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By Andrew G. Hudson

The long-term economics of each of the four principal metals in marine manganese nodules (copper, nickel, cobalt and manganese) was evaluated to determine the anticipated viability of a nodule mining venture based on existing studies of the potential profitability of a nodule project. This included assessments of the lifetimes of land-based reserves, and examination and econometric modelling of the economic variables thought to affect nodule metal prices and demand. These analyses demonstrated that a) land-based reserves of the nodule metals were likely to last well into the future (100 400 years); b) average nodule metal paces were likely to stay a low levels for the foreseeable future; and c) the expected revenue stream from a twenty- ear nodule mining venture was substantially (42%) below that required to attract the necessary investment capital for such a high risk venture.

Jan 1, 1996

By Ulrich Von Stackelber

Deep sea mining of manganese nodules actually will have an environmental impact to the seafloor and to the water column. However, we are far from being able to predict the possible consequences. Therefore, in 1992 environmental studies were conducted with the R/V Sonne in a manganese nodule field of the Peru Basin. The bathymetry of the seafloor was mapped using the hydrosweep system and the distribution and type of sediments were investigated by the parasound system and by collecting surface samples and sediment cores. Deep towing of a side-scan sonar system revealed a Mn encrustation of sediments and a nodule coverage of variable density. Along the tracks of a photo sledge a great variability of bottom fauna and of bioturbation was observed. Bottom-mechanical investigations of surface-near sediments were completed on board. Additionally water samples were collected near the sea floor to determine character and amount of dissolved and suspended particles. Manganese nodules and crusts were collected at 80 locations. In many aspects the nodules differ from those of the Clarion-Clipperton Zone: Big cauliflower-shaped nodules with growth rates up to 160 mm/ Ma may reach a maximum size of 24 cm in diameter, maximum abundance may be 44 kg/m2, the mean size of buried nodules is greater than that of surface nodules. The reason for that difference is due to the relatively high bioproductivity in surface waters and to a Mn redox boundary in the sediment column 10 cm below the seafloor. Histograms of nodules showing the distribution of size and growth type clearly indicate that the growth history is different for basins, slopes and tops of seamounts and ridges. Nodules with diameters >7 cm show mainly diagenetic and to a minor degree hydrogenetic growth. Smaller nodules of the same assemblage are composed mainly of hydrogenetically grown Mn oxide. The optimum diagenetic growth occurs within the sediment immediately above the Mn redox boundary, a level which is not reached by the small nodules.

Jan 1, 1994

By G. B. Carpenter

The United Nations Law of the Sea (LOS) Convention includes provisions (Article 76) for establishing the outer limits of a coastal State's continental shelf and for denoting the seaward extent of sovereign rights over natural resources. Determination of a coastal State's continental margin, according to Article 76, must consider eight factors: 1. The territorial sea baseline 2. The 2,500-meter isobath 3. The foot of the continental slope 4. A line 200 nautical miles seaward of the territorial sea baseline 5. A line seaward of the foot of the continental slope connecting the points where sediment thickness divided by distance to the foot of the slope equals .01 6. A line 60 nautical miles seaward of the foot of the continental slope 7. A line 100 nautical miles seaward of the 2,500-meter isobath 8. A line 350 nautical miles seaward of the territorial sea baseline Figure 1 shows the preliminary limits for each of the Article 76-based definitions for a portion of the U.S. Atlantic continental shelf. The additional areas gained beyond the 200- nautical mile Exclusive Economic Zone (EEZ) are highlighted. The first three factors are baselines from which the distance provisions of Article 76 are measured. Factors 4-8 are distance- from-baseline provisions for establishing the continental shelf limits. Factor 5, also known as the Depth of Sediment Limit or "Irish Formula", was calculated using sediment thickness data from seismic linesand isopach maps. All other factors were determined from digital hydrographic data. The Depth of Sediment Limit is the most advantageous method for the area shown in Figure 1. It is especially useful for introverted coastlines such as the Georgia Embayment and New York Bight areas. The 200-mile line is advantageous for protruding coasts such as those off major capes, e.g., Cape Hatteras. The 2,500-meter isobath plus 100-mile line gains

Jan 1, 1995

By Simon McDonald

The Neptune Group was established in 1999 to apply for exploration permits within New Zealand’s 200nm EEZ. These applications were to investigate and commercialise hydrothermal Seafloor Massive Sulphide (SMS) deposits identified by international researchers and to locate others. SMS are volcanically related seafloor accumulations of copper, lead and zinc with high levels of gold and silver. Neptune has three granted exploration licenses within the New Zealand EEZ and has application in other jurisdictions. Neptune undertook the world’s first commercial drilling exploration work of SMS in December of 2005.

