1. Edinburgh Ion Microprobe Facility (EIMF), Department of Geology and Geophysics; University of Edinburgh; West Mains Road,; Edinburgh; EH9 3JW; United Kingdom
2. Scottish Universities Environmental Research Centre; Rankine Avenue,; Glasgow; G75 0QF; United Kingdom
3. Department of Chemistry and Physics; Arkansas State University; P.O. Box 1847,; State University; Arkansas; 72467; USA
4. Hanoi University of Mining and Geology; Dong Ngac, Tu Liem; Hanoi; Vietnam
5. Department of Geology and Geophysics; Woods Hole Oceanographic Institution; Woods Hole; Massachusetts; 02543; USA
6. Vietnam Petroleum Institute; Yen Hoa, Cau Giay; Hanoi; Vietnam