Cᵉ siècle av. J.-C.
Africa
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The Precambrian African basement is the ancient crustal foundation underlying most of the continent. It comprises granitic rocks, gneisses, schists, sedimentary sequences, ancient nuclei, cratons, and younger orogenic belts affected by deformation, metamorphism, and denudation. Its progressive stabilization created large durable crustal blocks, while associated cratons and belts became closely linked to Africa’s major mineral deposits.
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Le récit
The Precambrian basement forms the underlying foundation of most of Africa. It includes extensive areas of granitic rocks, gneisses, and schists, together with thick sedimentary sequences that in some places remained only gently folded and relatively little altered. The survival of nearly horizontal formations more than a billion years old illustrates the long-term stability of substantial parts of the African crust.
This stability should not be confused with geological inactivity. The basement records several episodes of deformation, orogenesis, metamorphism, and denudation, preserved as belts with distinctive trends and radiometric ages. Stabilization occurred progressively: some core areas became rigid earlier than others, while younger orogenic belts formed around older nuclei.
The oldest preserved nuclei contain rocks more than 2,500 million years old, with some reaching approximately 3,600 million years. Together with surrounding younger belts, they form crustal regions that have remained stable for at least 900 million years; these stable areas are known as cratons. Much of the continent’s mineral wealth is derived from this basement, and important ore deposits are associated genetically with major cratons and orogenic belts.
Large portions of the basement were affected by metamorphic episodes during the very late Precambrian or early Cambrian, approximately 600 to 500 million years ago. This process is often termed the Pan-African orogenesis. The extract identifies the basement not only as a geological foundation but also as a long-term source of mineral resources that later influenced exploration and economic development.
Cᵉ siècle av. J.-C.
Africa
Traduction non disponible · Original (anglais) · français indisponible
The Precambrian African basement is the ancient crustal foundation underlying most of the continent. It comprises granitic rocks, gneisses, schists, sedimentary sequences, ancient nuclei, cratons, and younger orogenic belts affected by deformation, metamorphism, and denudation. Its progressive stabilization created large durable crustal blocks, while associated cratons and belts became closely linked to Africa’s major mineral deposits.
Poursuivre l’exploration
Le récit
The Precambrian basement forms the underlying foundation of most of Africa. It includes extensive areas of granitic rocks, gneisses, and schists, together with thick sedimentary sequences that in some places remained only gently folded and relatively little altered. The survival of nearly horizontal formations more than a billion years old illustrates the long-term stability of substantial parts of the African crust.
This stability should not be confused with geological inactivity. The basement records several episodes of deformation, orogenesis, metamorphism, and denudation, preserved as belts with distinctive trends and radiometric ages. Stabilization occurred progressively: some core areas became rigid earlier than others, while younger orogenic belts formed around older nuclei.
The oldest preserved nuclei contain rocks more than 2,500 million years old, with some reaching approximately 3,600 million years. Together with surrounding younger belts, they form crustal regions that have remained stable for at least 900 million years; these stable areas are known as cratons. Much of the continent’s mineral wealth is derived from this basement, and important ore deposits are associated genetically with major cratons and orogenic belts.
Large portions of the basement were affected by metamorphic episodes during the very late Precambrian or early Cambrian, approximately 600 to 500 million years ago. This process is often termed the Pan-African orogenesis. The extract identifies the basement not only as a geological foundation but also as a long-term source of mineral resources that later influenced exploration and economic development.