Deciphering the Formation Processes of Super-large Gold Deposits in China

Strategic Insights -

Research findings on Geology-Ore Geology have been reported from Hebei GEO University, which investigated the North Sanshandao gold deposit, China's first offshore super-large gold resource. The study aimed to understand the mineralization mechanisms of large-scale gold deposits and decipher the formation processes of super-large and Jiaodong-type gold deposits. Funded by the Ministry of Science and Technology National Key R & D Program of China, Natural Science Foundation of Shandong Province, and other organizations, the research involved petrographic observations, crosscutting relationships, and fluid inclusion studies.

Key Takeaways:

  • The North Sanshandao gold deposit exhibits four distinct mineralization stages, with fluid inclusion (FI) studies revealing four FI types in quartz across these stages: (i) liquid (H2O)-dominated two-phase (type 1), (ii) vapor (H2O)-dominated two-phase (type 2), and (iii) CO2-bearing (liquid and vapor) inclusions (types 3a and 3b).
  • The research found clear evidence of fluid immiscibility, indicative of a low-salinity, medium-temperature NaCl-H2O-CO2 hydrothermal system in stages I-III, contrasting with the simpler NaCl-H2O system in stage IV.
  • Stable isotope analysis reveals a predominantly magmatic fluid source for stages I-III, but a significant influx of meteoric water in stage IV.
  • Pressure estimates for stages I-III range from 54.2-81.0 MPa (avg. 69.3 MPa), corresponding to depths of 5.5-8.3 km.
  • Pyrite noble gas isotopes provide further insights, with He-3/He-4 ratios in auriferous pyrite from stages II and III confirming the mantle-derived fluids contribution to mineralization.
  • The research concluded that combined H-O-He-Ar isotopic data strongly support a unified magmatic origin for the ore-forming fluids across the Jiaodong gold deposits.

Statistics:

  • The North Sanshandao gold deposit has a resource of 562 t Au @ 4.35 g/t.
  • The research involved petrographic observations of 254-375°C and 195-313°C temperatures in stages I and II, respectively.
  • Fluid inclusion (FI) studies reveal a total of four FI types in quartz.
  • The He-3/He-4 ratios in auriferous pyrite from stages II and III range from 1.37 to 1.44 Ra (25-26 % mantle-derived He) and 0.07-1.29 Ra (1-23 % mantle-derived He), respectively.

Sources:

  • Geochemical Evolution of Ore-forming Fluids and Key Controlling Factors In Super-large Gold Deposits: a Case Study of the North Sanshandao Gold Deposit, Jiaodong Peninsula, Eastern China. Ore Geology Reviews, 2025;186.
  • NewsRx. Recent Research from Hebei GEO University Highlight Findings in Ore Geology (Geochemical Evolution of Ore-forming Fluids and Key Controlling Factors In Super-large Gold Deposits: a Case Study of the North Sanshandao Gold Deposit, Jiaodong ...). China Weekly News. November 4, 2025; p 283.