Occurrence of groundwater in the Phalaborwa igneous complex

[摘要] English: Three water bearing aquifer zones were defined in this study for the Phalaborwa IgneousComplex, namely a shallow weathered aquifer zone, fractured aquifer zone and the fresh toslightly fractured aquifer zone. The probabilities for groundwater occurrence in the differentaquifer zones in the Phalaborwa Igneous Complex are based on the available data set.The Phalaborwa Igneous Complex has intruded into granite-gneiss of the BasementComplex and is intruded by SW-NE trending dolerite dykes. These dolerite dykes are nearvertical or dip 85 0 north-west and south-east and act as preferential flow paths forgroundwater and compartmentalisation of the area.The probability of intersecting groundwater at the NSPP in the shallow aquifer zone above 50m is 68.4% and for intersecting groundwater seepage 31.6%. The probability of groundwateroccurrence below the weathered and fractured zone (50m) in the NSPP area is 5.8% to17.6%.The probability of intersecting groundwater in shallow aquifer zone above 58 m at the NPM is42.9% and for intersecting groundwater seepage 57.1 %. The probability of intersectinggroundwater below the weathered and fractured one at the NPM below 58 m is 81.8% andfor intersecting groundwater seepage 18.2%.The Phalaborwa Igneous Complex has intruded in to the Bushveld Igneous Complex, and ismined for phosphate and other minerals by Foskor and PMC. Foskor (Pty) Ltd is currentlyone of the world's leading phosphate and phosphoric acid producers, with approximately95% of South Africa's production.The world phosphate reserves are sufficient to supply the world with the required amountsand types of needed phosphate products for some centuries to come. However high gradeand economic reserves are being depleted, which could result in mining lower gradephosphate rocks at higher cost.The 95% of the global phosphate production used in agricultural production much contributedto providing enough food to ever growing world population. To sustain the large amount andhigh quality of food obtained today worldwide, and in particular in developing countries, arelargely due to the use of phosphate fertilizers, phosphorus-based herbicides andinsecticides, and plant hormone, let alone the use of phosphorus in animal feeds.There are many non-agricultural applications of phosphate-based products. Theseapplications are currently using limited quantities of phosphates, but they cover varioussectors essential to everyday life.Modern technologies, some based on incremental improvement of existing technologies andothers on entirely new concepts, should be developed to further the use of phosphates in thenon-agricultural sector.Phosphate mining has a negative impact on the quality of groundwater. Dewateringstrategies for open pit phosphate mining should be developed where a dewatering well fieldpump the groundwater away from the pit before it is contaminated in the mining process.This water should be monitored for quality and be released in to the ecosystem, or it could beused in the mining process. Groundwater quality should also be monitored with agroundwater monitoring network in order to contain groundwater pollution.

[发布机构] University of the Free State