Rare Earth Elements Enrichment in the Upper Eocene Tošići-Dujići Bauxite Deposit, Croatia, and Relation to REE Mineralogy, Parent Material and Weathering Pattern

Abstract

Tošići-Dujići bauxite deposit, situated in Dalmatian inlands, Croatia, contains minor remaining bauxite reserves. The deposit lies on Lower Eocene foraminiferal limestone and is covered by Upper Eocene Promina sediments. Bauxite samples were analyzed for textural, mineralogical, and geochemical features in order to determine absolute REE abundances and their relation to mineralogy, as well as to devise the origin of REE enrichment and to trace weathering and bauxitization paths of the parent material. The samples show total REE abundances up to 3500 mg/kg with significant HREE enrichment in some cases. All samples are gibbsitic with hematite and anatase as major phases. Kaolinite occurs in most of the samples, and goethite, böhmite, and nordstrandite are minor phases. Monazite-(Ce) and xenotime-(Y) were identified as detrital REE minerals as well as authigenic florencite-(Ce). In the REE most abundant sample, REE are most likely bound to Fe- and Ti-oxide phases as suggested by correlation analysis. Chemical weathering proxies show intensive weathering. Geochemical and textural data imply that the REE enrichment is influenced by intensive weathering (CIA 97.87–99.26) of detrital material, and also by possible deposition/redeposition of residual material potentially derived and mobilized from various sedimentary rocks of the area.

Geochemical records in subaerial exposure environments in Croatia using discriminant function analysis of bauxite data

“…Lately, bauxite research has particularly focused on the potential for REE and associated critical metals (e.g. Radusinović et al, 2016;Papadopoulos et al, 2019;Radusinović and Papadopoulos, 2021;Mondillo et al, 2019;Mongelli et al, 2017;Tomašić et al, 2021;Yang et al, 2019;and others). Widely identified as regional markers of global events, bauxites occurred in distinctive periods in the geological history with warm and humid climates conjoined with tectonically controlled subaerial exposure of the carbonate platform (D'Argenio and Mindszenty, 1992;D'Argenio and Mindszenty, 1995).…”

A time-space window between Eocene karst bauxite genesis and the first molasse deposition in the Dinaric Foreland Basin in the North Dalmatia, Croatia

“…The trace element composition (Maksimović, 1968;Maksimović,1976;Maksimović and Pantó, 1978;Deady et al, 2016;Radusinović and Papadopoulos, 2021;Tomašić et al, 2021) and content of Zr, Ga, and Cr (Özlü, 1983;Ilijanić et al, 2023) of the Frontiers in Earth Science frontiersin.org 16 bauxites in the Mediterranean belt show no genetic relationship with the calcareous basement. REEs become concentrated in bauxite deposits either by adsorption on the surface of clay-size constituents (Estrade et al, 2019) or by authigenic REE-bearing minerals crystallised during bauxitisation (Deady et al, 2014).…”