Abstract:

Balifang gold deposit, located in the northwest part of Heilongjiang Province, is one of the recently discovered gold deposits. The ore bodies are hosted in the diorite and arkose of the Middle Jurassic Emuerhe Formation. The ore types include gold and pyrite-bearing arkoses and quartz veins. Studies of petrogeochemistry indicate that the diorite, is with medium to low ∑REE concentrations, enriched in LILE (such as K, Rb, Ba) and more mobile incompatible elements (such as U, Th, Pb), relatively depleting in HFSE (such as Ta, Nb, P, Sr, Ti). The chondrite-normalized REE patterns of the diorite samples display pronounced LREE enrichment and HREE depletion, slightly negative Eu anomalies (average 0.82), and no Ce anomalies (δCe=0.97～1.07). Geochemical characters imply that the Balifang diorite intrusion has the similar geologic characteristic to the island-arc and active continental margin magma. The arkoses has a wide range of ∑REE concentrations, slightly negative Eu anomalies (average 0.76), and no Ce anomalies (δCe=0.91～0.99). The arkoses belongs to the sandstone series in active margin. Fluid inclusions in quartz veins can be classified into aqueous two-phase, CO₂-bearing three-phase and pure CO₂ types. The homogenization temperatures of aqueous two-phase and CO₂-bearing three-phase inclusions range from 107.9 to 247.4 ℃, 269.8 to 332.7 ℃,and the salinities(w(NaCl)) range from 3.05% to 8.55%, 4.41 to 10.29%. The ore-forming fluids are the hydrothermal system with mediumlow temperature and low salinity. Combined with the geological characteristics of ore deposit, petrogeochemistry and ore-forming fluids, it can be concluded that the Balifang gold deposit belongs to the orogenic gold deposit.

Key words: geology, geochemistry, fluid inclusion, ore genesis, Balifang gold deposit, Heilongjiang Province