Photon Factory Activity Report 2004 #22 Part B (2005)
Crystallography

10A/2003G208

The compressibility of natural norbergite, Mg2.98Fe0.01Ti0.01Si0.99O4(OH0.31, F1.69)
Takahiro KURIBAYASHI1*, Masahiko TANAKA2,3, Yasuhiro KUDOH1
1
Institute of Mineralogy, Petrology and Economic Geology, Graduate School of Science, Tohoku
University, Sendai 980-8578, Japan
3
WEBRAM, MIMS, Nishi-Harima, Hyogo 679-5198, Japan

Experimental Procedure
The sample used for this study is from Sterling Hill
Mine, New Jersey, U.S.A. A single crystal of norbergite
3(60×50×40 µm in size) was mounted in a modified
Merrille-Bassett type diamond anvil cell with a small
piece of a ruby crystal, which used for the pressure
calibration. The 4:1 fluid mixture of methanol andethanol was used for the pressure medium and a SUS301
stainless plate used for a gasket. Pressure was determinedby the ruby fluorescence method [2]. The wavelength ofsynchrotron radiation was calibrated by the unit cellvolume of the ruby standard crystal at ambient
temperature (λ=0.7004 Å for 0.5, 3.1, 4.2 and 5.4 GPa;
λ=0.7002 Å for 4.7 and 6.3 GPa; (λ=0.6989 Å for 0.0001,7.6 and 8.2 GPa). The X-ray diffraction were measured
using an automated four-circle X-ray diffractometer
installed at the beam line BL-10A, Photon Factory, HighEnergy Accelerator Research Organization. The unit cellparameters of norbergite were determined from 25
centered reflections in the 2θ range between 12.5° and30.9° under all high-pressure conditions.
Results
The unit cell parameters of norbergite at each pressure
condition were listed in Table 1. The axial linear
compressibilities of this norbergite were calculated usingthese results, yielding to βa=2.18(4), βb=2.93(7) and
βc=2.77(7) (× 10-3 / GPa). The big and small relationshipof linear compressibility of norbergite was the same as
those of the other humite minerals.

200

Users' Report

In similarly, the isothermal bulk modulus of thisspecimen was calculated as K=113(2) GPa assuming K′=4.
This result is plotted on the simple positive correlation [3]between K and density (ρ) of the minerals in some densehydrous silicate minerals (Fig. 1).
Table 1. The lattice parameters of natural norbergite
at each pressure point up to 8.2 GPa
P (GPa)abcV
0.00014.709(2) 10.279(3) 8.754(4) 423.7(2)0.5
4.701(2) 10.254(2) 8.736(3) 421.1(2)3.1
4.674(2) 10.176(2) 8.670(3) 412.3(2)4.2
4.662(2) 10.138(2) 8.642(3) 408.5(2)4.7
4.657(2) 10.120(3) 8.626(3) 406.5(2)5.4
4.652(2) 10.114(2) 8.619(3) 405.5(2)6.3
4.645(2) 10.085(2) 8.604(3) 403.1(2)7.6
4.637(2) 10.059(2) 8.574(3) 399.9(2)8.24.625(2) 10.049(2) 8.569(4) 398.2(2)180
Per [13]160
Sp.hy-B [12]Bulk modulus (GPa)Introduction
Norbergite (n=1), which is a hydrous magnesium
silicate mineral, is known as one of the humite minerals
described as nMg2SiO4⋅Mg(OH,F)2 (n=1-4).
Also,
forsterite, Mg2SiO4, is known as the most importantmineral in the Earth′s mantle. Forsterite and the humite
minerals constitute the polysomatic series. The humite
minerals are important in the view of the carriers andreservoirs of water in the Earth′s deep interior, because
these minerals are stable under high-pressure and hightemperature mantle conditions [1].
We performed a high-pressure single crystal X-ray
diffraction study on a natural norbergite at ambient, 0.5,3.1, 4.2, 4.7, 5.4, 6.3, 7.6 and 8.2 GPa in order toinvestigate its compressibility and crystal structure. In
this paper, we reported the axial linear compressibility
and the isothermal bulk modulus of this specimen.

Ph A [8]140Sp.hy-B [11]CD [6]

Fo [10]CD [16] Fo [9]OH-CH [3]CD [4]
OH-CD [3]CD [5]
OH-CD [16]120This study

Ph A [15]100

Ph A [7]Ph E [14]8060

Br [2]

40
2.20

Br [1]

2.40

2.60

2.80

3.00

3.20

3.40

3.60

3.80

3Density (g/cm )Figure 1. The relationship between density and bulk
modulus in some dense hydrous silicate minerals.
References[1] B. Wunder, Contrib. Mineral. Petrol., 132, 111-120,(1998). [2] G. J. Piermarini et al. J. Appl. Phys., 46,2774-2780, (1975). [3] Kuribayashi et al., J. Mineral.
Petrol. Sci., 99, 118-129, (2004)* t-kuri@mail.tains.tohoku.ac.jp