Inhaltsbereich
Phosphate and silicate minerals as monitors of geodynamic processes
Experiments involving phosphate and silicate minerals cover a wide range of minerals and fluid compositions. Most of these experiments have their origins and inspiration from natural processes involving metasomatically-induced partial alteration and/or re-equilibration of various phosphate and silicate minerals or phosphate-silicate mineral groups. Experimental projects include:
- Experimental fluid-aided incorporation of actinides into monazite and xenotime utilizing both alkali-rich fluids and simple, fluid-rich granitic melts
- Experimental dissolution of monazite and xenotime in NaCl- and NaF-bearing fluids as a function of P-T
- Test dating of experimentally fluid-altered, Pb-depleted monazite utilizing electron microprobe analysis
- Experimental incorporation or depletion of Th, U, and (Y+HREE) into zircon utilizing alkali-bearing and Ca-bearing fluids
- Experimental determination of fluorapatite, monazite, xenotime, allanite, and REE-enriched epidote stability fields in monazite-apatite-allanite and xenotime-apatite-allanite metapelitic systems as a function of P-T-X
- LREE-redistribution between fluorapatite, monazite, and allanite at high pressures and temperatures
- Thermodynamic, XRD, IR, Raman, and electron microscopic analytical characterization of apatite across the F – Cl, F – OH, and Cl – OH joins
- Experimental fluid-aided incorporation of (Y+HREE) into garnet as a function of P-T-X
- Experimental fluid-aided incorporation of As and Sb into dumortierite under subduction zone P-T conditions
- The experimental stability of scapolite as a function of P-T-XNaCl under amphibolite- to granulite-facies conditions.
© GFZ Potsdam- Examples of monazite grains experimentally metasomatised at 900 °C and 1000 MPa using a CaF2 assembly in the piston cylinder press. Any cracks seen occurred during the mounting and polishing process of the monazite grain fragments. a. MX54: Monazite grain metasomatised in a 2N KOH solution for 8 days. b. MX71: Monazite grain metasomatised in a 2N NaOH solution for 25 days. c. MX72a: Monazite grain metasomatised in a Na2Si2O5 + H2O solution for 2 days. d. MX72b: Monazite grain metasomatised in a Na2Si2O5 + H2O solution for 8 days. In all four case Th appears to be highly mobile and monazite highly reactive in alkali-bearing solutions. See Harlov et al. (2011) Contrib Mineral Petrol 162, 329–348 for more details.
© GFZ Potsdam- High contrast BSE and CL image of a natural zircon experimentally metasomatised using a NaF + H2O solution + ThO2 + SiO2 at 900 °C and 1000 MPa (Au capsule, CaF2 assembly, piston cylinder press). SHRIMP analysis of the original zircon are in black. SHRIMP analysis of the altered zircon (white areas under CL imaging) are in red. Altered areas are heavily depleted in U + Pb and enriched in Th. This suggests that zircon is highly reactive and U and Th highly mobile in alkali-bearing solutions.
© GFZ Potsdam- High contrast BSE image and electron microprobe element maps of a natural garnet (Gore Mountain) experimentally metasomatised in a Y2O3 + 2 M NaOH solution at 900 °C and 1000 MPa in a Au capsule using a CaF2 assembly in the piston cylinder press. The garnet experienced both overgrowth and partial replacement by Y-enriched garnet. This suggests a high reactivity for the garnet and a high mobility for Y in an alkali-bearing solution.
Contact: Daniel Harlov