Wang Tingyin,Wang Jinrong,Liu Jinkun,D epartment of Geology,Lanzhou U niversity,Lanzhou,GansuWang Shizheng,Ningxia Bureau of Geology and Mineral Resources,Yinchuan,Ningxiaand Wu Jiahong Shenyang Institute of Geology and Mineral Resources,Shenyang,Liaoning
Li Shuguang,Chen Yizhi,Department of Earth and Space Sciences,University of Science and Technology ofChina,Hefei,Anhui Zhang Zongqing,Ye Xiaojing,Institute of Geology,Chinese Academy of Geological Sciences,BeijingZhang Guowei,Guo Anlin,Department of Geology,Northwest University,Xi''''an,Shaanxiand S.R. HartDepartment of Geology and Geophysics,Woods Hole Oceanographic Institute,WoodsHole,MA 02543 USA
Yao Jianxin,Li Zishun,Zhan Lipei Institute of Geology,Chinese Academy of Geological Sciences,Beijingand Hao Weicheng Department of Geology,Peking University,Beijing