The geology of Malawi formed on extremely ancient crystalline basement rock, which was metamorphosed and intruded by igneous rocks during several orogeny mountain building events in the past one billion years. The rocks of the Karoo Supergroup and newer sedimentary units deposited across much of Malawi in the last 251 million years, in connection with a large rift basin on the supercontinent Gondwana and the more recent rifting that has created the East African Rift, which holds Lake Malawi. The country has extensive mineral reserves, many of them poorly understood or not exploited, including coal, vermiculite, rare earth elements and bauxite. [1]
The oldest rocks in Malawi are crystalline metamorphic basement rocks in the south that formed nearly two billion years ago. The oldest rocks may have originated from marine sediments and igneous rocks, based on the presence of marble. The Rusizi-Ubendia orogeny, a mountain building event 1.8 billion years ago in the Paleoproterozoic deformed and metamorphosed the rocks in the north of the country, affecting a large swath of what is now central Africa including southern Tanzania, northern Zambia, Burundi, Rwanda and the Democratic Republic of the Congo.
The region affected by the Mozambique orogeny may have extended as far south as the Limpopo Orogenic Belt in South Africa, but subsequent tectonic activity has erased traces in the rock. [2]
The Irumide orogeny began 1.6 billion years ago, at the start of the Mesoproterozoic and continued until 900 million years ago. The event caused regional deformation, metamorphism and igneous intrusions preserved in northern Malawi, Tanzania and Zambia. The Nyika granite and perhaps also the Dzalanyama granite emplaced in the north, followed by the mudstones, sandstones and conglomerates of the Mafingi Group, which deposited in a shallow marine environment. The Dzalanyama granite intruded into the preexisting Mchinji Group calcareous mudstones. [2]
The Mozambique orogeny began in the Neoproterozoic, subdivided by structural geologists into the Katangan and Damaran episode. Basement rocks were deformed and metamorphosed, in many cases forming migmatites. The event produced large areas of high-grade metamorphism in southern Malawi, producing rocks such as charnockite granulites, gneiss, hornblende schist and biotite. Perthite gneisses and granulites formed in areas with isoclinal folding. The Mchinji Group experienced some low-grade metamorphism. [2]
As the Mozambique orogeny came to an end, brittle deformation produced phyllonite in older gneisses in northern Malawi. Granite, syenite and nepheline syenite intruded rocks and the Mafingi Group experienced low-grade metamorphism. [2]
In the Permian a large rift valley opened up across the southern part of the supercontinent Gondwana, spanning into what is now southern South America. Throughout the Mesozoic, the basin filled with sediments forming the Karoo Supergroup, the most extensive sedimentary unit in southern Africa. In Malawi, the Karoo Supergroup deposited between the Permian and the Late Jurassic, creating sequences of mudstone, sandstone, marl and even coal seams. Sediment deposition was followed by dolerite intrusions and basalt flows in southern Malawi, which now comprise the Stormberg Group.
In the Late Jurassic and Early Cretaceous, carbonatites, feldspar, granulites and feldspathoid syenites intruded, forming the Chilwa Alkaline Province in southern Malawi. The Zomba Mountains and Mulanje Mountains both formed during this period as ring complexes related to the intrusion. Complex faulting created opportunities for sediment to accumulate in fault troughs, generating the dinosaur beds in the north and calcareous sandstones in the south. [3]
With the creation of the East Africa Rift beginning in the late Mesozoic, fault-trough sedimentation created the Sungwa Bed, Chitimwe Bed and Chiwondo Beds in the Paleogene, Neogene and Quaternary. These three beds preserve the early sedimentation of Lake Malawi. The water surface was probably 300 meters higher above sea level than it is presently, confined to an area a quarter of its present size in the north.
Geologists believe that down-faulting allowed the lake water to flow to lower elevations, extending to Cape Maclear Peninsula. The Dwangwa gravels, found along the shores of the lake are probably remnant beach deposits. The Songwe Volcanoes in northern Malawi erupted in the Pleistocene. [3]
After the Karoo Supergroup rocks deposited in tectonically controlled basins, the rocks were down-faulted into several normal fault troughs in northern and southwestern Malawi. Down-faulting in the late Mesozoic through the Cenozoic formed the East Africa Rift, which filled in with Lake Malawi and other lakes. The Rift Valley continues from the Zambezi River to the Red Sea.
