REEs geochemical characteristics of lower Cambrian phosphatic rocks in the Gorgan-Rasht Zone, northern Iran: Implications for diagenetic effects and depositional conditions

Assessment of the Effect of Organic Matter on Rare Earth Elements and Yttrium Using the Zhijin Early Cambrian Phosphorite as an Example

“…This could be supported by the Post-Archean Australian Shale (PAAS)-normalized REY pattern showing HREE depletion relative to MREE in sedimentary apatite, which is similar to that of organic matter [24][25][26][27]. Although the sum of REY (∑REY) exhibits a positive correlation with TOC in phosphorites in northern Iran, the ∑REY only varies from 87.9 to 292 ppm [28]. In contrast, phosphorites were enriched with higher REY concentrations (>500 ppm) in the Enoch Valley Mine, United States, and they showed no correlation between TOC and ∑REY [29].…”

“…However, it is doubtful that the ∑REY in marine phosphorites can reach the REY concentrations of the Zhijin phosphorites only by diagenesis. For example, the ∑REY of lower Cambrian Meishucun and Soltanieh phosphorites under the influence of diagenesis is typically less than 500 ppm and 250 ppm, respectively [28,37]. Furthermore, there are no obvious δ 18 O carb differences between the Zhijin samples with an ∑REY of below 1000 ppm and those with an ∑REY of above 1000 ppm (Figure 5b).…”

“…Compared with other REY, the removal efficiency of Y from seawater is also relatively low [68,69]. Because of these phenomena, seawater has a higher Y/Ho ratio than continental crust [68,69], with seawater and terrestrial sources having Y/Ho ratios of ~60 and ~28, respectively [28]. Meanwhile, the influence of terrestrial sources can be tested using immobile elements (e.g., Th, Sc, and Zr) [70].…”

“…Minerals 2022, 12, x FOR PEER REVIEW 16 of 24 continental crust [68,69], with seawater and terrestrial sources having Y/Ho ratios of ~60 and ~28, respectively [28]. Meanwhile, the influence of terrestrial sources can be tested using immobile elements (e.g., Th, Sc, and Zr) [70].…”

TiO2–Zr–Th–Y–rare‐earth elements ore deposit in unconsolidated fine‐grained sediments from Tongo Gandima in the Bétaré Oya Gold district, Eastern Cameroon

“…REE in weathering crust are predominantly associated with residual magmatic pyrochlore, apatite or to secondary phosphate minerals of the crandallite group, monazite, plumbo-gummite, rhabdophane, and/or iron hydroxides (Morteani & Preinfalk, 1993). High REE contents (up to 42 wt% REE oxides) were also described in laterites developed on carbonatites in the Mt Weld deposit in western Australia; REE are mainly incorporated in the structure of secondary phosphate minerals (Abedini & Calagari, 2017;Lottermoser, 1991;Sengupta & van Gosen, 2016).…”