Aug 24, 2006

By C. Wildman

Prospectivity modeling of seafloor massive sulphide (SMS) deposits has been completed over the Kermadec Arc-Colville Ridge area using the GIS based weights of evidence and fuzzy logic modeling techniques. SMS deposits are the current equivalent of ancient onshore volcanogenic massive sulphide (VMS) ore deposits. These high-grade deposits are formed on the seafloor and commonly consist of a black smoker and metal rich sediment mound complex resulting from the discharge of hydrothermal fluids (up to 400°C) from fractures on the seafloor. Metal sulphides are continuously precipitated in response to mixing of high-temperature hydrothermal fluids with ambient seawater. Accumulation of metal sulphides has led to SMS deposits being potentially major sources of copper, zinc, lead and other metals such as gold, silver, which to date remain untapped. Modeling of SMS deposits was undertaken to illustrate the power of GIS modeling for seafloor resource evaluation and how it can be used to quickly identify and rank in terms of the most likely prospective areas of the seafloor where new SMS deposits might exist. The mineral deposit modeling was constrained by the mineral systems concept which defines those parts of a mineralisation system that are critical to the ore-forming process. The deposits are typically formed in extensional tectonic settings, including both submerged tectonic margins and sea-floor spreading. Volcanic vent systems and underlying dykes, stocks and sills are the sources of heat that are responsible for converting sea water drawn down through fractures in the oceanic crust into an ore-forming hydrothermal fluid. This fluid is then capable of leaching metals and elements from surrounding footwall rocks, which are then transported upwards via the convection of hydrothermal fluids. The ore materials are then precipitated within the black smoker field as massive sulphides due to the mixing of high-temperature (250-400°C), metal-rich hydrothermal fluids with cold (about 2°C) oxygen bearing seawater.

Jan 1, 2011

By Mark D. Hannington

Results of the R/V Sonne Cruise (Edison) to the Tabar-Feni Arc from March 11 to April 5, 1994, a joint German-Canadian research cruise aboard the vessel R/V Sonne, undertook detailed mapping of the Tabar-Feni island chain, Papua New Guinea. The Tabar-Feni chain is host to several large porphyry stocks and epithermal gold deposits, including the giant Ladolam gold deposit on the island of Lihir (minimum 19 million oz. Au). The principal objective of the cruise was to map the seafloor in the vicinity of recently active alkaline volcanic islands in the Tabar-Feni chain and to characterize the tectonic setting of large high-level porphyry and epithermal gold deposits in the region. Additional work was carried out on shallow-water hot springs associated with mineralized geothermal systems on the volcanic islands. Complete sets of 1:50,000 scale (20-m contour) maps of the seafloor were produced for each of the four island groups (Feni, Tanga, Lihir, Tabar). The Lihir group was the most active and the most interesting. At least 4 (and probably 6 or 7), previously unknown volcanic cones were discovered within about 10 miles south of Lihir. The volcanoes are clearly very young and appear to have erupted along extensional faults produced by regional plate rotation. This recent volcanic activity appears to reflect recent forearc extension and represents the southward propagation of volcanic activity towards New Ireland. One volcanic cone at 1,490 m water depth is hydrothermally active, with very large areas of diffuse venting (100-200 m across), densely populated by beds of giant clams (probably calyptogena). Other vent-specific fauna are also present, including crabs, snails, sulfide worms, scale worms, limpettes, etc. The clam beds sit on a crust of hydrothermally baked and indurated, sulfidic, hyaloclastite-rich muds. The mineralization consists mainly of fine-grained disseminated pyrite and amorphous Fe-sulfides. A second, much larger cone at a depth of 1,070 m is capped by massive vesicular lavas which are intensely fractured and mineralized. Abundant sulfides and amorphous silica occur in stockwork-like veins which

