Name: ESS1
Start: 2013-08-12T08:00:00+02:00
End: 2013-08-15T20:00:00+02:00
Location: NMMU Summerstrand South Campus

Monday, 12 August
- 08:30 → 08:50
  
  REGISTRATION 20m
  
  Speaker: Prof. Moctar Doucoure (AEON - NMMU)
- 09:00 → 10:30
  
  Introduction to and Connections to Earth Stewardship Science 1h 30m
- 11:00 → 15:00
  
  Mantle origins of landscape evolution : Mantle dynamics and kimberlite emplacement 4h
  
  Mantle dynamics impact the behavior of Earth’s surface, and vice versa. In particular, the buoyancy forces generated by density anomalies at depth can play an important role in land surface movements. Temperature and composition both influence the density of materials in the Earth’s interior, with changes in these parameters often occurring during periods of geological activity leading to magmatism. On continents, underlying mantle activity is not always reflected in volcanism because the thick, cold continental lithosphere may act as a barrier, either trapping rising magmas or focusing them into particular locations by its internal structure. The lithosphere itself may undergo heating and chemical change (metasomatism) that influence its isostatic balance and elevation with respect to neighbouring regions. Thus, density changes and their surface impacts may be transient or long-lived, depending on their origins and where they are located within the underlying mantle. Although geophysical imaging and surface dynamics can provide some clues to mantle properties today, inferring what they were in the past, and how they changed with time relies on the evidence from mantle-derived rocks and tectonic reconstructions. This section of the course will review the tectonomagmatic history of southern Africa from Gondwana times to the present and the basic geophysical structure of the underlying mantle. We will consider the relationship in space and time between surface volcanism and underlying mantle dynamics, and the impact of magmatic events on the thermal and chemical structure of the deep lithosphere of the African plate. A general introduction to the Karoo and Parana-Etendeka large igneous provinces, group I and group II kimberlites, and younger alkaline mafic rocks such as melilitites will be provided, and to the mantle xenoliths in kimberlites. We will examine evidence from mantle xenoliths for heating and metasomatism of the lithosphere, and the density implications. The goal is to provide a broad framework in which to assess the role of the mantle on surface movements, and to focus attention on some specific areas for future research. Outline: 1. The present view of magmatism, topography, and deep Earth structure of Africa. 2. The structure of southern African lithosphere as a reflection of its tectonic history 3. Regional plate tectonic setting of S. Africa from ~400 Ma and Gondwana breakup 4. Mesozoic magmatism: location, timing, petrology/geochemistry and origins 4.1 The Karoo LIP 4.2 Group II kimberlites 4.3 Group I kimberlites 4.4 Melilitites and other alkaline rocks. 4.5 The Parana-Etendeka LIP 4.6 The Agulhas Plateau 5. Mantle xenoliths and the evidence they contribute 5.1 Introduction to mantle xenoliths 5.2 Thermobarometry and mantle geotherms 5.3 The process of mantle metasomatism 5.4 A dynamic model for lithospheric evolution in southern Africa 6. Density changes in the mantle and possible surface consequences.
  
  Speaker: Prof. David Bell (SARCHi Chair: Earth Systems Sciences, NMMU and ASU)
- 15:30 → 17:00
  
  INTRODUCTION TO THE MAGNETOTELLURIC METHOD FOR CRUSTAL AND LITHOSPHERIC STUDIES 1h 30m
  
  Apart from the Earthquake Seismology Method, the Magnetotelluric (MT) method is the only other geophysical method that enables the geoscientist to investigate deep crustal and lithospheric structure of the earth. The largest differences between the two techniques are that the MT technique targets the conductivity and conductivity contrasts between lithologies, while the Seismology technique targets seismic velocity contrasts and density differences between lithologies. There are many similarities between the two techniques, which include: 1. Deep exploration 2. Long time series to detect the zones of interest 3. Use natural sources 4. Can use artificial sources 5. Fairly complicated and time consuming processing techniques. This presentation(s) will focus on: 1. Why the MT technique is possible (from sunspots to the earth's magnetic field and the core) 2. Basic theoretical background of the MT Technique (EM – Theory and the Maxwell equations) 3. Basic processing of the data to obtain resistivity curves 4. MT equipment and field practice 5. Examples of how the MT technique was used to obtain information about the lithospheric thickness of the Kaapvaal Craton, the Rehoboth Craton, the Natal Namaqua and Limpopo Mobile Belts, the Colesberg Lineament and the lithospheric expression of the Kimberly Kimberlite feeder 6. Possible future studies which include the complete mapping of the Kaapvaal Craton, the Trompsburg Complex and the Karoo Basin for developing and evaluating the Shalegas exploitation. The MT technique is under siege in South Africa due to the enormous cultural development in South Africa. It is a matter or urgency that we start with the regional MT surveys across South Africa before it is too late.
  
