Role of Taylor―Hogg Topographic Eddies in the Formation of Cobalt-Manganese Crusts on Guyots of the Magellan Seamounts, Pacific Ocean

摘要

Cobalt-manganese crusts (CMC) of the Magellan Seamounts were studied by VNIIOkeanologiya (1986―1988) and PGO Dal'morgeologiya (1988―1996) as the major claim of Russia in the International Region of the Seafloor, endowed with Co, Mn, and other metal resources. The IOAN (MZh―35), Roskomnedra (MZh―36), and other guyots were investigated with a high reliability due to the successive principle of the geological surveying, from regional geological and geophysical works at a scale of 1 : 1 000 000 to prospecting works at a scale of 1 : 50 000. The difference between the guyots in dimensions, planar orientation, morphology of the abrasion-flattened surfaces, and depths is seen in Fig. 1. These structures formed in the Cretaceous and reached the current depth in the Oli-gocene. Ore bodies related to the guyots exhibit a certain regularity in their location and structure. The cobalt-manganese crusts are confined to their edges to form narrow (ribbonlike) bands. They are thickest (10―12 cm) at the edges but pinch out to a few millimeters toward the center of the guyot and downward the slope and disappear at a depth of 3500 m. Central segments of the guyot plateaus are covered with planktonogenic carbonate sediments with ripple marks whose dimensions and orientation are evidence of bottom currents with velocities of 5-10 cm/s.