TARGET SELECTION FROM AIRBORNE MAGNETIC AND RADIOMETRIC DATA IN STEINHAUSEN AREA, NAMIBIA A thesis submitted in partial fulfilment of the requirements for the degree of Masters of Sciences in Economic Geology Geology Department Rhodes University by Corus Naudé January 2012 ABSTRACT The eastern branch of the late Proterozoic Damara Orogenic Belt of central Namibia hosts various copper, gold, manganese and uranium deposits, but in the vicinity of Steinhausen, approximately 145 km northeast of Windhoek, the Damara Belt becomes increasingly covered by recent Kalahari cover sediments resulting in little known geology and subsequent lack of discovered economic mineral deposits. Airborne magnetic and radiometric data over the Steinhausen Study Area was enhanced through image processing and filtering to accentuate characteristics of subsurface geology that, by comparing these characteristics to known geology, aided in the interpretive mapping of lithology, structure and targets for follow-up exploration. As a result, some important observations regarding the regional lithology can be drawn. An arenaceous stratigraphic unit that includes a coarse grained, glassy quartzite below the Kuiseb Formation equates to either the eastern Damaran equivalent of the Nosib Group subjected to high grade metamorphism or, alternatively, the upper part of the pre-Damaran sequence, immediately underlying the Damara. The Kuiseb Formation within the study area is uncharacteristically varied as compared to the same formation further west along the Damaran Orogen and can be subdivided into 5 separate units based on geophysical signature. Structural features evident within the study area include the prominent Kudu- and Okahandja Lineaments and straddle an area of inferred uplifted stratigraphy of possibly pre-Damara age. The Ekuja Dome (Kibaran age and host to the Omitiomire copper deposit) is also clearly discernible on the airborne magnetic data and is cross-cut by an east-northeast structural zone. Direct targets for follow-up exploration include the Rodenbeck intrusion, anomalous magnetic bodies and numerous radiometric anomalies present within the study area. Identified dome-like features are considered prospective for Omitiomire-style deposits and the Okatjuru Layered Complex is considered a possible source of copper, chromite, magnetite, ilmenite, nickel and the platinum group elements. ACKNOWLEDGMENTS I would like to thank Craton Mining for permission to use the data, and Karl Hartmann (Craton) for information on the Omitiomire copper deposit. Also, to Remote Exploration Services for providing me with the opportunity to undertake my studies on a part-time basis. I would like to express my gratitude to Dr. Branko Corner for his invaluable guidance as well as for proofing of the thesis, and to my supervisors, the late Prof. John Moore for his insights and Prof. Yong Yao for his constructive input. TABLE OF CONTENTS TABLE OF CONTENTS ..................................................................................................... I LIST OF TABLES ............................................................................................................. III LIST OF FIGURES ........................................................................................................... IV CHAPTER 1 ......................................................................................................................... 1 INTRODUCTION ................................................................................................................... 1 CHAPTER 2 ......................................................................................................................... 6 GEOLOGICAL SETTING ........................................................................................................ 6 2.1 The Damara Orogen .............................................................................................. 6 2.2 Geology of the Steinhausen Study Area ................................................................. 8 CHAPTER 3 ....................................................................................................................... 15 KNOWN MINERAL OCCURRENCES AND DEPOSITS WITHIN STEINHAUSEN PROJECT AREA 15 3.1 Omitiomire copper deposit ................................................................................... 15 3.2 Copper geochemical anomalies ........................................................................... 16 3.3 Manganese occurrences ....................................................................................... 16 3.4 Nickel occurrences ............................................................................................... 17 CHAPTER 4 ....................................................................................................................... 19 MINERAL DEPOSIT MODELS AND SOME EXAMPLES .......................................................... 19 4.1 Matchless stratiform massive sulphides .............................................................. 19 4.1.1 Matchless Mine ........................................................................................................... 20 4.1.2 Otjihase Mine .............................................................................................................. 22 4.1.3 Ongeama Prospect ...................................................................................................... 23 4.2 Kuiseb Formation hosted hydrothermal copper deposits ................................... 23 4.2.1 Onganja Mine .............................................................................................................. 24 4.3 Manganese deposits ............................................................................................. 25 4.3.1 Otjosondu Manganese Field ....................................................................................... 25 4.4 Magmatic Nickel, Copper and Platinum Group Element (PGE) deposits ......... 26 4.4.1 Voisey’s Bay Deposit ................................................................................................. 27 4.4.2 Alpine serpentinites within Damara Orogen .............................................................. 28 4.5 Hydrothermal gold deposits ................................................................................. 28 4.5.1 Navachab Gold Mine .................................................................................................. 29 4.5.2 Ondundu-Otjiwapa Gold Field ................................................................................... 30 4.6 Uranium deposits ................................................................................................. 31 4.6.1 Calcrete-hosted uranium deposits ............................................................................... 32 4.6.1.1 Langer Heinrich Deposit .................................................................................... 32 4.6.2 Classical vein deposits ................................................................................................ 33 4.6.2.1 Schwartzwalder Mine ......................................................................................... 34 4.6.2 Deposits associated with igneous rocks ...................................................................... 34 4.7 Omitiomire-style copper ....................................................................................... 35 4.8 Geophysical expressions of target models ........................................................... 37 CHAPTER 5 ....................................................................................................................... 44 DATASETS AND PROCESSING ........................................................................................... 44 5.1 Geological Data ................................................................................................... 44 5.2 Satellite Imagery ................................................................................................... 47 5.2.1 Landsat ETM+ data..................................................................................................... 47 i 5.2.2 Shuttle Radar Topography Mission (SRTM) ............................................................. 54 5.3 Geophysical Data ................................................................................................. 56 5.3.1 Airborne radiometric data ........................................................................................... 56 5.3.2 Airborne magnetic data ............................................................................................... 69 5.3.2.1 Total Magnetic Intensity (TMI) ......................................................................... 70 5.3.2.2 First Vertical Derivative (FVD) ......................................................................... 71 5.3.2.3 Reduction to Magnetic Pole (RTP) .................................................................... 72 5.3.2.4 Total Horizontal Derivative (THD) ................................................................... 75 5.3.2.5 Normalised Total Horizontal Derivative (TDX) ............................................... 76 5.3.2.6 Analytic Signal (AS) .......................................................................................... 78 5.3.2.7 Potential Field Tilt Derivative (TDR) ................................................................ 80 5.3.2.8 Horizontal Derivative of the TDR (HD-TDR) .................................................