U-Pb ages and geochemistry of granitoids from Prydz Bay, East Antarctica, and their tectonic significance

Voluminous granitic plutons from the Prydz Bay of East Antarctica were emplaced during the Pan-African period. Using LA-ICP-MS U-Pb zircon technique, the Dalkoy, Munro Kerr and Amanda granites were dated at 519 +/- 2Ma, 497 +/- 2Ma and 498 +/- 7Ma, respectively. All granitoids are geochemically characterized by having high total alkali contents, low Mg, Ca, Cr, Ni contents and high K2O/Na2O,FeOT/ (FeOT + MgO) and 10(4) Ga/Al ratios, in accord with A-type granites. These rocks also show LILE- and HREE-enriched patterns with variable trough at Sr, Nb-Ta, Ti and P, and have very low initial (epsilon Nd) (t) values and high initial Sr-87/Sr-86 ratios. This suggests that magmatism in Prydz Bay is probably related to the post-collisional orogeny, including lithospheric thinning, magmatic underplating and crustal extension. The occurrence of post-collisional A-type granitoids from Prydz Bay supports the suggestion that the Prydz Belt may represent a collisional orogen.