The economics of mining seabed manganese nodules: A case study of the Indian Ocean nodule field

Abstract

Because of ever-growing demand for strategic metals, the focus of the international community has fallen on deep sea manganese nodules occurring at a water depth of more than 4500?m. We present an economic appraisal and strategy for mining of nodules from the Indian Ocean Nodule Field- one of the four economically potential areas in the world oceans. In contrast to the prevailing perception of non-viability of nodule mining, our analysis indicates a fair degree of economic feasibility and commercial sustainability to mine the deep-sea manganese nodules.     

A metasomatic setting,the Russian River Arch,and gravitational emplacement in the history of eclogites at the classic eclogite locality of Jenner,California, USA

ABSTRACT

Blocks of metamorphic rock designated as ‘high-grade’ blocks, commonly less than 100 m in diameter, consisting of garnet-glaucophane- and hornblende-schists and gneisses and rare eclogite, are widely distributed within mélanges of the Franciscan (accretionary) Complex of California. Eclogite-glaucophane schist blocks present at Jenner, California, have been studied for petrographic, geochemical, structural, and age characteristics, but their relationship to associated Franciscan rocks is poorly understood. The studied blocks are not in situ, but rather occur in landslide deposits and beach sands. The landslide deposits overlie the low to middle slope exposures of sandstone-rich broken formations of the Franciscan Complex that are not known to contain high-grade blocks. Geochemical studies suggest a serpentinite host for the blocks. Upslope, a serpentinite-matrix mélange contains numerous high-grade blocks, including rare retrograded eclogite, and is the likely block source. The Jenner terrain as a whole was uplifted relative to rocks to the north and south near Annapolis and Freestone, respectively, by uplift along the post-Pliocene Russian River (anticlinal) Arch, as indicated by the regional distribution of arching, wave-cut, post-Franciscan surfaces with overlying Miocene/Pliocene marine sedimentary rocks. Local uplift increased landsliding and colluvial downslope movement of the blocks. In addition, local, wave-influenced transportation of smaller blocks, together with the downslope mass movements, brought the high-grade blocks to their present positions. The high-grade blocks are thus displaced from upslope exposures of the original serpentinite-matrix mélange host, in which the blocks likely experienced the metasomatism that converted eclogite to glaucophane schist. In general, the relationship of blocks to the original serpentinite host is a critical element of subduction zone architecture related to subduction zone processes and history, and should be analysed, in any studies that seek to explain the architecture and history of any accretionary complex with similar high-grade blocks.     

Comparison of cloud-top height retrievals from ground-based 35 GHz MMCR and GMS-5 satellite observations at ARM TWP Manus site

Retrievals of cloud-top heights from the ARM 35 GHz Millimeter Wave Cloud Radar (MMCR) located on Manus Island are compared to those from the GMS-5 satellite as a means to evaluate the accuracy of both MMCR and GMS-5 retrievals, as well as to ascertain their limitations. Comparisons are carried out for retrievals of both single-layer and multilayer clouds as seen by radar, but only for satellite-detected clouds with 100% amount within a 0.3×0.3° domain centered at the ARM site of one cloud type (i.e., low, middle, or high). Mean differences, with 95% confidence limits, between radar- and satellite-retrieved cloud-top heights (i.e., radar-retrieved cloud-top heights−satellite-retrieved cloud-top heights) are 0.3±0.3 km for single-layer clouds and −0.7±0.3 km for multilayer clouds. The study reveals that for thick clouds (i.e., cloud base ≤1 km and cloud thickness ≥10 km), which are representative of convective towers with no/light precipitation as well as thick anvil clouds, retrievals from the MMCR agree well with those from satellite with mean differences of 0.0±0.4 and −0.2±0.3 km for single-layer and multilayer clouds, respectively. For clouds of lesser thickness, mean cloud-top heights derived from satellite are lower than those derived from radar by as much as 2.0 km. It is also shown that for convective clouds with heavy precipitation, MMCR retrievals underestimate the cloud-top heights significantly.     

Light-cued emergence and re-entry events in a strongly tidal estuary

Acoustic backscatter from an active sonar system (TAPS-6) over a range of six frequencies between 265 kHz and 3 MHz revealed characteristics of emergence and reentry events within 1 h of sunset and sunrise, respectively, at a site 10 m deep in the Damariscotta River estuary, Maine. Emergence traps indicated that the mysid shrimpNeomysis americana was the dominant migrator. Daily fluctuation in irradiance influenced the timing of dusk emergence. Local variability in irradiance apparently caused populations to emerge occasionally before sunset or to leave the surface after the beginning of nautical twilight near dawn. Emergence before sunset was marked by slower-than-average ascent, and departure from the surface after initiation of nautical twilight was marked by faster-than-average descent. This pattern would be expected for populations avoiding visual predators by concealment in dark water. Mean ascent (0.29 ± 0.03 cm s⁻¹ [±1 SE]) and descent (−0.26 ± 0.02 cm s⁻¹) velocities showed little difference in magnitude, suggesting that a similar mechanism controls both. Ascent initiation times for the first such event of the night were consistent with a cue based on relative rate of change in light intensity and inconsistent with either the progress of isolumes or with absolute rate of change in light intensity.     

