1. College of Earth Sciences��Jilin University��Changchun�� 130061��China; 2. Shandong Gold Geological Minerals Survey Co. ��Ltd��Chifeng 024005��Inner Mongolia��China; 3. Inner Mongolia Chifeng Institute of Geology and Mineral Exploration and Development��Chifeng��Inner Mongolia�� 024000

The Baiyinnuo'er Pb- - Zn mineral deposit is a large skarn- type deposit�� The mineralization is in two periods and five stages�� The research on fluid inclusion micro- thermometry indicates that in the stage ��- 1 are mainly developed the aqueous two- phase inclusions�� vapor- rich inclusions and NaCl daughter mineral- bearing three- phase fluid inclusions�� The homogenization temperatures of aqueous two- phase fluid inclusions range from 375. 4 �� to 479. 8 �棬and the salinity varies from 10. 73%to 13. 73%NaCleqv�� The homogenization temperatures of vapor- rich fluid inclusions range from 415. 2�� to 458. 4�棬and the salinity varies from 5. 32% to 7. 67%NaCleqv�� The homogenization temperatures of NaCl daughter mineral- bearing three- phase fluid inclusions range from 434. 6�� to 497. 5�棬and the salinity varies from 42. 15% to 45. 25% NaCleqv�� The fluid inclusions of stage ��- 1 belong to the immiscible NaCl �� H 2 O hydrothermal system with medium- high temperature and high salinity�� Stage ��- 2 main- ly develops two types of fluid inclusions�� The homogenization temperatures of aqueous two- phase fluid inclusions range from 202. 3 �� to 345. 7 �棬and the salinity varies from 5. 17% to 11. 22% NaCleqv�� The homogenization temperatures of aqueous two- phase fluid inclusions range from 265. 7�� to 381. 9�棬and the salinity varies from 1. 98% to 5. 01 NaCleqv�� The fluid inclusions of stage ��- 2 belong to the immiscible NaCl �� H 2 O hydrothermal system with medium temperature and medium salinity�� In the stage ��- 2 (main metallogenic stage) are mainly de- veloped the aqueous two- phase fluid inclusions��in which the homogenization temperatures range from 165. 9�� to 258. 7�棬and the salinity varies from 0. 83% to 5. 62%NaCleqv�� The fact indicates that the fluid inclusions of the stage ��- 2 belong to the uniform NaCl �� H 2 O hydrothermal system with medium- low temperature and low salinity�� In the process of the evolution from the immiscible NaCl �� H 2 O hydrothermal system with medium- high temperature and high salinity to the uniform NaCl �� H 2 O hydrothermal system with medium- low temperature and low salinity�� the metallic element gradually enriches and forms the industrial ore body eventually�� The study on the C��H��O i- sotope in the fluid inclusions indicates that the early fluid mainly comes from magmatic water��with the participation of a small amount of atmospheric precipitation; and the main source of later fluid inclusions is atmospheric precipi- tation��