Geochemical characteristics of Triassic and Cretaceous phosphorite horizons from the Transdanubian Mountain Range (western Hungary): Genetic implications

Zsuzsa Molnár, Gabriella B. Kiss, István Dunkl, György Czuppon, Federica Zaccarini, I. Dódony

Research output: Contribution to journalArticle

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Abstract

The carbonate-dominated Mesozoic sequence of the Transdanubian Mountain Range contains Triassic, uranium-enriched phosphorite layers and Cretaceous, REE-enriched nodular phosphorite. Detailed investigation of these deposits may have an economic benefit because of their large U and REE contents. The dominant minerals in the Triassic phosphorite are carbonate-bearing fluorapatite (CFA) and calcite. According to the electron-probe microanalysis (EPMA) the U is mainly associated with the CFA crystals. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) measurement shows that CFA contains 137-612 ppm U and 113-261 ppm total REE + Y. The LA-ICP-MS U-Pb age of the uppermost phosphorite horizon is 237 ± 11 Ma, which conforms with the stratigraphic age of the host limestone. The Cretaceous nodular phosphorite occurs on the base of an Aptian crinoid-bearing limestone mostly in the form of encrustations around bio- and silicic-clasts, but the clasts also contain phosphorite. The main minerals in these crusts are CFA, calcite, quartz, glauconite and Fe-oxide-hydroxides. Based on EPMA the REE enrichment is related to CFA and LA-ICP-MS measurements show that it contains 748-2953 ppm total REE + Y. The redox-sensitive proxies and the shape of NASC normalized REE patterns indicate that both phosphorites formed in anoxic environments. There are significant differences between these deposits such as appearance, rock-forming minerals, and U and REE contents which indicate differences in their sedimentary environments. The present results suggest that the Triassic phosphorite was formed by inorganic precipitation in a reducing environment close to sea-mounts. The Cretaceous occurrence resulted from a concentric growth mechanism in cold, ascending seawater at the continental margin environment during the anoxic Selli Event (OAE 1a) and/or Paquier Episode (OAE 1b). The critical raw material contents were derived from other sources.

Original languageEnglish
Pages (from-to)S147-S171
JournalMineralogical Magazine
Volume82
Issue numberS1
DOIs
Publication statusPublished - May 1 2018

Fingerprint

Bearings (structural)
phosphorite
Carbonates
Triassic
fluorapatite
rare earth element
Cretaceous
Calcium Carbonate
carbonate
Inductively coupled plasma mass spectrometry
Laser ablation
ablation
Minerals
mass spectrometry
laser
Electron probe microanalysis
plasma
electron probe analysis
clast
mineral

Keywords

  • carbonate-bearing fluorapatite
  • phosphorite
  • Transdanubian Mountain Range
  • U and REE enrichment

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Geochemical characteristics of Triassic and Cretaceous phosphorite horizons from the Transdanubian Mountain Range (western Hungary) : Genetic implications. / Molnár, Zsuzsa; Kiss, Gabriella B.; Dunkl, István; Czuppon, György; Zaccarini, Federica; Dódony, I.

In: Mineralogical Magazine, Vol. 82, No. S1, 01.05.2018, p. S147-S171.

Research output: Contribution to journalArticle

Molnár, Zsuzsa ; Kiss, Gabriella B. ; Dunkl, István ; Czuppon, György ; Zaccarini, Federica ; Dódony, I. / Geochemical characteristics of Triassic and Cretaceous phosphorite horizons from the Transdanubian Mountain Range (western Hungary) : Genetic implications. In: Mineralogical Magazine. 2018 ; Vol. 82, No. S1. pp. S147-S171.
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