Results of the complex analyses of the Gyűrűfű Rhyolite Formation in the Tisza Mega-unit (Hungary)

Szemerédi, Máté

doi:10.14232/phd.10580

Cited by 1 publication

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References 63 publications

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“…The iron content in the fresh granitic samples is around 3-5 wt% Fe 2 O 3tot , in correspondence with values found for granites of the whole Mórágy Formation [13]. The iron content of rhyolite samples is significantly lower, namely 3 wt% Fe 2 O 3tot is an upper limit similar to the values obtained on several other samples collected from this formation [16]. In contrast, the iron content of the BCF samples exceeds 2-3 times the values mentioned before, i.e., a definite accumulation process of iron can be deduced for BCF.…”

Section: Chemical Compositionssupporting

confidence: 86%

“…From the point of view of our subject, the emphasis is on the ferrous iron content in them; thus, hereinafter, the biotite group minerals will be referred to in general. Rock types of BCF source rocks (the Mórágy Metagranite Complex, the Baksa Metamorphic Complex and the Gy űr űf ű Formation) contain these minerals in various amounts [13][14][15][16][17][18][19]. Feldspar, the other primary component, usually does not contain appreciable amounts of iron.…”

Section: Introduction 1general Overviewmentioning

confidence: 99%

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Iron-Bearing Minerals in the Boda Claystone Formation: Correspondences with Stages of Evolution Revealed by Mössbauer Spectroscopy

Lázár,

Máthé,

Németh

et al. 2024

Minerals

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The Boda Claystone Formation (BCF) is an extended sedimentary sequence formed in a shallow-water salt lake under semi-arid to arid climatic conditions during the middle Permian period. The rock was formed predominantly from denuded and altered products of three primary felsic sources, the Mórágy Metagranite Complex, the Baksa Metamorphic Complex and the rhyolitic Gyűrűfű Formation, resulting in the recent dominant sheet silicate components, illite and chlorite. BCF has been considered a potential host rock for high-level nuclear waste, too. Thus, it has been characterized by several powerful methods so far (X-ray diffraction (XRD), transmission electron microscopy (TEM), etc.). 57Fe Mössbauer spectroscopy may provide a unique additional tool to study iron-bearing minerals. Iron is dominantly present in a ferrous form in minerals of the fresh parent rocks (in the biotite group and amphibole), and in a ferric oxide, hematite, in altered Gyűrűfű Formation. During transformations of biotite group minerals and amphibole, the partial release of ferrous iron or its conversion to ferric form takes place with the stabilization of recent illite and chlorite, while the original layered structure is still preserved. Mössbauer spectroscopy revealed the dominant presence of ferrous iron located in cis-M2 octahedral sites both in parent biotite group minerals and in the final illite, as well as chlorite in both stages. The proportion of ferrous iron in biotite group minerals was halved during the stages of evolution by conversion to ferric iron still in sheet silicate illite or by segregation into separate hematite inclusions. The transformation process of biotite group minerals and amphibole of the source rocks is connected only to the iron-bearing smaller fraction of sheet silicates in the BCF clay mineral assemblage. Determination of Fe2+/Fe3+ ratios in sheet silicates was also pertinent in two sections of BCF. Namely, in samples from the Gorica region, Fe3+ was dominant, siting in illite, whereas Fe2+ was also present in significant portions in chlorite in samples from the Western Mecsek Anticline. The interpretation is deduced in correspondence with results of extended XRD, and high-resolution TEM studies.

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Section: Chemical Compositionssupporting

confidence: 86%

Section: Introduction 1general Overviewmentioning

confidence: 99%