Rare earth mineral diversity controlled by REE pattern shapes

Abstract

The line connecting rare earth elements (REE) in chondrite-normalised plots can be represented by a smooth polynomial function using λ shape coefficients as described by O'Neill (2016). In this study, computationally generated λ combinations are used to construct artificial chondrite-normalised REE patterns that encompass most REE patterns likely to occur in natural materials. The dominant REE per pattern is identified, which would lead to its inclusion in a hypothetical mineral suffix, had this mineral contained essential REE. Furthermore, negative Ce and Y anomalies, common in natural minerals, are considered in the modelled REE patterns to investigate the effect of their exclusion on the relative abundance of the remainder REE. The dominant REE in a mineral results from distinct pattern shapes requiring specific fractionation processes, thus providing information on its genesis. Minerals dominated by heavy lanthanides are rare or non-existent, even though the present analysis shows that REE patterns dominated by Gd, Dy, Er and Yb are geologically plausible. This discrepancy is caused by the inclusion of Y, which dominates heavy REE budgets, in mineral name suffixes. The focus on Y obscures heavy lanthanide mineral diversity and can lead to various fractionation processes to be overlooked. Samarium dominant minerals are known, even though deemed unlikely by the computational model, suggesting additional fractionation processes that are not well described by λ shape coefficients. Positive Eu anomalies only need to be moderate in minerals depleted in the light REE for Eu to be the dominant REE, thus identifying candidate rocks in which the first Eu dominant mineral might be found. Here, I present an online tool, called ALambdaR that allows interactive control of λ shape coefficients and visualisation of resulting REE patterns.

Revisiting the provenance of the Stonehenge bluestones: Refining the provenance of the Group 2 non-spotted dolerites using rare earth element geochemistry

“…REE ratios and values and REE maximum and minimum 1 and 2 values for dolerites Groups 1, 2 and 3 along with that for the unclassified sample SH44. 1 2 values calculated using the web application of Anenburg (2020)…”

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)

“…REE patterns were fitted, and tetrad effect were calculated using BlambdaR/ AlambdaR method (Anenburg 2020;Anenburg and Williams 2022). 1 and Supplementary Table 3).…”

From microanalysis to supercontinents: Insights from the Rio Apa Terrane into the Mesoproterozoic SW Amazonian Craton evolution during Rodinia assembly

“…These are shape coefficients that describe the chondrite‐normalized patterns with λ 0 describing the average chondrite‐normalized REE abundances, whereas λ 1 and λ 2 describing the linear slope and the quadratic curvature, respectively (O'Neill, 2016). The lambda coefficients were calculated with the online BLambaR calculator (Anenburg, 2020) (https://lambdar.rses.anu.edu.au/blambdar/). All trace element data were normalized to the chondrite reference values from McDonough and Sun (1995).…”