High dispersive minerals of the metalliferous sediments from the axial zone of ultra-fast spreading center in the South part of the East Pacific Rise (20°30´-22°00´S) were studied by XRD methods. It is established that the high dispersive part of the studied sediments is almost totally composed of X-ray amorphous Fe and Mn oxihydroxides. Among the crystalline phases of greater importance is the Fe-montmorillonite with different degree of crystallinity. Going away from the rise axis illite of terrigenous origin appears. It is established that during the pulsed hydrothermal processes the degree of Fe-montmorillonite crystallinity changes. The Fe-montmorillonite formed during the low temperature phases of the hydrothermal stages is better crystallized than that one formed during the high temperature phases. The processes of crystallization are most probably controlled by the physicochemical parameters of the venting from the oceanic crust hydrothermal fluids.