Deep-Sea Nodules and Co-rich Mn Crusts     

G. P. Glasby  Zhilei Sun 《Marine Georesources & Geotechnology》2013,31(1):72-78

The mining of deep-sea manganese nodules has been a topic of interest since J.L. Mero undertook his preliminary studies in the 1960s to evaluate the prospects for mining deep-sea nodules. Despite the great deal of investment in deep-sea mining over more than 40 years, there has still been no successful attempt to mine the deep-sea nodules on a commercial scale. One of the major problems is that the nodules cannot be brought to the surface with the necessary amounts of recoverable nickel, cobalt and zinc to warrant the initial high investment necessary for this operation. It therefore appears that in the short term, deep-sea manganese and Co-rich Mn crusts will not be mined on a commercial scale in the foreseeable future. Nonetheless, investigations of deep-sea mineral deposits by a number of nations will continue and enable us to understand the deep-sea environment in increasing detail, which is necessary in view of the great extent of the deep oceans which cover an area of about 66% of the Earth's surface.  相似文献   

生物土壤结皮研究：进展、前沿与展望   总被引：43，自引：2，他引：41  

李新荣  张元明  赵允格 《地球科学进展》2009,24(1):11-24

生物土壤结皮是由隐花植物和相关土壤微小生物与表层土壤颗粒胶结而形成的复合体,与维管束植物覆盖一样,它是干旱区地表的重要覆盖类型(其盖度达40%)。生物土壤结皮是荒漠生态系统组成和地表景观的重要特征,在不同生物气候区的荒漠景观过程、土壤生态过程、土壤水文过程、土壤生物过程和地球化学循环过程,以及干旱半干旱地区生态修复过程中发挥着重要作用。关于生物土壤结皮的研究是地学和生物学学科交叉的前沿研究领域,已成为国际干旱区地表过程研究的重要核心科学问题之一。综述了国内外该领域最新研究进展,分析了研究的趋势,讨论了其前沿科学问题和未来研究的重点,以期促进我国生物土壤结皮的研究,加深对我国干旱半干旱区地表过程的认识。  相似文献   

Geochemistry of Some Marine Fe–Mn Nodules and Crusts with Respect to Pt Contents     

Alexandre Raphael Cabral  Carl‐Diedrich Sattler  Bernd Lehmann  Harilaos Tsikos 《Resource Geology》2009,59(4):400-406

Bulk chemical analyses for Pt and Pd in marine Fe–Mn nodules and crusts from different provenances are presented, together with a wide range of elements. Platinum contents vary from 70–328 ppb, whereas Pd contents extend from 0.6–4.7 ppb only. Bromine and Pb show strong positive correlations with Pt. Lead is remarkably enriched in Fe–Mn precipitates over seawater, but Br is a conservative‐type element in seawater and shows no enrichment in Fe–Mn precipitates. Hence, the Pt–Br–Pb element association combines two elements, Br and Pb, of extremely contrasting enrichment factors in Fe–Mn precipitates.  相似文献   

The PM₁₀and PM_2·5 dust generation potential of soils/sediments in the Southern Aral Sea Basin, Uzbekistan     

A. Singer  T. Zobeck  L. Poberezsky  E. Argaman 《Journal of Arid Environments》2003,54(4):705-728

The objective of this study was to assess the contribution of the major soil/sediment surfaces in the Southern Aral Sea Basin to the dust generation potential of this region. Eight crusts and soils/sediments from seven sites, representative of these surfaces, were sampled in the field and their major characteristics (particle size distribution, organic carbon content, carbonate content, salt content and composition) that are related to dust generation, were determined. The PM₁₀ and PM_2·5 dust generation potential of the materials was determined in the laboratory using the Lubbock Dust Generation, Analysis and Sampling System (LDGASS). The highest amount of PM₁₀ dust (579·3 mg.m⁻³) was generated from the Takyr crust material. The lowest by one Solonchak salt crust material (39·6 mg.m⁻³). Salt crusts from the desiccated Aral Sea bottom generated intermediate amounts of dust.The experimental results indicate that the Takyrs and Takyr-like soils, that occupy over 1 million ha in the Southern Aral Sea Basin, constitute the surfaces with the highest potential for being the source for the severe dust storms of the area. Second to the Takyr soils, the Solonchaks and Solonchak-like soils, also with an extent of over 1 million ha, contribute highly saline dust. To these must be added a large, as yet uncharted, proportion of the approximately 4 million ha of exposed sea bed, that exhibit Solonchak-like characteristics.  相似文献   

