The Chang' an is one of the largest gold deposits in the southern Ailaoshan metallogenic belt in Sanjiang region, and the occurrence of ore bodies is controlled by the brittle fractured zone of Ganhe fault. The ore-forming fluid system is characterized by low to moderate temperature and salinity. The fluid compositions are dominated by H(2)O, CO(2), Cl(-), K(+) and Na(+), and the CO(2) content in main metallogenic stage varies between 21. 162mo1% similar to 32. 832mol%. The delta(13)C(CO2) values of the fluid system are -3. 427 parts per thousand similar to 8. 749 parts per thousand, indicating the participation of marine carbonate and magmatism. The 811) value varies from -111 parts per thousand to -78. 383 parts per thousand, the delta(18)O values are 10. 527 parts per thousand similar to 13. 565 parts per thousand and the delta(34)S value is concentrated between +1 parts per thousand and +3 parts per thousand, which suggesting the ore-forming fluid probably sourced from the magmatic-hydrothermal system, and the metamorphic water sourced from marine carbonate strata also played an important role in the main mineralization stage. In Cenozoic, the large scale upward alkali-rich magma caused the magmatic hydrothermal fluid to circulate and mix with the metamorphic water in the Jinping area of the southern Ailaoshan belt. The mixed fluid extracted gold and other metallogenetic elements from the wall rock and other geological unites, then migrated them to the proper structural spaces, and rapidly precipitated under some favorable physical-chemical condition, finally formed the micro disseminated gold deposit. According to the comprehensive and contrastive study, the Chang' an gold deposit possesses the typical geological-geochemical characteristics of orogenic-type gold deposit and Carlin-type gold deposit, so it should belong to the Carlin-like gold deposit as a transitional type between orogenic-type and Carlin-type gold deposit.
