Fluid-induced nucleation of (Y+REE)-phosphate minerals within apatite: Nature and experiment. Part II. Fluorapatite
-
Daniel E. Harlov
and
Hans-Jürgen Förster
Abstract
To elucidate at what pressure and temperature and for what fluid compositions monazite may be induced to form from fluorapatite, the LREE-enriched Durango fluorapatite has been metasomatized experimentally at temperatures of 300, 600, 700, 800, 850, and 900°C and pressures of 500 and 1000 MPa. Fluids used included pure H2O, various NaCl, KCl, and CaCl2 brines (salt/H2O = 50/50, 30/70, or 10/90), and either 90/10 CO2/H2O or 40/60 CO2/H2O mix. Monazite formed in the fluorapatite + H2O, fluorapatite + 40/60 CO2/H2O, and the fluorapatite + KCl brine experiments. At 900°C and 1000 MPa, monazite formed both as inclusions within the fluorapatite and externally on its surface. Below 900°C, monazite grew only externally on the fluorapatite, either as euhedral to semi-euhedral crystals or as partial mantles over smaller fluorapatite grains. Monazite, especially at 900°C and 1000 MPa, is compositionally heterogeneous, specifically with respect to the Th content (ThO2 = 4-38 wt%). Whereas the reactant fluorapatite in the pure H2O experiments remained unzoned at lower temperatures, three coupled zones with different (LREE+Si+Na) abundances developed at 900°C. These zones roughly follow the rim of the fluorapatite enclosing a fourth zone or the core, resembling the original composition. Monazite inclusions formed only in the one zone where the LREE are depleted. In the NaCl brine experiments, the Na replaced Si lost to the solution, which stabilized the LREE, and precluded formation of monazite. Similarly, the high activity of Ca in the CaCl2 brine caused Ca to replace (LREE+Na) on the Ca site and discouraged the growth of monazite. The fluorapatite recrystallized to a fluor-chlorapatite, which displays oscillatory zoning, specifically with respect to the LREE. The results from this study imply that the presence of monazite inclusions and rim grains associated with fluorapatite (1) can be metasomatically induced; (2) can give insights into the chemistry of the metasomatizing fluids; (3) can provide some information on the grade of the metasomatic overprint; and (4) could indicate the occurrence of one or more metasomatic events
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Melting of garnet peridotite: Effects of capsules and thermocouples, and implications for the high-pressure mantle solidus
- High-resolution and energy-filtered TEM of the interface between hematite and ilmenite exsolution lamellae: Relevance to the origin of lamellar magnetism
- The structural evolution of mercury sulfide precipitate: an XAS and XRD study
- Synthetic fluid inclusions as recorders of microfracture healing and overgrowth formation rates
- Fluid-induced nucleation of (Y+REE)-phosphate minerals within apatite: Nature and experiment. Part II. Fluorapatite
- A technique for measuring 3D crystal-size distributions of prismatic microlites in obsidian
- TEM investigation of forsterite dendrites
- Mechanism and kinetics of element and isotopic exchange mediated by a fluid phase
- Chromian spinel during melting experiments of dry peridotite (KLB-1) at 1.0–2.5 GPa
- Resonant XPS study of the pyrite valence band with implications for molecular orbital contributions
- Petrology and mineralogy of wollastonite- and melilite-bearing paralavas from the Central Apennines, Italy
- Variation of antiphase domain size in omphacite: A tool to determine the temperature–time history of eclogites revisited
- Compressional and shear wave velocities of ringwoodite γ-Mg2SiO4 to 12 GPa
- A vibrational spectroscopic study of the oxidation of pyrite by ferric iron
- The atomic arrangement of the ganophyllite-group modulated layer silicates as determined from the orthorhombic dimorph of tamaite, with the elusive 16.8 Å ganophyllite-group superstructure revealed
- The crystal structure of chromian kassite from the Saranovskoye deposit, Northern Urals, Russia
- Spectroscopic and related evidence on the coloring and constitution of New Zealand jade
- Chemical speciation of Ag in galena by EPR spectroscopy
- Pressure dependence of melt viscosity in the system NaAlSi3O8-CaMgSi2O6
- Molecules in the SiO2-clathrate melanophlogite: A single-crystal Raman study
- Mn-rich tourmaline from Austria: structure, chemistry, optical spectra, and relations to synthetic solid solutions
- Compositional heterogeneity of olivine in thermally metamorphosed serpentinite from Southwest Japan
- Magnetic monitoring of hydrothermal magnetite nucleation-and-growth: Record of magnetic reversals
- High-temperature limits on viscosity of non-Arrhenian silicate melts
- First reported sedimentary occurrence of berlinite (AlPO4) in phosphate-bearing sediments from Cioclovina Cave, Romania
Articles in the same Issue
- Melting of garnet peridotite: Effects of capsules and thermocouples, and implications for the high-pressure mantle solidus
- High-resolution and energy-filtered TEM of the interface between hematite and ilmenite exsolution lamellae: Relevance to the origin of lamellar magnetism
- The structural evolution of mercury sulfide precipitate: an XAS and XRD study
- Synthetic fluid inclusions as recorders of microfracture healing and overgrowth formation rates
- Fluid-induced nucleation of (Y+REE)-phosphate minerals within apatite: Nature and experiment. Part II. Fluorapatite
- A technique for measuring 3D crystal-size distributions of prismatic microlites in obsidian
- TEM investigation of forsterite dendrites
- Mechanism and kinetics of element and isotopic exchange mediated by a fluid phase
- Chromian spinel during melting experiments of dry peridotite (KLB-1) at 1.0–2.5 GPa
- Resonant XPS study of the pyrite valence band with implications for molecular orbital contributions
- Petrology and mineralogy of wollastonite- and melilite-bearing paralavas from the Central Apennines, Italy
- Variation of antiphase domain size in omphacite: A tool to determine the temperature–time history of eclogites revisited
- Compressional and shear wave velocities of ringwoodite γ-Mg2SiO4 to 12 GPa
- A vibrational spectroscopic study of the oxidation of pyrite by ferric iron
- The atomic arrangement of the ganophyllite-group modulated layer silicates as determined from the orthorhombic dimorph of tamaite, with the elusive 16.8 Å ganophyllite-group superstructure revealed
- The crystal structure of chromian kassite from the Saranovskoye deposit, Northern Urals, Russia
- Spectroscopic and related evidence on the coloring and constitution of New Zealand jade
- Chemical speciation of Ag in galena by EPR spectroscopy
- Pressure dependence of melt viscosity in the system NaAlSi3O8-CaMgSi2O6
- Molecules in the SiO2-clathrate melanophlogite: A single-crystal Raman study
- Mn-rich tourmaline from Austria: structure, chemistry, optical spectra, and relations to synthetic solid solutions
- Compositional heterogeneity of olivine in thermally metamorphosed serpentinite from Southwest Japan
- Magnetic monitoring of hydrothermal magnetite nucleation-and-growth: Record of magnetic reversals
- High-temperature limits on viscosity of non-Arrhenian silicate melts
- First reported sedimentary occurrence of berlinite (AlPO4) in phosphate-bearing sediments from Cioclovina Cave, Romania
