Geochemical Mechanism Of Gold Accumulation In Offshore Of Northern Sanshandao Gold Deposit In The Jiaodong Gold Porvince,Eastern China

Jiaodong peninsula lies at the southeast of North China Craton and is China's largest and the world's third gold province,with a series of world-class large gold deposits,such as the Sanshandao,Jiaojia and Linglong.Jiaodong gold province has aroused great interest of ore deposit scientists and exploration ones both at home and abroad,and is the natural laboratory for the study and geological exploration of gold deposits.In recent years,with the depletion of mineral resources,the gold deposit prospecting at deep and periphery is imminent.The spatial and temporal distribution of different types of gold deposits is systematically summarized.The grade-tonnage model was constructed by the reserve-average grade-ore body occurrence data of 119 gold deposits,to systematically evaluate and predict the metallogenic potential from the regional scale.The Haiyu gold deposit is a typical Jiaojia type gold deposit.The gold orebody mainly occurs in Linglong-type granite and is controlled by Sanshandao-Cangshang fault zone.(Pyrite)Silicitization is the alteration product of the main metallogenic period.Hydrothermal fluid activates the gold in the wallrock by potassium metasomatism and hydrolysis.The study of alteration and fluid inclusion shows that the ore-forming fluid is characterized by medium and low temperature,medium and low salinity,and belongs to the CO2-H2O-NaCl±CH4 system.In hydrothermal fluid,gold may be transported mainly in the form of Au(HS)-complex,which led to Au precipitation and enrichment.The identification of MZ is the theoretical basis and main method for the prediction of deep prospecting exploration.The altered rocks affected by K-metasomatism are characterized by K enrichment and Na and Ca loss.The molar ratio of elements related to K-metasomatism can be used to identify hydrothermal altered minerals and their alteration processes in the Jiajia-type gold deposit.The mass change pattern of gold and pathfinder elements reflects the spatial relationship between gold mineralization and K metasomatism,and is the product of hydrothermal fluid interaction.The maximum concentration of K,gold and pathfinder elements usually occurred at the proximal end of the gold MZ,while most of the loss occurred at the distal end far from the gold MZ.K metasomatism can identify potentially larger areas of alteration,thus effectively indicating the location of the gold MZ.The geochemical indexes of gold MZ at different scales can be established based on the whole rock geochemical data to point to the gold mineralization location.The scale study of the deposit shows that 12 geochemical indexes can be used to distinguish the gold mineralized area from the non-mineralized area in Jiaojia-type gold deposit.Detailed-scale studies have shown that the component drift along the borehole direction can indicate whether there is and/or close to the gold MZ in the depth,and the element with the strongest component drift is often the best indicator of whether it is close to the gold MZ.Weathering effects should be considered in the strong oxidized rocks near the surface.