再论冀北古缝合带的证据   总被引：4，自引：0，他引：4  

王仁民  倪志耀  袁建平  童英 《岩石矿物学杂志》2002,21(4):327-335

近南北走向的冀北太古宙麻粒岩相古陆核北侧受到近东西走向的古元古代造山带的交切。在陆缘沉积增生带内发现大量残存的古洋壳残片，包括蛇纹石化方辉橄榄岩、且鬣刺结构的苦橄岩、透闪石岩、橄长岩、异剥钙榴岩、细碧岩、退变榴辉岩、基性枕状熔岩和斜长花岗岩等，与陆缘沉积岩一起构成古蛇绿岩混杂带。推断该蛇绿岩混杂带从古元古代开始直到新元古代末有逐步向北后退发育的特点。  相似文献   

大洋磷酸盐化作用对富钴结壳元素富集的影响   总被引：23，自引：2，他引：23  

潘家华  刘淑琴  Eric DeCarlo 《地球学报》2002,23(5):403-407

中国首次对与大洋富钴结壳密切相关的磷酸盐化作用进行了研究。对取自西太平洋麦哲伦海山区一厚度为 10cm的富钴结壳样品 ,自顶至底以 5mm间距采取了 2 0个分层样品进行了成矿元素和稀土元素分析。结果表明 ,未被磷酸盐化的新结壳和磷酸盐化的老结壳间主要成矿元素的含量相差显著。老结壳中Fe、Mn、Si、Al、Zn、Mg、Co、Ni、Cu元素亏损 ,亏损次序为Co >Ni>Mg >Al>Mn >Si>Cu >Zn >Fe;而Ca、P、Sr、Ba、Pb元素含量增加 ,富集次序为P >Ca >Ba >Pb >Sr。研究认为 ,结壳中磷酸盐化作用的强弱制约着富钴结壳成矿元素含量的变化 ,磷酸盐化作用是造成老结壳中主要成矿元素Co、Ni等贫化流失的根本原因。研究还表明 ,磷酸盐化作用对富钴结壳的稀土元素丰度也产生一定影响 ,使老结壳的稀土总量和Ce含量高于新结壳 ,但未显著改变其稀土配分模式和分馏特征。研究证实 ,老结壳的Y正异常与磷酸盐化作用无关。磷酸盐化作用的研究为富钴结壳矿产资源的评价和综合利用提供了有用信息。  相似文献   

Compositional variation and genesis of ferromanganese crusts of the Afanasiy—Nikitin Seamount, Equatorial Indian Ocean   总被引：1，自引：0，他引：1  

R. P. Rajani  V. K. Banakar  G. Parthiban  A. V. Mudholkar  A. R. Chodankar 《Journal of Earth System Science》2005,114(1):51-61

Eight ferromanganese crusts (Fe-Mn crusts) with igneous and sedimentary substrates collected at different water depths from the Afanasiy-Nikitin Seamount are studied for their bulk major, minor and rare earth element composition. The Mn/Fe ratios < 1.5 indicate the hydrogenetic accretion of the Fe-Mn hydroxides. These Fe-Mn crusts are enriched in Co (up to 0.9%, average ∼ 0.5%) and Ce. The Ce-content is the highest reported so far (up to 3763 ppm, average ∼ 2250 ppm) for global ocean seamount Fe-Mn crusts. In spite of general similarity in the range of major, minor, and strictly trivalent rare earth element composition, the dissimilarity between the present Fe-Mn crusts and the Pacific seamount Fe-Mn crusts in Co and Ce associations with major mineral phases indicates inter-oceanic heterogeneity and region-specific conditions responsible for their enrichment. The decrease in Ce-anomaly (from ∼ 8 to ∼ 1.5) with increasing water depth (from ∼ 1.7 km to ∼ 3.2 km) might suggest that the modern intermediate depth low oxygen layer was shifted and sustained at a deeper depth for a long period in the past.  相似文献   

Tracing the history of submarine hydrothermal inputs and the significance of hydrothermal hafnium for the seawater budget—a combined Pb-Hf-Nd isotope approach     

Tina van de Flierdt  Martin Frank  James R Hein  Detlef Günther 《Earth and Planetary Science Letters》2004,222(1):259-273

