The main achievements and key theory and methods of deep-seated prospecting in the Jiaodong gold concentration area，Shandong Province

Based on lots of geological exploration results, this paper summarized the main achievements of deep-seated prospecting in the Jiaodong gold concentration area, and reviewed in brief the development process of main gold metallogenic theory and prospecting methods. Up till now, more than 4500 tons of gold reserves have been found in shallow and deep places in the Jiaodong area, with more than 2700 tons found in the depth of 500~2000m below the surface. Among these resources, more than 2900 tons were found from superlarge gold deposits with the reserves of each single deposit ≥100 tons, and more than 3900 tons were detected from structural altered rock. Furthermore, Jiaojia and Sanshandao giant gold deposits of kiloton class have been proved. The progress of the ore-forming theory and prospecting methods has made important contribution to prospecting breakthrough. In the aspect of metallogenic model, the understanding has proceeded from quartz vein type gold deposit under a small structure control through structural altered rock type gold deposit under regional large fault control and then to a step metallogenic model in vertical direction. In the aspect of mineralization genesis, previous understanding included greenstone type, multi-sources and long-term mineralization, magmatic hydrothermal ore formation, mantle-derived mineralization and orogenic gold deposit. Now upwelling-extension theory on mineralization has been established. In the aspect of understanding of mineralization type, by integrating Jiaojia type structural altered rock gold deposit, Linglong type quartz vein gold deposit and other various types of gold deposits, researchers put forward the concept of Jiaodong-type gold deposit, which is a unique gold mineralization type that is different from other known types of gold deposit in the world. In the aspect of prospecting method, conventional methods include such means as geological mapping, IP and IP combined profile, and prospecting by primary and secondary halos, whereas present-day prospecting methods adopt high-precision and large detection depth means, such as 3-D metallogenitic prognosis along the structural belt, high resolution geophysical exploration, tectonogeochemical exploration, constructing exploration model on the basis of a step metallogenic model.