TEXTURAL AND MICROANALYSIS OF IGNEOUS ROCKS: TOOLS ...

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115 A) An (mol %) pop. A cores pop. B cores Site 1203 Unit 3 Ab 50 (mol %) Or 50 (mol %) B) An (mol %) An (mol %) pop. A cores pop. B cores Site 1203 Unit 14 Ab 50 (mol %) Or 50 (mol %) C) pop. A cores pop. B cores Site 884 Unit 8 pop. B cores Site 1203 Unit 31 (and Site 884 Unit 8) Ab 50 (mol %) Or 50 (mol %) Mg # Ti (ppm) An (mol %) Figure 3.9. a) The cores of Site 1203 Unit 3 population A and B crystals overlap, but population A crystals extend to much lower An. b) Unit 14 and Unit 31 (c) population B crystals extend up to An87, which is distinct from population A crystals in each Unit. d) There is little obvious variation of Mg# with An content, between crystal populations, or between Units. e) A strong correlation of Ti abundance with An content was observed, although correlations appears to weaken considerably at An > 70. Correlation coefficient for Unit 3 Ti vs. An R2 = 0.79, Unit 14 R2 = 0.80, and Unit 31 R2 = 0.39. D) E)
3.5.5 Trace Elements 3.5.5.1 Measured Compositions Trace element abundances measured by LA-ICP-MS in plagioclase crystals from each Unit are reported in table 3.3 and illustrated in figure 3.10. Yttrium, Sr, La, Nd, Sm, and Eu abundance exhibit little or no correlation with An content in figure 3.10. More prominent negative correlations of Ba and Ce abundance with An content are apparent if figures 3.10c,e, although these correlations appear to be most significant at An contents < An70. In the An80−87 range, which is dominated by the interiors of population B crystals from each Unit, Unit 14 population B crystals trend to highest Sr abundance, Unit 31 crystals have the lowest Sr of the three Site 1203 Units I examined, and the Site 884 Unit 8 crystals have lower abundances Sr than all Site 1203 crystals (Fig. 3.10). In terms of Y, Sm, Nd, and Eu all crystals in the An80−87 range overlap. It should be noted, however, that the Site 884 Unit 8 crystals tend to have the lowest abundances of these elements and Sm low enough to be below analytical detection limits. Lanthanum and Ce exhibit similar patterns in crystal zones in the An80−87 range, where Unit 31 crystals are the most La and Ce depleted of the Site 1203 samples and the Site 884 Unit 8 crystals have notably lower La and Ce abundances (Fig. 3.10d,e) 3.5.5.2 Inferred Parent Magma Compositions I inverted the compositions of magmas in equilibrium with the crystals at different periods during their growth. The calculated parent magma compositions and the partition coefficients used for inversion are listed in table 3.4. Rare earth element, Ti, Ba, and Sr abundance in parent magmas of the four Units I examined exhibit the following general trend of decreasing abundance: Unit 3 ≅ Unit 14 > 116
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TEXTURAL AND MICROANALYSIS OF IGNEO
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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
Page 77 and 78: 2.5.3.2 Trace Elements It is diffic
Page 79 and 80: Figure 2.9. Trace element ratio plo
Page 81 and 82: 2.5.4 Resorption Features in Site 1
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Page 85 and 86: 2.6.1.2 An-rich OJP Plagioclase: In
Page 87 and 88: equivocally the roles of H2O, press
Page 89 and 90: ent magma requires significant clin
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Page 93 and 94: Yamashita, [123], and thus did not
Page 95 and 96: erally extensive crystal-mush netwo
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Page 99 and 100: CHAPTER 3 SHALLOW MAGMA EVOLUTION D
Page 101 and 102: magma compositions [23, 39, 98]. A
Page 103 and 104: Figure 3.2. Stratigraphy of basalts
Page 105 and 106: [118]. No volcaniclastic rocks were
Page 107 and 108: magmatic crystallization. Using the
Page 109 and 110: Figure 3.3. A cross polarized light
Page 111 and 112: 3.4.5 Major and Trace Element Data
Page 113 and 114: 3.4.6.1 Partition coefficients for
Page 115 and 116: 3.5.1.2 Site 884 CSDs I measured pl
Page 117 and 118: Figure 3.5. Plagioclase CSDs of ODP
Page 119 and 120: 106 TABLE 3.2 CSD RESULTS Sample OD
Page 121 and 122: ln (n) [mm -4 ] ln (n) [mm -4 ] 10
Page 123 and 124: ulation A crystals are unzoned (An6
Page 125 and 126: Figure 3.8. a) The majority of Site
Page 127: 3.5.4.3 Site 1203 Unit 31 and Site
Page 131 and 132: Unit 31 > Site 884 Unit 8 (Table 3.
Page 133 and 134: 3.6 Discussion 3.6.1 Evidence of Cr
Page 135 and 136: 3.6.1.1 Site 1203 Alkalic Basalts a
Page 137 and 138: etween the different crystal popula
Page 139 and 140: Unit 14 and 31 magmas accumulated o
Page 141 and 142: sition is similar to parent magmas
Page 143 and 144: Sr - low La/Ce population A parent
Page 145 and 146: The Unit 31 plagioclase CSD is kink
Page 147 and 148: was dominated by late stage clinopy
Page 149 and 150: pressure, and growth of An-rich pla
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166 TABLE 3.4 Continued Sample Zone
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KP has been done via drilling at 11
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and over time crustal wall-rocks be
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flow [33]. I selected a single samp
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4.3.4 Major and Trace Element Data
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B) C) parafilm splash guard A) tape
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of these elements are the better co
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5 mm 5 mm Figure 4.4. Cross polariz
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4.4.2 Electron Probe Microanalysis
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An (mol %) An (mol %) An (mol %) An
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study exhibit their highest An at t
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4.4.3 LA-ICP-MS - Trace Elements An
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87 86 Sr/ SrI = 0.705722(8) Ba/Sr =
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and Rb (Fig. 4.11d,e). 4.4.3.3 Yttr
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Sr (ppm) Y (ppm) La (ppm) Ce (ppm)
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Unit 4 plagioclase rims plagioclase
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204 TABLE 4.4 UNIT 4 PLAGIOCLASE PA
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4.5 Discussion 4.5.0.1 Origin of Ma
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4.5.0.2 Insights from Trace Element
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that other factors influenced the a
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C A/B / D A/B C A/B / D A/B Unit 4
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Magma chambers tend to form at hori
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whole-rock basalt data. Cumulate xe
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over short time spans but may be ea
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lowing initial Elan Bank magma empl
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BIBLIOGRAPHY 1. C. Allegre, A. Prov
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22. B. Charlier, J. Davidson, O. Ba
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46. J. Fitton and M. Godard, Origin
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68. M. Higgins, Measurement of crys
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89. J. Longhi, D. Walker and J. Hay
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100 of Geophysical Monograph, pages
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129. J. Tarduno, W. Sliter, L. Kroe
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