Precambrian crystalline basement rock is the main groundwater source underlying Malawi. Although permeability is low, the water is generally good quality except in places where it encounters and dissolves evaporite deposits where it can have high salinity. Unconsolidated saprolite forms a weathered, unconfined aquifer in Precambrian material between 15 and 30 meters thick in plateau areas. Well-sorted, unconsolidated alluvial and lake bed sediments are important near surface aquifers in parts of the country, with water five to 10 meters below ground, but they tend to be more mineralized than water from basement rock. In fact, groundwater is not potable in the Shire Valley and Bwanje Valley due to high salinity from dissolved evaporates.
Plutonic rocks contain hardly any groundwater and Karoo Supergroup sedimentary rocks are usually too cemented to have much permeability, except for small quantities of water 20 to 30 meters below the surface. Malawi has some locally productive aquifers in weather fractures around lava flows in the Stormberg volcanic rocks as well as Cretaceous and Quaternary sedimentary rocks.
Malawi has extensive mineral reserves, but most are undeveloped. The Songwe Carbonatite and the Kangankunde Carbonatite near Mulanje and Ntcheu respectively, each contain rare earth elements as well as pyrochlore, barite, apatite and strontianite. Seventy five kilometers west of Blantyre there is a uranium deposit at Thambani. Mpatamanga in the same area has commercially viable vermiculite deposits.
Historically, Malawi imported coal from Mozambique even though coal deposits were known in the north. There are now two coal mines on the Livingstonia Coalfield. Bauxite is found on the Mlanje syenographic massif, 25 kilometers northeast of Mlanje. Unexploited deposits of porcelain clay, graphite and sand usable for silicon production exist throughout the country. Geologists are in the process of exploring for hydrocarbons, gold, gypsum, chromite, copper, nickel, rutile and salt. [4]
The geology of Somalia is built on more than 700 million year old igneous and metamorphic crystalline basement rock, which outcrops at some places in northern Somalia. These ancient units are covered in thick layers of sedimentary rock formed in the last 200 million years and influenced by the rifting apart of the Somali Plate and the Arabian Plate. The geology of Somaliland, the de facto independent country recognized as part of Somalia, is to some degree better studied than that of Somalia as a whole. Instability related to the Somali Civil War and previous political upheaval has limited geologic research in places while heightening the importance of groundwater resources for vulnerable populations.
The geology of Ghana is primarily very ancient crystalline basement rock, volcanic belts and sedimentary basins, affected by periods of igneous activity and two major orogeny mountain building events. Aside from modern sediments and some rocks formed within the past 541 million years of the Phanerozoic Eon, along the coast, many of the rocks in Ghana formed close to one billion years ago or older leading to five different types of gold deposit formation, which gave the region its former name Gold Coast.
The geology of the Democratic Republic of the Congo is extremely old, on the order of several billion years for many rocks. The country spans the Congo Craton: a stable section of ancient continental crust, deformed and influenced by several different mountain building orogeny events, sedimentation, volcanism and the geologically recent effects of the East Africa Rift System in the east. The country's complicated tectonic past have yielded large deposits of gold, diamonds, coltan and other valuable minerals.
The geology of Ivory Coast is almost entirely extremely ancient metamorphic and igneous crystalline basement rock between 2.1 and more than 3.5 billion years old, comprising part of the stable continental crust of the West African Craton. Near the surface, these ancient rocks have weathered into sediments and soils 20 to 45 meters thick on average, which holds much of Ivory Coast's groundwater. More recent sedimentary rocks are found along the coast. The country has extensive mineral resources such as gold, diamonds, nickel and bauxite as well as offshore oil and gas.
The geology of Lesotho is built on ancient crystalline basement rock up to 3.6 billion years old, belonging to the Kaapvaal Craton, a section of stable primordial crust. Most of the rocks in the country are sedimentary or volcanic units, belonging to the Karoo Supergroup. The country is notable for large fossil deposits and intense erosion due to high rainfall and a rare case of southern African glaciation during the last ice age. Lesotho has extensive diamonds and other natural resources and has the highest concentration of kimberlite pipes anywhere in the world.