Jan 1, 1994

By Marlene Olivares Cruz

The particles that make up the deep-sea sediments have two main sources: 1) those that are created in situ from dissolved components and 2) those that are washed into the ocean in solid phases from the continents, atmosphere, space and interior of the Earth. Many particles as they sink through the water column reaches the seabed and are known as pelagic sediments with terrigenous, biogenic, authigenic, and cosmogenic components. Among the minerals found in the terrigenous fraction of pelagic sediments are quartz, clay minerals, feldspar, micas, ferromagnesians, and the biogenic fraction with remains of siliceous organisms, such as, radiolarian and diatoms. The chemical nature of marine sediments is controlled by the contribution of particulate matter derived from various sources with varying compositions for the fixing of elements during deposition and the compositional changes carried out within the sediments during diagenesis. In the last decade there have been several studies on the mineralogical composition of seabed sediments, suspended particulate materials and cores, together with paleontological and geochemical data are used for paleoclimatic and paleoenvironmental reconstructions, analyze changes in sea level, stratigraphic correlations and identify past and

Sep 14, 2011

By Carl H. Hobbs

The needs of the on-going basic maintenance operations and proposed enhancement and hurricane protection projects in the City of Virginia Beach exceed the capability land-slide sources of sand. Through the past several years our studies have concentrated on locating and defining suitable quantities of sand appropriate for use on the area's beaches and assessing some of the consequences of dredging in shallow offshore areas. By providing information concerning the geological setting of sand resources, the local wave climate, and benthic infauna, the overall research project has strengthened the knowledge and understanding of several facets of Virginia's inner continental shelf. We have identified three distinct settings for deposits of beach-quality sand, two of which (filled channels and surficial shoals) are distinguishable in relatively unprocessed sub-bottom profiles and cores. The third, a sand facies within a larger stratum, is discernable only with a suite of cores. Sandbridge Shoal, about 5 km offshore of the resort and residential community of Sandbridge appears to contain a substantial quantity of sand that could be exploited with comparatively few problems. It already is designated as the source of material for use in a shoreline protection protect for a federal facility. Fluvial(?) fill of a late Pleistocene channel lust offshore of the main, commercial, resort area may offer a proximal alternative to existing and proposed resources. Ongoing work to describe the local wave climate and the possible impacts of anthropogenic alterations of the bottom topography on wave transformation and studies of the biological community as it might be affected by dredging will help fill-out our series of studies. Prior to utilization of the resource additional work is needed to provide better definition of the limits and magnitude of the sand bodies. Finally decisions concerning the use of specific resources will have to include physical, biological, economic, technical, and social considerations.

Jan 1, 1996

By Kris van Nijen

IHC Merwede, a Dutch supplier of ships and equipment for dredging and mining activities, and DEME, a Belgian dredging and environmental services group, will enter into a joint venture for deep-sea mining activities. Under their cooperative agreement, IHC Merwede will be responsible for the development and construction of technical solutions, while DEME will be responsible for operations. Together the companies will offer a unique pioneering total solution. The joint venture will be known as OceanflORE.

Jan 1, 2011

By J. R. Woolsey

Research grants of The Marine Minerals Technology Center (MMTC) are directed toward development of the technology 'for exploration, mining, and processing of non-fuel mineral resources within the U.S. Exclusive Economic Zone. FY 1989-90 research grants are as follows: - Seafloor Gamma Measurement Data Collection System. - Free-Fall Seafloor Hard Substrate Corer. - Microtopography of Manganese Crust Deposits. - Cobalt Crust Continuum on Seamounts, EEZ, Hawaii. - Economics of Marine Polymetallic Sulfide Resources. - Graphite Furnace Atomic Absorption Spectrometer. - Depositional Models for Aggregate and Heavy Mineral Exploration. - Sand Resources of Heald and Sabine Banks, Texas. - Sources, Geometries, and Compositions of Heavy Mineral Placers. - Geostatistical Methods for Marine Placer Exploration. - Computer Aided Design for Communication and Strength Umbilicals.

