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Chemical and morphological characterization of polymetallic (Mn-Fe) nodules from the Clarion-Clipperton Zone in the Pacific Ocean

Kozłowska-Roman Agata, Mikulski Stanisław

Geological Quarterly

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2021

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Vol. 65, No. 4

art. no. 57

EN

Geochemical studies (WD-XRF, ICP-MS, and GF-AAS) have shown that polymetallic nodules from the eastern Clarion-Clipperton Zone (CCZ) in the Pacific Ocean are enriched in several metals such as Cu (mean 1.16%), Ni (1.15%), Co (0.15%), and Zn (0.14%), as well as remarkable contents of Mo (0.059%), V (0.04%), Ce (0.019%), Nd (0.011%), Li (0.015), and Pt (43 ppb). The average content of REE, together with Y and Sc, is 620 ppm. In nodules from the CCZ metal concentrations are often much higher than those reported in nodules from other ocean basins in the world. The bulk-nodule mean value of the Mn/Fe ratio is 5.3, which is characteristic for a mixed (hydrogenetic and diagenetic) origin of the nodules. Microprobe investigation revealed two different chemical compositions of the layers, and ascertained their general metal content. The nodules analyzed are composed mainly of concentric-collomorphic laminae of Mn and Fe (oxy)hydroxides which crystallized around mineral nuclei (e.g., quartz, clay minerals), bioclasts or rock fragments. They are from 3.3 to 7.6 cm in diameter. The chemical and physical properties of the laminae allowed distinction of two genetic types: hydrogenetic and diagenetic. Those formed as a result of hydrogenesis had increased values of Co, Si, Cl and S, while formed diagenetically showed increased levels of Cu, Ni, Mg, Zn and K. These lamina types are characterized by different growth structures, reflectivity, density and Mn/Fe ratios. The ratio of the diagenetic layers to hydrogenetic layers (192/53) in representative polymetallic nodules shows that the nodules of this study are of mixed hydrogenetic-diagenetic type. A mixed genesis was also shown by discriminant diagrams, with these CCZ samples being located at the transition between typical hydrogenetic and diagenetic fields.

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Osady eupelagiczne jako potencjalne źródło pozyskiwania pierwiastków ziem rzadkich

Zawadzki D., Maciąg Ł., Kotliński R. A.

Biuletyn Państwowego Instytutu Geologicznego

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2015

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nr 465

131--141

PL

W artykule przedstawiono rezultaty badań nad przydatnością wybranych osadów eupelagicznych (mułów ilastych krzemionkowych) i hydrogenicznych (konkrecji polimetalicznych, naskorupień kobaltonośnych) do pozyskiwania pierwiastków ziem rzadkich (REE). Wykorzystano wyniki analiz geochemicznych 137 próbek mułów ilastych krzemionkowych, pochodzących z poligonu IOM H11 (Interoceanmetal Joint Organization), znajdującego się we wschodniej części Strefy Rozłamowej Clarion-Clipperton (CCFZ) na Pacyfiku. Otrzymane wyniki porównano z dostępnymi danymi literaturowymi odnoszącymi się do zawartości REE w tlenkowych skupieniach żelazowo-manganowych oraz w osadach eupelagicznych z innych perspektywicznych obszarów oceanicznych. Przeprowadzone analizy geochemiczne wykazały, że suma koncentracji pierwiastków ziem rzadkich i itru (ΣREY) w osadach badanego poligonu wynosi od 199,99 do 616,56 ppm, przy średniej 288,81 ppm. Badania porównawcze średnich zawartości REE w konkrecjach polimetalicznych i naskorupieniach kobaltonośnych wskazują, że największe ilości REY zawierają naskorupienia kobaltonośne Oceanu Indyjskiego (ΣREY = 2541 ppm) oraz północnego Pacyfiku (ΣREY = 2487 ppm). Konkrecje polimetaliczne odznaczają się umiarkowanymi zawartościami pierwiastków ziem rzadkich, przy czym rozpoznane zależności zmian ich koncentracji są związane z typami genetycznymi konkrecji.

EN

The study deals with the potential and suitability of selected eupelagic sediments (siliceous-clayey silts) and hydrogenic marine ferromanganese oxides (polymetallic nodules and cobalt-rich manganese crust) as a possible resource of rare earth elements (REE). A total of 137 surface sediment samples from the Interoceanmetal Joint Organization (IOM) H11 Fe-Mn nodule deposit, eastern part of the Clarion-Clipperton nodule field (located the Clarion-Clipperton Fracture Zone – CCFZ; tropical Pacific), were collected using a box corer during a research cruise of the R/V Yuzhmorgeologiya. The chemical composition of samples was analysed after 4-acid digestion by inductively coupled plasma mass spectrometry (ICP-MS) and compared with available literature data of REE concentration in marine ferromanganese oxides and eupelagic sediments from the prospective ocean areas.The geochemical analysis shows the total rare earth elements and yttrium (ΣREY) contents in the investigated samples range from 199.99 ppm to 616.56 ppm with an average of 288.81 ppm. Comparative study of average REY concentration in polymetallic nodules and cobalt-rich manganese crust from selected areas of the global ocean reveals the highest content of REY in cobalt-rich manganese crust of the Indian Ocean, Pacific Crust Zone (PCZ – the area of seamounts in the central and western equatorial Pacific, from the equator area to 20°N latitude) and Northern Pacific (non – PCZ). Polymetallic nodules are characterized by intermediate concentration of REY, and the variations of composition depend on genetic types of nodules.

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Abyssal epibenthic megafauna of the Clarion-Clipperton area (NE Pacific): Changes in time and space versus anthropogenic environmental disturbance

Radziejewska T., Stoyanova S.

Oceanological Studies

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2000

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Vol. 29, No. 2

83-101

EN

Abyssal epibenthic megafauna was used as one of biological indicators of the effects of anthropo-genic sediment disturbance in the Benthic Impact Experiment (BIE) carried out within 1994-1997 by the Interoceanmetal Joint Organization (IOM) in the Clarion-Clipperton Fracture Zone (NE Pacific). Analysis of bottom photographs collected from 14 phototransects measuring about 2-10 km in length, made during three cruises, yielded data on the composition and abundance of the epi-benthic megafauna in nodule-bearing (N) and nodule-free (NF) areas of the bottom. The latter included a site at which experimental sediment disturbance, mimicking that produced by nodule mining, was induced. Megafauna was studied before (October 1994, July 1995) and immediately after the disturbance (July 1995), a follow-up survey being performed in April 1997, i.e., 22 months after the original disturbance. Characteristic differences in megafaunal composition and abundance between the two habitat types (N vs. NF) were recorded, the N bottom megafauna being consistently more abundant and dominated by sessile invertebrates (mainly sponges), while the NF megafauna showed a preponderance of mobile deposit feeders (holothurians). The megafaunal abundance in both habitat types showed differing patterns of temporal changes: while the abundance in the NF areas declined sharply immediately after the disturbance and markedly increased 22 months later, the N megafauna abundance was observed to increase from one survey to the next. Due to the fact that the sediment sampled in April 1997 showed evidence of a substantial phytodetritus input, the increase in the megafaunal abundance, recorded in both habitat types at that time, is assumed to reflect mainly the increase in the benthic food supply, superimposed in the NF transect sections on natural processes of recolonisation, proceeding in the disturbed areas of the bottom.