Subsurface Structure of the Bushveld Igneous Complex, South Africa: An Application of Geophysics

Wednesday, 17 December 2014
Gerardo Vallejo1, Brynn Loryn Galindo1, Valerie Carranza2, Carlos Daniel Gomez3, Kameron Ortiz4, Joel Castro4, Christian Falzone5, Jonathan Guandique5, Erica Emry6, Susan Jane Webb7 and Andrew Nyblade6, (1)California State University Bakersfield, Bakersfield, CA, United States, (2)Los Angeles Valley College, North Hollywood, CA, United States, (3)California State University Northridge, Northridge, CA, United States, (4)University of Texas at El Paso, El Paso, TX, United States, (5)Fort Valley State University, Fort Valley, GA, United States, (6)Pennsylvania State University Main Campus, University Park, PA, United States, (7)University of Witwatersrand, Johannesburg, South Africa
South Africa is host to the largest single known platinum group metal supply in the world. The Bushveld Igneous Complex, spanning 300x400 kilometers, hosts hundreds of years’ worth of platinum, chromite, vanadium, and other ore. Its wealth of these metals is tied directly to the large layered igneous intrusion that formed roughly 2061 million years ago. The extraction of platinum is vital to the industrial world – as these metals are widely used in the automotive industry, dental restorations, computer technology, in addition to many other applications. In collaboration with the Africa Array geophysics field school and the Penn State Summer Research Opportunities Program (SROP), we surveyed the Modikwa mine located along the border of the provinces of Mpumalanga and Limpopo in South Africa. The following techniques were applied to survey the area of interest: seismic refraction and reflection, gravity, magnetics, electrical resistivity, and electromagnetics. The data collected were used to determine the depth to bedrock and to identify potential mining hazards from dykes and faults in the bedrock. Several areas were studied and with the combination of the above-mentioned methods several possible hazards were identified. One broad, major dyke that was located in a prior aeromagnetic survey and several previously undetected, parallel, minor dykes were identified in the region. The overburden thickness was determined to be ̴4-5 meters in some regions, and as thin as several centimeters in others. This section of rock and soil lies above an area where platinum will likely be mined in the future. The removal of overburden can be accomplished by using power shovels or scrapers; while remaining material can be contained with the use of galvanized steel culverts. Additionally, a number of joints were located that may have allowed water to accumulate underground. The models created from the data permit us to estimate which hazards could be present in different parts of the land surveyed. These results are important information that will help determine how deep to mine while also avoiding hazards that could result in serious injuries to personnel or cause costly damages to equipment.