Determining the Total Volume of the 2.05 Ga Bushveld Magmatic Event: Correlation of the Molopo Farms Complex, Botswana

Abstract:

The Bushveld Igneous Complex (BIC) in South Africa, erupted 2.05 billion years ago, is the world’s largest layered intrusion in the range of 710-1060 x 10³ km³ conservatively. However, the total volume of the magmatic event that produced the BIC remains poorly known. Several other intrusions occurred approximately contemporaneously with the BIC, but a clear relationship between these multiple intrusions is yet to be determined. The Molopo Farms Complex (MFC) is a layered igneous complex of similar age 2.044 Ga ­± 24 Ma located in Botswana, 200km west of the far western limb of the BIC, with a total volume of 1300 km². Using trace element analysis, this study makes an attempt to find a correlation between the magma that emplaced the Molopo Farms Complex with the Bushveld Igneous Complex. The MFC is related to the BIC and is located under approximately 200m of Kalahari sands, which prevents any direct sampling or observation. Unlike the BIC, the MFC is poorly studied creating a lack of information for the complex. Drill core samples from the MFC were analyzed to determine the trace element composition using an inductively coupled plasma mass spectrometer (ICP-MS). Using previously reported values for the BIC; a comparison can be made on both complexes to find possible correlations. The comparison of trace element schematics in the MFC and the BIC suggest that both complexes are derived from the same parental magma, often referred to as the “B1” magma. These comparisons allow for an assumption that the initial parental magma of the BIC may have also emplaced the MFC.