The geology of Mauritania is built on more than two billion year old Archean crystalline basement rock in the Reguibat Shield of the West African Craton, a section of ancient and stable continental crust. Mobile belts and the large Taoudeni Basin formed and filled with sediments in the connection with the Pan-African orogeny mountain building event 600 million years ago and a subsequent orogeny created the Mauritanide Belt. In the last 251 million years, Mauritania has accumulated additional sedimentary rocks during periods of marine transgression and sea level retreat. The arid country is 50% covered in sand dunes and has extensive mineral resources, although iron plays the most important role in the economy.
The geology of Mozambique is primarily extremely old Precambrian metamorphic and igneous crystalline basement rock, formed in the Archean and Proterozoic, in some cases more than two billion years ago. Mozambique contains greenstone belts and spans the Zimbabwe Craton, a section of ancient stable crust. The region was impacted by major tectonic events, such as the mountain building Irumide orogeny, Pan-African orogeny and the Snowball Earth glaciation. Large basins that formed in the last half-billion years have filled with extensive continental and marine sedimentary rocks, including rocks of the extensive Karoo Supergroup which exist across Southern Africa. In some cases these units are capped by volcanic rocks. As a result of its complex and ancient geology, Mozambique has deposits of iron, coal, gold, mineral sands, bauxite, copper and other natural resources.
The geology of Niger comprises very ancient igneous and metamorphic crystalline basement rocks in the west, more than 2.2 billion years old formed in the late Archean and Proterozoic eons of the Precambrian. The Volta Basin, Air Massif and the Iullemeden Basin began to form in the Neoproterozoic and Paleozoic, along with numerous ring complexes, as the region experienced events such as glaciation and the Pan-African orogeny. Today, Niger has extensive mineral resources due to complex mineralization and laterite weathering including uranium, molybdenum, iron, coal, silver, nickel, cobalt and other resources.
The geology of Sierra Leone is primarily very ancient Precambrian Archean and Proterozoic crystalline igneous and metamorphic basement rock, in many cases more than 2.5 billion years old. Throughout Earth history, Sierra Leone was impacted by major tectonic and climatic events, such as the Leonean, Liberian and Pan-African orogeny mountain building events, the Neoproterozoic Snowball Earth and millions of years of weathering, which has produced thick layers of regolith across much of the country's surface.
The geology of Tanzania began to form in the Precambrian, in the Archean and Proterozoic eons, in some cases more than 2.5 billion years ago. Igneous and metamorphic crystalline basement rock forms the Archean Tanzania Craton, which is surrounded by the Proterozoic Ubendian belt, Mozambique Belt and Karagwe-Ankole Belt. The region experienced downwarping of the crust during the Paleozoic and Mesozoic, as the massive Karoo Supergroup deposited. Within the past 100 million years, Tanzania has experienced marine sedimentary rock deposition along the coast and rift formation inland, which has produced large rift lakes. Tanzania has extensive, but poorly explored and exploited natural resources, including coal, gold, diamonds, graphite and clays.
The geology of Uganda extends back to the Archean and Proterozoic eons of the Precambrian, and much of the country is underlain by gneiss, argillite and other metamorphic rocks that are sometimes over 2.5 billion years old. Sedimentary rocks and new igneous and metamorphic units formed throughout the Proterozoic and the region was partially affected by the Pan-African orogeny and Snowball Earth events. Through the Mesozoic and Cenozoic, ancient basement rock has weathered into water-bearing saprolite and the region has experienced periods of volcanism and rift valley formation. The East Africa Rift gives rise to thick, more geologically recent sediment sequences and the country's numerous lakes. Uganda has extensive natural resources, particularly gold.
The geological history of Zambia begins in the Proterozoic eon of the Precambrian. The igneous and metamorphic basement rocks tend to be highly metamorphosed and may have formed earlier in the Archean, but heat and pressure has destroyed evidence of earlier conditions. Major sedimentary and metamorphic groups formed in the mid-Proterozoic, followed by a series of glaciations in the Neoproterozoic and much of the Paleozoic which deposited glacial conglomerate as well as other sediments to form the Katanga Supergroup and rift-related Karoo Supergroup. Basalt eruptions blanketed the Karoo Supergroup in the Mesozoic and Zambia shifted to coal and sandstone formation. Geologically recent windblown sands from the Kalahari Desert and alluvial deposits near rivers play an important role in the modern surficial geology of Zambia. The country has extensive natural resources, particularly copper, but also cobalt, emeralds, other gemstones, uranium and coal.
