Abstract
The work is a vivid description of the structural relationship between brittle deformation of the Precambrian basement in the southern continental part of the Cameroon Line and intrusive Paleozoic and Mesozoic basalt dykes swarms. A multidisciplinary approach that involves a combination of remote sensing techniques and field studies show that the major trend of brittle structures correspond to well-known regional structures: N70°E (Adamawa Shear Zone), N135°E (upper Benue trend) and N30°E (Cameroon Volcanic Line) corresponding to E-W and N-S directions respectively. Basalt dykes are associated to NE-SW, E-W and NW-SE oriented fractures. An integration of the available information on brittle structures and basalt dykes directions suggest an emplacement of the Mesozoic and Paleozoic basalt dykes structurally controlled by Precambrian structures that were originated through Riedel’s fracture kinematic model with dextral strike-slip Adamawa Shear Zone as the main shear zone during late stage of the Pan-African collision. Spatially, the restriction of the basalt dykes to the corridor of the Adamawa Shear Zone indicate that a rejuvenation of Precambrian faults may very well be the origin of the dykes with possibility that they may have been reworked several times during the Phanerozoic eon.
Highlights
The presence of basalt dyke swarms in any region is a surface expression of fractures of lithospheric importance and inversely provides a better understanding of these fracture distribution in the earth: This is considered as vectors of fissural eruptions channeling magma from source chamber to the Earth’s surface
An integration of the available information on brittle structures and basalt dykes directions suggest an emplacement of the Mesozoic and Paleozoic basalt dykes structurally controlled by Precambrian structures that were originated through Riedel’s fracture kinematic model with dextral strike-slip Adamawa Shear Zone as the main shear zone during late stage of the Pan-African collision
Basalt dykes of Paleozoic and Mesozoic age intrude the Precambrian basement in West Cameroon (Figure 1 and Figure 2), a basement bearing two lineaments of regional importance: 1) the N70 ̊E striking Adamawa Shear Zone (ASZ) known as Central Cameroon Shear Zone (CCSZ) [25] which extends from the Gulf of Guinea in Central Africa to the Red Sea
Summary
The presence of basalt dyke swarms in any region is a surface expression of fractures of lithospheric importance and inversely provides a better understanding of these fracture distribution in the earth: This is considered as vectors of fissural eruptions channeling magma from source chamber to the Earth’s surface. 600 - 540 Ma) that involved the Congo-Sao Francisco Craton, West African Craton and Saharan Metacraton [1] [28] It is well-known as the prolongation into Africa of the Pernambuco Shear Zone of North East Brazil after palinspatic reconstructions [23] before the opening of the South Atlantic Ocean during the Mesozoic [2] [53], 2) the Cameroon Volcanic Line (CVL) with a N30 ̊E orientation that runs from the Atlantic Ocean in the Gulf of Guinea to Lake Chad over a distance of more than 1500 km. If abundant works document relations between the CVL and ASZ [19] [27] [31] [35], little is known concerning basalt dykes discovered only recently and for which the only information related to petrology and geochronology are available in [46] [47]
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