Secular variations in the Pb isotopic composition of a mixed hydrogenous-hydrothermal ferromanganese crust from the Bauer Basin in the eastern Equatorial Pacific provide clear evidence for changes in hydrothermal contributions during the past 7 Myr. The nearby Galapagos Rise spreading center provided a strong hydrothermal flux prior to 6.5 Ma. After 6.5 Ma, the Pb became stepwise more radiogenic and more similar to Equatorial Pacific seawater, reflecting the westward shift of spreading to the presently active East Pacific Rise (EPR). A second, previously unrecognized enhanced hydrothermal period occurred between 4.4 and 2.9 Ma, which reflects either off-axis hydrothermal activity in the Bauer Basin or a late-stage pulse of hydrothermal Pb from the then active, but waning Galapagos Rise spreading center.Hafnium isotope time-series of the same mixed hydrogenous-hydrothermal crust show invariant values over the past 7 Myr. Hafnium isotope ratios, as well as Nd isotope ratios obtained for this crust, are identical to that of hydrogenous Equatorial Pacific deep water crusts and clearly indicate that hydrothermal Hf, similar to Nd, does not travel far from submarine vents. Therefore, we suggest that hydrothermal Hf fluxes do not contribute significantly to the global marine Hf budget.  相似文献   

Salt ramps: Wind-induced depositional features on Tunisian playas     

Andrew C. Millington  Nicholas A. Drake  Kevin White  Robert G. Bryant 《地球表面变化过程与地形》1995,20(2):105-113

Semicircular and crescent-shaped accumulations of salt crystals developed on salt crusts were measured on three Tunisian playas in September 1990. These features have been termed salt ramps. Their morphology and chemistry suggest that they are formed in the late stages of shallow ephemeral lake desiccation in playa basins. They form by salt precipitation from shallow brine lakes that are blown across salt-encrusted playa surfaces by the wind. Moreover, they appear to be short-lived features and their degradation is related to the flooding of playas with less saline water, and possibly rainfall and deflation.  相似文献   

Erodibility of some crust forming soils/sediments from the Southern Aral Sea Basin as determined in a wind tunnel     

E. Argaman  A. Singer  H. Tsoar 《地球表面变化过程与地形》2006,31(1):47-63

Severe dust storms in the Southern Aral Sea Basin have become common with the desiccation of the sea. The high incidence of dust in the area has had severe ecological consequences. Within the framework of efforts to reduce this phenomenon, deflatability as well as deflatability‐related characteristics of some prominent soils/sediment surfaces in the Southern Aral Sea Basin were examined. The materials included a salt crust from a developed Solonchak, a Takyr crust and a Takyr‐like soil, and salt crusts from undeveloped Solonchaks formed on the exposed bottom of the Aral Sea. Characteristics determined were particle size distribution, dry aggregate size distribution and salt, carbonate and organic carbon contents. Deflatability was examined using a suction type wind tunnel with a SENSIT‐type sensor to detect airborne unconsolidated material, on materials treated to different moisture levels and with a chemical stabilizer, and on restored crusts created from the unconsolidated materials. Fine sand dominates in the materials, and in the Takyr crust and Takyr‐like soils is accompanied by significant amounts of silt and clay. All materials contain moderate amounts of carbonate and are low in organic matter. All soils/sediments contain salts, but in the salt crusts of the Solonchaks the salt fraction dominates. They all have more than 50 per cent PM₈₅₀ (particles with diameter <850 µm), indicating a relatively high deflatability potential. The materials from the Takyr crusts and Takyr‐like soil with a high proportion of fine aggregates had the lowest threshold friction velocities, while the salt crusts of the Solonchaks with a high proportion of coarse aggregates had the highest. This suggests that Takyrs and Takyr‐like soils are the most deflatable and Solonchak soils the least deflatable. These differences are attributed to the presence of salts that create stable, large aggregates in the Solonchak crusts. Wetting of the materials to three moisture levels considerably increased threshold friction velocity. The increase was most prominent in the salt‐rich materials, and was attributed to the rapid formation of surface films by drying in the course of the wind tunnel determinations. Applications of chemical stabilizers at two levels also considerably increased threshold friction velocity. On the restored crusts, threshold friction velocity dramatically increased, occasionally to non‐recordable values. This increase was monitored with both the salt crusts characteristic for the Solonchak soils and the fine‐grained crusts characteristic for the Takyr soils. The stability was attributed to the tightly packed salt particles in the salt crusts, and to the cohesive properties of the fine‐grained materials in the Takyr crusts. Once the crusts were ruptured, however, strong deflation commenced. These results suggest that by maintaining moisture in the soils/sediments (for example, by maintaining a high water table in the Amu‐Darya river flood plain) deflation can be reduced. By the same means, deflation can be reduced by creating new crusts or by preserving existing crusts. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献