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East Carpathian Manganese Deposits

Romania

Main commodities: Mn
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The manganese deposits of the East Carpathians in Romania are hosted by the Tulghes Group, a Cambrian-Ordovician island arc complex, subsequently metamorphosed to greenschist facies during the Silurian.

The host Tulghes Group is composed of sericite-chlorite schists, metarhyolites, quartzites, metagreywackes, limestones and greenschists. It is overlain above a major thrust by a Neoproterozoic succession of pelitic gneisses, mica schists, orthogneisses, amphibolites and granites, and is in turn thrust over a Neoproterozoic pile of metadacite lavas and tuffs, metagranodiorites and mica schists that in turn overlie older Neoproeterozoic mica schist, sillimanite-bearing pelitic gneiss, dolomites, limestones, amphibolites and quartzites. These sequences are sheared by Middle Cretaceous thrusts and are overlain by Cretaceous flysch to the east and a Neogene volcanic arc to the west.

The deposits consist of ferromanganese carbonate­silicate orebodies (Fe-rhodochrosite, Mn-amphibole, spessartine, stilpnomelane, rhodonite, pyroxmangite and tephroite), occurring within larger and lower-grade mineralized areas. The manganese carbonates are spatially asscociated with organic matter, although the ore is devoid of organic matter.

Two types of ore are distinguished, namely:
i). Banded ore - millimetre thick stripes corresponding to the different components, comprising pink to grey carbonate, green to white amphibole, brown to yellow spessartine ±stilpnomelane, white to colourless quartz and black oxides.
ii). Massive ore - a grey or pink compact rock composed of 70-90% carbonate, with minor quartz, silicates and oxides. Garnet, amphibole, tephroite, rhodonite and pyroxmangite are the most common silicates.
The two ore types can occur together in the same orebody which may vary from a few tens of centimetres to several metres in thickness. Pyrite, pyrrhotite, sphalerite, chalcopyrite and galena occur mainly in the massive ore.

The formation of the ore has been interpreted to have involved the development of silicate minerals by decarbonation reactions, followed by the extensive replacement of silicate phases by Mn carbonate and, locally, by iron sulphide, as a result of reducing fluids circulation.

These deposits have been mined since the 18th century, with about 10 Mt of ore having been removed to date. The ore is based on a 15% Mn cut-off. For detail consult the reference(s) listed below.

The most recent source geological information used to prepare this summary was dated: 2004.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.


  References & Additional Information
   Selected References:
Munteanu M, Marincea S, Kasper H U, Zak K, Alexe V, Trandafir V, Saptefrati G, Mihalache A  2004 - Black chert-hosted manganese deposits from the Bistritei Mountains, Eastern Carpathians (Romania): petrography, genesis and metamorphic evolution: in    Ore Geology Reviews   v24 pp 45-65


Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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