Krisztián Fintor

Microbial action formed Jurassic Mn-carbonate ore deposit in only a few hundred years (Úrkút, Hungary)

The Urkut (Hungary) manganese (Mn) ore, hosted by Jurassic black shale, was studied using high-resolution mineralogical, microtextural, and chemical methods. Two independent superimposed biostructures were identified consisting of rhythmic laminations that provide important proxies for paleoenvironments and duration of ore formation. Millimeter-scale laminae reflect a depositional series of Fe-rich biomats, mineralized microbially produced sedimentary structures. These biomats formed at the sediment-water interface under dysoxic and neutral pH conditions by enzymatic Fe 2+ oxidizing processes that may have developed on a daily to weekly growth cycle. The early diagenetic sedimentary ore is composed of Ca rhodochrosite, celadonite, and smectite, and also shows a 100-µm-scale element oscillation that produces Mn(Ca)-rich and Si(Fe clay)-rich microlaminae. This microlamination may reflect a 10 h to daily rhythmicity produced by the growth of microbial communities. If true, then the giant Urkut ore deposit may have formed over hundreds of years, rather than hundreds of thousands of years as previously thought.

Archaeometric investigation of the hoard from Bodrogolaszi, Hungary

Abstract The hoard from Bodrogolaszi is a very significant find, dating back to the 15th-16th centuries. Unfortunately only 73 coins have survived from the original 135. In our study we would like to present the site, the circumstances of finding the hoard, and also a short numismatic introduction to these coins. We used stereomicroscopy to investigate the surface of coins, searching for additional artificial interventions (breaking, cutting, and fillip). We discovered darker reddish brown spots on several coins. We applied Raman spectroscopy to determine the origin of the spots. The results revealed they are part of a lepidocrocitegoethite cover layer caused by exposure to the soil. XRF measurements were used to prove that the purity of the coins differs from historical data.

Characterization and 10Be content of iron carbonate concretions for genetic aspects – Weathering, desert varnish or burning: Rim effects in iron carbonate concretions

The research investigated three iron carbonate (siderite) sedimentary concretions from Nagykovácsi, Úri and Délegyháza, Hungary. To identify possible source rocks and effects of the glaze-like exposed surface of the concretions, we carried on comparative petrological, mineralogical, geochemical and isotopic studies. The samples were microbially mediated siderite concretions with embedded metamorphous and igneous mineral clasts, and had specific rim belts characterized by semi-concentric outer Fe-oxide layers, fluffy pyrite-rich outer belts and siderite inner parts. We investigated the cross section of the Fe-carbonate concretions by independent methodologies in order to identify their rim effects. Their surficial oxide layers showed evidence of degassing of the exposed surface caused most probably by elevated temperatures. The inner rim pyrite belt in the concretions excluded the possibility of a prolonged wet surface environment. Microtextural and mineralogical features did not support desert varnish formation. 10Be nuclide values of the Nagykovácsi and Uri concretions were far above the level of terrestrial in-situ cosmogenic nuclides, but they were consistent with the lowest levels for meteorites. Though the data were not conclusive to confirm any kind of known origin, they are contradictary, and open possibilities for a scenario of terrestrial meteorite origin.

Thermal metamorphism of the Mócs meteorite (L6) revealed by optical microscopy and BSE imaging

The Mocs chondrite was studied by optical microscopy, element mapping, as well as scanning electron microscope backscattered electron (SEM—BSE) imaging, in order to gain a better understanding of the thermal metamorphic as well as post-shock annealing evolution and the mineralogical signatures in this meteorite. The studied thin section of Mocs meteorite contains 26 chondrules with a variety of chondrule textures, which are characterized by a blurry rim. The chondrules mostly consist of pyroxene and olivine, whereas feldspars occur only in the recrystallized groundmass, chondrule mesostasis, and mineral melt inside and beyond the shock veins. It was found that the matrix was completely recrystallized. According to the scanning electron microscope and optical microscope observations mentioned above, it can be concluded that the Mocs chondrite is a 6.5 petrographic type.