Detrital and authigenic(?) baddeleyite(ZrO_2) in ferromanganese nodules of Central Indian Ocean Basin

Occurrence of baddeleyite（ZrO_2） which is a rare mineral has been recorded in ferromanganese nodules of Central Indian Ocean Basin（CIOB）.The mineral occurs either as independent isolated sub-rounded to elliptical grains or in clusters forming fine subhedral crystals（〈3μm） within ferromanganese concretionary growth bands.The mode of occurrence,texturai features and chemistry of the mineral suggest detrital and possibly an authigenic origin for baddeleyite.For authigenic origin it is proposed that zirconium might have got released either from the terrigenous sediments or the altered seafloor rocks forming halogen complexes and subsequently it has re-precipitated in me form of baddeleyite within manganese nodules under oxic to sub-oxic conditions.

Geochemistry and Origin of Layers in Single Manganese Nodule from the Philippine Sea and Manganese Nodules from Offshore Minami-Torishima, Western Pacific

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.

Image Processing of Manganese Nodules Based on Background Gray Value Calculation

To troubleshoot two problems arising from the segmentation of manganese nodule images-uneven illumination and morphological defects caused by white sand coverage,we propose,with reference to features of manganese nodules,a method called“background gray value calculation”.As the result of the image procession with the aid this method,the two problems above are solved eventually,together with acquisition of a segmentable image of manganese nodules.As a result,its comparison with other segmentation methods justifies its feasibility and stability.Judging from simulation results,it is indicated that this method is applicable to repair the target shape in the image,and segment the manganese nodule image in a short time.Also,it could be used to synchronously process a large number of manganese nodules on different conditions in an image,laying a good foundation for automatic underwater manganese nodule survey.Even if the target in the image is slightly distorted,the statistical data of manganese nodules are still accurate.Moreover,other methods cannot be fully applied to the segmentation of manganese nodule images;in another word,the effectiveness and stability of this method are proved.

Growth Rate Estimates of Supergene Manganese Nodule by ^(40)Ar/^( 39)Ar Isotopic Dating

Increasing world-class, high-grade, and metals-enriched supergene manganese ore deposits have been discovered in the last two decades, making them more and more economically important. However, data on the timing and duration of their formation are sparse, mainly due to the difficulties extracting datable minerals suited to traditional radiometric dating methods. Hollandite, cryptomelane, coronadite, todorokite, and manjiroite are common manganese oxide minerals in supergene environments. These minerals host potassium of variable amounts from 0.1 wt% to 5.0 wt% in their structural sites. This geochemical property provides possibility to date supergene manganese ores by using K-Ar and 40Ar/ 39Ar methods. In this study, we perform 40Ar/ 39Ar dating on a 7.1-cm-thick botryoidal manganese nodule from an ancient weathering profile at Mount Tabor, central Queensland, Australia. Laser microprobe incremental analyses of distinct growth bands, from the inner core through the intermediate bands to the outermost crusts of the nodule, have yielded high quality 40Ar/ 39Ar ages at 27.3 Ma, 20.9 Ma, 19.2 Ma, and 16.1 Ma, respectively. The age results permit preliminary estimates on the average growth rates of the nodule varying from 4.7×10 -3 mm/ka to 7.6×10 -3 mm/ka to 9.0×10 -3 mm/ka, from the core to the rim. Results of this study are of significance in our understanding of the mode, mechanism, process, and climatic conditions in the formation of supergene manganese ore deposits.

Pelagic Manganese Nodules--A New Type of Oncolites

Pelagic manganese nodules from the East Pacific Ocean have been studied using polarizing,scanning electron and transmission electron microscopes. It has been revealed that the manganesenodules are composed of cores and stromatolite coatings. The structures and textures of thesenodules are peculiar to oncolite. Consequently, the pelagic manganese nodules are manganeseoncolites. Based on the stromatolites in the coatings, the manganese oncolites from the East Paci-fic Ocean can be divided into two types. One is smooth on surface and dense inside. Its coatingsare composed mainly of Minima. The other has a knobby surface and is loose internally. Itscoatings consist mainly of Admirabilis. The TEM investigation has also revealed that the con-structors of the manganese oncolites are ultra-microbes. The Minima is constructed byMiniactinomyces chinensis sp. nov. and the Admirabilis is built by Spirisosphaerospora pacifica sp.nov.

Radiochemical studies of deep - sea manganese nodules

Five manganese nodules collected from the Northern Mid - Pacific have been analysed for their U and Th isotopes.lt is found that the enrichment of thorium compared to uranium is universal in deep- sea manganese, nodules and in the top sides of the nodules there are large excesses of Th and Pa decreasing exponentially with depth. For each of the nodules, the concordant growth rates are obtained from three different methods: 230Thex 230Thex/232Th and 231Paex.The growth rates of manganese nodules are closely related to the chemical compositions of the nodules and the types of the underlying sediments. The growth rates of five nodules are determined to be in the range of 0.79-7.4 mm/106a, in agreement with those predicted from the chemical compositions of the nodules. By the comparison of the extrapolated 230Thex,230Thex/232 Th and 231PaeX data from the top and bottom surfaces of the nodule from Site M21 yields, the nodule turnover time is (9.83-13.7)×104a.

