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205 TABLE 4.5 UNIT 10 PLAGIOCLASE PARTITION COEFFICIENTS <strong>AND</strong> INFERRED PARENT MAGMA COMPOSITIONS Sample Zone An DRb DSr DY DBa DLa DCe DP r DNd DSm Rb Sr Y Ba La Ce Pr Nd Sm (mol%) 10-1C-A C 60 0.01 2.02 0.01 0.36 0.11 0.09 0.07 0.05 0.03 58.3 426.8 10.3 372.3 10.3 28.5 3.2 16 4.5 10-1C-A I 65 0.01 1.9 0.01 0.31 0.11 0.09 0.07 0.05 0.03 53.9 469.3 14.5 340.4 10.3 25.8 3 14.8 5 10-1C-A I 62 0.01 1.96 0.01 0.33 0.11 0.09 0.07 0.05 0.03 67.3 464.7 13.9 424.3 11 29.1 3.5 16.7 5 10-1C-A R 66 0.01 1.86 0.01 0.3 0.1 0.09 0.07 0.05 0.03 47 449.3 14.1 324.2 9.8 24.5 2.8 13.4 2.7 10-1C-B1 C 65 0.01 1.87 0.01 0.3 0.11 0.09 0.07 0.05 0.03 58.8 478.1 14.8 468.9 11 32.7 3.9 18.6 4.3 10-1C-B1 I 61 0.01 1.99 0.01 0.35 0.11 0.09 0.07 0.05 0.03 82.2 455.2 19.6 426 11.6 32.3 3.3 18.6 4.7 10-1C-B1 I 65 0.01 1.87 0.01 0.3 0.11 0.09 0.07 0.05 0.03 43.8 452.4 10.9 370.8 10.2 30.1 3.2 15.4 5 10-1C-B1 I 64 0.01 1.9 0.01 0.31 0.11 0.09 0.07 0.05 0.03 47.9 422.7 16.2 351 9.5 27.5 2.9 16 4.3 10-1C-B1 R 66 0.01 1.84 0.01 0.29 0.1 0.09 0.07 0.05 0.03 40.9 460 12.4 378.9 10.2 29.9 3.2 16.4 2.8 10-1C-B2 C 58 0.01 2.08 0.01 0.38 0.11 0.09 0.07 0.05 0.03 91.4 438.6 22.5 395.9 13 35.4 4.2 17.9 5.4 10-1C-B2 I 64 0.01 1.92 0.01 0.32 0.11 0.09 0.07 0.05 0.03 49.1 419.1 14.8 327 9.9 29 3.3 17.1 3.9 10-1C-B2 I 62 0.01 1.98 0.01 0.34 0.11 0.09 0.07 0.05 0.03 42.4 404.2 14.5 330.6 10 28.3 3.3 15.1 3.9 10-1C-B2 R 59 0.01 2.07 0.01 0.38 0.11 0.09 0.07 0.05 0.03 72.5 392.3 14.1 299.2 9.6 25.2 3.1 13.2 2.9 10-2A-D C 59 0.01 2.06 0.01 0.37 0.11 0.09 0.07 0.05 0.03 54.8 430.1 22.3 341.5 12.6 25.8 3.4 16.8 6.3 10-2A-D R 67 0.01 1.84 0.01 0.29 0.1 0.09 0.07 0.05 0.03 41 422.8 24.6 290.8 11.6 21.4 2.8 14 3.8 10-2A-C C 58 0.01 2.1 0.01 0.39 0.11 0.09 0.07 0.05 0.03 58.4 411.2 18.5 309.7 12.7 25.1 3.6 18.2 6 10-2A-C I 62 0.01 1.97 0.01 0.34 0.11 0.09 0.07 0.05 0.03 71.7 476.8 22.3 409.2 13.6 27.1 3.9 16.4 4.4 10-2A-C I 67 0.01 1.82 0.01 0.29 0.1 0.09 0.07 0.05 0.03 31.7 423.5 18.6 293.8 10.7 23 3.3 15.1 4 10-2A-C R 65 0.01 1.87 0.01 0.3 0.11 0.09 0.07 0.05 0.03 39.7 451.6 21.5 333.9 12.4 24.3 3.4 15.2 5 10-1C-D C 63 0.01 1.94 0.01 0.33 0.11 0.09 0.07 0.05 0.03 47.4 413.4 17 349.3 9.1 26.2 3 14.6 3.3 10-1C-D I 60 0.01 2.05 0.01 0.37 0.11 0.09 0.07 0.05 0.03 63 391 7.7 396.3 10.1 28.8 2.9 11.4 3.1 10-1C-D I 63 0.01 1.95 0.01 0.33 0.11 0.09 0.07 0.05 0.03 68.2 409.4 16.9 427.6 9.9 27.7 3.1 13.3 3.3 10-1C-D I 59 0.01 2.06 0.01 0.37 0.11 0.09 0.07 0.05 0.03 71 409.6 9.5 382.2 9.8 29.3 3.4 18.2 3.8 10-1C-D R 62 0.01 1.98 0.01 0.34 0.11 0.09 0.07 0.05 0.03 43 396.3 15 347.7 9.7 27.5 3.3 14.1 3 10-1D-A I 57 0.01 2.12 0.01 0.4 0.11 0.09 0.07 0.05 0.03 52.9 376.3 12.6 305.4 9.9 26.9 3.2 12 4.6 10-1D-A I 57 0.01 2.11 0.01 0.39 0.11 0.09 0.07 0.05 0.03 64.4 385.6 11.5 359.9 9.4 26.9 3.4 13 1.8 10-1D-A R 66 0.01 1.85 0.01 0.3 0.1 0.09 0.07 0.05 0.03 46 449.6 12.4 399.5 9.7 29.2 3.7 12.9 4.3 1 C = core; I = Intermediate Zone; R = rim 2 [An = Ca / (Ca+Na+K)]*100
