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81.
82.
韩宗珠 《中国海洋大学学报(自然科学版)》1994,(1)
以微量元素、稀土元素、Sr和Nd同位素变异特征为依据,确定鲁苏榴辉岩为多成因、多来源和多阶段,指出主要是在印支期扬子陆块与华北陆块碰撞造山作用过程中,挤入的上地幔碎片以及不同原岩类型的壳内高压变质岩碎块。燕山晚期的区域构造热事件使得某些榴辉岩的同位素体系再平衡。 相似文献
83.
IwrincrIONOn the evolution of palcoenvironment, salt-water encroachmnt and the distributionof subsurface brine in the LaizhOu Bay area, many researches had been carried out, and muchknowledge abeut the gcolOgical features in this area since Late QUaternary was aCquired' ) (H8nand Wu, l992; Han and Meng, l994; Wen et al. l989). However there was IittIe studyon the sediment geOChemical characteristics since Quaternary. In this Paper, the element strati-graphic characteristics and evolut… 相似文献
84.
Geochemical and hydrodynamic constraints on the distribution of trace metal concentrations in the lagoon of Nouméa, New Caledonia 总被引:1,自引:0,他引:1
Christophe Migon Sylvain Ouillon Xavier Mari Emmanuel Nicolas 《Estuarine, Coastal and Shelf Science》2007,74(4):756
Seawater samples were collected in the lagoon of Nouméa (southwest New Caledonia) along two transects from eutrophic coastal bays to the oligotrophic barrier reef. Land-based emissions to the lagoon were measured with dissolved and particulate concentrations of chromium (Cr) and nickel (Ni), used as tracers of both terrigenous and industrial (Ni ore treatment) activities, as well as dissolved and particulate concentrations of zinc (Zn), used as a tracer of urban effluents. The spatial variability of metal concentrations was related to geochemical and hydrodynamic conditions, i.e., respectively: (1) natural and anthropogenic emission sources, and chemical processes occurring in the water column; and (2) water residence times. The parameter used to describe the residence time of water masses was the local e-flushing time, i.e. the time required for a tracer mass contained within a given station to be reduced by a factor 1/e. High metal concentrations were found in coastal areas (up to 9000 ng dissolved Ni L−1), and steeply decreased with distance from the coast (down to 101 ng dissolved Ni L−1 near the barrier reef) to reach levels similar to those found in remote Pacific waters, suggesting a rapid renewal of waters close to the barrier. Distributions of metals in the lagoon are controlled upstream by land-based emission sources and later chemical processes. Then hydrodynamics constrain metal distributions, as shown by the observed relationship between local e-flushing times and the spatial variability of metal concentrations. In addition, a change in the direction of prevailing winds yielded a decrease of dissolved metal concentrations at the same site by a factor of 2.5 (Cr and Ni) and 2.9 (Zn). It is suggested that the residence time is a key parameter in the control of elemental concentrations in the lagoon waters, as much as land-based emission sources. 相似文献
85.
86.
西菲律宾海沉积物铁族元素地球化学 总被引:5,自引:1,他引:5
本文对取自西菲律宾海区的三个柱状沉积物岩芯的铁族元素地球化学行为进行了系统的研究。从元素的含量及剖面变化、元素的相关性及组合特征,铁族元素与主元素的关系以及元素的赋存状态等方面探讨了物质来源、沉积作用和古气候,并据此进行了地层划分。沉积物有4种来源:海底火山源、生物源、自生源和陆源。海底火山物质提供了较多的铁族元素,相形之下,自生沉积作用较弱。元素地层学研究表明,在全新世温暖期和晚更新世寒冷期铁族元素表现出不同的地球化学行为,尤以Mn和亲生物(Ca)元素对气候的反映灵敏。WP_2孔和WP_(40)孔铁族元素特征相似,与WP_1孔差别较大。 相似文献
87.
Iron-rich concretions are frequently found around plant roots in Tagus estuary (Portugal) where radial delivery of O2 takes place. Salt marsh sediments exhibit cracks that are an additional feature to introduce O2 and other solutes in the upper sediments. Metal concentrations in salt marsh sediments are clearly above the background levels reflecting the anthropogenic sources from a large city with 2.5 million inhabitants, and several industrial centres. In order to evaluate how both oxidised structures influences the redistribution of redox sensitive elements in salt marsh sediments, concretions were collected from roots of Halimione portucaloides below the oxygenated zone. These tubular cylindrical structures were analysed for Fe, Al, Mn, As, and P along 1-cm radial transect in a millimetre scale from the inner part to the adjacent anoxic sediment. In addition, oxidised cracks were analysed for the same spatial resolution, from the sediment–water interface to anoxic layers (2-cm transept). The parallelism between Fe, As, and P concentrations at this microscale is the most noticeable aspect. Iron and As presented very high concentrations in the 4-mm concretions (3.4 mmol g−1 and 3.1 μmol g−1, respectively) and decreased sharply to the host sediment. Oxygen released from roots oxidise the solid sulphides, and the reduced Fe and As are transported towards the root by both diffusion and pore water flow associated with the root water uptake. Subsequently, Fe(III) precipitates and As is retained by sorption and/or coprecipitation. These elements are also enriched in the first 2-mm of oxidised cracks, but in lower concentrations (50% and 30%, respectively). Manganese concentrations in concretions were low (11.8 μmol g−1), indicating that Fe dominates the sediment chemistry. Phosphorus and iron concentrations in the ascorbate fraction were higher in the oxidising surfaces of concretions (10.7 μmol g−1 and 1.6 mmol g−1, respectively) and of cracks (5.1 μmol g−1 and 0.47 mmol g−1). The parallelism of Fe and As distributions includes not only their similar redox chemistries, but also that to phosphate, including control by coprecipitation of the host iron phases. The mechanisms involved in the mobilisation of As and P are however different, whereas As comes from the oxidation of iron sulphides; dissolved P derives from reduction of ferri-hydroxide phases. 相似文献
88.
The current advances in the study of geochemistry and paleo-oceanography of the Co-rich crust are reviewed in this paper. We summarize the study of geochemistry of the Co-rich crust, discuss the diffusion of elements in the Co-rich crust and the exchange with ambient seawater. Besides, we discuss the effect of phosphatization and substrate rocks on the composition of the Co-rich crust. We also introduce the application of stable isotopes (including the stable isotopes of Pb, Nd, and Hf), radioactive isotopes (including the radioactive isotopes of Be, U and Th), and elements (including the major elements, minor elements and rare earth elements) to the study of paleo-oceanography of the Co-rich crust. 相似文献
89.
东太平洋沉积物U的地球化学 总被引:4,自引:0,他引:4
本文对地矿部“海洋四号”科学考察船1987-1989年在东赤道太平洋CC区所取得的27个深海表层沉积样品进行U的地球化学分析,探讨了U在深海沉积中的地球化学行为,结果表明,不同类型沉积的U含量不同,平均值由大至小的次序的含沸石粘土(2.16×10^-6),硅质粘土(1.95×10^-6),硅质软泥(1.65×10^-6),钙质硅质粘土(1.59×10^-6),在同类型沉积中U的分散性较大;U在区域 相似文献
90.
南海西沙西南海域表层沉积物特征 总被引:3,自引:1,他引:3
西沙西南海域表层沉积物样品矿物成分,地球化学,微体古生物分析测试结果表明:沉积物可分为7种类型,沉积环境主要是陆坡,部分为深海平原,海洋生物,海洋化学以及火山物质的沉积起到了积极的作用,陆源物质的影响较小,它们主要来源于北部大陆和南部岛礁等物源区。 相似文献