TY - JOUR
T1 - Archean evolution of the Leo Rise and its Eburnean reworking
AU - Thiéblemont, Denis
AU - Goujou, Jean Christian
AU - Egal, Emmanuel
AU - Cocherie, Alain
AU - Delor, Claude
AU - Lafon, Jean Michel
AU - Fanning, C. Mark
PY - 2004/6
Y1 - 2004/6
N2 - Recent geological mapping in southeastern Guinea, supported by zircon dating, has called into question traditional understanding concerning the evolution of the Leo Rise. Gneiss dated at about 3540 Ma appears to constitute the earliest evidence for continental accretion within the Leo Rise. The existence of a Leonian depositional cycle at about 3000 Ma is confirmed, marked by volcanic and sedimentary rocks that can be correlated with the Loko Group in Sierra Leone. The span of ages (3244-3050 Ma) suggests that the Leonian cycle comprises different episodes whose respective chronology is as yet uncertain. Clearly distinct from the Leonian cycle, the Liberian cycle (∼2900-2800 Ma) is represented in Guinea by granite and migmatite (∼2910-2800 Ma), reflecting remobilization of the ancient Archean basement and deformation of the Leonian rocks; no deposition is associated with this cycle. After the Liberian, the Nimba and Simandou successions, containing Liberian detrital zircons, are assigned to the Birimian (∼2200-2000 Ma). Finally, Eburnean tectonism caused intense deformation of the Archean craton, accompanied by high-grade metamorphism and the intrusion of granite and syenite with ages between 2080 and 2020 Ma. The evolution of the Kénéma-Man domain, attributed to the cumulated effect of the Leonian and Liberian cycles, is thus in part Eburnean. We can suppose, therefore, that the NNE-SSW-trending structures attributed to the Liberian in Sierra Leone are, in fact, Eburnean. The Kambui Supergroup, also affected by this tectonism, should thus be assigned to the Birimian rather than the Liberian, which would explain its similarities with the Nimba and Simandou successions.
AB - Recent geological mapping in southeastern Guinea, supported by zircon dating, has called into question traditional understanding concerning the evolution of the Leo Rise. Gneiss dated at about 3540 Ma appears to constitute the earliest evidence for continental accretion within the Leo Rise. The existence of a Leonian depositional cycle at about 3000 Ma is confirmed, marked by volcanic and sedimentary rocks that can be correlated with the Loko Group in Sierra Leone. The span of ages (3244-3050 Ma) suggests that the Leonian cycle comprises different episodes whose respective chronology is as yet uncertain. Clearly distinct from the Leonian cycle, the Liberian cycle (∼2900-2800 Ma) is represented in Guinea by granite and migmatite (∼2910-2800 Ma), reflecting remobilization of the ancient Archean basement and deformation of the Leonian rocks; no deposition is associated with this cycle. After the Liberian, the Nimba and Simandou successions, containing Liberian detrital zircons, are assigned to the Birimian (∼2200-2000 Ma). Finally, Eburnean tectonism caused intense deformation of the Archean craton, accompanied by high-grade metamorphism and the intrusion of granite and syenite with ages between 2080 and 2020 Ma. The evolution of the Kénéma-Man domain, attributed to the cumulated effect of the Leonian and Liberian cycles, is thus in part Eburnean. We can suppose, therefore, that the NNE-SSW-trending structures attributed to the Liberian in Sierra Leone are, in fact, Eburnean. The Kambui Supergroup, also affected by this tectonism, should thus be assigned to the Birimian rather than the Liberian, which would explain its similarities with the Nimba and Simandou successions.
KW - Archean
KW - Birimian
KW - Eburnean
KW - Guinea
KW - Leo Rise
KW - Leonian
KW - Liberian
KW - W-Africa
UR - http://www.scopus.com/inward/record.url?scp=8644268883&partnerID=8YFLogxK
U2 - 10.1016/j.jafrearsci.2004.07.059
DO - 10.1016/j.jafrearsci.2004.07.059
M3 - Article
SN - 1464-343X
VL - 39
SP - 97
EP - 104
JO - Journal of African Earth Sciences
JF - Journal of African Earth Sciences
IS - 3-5
ER -