Rare Earth Elements in Mineral Deposits: Speciation in Hydrothermal Fluids and Partitioning in Calcite

Figure 5

Rare earth element fluid-calcite partitioning Model IIb at 1 kbar, showing the speciation of REE in a fluid in equilibrium with REE-bearing calcite as a function of temperature and salinity (0.5 and 20 wt.% NaCl). The starting fluid had a composition of 100 ppm REE, CO₂ of 0.1, and 50 g of calcite.

(a) 100 ppm Ce 0.5 wt.% NaCl

(b) 100 ppm Ce 20 wt.% NaCl

(c) 100 ppm Nd 0.5 wt.% NaCl

(d) 100 ppm Nd 20 wt.% NaCl

(e) 100 ppm Er 0.5 wt.% NaCl

(f) 100 ppm Er 20 wt.% NaCl