Formation Mechanisms of Fe-Mn Concretions in the Vijenac Quarry, Dinaric Ophiolite Zone

Abstract

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 con rmed 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.

Characteristics of soils and the soil cover in the Kostomuksha State Nature Reserve, Russia

“…They can influence the redistribution of fine fractions and make the local increase in moisture of sites. A similar formation of compact miner-alised layers has been observed also in soils of other regions, with an optimal combination of hydrothermal conditions, organic matter availability, and a high iron content (Zaidelman & Nikiforova, 2001;Vodyanitskiy, 2003;Charzynski et al, 2005;Gasparatos, 2007;Antsiferova, 2014;Bevandić et al, 2018).…”