SPINEL, KALSILITE, CLINOPYROXENE AND OLIVINE by

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Sample synthesis Experimental Magnesium vanadate spinel was synthesized at 1 bar and 1200 °C at an oxygen fugacity equivalent to 1.3 log fO2 units above the fayalite-magnetite-quartz (FMQ) buffer, from a mixture of MgO and V2O3 (99.995% pure). The material was placed on a Re wire loop in the hot spot of a Deltech vertical furnace. Oxygen fugacity was controlled by mixing CO and CO2 in a reference furnace at 1200 °C, where the desired emf was adjusted before the introduction of the sample. The sample was held in the hot spot for 72 hours, and then quenched by rapid removal. The synthesis products are clear octahedra of periclase and black spinel crystals, ranging from 30 to 50 μm in size. Microprobe analysis Five spinel crystals were selected from the same synthesis run and analyzed on a Cameca SX50 electron microprobe, using an acceleration voltage of 15 kV, a beam current of 20 nA, beam diameter of 2 μm, and 20 s counting times. Natural diopside and pure metallic vanadium were used as standards. Approximately 10 points were analyzed on the inclusion-free regions of each crystal. The chemical formula of the spinel, Mg1.37V 3+ 1.26 V 4+ 0.37O4, was determined based on the analyses of the five crystals (Table 1). The amount of VO2 was estimated by adjusting the sum of cation numbers to three and the total cation charge of eight. The back-scattered electron (BSE) images showed the presence of Mg-rich inclusions in all of these spinel crystals (Figs. 1a and b). 46
However, the inclusions were too small (≤ 3 μm) for an accurate chemical analysis. The crystals in Figures 1a and b were oriented and polished to parallel to (001) and (111) planes, respectively. The inclusions in these crystals appear to exhibit specific crystallographic orientations, with 4-fold and 3-fold symmetry, respectively. EBSD / XEDS The crystal was placed on a vibratory polisher with 0.05-micron colloidal silica suspension for approximately 10 minutes to obtain optimal diffraction patterns. An EDAX-TSL OIM 4.6 EBSD (electron backscatter diffraction) system coupled with an EDAX Genesis 4.5 XEDS system was employed to determine the chemistry of the Mg- rich inclusions and their crystallographic orientation with respect to the spinel phase. These systems were mounted on an FEI XL30 Scanning Electron Microscope (SEM). The XEDS spectra at 20, 15, 12, and 10 kV were measured to quantify the excitation volumes for the inclusion as a function of acceleration voltage. The calculated excitation volumes at those voltages are 8, 1, 0.4, 0.1 µm 3 , respectively. The height of V peaks decreased at lower voltages, indicating that the presence of V at higher voltages is the result of interference with the matrix. Therefore, we conclude that the inclusions are pure MgO. For phase and orientation mapping, the sample was tilted approximately 75 degrees and analyzed with an acceleration voltage of 20 kV. In order to map out the orientation relationships in the crystal, EBSD patterns were systematically collected and automatically indexed to obtain individual crystallographic orientations over an array of measurement points. Since the crystal structures of the matrix and inclusions are quite 47
Page 1 and 2: CRYSTAL CHEMICAL AND STRUCTURAL ANA
Page 3 and 4: STATEMENT BY AUTHOR This dissertati
Page 5 and 6: DEDICATION This dissertation is ded
Page 7 and 8: TABLE OF CONTENTS - Continued APPEN
Page 9 and 10: ABSTRACT Natural and synthetic comm
Page 11 and 12: Explanation of the Problem and its
Page 13 and 14: (APPENDIX C), clinopyroxene (APPEND
Page 15 and 16: etween observed structure and the m
Page 17 and 18: close to 1.0 for Fa24 at room tempe
Page 19 and 20: crystallization can provide useful
Page 21 and 22: limit of ~ 25 kbars in the equilibr
Page 23 and 24: isotopes (Zartman and Tera 1973). F
Page 25 and 26: crystals are present (up to 1 cm) (
Page 27 and 28: Downs (2001). I examined packing di
Page 29 and 30: the substitution of Co for Mg resul
Page 31 and 32: Figure 2. Two melting indicators, A
Page 33 and 34: Fig. 3 cont. (b) (c) (d) 33
Page 35 and 36: Fig. 3 cont. (h) (i) 35
Page 37 and 38: REFERENCES Aoki, K. (1975) Origin o
Page 39 and 40: Princivalle, F., Della Giusta, A.,
Page 41 and 42: APPENDIX A: INVESTIGATION OF SYNTHE
Page 43 and 44: (XEDS) suggested that the Mg-rich i
Page 45: The presence of a small amount of c
Page 49 and 50: Turner (1968). The refined paramete
Page 51 and 52: is occupied, the nearest octahedral
Page 53 and 54: the observed tetrahedral bond dista
Page 55 and 56: length because of its low abundance
Page 57 and 58: Devanathan, R., Yu, N., Sickafus, K
Page 59 and 60: Nowell, M.M. and Wright, S.I. (2004
Page 61 and 62: Figure 1. BSE images of (a) the sel
Page 63 and 64: Figure 2. XEDS maps and statistics.
