NANOSCALE METALS IN EARTHGAS AND MOBILE FORMS OF METALS IN OVERBURDENIN WIDE-SPACED REGIONAL EXPLORATION FOR GIANT DEPOSITS IN OVERBURDEN TERRAINS

This paper describes the use of NAnoscale Metals in EarthGas (NAMEG) a nd MObile forms of MEtals in Overburden (MOMEO) methods in regional sc ale geochemical exploration for giant deposits in terrains covered by overburden. These methods are based on the premise that gases generate d from the earth's interior can not only transport mobile forms of ele ments from an ore deposit and its geochemical halos to the surface to form a local anomaly, but also transport them from distinct bedrock '' geochemical blocks'' hosting large and giant ore deposits and give ris e to large regional geochemical anomalies and geochemical provinces at the surface. Regional NAMEG and MOMEO surveys for giant gold deposits were carried out in Shandong Province, where the largest gold deposit s in China are found, and in the Muruntau region of the Kyzylkum Deser t, Uzbekistan, one of the world's largest gold ore provinces. In Shand ong Province, where most of the area is covered by complex overburden, large regional anomalies in earthgas and water-extractable Au were de lineated over and around the giant gold deposits. For many trace eleme nts, the anomalies are larger in area and have greater contrast than t hose from other methods. High concentration of water soluble Au extend s into the southern area covered by transported overburden, suggesting that this region may have potential for the discovery of new conceale d gold deposits. The anomalous provinces of Au in both earthgas and wa ter soluble salts coincide with a deep fault, supporting the idea that the deep fault is the main conduit of Au from the interior. In the ce ntral Kyzylkum Desert, nearly all Au-hosting rocks are covered by sedi mentary sequences overlain by desert sand. Gold and As anomalies over Muruntau and Kokpatas gold deposits have contrasts ranging from 2 to 4 00 times background. Strong anomalies were also discovered in the sout h of the Muruntau region, suggesting a promising area for the discover y of new giant gold deposits.