The geochronological evolution of the Paleoproterozoic Baoulé-Mossi domain of the Southern West African Craton

Abstract

Generation and emplacement of felsic magmas in the Paleoproterozoic Baoulé-Mossi domain of the West African Craton does not match the apparent peaks of global crust generation identified between ca. 2900-2600, 1900-1600 and 1200-900 Ma. In contrast, across the Baoulé-Mossi domain, the emplacement of felsic intrusions ranges from ca. 2300 to 2000 Ma. It has proven difficult to place this magmatism within a robust geodynamic framework due to the lack of accurate geochronological data from across the West African Craton. The present study addresses this issue by presenting eighty-four new felsic intrusions zircon ion microprobe and LA-ICP-MS U-Pb ages from areas that up until now have not been targeted for geochronology.The new dataset, when fully integrated with existing age data, reveals a craton-wide diachronous geochronological pattern characterized by a magmatic front that migrated westward. This migration proceeded at a rate of 35 km per million years, with an apparent offset of the initiation and cessation of felsic magmatic activity between the east and west of approximately 50 million years. The new data also show that although the entire Baoulé-Mossi domain was subject to continuous magmatic activity for approximately at least 150 million years, this magmatic activity displays a rather different record in the eastern and western portions of the domain. The differences are expressed as a westward migration of the magmatic activity, cessation of activity around ca. 2100 Ma (easternmost portion) and ca. 2050 Ma (westernmost portion) and a higher incidence of inherited ages in the westernmost portion when compared to the easternmost region. In addition, the new U-Pb data identify some of the oldest felsic intrusions in the region, including a granite from Burkina Faso (2265 ± 17 Ma) and a diorite porphyry (2216 ± Ma) in southern Mali. This study also reveals inherited Archean zircon cores from across southern Mali. The combination of the new data presented here, along with previously published data, suggests that the Baoulé-Mossi domain formed from the accretion of two major crustal blocks. The Archean inherited ages open a window for further investigation of the interaction between the Archean Kénéma-Man and the Paleoproterozoic Baoulé-Mossi domains.Rock classification was made based on 3 parameters: 1) hand specimen observations; 2) CIPW norm; and 3) modal composition determined from microscopic evaluation of thin sections, characterized after Streckeisen (1976) (Tables and 3). Zircon morphology and U-Pb datingZircon concentrates were obtained following the standard procedures described in Claoué-Long et al. (1995). Sample processing to obtain zircon concentrates, zircon mount procedures and zircon imaging, which include the use of backscattered electron (BSE) and cathodoluminescence (CL) detectors, are described in Appendix A1. Detailed information about U-Pb isotope analysis of zircon by SHRIMP (Appendix A2) and LA-ICP-MS (Appendix A3), the criteria for rejection of analyses and data reduction are explaine...

Detrital zircon U–Pb–Hf data from Cambrian sandstones of the Ougarta Mountains Algeria: Implication for palaeoenvironment

“…In previous studies, Cambrian–Ordovician successions along the northern Gondwana margin from Morocco in the west to Jordan in the east show prominent zircon groups between 750 and 530 Ma (Figure 7), with varying individual age peaks, including 1,100–950 Ma, 2,150–1,750 Ma, and 2,700–2,500 Ma (Meinhold et al, 2013). In this study, the ~618 Ma dominant age peak of the Ougarta Cambrian sandstone samples is consistent with the 750–530 Ma age peak identified in the WAC (Abati et al, 2012; Linnemann et al, 2011; Linnemann, Gerdes, Hofmann, & Marko, 2014; Parra‐Avila et al, 2017; Petersson, Schersten, Kristinsdottir, Kemp, & Whitehouse, 2018), and the secondary age peak of 2,035 Ma is consistent with the age of the Eburnean orogen in the WAC (Grenholm, Jessell, & Thébaud, 2019; Ikenne, Souhassou, Arai, & Soulaimani, 2017; Linnemann et al, 2011). Thus, the data from the Ougarta are consistent with proximal provenance from the WAC.…”

New U–Pb zircon ages of Nyong Complex meta‐plutonites: Implications for the Eburnean/Trans‐Amazonian Orogeny in southwestern Cameroon (Central Africa)

“…As implicit in its name, this orogeny spans, like the Pan‐African/Brasiliano orogen, the Atlantic Ocean (e.g., Feybesse et al, 1998; Ledru, Johan, Milési, & Tegyey, 1994; Lerouge et al, 2006; Trompette, 1994). It encompasses the whole WCAFB (e.g., Feybesse et al, 1998; Lerouge et al, 2006; Loose & Schenk, 2018; Toteu et al, 1994), its South American equivalents, such as the Eastern Bahia and Mineiro belts (e.g., Aguilar et al, 2017; Alkmim & Wilson, 2017; Barbosa & Barbosa, 2017; Carvalho, Janasi, & Sayer, 2017), and its West African counterparts, the Ashanti‐Kumasi, Houndé, Lawra, Kédougou, Ouago‐Fitini, and Reguibat belts (e.g., Kouamelan et al, 1997; Lambert‐Smith et al, 2015; Parra‐Avila et al, 2017; Peucat et al, 2005).…”

“…It stretches across Cameroon, the Central African Republic, Equatorial Guinea, and Gabon, forming the West Central African Fold Belt (WCAFB; Boniface, Schenk, & Appel, 2012; Houketchang Bouyo, Pénaye, Mouri, & Toteu, 2019; Feybesse et al, 1998; Loose & Schenk, 2018; Nga Essomba et al, 2019; Thiéblemont, Callec, Fernandez‐Alonso, & Chène, 2018). Units equivalent to the Nyong Complex were mapped around the West African Shield, notably the Ashanti‐Kumasi, Houndé, Lawra, Kédougou, Ouago‐Fitini, and Reguibat belts (Kouamelan, Delor, & Peucat, 1997; Lambert‐Smith, Lawrence, Müller, & Treloar, 2015; Parra‐Avila et al, 2017; Peucat, Capdevila, Drareni, Mahdjoub, & Kahoui, 2005), and around the São Francisco Shield in Brazil, comprising the Eastern Bahia and Mineiro belts (Figure 1a; e.g., Aguilar et al, 2017; Alkmim & Wilson, 2017; Barbosa & Barbosa, 2017; Lopez, Cameron, & Jones, 2001; Neves et al, 2006).…”

Origin and tectonic significance of the metavolcanic rocks and mafic enclaves from the Palaeoproterozoic Birimian Terrane, SE West African Craton, Ghana

“…The identification of Archean zircons in the region therefore argues for greater interaction between the Baoulé-Mossi domain and the Archean Kénéma-Man domain. Additionally, zircon U-Pb dating and Hf and O-isotope studies of igneous rocks from the Palaeoproterozoic Baoulé-Mossi domain of the WAC, covering Burkina Faso, Ghana, Guinea and Mali, revealed the juvenile isotopic character of the domain, and further showed that the southern part of the WAC evolved by accretionary processes (Parra-Avila et al 2017. Similar to the above, zircon U-Pb age and Lu-Hf isotopic data from granites of southern, southeastern and northwestern Ghana suggest juvenile crustal addition with a short period of reworking of Archaean crust within the Palaeoproterozoic Birimian Terrane of Ghana, and provides evidence of subductionrelated crustal growth (Petersson et al 2016(Petersson et al , 2018.…”