Re-Os isotope systematics of sediments of the Brahmaputra River system     

Sunil K. Singh  Christian France-Lanord 《Geochimica et cosmochimica acta》2003,67(21):4101-4111

Re-Os analyses were performed on suspended loads and coarser grained bank sediments of the Brahmaputra River system. Re and Os concentrations of these sediments vary from 7 to 1154 ppt and from 3 to 173 ppt, respectively. ¹⁸⁷Os/¹⁸⁸Os ratios range from 0.178 to 6.8, and thus vary from nearly mantle to very radiogenic crustal values. Nevertheless, most of the sediments have ¹⁸⁷Os/¹⁸⁸Os ratios less than 1.5, and nearly all of the samples of the Brahmaputra main channel have ratios less than 1.2. Thus, as previously suggested, the Brahmaputra is much less radiogenic than the Ganga. The Siang River, the northern extension of the Brahmaputra, is quite radiogenic in Os despite receiving sediments from the Tsangpo River, which flows along a suture zone with ultramafic outcrops. The Brahmaputra main channel has a fairly constant ¹⁸⁷Os/¹⁸⁸Os ratio even though its tributaries contribute sediments with very heterogeneous Os isotopic compositions. These data, along with the corresponding Nd isotopic compositions, suggest that about 60-90% of the sediment in the Brahmaputra system is derived from Himalayan formations (Higher Himalaya and Lesser Himalaya) whereas 10-40% comes from ophiolite-bearing sequences, perhaps eastern equivalents of those of the Transhimalayan Plutonic Belt. Os data also confirm previously published Sr and Nd results, indicating that about half of the sediments delivered to the Brahmaputra are supplied by the Siang River, while the Himalayan and the eastern tributaries account for 40 and 10%, respectively.The lower ¹⁸⁷Os/¹⁸⁸Os of the Brahmaputra River compared to that of the Ganga is due to two factors. One is the more limited presence of the Lesser Himalaya and hence the lower black shale content of the eastern Himalaya. The other is the non-radiogenic Os supplied by the eastern and southern tributaries, reflecting the presence of mantle-derived lithologies in this region. Despite the lower sediment supply from these tributaries, they contribute greatly to the Os budget of the Brahmaputra River. This study indicates that the Brahmaputra River has little effect on the present-day seawater Os budget. However, reconsideration of this budget suggests that the Ganga, which provides the most radiogenic Os of major rivers studied to date, may have significant impact on the marine Os isotopic composition. The Indo-Asian collision cannot be excluded as an important cause of the increase in the marine ¹⁸⁷Os/¹⁸⁸Os over the past 16 million years until the contributions of all of the rivers draining the Himalayan Tibetan Plateau are known.  相似文献   

Recycling of Cathode Ray Tubes (CRTs) in Electronic Waste     

Sunil Herat 《洁净——土壤、空气、水》2008,36(1):19-24

The management of used electrical and electronic equipment (EEE) or e‐waste is a significant problem worldwide due to rapid uptake of the technology and early obsolescence of EEE. Cathode ray tubes (CRTs) from used televisions and computer monitors represent a major e‐waste problem as they consist of glass with different compositions. The front panel is a lead‐free barium‐strontium glass whereas parts such as the funnel hidden inside are composed of glass with lead oxides. Regulations require the glass from waste CRTs to be recycled or re‐utilized. Closed‐loop recycling and open‐loop recycling are two principal ways of recycling CRT glass. The aim of this paper is to examine the technical characteristics and composition of the CRTs, its generation, environmental impacts and related regulatory requirements and to review the current technologies and their limitations for recycling CRT glass and its end use.  相似文献   

Numerical modeling of the development of southeastern Red Sea continental margin     

Sunil Kumar Dwivedi  Daigoro Hayashi 《地震学报(英文版)》2009,(3):239-249

The Red Sea continental margin (RSCM) corresponds to a wide hinge zone between Red Sea and Arabian plate. This margin has been studied through geological and geophysical observations primarily in regard to the evolution of Red Sea rift. This margin is characterized by occurrence of thin sediments, significant onshore uplift, tectonic subsidence of the offshore sedimentary basin, active faulting and seismicity. Studies indicate that sedimentary sequences of the margin are deformed by faults and folds resulti...  相似文献   

IAG/AIG Newsletter No. 29 (3/2013)          下载免费PDF全文

Emmanuel Reynard  Sunil Kumar De 《地球表面变化过程与地形》2014,39(3):419-425

  相似文献   

International association of geomorphologists     

Sunil Kumar De 《地球表面变化过程与地形》2010,35(11):1368-1371

  相似文献   

Chemical erosion in the eastern Himalaya: Major ion composition of the Brahmaputra and δC of dissolved inorganic carbon     

Sunil K. Singh  M.M. Sarin 《Geochimica et cosmochimica acta》2005,69(14):3573-3588

