[Society of Earth Scientists Series] Structural Geometry of Mobile Belts of the Indian Subcontinent ||

This book summarizes the latest research on the structural geology of the mobile belts of the Indian subcontinent including the Himalayas, NE Himalayas, Bangladesh thrust belt, Andaman subduction zone, the Aravalli‐Delhi, the Central India Tectonic Zone, the Singhbhum, the Eastern Ghats and the Southern granulite terrane. It offers essential information on deformational structures in the mobile belt, such as folding patterns, the character of the shear zone, shear strain analysis, and faults, as well as fault zone rocks. The findings presented here are based on field observations, mapping, sampling and analysis work (e.g. petrographic studies), as well as limited geochemical and geochronological analysis to support the findings. A discussion on the structural evolution of these mobile belts and their connections with other belts rounds out the coverage. Foreword 6 Preface 7 Contents 9 About the Editors 11 Timing of South Delhi Orogeny: Interpretation from Structural Fabric and Granite Geochronology, Beawar-Rupnagar-Babra Area, Rajasthan, NW India 13 1 Introduction 14 2 Geological Setting 15 3 Methodology 17 4 Result 18 4.1 Lithology 18 4.2 Structures 22 5 Discussion 24 5.1 Deformation of the Rocks of the South Delhi Terrane (SDT) 24 5.2 Deformation Fabric and Previous Geochronology of Granite, and Timing of the South Delhi Orogeny 26 5.3 South Delhi Orogeny in Relation to Global Orogeny 27 6 Conclusions 28 References 29 Deformation in the Aravalli Supergroup, Aravalli-Delhi Mobile Belt, NW India and Tectonic Significance 35 1 Introduction 36 2 Geological Setting 38 3 Analytical Methods 42 3.1 Sample Collection and Sample Preparation 42 3.2 Microstructural Analyses of Quartz Fabrics 42 3.3 SEM-Based Automated Mineralogy (MLA) and EPMA 43 4 Results 46 4.1 Structural and Lithological Characteristics 46 4.2 Garnet Mineral Chemistry and Geothermobarometry 49 4.3 Quartz Microstructural Fabrics 49 5 Discussion and Interpretation 53 6 Conclusions 60 References 61 Evolution of the “Central Indian Tectonic Zone”: A Critique Based on the Study of the Sausar Belt 68 1 Introduction 68 2 Review of Ideas Regarding Evolution of the “CITZ” and Significance of the “Satpura Orogenic Trend” 72 2.1 Spatio-Temporal Relations 72 2.2 Location and Geometry of the Subduction Zone 73 2.3 Summary 75 3 Deformation Pattern of Different Domains of CITZ and Its Tectonic Implication 76 3.1 Deformation in the Sausar Belt in the Western Domain of the CITZ 76 3.2 Structural Evolution of the Chhotanagpur Complex in the Eastern Domain of CITZ 88 4 Spatio-Temporal Correlation of Different Domains of the CITZ 89 5 Discussion 91 5.1 Tectonic Evolution of CITZ 91 5.2 Dip of Subduction Boundary and Position of the Suture 94 6 Conclusions 95 References 96 Tectonic Development of the Bengal Basin in Relation to Fold-Thrust Belt to the East and to the North 101 1 Introduction 101 2 Tectonic Settings 104 2.1 Geological Settings 104 2.2 Tectonic Evolution 104 3 Methodology 106 4 Result and Discussion 106 4.1 Result 106 4.2 Discussion 108 5 Conclusion 115 References 115 Structural Imprints of Andaman Accretionary Prism and Its Tectonic Relation with Ophiolite Belt of Indo-Burma Ranges 120 1 Introduction 121 2 Geological Setting 122 3 Deformation Structures of Andaman Accretionary Prism 124 3.1 Folds 124 3.2 Thrust 125 3.3 Strike-Slip/Normal Faults 126 4 Discussion 126 4.1 Evolution of Andaman Accretionary Prism 126 4.2 Tectonic Correlation Between Andaman Ophiolite with Other Ophiolites of IBR 129 4.3 Nature of the Crust of