4.5 Discussion 4.5.0.1 Origin of Major Element Zoning and Resorption Surfaces Abrupt changes of 5 to > 10 mole % An and the presence of resorption surfaces amongst Unit 4 and 10 plagioclase phenocrysts indicates these crystals were variably exposed to magmas with which they were at a state of disequilibrium (e.g., Fig. 4.6, 4.7, Fig. 4.8, Fig. 4.9, Fig. 4.10). Injection of hot fresh magma into a crystallizing magma chamber can lead to partial resorption and subsequent growth of higher An zones, which is a feature that was noted for select crystals from each Unit (e.g., Fig. 4.6a,e,f,p, Fig. 4.7). An alternative scenario is that mo- bilization of crystals from mush piles within the magma chamber by convective overturn, avalanches of wall and roof debris, or magmatic stirring generated these features [83, 98]. Crystals growing in such mush layers are thermally and me- chanically insulated from the hottest portions of the magma chamber and can be out of equilibrium with magma in the chamber interior. Either of these processes may have operated to generate some or all of the observed dissolution and zoning patterns in Unit 4 and 10 plagioclase crystals. There are, however, systematic differences in the dominant zoning patterns between the Unit 4 and 10 basalt samples examined in this study. The Unit 4 basalt examined in this study contains a fairly even mixture or normal and reverse zoned crystals, which is a first order indication that crystals from different portions of the magmatic system were entrained during or before eruption. Deposition of plagioclase-rich crystal debris at one or more locations (walls, floors, etc.) in the magmatic system prior to eruption of the Unit 4 basalt is supported by the presence of plagioclase glomerocrysts, where after deposition the crystals were partially compacted to later be mobilized as cognate clusters of 206
Page 1 and 2:
TEXTURAL AND MICROANALYSIS OF IGNEO
Page 3 and 4:
TEXTURAL AND MICROANALYSIS OF IGNEO
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DEDICATION This work is dedicated t
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CHAPTER 2: MAGMA EVOLUTION REVEALED
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3.6.3.1 Crystal Population Origins
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FIGURES 1.1 Magma Chambers . . . .
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TABLES 2.1 MAJOR AND TRACE ELEMENT
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thus been debate within the volcano
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Cambrian schist) including a crysta
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explosive eruption vs. mild effusiv
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tiation (e.g., [84, 98]; Fig. 1.3).
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defined as having crystallinities b
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12 Figure 1.4: Large Igneous Provin
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distribution of crystal sizes (e.g.
