Abstract: Streltsov (Str) ore field is a large deposit cluster composed of super-large and large Mo-U deposits, and has been the only source of natural uranium in Russia for a long time after the disintegration of the Soviet Union. Its discovery and exploration in Str ore field is long, tortuous, and legendary. The uranium prospecting began in the region of South Erguna, and stopped completely at the beginning of 1962, as no valuable results had been found. In the autumn of 1962, L P Ishukova, a senior geologist, wrote to the leader suggesting a continue prospecting work in this area, and got the chance to try again. The first super-sized U deposit was discovered by her drilling layout in Str ore field, and caused the big turn of the whole situation. Since then, accelerating the ore field development had become the general principle of all work. The parallel acceleration of exploration and geological research for deposits promoted mutually, and most of the deposits in this ore field were discovered within the following 10 years. By the end of 1966, the preliminary prospecting results of Str and other deposits had become a sufficient basis for the establishment of the largest uranium mine in the Soviet Union in the early 1970s. By the end of 1980s,17 Mo-U deposits had been completely explored. From a technical perspective,the success of Str ore field exploitation has two main reasons:one is that people have had a deep understanding to these deposits and their control conditions in the ore field; the other is that the work methodology adopted has been improved constantly, as almost every deposit in this ore field is a deep-buried blind ore. The new round prospecting strategy was that by the comprehensive use of geology, radioactivity, traditional geophysics, geochemistry, deep survey automatic perforation device, and drilling exploration, three dimensional geological tectonic mapping of different scales was completed. On the basis of these results, drilling was used to discover deposits. The basic fact facing exploration work is that the complexity of deposit composition is the common feature of all the deposits in Str ore field, and each deposit has its own characteristics, which makes every exploration process of these deposits quite different. Drilling was used in early exploration, and the basic mesh ranged from 200 m×100 m to 400m×100 m. In detailed exploration, the combination of underground engineering and drilling was used, and the exploration system combined with horizontal and vertical cross sections was adopted with the basic mesh from 50 m×20 m to 50 m×25 m. The total exploration results of all deposits were fully confirmed thereafter by mining engineering, and the reserves was also increased by 10 percent. The basic experience and lessons of the successful exploration in this field are worthy to learn. The "Str effect" has spread rapidly in China for geological exploration work. It is expected to continue to ferment in China, especially in Hulun Buir, and even in the Mesozoic tectonic-magmatic belt of the Dahingan-Yanshan Mountains with more and greater achievements.

Key words: Russia, Streltsov ore field, super-sized urnium deposit, uranium deposit discovery and exploration, “Streltsov effect”, Hulun Buir area