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-

The Influence of Seafloor Hydrothermal Activity on Major and Trace Elements of the Sediments From the South Mid-Atlantic Ridge

Sediment samples obtained from the South Mid-Atlantic Ridge were analyzed for the major and trace elements by inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry. Results revealed that the contents of elements(e.g., Fe, Mn, Cu, Zn, V, Co) were high in samples 22V-TVG10 and 26V-TVG05 from the sites near the hydrothermal areas, and low in sample 22V-TVG14, which was collected far from the hydrothermal areas. The contents of Ca, Sr and Ba in the samples showed opposite trends. A positive correlation between the concentrations of metallic elements(Cu, Zn, Co, Ni, Pb, V) and Fe in the samples were observed. These results are consistent with chemical evolution of the dispersing hydrothermal plume.

Impact of residual zircon on Nd-Hf isotope decoupling during sediment recycling in subduction zone

The subduction factories in convergent plate margins exert crucial control on recycling terrestrial components and returning to the overlying crust. The Nd and Hf isotopic systems provide potential tracers to evaluate these processes. Here we present a case where these isotopic systems are decoupled in a suite of granites from the Chinese Altai, showing a wide range of εHf(t) values(from -4.7 to +10.8) in contrast to a limited range of εNd(t) values(from -5.8 to -1.9). The zircon xenocrysts occurring frequently in these rocks show markedly negative εHf(t) values(from -34.3 to -6.5) and positive d7 Li values(from +12.5 to +18.2). We propose a model to explain the observed relationship between residual zircon and Nde Hf isotope decoupling. We suggest that the Altai granites originated from partial melting of subducted slab components under relatively low temperature conditions which aided the residual zircon from oceanic sediments to inherit and retain a significant amount of177 Hf in the source, thereby elevating the^(176) Hf/^(177) Hf ratio of the melt, and decoupling from the^(143) Nd/^(144) Nd ratio during the subsequent magmatic processes. Our study illustrates a case where sediment recycling in subduction zone contributes to decoupling of Nd and Hf isotopic systems, with former providing a more reliable estimate of the source characteristics of granitic magmas.

Geochemical characteristics of REY-rich pelagic sediments from the GC02 in central Indian Ocean Basin

As a potential mineral resource, the clay minerals enriched in rare earth elements including yttrium（REY） in the deep sea have been attracting great attention. However, the enrichment mechanism of REY remains unclear. To understand the geochemical characteristics and factors controlling REY enrichment in zeolite clay in the deep sea, we conducted mineral identification by XRD, major and trace element measurements by XRF and REY analyses by ICP-MS on a 1.4-m-long sediment core（GC02） located in the Central Indian Oceanic Basin（CIOB）. The main findings include：（1） the core sediments in GC02 possess elevated REY contents and exhibited a strong negative Ce anomaly, an apparent MREE bulge and positive Y anomaly. These were comparable with typical REY-rich clays in the Pacific Ocean, indicating the similar REY enrichment mechanism and the presence of REY-rich clays in the CIOB;（2） in comparison with the dataset from the Wharton Basin and DSDP site 213, the higher content of REY and stronger PAAS（Post Archean Australian Shale） normalization patterns in the GC02 sediments were likely caused by the weaker impact of terrigenous materials of GC02. The CIOB was suggested to be a promising place hosting REY rich pelagic sediments.

Modeling the circulation and sediment transport in the Beibu Gulf

Water circulation and sediment transport in the Beibu Gulf are important for its environmental protection and resource exploitation.By employing the Regional Ocean Modeling System（ROMS）,we studied the seasonal variation of circulation,sediment transport and long-term morphological evolution in the Beibu Gulf.The simulation results show that the circulation induced by tide and wind is cyclonic both in winter and summer in the gulf and that the wind-driven circulation is stronger in winter than that in summer.The sediment concentration is higher in the Qiongzhou Strait,west of the Hainan Island and the coast of Vietnam and the Leizhou Peninsula.The sediment is transported westwards in winter and eastwards in summer in the Qiongzhou Strait.The west entrance of the Qiongzhou Strait is dominated by westward transport all the year round.The sediment discharged by rivers is deposited near the river mouths.The simulated result demonstrates that the sediment transport is mainly controlled by tidal induced bottom resuspension in the Beibu Gulf.Four characteristics are summarized for the distribution patterns of erosion and deposition.（1） The erosion and deposition are insignificant in most area of the gulf.（2） Sediment deposition is more significant in the mouths of Qiongzhou Strait.（3） The erosion is observed in the seabed of Qiongzhou Strait.（4） Erosion and deposition occur alternatively in the west of Hainan Island.

Suspended sediment concentration mapping based on the MODIS satellite imagery in the East China inland, estuarine, and coastal waters

The purpose of this research is to improve the retrieval accuracy for the suspended sediment concentration(SSC) from in situ and satellite remote sensing measurements in turbid East China estuarine and coastal waters. For this aim, three important tasks are formulated and solved: 1) an estimation of remote-sensing reflectance spectra R_(rs)(λ) after atmospheric correction; 2) an estimation of R_(rs)(λ) from the radiometric signals above the air-water surface; and 3) an estimation of SSC from R_(rs)(λ). Six different models for radiometric R_(rs)(λ) determination and 28 models for SSC versus R_(rs)(λ) are analyzed based on the field observations made in the Changjiang River estuary and its adjacent coastal area. The SSC images based on the above-mentioned analysis are generated for the area.