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Hyperspectral Mapping of Surface Mineralogy in the Lake Magadi Area in Kenya

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Hyperspectral mapping of surface mineralogy in the Lake Magadi area in Kenya. Gayantha Roshana Loku Kodikara March, 2009 Hyperspectral mapping of surface mineralogy in the Lake Magadi area in Kenya. by Gayantha Roshana Loku Kodikara Thesis submitted to the International Institute for Geo‐information Science and Earth Observation in partial fulfilment of the requirements for the degree of Master of Science in Geo‐information Science and Earth Observation, Specialisation: Geo‐hazards Thesis Assessment Board Prof.Dr. F.D. van der Meer (Chair) Dr. P.M. van Dijk (External Examiner) Dr. T. Woldai (First Supervisor) Dr. F.J.A. van Ruitenbeek (Second Supervisor) Observer: Drs. T.M. Loran (Programme Director) INTERNATIONAL INSTITUTE FOR GEO‐INFORMATION SCIENCE AND EARTH OBSERVATION ENSCHEDE, THE NETHERLANDS Disclaimer This document describes work undertaken as part of a programme of study at the International Institute for Geo‐information Science and Earth Observation. All views and opinions expressed therein remain the sole responsibility of the author, and do not necessarily represent those of the institute. To my loving mother H.B. Kusumawathe. Abstract Hyperion and Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) data were used to identify, map and model the spatial distribution of the mineral precipitates at the Lake Magadi area in Kenya. Mapping was coupled with laboratory analysis, including reflectance and emittance spectroscopic measurements and X‐ray diffraction for selected rock and soil samples. In addition to that, land surface temperature mapping, stratigraphic information and drainage network extraction of the area were carried out using remote sensing techniques and later integrated and modelled. The spectral responses of 92 rock and soil samples were studied and identified. The spectral signatures of Magadiite (NaSi7O13 (OH) 3 ∙3H2O) and Kenyaite (NaSi11O20.5 (OH) 4 ∙3H2O), which are not known from the work of others, were established in this research. The Magadiite shows diagnostic absorption feature at 1.464 µm. The characteristic absorption features of the Kenyaite are at 1.153 µm and 1.464 µm wavelength regions. In addition to that, spectral signatures of trona, chert, diatomite, basalt/trachyte, erionite, Green bed and High Magadi bed were studied and identified. Chert samples show the broad Si‐OH absorption feature at 2.2 µm while, Green bed, High Magadi bed and diatomite exhibit carbonate absorption feature at 2.35 µm with broad Si‐OH absorption feature at 2.2 µm. Trona exhibits six common absorption features at 1.50, 1.74, 1.94, 2.03, 2.22 and 2.39 µm. Thermal Infrared spectra of trona also exhibit three characteristics features at 6.66, 9.35 and 11.71 µm wavelength regions. The spectroscopic studies of undisturbed soil samples revealed that the evaporites have been restricted to the uppermost part of the surface and the change in mineral phase is possible due to the temperature changes. Mapping of different stages of evaporites and other surface minerals using combination of ASTER and Hyperion images facilitated by different types of mapping techniques including spectral mapping methods (SAM & MTMF) and band rationing method substantially improved the existing knowledge of the geology of the area. Stratigraphic information extracted from remote sensing methods showed that the mineral precipitates are restricted to the low lying areas associated with water. Drainage network extracted from the ASTER DEM showed the influence of runoff for mineral reactions and formations that were described in existing hydro‐geochemical models of the area. The contribution of spatial and temporal land surface temperature variations for the evaporitic mineral formations in the area was identified after mapping surface temperatures from ASTER TIR (Thermal Infrared) bands. Finally, this study concludes that the usage of remote sensing techniques with existing geochemical knowledge of the area significantly enhanced the capability to derive substantial information related to the distribution and formation of precipitates and evaporites in the area. Keywords: Hyperion; ASTER; Lake Magadi; Reflectance and emittance spectroscopy; X‐ray Diffraction; Surface mineral mapping; Land surface temperature mapping; Drainage network extraction; Magadiite; Kenyaite; Trona; Chert; Diatomite; Remote sensing i Acknowledgements First and fore most, I would like to express my sincere appreciation and thanks to my supervisors Dr. T. Woldai and Dr. F.J.A. van Ruitenbeek for their unlimited and continuous support, critical comments and guidance from the inception to the success of the research. I am very much grateful for their encouragement, advice, friendship and moral support throughout this research and in all hardships met in this study. I would also like to extend very many thanks to the AES course director Drs. T.M. Loran and the Chairman of the Department of Earth Systems Analysis, Prof. Dr. F.D. van der Meer for their uncountable efforts and assistance during my studies and hardships. Also many thanks to Drs. J.B. de Smeth for all his help, critical comments, friendship and idea sharing that had a positive effect towards the success of this research. I am also grateful for Mr. Chris Hecker for his support and advice in this research especially during the spectral acquisition of the rock and soil samples using VERTEX 70 FTIR spectrometer in ITC, the Netherlands. I express my gratitude to all the staff members of AES department especially those of the Geo‐hazard stream for the skills acquired through their effort. I also extend my appreciation to the Earth Resource Exploration staff for the success of my studies and this research in particular. Also many thanks to my PhD advisor, Mr. Zack Kuria for his incredible supports during the field work in Kenya. I would also like to express my sincere appreciation to Dr. Keith Shepherd and Mr. Elvis Weullow for their guidance and kind support by giving me an opportunity to use MPA FTIR instrument at International Center for Research in Agro Forestry (ICRAF) in Nairobi, Kenya. My Sincere appreciation also goes to Ing. G.J. van Hummel for his guidance and support by giving me a great opportunity to use XRD instrument at Institute for Nanotechnology (MESA+), University of Twente, The Netherlands. I would like to thank very much to Magadi Soda company and masai community of the area for their reception and incredible support rendered during my field work. My special thanks go to Mr. S.N. Juguna who took us every where we wanted to go in the field. I would also like to take this opportunity to thank my fellow students, AES 2007 batch and all ITC friends with Ms. Darani for their good co‐operation, friendship and encouragements. I am also very much grateful for Ghebretinsae Woldu who worked with me during the field work in a same area giving me incredible support during that hard time. My sincere appreciation also goes to Dr. Jagath Gunathilake (Department of Geology, University of Peradeniya, Sri Lanka), who created my enthusiasm in field of geology and gave me the opportunity to study in ITC. Of course, all my academic success counts back on the love, help, support and encouragement that I got from my parents, relatives and friends. My mother H.B. Kusuma, most valuable person of my world, how can I dedicate to this work to you? Because you passed away during the last part of my thesis leaving me alone in this world. I would like to dedicate this work to my father L.K. Sumanadasa in particularly in this very hard sorrowful time encouraging me to finish this work successfully. I am very much grateful to my sister Inosha Kodikara and all my relatives, for their sacrifice to stay close to my parents when I am staying away from them. Especially after that sorrowful day every time they encouraged me to start my work again giving me a life and staying in touch with my father when I came back to ITC to complete the Thesis. This success is a result of their encouragement to further my studies. ii Table of contents Abstract.................................................................................................................................................... i Acknowledgement................................................................................................................................... ii Table of contents.................................................................................................................................... iii List of figures........................................................................................................................................... v List of tables............................................................................................................................................ x List of Abbreviations............................................................................................................................... xi 1. Introduction......................................................................................................................................1 1.1. Background .............................................................................................................................1 1.2. Problem Statement.................................................................................................................2 1.3. Objectives and Research questions ........................................................................................3 1.4. Research
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