TEXTURAL AND MICROANALYSIS OF IGNEOUS ROCKS: TOOLS ...

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A) B) 19∞15' N 19∞20' Mauna Iki Kamakalauka 19∞25' Kamakaiawaena Summit Magma Reservoir Southwest Rift Zone 155∞20' 19∞30' Kilauea Caldera Halemaumau Keanakakoi Kilauea Iki Devil's Throat Pauahi Aloi East Rift Zone Mauna Ulu Alae 155∞10' Primary Conduit Makaopuhi Napau Pu'u Kamoamoa Pu'u O'o 0 Pu'u Kauka Heiheiahulu Pu'u Kiai Kalalua Volcanic Shield Oceanic Crust Upper Mantle 3 km 155∞05' 30 35 40 25 0 20 15 3 km Pacific Ocean Figure 1.1. Graphic examples of relatively simple versus complex magma chamber models for the A) Ontong Java Plateau (from Sano and Yamashita [123]) constructed based primarily upon geochemical data and B) Kilauea (from Ryan [122]) using seismic data. Which model is more accurate? 3 Pu'u Kahaualea 10 155∞00' W 5 Depth (km) 0
Cambrian schist) including a crystal with a narrow ∼ 520 Myr core region and ∼ 300 Kyr rim grown in the rhyolitic host magma. These types of findings are of profound significance, as they provide robust insights into the fundamental phys- ical processes and chemical consequences of crustal assimilation. Although zircon is a refractory mineral, this type crystal of inheritance is not limited to zircon and may be exhibited by minerals that are stable on the basaltic liquidus over a wide range of magmatic temperatures and pressures (e.g., plagioclase). Crystal popula- tions and individual crystals not totally consumed by magmatic processes indeed provide records of magma chemistry and magma chamber dynamics beyond what can be learned through whole-rock studies alone. The complexity of shallow magma evolution has also been highlighted by quantitative textural studies, most notably in crystal size distribution (CSD) studies (e.g.,[67, 68, 96, 97]). Crystal size distributions yield information about crystal nucleation and growth conditions as well as open system processes like crystal accumulation or magma mixing [20, 96]. Higgins [67] showed that the proportions of mixing members can be well estimated from CSD data. Crystal size distributions provide a means to qualitatively assess whether certain processes may have taken place (e.g., magma mixing, crystal resorption/removal, or crystal accumulation), as well as provide a quantitative method for determining magmatic residence times and calculation of end-member mixing proportions [67]. A collective goal within the volcanology and petrology community is to under- stand the timing and dynamics of shallow magma evolution. Meeting this goal serves not only to answer fundamental scientific questions but also includes an im- portant human factor. Magma evolution that takes place in shallow subterranean chambers has a dramatic influence on when and how a volcano will erupt (e.g., 4
Page 1 and 2: TEXTURAL AND MICROANALYSIS OF IGNEO
Page 3 and 4: TEXTURAL AND MICROANALYSIS OF IGNEO
Page 5 and 6: DEDICATION This work is dedicated t
Page 7 and 8: CHAPTER 2: MAGMA EVOLUTION REVEALED
Page 9 and 10: 3.6.3.1 Crystal Population Origins
Page 11 and 12: FIGURES 1.1 Magma Chambers . . . .
Page 13 and 14: TABLES 2.1 MAJOR AND TRACE ELEMENT
Page 15: thus been debate within the volcano
Page 19 and 20: explosive eruption vs. mild effusiv
Page 21 and 22: tiation (e.g., [84, 98]; Fig. 1.3).
Page 23 and 24: defined as having crystallinities b
Page 25 and 26: 12 Figure 1.4: Large Igneous Provin
Page 27 and 28: distribution of crystal sizes (e.g.
Page 29 and 30: investigating magmatic evolution us
Page 31 and 32: length dispersive spectroscopy(WDS)
Page 33 and 34: microdrilling, a pre-cleaned square
Page 35 and 36: 1.7.2 Detroit Seamount, Part of the
Page 37 and 38: lations. Reprocessing of intrusive
Page 39 and 40: nucleated homogenously and grew thr
Page 41 and 42: With accurate partition coefficient
Page 43 and 44: uniform composition of large volume
Page 45 and 46: Figure 2.2. Hand sample and thin se
Page 47 and 48: 2.3.1 A Cogenetic Relationship Betw
Page 49 and 50: Figure 2.4. Stratigraphic section o
Page 51 and 52: Figure 2.5. Backscatter electron im
Page 53 and 54: studies of Kwaimbaita basalt by San
Page 55 and 56: 42 Crystal Zone An (mol%) TABLE 2.1
Page 57 and 58: 44 Crystal Zone An (mol%) 63R2 phen
Page 63 and 64: along the xenolith margins (e.g., F
Page 65 and 66: are more abundant in phenocrysts fr
Page 67 and 68:
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
Page 109 and 110:
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
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
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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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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
Page 193 and 194:
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
Page 237 and 238:
22. B. Charlier, J. Davidson, O. Ba
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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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