Formation of authigenic monazite-(Ce) to monazite-(Nd) from Upper Carboniferous graywackes of the Drahany Upland: Roles of the chemical composition of host rock and burial temperature

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Authors	ČOPJAKOVÁ Renata NOVÁK Milan FRANCŮ Eva
Year of publication	2011
Type	Article in Periodical
Magazine / Source	Lithos
MU Faculty or unit	Faculty of Science
Citation
Field	Geology and mineralogy
Keywords	Authigenic monazite;Diagenesis;Very-low grade metamorphism;Graywackes;Lower Carboniferous Culm basin;Bohemian Massif
Description	Irregular aggregates of monazite-(Ce) to monazite-(Nd)have been found in graywackes from the Protivanov Formation, Drahany Upland, Czech Republic. Textural evidences suggest that they are of authigenic origin and grew during very low-grade metamorphism at a maximum temperature ~200–300C in relation to a deep burial. Authigenic monazite appears to form only in Ca-poor rocks. In Ca-rich graywackes, which underwent the same low-temperature metamorphic overprint, authigenic synchysite-(Ce) or parisite-(Ce) are common instead. Authigenic monazite shows low concentrations of Th, U, Ca, Y+HREE, and a low Eu anomaly. Zoning pattern suggests an evolution in fluid chemistry during diagenesis/very low-grade metamorphism or it relates to different solubility of the individual REE-phosphates. The major source of REEs are detrital minerals mainly monazite. Other minor sources of REEs probably include Fe-oxide/hydroxide and/or clay minerals, which could have contributed to the Nd+MREE-rich cores.
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