CHARACTERISTICS OF HYDROLOGIC ANOMALIES ABOVE VENTS, AS RELATED TO PROSPECTING FOR DEEP-WATER DEPOSITS OF POLYMETAL SULFIDES

Abstract

This paper represents the first attempt to model the structure and evolution of hydrologic anomalies associated with active hydrothermal vents on the sea bottom. Measurements of the variation of water temperature and salinity in the vicinity of hydrothermal vents proved the existence of plumes of water in which the temperature and salinity exceeded the background values by, respectively, 0.1 to 0.3°C and 0.01 to 0.02 promilles. The horizontal scales of these plumes (anomalies) were 5 to 10 km and the vertical scales 150 to 200 m. It is shown that it is possible to represent the hydrologic anomaly as consisting of three zones (Fig. 1): zone I, the root of the anomaly; zone II, the vortical cone of the anomaly; and zone III, the plume. The overall effect of the combination of vertical and horizontal rates of development of the anomaly suggests the horizontal dimension of the plume will be 5 to 10 km and that it will most typically occur at heights of 300 to 500 m above the bottom.