Detrital Zircon U-Pb Chronology of the Inkisi Formation in the Southwestern Margin of the Congo Basin:Constraints on Stratigraphic Age and Provenance
The Inkisi Formation is one of the earliest sedimentary strata in the Congo Basin after the Pan-African movement.The determination of stratigraphic age,provenance and tectonic evolution of Inkisi Formation is of great geological significance to the study of the evolution of Congo Basin.According to the U-Pb geochronology of detrital zircons from the Inkisi Formation,the formation age and Pan-African movement of the Inkisi Formation were constrained,and the provenance was discussed.Results show that the minimum ages of detrital zircons in the lower member and upper member of the Inkisi Formation are 526±6 Ma and 534±14 Ma,respectively.Furthermore,the weighted average age of the four youngest zircons is 532±9.4 Ma,which restricts the earliest deposition age of the Inkisi Formation.The Inkisi Formation is therefore assigned to the Early Cambrian and disassembled from the Neoproterozoic Xisto-Gresoso Group.In addition,the rocks of Inkisi Formation did not undergo metamorphism and deformation,indicating that it was formed after the Pan-African movement.The results of detrital zircon age spectrum show that the detrital zircons of Inkisi Formation have a wide age range,showing five age peaks:>2800 Ma,2800～2400 Ma,2100～1750 Ma,1500～900 Ma,and 850～500 Ma.By comparing the age peaks with the surrounding geologic bodies,it is concluded that the Western Congo Orogenic belt,Kasai Craton and Angola Craton are the main provenance,and the Lufilian tectonic belt is the secondary provenance.
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