sgr ms thesis - University of Maine

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A 1.E+04 1.E+03 N 1.E+02 1.E+01 Modification of Clast Size Distribution produced by modeled transient melt progression Unexposed 1 second 5 seconds 20 seconds 50 seconds 100 seconds 200 seconds 500 seconds 1000 seconds 1.E+00 B cumulate frequency 100 10 0.01 0.1 r (cm) 1 10 Evolution of clast size distribution caused by modeled transient melt progression t = 4 Bifractal: D = 2, 1.5 t = 100 Non-Fractal t = 0 D = 2.5 t0 t4 100 1 1 10 100 radius (pixels) Figure 7.5. The evolution of clast size distribution with progressive thermal exposure. A) A fabricated CSD with D s = 3, T c = 650°C and subjected to T i = 900°C, 34% magma: small clast populations quickly melt, evolving from a fractal to non-fractal distribution of clast sizes. B) CSD results from chosen time steps from the outcrop model used in Figure 7.3; T i = 900°C, T c = 650°C. 107
7.4. Thermal-Induced Fracture Field observations, specifically the late stage fractures in diorite clasts, show that late stage fracturing occurred with the introduction of magma into the Shatter Zone. Clasts when exposed to magma undergo rapid heating and a transient, non-uniform temperature distribution develops within them. Most materials tend to volumetrically expand when heated (e.g. Clarke, 1998). No critical stresses would be induced if the material under uniform heating is free to expand. Non-uniform volume expansion in a constricted solid, however, leads to stress buildup and potential fracture propagation. In a clast of irregular shape subjected to surface heating, temperatures in the interior and in the root regions of the corners are lower than those at the surfaces. Tensile stresses thus develop in these regions of non-uniform expansion as the materials there are stretched by the hotter surface materials, causing potential corner break-off. Thermal fracture could be significant for CSD because 1) it directly produces new clasts from the breakdown of old ones in a pattern different from explosion-derived populations, and 2) it increases surface area of clasts that could enhance the speed of temperature homogenization. A one-dimensional equation is used to approximate the required temperature gradient necessary to cause tensile fracture (Manson, 1953) (7.5) where is Young’s Modulus, is Poisson’s ratio, is the coefficient of linear thermal expansion, is the temperature difference experienced by the body, and is the thermally induced tensile stress. An average rock can fracture 108
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FRACTAL ANALYSIS AND THERMAL-ELASTI
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LIBRARY RIGHTS STATEMENT In present
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emplacement of mafic magma, resulti
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© 2011 Samuel Geoffrey Roy All Rig
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TABLE OF CONTENTS ACKNOWLEDGEMENTS
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5.3.5. Clast Circularity Analysis .
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LIST OF FIGURES Figure 2.1. Figure
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LIST OF TABLES Table 6.1. Table 7.1
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subvolcanic magmatic systems, the l
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Chapter 2 GEOLOGIC SETTING 2.1. Reg
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Somesville granite suite to the wes
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Biotite is metamorphic in origin, a
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Chapter 3 PHYSICAL DESCRIPTION OF S
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thinned lithosphere allows for part
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A B C Figure 3.1. Formation of a la
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1997; Branney and Kokelaar, 1998; J
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Effusive-Type Eruption max 10 0 - 1
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magma quickly intrudes the develope
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Piston Downsag Piecemeal Funnel Tra
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fragmentation, and thermal energy h
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Chapter 4 THERMAL FRAMEWORK FOR CON
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contrast, conduction is heat transf
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A B Grt C Grt D Crd Crd E 1 mm F Cr
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! ! ! ! Biotite Zone Garnet Zone !
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4.3.1. Model Setup The model is use
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to make a “hockey puck” style g
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t = 0s t = 1E11 t = 1E12s t = 1E13s
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850 750 650 550 450 400m Into Chamb
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approximately 140m thinner. The Sha
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Chapter 5 ROCK MECHANICS AND THE FR
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A β δ σ 1 σ 3 σ t c a σ 1 σ
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friction along the closed crack sur
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h h/2 h/4 Figure 5.2. A cube displa
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where N (≥r) is the count of clas
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to place a minimum size limit when
Page 71 and 72: moment of sudden fracture tip failu
Page 73 and 74: produced results in a self-similar
Page 75 and 76: 13 ln(area) (pixels) 12 11 10 9 ln(
Page 77 and 78: eaction processes were involved in
Page 79 and 80: Chapter 6 ANALYSIS AND RESULTS The
Page 81 and 82: Type 1 Type 2 500 m N Type 1 Type 2
Page 83 and 84: A B Figure 6.3. Type 2 Shatter Zone
Page 85 and 86: A B Figure 6.5. Centimeter-scale bo
Page 87 and 88: A B Figure 6.6. Brecciation texture
Page 89 and 90: The final breccia classified in thi
Page 91 and 92: esolution images of each box were s
Page 93 and 94: Clast circularity data were produce
Page 95 and 96: A 1000 Clast Size Distribu on: Type
Page 97 and 98: diorite dike with D s = 2.62 and R
Page 99 and 100: 6.3.3. Clast Circularity Analysis (
Page 101 and 102: with decreasing clast size in all T
Page 103 and 104: possibilities as postulated previou
Page 105 and 106: Chapter 7 MECHANISMS FOR SECONDARY
Page 107 and 108: magma. To prove the viability of th
Page 109 and 110: mesh to better evaluate large therm
Page 111 and 112: consistent with Type 3 breccias. Th
Page 113 and 114: A temperature versus time plot was
Page 115 and 116: Dimensionless time 0 0.05 0.1 0.15
Page 117 and 118: Figure 7.4 displays model results f
Page 119 and 120: thermal model ignores advection of
Page 121: Zone experienced a relatively weake
Page 125 and 126: Metapelite/hornfels Diorite dike E
Page 127 and 128: 7.4.2. Results and Discussion COMSO
Page 129 and 130: This thermal fracture model explain
Page 131 and 132: disaggregation of Bar Harbor clasts
Page 133 and 134: REFERENCES Acocella, V. (2007). Und
Page 135 and 136: Billen, M.I. and Gurnis, M. (2001).
Page 137 and 138: Clarke, D. B. (2007). Assimilation
Page 139 and 140: Fisher, R.V. (1960). Classification
Page 141 and 142: Hartmann, W.K. (1969). Terrestrial,
Page 143 and 144: Johnson, S.E.; Paterson, S.R.; Tate
Page 145 and 146: Mandelbrot, B.B. (1967). How long i
Page 147 and 148: Oliver, N.H.S.; Rubenach, M.J.; Fu,
Page 149 and 150: Schoutens, J.E. (1979). Empirical A
Page 151 and 152: Wiebe, R.; Holden, J.; Coombs, M.;
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