Neoproterozoic crustal evolution in Southern Chad: Pan-African ocean basin closing, arc accretion and late- to post-orogenic granitic intrusion

Abstract

In the Lake Léré region, southern Chad, Neoproterozoic terrains are distributed in four lithostructural groups that reveal the geotectonic evolution of a part of the Pan-African orogenic domain. The first group includes basaltic volcanic rocks and fine-grained detrital sedimentary rocks of pre-tectonic basins that were emplaced in an extensional regime, close to a volcanic arc. The second and third groups include calc-alkaline gabbroic intrusions emplaced at an upper crustal level and a midcrustal tonalite, respectively, that are interpreted to be the roots of an active margin volcanic arc. These first three groups experienced WNW to ESE compression, and may belong to a fore-arc basic-volcanic arc-back-arc basin system that was accreted eastward to the Palaeoproterozoic Adamaoua-Yadé Block. The fourth group includes post-tectonic granite plutons invading the older groups. This paper documents the accretion processes in the southern margin of the Saharan Metacraton.

Geophysical Signature Location in the South-West of Chad: Structural Implications

“…This regional pressure, related to the major direction (Figure 10) of the gravity lineaments, is in line with the Panafrican faults which are similar to those observed at the edge of the West African crater and which are said to have played an essential role in controling the geodynamic evolution of the region région [34][35][36]. The tectonic evolution of this region leads to the understanding that the Precambrian was marked by the putting in place of great fractures which is the result of a compressive tectonic corresponding to the Panafrican orogenic.…”

Polyphase deformation in the Mbé - Sassa-Bersi area: Implications on the tectono-magmatic history of the area and the tectonic evolution of the Tcholliré-Banyo and Central Cameroon Shear Zones (Central North Cameroon)

“…The RBGB is made of mafic to intermediate and felsic metavolcanic rocks; and by metasedimentary rocks all metamorphosed under low grade at 600 Ma [28,29]. The RBGB is actually considered as remnants of back arc basin [30,31] related to the TBSZ. The mylonitic hornblende-biotite gneiss of Mbé quarry which have been dated at 580 ± 11 Ma (U-Pb titanite age) was interpreted as dating the minimum age of sinistral deformation event in this area [25].…”

The dolerite dyke swarm of Mongo, Guéra Massif (Chad, Central Africa): Geological setting, petrography and geochemistry

“…Petrological and structural similarities between Mongo [8], Mayo Kebbi [4,7] and Léré basements in Southern Chad [5] suggest that these regions are parts of the same terrane, which was welded during the Pan-African orogeny to the Adamawa-Yadé Domain [21], i.e. outside of the "Saharan metacraton".…”

“…Precambrian massifs are exposed in Chad as five terranes (review in [1]): Tibesti to the north [2], Waddai to the east, Mbaibokoum, or Yade, to the south [3], Mayo Kebbi to the south-west [4][5][6][7] ( Figure 1A) and Guéra to the south [8]. Mayo-Kebbi and Mbaibokoum/Yade constitute terranes of the Neoproterozoic Central African Orogenic Belt (CAOB) [4,5].…”

“…Mayo-Kebbi and Mbaibokoum/Yade constitute terranes of the Neoproterozoic Central African Orogenic Belt (CAOB) [4,5]. Tibesti, Waddaï and Guera are parts of a large area coined by [9] as the "Saharan Metacraton", defined as "a craton that has been remobilized during an orogenic event but that is still recognizable dominantly through its rheological, geochronological and isotopic characteristics" [9].…”