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investigating magmatic evolution us
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length dispersive spectroscopy(WDS)
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microdrilling, a pre-cleaned square
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1.7.2 Detroit Seamount, Part of the
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lations. Reprocessing of intrusive
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nucleated homogenously and grew thr
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With accurate partition coefficient
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uniform composition of large volume
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Figure 2.2. Hand sample and thin se
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2.3.1 A Cogenetic Relationship Betw
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Figure 2.4. Stratigraphic section o
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Figure 2.5. Backscatter electron im
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studies of Kwaimbaita basalt by San
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42 Crystal Zone An (mol%) TABLE 2.1
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44 Crystal Zone An (mol%) 63R2 phen
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along the xenolith margins (e.g., F
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are more abundant in phenocrysts fr
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54 Crystal Zone 5 ML-X1 xenolith TA
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56 TABLE 2.2 Continued Crystal Zone
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Figure 2.7. Measured major and trac
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2.5.3.2 Trace Elements It is diffic
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Figure 2.9. Trace element ratio plo
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2.5.4 Resorption Features in Site 1
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should, however, be noted that in t
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2.6.1.2 An-rich OJP Plagioclase: In
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equivocally the roles of H2O, press
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ent magma requires significant clin
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tion driven plumes, or stirring by
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Yamashita, [123], and thus did not
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erally extensive crystal-mush netwo
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asalt at Site 1185 of ODP Leg 192 [
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CHAPTER 3 SHALLOW MAGMA EVOLUTION D
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magma compositions [23, 39, 98]. A
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Figure 3.2. Stratigraphy of basalts
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[118]. No volcaniclastic rocks were
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magmatic crystallization. Using the
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Figure 3.3. A cross polarized light
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3.4.5 Major and Trace Element Data
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3.4.6.1 Partition coefficients for
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3.5.1.2 Site 884 CSDs I measured pl
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Figure 3.5. Plagioclase CSDs of ODP
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106 TABLE 3.2 CSD RESULTS Sample OD
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ln (n) [mm -4 ] ln (n) [mm -4 ] 10
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ulation A crystals are unzoned (An6
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Figure 3.8. a) The majority of Site
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3.5.4.3 Site 1203 Unit 31 and Site
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3.5.5 Trace Elements 3.5.5.1 Measur
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Unit 31 > Site 884 Unit 8 (Table 3.
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3.6 Discussion 3.6.1 Evidence of Cr
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3.6.1.1 Site 1203 Alkalic Basalts a
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etween the different crystal popula
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Unit 14 and 31 magmas accumulated o
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sition is similar to parent magmas
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Sr - low La/Ce population A parent
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The Unit 31 plagioclase CSD is kink
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was dominated by late stage clinopy
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pressure, and growth of An-rich pla
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138 TABLE 3.3 PLAGIOCLASE PHENOCRYS
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140 TABLE 3.3 Continued Sample Zone
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Page 167 and 168: 154 TABLE 3.3 Continued Sample Zone
Page 187 and 188: KP has been done via drilling at 11
Page 189 and 190: and over time crustal wall-rocks be
Page 191 and 192: flow [33]. I selected a single samp
Page 193 and 194: 4.3.4 Major and Trace Element Data
Page 195 and 196: B) C) parafilm splash guard A) tape
Page 197 and 198: of these elements are the better co
Page 199 and 200: 5 mm 5 mm Figure 4.4. Cross polariz
Page 201 and 202: 4.4.2 Electron Probe Microanalysis
Page 203 and 204: An (mol %) An (mol %) An (mol %) An
Page 205 and 206: study exhibit their highest An at t
Page 207 and 208: 4.4.3 LA-ICP-MS - Trace Elements An
Page 209 and 210: 87 86 Sr/ SrI = 0.705722(8) Ba/Sr =
Page 211 and 212: and Rb (Fig. 4.11d,e). 4.4.3.3 Yttr
Page 213 and 214: Sr (ppm) Y (ppm) La (ppm) Ce (ppm)
Page 215 and 216: Unit 4 plagioclase rims plagioclase
Page 217: 204 TABLE 4.4 UNIT 4 PLAGIOCLASE PA
Page 221 and 222: 4.5.0.2 Insights from Trace Element
Page 223 and 224: that other factors influenced the a
Page 225 and 226: C A/B / D A/B C A/B / D A/B Unit 4
Page 227 and 228: Magma chambers tend to form at hori
Page 229 and 230: whole-rock basalt data. Cumulate xe
Page 231 and 232: over short time spans but may be ea
Page 233 and 234: lowing initial Elan Bank magma empl
Page 235 and 236: BIBLIOGRAPHY 1. C. Allegre, A. Prov
Page 237 and 238: 22. B. Charlier, J. Davidson, O. Ba
Page 239 and 240: 46. J. Fitton and M. Godard, Origin
Page 241 and 242: 68. M. Higgins, Measurement of crys
Page 243 and 244: 89. J. Longhi, D. Walker and J. Hay
Page 245 and 246: 100 of Geophysical Monograph, pages
Page 247 and 248: 129. J. Tarduno, W. Sliter, L. Kroe
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