title of the thesis - Department of Geology - Queen's University

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$Fayek & Kyser 2000 uraninite fractionations.pdf - Queen's University$

from the Leo Pargil dome also reveal the exhumation and juxtaposition of mid-crustal rocks against the TSS via sustained normal displacement along the west-dipping western flank of the dome (Thiede et al., 2006). Chronological constraints suggest dome exhumation initiated in a setting linked to orogen-parallel extension by 16 Ma (Thiede et al., 2006), and potentially post 19 Ma (Leech, 2008). 1.4 This study The purpose of this study is to characterize the cessation of south-directed mid-crust extrusion and the onset of orogen-parallel deformation. The area selected to perform this study is located within the upper Karnali valley of northwestern Nepal (Figs. 1.2b, 2.2b), where a northwest-striking, strike-slip-dominated shear zone defines the upper contact and cuts obliquely across the GHS (Murphy and Copeland, 2005). 1.4.1 Geology of northwestern Nepal and the upper Karnali valley The upper Karnali valley lies to the northwest of the village of Simikot, located in farnorthwestern Nepal (Fig. 1.2b). The regional geological framework of the area was pioneered by Fuchs (1977) and Shrestha (1987), and subsequently refined by Murphy and Copeland (2005), Robinson et al. (2006), and Yakymchuk and Godin (2012). A compilation of data reveal a high-strain south-dipping contact, which juxtaposes weakly deformed and metamorphosed TSS over strongly deformed, high-metamorphic grade GHS (Fig. 1.2b; Murphy and Copeland, 2005). This lithotectonic relationship is consistent with the STDS, however the kinematics along the high-strain zone are not. Well-developed down-dip mineral elongation lineations indicating a significant dip-slip component are expected along the STDS in order to juxtapose units of contrasting metamorphic grades. Contrastingly, shallow ESE- WNW lineations are observed along the high-strain zone, indicating a dominant strike-slip sense 9
of shear (Murphy and Copeland, 2005). Additionally, this high strain zone is not limited to the TSS-GHS interface, but also cuts obliquely across the GHS and possibly into the Lesser Himalayan sequence to the southwest (Fig. 1.2b; Murphy and Copeland, 2005). These observations, in conjunction with middle Miocene chronologic constraints, prompted the interpretation that this contact is a component of the Gurla Mandhata-Humla fault system (GMH), a northwest-striking shear zone associated with orogen-parallel extension, postdating southdirected extrusion of the GHS (Murphy and Copeland, 2005). The presence of the GMH strike-slip-dominated fault system atop and along the GHS provides an ideal geologic context in which to investigate the relationship between south-directed extrusion of the GHS and orogen-parallel extension. 1.4.2 Purpose of this study The purpose of this study is to characterize the transition from cessation of south-directed extrusion of the GHS to onset of orogen-parallel extension. Results from this thesis clarify this fundamental Himalayan tectonic transition and provide insight on large-scale processes governing the evolution of large, hot collisional orogens. This problem is approached by addressing the following questions: 1. What are the relationships between the structures, kinematics, temperatures, and timing of deformation associated with south-directed extrusion of the GHS and orogen-parallel extension 2. What do these data imply for tectonic processes governing (1) south-directed mid-crustal flow, (2) orogen-parallel extension, and (3) orogen-wide evolution of the Himalayan-Tibetan orogen 10
Page 1 and 2: FROM CESSATION OF SOUTH-DIRECTED MI
Page 3 and 4: Abstract Field mapping and, structu
Page 5 and 6: Co-Authorship This thesis is my own
Page 7 and 8: Table of Contents Abstract ........
Page 9 and 10: 4.1 Introduction ..................
Page 11 and 12: Figure 4.3 Microscale CPO variabili
Page 13 and 14: Abbreviations Mineral Biotite Calci
Page 15 and 16: Figure 1.1 Color relief map of the
Page 17 and 18: 1.2 Evolution of the Himalayan-Tibe
Page 19 and 20: Figure 1.3 Structures in the Himala
Page 21: the various models. However, this a
Page 25 and 26: Chapter 4 outlines proposed future
Page 27 and 28: indicated by symmetric high-tempera
Page 29 and 30: The second phase of middle Miocene
Page 31 and 32: 2.3 Geologic Setting 2.3.1 Himalaya
Page 33 and 34: 2.4 Geology of the upper Karnali Va
Page 36 and 37: Figure 2.3 Lithotectonic map and si
Page 38 and 39: the main shear zone fabric. The lit
Page 40 and 41: South of the interface, the TSS is
Page 42 and 43: WNW Figure 2.6 Representative struc
Page 44 and 45: Figure 2.7 Representative structure
Page 46 and 47: distribution of dextral and sinistr
Page 48 and 49: al., 1986; Mainprice et al., 1986).
