This is an implementation of the model presented in the paper A window in the course of alkaline magma differentiation conducive to immiscible REE-rich carbonatites, Geochimica et Cosmochimica Acta 282 (2020) 297-323.
https://doi.org/10.1016/j.gca.2020.04.008
This modelling predicts the REE concentrations of a carbonatite which may be immiscible at equilibrium with an alkaline magmatic rock, only from the silicate rock major elements and REE compositions. The parameterisation first calculates the Ca partition coefficient (DCaCL/SL ), then the REE partition coefficients (DREECL/SL), and finally the REE concentrations of the potential carbonatite.
The calculated REE concentrations can be normalised to chondrite (McDonough and Sun, 1995).
As an example, we calculate the REE compositions of the carbonatite which may be immiscible with a phono-tephrite dyke from the Lofdal magmatic suite in Namibia (Fig.7 in the paper). The phono-tephrite data are from Bodeving et al. (2017)
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| Normalisation to chondrites | Silicate melt major element concentration (wt%) | Silicate melt REE concentration (μg/g = ppm) | DcaCL/SL calculation | DREECL/SL calculation | Calculation of carbonatite REE concentrations (μg/g = ppm) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Graph | Tm | Pm | Dca | σ(Dca) | {{outputs[y].label}} | σ({{outputs[y].label}}) | Tm | σ(Tm) | {{outputs[y].label}} | σ({{outputs[y].label}}) | Pm | σ(Pm) | {{outputs[y].label}} | σ({{outputs[y].label}}) | {{outputs[y].label}} | σ({{outputs[y].label}}) | Tm | σ(Tm) | {{outputs[y].label}} | σ({{outputs[y].label}}) | Pm | σ(Pm) | {{outputs[y].label}} | σ({{outputs[y].label}}) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| {{inputs_show[x].object.value[key]}} | {{inputs_show[x].object.value[key]}} | ND | {{inputs_show[x].object.value[key]}} | ND | {{inputs_show[x].object.value[key]}} | {{outputs_show[y].object.value[key]}} | {{outputs_show[y].object.uncertainty[key]}} | {{outputs_show[y].object.value[key]}} | {{outputs_show[y].object.uncertainty[key]}} | ND | ND | {{outputs_show[y].object.value[key]}} | {{outputs_show[y].object.uncertainty[key]}} | ND | ND | {{outputs_show[y].object.value[key]}} | {{outputs_show[y].object.uncertainty[key]}} | {{outputs_show[y].object.value[key]}} | {{outputs_show[y].object.uncertainty[key]}} | ND | ND | {{outputs_show[y].object.value[key]}} | {{outputs_show[y].object.uncertainty[key]}} | ND | ND | {{outputs_show[y].object.value[key]}} | {{outputs_show[y].object.uncertainty[key]}} | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