  Speaker: Dr Stoffel (CJS) Fourie (Environmental Water and Earth Sciences Department, Faculty of Science, Tshwane University of Technology (TUT))
Tuesday, 13 August
- 08:30 → 13:00
  
  Geophysical targeting and detection of kimberlites and characterization of the critical zone 4h 30m
  
  This course deals with the application of geophysical methods to regional targeting and detection of kimberlites, and to the characterisation of the critical zone. Kimberlites are complex hybrid rocks derived from the Earth mantle through intrusive and extrusive emplacement processes. As carriers of xenoliths, kimberlite pipes offer a valuable window into the crust and mantle and are targeted by the mineral industry as primary sources of diamonds. Diamond-bearing kimberlites are known to be associated with cratonic domains underlain by rigid sub-continental lithospheric mantle that can be delineated by regional scale geophysical data. The detection and determination of the precise location of kimberlite pipes is better achieved using higher-than-regional-scale resolution geophysical surveys. This is because most pipes are located at depth and hidden from direct observation at the surface where only indicator minerals may be found in soil. Soil is the central component of the near-surface Earth extending from the top of the vegetation canopy (the lower limit of airborne survey altitude) down to and including the zone of freely circulating groundwater. This near-surface Earth is known as the critical zone. This zone is dynamic and sustains all terrestrial life through its resources. Characterisation of the critical zone is thus important and can be done through various geophysical applications that are, amongst others, environmental, geotechnical, groundwater, archaeological, or mining in focus. These near-surface geophysical applications are distinguished by shallow depths of investigation, requirement for high-resolution, and the possibility for real-time validation of results.
  
  Speaker: Prof. Moctar DOUCOURE (NMMU)
- 14:00 → 17:00
  
  Thermochronology - Short Course Outline 3h
  
  AEON Earth Stewardship Science – Short Course, 13-14 August 2013 Thermochronology Short Course Outline Organizers: Becky Flowers and Jessica Stanley, University of Colorado Boulder Tuesday, 13 August 2013 (0.5 day) Low temperature thermochronology: General background and technique (0.5 day = 4 hrs) 13:00 – 13:50 Fundamentals of thermochronology Topics will include radioactivity and decay, diffusion, closure temperatures, partial retention, and the thermal structure of the lithosphere 14:00 – 14:50 Development and fundamentals of (U-Th)/He thermochronology Historical view of He thermochronology, highlighting recent milestones of the last two decades Details of the (U-Th)/He method, how to do analyses, reproducibility, uncertainties, and the effects of radiation damage, parent zonation, and inclusions on He dates 15:00 – 15:50 Interpreting He dates – classic examples Examples of published and ongoing studies that have taken advantage of He thermochronology to constrain a variety of geologic and tectonic processes. Topics may include the use of He thermochronology in convergent and divergent orogens, landscape evolution, the thermal history of sedimentary basins and implications for hydrocarbon exploration, detrital thermochronology, and spatial and temporal patterns of erosion 16:00 - 16:50 General discussion and HeFTy software downloads/organization. Wednesday, 14 August 2013 (0.75 day) Low temperature thermochronology: Applications and case studies (0.75 day = 6 hrs) 08:00 – 09:10 Case study: Southern African Plateau 09:25 – 10:35 Tutorial #1: Modeling He dates, the basics Hands-on exercise using freely available software (HeFTy) to create thermal models using He data 10:50 – 12:00 Case study: North American interior 13:00 - 13:30 The Future of He thermochronology Discussion of where He thermochronology is headed, highlighting recent work on applying and interpreting He datasets, including an emphasis on minerals other than apatite and zircon. Examples may include wildfire thermochronology, clinker dating, double-dating, and more sophisticated modeling approaches 13:30 – 14:00 Brainstorming and discussion of ideas for He work on problems in Africa 14:00 – 15:00 Tutorial #2: More complex examples
  
