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1.
Layers from one manganese nodule dredged from the Philippine Sea(16°56'N, 129°48'E; water depth, 5700 m) and 45 bulk nodules from offshore Minami-Torishima Island, Japan(23°3'N, 153°22'E; water depth, 1200 m) were analyzed chemically and their origin is discussed based on geochemical constraints. In general, Cu, Ni, Zn and Mo tend to increase with increasing Mn content, while Co, Pb, Ba, V, Sc, Th, and the rare earth elements(REEs) show less variation with increasing Mn content. Nodule 42 H from the Philippine Sea has an average Mn/Fe ratio close to 1 and shows a positive Ce anomaly, suggesting a predominant hydrogenous origin. Profiles of 230Th230 ex and Thex/232 Th ratios in the outer ~0.3 mm of nodule 42 H indicate a steady growth rate of ~1.7 mm/Myr. Nodule E30 from offshore Minami-Torishima is characterized by lower Mn, Fe, Mn/Fe(0.53) and Mo/V(0.2) ratios but higher P and Cu/Ni(0.31) ratio relative to other nodules from that area. The Ce content of E30 is unusually low(82 ppm) when compared with other nodules from the area and it is the only nodule analyzed with a negative Ce anomaly(-0.64). Based on the geochemical data we suggest that most nodules from offshore Minami-Torishima are primarily of hydrogenous origin except E30, which is dominated by hydrothermal input, and E45, which has about a 35% hydrothermal contribution. 相似文献
2.
Processes of authigenic manganese ore formation in sediments of the northern equatorial Pacific are considered on the basis
of study of the surface layer (<2 mm) of ferromanganese nodule and four micronodule size fractions from the associated surface
sediment (0–7 cm). Inhomogeneity of the nodule composition is shown. The Mn/Fe ratio is maximal in samples taken from the
lateral sectors of nodule at the water-sediment interface. Compositional differences of nodules are related to the preferential
accumulation of microelements in iron oxyhydroxides (P, Sr, Pb, U, Bi, Th, Y, and REE), manganese hydroxides (Co, Ni, Cu,
Zn, Cd, Mo, Tl, W), and lithogenous component trapped during nodule growth (Ga, Rb, Ba, and Cs). The Ce accumulation in the
REE composition is maximal in the upper and lower parts of the nodule characterized by the minimal Mn/Fe values. The compositional
comparison of manganese micronodules and surface layers of the nodule demonstrated that the micronodule material was subjected
to a more intense reworking during the diagenesis of sediments. The micronodules are characterized by higher Mn/Fe and P/Fe
ratios but lower Ni/Cu and Co/Ni ratios. The micronodules and nodules do not differ in terms of contents of Ce and Th that
are least mobile elements during the diagenesis of elements. Differences in the chemical composition of micronodules and nodules
are related not only to the additional input of Mn in the process of diagenesis, but also to the transformation of iron oxyhydroxides
after the removal of Mn from the close association with Fe formed in the suspended matter at the stage of sedimentation. 相似文献
3.
