A single-crystal study on the pressure behavior of phlogopite and petrological implications

Abstract

The structural behavior of phlogopite was studied by in situ single-crystal X-ray diffraction (XRD) in a diamond-anvil cell, using crystals of composition [(K0.91Na0.02Ba0.03) (Fe2+0.65Fe3+0.163Al0.123Mg1.81Ti0.149)Si2.708Al1.292O10OH1.725F0.175]. Lattice parameters were measured from 0.0001 to 6.5 GPa and fitted with a third-order Birch-Murnaghan equation of state (EoS). The resulting EoS parameters are: V0 = 497.1(1) Å3, K0 = 54(2) GPa-1, and K' = 7(1); a0 = 5.336(1) Å, K0 = 123(9) GPa, and K' = 3(2); b0 = 9.240(3) Å, K0 = 128(15) GPa, and K' = 3(2); c0 = 10.237(6) Å, K0 = 25(2) GPa, and K' = 5(1); the β angle increases linearly with pressure from 100.02(5) to 100.4(1)°.