Original scientific paper

Mn-crust todorokite mineralization on SW backshore Cretaceous limestones from the island of Dugi Otok (Central Adriatic, Croatia)

Boško LUGOVIĆ ; Faculty of Mining, Geology and Petrol Engineering, University of Zagreb, Pierottijeva 6, HR-10000 Zagreb, Croatia
Branimir ŠEGVIĆ ; Faculty of Mining, Geology and Petrol Engineering, University of Zagreb, Pierottijeva 6, HR-10000 Zagreb, Croatia
Tanja ŠEGVIĆ ; Institute of Oceanography and Fisheries, P.O.Box 500, HR-21000 Split, Croatia

Abstract

The southwest shore of the island of Dugi Otok is characterized by the unusual sample occurrence of Mn-hydrated oxide mineralization in the form of botryoidally and globular, fine-laminated concentric aggregates, crusting the Upper Cretaceous backshore limestones. The mineralization consists mainly of Fe impoverished 10-Å tecto-manganate todorokite (enriched in Mg and transition metals) accompanied by accessory MnO·OH. Todorokite chemical composition is typical of a hydrogenous origin in an oxic shallow marine environment. According to our model, Mn has been recurrently leached and mobilized from the Late Pleistocene sea floor sediments located around 50 nautical miles south of Dugi Otok. We propose a link between the Mn-geochemical anomaly of these sediments and the alteration of distinct, spatial close pre-Holocene tephra, dispersed over the entire recent Adriatic area.

Keywords

10-Å manganates; todorokite; hydrogenous origin; pre-Holocene tephra; Dugi Otok island; Adriatic

Hrčak ID:

26477

URI

https://hrcak.srce.hr/26477

Publication date:

1.7.2008.

Article data in other languages: croatian

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