A. Bollhöfer A. Eisenhauer N. Frank D. Pech A. Mangini 《International Journal of Earth Sciences》1996,85(3):577-585
Thorium- and uranium isotopes were measured in a diagenetic manganese nodule from the Peru basin applying alpha- and thermal
ionization mass spectrometry (TIMS). Alpha-counting of 62 samples was carried out with a depth resolution of 0.4 mm to gain
a high-resolution230Thexcess profile. In addition, 17 samples were measured with TIMS to obtain precise isotope concentrations and isotope ratios. We
got values of 0.06–0.59 ppb (230Th), 0.43–1.40 ppm (232Th), 0.09–0.49 ppb (234U) and 1.66–8.24 ppm (238U). The uranium activity ratio in the uppermost samples (1–6 mm) and in two further sections in the nodule at 12.5±1.0 mm
and 27.3–33.5 mm comes close to the present ocean water value of 1.144±0.004. In two other sections of the nodule, this ratio
is significantly higher, probably reflecting incorporation of diagenetic uranium. The upper 25 mm section of the Mn nodule
shows a relatively smooth exponential decrease in the230Thexcess concentration (TIMS). The slope of the best fit yields a growth rate of 110 mm/Ma up to 24.5 mm depth. The section from 25
to 30.3 mm depth shows constant230Thexcess concentrations probably due to growth rates even faster than those in the top section of the nodule. From 33 to 50 mm depth,
the growth rate is approximately 60 mm/Ma. Two layers in the nodule with distinct laminations (11–15 and 28–33 mm depth) probably
formed during the transition from isotopic stage 8 to 7 and in stage 5e, respectively. The Mn/Fe ratio shows higher values
during interglacials 5 and 7, and lower ones during glacials 4 and 6. A comparison of our data with data from adjacent sediment
cores suggests (a) a variable supply of hydrothermal Mn to sediments and Mn nodules of the Peru basin or (b) suboxic conditions
at the water sediment interface during periods with lower Mn/Fe ratios. 相似文献
4.
Manganese nodules and manganese carbonate concretions occur in the upper 10–15 cm of the Recent sediments of Loch Fyne, Argyllshire in water depths of 180–200 m. The nodules are spherical, a few mm to 3 cm in diameter, and consist of a black, Mn-rich core and a thin, red, Fe-rich rim. The carbonate occurs as irregular concretions, 0.5–8 cm in size, and as a cement in irregular nodule and shell fragment aggregates. It partially replaces some nodule material and clastic silicate inclusions, but does not affect aragonitic and calcitic shell fragments.The nodules are approximately 75% pure oxides and contain 30% Mn and 4% Fe. In the cores, the principal mineral phase is todorokite, with a Mn/Fe ratio of 17. The rim consists of X-ray amorphous Fe and Mn oxides with a Mn/Fe ratio of 0.66. The cores are enriched, relative to Al, in K, Ba, Co, Mo, Ni and Sr while the rims contain more P, Ti, As, Pb, Y and Zn.The manganese carbonate has the composition (Mn47.7 Ca45.1 Mg7.2) CO3. Apart from Cu, all minor elements are excluded from significant substitution in the carbonate lattice.Manganese nodules and carbonates form diagenetically within the Recent sediments of Loch Fyne. This accounts for the high Mn/Fe ratios in the oxide phases and the abundance of manganese carbonate concretions. Mn concentrations in the interstitial waters of sediment cores are high (ca. 10 ppm) as also, by inference, are the dissolved carbonate concentrations. 相似文献
5.
A. V. Dubinin T. Yu. Uspenskaya M. N. Rimskaya-Korsakova T. P. Demidova 《Lithology and Mineral Resources》2017,52(2):81-101
The Sr isotope stratigraphy of the biogenic apatite was used to determine the age of pelagic sediments in the Brazil Basin (Station 1541) that contain ferromanganese micronodules, nodules, and coatings on the weathered volcanic rocks. The age of sediments at horizons 0–5 and 86–90 cm was estimated at 24.1 ± 0.2 Ma and 24.8 ± 0.2 Ma, respectively. The average sedimentation rate in the Late Oligocene was about 13 mm/ka. The hydrogenous Fe–Mn nodule on the sediment surface with the Mn/Fe value of 1.05–1.95 was formed at a rate of 1.2–2.4 mm/Ma, which is 1000 times lower than the growth rate of buried nodule (Mn/Fe 0.4) at depth of 83 cm. Diagenesis provoked changes in the mineral composition of the buried nodule (asbolane-buserite partially replaced by goethite), leading to the loss of a part of Mn, Ni, Li, and Tl but accumulation of trace elements linked with iron oxyhydroxides (Ce, Th, Be, As, and V) were retained. The composition of manganese micronodules at two studied depths in sediments evolved in the course of two stages of ore formation: related to the oxic and suboxic diagenesis. The Sr isotopic composition in manganese micronodules from both horizons do not differ from that of dissolved Sr in the ocean water. The 143Nd/144Nd ratio, which reflects the Nd isotopic composition in the paleocean during the micronodule formation, varies in manganese micronodules from different horizons and is constant in different size fractions. 相似文献
6.