Jan 1, 1989

By B. Prause

Ferromanganese crust samples collected from Central Pacific sea-mount areas became of special interest after surprisingly high nobel metal contents have been analyzed. Hydrogenetic crust growth is controlled by the conditions of the oceanic water column. Thicker encrustations show two crust generations of different age ranges. The mean values of the chemical composition state that the older generation is richer in P, Ca, Ni, Cu, Zn, and Pt and depleted in Fe, Ti, Co, Al, and Si. The differences apparently indicate a distinct change of the geochemical environment. The Pt concentrations vary up to 1800 ppb and do not clearly correlate to one of the other metals. This might indicate a bond of multiple nature. Several mechanisms have been proposed to explain the Pt concentrations in ferromanganese samples. Our models consider seawater and cosmic spherules as responsible Pt sources. In seawater the main species of dissolved Pt probably exist as the doubly negatively charged tetrachloro-complex. A precipitation of Pt in seawater may take place if the chloro-complex is decomposed by reduction of pt2+ to pt0. On the other hand, the Mn02 precipitation is caused by an oxidation of Mn2+ which is supplied from the oxygen-minimum zone. The large activation energy needed for the oxidation of divalent ~n" in solution has been recognised, and the resulting slowness in the formation of Mn(V1)-oxihydrate sug

Jan 1, 1989

By Seung-Kyu Son

Environmental properties of the northeast Equatorial Pacific along 131.5 degrees west, between 5 degrees and 13 degrees north latitude, were investigated in association with changes in water column structures during the summer seasons of 1998 and 1999. Climatic disturbances such as El Nino and La Nina, should have affected this area during the study period. In 1998, a thermocline where temperatures rapidly decrease with depth, was formed at 90~110 m water depth. However, in 1999, a very fluctuating thermocline was observed with latitudes. As a result of changes in the water column structures, biological and chemical environment also showed fluctuation parallel to the changes in other physical parameters. Inorganic nutrient depleting areas, especially for nitrate+nitrite and phosphate, or oligotrophic regions were extended down to approximately 100 m depth, which coincided with the surface mixed layer depth. In the euphotic zone, depth integrated nitrogen (N) and phosphorus (P) values were 34 g-N/m2 (grams of Nitrogen per square meter of sea floor), 7 g-P/m2 in 1998 and 130 g-N/m2, 18 g-P/m2 in 1999, respectively. The results indicated that nitrogen (96 g-N/m2) and phosphorus (11 g-P/m2) are supported by up-welling and down-welling phenomena with convergence and divergence in the study area. Biological parameters in the water columns were largely determined by the physico-chemical environmental parameters. Subsurface chlorophyll maximum layers were coincided with the formation of seasonal thermocline. Copepods were the dominant group of zooplankton community at three sampling stations (N5, N6, N10) terms of abundance, which was the same results of previous surveys for the past 3 years. Among copepod populations, Oncaea sp., Oithona sp. Clausocalanus sp., Acarocalanus sp. and juvenile copepodites were dominant Appendicularians, foraminiferans and radiolarians were also dominant. To investigate diel vertical migration pattern of zooplankton, repeated samplings from the water depth of 0~50m and 50~200m were conducted at KODOS (Korea Deep Ocean Study) area before and after sunrise. Zooplankton abundance was slightly higher after sunrise than before sunrise in the surface layer. Chlorophyll-a concentrations were relatively low as the concentration of sediment increased in most experiments possibly due to a decrease of grazing pressure of microzooplantkon such as ciliates, which is the efficient grazer on small-sized phytoplankton. Because copepod predation on microzooplankton may be prevented by the high concentration of sediment, resulting in lower grazing pressure on small-sized phytoplankton. The results obtained during the baseline study as a part of KODOS project since 1998.

Jan 1, 2001

By Jae-Hyung Park

Since the Industrial Revolution, the land resources have been decreased rapidly as the industrialization. And this phenomenon brings to our mind an interest in deep-sea resource(manganese nodule). Hence, Korea has been participated in the development project of exploiting manganese nodule since 1983. Hwang and cho(1998) studied the economic efficiency evaluation of manganese nodule carrier. But they used the TAMU(Texas A&M University) model, and assumed deadweight and velocity of bulk-carrier. If we use some optimization technique, more economic manganese nodule carrier can be selected and evaluated without limited assumption. In this study, we evaluated the economic efficiency of manganese nodule carrier using genetic algorithms(GAs).

