REE Tetrad Effect as a Powerful Indicator of Formation Conditions of Karst Bauxites: A Case Study of the Shahindezh Deposit, NW Iran

Abstract

Study of the concentration of major, trace, and rare earth elements (REE) in the Shahindezh karst bauxite deposit, northwestern Iran clarifies the relationship of the tetrad effect with geochemical parameters in the bauxite ores. The existence of irregular curves in the chondrite‐normalized REE patterns as well as non‐CHARAC behavior of geochemically isovalent pairs (Y/Ho) are related to the tetrad effect. The meaningful positive correlation between the sizes of the calculated T3 tetrad effect and some geochemical factors such as Y/Ho, ΣREE, La/Y, (La/Yb)N, and (LREE/HREE)N as well as some major oxides‐based parameters like Al2O3 + LOI/SiO2 + Fe2O3, Al2O3/Fe2O3, Al2O3 + LOI, IOL, and SiO2 + Fe2O3 indicate that the studied bauxite horizon was likely deposited by different (acidic and/or alkalic) solutions at different stages. The lower part of the studied horizon with a thickness of ∼4.7 m displays alkali characteristics whereas the upper parts of the horizon with a thickness of ∼5.3 m are characterized by more acidic conditions. These results are fully supported by the co‐occurrence of convex‐concave tetrad effect curves in the chondrite‐normalized REE patterns. Therefore, the tetrad effect phenomenon used in this study has proved to be a good and reliable geochemical proxy to assess the conditions of the depositional environment in the Shahindezh bauxite ores.

Iron Loss During Continental Weathering in the Early Carboniferous Period Recorded by Karst Bauxites

“…The Jiujialu Formation, which shows parallel unconformities with the overlying lower Carboniferous limestone/clay rock and the underlying Cambrian or Ordovician dolomite strata, usually comprises a 1–20 m thick bauxite bed (bauxite ore/clay rock) and an underlying 0–6 m thick iron bed (iron ore/iron‐rich clay) (Figure 2). This typical “iron‐bauxite” structure is widespread worldwide, such as the Ghiona bauxite deposit in Greece (Kalaitzidis et al., 2010), the Nurra bauxite deposit in Italy (Mameli et al., 2007), the Kanisheeteh, Kanirash, Shahindezh, Qopi, Darzi‐Vali; Soleiman‐Kandi, Kani‐Zarrineh bauxite deposits in Iran (Abedini, Habibi Mehr, et al., 2019; Abedini et al., 2019a, 2019b; Abedini et al., 2022a, 2022b; Calagari & Abedini, 2007; Khosravi et al., 2017, 2021), and most bauxite deposits in China (e.g., Ling et al., 2017; X. Liu et al., 2017; Yu et al., 2019; Z. Zhang et al., 2013). In central Guizhou, the thickness of the Jiujialu Formation is controlled by the paleo‐karst unconformities, that is, the thickness above the karst depression is greater than that above the highland (Figure 3).…”

Gadolinium-dominant monazite and xenotime: Selective hydrothermal enrichment of middle REE during low-temperature alteration of uraninite, brannerite, and fluorapatite (the Zimná Voda REE-U-Au quartz vein, Western Carpathians, Slovakia)

“…There are only two belong to very rare minerals occurring in some granitic pegmatites and metamorphichydrothermal lithologies (Demartin et al 1991a;Förster and Rhede 1995;Förster 1998b;Buck et al 1999;Massau et al 2000;Repina 2011Repina , 2014Franz et al 2015). Despite having a generally coherent behavior, selective REE mobilization and fractionation in aqueous systems is quite common and has been reported previously from different geochemical environments (e.g., Seredin 1996;Morgan et al 2012;Lee et al 2013;Franz et al 2015;Migdisov et al 2019;Ondrejka et al 2018;Abedini et al 2019;Anenburg et al 2020b).…”

Provenance and Tectonic Evolution of Bauxite Deposits in the Tethys: Perspective From Random Forest and Logistic Regression Analyses

“…This suggests that climate may not be a key factor affecting the TiO 2 content (Figure 5b). Some bauxite deposits formed between 30° and 40° latitude, such as Amir‐Abad, Kani Zarrineh, Sahindezh, Kanisheeteh, Soleiman Kandi bauxites in northwestern Iran (Abedini & Khosravi, 2020; Abedini, Mongelli, & Khosravi, 2022; Abedini et al., 2019a, 2019b, 2021) and Siahrudbar bauxite in Alborz mountains, Iran (Kiaeshkevarian et al., 2020), Languedoc and Provence bauxite in southern France (Mondillo et al., 2019). This is mainly due to greenhouse conditions in the Mesozoic.…”