锰结核生长与沉积环境的关系 总被引：2，自引：0，他引：2
本文收集了48组世界大洋各种沉积环境锰结核化学组成和生长速率数据并计算了它们的铁锰通量；讨论了不同环境的锰结核的铁锰含量之间的关系，以及锰通量与铁通量、Mn/Fe比的相关性；导出了由锰结核锰铁含量计算生长速率的经验关系；从本质上揭示了锰结核化学组成、生长速率与沉积环境的内在联系，为探讨锰结核形成机理提供了有力的依据。 相似文献
7.
Deep-sea ferromanganese deposits contain a wide range of economically important metals. Ferromanganese crusts and nodules represent an important future resource, since they not only contain base metals such as Mn, Ni, Co, Cu and Zn, but are also enriched in critical or rare high-technology elements such as Li, Mo, Nb, W, the rare earth elements and yttrium (REY). These metals could be extracted from nodules and crusts as a by-product to the base metal production. However, there are no proper separation techniques available that selectively extract certain metals out of the carrier phases. By sequential leaching, we demonstrated that, except for Li, which is present in an easily soluble form, all other high-tech metals enriched in ferromanganese nodules and crusts are largely associated with the Fe-oxyhydroxide phases and only to subordinate extents with Mn-oxide phases. Based on this fact, we conducted selective leaching experiments with the Fe-specific organic ligand desferrioxamine-B, a naturally occurring and ubiquitous siderophore. We showed by leaching of ferromanganese nodules and crusts with desferrioxamine-B that a significant and selective extraction of high-tech metals such as Li, Mo, Zr, Hf and Ta is possible, while other elements like Fe and the base metals Mn, Ni, Cu, Co and Zn are not extracted to large extents. The set of selectively extracted elements can be extended to Nb and W if Mn and carbonate phases are stripped from the bulk nodule or crust prior to the siderophore leach by e.g. a sequential leaching technique. This combination of sequential leaches with a siderophore leach enhanced the extraction to 30–50% of each Mo, Nb, W and Ta from a mixed type Clarion-Clipperton Zone (CCZ) nodule and 40–80% from a diagenetic Peru Basin nodule, whilst only 5–10% Fe and even less Mn are extracted from the nodules. Li is extracted to about 60% from the CCZ nodule and a maximum of 80% Li is extracted from the Peru Basin nodule.Our pilot work on selective extraction of high-tech metals from marine ferromanganese nodules and crusts showed that specific metal-binding organic ligands may have promising potential in future processing technologies of these oxide deposits. 相似文献
8.
Fe-nodules occur within saprolites formed from weathering of granodioritic gneisses in the rain-shadow region of the Mysore Plateau adjacent to the Sahyadri Mountains in Southern India. These nodules and their host saprolites were studied for their geochemistry, including chemical speciation, to understand nodule formation and chemical redistribution processes during rock weathering. From their mode of occurrence, and mineralogical and geochemical data, we infer that the nodules originated by a two-stage process in which the initial extensive weathering of gneisses likely facilitated subsequent ferrolysis weathering and nodule formation. Nodules originated by precipitation of goethite, hematite and gibbsite along with several amorphous phases within the matrix of weathered gneisses. This is possible only under hydromorphic conditions, suggesting that parts of the plateau must have gone through a humid phase prior to the present aridity. In the saprolites, Al, Fe, and Ti become enriched because of the removal of Si, Ca, Na, and K. However within the nodule, Fe, Ti, Cr, and Ni are deposited after their chemical transport from the saprolite. Titanium, known for its immobile nature, was also mobilized and concentrated under the conditions of nodule formation. The most important elements in the nodule constitution are Fe, Al, Ti, and Mn, each having both crystalline and amorphous phases. Fe-Ti and Mn oxyhydroxides grain coatings in the saprolites and discrete amorphous Mn and Ti phases in the nodules seem to have scavenged trace elements from the weathering profile. REE were mobilized during weathering and nodule genesis in which Ce and Ti show a strong geochemical coherence. The enrichment of only HREE in saprolite, and both HREE and LREE with significant Ce in the nodule, indicate the control of evolving secondary minerals in the REE redistribution during rock weathering. Strong enrichment of Ce in the weathering profile and in nodules has important implications to the REE chemistry of river waters. 相似文献
9.
