New insight into the Dahomeyide Belt of southeastern Ghana, West Africa: Evidence of arc-continental collision and Neoarchaean crustal reworking

摘要: Abstract This study presents petrography, geochemistry, geochronology, and Lu-Hf isotope compositions of Paleoproterozoic orthogneisses from the Dahomeyide Belt, southeastern Ghana. Previous studies indicated that these rocks represent part Birimian West African Craton, remobilized during Pan-African Orogen. The results obtained this indicate basement are mainly amphibole biotite medium-K, tonalitic composition, muscovite bearing high-K granodioritic composition. Both suites magnesian, calc-alkaline, metaluminous to weak peraluminous with A/CNK values 0.86 – 1.03. They rich in LREEs, LILEs heat-producing elements (Ba, K, Pb, Sr). moderately V Zn show variable (La/Yb)N Sr/Y ratios geochemical characteristics akin Neoarchaean sanukitoids. However, they depleted Ni Cr relative Zircon U-Pb ages determined on two amphibole-biotite four biotite-muscovite yield 2145 ± 12 Ma 2122 27 2105 18 2125 25 respectively. eHf(∼2.1Ga) -9.5 -3.7, pointing mean model (TDM1) 2721 24 2761 14 T(DM2) 3053 26 3125 Ma. Similarly, present -10.6 -1.7, corresponding T(DM1) 2743 2733 20 2949 3111 36 data suggest derived partial melting lower crust sediments little or no mantle contribution. A collision between arc an unknown Archaean (possibly, now Belt) accounted for formation rocks. provides first evidence reworked Belt along eastern border Craton. Our serves as comprehensive supporting older crustal contribution geodynamic evolution juvenile Eburnean/Birimian