Studies on diffusion and profiles of elements in deep-sea manganese nodules

Elemental compositions are measured in manganese nodules collected from the Northern Mid-Pacific floor by inductively-coupled plasma atomic emission spectrometry (1CP-AES) and their growth rates are determined by radiometric methods. The result shows that depth distributions of elements in nodules vary with depth as follows; (i) increase, (ii) decrease and (iii) fluctuation. These internodule variations in elemental compositions are considered to be caused by diffusion and migration of elements in nodules and heterogeneities in textures of nodules. In the present paper, a diffusive model is used to elucidate the inward-increase profile of some elements in nodules. The effective diffusive coefficients are estimated to be of the order of 10-9 cm2/a for Ni, V and Zn in the nodules, which is less than the value reported for radionuclides.

Preparation and Characterization of La Doped Ferrite Using Marine Manganese Nodules as Raw Materials

A kind of La doped ferrite was prepared with marine manganese nodules derived from East Pacific sea-bottom as raw material, NaOH as fluxing reagent, La(NO3)3 as doping agent, by calcination at 1000 ℃ for 5 h. XRD analysis showed that the ferrite products were of a spinel structure, and that its molecular formula could be expressed as MnFe2-xRxO4. SEM images proved that these ferrites showed octahedral and cubic aspects. It was found that there is some relationship between the La doping amount and the magnetic property of the ferrite. When the La doping amount was 0.03, the susceptibility of the ferrite was maximal. The as-prepared La doped ferrite is a kind of soft magnetic material that is easy to be magnetized with rather weak coercive force.

Rare Earth Elements in Manganese Nodules from the Central Pacific Ocean

Manganese nodules in areas CP and CC of the central Pacific are rich in REE. Comparatively speaking,the REE contents of nodules in area CP are hihger than those in area CC; and the REE contents of nodulesfrom seamounts are higher than those of nodules from sea-floor plains and hills. Within the nodules, the REEshow a zonal distribution. The REE distribution patterns of the nodules are similar to those of the sedimentsand have a mirror image relationship with those of the sea water. Trivalent REE were not obviously differenti-ated when they entered into the nodules from the sea water.A major factor causing the difference of REE abundances between nodules and sediments is the redoxconditions. The redox intensity of the ocean floor of the Pacific is controlled mainly by Antarctic Bottom Wat-er(AABW), The iron-bearing facies in the nodules is the main carrier of REE.

Metallic Reserves of Submarine Manganese Nodules to be Estimated and Harnessed Prudently: Evidence from China's Jiaolong Manned Submersible

Since the discovery of oceanic manganese nodules during the expedition of the British ocean-going ship Challenger from 1872 to 1876, research and development for seabed manganese nodules have never ceased owing to the huge economic inducements. Manganese nodules are the black or dark brown, spherical or massive Mn-bearing ores, deposits of which are found on the sea bottom. The nodules are a mixture of silicate and insoluble potassium permanganates （also with sub-Ti, Fe and Na permanganates） that contain more than 30 kinds of metallic elements, among which those of greatest economic interest are Mn （27-30%）, Ni（1.25-1.5%）, Cu（1- 1.4%）, Co（0.2- 0.25 %）, Fe, Si, and AI, with minor amounts of Ca, Na, K, Ti, B, H and O.

Abundance of total bacteria, ATP and manganese-oxidating bacteria in the sediments and manganese nodules of the Northwestern Pacific Ocean

In the seawater and sediments of the ocean, there exist huge quantities of bacteria whose living activities cause various chemical reaction processes. It is demonstrated that microorganisms play a fundamental role on chemical changes of the sediments and diageneses. Over the last twenty years, great interest has been increased about the role of deep-sea bacteria in the ferromanganese sedimentary process. Much work has been done on this aspect in the Atlantic Ocean, the Baltic Sea and the Pacific O-

Study on mineral structural stability of marine 1nm manganate

In order to study the phase transformation between 1nm manganate and 0.7nm manganate, a series of Slum Me^(2+) manganates were made after the synthetic 1nm Na^+ manganate substituted with different kinds of divalent cations. The X-ray diffraction analysis of wet S1nm Me^(2+) manganates after 24 h room temperature dry showed that their basal d-spacing had been changed, indicating that there was phase transformation between 1nm and 0.7nm manganates. Take 1nm manganates with unstable structure collapsed into 0. 7nm manganate by losing one interlayer OH-H_2O, while those with stable structure still retained the 1nm d-spacing. This factor reminds us that the manganese nodule samples must be kept in wet condition to avoid the misleading results. The structural stabdity of 1nn manganate is mainly controlled by the interlayer divalent cations. There is a possitive correlation between the amount of cations in the interlayer and the structural stability, while the capacity of different canons in stabilizing the structure of 1nm manganate is as follows: Ni > Cu > Co > Zn > Ca>Mg > Na.