Ferromanganese nodules of the Baltic Sea: Composition,helium isotopes,and growth rate 总被引：1，自引：0，他引：1
Results of the study of shallow-water ferromanganese nodules in the Gulf of Finland of the Baltic Sea, which are of practical interest for metallurgical and chemical industries, are discussed. The nodules contain the following elements: Mn, Fe, Si, Al, Na, Mg, Ti, K, V, Cu, Ni, Zn, P, and Ba. Contents of Mn (～30%) and Fe (～10%) are virtually similar to those in deep-sea oceanic nodules. However, concentrations of Ti, Cu, and Ni are notably lower than average values in oceanic nodules. The helium isotopic composition was studied to reveal cosmic dust in the nodule substance. The measured 3He and 4He concentrations are ～10?12 and ～10?5 cm3/g, respectively. The isotope ratio 3He/4He is approximately 10?7. More than 60% 3He is of cosmic (solar) origin, whereas 4He is of terrigenous (radiogenic) origin. Based on the cosmic duct concentration and the space tracer method, the FMN growth rate is estimated at 8–9 mm/ka at the nodule age varying from ～800 to 1500 yr. The growth rate of nodule has negative correlation with its size. Based on literature data, the growth rate of FMN from the western Baltic Sea is twice as high. An independent calculation of the FMN growth rate based on the diffusion-sorption mechanism (DSM) yielded 8.1 mm/ka, which is very close to the result based on the space tracer method. This value is proposed as the average growth rate of the studied nodules. Comparison with our previous measurements of growth rates for oceanic nodules showed that these values differ only slightly and are equal to n mm/ka, where n < 10. It is inferred that the formation mechanism of both marine and oceanic nodules is based on the same principles that control the generation of mobile forms of Mn in the bottom layer of sediments, i.e., principles related to bioproductivity of sea and ocean basins. Fluxes of lithogenic forms of Mn are of minor importance. 相似文献
10.
Nodules of various compositions, including ferromanganese nodules, have been found in bottom sediments of an artificial reservoir
in the central Altai Territory. The nodules were formed in the alkaline environment against the background of a high carbonate
content and saturation with oxygen. The rate of nodule growth is no less than 1.7–1.8 mm/yr and the pH value of water varies
from 8.0 to 9.7. Fe and Mn contents in soil and loam of the drainage area are lower than the global clarke value, whereas
Ca, K, and Na contents are much higher. The main mass of bottom sediments in the reservoir is markedly enriched in Cd, Mg,
Mn, Sr, Ni, Cr, Sb, V, and Pb, but they are depleted in Cu, Mo, Zn, and Li, relative to the soil and loam. Elements in ferromanganese
nodules are arranged in the following way in terms of the decreasing concentration coefficient: Mn (27) > Ba (13.4) > Co (10.7)
> Mo (9.2) > Cd (5.35) > Ni (3.88) > V (3.52) > Cu (3.3) > Fe (3.2) > Sb (2.17) > Sr (2.04) > Pb (1.5) > Zn (1.43) > Cr (1.1)
> Li (0.78) > Mg (0.75) > Na (0.69) > K (0.67) > Ca (0.51). The microelemental composition of nodules in the reservoir qualitatively
fits the composition of ferromanganese nodules in seas and oceans. However, the contents of major ore elements (Ni, Cu, Co,
Zn, Pb, Mo, and V) in ferromanganese nodules from the World Ocean are much higher than in nodules from the examined reservoir. 相似文献
11.
