Dec 16 2013nbsp018332The recovery of such deposits and of other mineral deposits known to lie at some depth below the ocean floor and at considerable distances from the nearest land will be difficult Where the distance is too great to warrant driving long tunnels from shore based shafts it may be necessary to adapt techniques for offshore petroleum recovery.
The Hawaiian and Johnston Island Exclusive Economic Zone seabed areas host significant deep sea mineral deposits called ferromanganese crusts These deposits are enriched in manganese cobalt and other metals of commercial interest including rare earths Rare earths make possible the high tech world that we live in today allowing for everything from miniaturization of electronics to green energy even medical technologies and essential telecommunications With increasing demand for high tech devices global commercial exploration of deep sea minerals is accelerating.
In many deepwater areas around the world these crust deposits form as iron Fe and manganese Mn minerals precipitate out of seawater to form a layer or crust on rocky surfaces see Figure 1 above They are commonly found on virtually any type of deep sea rocky surfaces where bare rocks are exposed to seawater for long periods of time They only occur on sediment free surfaces Crusts may be found on the rock seabed anywhere deeper than a few hundred meters They are most common on the flanks and summits of seamounts that rise hundreds of meters above the ocean floor.
While there are many unknowns about the viability of commercially mining these deposits the key variable will probably be the thickness of the crust Metal concentration is also important but the technical difficulties related to removing thin deposits from irregular rocky surfaces suggests that the most viable deposits economically will be those with the greatest thickness on the smoothest surfaces.
Dr James Hein of the U S Geological Survey has studied deep sea crust deposits extensively for more than 35 years collecting examining and testing samples recovered from many sites Dr Hein has concluded that the deposits with the most potential for economic recovery i e deposits with relatively high content of cobalt and relatively thick crust layers are found on seamount flanks and summits in water depths between 800 and 2 500 meters Hein Conrad and Dunham 2009.
Geologists surmise the thickest and most metal rich ferromanganese crusts are found at depths between 800 and 2 500 meters on seamount flanks and summits This is due to the co occurrence of more chemically available metal sources caused by the Oxygen Minimum Zone higher flows of water over the rocks where the deposits form and stronger currents that can remove sediments Image courtesy of the NOAA Office of Ocean Exploration and Research 2015 Hohonu Moana Download larger version jpg 420 KB.
This depth range usually corresponds to the level in the ocean known as the Oxygen Minimum Zone OMZ which lies below depths where significant sunlight can penetrate and permit photosynthesis to take place and below depths affected by wind driven currents and turbulence that can mix oxygen rich surface water with deeper water In water with relatively low levels of oxygen the metals that precipitate to form the crusts become more chemically active than at higher oxygen levels and thus more available to form the deposits.
The apparent preference for growth on seamounts may also be related to the fact that seamounts are obstacles to deep sea current circulation Currents encountering a seamount are diverted around and above the edifice leading to increased current levels at the seafloor seawater interface This increase will increase the flow rate of water at the seafloor surface and can also act to dislodge loose sediments that might otherwise cover the rocky surfaces.
Thus as illustrated in Figure 2 the co occurrence of more chemically available metal sources due to the presence of the OMZ relatively higher flows of water over the rocks where the deposits form and stronger currents that can remove sediments may explain the occurrence of the thickest and most metal rich crusts within this depth range and on seamounts.
Commercial interest is currently focused on three types of marine mineral deposits Polymetallic nodules occur throughout the ocean and are found lying on the sea floor in the abyssal plains.
Deep ocean mineral deposits as a source of critical metals for high and green technology applications comparison with land based deposits Ore Geology Reviews 51 1.
Describe how these deposits are distributed throughout geologic time Archean to Cenozoic and in space e g mid ocean ridge continental arc back arc basin Develop a conceptual Source Transport Trap STT model for understanding the genesis of mineral deposits on Earth and their relationship to plate tectonics in time and space.
Aug 17 2020nbsp018332Companies are eager to mine the deep ocean for valuable mineral deposits But scientists are concerned about impacts on sea life including creatures that.
The Marine Minerals Program MMP has worked with 18 states on cooperative agreements through which hundreds of millions of cubic yards of OCS sediment has been identified for use in beach nourishment and coastal restoration projects For example Federal state and local government agencies have constructed projects in Florida Louisiana Maryland New Jersey and Virginia using sediment evaluated through the cooperative program including several done on an emergency basis.
The ocean floor is one of the least explored places in the world Rich with abundant marine life and mineral deposits the deep seabed has attracted the interest of a newly forming deep sea mining industry which could threaten fragile marine ecosystems In this episode we rebroadcast an event at Pew featuring Michael Lodge secretary general.
The study compiled coastal project data from many different sources BOEM recognizes there is incomplete information for some specific timeframes and locations and uncertainty when projecting the demand for sediment to address erosion following future storms The report reached three major conclusions more states will turn to OCS sediment resources as in state resources become scarce the volumes requested will be larger to support increasing coastal resilience measures and there is a critical need for BOEM to continue identifying additional OCS sand resources.
Potential follow on studies would attempt to close many of these data gaps to refine the forecast and improve its usefulness to coastal managers.
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Metals occur in all kinds of rocks but usually in concentrations that are too low to be mined Metallic ore deposits however are relatively rare concentrations of metalbearing minerals usually sulfides that contain enough metal to be profitably mined Again the profit line is dependent on a number of economic factors Our most important metals are iron copper aluminum lead zinc silver gold chromium nickel cobalt manganese molybdenum tungsten vanadium tin mercury magnesium platinum and titanium.
Mineral exploration is the practice of exploring for and discovering new ore deposits Exploration is becoming progressively more challenging as the ore deposits exposed at the surface are discovered and mined Future exploration will focus on developing techniques that will help find ore deposits that are hundreds or thousands of feet below the surface and impossible to detect at the surface.
Feb 25 2016nbsp018332Active hydrothermal deposits of this type were investigated in 2000 during Ocean Drilling Program ODP Leg 193 in the Manus Basin 7 and in 2010 during Integrated Ocean.
VMS deposits are formed from the water discharged at high temperature 250176 to 300176C at ocean floor hydrothermal vents primarily in areas of subduction zone volcanism The environment is comparable to that of modern day black smokers Figure 20 5 which form where hot metal and sulphide rich water issues from the sea floor.
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Form mineral deposits and dispersed in the ocean and gases hydrogen hydrogen sulphides methane carbon dioxide that are used as an energy source for 1 Nodules crusts and vents Marine minerals.
Feb 27 2017nbsp018332These are also abundant in deep ocean mineral deposits Minerals Within Reach Deep below the oceans surface precious minerals have spent millions of years building up on rocks and soft.
Jun 25 2018nbsp018332These minerals solidify as they cool forming chimney like structures Black smokers are chimneys formed from deposits of iron sulfide which is black White smokers are chimneys formed from deposits of barium calcium and silicon which are white.
Hydrothermal mineral deposits are formed when minerals are deposited and concentrated from hot hydrothermal waters that are superheated by molten magma and ascend to spring at the earths surface The sulphide metal minerals that hotsprings deposit are generally concentrated in the cracks and faults along which the fluids rise to the surface.
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