The geology of Somaliland is very closely related to the geology of Somalia. Somaliland is a de facto independent country within the boundaries that the international community recognizes as Somalia. Because it encompasses the former territory of British Somaliland, the region is historically better researched than former Italian Somaliland. Somaliland is built on more than 700 million year old igneous and metamorphic crystalline basement rock.. These ancient units are covered in thick layers of sedimentary rock formed in the last 200 million years and influenced by the rifting apart of the Somali Plate and the Arabian Plate.
The geology of Eswatini formed beginning 3.6 billion years ago, in the Archean Eon of the Precambrian. Eswatini is the only country entirely underlain by the Kaapvaal Craton, one of the oldest pieces of stable continental crust and the only craton regarded as "pristine" by geologists, other than the Yilgarn Craton in Australia. As such, the country has very ancient granite, gneiss and in some cases sedimentary rocks from the Archean into the Proterozoic, overlain by sedimentary rocks and igneous rocks formed during the last 539 million years of the Phanerozoic as part of the Karoo Supergroup. Intensive weathering has created thick zones of saprolite and heavily weathered soils.
The geology of Morocco formed beginning up to two billion years ago, in the Paleoproterozoic and potentially even earlier. It was affected by the Pan-African orogeny, although the later Hercynian orogeny produced fewer changes and left the Maseta Domain, a large area of remnant Paleozoic massifs. During the Paleozoic, extensive sedimentary deposits preserved marine fossils. Throughout the Mesozoic, the rifting apart of Pangaea to form the Atlantic Ocean created basins and fault blocks, which were blanketed in terrestrial and marine sediments—particularly as a major marine transgression flooded much of the region. In the Cenozoic, a microcontinent covered in sedimentary rocks from the Triassic and Cretaceous collided with northern Morocco, forming the Rif region. Morocco has extensive phosphate and salt reserves, as well as resources such as lead, zinc, copper and silver.
The geology of Sudan formed primarily in the Precambrian, as igneous and metamorphic crystalline basement rock. Ancient terranes and inliers were intruded with granites, granitoids as well as volcanic rocks. Units of all types were deformed, reactivated, intruded and metamorphosed during the Proterozoic Pan-African orogeny. Dramatic sheet flow erosion prevented almost any sedimentary rocks from forming during the Paleozoic and Mesozoic. From the Mesozoic into the Cenozoic the formation of the Red Sea depression and complex faulting led to massive sediment deposition in some locations and regional volcanism. Sudan has petroleum, chromite, salt, gold, limestone and other natural resources.
The geology of Nigeria formed beginning in the Archean and Proterozoic eons of the Precambrian. The country forms the Nigerian Province and more than half of its surface is igneous and metamorphic crystalline basement rock from the Precambrian. Between 2.9 billion and 500 million years ago, Nigeria was affected by three major orogeny mountain-building events and related igneous intrusions. Following the Pan-African orogeny, in the Cambrian at the time that multi-cellular life proliferated, Nigeria began to experience regional sedimentation and witnessed new igneous intrusions. By the Cretaceous period of the late Mesozoic, massive sedimentation was underway in different basins, due to a large marine transgression. By the Eocene, in the Cenozoic, the region returned to terrestrial conditions.
The geology of South Korea includes rocks dating to the Archean and two large massifs of metamorphic rock as the crystalline basement, overlain by thick sedimentary sequences, younger metamorphic rocks and volcanic deposits. Although extent is small, Geology is diverse, and there are diverse rocks that were formed during the Precambrian to Cenozoic Era in the Korea Peninsula.
The geology of North Korea has been studied by the Central Geological Survey of Mineral Resources, rare international research and by inference from South Korea's geology.
The geology of Newfoundland and Labrador includes basement rocks formed as part of the Grenville Province in the west and Labrador and the Avalonian microcontinent in the east. Extensive tectonic changes, metamorphism and volcanic activity have formed the region throughout Earth history.