Intraplate volcanic-hydrothermal systems of the Clarion-Clipperton zone, Pacific Ocean

The results of recent studies of specific craterlike structures in sediments of the Clarion-Clipperton zone (CCZ) of the Pacific Ocean are summarized. It was established from the example of a crater located in the bottom area with age of ∼40 Ma that such craters from several hundreds of meters to a few kilometers in diameter and from 15 to 100 m deep are a result of evolution of intraplate volcanic-hydrothermal systems mostly active in the CCZ area beginning from the Middle Miocene. Vertical chimneylike channels from a few centimeters to 0.5 m across in pre-Middle Miocene carbonate sediments in the areas of subvolcanic basaltic stocks with an age of 16–18 Ma and less are the structural elements of these systems. The channels are filled with nontronite clays and Fe-Mn hydroxides, which are the products of discharge of low-temperature hydrotherms. New data have allowed us to reach a conclusion on the origin of thermal convection of volcanichydrothermal systems, which dissolved the host carbonate sediments and formed the craterlike structures at the final stage of evolution.