Genesis of secondary Mn-oxide ores in the Úrkút deposit, Hungary
✍ Scribed by Gy. Pantó; A. Demény; M. Polgári
- Publisher
- Springer
- Year
- 1996
- Tongue
- English
- Weight
- 399 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0026-4598
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✦ Synopsis
The Orkfit Basin of western Hungary is well known for its early Jurassic Mn-carbonate deposit that is related genetically to Jurassic black shale formation. This carbonate deposit has undergone multistage oxidation during the Cretaceous that produced secondary Mnoxides. Among the geochemical characteristics that distinguish the host sedimentary rocks and Mn-carbonates from the Mn-oxides is an extreme enrichment in Sr (up to 1%) without an observable independent Sr-phase. This enrichment indicates a special process of formation. The 6180 values of these Mn-oxide ores fall between 1.5 and 5.5%o (VSMOW) showing a slight bimodal distribution. This isotopic variability is interpreted as a product of superposing effects of the interaction of surficial and deepseated magmatic fluids. The •18OMnO2 values (from 1.5 to 5.5%o), the assumed 618Owa,er values and formation temperatures fit well with the MnO2-water fractionation curve based on the data of Yeh et al. (1985) and Hoers et al. (1987).