Page 50 and 51: Figure 2.9 Summary of CPO post-acqu
Page 52: a c a c Figure 2.10 Summary of quar
Page 56 and 57: Sample HK131A is a high-strain quar
Page 58 and 59: constriction, where rhomb slip domi
Page 60 and 61: ± 50°C (Law et al., 2004). Furthe
Page 62 and 63: Figure 2.14 (a) Photomicrograph of
Page 64 and 65: Figure 2.15 Summary of lithotectoni
Page 66 and 67: elationships, these data constrain
Page 68 and 69: primary reference material, “4409
Page 70 and 71: Figure 2.16 - continued. 57
Page 72:
monazite grains are aligned paralle
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Analysis Position Pb U Th Th/U 207
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Analysis Position HK117A Pb U Th Th
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are derived from intensely deformed
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Samples KH10, HK102a, HK105, HK115,
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the intralaboratory standard (MAC-8
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Figure 2.18 - continued. 76
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espectively. Note that the plateaus
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Figure 2.19 Plots of muscovite cool
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Figure 2.20 Summary of results from
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(2) Previously published chronologi
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Figs. 2.7b,d, 2.15) is locally over
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Thermochronology of muscovite grain
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Figure 2.21 - continued - Box (3) r
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92 Figure 2.22 (a) Location of stud
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is little data to support both afor
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Figure 2.23 Numerical model of modi
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The second phase is associated with
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yr Figure 3.1 Numerical model of Co
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phenomena are consistent with ongoi
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towards the topographic front of th
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Chapter 4 Microstructural analyses:
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a c a c Figure 4.1 Summary of quart
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Figure 4.2 Results of study by Toy
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factors on the formation of differe
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1987; Simpson and De Paor, 1993, 19
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2009). Furthermore, there is rising
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Figure 4.5 Simplified set up of ana
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Appendix A Station locations and st
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Station Latitude Longitude Elevatio
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Station Latitude Longitude KH019 KH
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HK 140 - Non-processed EBSD data 12
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HK 131A - U-Stage data 128
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HK 131A - Non-processed EBSD data 1
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HK 139D - Non-processed EBSD data 1
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HK 105A - U-Stage data 134
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HK 105A - Processed EBSD data (e.g.
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HK 125 - Processed EBSD data (e.g.
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Page 159 and 160:
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HK 124B2 - Processed EBSD data (e.g
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KH18a - Monazite 1 150
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Page 171 and 172:
Page 173 and 174:
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Page 179 and 180:
HK109 - Thin section * For HK109_mo
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U Th 4 3 2 1 5 10 9 11 7 8 6 Nd Y 1
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HK109 - Monazite 3 170
Page 185 and 186:
U SL CP 172
Page 187 and 188:
U Th SL 174
Page 189 and 190:
Page 191 and 192:
U Nd CP 178
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U Nd Th 180
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Page 197 and 198:
Y Nd U Th 184
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U Th SL 186
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CP Nd 2 3 4 6 5 1 Y P 190
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U Th SL 192
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CP Nd Y P 196
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U Th SL 198
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HK117a - Thin section 200
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11 12 10 8 9 13 14 15 7 6 4 2 5 3 1
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4 1 5 9 10 2 11 6 16 3 7 17 14 8 18
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9 8 7 10 6 5 4 3 2 1 206
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7 6 8 9 13 14 15 4 5 1 2 3 10 11 12
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210
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5 4 9 6 7 8 3 2 1 10 212
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2 3 4 1 6 7 8 9 10 5 214
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Holdsworth, R.E., McCaffrey, K.J.W.
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Cottle, J. M., Jessup, M. J., Newel
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Ghosh, S.K., and Ramberg, H. 1976.
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Hodges, K.V., and Silverberg, D.S.
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Kohn, M.J. 2008. P-T-t data from ce
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Means, W. D., Hobbs, B. E., Lister,
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Prior, D.J. 2009. EBSD in the earth
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Caledonides. In, S. Sengupta (Ed.),
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Yakymchuck, C., 2010. Tectonometamo
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