects: Calcite; Calcium; Carbonate rocks; chemical analysis; Chromium; Concretions; diagenetic growth; Dinaric Ophiolite Zone; Dolomite; Embedding; Fe-Mn concretions; Geology; Hematite; Iron; Limestone; Magnesium; Manganese; Metamorphic rocks; Mineralogy; Minerals; Mn-minerals; Nickel; Organic chemistry; Quarries; Sandstone; Sediments; Selenium; Spectrum analysis; Studies; Texture; Bosnia-Hercegovina
• ISSN: 0353-4529; 1849-0409
• DOI: 10.17794/rgn.2018.3.7

The Vijenac limestone quarry, near Tuzla in Bosnia and Herzegovina, is composed of carbonate rocks locally embedding tectonically disturbed siltite and sandstone with Fe-Mn concretions. The quarry itself represents a part of Dinaric overstep sequences (the Pogari Formation) unconformably overlying ophiolite mélange and ophiolite trust-scheets. Petrographic, chemical and mineralogical analyses had shown that the concretions may be divided into two types: (i) Mn-rich concretions with ≈ 17 wt.% of Mn and compact texture and (ii) Mn-poor with ≈ 8 wt.% of Mn and porous texture. The amount of Ca, Fe and Mg in both concretion types are similar. Nickel and Cr positively correlate with Fe and Mn, respectively. According to petrographic and mineralogical analyses, concretions are composed of calcite, dolomite, hematite, todorokite and takanelite. Petrographic study confirmed the development of concretions within three stages including two generations of calcite. Studied concretions are formed within consolidated sandstones inheriting their sedimentary textures - therefore a late diagenetic process is assumed.