Nodular monazite from placers in the Kular Ridge (Arctic Siberia, Russia): Composition and age

Nodular monazite occurs in metamorphic rocks worldwide and has zonal REE patterns. This paper focuses on the composition of nodular monazite hosted by Permian black shales of the Kular Ridge in the Kular-Nera terrane. This monazite variety (called kularite in the Russian literature) reaches commerci...

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Published inRussian geology and geophysics Vol. 59; no. 10; pp. 1330 - 1347
Main Authors Lazareva, E.V., Zhmodik, S.M., Prokopiev, A.V., Karmanov, N.S., Sergeenko, A.I.
Format Journal Article
LanguageEnglish
Published Elsevier B.V 01.10.2018
Allerton Press
Subjects
Arctic region
Asia
black shale
clastic rocks
Commonwealth of Independent States
Economic geology
geochemical methods
Geochemistry
Khatanga River
Kular Range
Kular Ridge
metal ores
metamorphic rocks
mineral composition
monazite
niobium ores
nodular monazite (kularite)
Paleozoic
Permian
phosphates
placers
rare earth deposits
rare-earth elements
rock, sediment, soil
Russian Arctic
Russian Federation
sedimentary rocks
Siberia
Tomtor Deposit
trace elements
nodular monazite (kularite)
rare-earth elements
Kular Ridge
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Summary:Nodular monazite occurs in metamorphic rocks worldwide and has zonal REE patterns. This paper focuses on the composition of nodular monazite hosted by Permian black shales of the Kular Ridge in the Kular-Nera terrane. This monazite variety (called kularite in the Russian literature) reaches commercial amounts in placers of the area. The contents of Ce, Nd, and La in the analyzed monazite nodules show correlations at Ce/Nd = 14.39La + 0.0919 (in apfu) and Ce/Nd = 0.2318La + 0.1135 (in wt.%) and vary regularly from core to rim. All monazite compositions fall on this trend, but specific grains may plot in its different parts. Thermodynamic calculations indicate that monazite forms via an intermediate precursor (LnPO4·2H2O). The Ce:La:Nd changes in different grains record Eh-pH variations during nucleation and a gradual temperature increase during subsequent growth. The Ce:La:Nd ratio changes partly in grain rims as a result of oxidative dissolution. Judging by the tectonic setting, REE came to the Kular-Nera rocks from the weathered Tomtor Nb-REE deposit, being transported by the Paleo-Khatanga River with monazite nanoparticles bound to the surface of clay minerals.
ISSN:1068-7971
1878-030X
DOI:10.1016/j.rgg.2018.09.010