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Volcanogenic and Hydrothermal Evidence from the Central Indian Ocean Basin Since 60 Ma

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Volcanogenic and Hydrothermal Evidence from the Central Indian Ocean Basin Since 60 Ma Volcanogenic and hydrothermal evidence from the Central Indian Ocean Basin since 60 Ma A Thesis submitted to the Goa University for the Award of the Degree of DOCTOR OF PHILOSOPHY In the School of Earth, Ocean and Atmospheric Sciences By Ankeeta Ashok Amonkar Research Guide Dr. Sridhar D. Iyer Chief Scientist (Retired) (CSIR-National Institute of Oceanography, Goa 403004) Goa University, Taleigao, Goa 2020 CONTENTS Page No. Declaration Certificate Acknowledgements i-ii List of Publications iii-iv Acronym v-vi Preface vii-xii List of Figures xi-xiii List of Tables xiv-xv Chapter 1 An overview of the Central Indian Ocean Basin: Structure, 1-14 Tectonic, Sediment and Volcanism 1.1 Study area - Central Indian Ocean Basin 2 1.2 Tectonic evolution of the CIOB 4 1.3 Sediment classification and distribution in the CIOB 7 1.4 Mineral deposits in the CIOB 12 1.5 Previous studies related to volcanism and hydrothermal 12 activity in the CIOB 1.6 Objectives 13 1.7 Summary 14 Chapter 2 Materials, Methodology, and Techniques 15-27 2.1 Sampling details 16 2.2 Sediment and rock processing 17 2.3 Microscopy 18 2.3.1 Binocular, Polarized 18 2.3.2 Scanning Electron Microscope (SEM) 19 2.4 Analytical Procedures 19 2.4.1 Energy Dispersive Spectrometry (EDS) 19 2.4.2 Electron Probe Micro Analyser (EPMA) 20 2.4.3 X-Ray Fluorescence (XRF) Spectrometer 20 2.4.4 Inductively Coupled Plasma Mass Spectrometry (ICP-MS) 21 2.4.5 Magnetic susceptibility 21 2.5 Summary 22 Chapter3 Basalts and Vhm From Seamount Dominated Areas 23-56 3.1 Introduction 29 3.2 Literature review on seamounts 30 3.3 Study Area 32 3.4 Results 33 3.4.1 Morphology of the CIOB seamounts 33 3.4.2 Petrography of seamount basalts 33 3.4.3 Chemical composition of seamount basalts 36 3.5 Interpretations and Discussion 36 3.5.1. Seamount morphology 36 3.5.2 Petrography 36 3.5.3. Major oxides 38 3.5.4 Minor, trace and rare earth elements 40 3.5.5 Seamount emplacement and associated vhm 48 3.6. Conclusions 49 Chapter 4 Iron-Rich Magnetic Spherules 57-76 4.1Introduction 58 4.2 Earlier studies on Fe-rich spherules in the Indian Ocean 59 4.3 Study area 59 4.3.1 Sampling strategy 59 4.4 Results and Interpretations 61 4.4.1 Sediment characteristics and coarse fraction 61 description 4.4.2 Iron-rich magnetic Spherules 62 4.4.2.1 Spatial distribution 63 4.4.2.2 Physical characteristics- Shape, Size and 63 Texture 4.4.2.3 Chemical composition of spherules 67 4.4.3 Fe-rich Particles: physical and chemical parameters 69 4.4.4 Comparison with other deep sea Fe-rich spherules 69 4.5. Discussion 70 4.5.1 Formational process of Fe-rich spherules 72 4.5.2 Volcanic-hydrothermal activities in the CIOB 75 4.6 Conclusions 76 Chapter 5 Metal-Rich and Native Grains 87-105 5.1 Introduction 88 5.2 Study Area 90 5.3 Results and Interpretations 90 5.3.1 Titano-magnetite grains 90 5.3.2 Metallic grains: Zn-Cu-S, Zn-Cu 91 5.3.3 Metallic grains: Ba-S, Ba-Pb-S 94 5.3.4 Aluminium-rich spherules 94 5.3.5 Native silver grains 95 5.4 Discussion 95 5.4.1 Model for the formation of metal grains in the CIOB 100 5. 5 Conclusion 103 Chapter 6 Basalt Emplacement: Formation of baked sediments and 106-130 vhm 6.1 Introduction 108 6.2 Sediment core 108 6.3 Results and Discussion 109 6.3.1 Physical description and coarse fraction of the 109 sediment core AAS-22/7 6.3.2 Magnetic susceptibility measurements 110 6.3.3 Geochemistry of core AAS-22/7 sediments 114 6.3.4 Geochemistry of the entrapped rock 118 6.3.5 Effect of magmatic activity on the sediments 120 6.4 Conclusion 122 Chapter 7 Effect of low-temperature alteration: Palagonite formation 131-163 and Mass disappearance of radiolarian 7.1 Introduction 132 7.2 Background work 134 7.3 Study Area 135 7.4 Results and Interpretations 135 7.4.1 Core fractions description 135 7.4.2 Palagonite Grains: morphology and composition 138 7.4.3 Phillipsite Grains: morphology and composition 141 7.4.4 Composition of the core sediments 143 7.4.5 Magnetic susceptibility measurements 145 7.5 Discussion 149 7.5.1 Mass disappearance of radiolarians 149 7.5.2 Alteration of sediments / Palagonitisation 150 7.6 Conclusions 153 Chapter 8 Volcanic Glass Shards and Tephrochronology 164-190 8.1 Introduction 165 8.2 Earlier studies of the CIOB glass shards 167 8.3 Study area 167 8.4 Results and Interpretations 168 8.4.1 Core descriptions: 168 8.4.2 Morphology of shards (Shape, Size, Texture) 171 8.4.3 Chemical composition of glass shards 