Fourteen ferromanganese nodule–sediment pairs from different sedimentary environments such as siliceous ooze (11), calcareous ooze (two) and red clay (one) from Central Indian Ocean Basin (CIOB) were analysed for major, trace and rare earth elements (REE) to understand the possible elemental relationship between them. Nodules from siliceous and calcareous ooze are diagenetic to early diagenetic whereas, nodule from red clay is of hydrogenetic origin. Si, Al and Ba are enriched in the sediments compared to associated nodules; K and Na are almost in the similar range in nodule–sediment pairs and Mn, Fe, Ti, Mg, P, Ni, Cu, Mo, Zn, Co, Pb, Sr, V, Y, Li and REEs are all enriched in nodules compared to associated sediments (siliceous and calcareous). Major portion of Si, Al and K in both nodules and sediments appear to be of terrigenous nature. The elements which are highly enriched in the nodules compared to associated sediments from both siliceous and calcareous ooze are Mo – (307, 273), Ni – (71, 125), Mn – (64, 87), Cu – (43, 80), Co – (23, 75), Pb – (15, 24), Zn – (9, 11) and V – (8, 19) respectively. These high enrichment ratios of elements could be due to effective diagenetic supply of metals from the underlying sediment to the nodule. Enrichment ratios of transition metals and REEs in the nodule to sediment are higher in CIOB compared to Pacific and Atlantic Ocean. Nodule from red clay, exhibit very small enrichment ratio of four with Mn and Ce while, Al, Fe, Ti, Ca, Na, K, Mg, P, Zn, Co, V, Y and REE are all enriched in red clay compared to associated nodule. This is probably due to presence of abundant smectite, fish teeth, micronodules and phillipsite in the red clay. The strong positive correlation (r ? 0.8) of Mn with Ni, Cu, Zn and Mo and a convex pattern of shale-normalized REE pattern with positive Ce-anomaly of siliceous ooze could be due to presence of abundant manganese micronodules. None of the major trace and REE exhibits any type of inter-elemental relationship between nodule and sediment pairs. Therefore, it may not be appropriate to correlate elemental behaviour between these pairs. 相似文献
12.
13.
Mitchell Lyle 《Geochimica et cosmochimica acta》1982,46(11):2301-2306
Using available information on the accretion rates and the bulk chemical compositions of oceanic ferromanganese nodules, it can be shown that the accumulation rate of manganese is proportional to the square of the accumulation rate of iron. This relationship has been used to derive an equation that predicts nodule growth rates from their chemical compositions. The equation accurately predicts growth rates up to about 50 mm/106 yr, but yields incorrect rates for faster-growing concretions. From this relationship nodules underneath water of high primary productivity grow most rapidly and accumulate transition metals most rapidly; however, nodules from regions of highest primary productivity do not have the highest concentrations of nickel and copper. Reduction of manganese within the sediment column and remobilization of a fraction to the surface sediments adds manganese to nodules without substantially augmenting the supply of other transition elements. The addition of remobilized manganese to the nodule dilutes the concentrations of nickel, copper and iron, even though their rates of accumulation are also high. 相似文献
14.
15.
