MR016-0016
Single-Crystal X-Ray Diffraction of Fluorapatite to 60 GPa

Wednesday, 16 December 2020
Poster
Melinda Rucks1, Gregory J Finkelstein1, Dongzhou Zhang2, Przemeslaw Dera3,4 and Thomas S Duffy1, (1)Princeton University, Princeton, NJ, United States, (2)University of Hawaii at Manoa, Hawaii Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, Honolulu, HI, United States, (3)University of Chicago, GeoSoilEnviroCARS, Chicago, IL, United States, (4)University of Hawai'i at Manoa, Hawai'i Institute of Geophysics and Planetology, Honolulu, HI, United States
Abstract:
Apatite, Ca5(PO4)3(F,Cl,OH), is the most abundant phosphate mineral in the Earth’s crust and is a key repository in the upper mantle for phosphorous and halogens1. Apatite is often used to constrain the petrogenetic history of terrestrial samples and the environmental factors that influence their formation2. Previous experimental studies of the behavior of apatite under compression above 20 GPa are limited3. In this study, we use single-crystal X-ray diffraction to study the structural response of natural fluorapatite to pressures up to 60 GPa.

Experiments were conducted at the 13-BM-C (PX^2) beamline at the Advanced Photon Source at Argonne National Laboratory using a natural single crystal of Durango apatite. The sample was loaded in a He-gas loaded SS-DAC-70 diamond anvil cell and compressed at room temperature using a gas membrane. Single-crystal diffraction data were collected over a 58 degree angular range on a single rotation axis with a ¼ degree step size. Diffraction patterns were collected at ~ 3 GPa intervals. Ruby spheres and Au foil were used as pressure calibrants. The evolution of the crystal structure of apatite was constrained to ~30 GPa, at which point it undergoes at least one phase transition. Here, we will discuss the resulting apatite equation of state and pressure-driven changes in crystallographic parameters.

1 J.V. Smith, Nature 289, 762 (1981). 2 J.D. Webster and P.M. Piccoli, Elements 11, 177 (2015). 3 F. Brunet, D.R. Allan, S.A.T. Redfern, R.J. Angel, R. Miletich, H.J. Reichmann, J. Sergent, and M. Hanfland, Eur. J. Mineral. 11, 1023 (1999).

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