Upper-Crustal Emplacement Mode of the Neoproterozoic Ngwi Granites along the Central Cameroon Shear Zone, Adamawa–Yadé Domain, West-Central Cameroon: Implications for Regional Tectonic Control

Abstract

The Ngwi area, along the central Cameroon shear zone (CCSZ), features two-mica granite and hornblende–biotite granite intrusive into paragneisses and amphibolites. This work provides insights into the kinematic evolution and emplacement mechanism of the Ngwi pluton, highlighting the complex tectonic history of the region, with implications for understanding the Pan-African tectonics. Structural data analysis reveals: (i) D₁ flattening (∼622–613 Ma) defined by NW- to WNW-striking S₁ foliation in paragneisses; (ii) D₂ sinistral shearing (∼613–590 Ma) with NE–SW to NNE–SSW and NW–SE rotational evolution, developed S₂ foliation in host-rocks and S_m2 magmatic fabric in pluton; (iii) D₃ dextral shearing (∼585–540 Ma) with NE–SW to ENE–WSW and NW–SE rotational evolution, induced a mylonitic fabric towards the pluton margins. Microstructural and kinematic data analysis suggest the Ngwi pluton emplaced into a high-strain sheared crustal domain during the D₂–D₃ phases, with a continuous evolution from magmatic to solid-state deformation (i.e., 700°C ≤ T ≤ 300°C) under high-grade amphibolite to low-grade greenschist conditions. The pluton's emplacement likely occurred within tension gashes opened in the paragneiss host rocks under a sinistral transpressive tectonics along the CCSZ, consistent with similar shear zones in Chad, Central African Republic and northeastern Brazil.

Keywords

kinematic evolution / Ngwi granites / sinistral transpression / syn-kinematic pluton emplacement / tension gashes / central Cameroon shear zone

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2026 Geological Society of China.