Jan 1, 2003

By P. E. Halbach

On June 26, 1988, the Jade Hydrothermal Field was discovered in the Okinawa Trough by the German RV Sonne. This research cruise has taken place within the scope of a German-Japanese cooperative project. The Okinawa Trough, located between the Ryukyu Island Chain and the east coast of China, is an active backarc-basin formed by extension within the continental lithosphere. The Ryukyu arc consists of a nonvolcanic outer arc, forming the main island chain and representing compressive highs of the Asian continental margin, and an inner arc with present-day volcanism in its northern part (Sibuet et al. 1988). The valleys and ridges of the trough are cut across by transverse faults, giving rise to younger volcanic intrusions. The Jade Hydrothermal Field was detected in a caldera-like structure. It is. located at about 27°15,0'N and 127°04,5'E with a maxi- mum water depth of about 1650 m. Data of heat flow measurements show a high anomaly in the cauldron basin with values ranging from around 100 to 800 mw/m2 (Halbach et al. 1989). The hydrothermal vent area was discovered in the northern part of the inside northeast slope of the cauldron in a water depth between about 1300 and 1500 m. We identified different varieties of hydrothermal

Jan 1, 1989

By Robert G. Ditchburn, Cornel E. J. de Ronde, Bernard J. Barry

The age of mineralization, its mode of formation, the time elapsed to amass an economic deposit, its capacity for sustainable extraction and, ultimately, its grade and tonnage, are key aspects in the economic viability of volcanic massive sulphide (VMS) deposits (Ditchburn et al, 2004). Radiometric dating methods applied at GNS Science have been recently refined with the purpose of efficiently determining the ages of seafloor VMS mineralization along active intraoceanic arcs. These developments include: determining the longevity of seafloor hydrothermal systems, details of individual chimney and massive sulfide mound growth, and insights into deep-seated processes, such as the transfer of elements from magmas to their overlying hydrothermal systems. In our pursuit to better understand seafloor hydrothermal systems along intraoceanic arcs, we have thus far compiled age information for three volcanic centres of the Kermadec arc (South Pacific) and one of the Mariana arc (NW Pacific).

By G. Cherkashov

The geodiversity of seafloor massive sulfides (SMS) deposits at the slow- and ultra-slow spreading ridges is of great variety (Fouquet et al., 2010). Tectonics and magmatism are the two principal factors which control SMS formation and localization. The geological setting of SMS deposits is determined by their position relative to the rift valley and by the types of rocks hosted (Table 1). Depending on the first parameter, SMS deposits could be localized at [ ] the axial volcanic ridge or at the flank of the rift valley. Basalts, deep-seated gabbro, and serpentinized peridotites are distinguished among the hosted rocks. The outcrops of deep-seated rocks are exposed at the flanks of the rift valley. The tectonic mechanism of the lower crust and mantle rocks exhumation process is connected with very large offsets along the detachment faults, resulting in a forming oceanic core complex (OCC) (Smith et al., 2006; MacLeod et al., 2009). The SMS related to OCCs are represented by such ore clusters as Ashadze, Logatchev, Semyenov, and some others (Table 1) and are increasing steadily in number. This fact in combination with widespread OCC formation at the slow-spreading ridges (Escartin et al., 2008) and high grades of metals in SMS related to OCCs has provoked considerable scientific and economic interest in these types of deposits. It could be mentioned in this regard that the first two applications to the International Seabed Authority for prospecting and exploration of sulfides have been submitted for the areas in the spreading centres with wide distribution of the core complexes.

Jan 1, 2011

By Jung-Hoon Kang

Present study was stemmed from the survey associated with deep-sea mining in the KODOS area between Clarion Fracture Zone and Clipperton Fracture Zone located in the North Pacific Ocean. The study area, which is located in the southeastern part of North Pacific gyre, is oligotrophic waters with low nutrients and chl-a concentrations below 1µg/l (MOMAF, 1996). This area is also characterized by divergence at 8°N and convergence at 6°N, which moved northward or southward in the range of a few kilometers with seasonal and climate changes. If the waste materials related to deep-sea mining are intruded into the surface waters continuously, unexpected effects to water column ecosystem are anticipated negatively. In order to assess the impact on the planktonic ecosystem, natural variation need to be distinguished from anthropogenically induced variation in terms of the abundance and species composition of plankton. In this study, mesoscale variation of zooplankton community was reported in relation to the physical conditions in the northeastern Pacific during 1998 and 1999. Temperature and salinity were determined using a CTD from surface to 200m depth in July 3-20, 1998 and in June 22-July 1, 1999. Zooplankton samples were collected from two different depths (0-50m, 50-200m) by vertical towing using an opening-closing net (100cm diameter and 300 µm mesh size). The samplings were carried out at every one degree between 5° and 12°N (1998), between 5° and 11°N (1999) along the meridional lines of 131°30´ W. The net was lowered to the depth of interest from a stationary research vessel and towed upward to collect zooplankton at a speed of 25~30 m per minute. Zooplankton samples were transferred to 1-l sampling bottles and immediately fixed with neutralized formalin into the final concentration of 5%. Considering the characteristics of zooplankton such as diurnal vertical migration, all samplings were done during the nighttime. The volume filtered by the net was calculated from the readings of flow meter (Hydro-Bios Model 438-115). Zooplankton were identified to the genus level and enumerated under a microscope. The abundance of zooplankton at each station was expressed as the numbers/100 m3.