Andaman and IBR 133 4.4 Volcanic Arc of Andaman and IBR Region 134 5 Conclusions 134 References 135 Two and Three-Dimensional Structural Modelling of Central Kohat Plateau, Northwestern Himalaya, Pakistan 140 1 Introduction 141 2 Tectonic Setting and Stratigraphy of the Study Area 144 3 Methodology 145 3.1 Reconnaissance and Travers Selection 145 3.2 Field Data Collection 145 3.3 Remote Sensing 146 3.4 Surface Geological Map Construction 146 3.5 Structural Study 146 3.6 Two and Three Dimensional Structural Modelling 147 3.7 Stress Analysis 148 4 Results 148 4.1 Surface Geology 148 4.2 Two-Dimensional Structural Modelling 148 4.3 Three-Dimensional Structural Modelling 154 4.4 Stress Analysis of the Area 155 5 Discussion 156 6 Conclusions 157 References 159 The Northern Margin of the Eastern Ghats Mobile Belt: Evidence for Strike-Slip Tectonics Along a Craton-Mobile Belt Boundary 161 1 Introduction 162 2 Geological Setting 163 2.1 Eastern Ghats Mobile Belt 165 2.2 Rengali Province 165 2.3 Singhbhum Craton 166 3 Methodology 167 4 Results 168 4.1 Structure 168 4.2 Petrography and Microstructure 171 4.3 Electron Backscatter Diffraction (EBSD) Studies 175 5 Discussion 176 5.1 Evolution of Ideas About the Northern Margin of the EGMB 176 5.2 The EGMB-Rengali Province Boundary 176 5.3 Implications for Further Studies on the Northern Margin of the EGMB 178 6 Conclusions 179 References 180 A Preliminary Study on Earthquake Source Properties Based on Geochemistry, Shear Resistance and Melt Pressure of Pseudotachylites, Gangavalli Fault, South India 183 1 Introduction 184 2 Geological Setting 184 3 Methodology 186 3.1 Mapping and Sampling 186 3.2 Geochemical Analysis 186 3.3 Frictional Stress Measurement 192 3.4 Melt Pressure Measurement 193 4 Result 194 4.1 Megascopic Study of Pseudotachylite Veins 194 4.2 Microscopic Study of Pseudotachylite Veins 195 4.3 Geochemical Analysis 196 4.4 Shear Stress Estimation 198 4.5 Melt Pressure Estimation 198 5 Discussion 200 5.1 Parent Rock and Coseismic Melting Temperature of Pseudotachylite 200 5.2 Frictional Shear Stress Estimation and Implication About Magnitude of Earthquake 201 5.3 Melt Pressure and Flip-Flop Between σ1 and σ2, Implication for Stick-Slip and Stress Drop 202 6 Conclusions 203 References 203 Anisotropy of Magnetic Susceptibility (AMS) Studies on Quartzites of Champaner Group, Upper Aravallis: An Implication to Decode Regional Tectonics of Southern Aravalli Mountain Belt (SAMB), Gujarat, Western India 206 1 Introduction 206 2 Geological and Structural Setting 207 3 Anisotropy of Magnetic Susceptibility Studies on Quartzites, Principle and Methodology 209 4 Result and AMS Data Interpretation 210 5 Discussions 213 5.1 Significance of AMS Study for the Study Area 213 5.2 AMS of Adjoining Areas 213 6 Conclusion 215 References 216 Tectonic Implications of Small-Scale Structures in the Main Central Thrust Zone of Garhwal Higher Himalaya 219 1 Introduction 219 2 Geological Setting 221 3 Methodology, Principle and Assumptions 222 4 Results 225 4.1 Deformation Structures 225 4.2 Crystallographic Preferred Orientation of Quartz 231 4.3 Estimation of Strain 232 4.4 Estimation of Compressive Stress Direction 232 5 Discussion 233 6 Conclusions 235 References 236 Thrust Sheets, Tectonic Windows, and Intermontane Basins in the Nepal Himalaya 239 1 Introduction 239 2 Great Midland Antiform and Tectonic Windows 242 2.1 Tectonic Windows of West Nepal 243 2.2 Tectonic Windows of East Nepal 243 3 Great Mahabharat Synform and Klippen 248 4 Active Faults and Seismicity 250 5 Intermontane Basins 251 5.1 Thakkhola Graben 252 6 Conclusions 255 References 256