Original scientific paper
https://doi.org/10.17794/rgn.2018.3.7
FORMATION MECHANISMS OF FE-MN CONCRETIONS IN THE VIJENAC QUARRY, DINARIC OPHIOLITE ZONE
Srećko Bevandić
; Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb, Pierottijeva 6, 10 000 Zagreb, Croatia
Tomislav Brenko
; Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb, Pierottijeva 6, 10 000 Zagreb, Croatia
Elvir Babajić
orcid.org/0000-0002-2903-1826
; Faculty of Mining, Geology and Civil Engineering, University of Tuzla, Univerzitetska 2, 75 000 Tuzla, Bosnia and Herzegovina
Sibila Borojević Šoštarić
orcid.org/0000-0003-1861-2470
; Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb, Pierottijeva 6, 10 000 Zagreb, Croatia
Abstract
Vijenac quarry, near Tuzla in Bosnia-Herzegovina, is composed of carbonate rocks locally embedding tectonically disturbed siltite and sandstone with Mn-Fe concretions. The quarry itself represent a part of Dinaric overstep sequences (Pogari series) unconformably overlying ophiolite mélange and ophiolite trust-scheets. Petrographic, chemical and XRD analyses had shown that the concretions may be divided into two types: (i) Mn-rich concretions with ≈17% of Mn and compact texture and (ii) Mn-poor (≈8% of Mn) and porous texture. The amount of Ca, Mg, Fe and organic matter, as well as analysed microelements (Ni, Cr) in both concretion types are similar. According to petrographic and XRD analyses, concretions are composed of calcite, dolomite, hematite, todorkite and takenelite. Todorokite is characteristic for concretions formed by diagenetic growth. Petrographic study confirmed the development of concretions within three stages including two generations of calcite. The studied concretions are formed within consolidated sandstones inheriting their sedimentary textures - therefore a late diagenetic process is assumed.
Keywords
Fe-Mn concretions; diagenetic growth; Mn-minerals; chemical analysis; Dinaric Ophiolite Zone
Hrčak ID:
201001
URI
Publication date:
11.6.2018.
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