**Author details**

Petr Ptáček

extrapolation of high-temperature diffusion data of trace elements in apatite shows that these processes are inefficient at temperatures below 300°C, which cover the conditions of diage‐

The differing initial and boundary conditions imposed in three sets of diffusion experiments:

consequently resulting in different solutions to the diffusion equation. However, in all cases, the process can be described as one-dimensional, concentration-independent diffusion [141].

Apatite

600 1400 1200 1000

–18

**(a) (b)**

Sm - zircon

–20

–22

–24

8 10 12 6 8 10 12

T (°C)

Sm - apatite (I)

Sm - diopside REE - garnet REE Diffusion

> Nd - titanite Nd - YAG Nd - apatite (C) Ce - diopside Nd - calcite

Dy - diopside

800 600

Nd - garnet

1/T (×104/K) 1/T (×104/K)

**Fig. 17.** The summary of data diffusion for cations and anions in apatite (a) [142] and the diffusion of Sm and Nd for

A plot of diffusivities of various cations and anions in apatite is shown in **Fig. 17**(**a**). The diffusivities of Mn are similarto those of Sr and about an order of magnitude slowerthan those of Pb. On the other hand, the diffusion of Mn2+ in apatite is about two orders of magnitude faster than the diffusion of (trivalent) REE when coupled substitutions according to **Eqs. 4** and **5** are involved [141],[142]. The diffusion coefficients of Nd and Sm in various minerals and related oxides are plotted in **Fig. 17**(**b**). The diffusion of REE in apatite is relatively fast; when only simple REE exchange is involved, it is among the fastest in rock-forming minerals for which the data exist. Even when the chemical diffusion involving coupled exchange is considered, REE transport in apatite is considerably faster than the REE diffusion in other

log D (m2s–1)

netic alteration up to low-grade metamorphism [135],[141].

324 Apatites and their Synthetic Analogues - Synthesis, Structure, Properties and Applications

**2.** In-diffusion with powder sources experiment;

1200 1000 800

F-Cl-OH

T (°C)

Sm (watson et al., 1985)

REE - coupled diffusion Sm - simple REE exchange

Oxygen

Sr Pb Mn

**1.** Ion implantation;

**3.** Out-diffusion.

6

various minerals and oxides (a) [141].

accessory minerals [141].

–22

–20

U - NNO

U - air

–18 log D (m2sec–1)

–16

–14

Brno University of Technology, Czech Republic
