1.1 What are metalliferous sediments?
Metalliferous sediments are unconsolidated deep-sea deposits that form in volcanically active areas of the ocean floor (Gurvich, 2006). These deposits are variable proportions of hydrothermal, detrital, hydrogenous, and biogenous material (Dymond et al., 1977). More simply defined, these are sediments with higher transition metal content than normal. These sediments are specifically enriched in iron, manganese and a number of other trace elements, while depleted in aluminum and titanium. This abiogenic matter is primarily produced and contributed to the ocean by means of hydrothermal vents, which emit sulfur and metal-bearing material into the ocean from Earth’s interior. Hydrothermal plumes of particle-laden fluid interact intimately with the surrounding seawater, where metal-rich marine precipitates then fall out of suspension and settle down to the ocean floor. Bonatti (1978) states that the essential feature of a metalliferous sediment is a hydrothermal Fe-Mn deposit that forms near active plate boundaries and hot spots.
2. Background
2.1 Discovery of metalliferous sediments
Although the first deep-sea metalliferous sample was recovered during the H.M.S. Challenger voyage of the southeastern Pacific, Murray and Renard (1891) did not recognize the anomalous nature of the sediment. Instead, credit for the discovery of the metallic nature of this sediment lies with Boström and Peterson (1966), as results from their experiment displayed a marked enrichment of Fe, Mn, Cu, Cr, Pb and Ni in sediments from the East Pacific Rise. Metal-rich sediments have since been recovered from a number of from a number of sites, most prominently on the East Pacific Rise and Mid-Atlantic Ridge, in the Bau...
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The Kimmeridge Clay Formation is the penultimate formation of the onshore British Jurrasic Succession. William Smith was the first to document this distinct formation on his map of 1815, and to name as the Oaktree Soil. In 1817, he gave the name Oaktree Clay for the layers of clay between the “Portland Rock” and “Coral Rag and Pisolite” but in 1816 Webster was the first to describe in details the formation and changed to the name now known as kimmeridge Clay Formation after the English village of Kimmeridge on Dorset’s “Jurassic Coast” a place frequently visited by fossil hunters. (Cox and Gallois, 1981).
The central belt of the Franciscan Complex represents older and more metamorphosed units of rock best characterized as a melange. Blocks of graywacke, greenstone, chert, limestone, and blueschists are sheared and thrust upon one another in a choatic mix (Isozaki and Blake, 1994). In contrast to the coastal belt, metamorphism is higher in grade here and dominated by pumpellyite which formed within the matrix of graywacke (Hagstrum and Murchey, 1993). The mixing of these units makes a stratigraphic subdivision difficult but analysis of the graywacke slabs indicates that the depositional environment was also deep sea, near to the continent. Turbidity currents in this environment deposited much of the sediment in both the coastal and central belts.
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Magmas in island arc settings consist primarily of components from two different origins, the slab component, and the mantle wedge. The mantle wedge may melt due the descent of the slab, giving the main portion of the non-slab component. The slab component is derived from the subducting slab as it descends. This may consist of melting of the crustal portion of the slab, but also melting of the mantle wedge due to addition of water driven off the slab. Since the descending slab is composed of old, cold oceanic crust, there is a slight paradox in the idea of melts forming from it. However, frictional heat, as well as the heat of the underlying mantle, can drive hydrous fluids off the slab. (Machado, Chemale Jr., Conceição, Kawashita, Morata, and Van Schmus, 2003; Kimura and Yoshida, 2006).The addition of water to the mantle wedge results in the lowering of melting temperatures, allowing melts to be formed at much lower temperatures than might otherwise be expected. Also, the circulation of hot fluids allows materials dissolved in them to migrate upwards ...
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Minerals play an important role in our day-to-day life but we often not contemplate how the minerals are obtained. Minerals are scattered all over the world just like any other resources. Due to the natural processes of magma flow, hydrothermal gradients, sedimentation, and evaporation, Minerals are concentrated in various areas of the Earth’s crust. Obtaining these minerals for human use involves four general steps:
Review: The opportunity and endeavor of exploring the Earth’s oceans can reap great rewards for mankind and unravel many of the mysteries that the Earth has left to discover.