Geology of Zambia

A one billion year Proterozoic unconformity separates the basement rock from the conglomerate, quartzite, schists, iron-rich sandstones and mudstones of the Muva Supergroup. The supergroup is intruded by carbonatite, dolerite, granite, granite porphyry, lamprophyre, norite, pegmatite and other igneous rock types. A rhyolite porphyritic belt, formed at the same time as the Muva Supergroup extends along the eastern bank of the Luapula River, between Lake Tanganyika and Lake Mweru.^[1]

In the

The deposition of the Katanga Supergroup continued into the Cambrian, in parallel with the rapid expansion of multi-cellular life. Geologists divide the supergroup into the Roan Group, Mwasha Group and Kundelungu Group in the Copperbelt, and simply into upper and lower units elsewhere. The Roan Group hosts much of the copper in the Copperbelt as chalcopyrite, chalcocite, bornite, malachite and azurite, in shale, sandstone, dolomite and quartzite associated with the margins of the Kafue syncline.

The Kundelungu Group dolomites, limestones and carbonaceous shales unconformably overly the Mwasha Group shale, argillite and interbedded quartzites. The lower unit of the Kundelungu Group is a conglomerate formed from glacial sediments, potentially related to the Hirnantian glaciation in the Ordovician, as Zambia, within the supercontinent Gondwana drifted close to the South Pole.

In the mid-Paleozoic, a large rift valley formed across southern Gondwana, spanning much of what is now southern Africa and southern South America. The

Deposition of the Karoo Supergroup continued into the Mesozoic, with the sequence capped by basalt lava flows from the Jurassic. Today, the basalt is exposed on the walls of Batoka Gorge, below Victoria Falls.

The Karoo Supergroup is overlain by Late Jurassic and Cretaceous sandstones and mudstone, and intruded by carbonatite and kimberlite.

During the past 66 million years of the Cenozoic, the Kalahari Desert underwent a major expansion during a long lasting dry period. In the Neogene through the Pleistocene, this climate change deposited moderately consolidated sandstones and windblown sands as the Kalahari Group in the Western Province and other parts of northwest, south and central Zambia. Pleistocene and Holocene alluvial deposits line the major rivers, as well as the Bangweulu Swamps and Kafue Flats.^[2]

Hydrogeology

Quaternary alluvial aquifers and the 20 to 40 meter unconsolidated sands of the Kalahari Group, in western and northeastern Zambia are recharged by rainwater, although the Kalahari Group has some issues with brackish water.

Several units of the

Large parts of the country are underlain by granite and gabbro crystalline basement rock. These rocks are generally impermeable, but store water in 10 to 15 meter thick weathered regolith and fractures.^[3]

Natural resource geology

Zambia has extensive natural resources, most famously the copper ore of the Roan Group, which gave rise to the Copperbelt region. Until the rapid decline in copper prices in the mid-1970s, copper mining formed the backbone of the economy of Zambia. Demand has picked up for copper, along with secondary production of cobalt. The country has deposits of iron, zinc, lead and tin, as well as small scale gemstone mining from basement rock. The Ndola area has emerald, aquamarine, garnet and talc.

Lower Karoo rocks host coal, while Upper Karoo rocks contain uranium.^[4]

See also

• Bangweulu Block
• Mporokoso Group
• Hook granite massif
• Mwembeshi Shear Zone
• Zambezi Belt
• Lufilian Arc

References