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By Tetsuo Yamazaki

Deep-sea rare-earth element-rich mud (REE Mud) distributes in pelagic clayey sediment column on ocean seafloor at 4,000-6,000 m deep. The thickness ranges 5-80 m and the burial depth 0-100 m. The REE content ranges 600-2,250 ppm in Pacific and one of the richest, maximum 6,500ppm, has been found in Marcus Is. exclusive economic zone. By applying a conventional hydraulic excavation and lifting methods, the economy of REE Mud mining around Marcus Is. is preliminary examined. Because the waste content in REE Mud is high and the disposal cost in Japan is very expensive, the mining is recognized far away from economy.

Sep 14, 2011

By Mark Lee, Isobel Yeo, Sarah Howarth, Christian Millo, Javier González Sanz, Paul Lusty, Bramley Murton, Pierre Josso

"Seafloor cobalt-rich ferromanganese crusts represent the most important yet least explored resource of ‘E-tech’ elements on the planet (Hein et al. 2003; ISA, 2008; Hein et al. 2010; Hein et al. 2013). These polymetallic deposits form a continuum from nodules rich in manganese and cobalt to crusts rich in tellurium and the heavy rare earth elements (HREE). It is this combination of traditional (base) metals and the extreme enrichment of ‘E-tech’ elements that makes seafloor ferromanganese oxide deposits particularly interesting to both science and society. Recent estimates of the global resource, based on the sparse data available, infers a dry mass of ferromanganese crusts on the seafloor of 35 x 109 tonnes (35GT). Of this, 3.7 GT is predicted in the Indian Ocean, 8 GT in the Atlantic, and 23 GT in the Pacific (Hein et al. 2013).At a global scale, the processes controlling the formation and distribution of ferromanganese (Fe-Mn) crusts are reasonably well understood (e.g. Hein et al. 2000; Verlaan et al. 2004; Cronan 2006; Halbach et al. 1989; Usui and Someya, 1997; Hein et al. 2000; Hein et al. 2003; Hein et al. 2009; Hein et al. 2010; Hein et al. 2013; Muiños et al. 2013; Marino et al., 2016). However, much of this knowledge is drawn from sparse sampling at a regional to ocean basin scale. As a result, there remains a fundamental gap in understanding of the role of local-scale factors, such as micro-topography, ocean currents and upwelling, sedimentation rates, micro-organisms, water mass composition and biological productivity, that are considered potentially crucial to controlling the growth and composition of Fe-Mn crusts. Indeed, quantitative, particularly temporal, information relating to these processes and their relative importance in deposit formation is almost completely absent. Hence, to make any significant advance in understanding these deposits require significant new research."

Jan 1, 2017

By C. L. Mardock

The U. S. Bureau of Mines participated in a two-year joint State of Oregon/Department of Interior Placer Task Force study on the economic and environmental aspects of Oregon's marine placer deposits. The effort culminated in a research cruise off the southwest coast of Oregon to investigate the geological and biological characteristics of the continental shelf deposits. The Bureau's role was to collect and study the placer material off the continental shelf and to determine its strategic potential and significance. In-depth characterization of the sediments by optical and electron microscopy verify that the placer material from Cape Blanco contains up to 3 pct ilmenite, 0.5 pct chromite, and small amounts of zircon and gold. However, harsh sea conditions and equipment failures prevented sampling below a four-foot depth at the Cape Blanco site. Results to date indicate that the deposits sampled off the southwest coast of Oregon do not represent a significant source of strategic minerals. However, further study of the deeper sediments off Cape Blanco may uncover significant concentrations of chromite. This presentation encompasses the site geology, the geophysical and biological activities of the expedition, and the results of the Bureau's mineralogical and chemical investigation. The combined findings of the Bureau and other Task Force agencies have provided information needed to expand the country's limited knowledge of marine mineral resources and has assisted state and federal agencies in the formulation of offshore mineral policies.

Jan 1, 1991

By Yanis Miezitis, Gerald Mueller, Timothy F. McConachy, Ronald G. Sait, Keith R. Porritt, William J. McKay

In November 2004, Australia lodged with the United Nations Commission on the Limits of the Continental Shelf possible new maritime boundaries in relation to Australia’s continental shelf extending beyond 200 nautical miles from the Territorial Sea Baseline (Colwell and Symonds, 2005). If agreed by the commission, just over half of Australia’s land mass will lie below the sea, and Australia will have one of the largest marine jurisdictions in the world (14.41 million km2). With this jurisdiction comes a responsibility to manage and sustain the marine environment (McConachy, 2006). Knowledge of minerals and their resource potential is part of this responsibility but is generally poorly known (McConachy, 2005).

Aug 24, 2006

By Caleen E. Kilby

A program of surveying and studying the surficial sediments of northern Juan de Fuca Strait was undertaken between 1988 and 199 1. Detrital sediments were mapped from the intertidal zone down to 100 m depth along the slopes of a series of shallow coastal marine terraces. The sand heavy mineral content was examined over this region and sediment geochemistry and assays were performed on selected samples both offshore and from beaches along the coast. The coastline of southwestern Vancouver Island has numerous streams, with a history of small Au placer extraction, which empty into the strait to the south. Only very minor evidence of this was seen in values from isolated locales. However, one beach presented a remarkably different mineralogy and geochemistry from the remainder of the coastline. From the beach to 800 meters offshore heavy mineral contents were greatly elevated and Ti values were as high as 1.4% of the sand fraction. Minerals were relatively fresh and angular, with mineral percents distinctly different than those found elsewhere along this coastline. No stream of substantial size crosses this largely sandy-gravel beach. A series of studies identified the source of this small marine placer as having its origins n the tailings from a submarine pipe broken short in the next bay. A Cu-Au mine 1.5 km upstream, closed by the mid 1970's, had processed its ore underground and piped the crushed tailings to the submarine discharge pipe. The crushed material has been transported and concentrated with the longshore current and been sorted by strong coastal swells. Ilmenite/titanomagnetite from the homblendized basalt of the mine is the source of the Ti enrichment.

Jan 1, 1994

By C. W. Devey, K. S. Lackschewitz

The mineralogy and geochemistry of hydrothermally altered wall rocks from different modern basaltic- and felsic-hosted hydrothermal fields at seafloor spreading centers and convergent margins have been studied to determine the characteristics of different types of alteration and to calculate the magnitudes of elemental exchanges between seawater and wall rock.

Aug 24, 2006