171 8.4.4 Sedimentation rate and age of the cores 172 8.4.5 Tephrochronology of the CIOB Shards 174 8.5 Discussion 177 8.5.1 Source and Formation of shards 179 8.6 Conclusion 180 Chapter 9 Summary and Conclusions 195-197 9.1 Summary and Conclusions 196 9.2 Scope for future study 196 References 198-212 CERTIFICATE This is to certify that the thesis titled “Volcanogenic and hydrothermal evidence from the Central Indian Ocean Basin since 60 Ma” submitted to Goa University, by Ms. Ankeeta Ashok Amonkar for the award of the degree of Doctor of Philosophy in Marine Sciences is a record of original and independent work carried out by her during the period of September 2015- January 2020 under my supervision and the same has not been previously submitted for the award of any diploma, degree, associateship or fellowship or any other similar title. CSIR-NIO, Goa January 2020 Dr. Sridhar D. Iyer Ph.D. Supervisor Formerly with CSIR-National Institute of Oceanography Dona Paula 403004 Goa, India DECLARATION As required under the University Ordinance OB-9A, I hereby declare that the matter embodied in this thesis titled “Volcanogenic and hydrothermal evidence from the Central Indian Ocean Basin since 60 Ma” submitted to Goa University, for the award of the degree of Doctor of Philosophy in Marine Sciences is a record of original and independent work carried out by me during the period of September 2015 – January 2020 under the supervision of Dr. Sridhar D. Iyer, CSIR-National Institute of Oceanography, Dona Paula and that it has not been previously formed the basis for award of any diploma, degree, associateship or fellowship or any other similar title. CSIR-NIO, Goa January 2020 Ms. Ankeeta Ashok Amonkar CSIR-National Institute of Oceanography Dona Paula 403004 Goa, India Goa University Taleigao, Goa, India ACKNOWLEDGEMENTS The successful completion of this thesis work would not have been possible without the support, encouragement, cooperation and assistance from many individuals who contributed immensely and stood constantly with me in these 4 years of long journey. With great pleasure I take this opportunity to express my deep sense of gratitude to my research supervisor Dr. Sridhar D. Iyer, Retired Chief Scientist, CSIR-National Institute of Oceanography. His immense knowledge, valuable guidance and cool temperament helped me in evolving as a better person and in completing my research work successfully. I am really fortunate to have him as my Ph.D. supervisor. I fall short of words to thank Dr. G. N. Nayak, Emeritus Scientist, School of Earth, Ocean and Atmospheric Sciences and Dr. R. Mukhopadhyay for their suggestions and advice during the doctoral committee meetings. Their inspirational words, scientific ideas and patience have equally helped me in completion of my research. I am thankful to the Director, CSIR-NIO, Dr. V. Loveson (Head GOD and Project Leader), CSIR-NIO, The Vice-Chancellor Goa University and Dr. H. Menon, Dean of Faculty of School of Earth, Ocean and Atmospheric Sciences, Goa University for providing facilities and in administrative matters. Wholeheartedly I am thankful to Dr. F. Badesab for permitting me to carry out magnetic susceptibility analysis, Dr. M. Kocherla for XRF analyses, Dr. A Mudholkar for thin section preparation, Dr. G. Parthiban for ICP-MS, Mr. A Sardar for SEM and SEM- EDS, Mr. V M Khedekar for EPMA,and Dr. Brenda and Dr. Pratima for allowing access to geochemistry and sedimentology laboratories and Dr S. M. Gupta, (Retired scientist) for his help and discussion. I specially remember and thank Dr. N. G. Rudraswami, for rendering me his computer system and financial support to carry out analysis outside CSIR-NIO. His positive and kind nature has always encouraged me to keep going in low times. I am thankful to Dr. E V S S K Babu from CSIR-National Geophysical Research Institute and his student S Manju for helping with the EPMA analysis of glass shards and spherules. It is indeed a great pleasure and privilege for me to express my indebted sense of gratitude to Prof. S. Balakrishnan, Professor, Dept. of Earth Sciences, for allowing me to work in his clean laboratory at Pondicherry University. I am thankful to Dr. J. N. Pattan for being there, supporting with his valued comments and suggestions during my research work and Dr. Anthony Veigas for conducting SRF evaluation. I acknowledge Dr. B. N. Nath (PL- GEOSINK), and Dr. M. Prasad, Late Dr. R. Banerjee, Dr. B. Chakraborty, Dr. A. Saha (all PL- PMN Survey and Exploration). I acknowledge CSIR-Direct SRF Fellowship (Grant No. 31/026/ (0306)/2018-EMR- I) for funding and to carry out the research work.
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