Page 65 and 66: Figure 3. EBSD patterns of (a) spin
Page 67 and 68: Figure 5. Two possible structural i
Page 69 and 70: Table 1. Chemical composition of Mg
Page 71 and 72: Table 3. Comparison of refinement r
Page 73 and 74: APPENDIX B: AN APPARENT SYMMETRY P6
Page 75 and 76: Additionally, the same crystal from
Page 77 and 78: displacive transformation between P
Page 79 and 80: 1955) and later in most kalsilite (
Page 81 and 82: temperatures on a Bruker X8 APEX si
Page 83 and 84: oxygen, O1, and assigning O1 off th
Page 85 and 86: layers was on the 3-fold axis. This
Page 87 and 88: ecame more perpendicular to the c a
Page 89 and 90: Downs, R.T. (2000) Analysis of harm
Page 91 and 92: Figure 1. Unit-cell volume changes
Page 93 and 94: c-c o 0.06 0.04 0.02 0.00 -0.02 -0.
Page 95 and 96: Table 1. Chemical composition (wt%)
Page 97 and 98:
Table 3. Summary of crystal data an
Page 99 and 100:
Table 4. Refinement results at room
Page 101 and 102:
Table 4. cont. ====================
Page 103 and 104:
Table 4. cont. ====================
Page 105 and 106:
Single-crystal X-ray diffraction of
Page 107 and 108:
to the host basalt but rather they
Page 109 and 110:
O and T-O bond distances (u = 0.262
Page 111 and 112:
temperature of TQ onto the equilibr
Page 113 and 114:
higher value of Rw, but it insures
Page 115 and 116:
would rigidly constrain the optimiz
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these three figures. In addition to
Page 119 and 120:
Closure temperatures, Tc, for our s
Page 121 and 122:
Bond distances, T-O vs. M-O, are pl
Page 123 and 124:
Finger, L.W. and Prince, E. (1975)
Page 125 and 126:
diffraction study of MgAl2O4 at tem
Page 127 and 128:
Figure 1. Chemistry of spinels from
Page 129 and 130:
129
Page 131 and 132:
131
Page 133 and 134:
Figure 4. Closure temperatures vers
Page 135 and 136:
Figure 6. Bond distances, M-O vs. T
Page 137 and 138:
Table 2. Structural refinement resu
Page 139 and 140:
Table 2. cont. Sample SC 1 SC 11 SC
Page 141 and 142:
Table 4. Cation distribution, inver
Page 143 and 144:
Table 4. cont. Sample Occ T Occ M F
Page 145 and 146:
APPENDIX D: CRYSTAL CHEMISTRY OF CL
Page 147 and 148:
effect on Ucp in case of clinopyrox
Page 149 and 150:
Pyroxene is an important mineralogi
Page 151 and 152:
and M polyhedra (VT and VM, respect
Page 153 and 154:
Ganguly 2003). Liermann and Ganguly
Page 155 and 156:
crystal chemistry of those samples.
Page 157 and 158:
Experimental Crystals were selected
Page 159 and 160:
of both xenoliths types. The absenc
Page 161 and 162:
temperature and pressure for the sa
Page 163 and 164:
elationships among geometrical para
Page 165 and 166:
We examined the datasets to find th
Page 167 and 168:
Figure 6 shows a correlation betwee
Page 169 and 170:
References Basu, A.R. and MacGregor
Page 171 and 172:
Galer, S.J.G. and O’Nions, R.K. (
Page 173 and 174:
Princivalle, F., Salviulo, G., Fabr
Page 175 and 176:
Witt-Eickschen, G. and Seck, H.A. (
Page 177 and 178:
Figure 2. Estimated pressure and te
Page 179 and 180:
(b) 179
Page 181 and 182:
(b) 181
Page 183 and 184:
Figure 6. Correlation between Ucp (
Page 185 and 186:
Table 1. Chemical composition of th
Page 187 and 188:
Table 2. cont. SC19 SC1 SC11 a (Å)
Page 189 and 190:
Table 3. cont. SC19 SC1 SC11 M1 y 0
Page 191 and 192:
Table 5. Pressure and temperature e
Page 193 and 194:
Investigation of distortions from i
Page 195 and 196:
ideal geometry. For olivine, while
Page 197 and 198:
and shown to have a widely ranging
Page 199 and 200:
this viewpoint gave meaningful resu
Page 201 and 202:
201 After the X-ray data collection
Page 203 and 204:
Discussion (1) Relationship between
Page 205 and 206:
NiMgSiO4 (Henderson et al. 2001), F
Page 207 and 208:
increases. As Thompson and Downs (2
Page 209 and 210:
correlated with the average radii o
Page 211 and 212:
211 We have shown in Uchida et al.
Page 213 and 214:
Belokoneva, E.L., Ivanov, Y.A., Sim
Page 215 and 216:
Kimata, M. and Nishida, N. (1987) T
Page 217 and 218:
Smyth, J.R. (1975) High-temperature
Page 219 and 220:
Figure 2. x coordinate vs. y coordi
Page 221 and 222:
Figure 4. Ucp (Å 2 ) as a function
Page 223 and 224:
Ucp 0.075 0.070 0.065 (b) Ucp = 0.0
Page 225 and 226:
Figure 7. Changes in lengths of O-O
Page 227 and 228:
Table 1. Chemical composition of th
Page 229 and 230:
Table 2. cont. SC19 SC1-2 SC11-4 SC
Page 231 and 232:
Table 3.cont. SC8 SC2 SC19 SC1-2 SC
Page 233:
Table 4. Ucp of selected silicate a
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SPINEL, KALSILITE, CLINOPYROXENE AND OLIVINE by

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