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Abstract
Lockheed Martin has conducted an analysis of the rare earth content of Clarion-Clipperton Zone (mid-Pacific) manganese nodules using samples from its archive from the 1970s/1980s. The rare earth content of these manganese nodules is economically significant, and essentially uniform over large areas. Additionally, manganese nodules have low thorium and uranium content relative to land based rare earth ores, and therefore may provide an inherently environmentally cleaner and economical source for rare earths.

Introduction
From 1978 to 1981, Lockheed Martin collected thousands of manganese nodule samples from the seabed of the Clarion-Clipperton Zone of the Pacific Ocean. This was done as part of a $500M (in 2010 adjusted dollars) effort in manganese nodule mining. Due to the increasing technological importance and economic value of a wide range of rare earths, in early 2011 samples from 79 locations across Lockheed Martin’s original US licensed claims were submitted to a commercial laboratory and assayed for rare earth content. The following sections describe the results and economic implications of this study.

Background
In the 1970s/80s, Lockheed Martin led a consortium of companies in an effort to develop a commercial mining operation for deep seabed manganese nodules. Manganese nodules form on the seafloor at water depths between 4 km to 5 km (USBoM, 1985). The most commercially attractive manganese nodules are those in the Clarion-Clipperton Zone (CCZ) in the Pacific Ocean which lies between Hawaii and Mexico (USBoM, 1985). In the 1970s/1980s, the interest in CCZ nodules was due to their content in Ni (1.4%), Cu (1.3%) and Co (0.25%). Today, Mn (30%) and rare earth elements (0.08%) add to their potential commercial value.

The Lockheed Martin consortium spent over $150M (approximately $500M in 2010 dollars) to extensively survey its claims in the CCZ, and to develop manganese nodule mining and metallurgical processing technology. Under Lockheed Martin’s US exploration licenses (Figure 1), a detailed survey of the claims was completed, with thousands of separate samples of nodules retrieved from the seabed. The nodule retrieval techniques included both free fall grab and box coring. In addition to these surveys, Lockheed Martin designed, developed and tested a pilot-scale seabed mining system in the CCZ (Figure 2). The system included a seabed nodule collector and crusher system, a seabed-to-surface nodule slurry riser system, a dynamically positioned surface ship, and a metallurgical processing plant specific to seabed nodules. Over eighty patents related to this effort were generated, including many related to deep sea power and remote control technologies and techniques. The Lockheed Martin consortium employed the M/V Glomar Explorer, which was the first vessel to employ dynamic positioning and riser pipe heave compensation on an industrial scale. The Lockheed Martin mining effort was scaled back in the mid-1980s as a result of uncertainty over international mining regulations and deflated commodity prices.

Manganese Nodule Sample Collection and Analysis
Figure 3 shows the 79 locations of the samples from the Lockheed Martin archive used in this study. The samples were chosen due to the relatively high (> 15 kg/m^2) estimated abundance of manganese nodules in their locality. Blind replicates for six of the samples were included for a total of 85 analyzed samples.