Changes in the Composition of Upper Pleistocene Sediments in the Center of an Active Hydrothermal System (Middle Valley, Juan De Fuca Ridge, Pacific Ocean)

The article presents the results of studying changes in the chemical composition of Upper Pleistocene sediments from Hole ODP 1036A drilled in the Middle Valley of the Juan de Fuca oceanic ridge at the Dead Dog hydrothermal field to a depth of 38.50 m, 9 m from a black smoker with a temperature of 268°C. The most significant changes in sediment chemistry occurred in the lower intervals of the hole. In the 20–30.70 m interval, the concentration of a large number of chemical elements increased and, accordingly, the hydrothermal fluid was depleted of these elements. Conversely, in the 30.70–38.5 m interval, the concentration of most chemical elements decreased, which led to significant enrichment of hydrothermal fluid in these elements.