REE Normalisation & Spider Plot
Normalise a rare-earth-element assay to a named reference (CI chondrite, McDonough & Sun 1995), plot the log-scale spider pattern, and read Eu/Ce anomalies and the (La/Yb)ₙ slope.
REE assay (ppm)
McDonough, W.F. & Sun, S.-s. (1995) The composition of the Earth. Chemical Geology 120, 223–253.
Chondrite-normalised pattern
Runs entirely in your browser. Your assay data is not uploaded or stored by Zerdly.
- Enter at least two REE concentrations.
Assumptions & basis
- Reference: CI chondrite (McDonough & Sun, 1995) (user)
- Citation: McDonough, W.F. & Sun, S.-s. (1995) The composition of the Earth. Chemical Geology 120, 223–253. (derived)
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the REE concentrations (La–Lu) in ppm and choose the normalisation reference.
- Read the log-scale spider pattern and the normalised value for each element.
- Check the Eu/Eu*, Ce/Ce* anomalies and the (La/Yb)ₙ light-to-heavy slope.
How it works
Each element is divided by the same element in the chosen reference: normalisedᵢ = sampleᵢ / referenceᵢ. Plotting these on a logarithmic y-axis against atomic number gives the familiar spider pattern, where a smooth trend reflects the reference-relative enrichment or depletion. The Eu anomaly Eu/Eu* = Euₙ / √(Smₙ · Gdₙ) compares measured Eu to the value interpolated from its neighbours; below 1 is a negative (feldspar) anomaly. Ce/Ce* is the analogous La–Pr interpolation.
Reference compositions differ by publication and reservoir, so the tool never uses an unlabeled 'chondrite'. The chosen reference and its citation are shown beside the plot, and each reference is stored as versioned static data — here CI chondrite from McDonough & Sun (1995).
Worked example
A light-REE-enriched pattern. A sample with La 30, Yb 1.9 ppm normalised to CI chondrite gives Laₙ ≈ 127 and Ybₙ ≈ 11.8, a (La/Yb)ₙ of about 10.7 — a steep, light-REE-enriched pattern typical of many crustal rocks.
Common mistakes
- Comparing patterns normalised to different references.
- Reading anomalies off raw concentrations instead of normalised values.
- Plotting on a linear rather than logarithmic scale.
Frequently asked questions
Why plot on a log scale?
REE concentrations span orders of magnitude and the light REE are far more abundant than the heavy REE. A log y-axis makes the normalised pattern and its slope readable.
What is Eu/Eu*?
The measured, normalised Eu divided by the value interpolated from its neighbours (√(Smₙ·Gdₙ)). Below 1 is a negative Eu anomaly, commonly linked to feldspar fractionation.
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Cite this tool
Zerdly. (2026). REE Normalisation & Spider Plot. Retrieved from https://www.zerdly.com/tools/ree-normalization-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.