Ore Assays of Massive Sulfides From Three Spreading Centers

Abstract

ABSTRACT Ocean Minerals Company (OMCO), a deep seabed mining consortium has, through its general contractor, Lockheed Advanced Marine Systems, analyzed massive marine sulfide samples from three sites on the Juan de Fuca Ridge, one site on the East Pacific Rise (near 2PN), and one site on the Galapagos Rift, for the concentrations of Ca, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd and Pb. The samples were collected with dredges and submersibles, and were generously provided to OMCO by government and academic investigators. It is possible that marine sulfides may be a future commercial source of Cu, Ag, Zn and other metals and those studies of these young, relatively unaltered deposits will also provide useful guidelines for the location of unexplored and commercially viable land deposits of marine origin. OMCO has supported this comparative study of the major and minor element composition of sulfides from these three medium-rate spreading centers to obtain a preliminary estimate of ore grade variability and to identify likely sites for future exploration. From the samples analyzed to date, it appears that there are significant differences among the sulfide compositions characteristic of each spreading center. The samples from the Juan de Fuca Ridge are all Zn-rich (maximum concentration greater than 50%) with significant concentrations of Ag (6–12.5 Tr. oz/metric ton). The 21°N East Pacific Rise samples are either Zn-rich or Cu-rich, but have lower Ag concentrations than the Juan de Fuca Ridge samples. Samples from the Galapagos Rift are Cu-rich and Fe-rich. Silver concentrations in these samples appear to be inversely correlated with water depth. Though the high metal values obtained are encouraging and clearly justify the continued support of the several U.S. projects which are presently investigating such deposits worldwide, much additional information is needed to justify serious commercial interest. The distinct compositional differences noted between spreading centers may well be regional in character, and may imply basic differences in the source rock, the development of the hydrothermal fluid, or the deposition process. INTRODUCTION Sixteen samples of marine massive sulfide deposits were recently provided to Ocean Minerals Company (OMCO) by academic and U.S. Government researchers for preliminary ore assay analysis. These samples have been subsampled and analyzed by Lockheed for Ca, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd and Pb using atomic absorption techniques. The samples were collected from very young hydrothermal deposits at five sites; three on the Juan de Fuca Ridge (the Endeavor segment, the Axial seamount, and the southern Juan de Fuca Ridge), one from the East Pacific Rise at 21°N and one from the Galapagos Rift at 86°W. The samples were collected by both dredges and manned submersibles. The purpose of this paper is to report the results of these preliminary analyses. Since identical methods were used in the analysis of all samples, the data set provides a good means of comparison of deposits from different locations.