*Joachim JACOBS¹、Andreas LAEUFER²、Marlina ELBURG³、Wilfried JOKAT⁴ (1.Department of Earth Science, University of Bergen, PB 7803, N-5020 Bergen, Norway、2.Bundesanstalt fur Geowissenschaften und Rohstoffe (BGR), Stilleweg 2, D-30655 Hannover, Germany、3.Department of Geology, University of Johannesburg, Auckland Park 2006, Johannesburg, South Africa、4.Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germnay)