Manganese at equilibrium in seawater occurs dominantly as Mn2+ and inorganic complexes at a concentration ratio of about 1:0.72; solubility decreases exponentially with increasing pH or Eh. However, the nodule oxides birnessite and todorokite are at least four orders of magnitude undersaturated relative to the Mn concentrations of seawater, and are metastable relative to hausmannite and manganite. This apparent lack of equilibrium is explicable by the mechanism of precipitation.Surfaces assist Mn precipitation by catalyzing equilibration between dissolved and reactive O2 and simultaneously also by adsorbing ionic Mn species. The effective Eh at the surface becomes 200–400 mV above that of seawater; the oxidation rate of Mn increases about 108 ×, and the activation energies for Mn oxidation decrease ~ 11.5 kcal/mole. Consequently, marine Mn nodules and crusts form by adsorption and catalytic oxidation of Mn2+ and ferrous ions at nucleating surfaces such as sea-floor silicates, oxyhydroxides, carbonates, phosphates and biogenic debris. The resulting ferromanganese surfaces autocatalyze further growth. In addition, Mn-fixing bacteria may also significantly accelerate accretion rates on these surfaces.Mn which accumulates in submarine sediments may be diagenetically recycled in response to steep solubility gradients causing upward migration from more acidic and reducing horizons toward the sea floor. In contrast, the concentrations of the predominant ferric complexes, Fe(OH)30 and Fe(OH)4?, are relatively less sensitive to the Eh's and pH's found in this environment; Fe is therefore not as readily recycled within buried sediments. Consequently, Fe is not so effectively enriched on the sea floor, although it precipitates more readily than Mn because seawater is saturated in amorphous Fe(OH)3.The metastable, perhaps kinetically-related, Mn oxides of nodules have a characteristic distribution: birnessite predominates in oxidizing environments of low sedimentation rate and todorokite where sedimentation rates and diagenetic Mn mobility are higher. Surface adsorption and cation substitution within the disordered birnessite-todorokite structure account for the high trace element content of Mn nodules. 相似文献
16.
Some garnet peridotite nodules from The Thumb, a minette neck on the Colorado Plateau in the southwestern United States, contain
zoned minerals. Zoning does not exceed 1.5 wt.% for any oxide, but some relative changes are large: in one garnet TiO2 and Cr2O3 ranges are 0.05–0.65 and 3.5–5.0 wt.%, respectively. In two porphyroclastic nodules, garnet rims are depleted in Mg and enriched
in Fe, Ti, and Na compared to cores, and one garnet is irregularly zoned in Ti and Cr. Olivine crystals in these rocks are
unzoned, and pyroxene zoning is slight, yet matrix olivine and pyroxene contain more Fe and Ti and less Mg and Cr than inclusions
of these phases in garnet. In three coarse nodules, garnet rims are Ti-rich compared to cores, and Ca, Fe, Mg, and Cr zoning
patterns are complex. Several nodules appear to have partially equilibrated near 1200° C and 35 kb, and under these conditions
cation mobility in pyroxene was greater than in garnet.
The zoning partly reflects Fe and Ti metasomatism in the mantle. Calculations indicate that Fe-Mg gradients in garnet could
have persisted for only a short time in the mantle, perhaps thousands of years or less, so the metasomatism occurred shortly
before eruption. The minette host, a likely source of the Fe and Ti, is rich in light rare earth elements: since the nodules
are much poorer in these elements, little or no infiltrated minette was trapped in them. Diffusion is a possible mechanism
for nodule metasomatism. Some fertile peridotite nodules from kimberlites may have been affected by similar events. Compositional
differences between inclusions in garnet and matrix phases are intriguingly similar to some of the differences between most
peridotite inclusions in diamonds and common lherzolite phases. 相似文献
17.
