Mponeng Gold Mine

History As part of the Witwatersrand, the largest gold mineralization on earth, Mponeng is the result of the discovery of the basin by Europeans. Beginning in the 1850–70s a series of mineral discoveries were made in the area, including those of Pieter Jacobus Marais panning gold from a river and Henry Lewis finding a quartz and gold vein on a farm, that led to the Witwatersrand Gold Rush in 1886. These discoveries led to many mining operations and after shaft sinking for about 5 years (1981) Mponeng officially began mining operations in 1986. Before Mponeng, the mine was known as the Western Deep Levels South Shaft or the No1 Shaft; the name Mponeng came into use in 1999. Current depths reach roughly 3.8 km down, in the coming years of remaining production life of the mine it will likely reach beyond 4.2 km depth. Striking in South Africa's mining district was apparent in the 1900s, for example the South African gold mine strike in August 1946. As Mponeng did not start operations until near the turn of the century there has not been many other notable strikes since then, other than 2012. In 2012, while AngloGold Ashanti was Mponeng's owner, strikes occurred. The strikes were a combined result of gold and platinum industry-worker issues in South Africa. AngloGold specifically experienced nearly 35,000 workers putting down their tools in the illegal strike. Although not at Mponeng, the strike of 2012 included a wildcat strike at a nearby platinum mine ended with 34 miners dying from police interactions. Gold is currently worth roughly US$2080/oz (US$1900/Troy oz). Over 5,400 metric tons of rock are excavated from Mponeng each day. Harmony Gold, aside from closures, has kept up operations: The most recent publication from Harmony Gold outlines their 2023-year production: • Produced: 7,449 kg (239,490 oz) of gold • Grade: 8.43g/t • Volume of ore milled: 884,000 tons ==Physical conditions==

The temperature of the rock reaches , and the mine pumps slurry ice underground to cool the tunnel air to below . A mixture of concrete, water, and rock is packed into excavated areas, which further acts as an insulator. Tunnel walls are secured by flexible shotcrete reinforced with steel fibers, which is further held in place by diamond-mesh netting. In 2008, researchers looking for extremophile organisms discovered the bacterium Desulforudis audaxviator present within groundwater samples from kilometers deep in the mine. The name 'Audaxviator' comes from a Latin-language passage in the novel Journey to the Centre of the Earth by Jules Verne: ("Descend, bold traveller, and attain the centre of the Earth.") == Geology and gold bearing fractures ==

The mine sits in the Witwatersrand Basin and uses 2 horizons: Ventersdorp Contact Reef and Carbon Leader Reef. These small faults often correspond to depositional and sediment contacts. == Environmental impacts ==

South Africa has been dealing with the effects of mining-related pollution for years; the effects of mining-related environmental damage have been large given that mining is roughly 8% of the South African GDP. In 1998, mining industry contributed nearly 90% of the 533.6 million tons of waste that was produced annually. According to 1998 data, gold mining is the largest single source of pollution in South Africa. A large portion of this occurs in the Witwatersrand Basin, home to over 270 tailings storage facilities, covering 18,000 Ha. of CO2 equivalent in 2024. Gold mining operations contribute to greenhouse gas emissions primarily through the use of heavy machinery, ore processing, and energy-intensive refining methods. Diesel-powered equipment, explosives, and electricity consumption—largely derived from fossil fuels in South Africa—lead to significant carbon dioxide (CO2) and methane (CH4) emissions. Beyond the environment, the citizens of the Witwatersrand Basin have been complaining of windblown dust, most of which originates from partially rehabilitated TSFs. Anglo Ashanti began recording meteorological data in 2012 and Harmony Gold has since taken over monitoring after the acquisition in 2020. A study in 2020 found elevated value of silica and uranium in PM10 airborne pollution from TSFs of gold mines in the area. == Seismicity ==

Seismicity in mines is common as removing mass amounts of rock can change stress dynamics, especially if pre-existing faults exist. This seismicity is termed 'mining-induced seismicity', caused by the release of elastic strain but are often low moment magnitude. Reaching beyond 1,000 events a day, events of any size pose serious risk to mining operations and employees. It is not uncommon for equipment to be damaged, or have the collapse of drifts and stopes as a result of events.''' In deep mines, vertical stress can reach 80–100 MPa, equivalent to roughly 10 km under water. Seismicity in deep gold mines is common, and is often induced by mining activities. Two events can be considered: Research One way to move forward is a better understanding of rock burst and excavation methods. A better understanding can provide better safety protocols. A prominent use of deep mines and their associated, often low magnitude, earthquakes is to connect laboratory scale experiments to real world situations. There is also considerable research trying to understand nucleation of said earthquakes, has emplaced a network of accelerometers and piezoelectric acoustic emissions sensors. These sensors can record very small moment magnitude earthquakes, capable of recording events with frequencies from 0.7 kHz to 200 kHz (M<0.5). In a one-year period, 2007–2008, nearly 500,000 events were recorded, most of which with low (sub 25 kHz) frequencies. The JAGUARS network is placed below the Ventersdorp Contact Reef, there are eight Acoustic emissions sensors, two strainmeters, and one triaxial accelerometer that make up the network. == See also ==