Jan 1, 2003

By G. A. Tret’yakov, V. A. Simonov, I. Yu. Melekestseva, V. V. Zaykov, N. N. Ankusheva

The Kyzyl-Tashtyg massive sulfide polymetallic deposit is situated 120 km north-east of Kyzyl (the capital of Tuva Republic, Russia). It is located in the Ulug-O volcanic zone which is interpreted as the northern segment of the Kaa-Khem rift in Sayano-Tuva marginal sea, one of the Paleoasian Ocean margin (Fig. 1) [Zaykov, 2006]. Since its discovery in 1946 the deposit has been studied by many researchers. Significant information was published by Kuzebny et al. [2001] and Zaykov [2006] who proposed volcanogenic-sedimentary genesis. A single reference in English about Kyzyl-Tashtyg is available [Herrington et al., 1999].

By Boris Broere, Wiebe Boomsma, Pieter Lucieer

"The Blue Nodules project started February 2016 as part of the EU Horizon 2020 subsidy program. Blue Nodules aims at developing a sustainable deep sea mining system for the harvesting of polymetallic nodules from the sea floor. Blue Nodules is closely related to the Blue Mining and Midas projects, both EU subsidized projects. Blue Mining mainly concerned the development of technical capabilities to adequately and cost-effectively discover, assess and transport deep sea mineral deposits up to 6,000 m water depths. The MIDAS project - Managing Impacts of DeepseA reSource exploitation - was a multidisciplinary research programme investigating the environmental impacts of extracting mineral and energy resources from the deep-sea environment.The Blue Nodules project is divided in seven work packages defined to develop mining equipment and process equipment, to assess and integrate environmental, economic and technological aspects and to assess and minimize the environmental impact of mining polymetallic nodules.This abstract will address part of the work performed in the second work package called: ‘Subsea harvesting equipment and control technology’. The main topic addressed will be the development of a propulsion system to manoeuvre the harvesting system. The propulsion system will be developed with full incorporation of economical and compliance requirements and to have a minimal environmental impact.SummaryBased on information gathered in the 70’s during the first studies into polymetallic nodules mining and more recent data and developments, an initial full scale design of the propulsion system is developed. The largest challenge for the propulsion of a deep sea mining vehicle is to drive on the soft sediments associated with these deep sea environments. A short summary of the initial design criteria is given below."

Jan 1, 2017

By A. Ivanova

The continental shelves occupy a vast area of Russia and contain complexes of commercial placer minerals. Of prime importance are Cenozoic placers of valuable minerals including gold, cassiterite, diamonds, chromite, platinoids, and minerals of titanium, zirconium and rare earth elements, biogenic amber and fossil ivory (1). Commercial placer minerals are associated with shelf placer formation zones (SPFZ). These zones are located at junctions of marginal orogens and shelf troughs in morphostructures where upwarping, subsidence, and sign-variable neotectonic movements are not significant. The SPFZs are characterized by ancient buried leveling planes with mantles of waste, series of wave-cut aggradation terraces on land and beneath the sea, and drowned and buried stream valleys. The occurrence of mineral placers in the SPFZs was caused by endogenic mineralization and exogenic placer hosted formation. Concentrations of commercial biogenic minerals are associated with areas of burial of biogenic material (release of resins by plants and theriofauna thanatocoenoses) and with their transition zones. Since the Oligocene, alternations in marine transgression-regression have dominated the shelf areas. This has resulted in the formation of polygenic placers. Climatic conditions are of great importance: warm and humid climate in the Paleogene-Neogene changed to colder climates in the late Pliocene (polar type sedimentation; formation of permafrost strata and sea glaciation). These events are responsible for the regularity in placer formation during the Cenozoic in which the early Cenozoic (Eocene-Oligocene-Miocene) and late Cenozoic (late Pliocene-early Pleistocene and late Pleistocene-Holocene) epochs are prominent.

Jan 1, 2004