Major ion composition of waters, δ¹³C of its DIC (dissolved inorganic carbon), and the clay mineral composition of bank sediments in the Brahmaputra River System (draining India and Bangladesh) have been measured to understand chemical weathering and erosion and the factors controlling these processes in the eastern Himalaya. The time-series samples, collected biweekly at Guwahati, from the Brahmaputra mainstream, were also analyzed for the major ion composition. Clay mineralogy and chemical index of alteration (CIA) of sediments suggest that weathering intensity is relatively poor in comparison to that in the Ganga basin. This is attributed to higher runoff and associated physical erosion occurring in the Brahmaputra basin. The results of this study show, for the first time, spatial and temporal variations in chemical and silicate erosion rates in the Brahmaputra basin. The subbasins of the Brahmaputra watershed exhibit chemical erosion rates varying by about an order of magnitude. The Eastern Syntaxis basin dominates the erosion with a rate of ∼300 t km⁻² y⁻¹, one of the highest among the world river basins and comparable to those reported for some of the basaltic terrains. In contrast, the flat, cold, and relatively more arid Tibetan basin undergoes much slower chemical erosion (∼40 t km⁻² y⁻¹). The abundance of total dissolved solids (TDS, 102-203 mg/L) in the time-series samples collected over a period of one year shows variations in accordance with the annual discharge, except one of them, cause for which is attributable to flash floods. Na* (Na corrected for cyclic component) shows a strong positive correlation with Si, indicating their common source: silicate weathering. Estimates of silicate cations (Na_sil+K_sil+Ca_sil+Mg_sil) suggest that about half of the dissolved cations in the Brahmaputra are derived from silicates, a proportion higher than that for the Ganga system. The CO₂ consumption rate due to silicate weathering in the Brahmaputra watershed is ∼6 × 10⁵ moles km⁻² y⁻¹; whereas that in the Eastern Syntaxis subbasin is ∼19 × 10⁵ moles km⁻² y⁻¹, similar to the estimates for some of the basaltic terrains. This study suggests that the Eastern Syntaxis basin of the Brahmaputra is one of most intensely chemically eroding regions of the globe; and that runoff and physical erosion are the controlling factors of chemical erosion in the eastern Himalaya.  相似文献   

Mortar coupling and upscaling of pore-scale models     

Matthew T. Balhoff  Sunil G. Thomas  Mary F. Wheeler 《Computational Geosciences》2008,12(1):15-27

Pore-scale models are becoming increasingly useful as predictive tools for modeling flow and transport in porous media. These models can accurately represent the 3D pore-structure of real media. Currently first-principles modeling methods are being employed for obtaining qualitative and quantitative behavior. Generally, artificial, simple boundary conditions are imposed on a model that is used as a stand-alone tool for extracting macroscopic parameters. However, realistic boundary conditions, reflecting flow and transport in surrounding media, may be necessary for behavior that occurs over larger length scales or including pore-scale models in a multiscale setting. Here, pore-scale network models are coupled to adjacent media (additional pore-scale or continuum-scale models) using mortars. Mortars are 2D finite-element spaces employed to couple independent subdomains by enforcing continuity of pressure and flux at shared boundary interfaces. While mortars have been used in the past to couple subdomains of different models, physics, and meshes, they are extended here for the first time to pore-scale models. The approach is demonstrated by modeling single-phase flow in coupled pore-scale models, but the methodology can be utilized to model dynamic processes and perform multiscale modeling in 3D continuum simulators for flow and transport.  相似文献   

Effect of ion and electron beam on kinetic Alfven wave in an inhomogeneous magnetic field     

A. K. Dwivedi  Sunil Kumar  M. S. Tiwari 《Astrophysics and Space Science》2014,350(2):547-556

Kinetic Alfven waves are examined in the presence of electron and ion beam and an inhomogeneous magnetic field with bi-Maxwellian distribution function. The theory of particle aspect analysis is used to evaluate the trajectories of the charged particles. The expressions for the field-aligned currents, perpendicular currents (with respect to B ₀), dispersion relation and growth/damping rate with marginal instability criteria are derived. The effect of electron and ion beam and inhomogeneity of magnetic field are discussed. The results are interpreted for the space plasma parameter appropriate to the auroral acceleration region of the earth’s magnetoplasma.  相似文献   

Herschel SPIRE fourier transform spectrometer: calibration of its bright-source mode     

Nanyao Lu  Edward T. Polehampton  Bruce M. Swinyard  Dominique Benielli  Trevor Fulton  Rosalind Hopwood  Peter Imhof  Tanya Lim  Nicola Marchili  David A. Naylor  Bernhard Schulz  Sunil Sidher  Ivan Valtchanov 《Experimental Astronomy》2014,37(2):239-252

The Fourier Transform Spectrometer (FTS) of the Spectral and Photometric Imaging REceiver (SPIRE) on board the ESA Herschel Space Observatory has two detector setting modes: (a) a nominal mode, which is optimized for observing moderately bright to faint astronomical targets, and (b) a bright-source mode recommended for sources significantly brighter than 500 Jy, within the SPIRE FTS bandwidth of 446.7–1544 GHz (or 194–671 microns in wavelength), which employs a reduced detector responsivity and out-of-phase analog signal amplifier/demodulator. We address in detail the calibration issues unique to the bright-source mode, describe the integration of the bright-mode data processing into the existing pipeline for the nominal mode, and show that the flux calibration accuracy of the bright-source mode is generally within 2 % of that of the nominal mode, and that the bright-source mode is 3 to 4 times less sensitive than the nominal mode.  相似文献   

Equilibrium Structure of Rotationally and Tidally Distorted Prasad Model Including the Effect of Mass Variation Inside the Star     

Seema Saini  A. K. Lal  Sunil Kumar 《Astrophysics》2014,57(1):119-129

  相似文献