Constraints on paleolake levels,spillways and glacial lake history,north-central Ontario,Canada

The recognition of ice-marginal deltas constructed during the formation of the Nakina II moraine and a previously unrecognized spillway, in the vicinity of Longlac, northern Ontario, indicates that existing concepts of ancestral lake level history and drainage systems in the Lake Superior–Lake Nipigon region is inadequate. Based on isostatically corrected digital elevation maps, ice-marginal deltas of the Nakina II moraine probably formed at the level of glacial Lake Minong, most likely Minong III, and not glacial Lake Nakina as has been commonly suggested. In addition, the presence of a spillway near Longlac indicates that lake water drained southward through the Mullet Outlet–Pic River system immediately following ice-marginal retreat from the Nakina II moraine and not eastward as previously proposed. Architectural-element analysis of exposures within the spillway indicates hyperconcentrated outbursts of meltwater produced thick channel-fill elements during flood conditions with peak-velocities exceeding 3 m/s. Subsequent retreat of ice from the Pic River valley to the east, may have allowed waters of Lake Agassiz, Lake Barlow–Ojibway, or both, to drain into post-Minong lake levels in the Lake Superior basin. These findings place major constraints on previously proposed concepts of northeastern or eastern outlets of Lake Agassiz.     

Development of a numerical groundwater flow model using SRTM elevations

Remotely-sensed elevation data are potentially useful for constructing regional scale groundwater models, particularly in regions where ground-based data are poor or sparse. Surface-water elevations measured by the Shuttle Radar Topography Mission (SRTM) were used to develop a regional-groundwater flow model by assuming that frozen surface waters reflect local hydraulic head (or groundwater potential). Drainage lakes (fed primarily by surface water) are designated as boundary conditions and seepage lakes and isolated wetlands (fed primarily by groundwater) are used as observation points to calibrate a numerical flow model of the 900 km² study area in the Northern Highland Lakes Region of Wisconsin, USA. Elevation data were utilized in a geographic information system (GIS) based groundwater-modeling package that employs the analytic element method (AEM). Calibration statistics indicate that lakes and wetlands had similar influence on the parameter estimation, suggesting that wetlands might be used as observations where open water elevations are unreliable or not available. Open water elevations are often difficult to resolve in radar interferometry because unfrozen water does not return off-nadir radar signals.     

Geoarchaeological context of late Pleistocene and early Holocene occupation at the Cooper's Ferry site,western Idaho,USA

Archaeological excavations at the Cooper's Ferry site (10IH73), located in the lower Salmon River canyon of western Idaho, revealed a stratified sequence of cultural occupations that included a pit feature containing stemmed points. However, radiocarbon ages determined on charcoal and bone in the pit feature range between ca. 12,000 yr B.P. and 7300 yr B.P. By considering the effects of postdepositional processes on dated samples, and by comparing the lithostratigraphy, pedostratigraphy, and stable isotope geochemistry of pedogenic carbonates from Cooper's Ferry with other well‐dated stratigraphic sections in the canyon, site geochronology is clarified. Based on the presence of key radiocarbon ages and distinctive stratigraphic criteria, we argue that the initial occupation and interment of lithic artifacts in a pit feature at Cooper's Ferry occurred during the late Pleistocene, between ca. 11,410 and 11,370 yr B.P., and not during the early Holocene. Records of geomorphic change and paleoenvironmental proxy data from the site reveal that early occupation in the lower Salmon River canyon corresponds with evolving riparian ecosystems, which must be considered as a contextual aspect of local prehistoric cultural ecology. © 2004 Wiley Periodicals, Inc.     

Proposed GSSP for the base of Cambrian Stage 9, coinciding with the first appearance of <Emphasis Type="Italic">Agnostotes orientalis</Emphasis>, at Duibian,Zhejiang, China

Exposed in natural outcrops near the Duibian Village, Jiangshan County, Zhejiang Province, China, the Duibian B section is proposed as the boundary stratotype for the base of an unnamed stage termed provisionally Cambrian Stage 9. The proposed position of the GSSP is 108.12 m above the base of the Huayansi Formation, at a horizon coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalis. This horizon coincides also with the first appearance of the cosmopolitan polymerid trilobite Irvingella angustilimbata. The section fulfills all the requirements for a GSSP, and the horizon can be constrained not only by the primary stratigraphic marker (A. orientalis) but also with secondary biostratigraphic, chemostratigraphic, and sequence-stratigraphic correlation tools. The first appearance of A. orientalis is one of the most readily recognizable levels in Cambrian, and can be correlated with precision to all paleocontinents. Supported by Chinese Academy of Sciences (Grant No. KZCX2-YW-122), the Ministry of Science and Technology of China (Grant Nos. 2006FY120300, 2006CB806400), National Natural Science Foundation of China (Grant Nos. 40072003, 40023002, 40332018, 40672023, 40602002), and the U.S. National Science Foundation (Grant No. EAR-0106883)     

Incorporating nonlinear isotherms into robust multilayer sorptive barrier design

Sorptive barrier technologies have emerged as useful tools for addressing a wide range of remediation problems. When simulating barrier performance, numerous isotherm expressions are available for relating aqueous and sorbed concentrations. However, isotherm selection is non-trivial because alternative expressions may yield comparable fits to experimental data. Additionally, concentration data collected for parameter fitting is often outside the range of concentrations relevant to simulating barrier performance. This incompatibility necessitates extrapolation of isotherm behavior during simulation–optimization. Consequently, equally plausible isotherms may predict significantly different barrier performance.Numerical experiments involving organic contaminants were performed to examine the influence of isotherm selection and extrapolation on optimal barrier design. Ten isotherms were calibrated to existing experimental data and evaluated using information-theoretic selection criteria. When incorporated into simulation–optimization, extrapolation effects were clearly evident and optimal designs varied according to the chosen isotherm. To ensure robust barrier design in the presence of such variability, a simple methodology is proposed that utilizes a piecewise-minimum isotherm concept. By favoring plausible isotherms that predict the least amount of sorption, the methodology encourages conservative barrier design while respecting available data.