Ferromanganese (Fe–Mn) crusts are strongly enriched relative to the Earth's lithosphere in many rare and critical metals, including Co, Te, Mo, Bi, Pt, W, Zr, Nb, Y, and rare-earth elements (REEs). Fe–Mn nodules are strongly enriched in Ni, Cu, Co, Mo, Zr, Li, Y, and REEs. Compared to Fe–Mn crusts, nodules are more enriched in Ni, Cu, and Li, with subequal amounts of Mo and crusts are more enriched in the other metals. The metal ions and complexes in seawater are sorbed onto the two major host phases, FeO(OH) with a positively charged surface and MnO2 with a negatively charged surface. Metals are also derived from diagenetically modified sediment pore fluids and incorporated into most nodules. Seafloor massive sulfides (SMS), especially those in arc and back-arc settings, can also be enriched in rare metals and metalloids, such as Cd, Ga, Ge, In, As, Sb, and Se. Metal grades for the elements of economic interest in SMS (Cu, Zn, Au, Ag) are much greater than those in land-based volcanogenic massive sulfides. However, their tonnage throughout the global ocean is poorly known and grade/tonnage comparisons with land-based deposits would be premature.The Clarion–Clipperton Fe–Mn Nodule Zone (CCZ) in the NE Pacific and the prime Fe–Mn crust zone (PCZ) in the central Pacific are the areas of greatest economic interest for nodules and crusts and grades and tonnages for those areas are moderately well known. We compare the grades and tonnages of nodules and crusts in those two areas with the global terrestrial reserves and resources. Nodules in the CCZ have more Tl (6000 times), Mn, Te, Ni, Co, and Y than the entire global terrestrial reserve base for those metals. The CCZ nodules also contain significant amounts of Cu, Mo, W, Li, Nb, and rare earth oxides (REO) compared to the global land-based reserves. Fe–Mn crusts in the PCZ have significantly more Tl (1700 times), Te (10 times more), Co, and Y than the entire terrestrial reserve base. Other metals of significance in the PCZ crusts relative to the total global land-based reserves are Bi, REO, Nb, and W. CCZ nodules and PCZ crusts are also compared with the two largest existing land-based REE mines, Bayan Obo in China and Mountain Pass in the USA. The land-based deposits are higher grade but lower tonnage deposits. Notably, both land-based deposits have < 1% heavy REEs (HREEs), whereas the CCZ has 26% HREEs and the PCZ, 18% HREEs; the HREEs have a much greater economic value. Radioactive Th concentrations are appreciably higher in the land-based deposits than in either type of marine deposit. A discussion of the differences between terrestrial and marine impacts and mine characteristics is also presented, including the potential for rare metals and REEs in marine deposits to be recovered as byproducts of mining the main metals of economic interest in nodules and crusts. 相似文献
18.
《Geochimica et cosmochimica acta》1986,50(10):2235-2243
The solid Mn content of sediments at a site in the Panama Basin (5°21′N 81°56′W) decreases from 3.9% in the interfacial sediment to 1% at 1.5 cm and <0.2% below 5 cm. These conditions provide an opportunity to examine the influence of Mn oxides on the metal adsorption characteristics of natural marine sediments.The adsorption of 14 metals on interfacial sediment and sediment from depths of 0.5 to 3 cm and 15 to 19 cm from the Panama Basin site was studied, and distribution coefficients (KD) were determined. A comparison of the KD values for a variety of samples containing different Mn contents (i.e., Panama Basin sediments, MANOP site H interfacial sediment, red clay, and buserite) indicates that an increase in the solid Mn content enhances the ability of the particles to bind certain metals (e.g., Zn, Pb, Co, Cd, and Ba) while the binding ability for other metals (e.g., Cs, Be, Sc, Pu, Sn, and Fe) is not significantly affected. For the Panama Basin sediment, the KD values for Ni, Co, Cd, Ba, and Mn for the Mn enriched interfacial sediment are 5 to 23 times greater than the KD values for the Mn depleted deep sediment. The KD values for Cs, Be, Sc, Pu, and Fe for the two types of sediment are essentially the same. The correlation between the Mn content and the binding ability of the sediment for particular metals coincides with the Mn-metal correlations observed in bulk compositional data for ferromanganese nodules and sediments. This implies that the observed metal enrichments in nodules or hemipelagic sediments are most likely caused by preferential adsorption of the metals by Mn enriched phases. 相似文献
19.