  Speakers: Ms Jessica Stanley (University of Colorado Boulder, USA) , Dr Rebecca Flowers (University of Colorado Boulder, USA)
Wednesday, 14 August
- 08:30 → 13:00
  
  Low-temperature thermochronometry: General background and technique
  
  Continued from Tue 13 August 2013
  
  Convener: Dr Rebecca Flowers (University of Colorado Boulder, USA)
- 14:00 → 15:00
  
  Thermocronometry: Discussions with more complex case studies 1h
  
  Speaker: Dr Rebecca Flowers (University of Colorado Boulder, USA)
- 15:30 → 17:00
  
  Cosmogenic dating of the critical zone and climatically influenced denudation rates of the southern African plateau 1h 30m
  
  Cosmogenic nuclides are produced through the interaction of high-energy cosmic ray particles with target nuclei in the earth’s atmosphere, in meteorites and in terrestrial rocks. Because cosmic ray particles interact with the earth’s atmosphere during their descent, cosmogenic nuclides produced in situ in terrestrial surface rocks are several orders of magnitude less abundant than in meteorites, and thus it is only in the last two decades that technological advances have allowed for their routine analysis. Cosmogenic nuclides typically yield constraints on earth surface exposure histories on an intermediate timescale of 103 to 106 years and are thus useful for the investigation of a range of geomorphological problems. Southern Africa offers a unique field laboratory for such research, as it paradoxically exhibits tectonic stability and low rates of denudation despite its high topography. Here we examine the present controls on denudation in southern Africa through an investigation of the maximum denudation rates of Karoo dolerite surfaces in the region, determined from the abundances of cosmogenic noble gas nuclides (3He, 21Ne and 38Ar) in pyroxenes. We compare these results with the predictions of a climate-dependent weathering rate model, and find an excellent agreement in the value ranges of both datasets (~4 m/Myr), which we interpret as evidence that present denudation in southern Africa is weathering-limited and climatically influenced due to an apparent absence of significant regional neotectonic uplift. The onset of this geodynamic coupling is unknown but may be of considerable antiquity, thus allowing for the prolonged tenure of southern Africa's inherited Cretaceous topography. We also compare these low bedrock denudation rates, which may be interpreted to represent local rates of soil production, with various literature estimates for the corresponding rates of soil erosion in the same catchments, and find that they are in all instances lower, by up to two orders of magnitude. This significant contrast between long term rates of climatically-influenced soil production and short term rates of anthropogenically-driven soil erosion suggests that current agricultural practices are unsustainable under prevailing geological conditions.
  
  Speaker: Prof. Maarten De Wit (Chair: Earth Stewardship Science - AEON, NMMU)
Thursday, 15 August
- 08:30 → 10:30
  
  The critical zone and remote sensing applications to soil degradation and land use 2h
  
  Critical pedological, lithological and topographical surfaces exist within the landscape where certain episodic processes could be triggered within a spatial-temporal framework. Severe soil erosion forms, shallow and deep landslides, surface wetness conditions and other land surface hazards do have preferential zones where they occur within the landscape. Spatially explicit topographically driven models have been developed to identify such critical zones using remote sensing techniques and Digital Elevation Models (DEMs). According to Pelletier (2008), DEMs should be a part of every geoscientist’s toolkit! They provide baseline data for quantifying landscape morphology and enable modelling pathways of mass and energy transport through the landscape. This short course serves as an introduction to the TOPMODEL from which indices to a range of critical zones are developed.
  
  Speaker: Prof. Vincent Kakembo (ACE - NMMU, Department of Geosciences)
- 11:00 → 15:00
  
  The critical zone and geoecodynamics 4h
  
  Speaker: Dr Fenton Cotterill (AEON - Stellenbosch University)
- 15:30 → 16:00
  
  Wrap-up and future development 30m

ESS1

VIP Lounge (upstairs), Sport Conference Centre

NMMU Summerstrand South Campus