REE and Th minerals in the metasandstones of the Udokan basin (Russia)
- 28 June 2022
- journal article
- Published by South Urals Federal Research Center for Mineralogy and Geoecology of the Urals Branch of the RAS
Abstract
Based on ICP-MS, optical and electron microscopy, and electron back-scatter diffraction data, the paper considers the distribution and mode of occurrence of REE and Th in metasandstones of the Lower Proterozoic Sakukan Formation, which host mineralization of the Udokan and Unkur copper sandstone deposits. The REE and Th contents increase in the layers enriched in iron oxides and minerals of natural heavy concentrate relatively to the background metasandstones. Detrital allanite is the major REE mineral, which occurs in layers enriched in iron oxides together with authigenic allanite, monazite, and unidentifed Ca and REE carbonates. Thorium is concentrated in an authigenic silicate (thorite or thorogummite), which contains a signifcant amount of Fe, Ca, Al, and Cu and microinclusions of Cu and Pb sulfdes and barite. The diagenetic formation of authigenic REE and Th minerals is suggested as a result of desorption of these elements from siliceous-ferruginous gel-like sediments formed in river deltas and the wave-cut zone of the Proterozoic Sea.Keywords
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