Stratiform manganese deposit which is bound to the metamorphosed Early Paleozoic black shale of the Gemericum Superunit. Sedimentary-diagenetic accumulation was overlapped by association of the metamorphic minerals due to the Hercynian metamorphism.

Two lenticular ore bodies of Mn bearing skarn, closing a segment of Fe skarn, are located at the northern side of the Čučma village, about 6 km north-east of Rožňava town in the Gemeric unit of the Internal (Inner) Western Carpathians. The Fe and Mn skarns formed during three metamorphic stages. The first stage gradually replaced the former Silurian limestones lenses into of Mn-rich calcite, kutnahorite, rhodochrosite, Mn-rich siderite, fluorapatite, tourmaline, phengitic muscovite, Mn-rich chlorite. Rare pyrite, molybdenite, galena, chalcopyrite, pyrite, sphalerite and Ag-rich tetrahedrite occur there as well. Near the contact of former limestone with metapelite, the maghemite dominates over assemblage of Mn-rich carbonates to form Fe skarn. The replacement of limestones as well as the Fe skarn metasomatic origin took place in the chlorite-apatite zone at a temperature range 520–540 °C, where the maghemite and Mn-rich carbonates were generated by the fluid phase, released during anatectic melting of the upper crust during the older Permian metamorphic-magmatic- -hydrothermal cycle (MMH of 281–273 Ma). In the second prograde metamorphic stage, the first-stage minerals were continuously overheated in amphibolite facies (600–650 °C; ~ 4 Kbar), forming following minerals: spessartine, alleghanyite, pyrophanite, manganosite, kempite, jacobsite, iwakiite, hausmannite, tephroite, Ti-rich tephroite, knebelite, rhodonite-1, rhodonite-2, cummingtonite, grunerite and allanite. This study brings an important finding of a new Ti4+ = Si4+ substitution in the olivine group, where in the Ti-rich tephroite the Si content was replaced by Ti up to 0.159 apfu. Grains formation of Ti tephroite are controlled by the sector zoning, having different content of Ti in each sector. In the final stage of skarns formation, the unstable minerals of previous two stages were replaced by the Si, Ba, H2 S and H2 O bearing fluid phase to form Ca-rich spessartine, bementite, pyrochroite, quartz, pyrolusite, baryte, chlorite and stilpnomelane during the retrograde stilpnomelane-chlorite zone metamorphism at 300–370 °C. This mineral assemblage was gradually formed in retrograde metamorphic path with decreasing temperature from the amphibolite facies to the stilpnomelane-chlorite zone. The prograde and retrograde metamorphic stages produced a group of Mn bearing garnets, humites, oxides, halides, spinels, olivines, pyroxenoides, amphiboles and they on the former Fe skarn formed a younger and fine to medium-grained Mn bearing part of the skarn. This metamorphic part of Mn skarn has the positive Eu anomaly and was formed by the fluid phase influenced by the primitive mantle in younger MMH cycle of the Permian, dated to 269–251 Ma.

Old Hungarian name is Feketebánya or Roszty.

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References