Bilinga Suite Gr

Granitic intrusion unit in the middle of the Loeme Super Gr. The Nyanga-Niari Basin in the northern part of the West Congo Belt on the western margin of the Congo Shield comprises two distinct geologic domains from west to east, i.e. the metasedimentary hinterland domain deposited on c. 1000–850 Ma magmatic Mabouine´ and Mayumba complexes, and the poorly constrained unmetamorphosed sedimentary foreland domain (Thie´blemont et al. 2009). The Mayumba basin is exposed on the Mabouine´ and Mayumba complexes.

Synonym: Bilinga Suite

References: Fullgraf et al., 2024; de Wit et al., 2015.

[Fig 1. Lithostratigraphic synthesis for the Neoproterozoic to Early Paleozoic period. Compiled after various authors (see text).Dotted lines between Banalia, Alolo and Galamboge formations: stratigraphic transition by recurrences.]

[Fig 2. Lithostratigraphic columns for the Congo Basin established using data from the 4 wells in the central part of the basin and outcrops on its NE margin (Lindi-Ubangi and Kisangani-Kindu region), compared with the West-Congo and Katanga stratigraphy.]

[Fig 3. Simplified geological map of Sub-Saharan Africa showing the Neoproterozoic basins on and around the Congo Shield (modified after De Waele et al. 2008). (LC) Lower Congo Basin, (Co) Comba Basin, (Sa) Sangha Basin, (Ny) Nyanga-Niari Basin, (An) Angola Basin, (SO) Semb-Ouesso Basin, (Ba) Ubangui Basin, (LiB) Likki-Bembe´ Basin, (Bk) Bakouma Basin, (Fou) Fouroumbala Basin, (Li) Lindi Basin, It Itombwe Basin, (Ma)Malagarazi-Bukoban Basin, (Mb) Sankuru-Mbuji-Mayi-Lomami-Lovoy Basin, (Lu) Luamba Group, (Kat) Katanga Basin, (RB) Ruwenzorian Belt, KaB) Karagwe-Ankole Belt, (RuB) Ruzisian Belt, (KiB) Kibaran Belt,(UB) Ubendian Belt, IB Irumide Belt]

[Fig. 4. Stratigraphic correlation between the Neoproterozoic sedimentary basins in Central Africa. Correlations based on Sr isotopic data, radiometric age constraints and revised lithological relationships]

Calc-alkaline intrusions; tonolitic to granitic Eburnean orogeny. Some component units are Les Saras granite gneiss, Bilinga and Bilala meta-tonalite (Fullgraf et al., 2024; de Wit et al., 2015).

Ca. 92% up in Rhyacian to ca. 8% up in Orosirian (2070 to 2030 Ma) on Fig. 21 of Fullgraf et al. (2024). Magmatic zircons from four samples of the Bilinga, Bilala and Les Saras intrusions yielded ages between 2028 ± 12 and 2048 ± 12 Ma, indicating (i) their origin in the late phase of the Eburnean orogeny (ii) the minimum age of the M1 event they post-date (iii) the maximum age of the M2 event that converted the intrusions into orthogneiss, and (iv) the minimum age of the M1 anatectic event that affected the country rock but was not recorded in the intrusions, with similar results dating the intrusions at 2049 ± 29 and 2060 ± 18 Ma (Fullgraf et al., 2024).