[1] Geol Survey Norway, N-7491 Trondheim, Norway
[2] Tallinn Univ Technol, Inst Geol, EE-10243 Tallinn, Estonia
[3] CNRS, Ctr Rech Petrog & Geochim, F-54501 Vandoeuvre Les Nancy, France
[4] Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA
[5] Swedish Museum Nat Hist, SE-10405 Stockholm, Sweden
[6] George Washington Univ, Dept Earth & Environm Sci, Washington, DC 20052 USA