Geochemical and Petrological Insights into the Neoproterozoic Moumba Metabasites: Implications for Crustal Processes in the West Congo Belt (Republic of Congo)  

作　　者：Ulrich Verne Matiaba-Bazika Nelson Lekeba Makamba Vicky Tendresse Télange Bouénitéla Nicy Carmelle Bazebizonza Tchiguina Timothée Miyouna Florent Boudzoumou Ulrich Verne Matiaba-Bazika;Nelson Lekeba Makamba;Vicky Tendresse Télange Bouénitéla;Nicy Carmelle Bazebizonza Tchiguina;Timothée Miyouna;Florent Boudzoumou(Laboratory of Geosciences, Faculty of Sciences and Technics, Marien NGOUABI University, Brazzaville, Republic of Congo;National Institute for Research in Exact and Natural Sciences (IRSEN), Brazzaville, Republic of Congo;Geographid Research and Cartographic Production Center (CERGEC), Brazzaville, Republic of Congo)

机构地区：[1]Laboratory of Geosciences, Faculty of Sciences and Technics, Marien NGOUABI University, Brazzaville, Republic of Congo [2]National Institute for Research in Exact and Natural Sciences (IRSEN), Brazzaville, Republic of Congo [3]Geographid Research and Cartographic Production Center (CERGEC), Brazzaville, Republic of Congo

出　　处：《Journal of Geoscience and Environment Protection》2024年第2期1-29,共29页地球科学和环境保护期刊（英文）

摘　　要：The West Congo Belt contains in its rocks of Neoproterozoic age from Nemba complex outcropping in the Moumba River. This West Congo belt is made up of a crustal segment of the Arcuaï-West Congo orogen which extends from southwest Gabon to the northeast of Angola. This study aims to constrain the geochemical signature Nemba complex of West Congo belt from the petrograhic and geochemical study on the whole rock. The petrographic data from this study show the Moumba metabasites are made up of amphibolites, metagabbros, epidotites and greenschists interstratified in the Eburnean metasediments and affected by mesozonal to epizonal metamorphism characterized by the retromorphosis of intermediate amphibolite facies minerals into greenschist facies. Whole-rock geochemical data indicate that these metabasites are continental flood basalts (CFB) of basic nature and transitional affinity emplaced in intraplate context. These continental flood basalts are generated from magma originating from a significantly enriched shallow mantle plume and this magma then contaminated by the continental crust during their ascent. The reconstruction of tectonic signature suggests that West Congo belt would result from closure of an ocean basin with subduction phenomena. This collision would be marked by the establishment of ophiolite complex. We show that this model is incompatible with the CFB nature of metabasites and the orogenic evolution of Neoproterozoic. It does not seem that we can evoke a genetic link with a subduction of oceanic crust, because the paleogeography of Neoproterozoic (Rodinia) is marked by intracontinental rifts linked to opening of Rodinia. We therefore suggest the non-existence of ophiolitic complex in western Congo belt and reject the collisional model published by certain authors. We confirm the currently available intracontinental orogen model.The West Congo Belt contains in its rocks of Neoproterozoic age from Nemba complex outcropping in the Moumba River. This West Congo belt is made up of a crustal segment of the Arcuaï-West Congo orogen which extends from southwest Gabon to the northeast of Angola. This study aims to constrain the geochemical signature Nemba complex of West Congo belt from the petrograhic and geochemical study on the whole rock. The petrographic data from this study show the Moumba metabasites are made up of amphibolites, metagabbros, epidotites and greenschists interstratified in the Eburnean metasediments and affected by mesozonal to epizonal metamorphism characterized by the retromorphosis of intermediate amphibolite facies minerals into greenschist facies. Whole-rock geochemical data indicate that these metabasites are continental flood basalts (CFB) of basic nature and transitional affinity emplaced in intraplate context. These continental flood basalts are generated from magma originating from a significantly enriched shallow mantle plume and this magma then contaminated by the continental crust during their ascent. The reconstruction of tectonic signature suggests that West Congo belt would result from closure of an ocean basin with subduction phenomena. This collision would be marked by the establishment of ophiolite complex. We show that this model is incompatible with the CFB nature of metabasites and the orogenic evolution of Neoproterozoic. It does not seem that we can evoke a genetic link with a subduction of oceanic crust, because the paleogeography of Neoproterozoic (Rodinia) is marked by intracontinental rifts linked to opening of Rodinia. We therefore suggest the non-existence of ophiolitic complex in western Congo belt and reject the collisional model published by certain authors. We confirm the currently available intracontinental orogen model.

关 键 词：Mayombe METABASITES Moumba Mantle Plume Continental Rifting Basalts Flood Continental 

分 类 号：P58[天文地球—岩石学]