RESEARCH ON THE CLASSIFICATION AND METALLOGENIC BACKGROUND OF GOLD DEPOSITS IN DUOBAOSHAN-HUMA AREA, HEILONGJIANG PROVINCE

Dozens of gold deposits have been discovered in Duobaoshan-Huma area in the northwestern part of Heilongjiang Province, which are distributed mainly in a rhombic area composed of NE-trending and NW-trending structures. The Proterozoic and Lower Paleozoic stratigraphic units may be the provenance of gold. Three stages of tectonomagmatic thermal events since Paleozoic have provided the heat, fluid and space for metallogenesis. Based on the characteristics of host rocks, ore-forming fluids and regional tectonic evolution of the deposits, it is suggested that the gold deposits in this area divide into three genetic types, i.e. 1) volcanic rock-related epithermal type, hosted by Early Cretaceous volcanic rock, with ore-forming fluid from meteoric water; 2) epithermal type gold deposits controlled by compressional structure, without choice for host rock, with mixed ore-forming fluid from meteoric water and metamorphic fluid, low salinity and less CO₂; and 3) skarn-type and porphyry-type of associated gold deposits, with high mineralization temperature, high salinity and CO₂-rich fluid inclusions. The former two types were formed in the same period but located in different tectonic level, in the geological environment of post orogenic extension. The third type of gold deposits were formed in compressive orogenic environment related to the subduction of paleo-Pacific plate and the closure of Mongol-Okhotsk ocean in Late Triassic-Middle Jurassic period.