Composition of Co-rich ferromanganese crusts and substrate rocks from the Marshall Islands, cruise KODOS 97-4

Abstract

This report is preliminary and has not been reviewed for conformity with the U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Three northwest Pacific seamounts were studied in the Marshall Islands Exclusive Economic Zone (EEZ) during the KODOS 97-4 cruise, which took place from 23 August to 6 September, 1997 aboard the R.V. Onnuri (Figs. 1-4). Cruise KODOS 97-4 (Table 1) marked a renewed effort to study seamount mineral deposits that had started with three USGS-KORDI cooperative cruises aboard the R.V. Farnella, one each in the years 1989-1991. The primary objectives of the KODOS 97-4 cruise were to (1) map the distribution of thick Fe-Mn crusts on Lomilik Seamount and determine the geologic and oceanographic conditions that promoted growth of thick crusts (Fig. 3). Reconnaissance sampling and mapping on Lomilik Seamount were completed in 1989 during the first cooperative USGS-KORDI cruise aboard the R.V. Farnella (Hein, Kang, et al., 1990). During that cruise, the thickest (180 mm) shallow-water crust ever recovered from the ocean basins was collected from the summit of Lomilik Seamount; and (2) reconnaissance sampling and mapping of two volcanic edifices that had not previously been studied, Lemkein Seamount and Litakpooki Ridge (Figs. 2,4). Representative ferromanganese oxyhydroxide crusts (Fe-Mn crusts) and substrate rocks from the dredge hauls taken on those three edifices were analyzed for this study, which extends our previous work on Fe-Mn crusts collected in and around the Marshall Islands (