Petrographic and chronological characteristics and geological significance of Inkisi Formation sandstones from eastern margin of the west Congo Orogenic Belt

The West Congo Orogenic Belt is a part of Africa where the San Francisco Craton and Congo Craton converged and collided during the Pan African period. Its tectonic evolution has attracted the attention of scholars both domestically and internationally. Conducting research on the stratigraphy during this period is of great significance for exploring the tectonic evolution of the orogenic belt.Methods:This study selected the Inkisi Formation sandstone in the northwest of Angola in the foreland basin on the eastern edge of the orogenic belt as the research object, and conducted studies on chronology and petrology.Results: The minimum detrital zircon age in the Inkisi Formation sandstone is 588.0 ± 3. 0 Ma, and the discrimination diagram indicates that the sandstone was formed in a sedimentary basin under a collision background. The chemical alteration indices (CIA, CIW, PIA) of the Inkisi sandstone are 63. 34~73. 17, 70. 82~92. 29, and 65. 19~89. 56, the Sr/Ba values ranging from 0. 07 to 0. 24<0. 5.Conclusions: The petrological and chronological characteristics of the Inkisi sandstone indicate that it was formed in a basin related to collision environments in the context of active continental margins, and is a product of river sedimentary environments. Its source area was warm and humid ancient climate conditions, and the source rocks underwent low to moderate weathering. It is a response to the Pan African West Congo orogeny, and also suggests that the West Congo collisional orogeny continued during the Ediacaran—Early Cambrian period.