Supraore Haloes of Buried Submarine Placers: Formation Conditions and Implications for Prospecting

The structure and formation conditions of secondary geochemical haloes above the buried and flooded placers and their submarine sources in the nearshore shelf zone are considered with a special emphasis on the geochemical processes in placers. It is shown that these processes are most contrasting during periodical emergence and submergence of the shelf. They are of crucial importance in the prospecting for buried mineralization. Submarine tin placers on the Eterikan Strait shelf in the northern framework of Bol'shoi Lyakhovskii Island (New Siberian Islands) were investigated. It was established that ore placers buried below the sealevel are accompanied by contrasting supraore anomalies that penetrate the entire overlying sedimentary sequence and reach the seafloor. The most contrasting anomalies of ore element assemblages are typical of the modern active layer of bottom sediments. It plays the role of an efficient complex geochemical barrier that can accumulate the geochemical information on underlying sediments. Facts demonstrating the efficiency of prospecting works within contours of these anomalies and discovery of buried submarine placers are presented.