《Applied Geochemistry》2004,19(6):973-979
The association of rare earth and other trace elements with Fe and Mn oxides was studied in Fe-Mn-nodules from a lateritic soil from Serra do Navio (Northern Brazil). Two improved methods of selective dissolution by hydroxylamine hydrochloride and acidified hydrogen peroxide along with a classical Na–citrate–bicarbonate–dithionite method were used. The two former reagents were used to dissolve Mn oxides without significant dissolution of Fe oxides, and the latter reagent was used to dissolve both Mn and Fe oxides. Soil nodules and matrix were separated by hand. Inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry after fusion with lithium metaborate, and X-ray diffraction were used to determine the elemental and mineralogical composition of the nodules and soil matrix. The latter was composed of kaolinite, gibbsite, goethite, hematite, and quartz. In the nodules, lithiophorite LiAl2(MnIV2MnIII)O6(OH)6 was detected in addition to the above-mentioned minerals. The presence of hollandite (BaMn8O16) and/or coronadite (PbMn8O16) in the nodules is also possible. In comparison to the matrix, the nodules were enriched in Mn, Fe, K, and P, and relatively poor in Si, Al, and Ti. The nodules were also enriched in all trace elements determined. Phosphorus, As and Cr were associated mainly with Fe oxides; Cu, Ni, and V were associated with both Fe and Mn oxides; and Ba, Co, and Pb were associated mainly with Mn oxides. Distribution of rare earth elements indicated a strong positive Ce-anomaly in the nodules, compared to the absence of any anomaly in the matrix. Some of Ce was associated with Mn oxides. The improved methods achieved almost complete release of Mn from the sample without decreasing the selectivity of dissolution, i.e., without dissolving significant amounts of Fe oxides and other minerals, and provided reliable information on associations of trace elements with Mn oxides. These methods are thus proposed to be included in sequential extraction schemes for fractionation of trace elements in soils and sediments. 相似文献
20.
《Geochimica et cosmochimica acta》1999,63(11-12):1709-1722
Particulate samples (>0.45 μm) from a neutrally buoyant hydrothermal plume at 9°45′N on the northern East Pacific Rise were collected using large volume in situ filtration and analyzed for Fe, Al, Mn, Ni, and fourteen rare earth elements (REE). The Sm/Fe ratio (a proxy for overall REE/Fe) and Nd/Er (light/heavy REE fractionation) increased moderately with decreasing particulate Fe. Chemically, the sense of these relationships matched that documented previously in the TAG plume on the Mid-Atlantic Ridge (German et al., 1990), although particulate Fe was about 10 fold lower at 9°45′N. Spatial trends relative to the vent source, however, were opposite of expectation because slow Fe(II) oxidation and Fe(III) colloid aggregation over this interval led to increased particulate Fe (10–26 nM) with distance from source (Field and Sherrell, submitted). After subtraction of non-plume background particle composition, plume particles at 9°45′N and TAG had indistinguishable ranges of light REE-enriched fractionation relative to ambient seawater and had very similar Sm/Fe (therefore Kd for Fe oxyhydroxides), demonstrating that plume particles in both oceans reflect to a first degree the local seawater REE composition. Within-plume REE variations at 9°45′N were investigated using a simple mixing model which accounts for the bulk Fe-Al-Mn variations in the plume using two endmembers: fresh hydrothermal oxyhydroxide precipitates and ridge-crest background particles (composed largely of locally resuspended sediment). Sm/Fe and Nd/Er plot linearly with mixing ratio (R > 0.96), implying that the observed REE trends result from mixing of these two endmembers. Extrapolation to the composition of pure hydrothermal precipitates suggests that Nd/Er is fractionated relative to seawater by a factor of 1.8 during adsorption onto fresh Fe oxyhydroxide particles. The ridge-crest background particles are 5 fold higher in Sm/Fe and Nd/Er is 2.49 relative to seawater, partly a result of enriched terrigenous component in the resuspended matter. A reinterpretation of REE at TAG reveals that positive curvature in REE vs. Fe plots, argued previously to reflect continuous REE uptake (i.e., increasing Kd; German et al., 1990), may result from local depletion of the dissolved REE pool by partitioning onto Fe particles at Fe > 100 nM. Similar drawdown effects could contribute to the variable degrees of curvature observed for all seawater-source particle-reactive species in plumes that are sampled at high particulate Fe concentration. In sum, REE behavior in hydrothermal plumes is more consistent with equilibrium adsorption and mixing of distinct particle types, than with kinetic uptake control. Precise measurements of REEs in modern ridge-crest metalliferous sediments could be compared to the endmember composition calculated from the plume data to evaluate long-term changes in REE of the hydrothermal component. 相似文献