Fluid-induced nucleation of (Y + REE)-phosphate minerals within apatite: Nature and experiment. Part I. Chlorapatite
-
Daniel E. Harlov
,
Hans-Jürgen Förster
Abstract
This study investigates chlorapatite [ideally Ca10(PO4)6Cl2)] from two spatially separated locations in the Ødegårdens Verk apatite mine, Bamble Sector, SE Norway, which was partially metasomatized under amphibolite-facies conditions. Relative to the original chlorapatite, metasomatized areas in sample DL136 are enriched in OH and F, depleted in Na, Si, and (Y + REE) and contain numerous inclusions (1-15 μm) of monazite and xenotime. In contrast, metasomatized areas in sample TN174 are enriched in F and Si, depleted in Na, show (Y + REE) abundances similar to the original chlorapatite, and host only a few monazite and xenotime grains.
In order to define the role of fluids in the formation of (Y + REE)-phosphate minerals associated with apatite, a series of experiments covering wide ranges of temperature (900-300 °C) and pressure (1000-500 MPa) for a series of fluid compositions (pure H2O, a 50/50 molar mix of H2O and CaF2, and CO2 with 1-2 wt% H2O) were conducted on unaltered chlorapatite from the Ødegårdens Verk. In the H2O experiments, features due to metasomatic alteration [depletion in Na, Si, and (Y + REE) as well as numerous monazite and xenotime inclusions], as observed in the natural sample DL136, were fully reproduced. Monazite and xenotime grains were also observed growing on the surface of the apatite in dissolution embayments in metasomatized areas. In the 50/50 CaF2-H2O experiments, metasomatized regions are strongly enriched in F and Si, depleted in Na, show unchanged (Y + REE) abundances, and contain only a very few, small monazite and xenotime grains similar to what was observed in sample TN174.
Natural and experimental observation imply the presence of two coupled substitutions: Na+ + (Y + REE)3+ = 2 Ca2+ and Si4+ + (Y + REE)3+ = P5+ + Ca2+. In the case of DL136 and H2O-fluid experiments, Na+ and Si4+ went into solution, whereas the released (Y + REE) contributed to the growth of monazite and xenotime within the metasomatized apatite structure. For sample TN174 and the 50/50 CaF2 + H2O-fluid experiments, Na in apatite became depleted but Si was enriched thereby stabilizing the (Y + REE) in the now recrystallized fluor-hydroxylapatite structure, which retarded the growth of monazite or xenotime inclusions. The basic conclusion of this study is that nucleation of monazite and xenotime in the metasomatized chlorapatite is principally a function of the composition of the infiltrating fluid and, to a much lesser extent, temperature and pressure.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Presidential Address. Scales of disequilibrium and rates of equilibration during metamorphism
- Characterization of coexisting NH4- and K-micas in very low-grade metapelites
- Effect of sonic and ultrasonic frequencies on the crystallization of basalt
- Sulfur saturation limits in silicate melts and their implications for core formation scenarios for terrestrial planets
- Molecular water in beryl, VIAl2 [Be3Si6O18]·nH2O, as a function of pressure and temperature: An experimental study
- Fluid-induced nucleation of (Y + REE)-phosphate minerals within apatite: Nature and experiment. Part I. Chlorapatite
- X-ray spectroscopic investigations of fluids in the hydrothermal diamond anvil cell: The hydration structure of aqueous La3+ up to 300 °C and 1600 bars
- Fibrous nanoinclusions in massive rose quartz: HRTEM and AEM investigations
- Polysomatism in högbomite: The crystal structures of 10T, 12H, 14T, and 24R polysomes
- Ordering of hydroxyl defects in hydrous wadsleyite (β-Mg2SiO4)
- The crystal structure and cation ordering of Phase-X-(K1–x–n)2(Mg1–n[Al,Cr]n)2Si2O7H2x: A potential K- and H-bearing phase in the mantle
- Feasibility of determining the quantitative OH content of garnets with Raman spectroscopy
- Raman spectroscopic study of garnet inclusions in diamonds from the mantle transition zone
- Raman spectroscopy of Fe2O3 to 62 GPa
- Study of the (010) olivine surface by Rutherford backscattering spectrometry in channeling geometry
- Equation of state of dense hydrous magnesium silicate phase A, Mg7Si2O8(OH)6
- Si-F bonding in aluminosilicate glasses: Inferences from ab initio NMR calculations
- Monoclinic nearly stoichiometric wüstite at low temperatures
- On the nature of tincalconite
- Letters. Chloride ion sites in silicate and aluminosilicate glasses: A preliminary study by 35Cl solid-state NMR
- Nuclear magnetic resonance and infrared spectroscopic study of excess-boron olenite from Koralpe, Styria, Austria
Articles in the same Issue
- Presidential Address. Scales of disequilibrium and rates of equilibration during metamorphism
- Characterization of coexisting NH4- and K-micas in very low-grade metapelites
- Effect of sonic and ultrasonic frequencies on the crystallization of basalt
- Sulfur saturation limits in silicate melts and their implications for core formation scenarios for terrestrial planets
- Molecular water in beryl, VIAl2 [Be3Si6O18]·nH2O, as a function of pressure and temperature: An experimental study
- Fluid-induced nucleation of (Y + REE)-phosphate minerals within apatite: Nature and experiment. Part I. Chlorapatite
- X-ray spectroscopic investigations of fluids in the hydrothermal diamond anvil cell: The hydration structure of aqueous La3+ up to 300 °C and 1600 bars
- Fibrous nanoinclusions in massive rose quartz: HRTEM and AEM investigations
- Polysomatism in högbomite: The crystal structures of 10T, 12H, 14T, and 24R polysomes
- Ordering of hydroxyl defects in hydrous wadsleyite (β-Mg2SiO4)
- The crystal structure and cation ordering of Phase-X-(K1–x–n)2(Mg1–n[Al,Cr]n)2Si2O7H2x: A potential K- and H-bearing phase in the mantle
- Feasibility of determining the quantitative OH content of garnets with Raman spectroscopy
- Raman spectroscopic study of garnet inclusions in diamonds from the mantle transition zone
- Raman spectroscopy of Fe2O3 to 62 GPa
- Study of the (010) olivine surface by Rutherford backscattering spectrometry in channeling geometry
- Equation of state of dense hydrous magnesium silicate phase A, Mg7Si2O8(OH)6
- Si-F bonding in aluminosilicate glasses: Inferences from ab initio NMR calculations
- Monoclinic nearly stoichiometric wüstite at low temperatures
- On the nature of tincalconite
- Letters. Chloride ion sites in silicate and aluminosilicate glasses: A preliminary study by 35Cl solid-state NMR
- Nuclear magnetic resonance and infrared spectroscopic study of excess-boron olenite from Koralpe, Styria, Austria
