sgr ms thesis - University of Maine

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3.4. Emplacement and eruptive history of the Cadillac Mountain Intrusive Complex The Cadillac Mountain Granite formed by crustal thinning in an extensional terrane (Wiebe et al., 1997a). The intrusive complex provides a record of episodic basaltic magma injection before, during, and after emplacement and crystallization of the granitic pluton. Injection sequences are recorded in the gabbro-diorite-granite sheets at the base of the complex. Wiebe (1994) hypothesized that the formation of the Cadillac Mountain Granite pluton enhanced the potential to attract and trap basaltic dikes at the base of the chamber. Continuous replenishment of the reservoir extended the life of the pluton, and the steady addition of thermal energy drove convection (Chapman, 1962). Based on the prevalence of enclaves throughout the Cadillac Mountain Granite, there was some amount of granitic and basaltic mixing during convection (Wiebe et al., 1997b). The continued addition of thermal energy and volumetric expansion by basaltic replenishment were also the likeliest triggers for reservoir overpressurization and subsequent volcanic eruption (e.g. Wiebe, 1994; Seaman et al., 1999; Annen and Sparks, 2002). 25
Chapter 4 THERMAL FRAMEWORK FOR CONTACT METAMORPHISM To fully understand the development of the Shatter Zone, it is first necessary to determine the characteristics of contact metamorphism within the unit. In this chapter, I discuss how thermal energy drives metamorphism along the contact between the Cadillac Mountain Granite and Bar Harbor Formation, and how modeling and isograd data can potentially tell us about the condition of the wall rock before the formation of the Shatter Zone. Important constraints are discussed in order to develop a useful model for intrusive thermal behavior. I use a conductive heat transfer-based, instantaneous single intrusion model. Although the model is a simplified version of the intrusion complex, it provides endmember results for the true thickness of the metamorphic zones, the dominant heat transfer mode, and the effect of extended chamber activity and wall rock brecciation on contact metamorphism. I find that the model is a good first order approximation for contact metamorphism in the Shatter Zone, but convective heat transfer, extended pluton activity, and wall rock brecciation are all important factors that have been ignored here. 4.1. Characteristics of Contact Metamorphism Contact metamorphism involves a balance of heat transfer (Bergantz, 1991; Labotka, 1991): as the wall rock heats up from contact, the intrusion must cool down by a proportional amount. Contact metamorphism is limited to a 26
Page 1 and 2: FRACTAL ANALYSIS AND THERMAL-ELASTI
Page 3 and 4: LIBRARY RIGHTS STATEMENT In present
Page 5 and 6: emplacement of mafic magma, resulti
Page 7 and 8: © 2011 Samuel Geoffrey Roy All Rig
Page 9 and 10: TABLE OF CONTENTS ACKNOWLEDGEMENTS
Page 11 and 12: 5.3.5. Clast Circularity Analysis .
Page 13 and 14: LIST OF FIGURES Figure 2.1. Figure
Page 15 and 16: LIST OF TABLES Table 6.1. Table 7.1
Page 17 and 18: subvolcanic magmatic systems, the l
Page 19 and 20: Chapter 2 GEOLOGIC SETTING 2.1. Reg
Page 21 and 22: Somesville granite suite to the wes
Page 23 and 24: Biotite is metamorphic in origin, a
Page 25 and 26: Chapter 3 PHYSICAL DESCRIPTION OF S
Page 27 and 28: thinned lithosphere allows for part
Page 29 and 30: A B C Figure 3.1. Formation of a la
Page 31 and 32: 1997; Branney and Kokelaar, 1998; J
Page 33 and 34: Effusive-Type Eruption max 10 0 - 1
Page 35 and 36: magma quickly intrudes the develope
Page 37 and 38: Piston Downsag Piecemeal Funnel Tra
Page 39: fragmentation, and thermal energy h
Page 43 and 44: contrast, conduction is heat transf
Page 45 and 46: A B Grt C Grt D Crd Crd E 1 mm F Cr
Page 47 and 48: ! ! ! ! Biotite Zone Garnet Zone !
Page 49 and 50: 4.3.1. Model Setup The model is use
Page 51 and 52: to make a “hockey puck” style g
Page 53 and 54: t = 0s t = 1E11 t = 1E12s t = 1E13s
Page 55 and 56: 850 750 650 550 450 400m Into Chamb
Page 57 and 58: approximately 140m thinner. The Sha
Page 59 and 60: Chapter 5 ROCK MECHANICS AND THE FR
Page 61 and 62: A β δ σ 1 σ 3 σ t c a σ 1 σ
Page 63 and 64: friction along the closed crack sur
Page 65 and 66: h h/2 h/4 Figure 5.2. A cube displa
Page 67 and 68: where N (≥r) is the count of clas
Page 69 and 70: 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 and 122:
Zone experienced a relatively weake
Page 123 and 124:
7.4. Thermal-Induced Fracture Field
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Metapelite/hornfels Diorite dike E
Page 127 and 128:
7.4.2. Results and Discussion COMSO
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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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