极谱法同时测定岩石中的微量铀钍   总被引：2，自引：0，他引：2  

李功顺  朱樱  齐玲  白静梅  郭光珍 《铀矿地质》2009,25(4):240-244

试样经过氧化钠熔融后,用硝酸溶液提取熔块,加入十六烷基三甲基溴化铵（CTMAB）凝聚硅胶,过滤除硅,TBP萃淋树脂分离富集铀钍。在含0．02g／L四丁基碘化铵-4g／L铜铁试剂、pH=5的乙酸-乙酸钠极谱测定体系中同时测定铀钍,铀钍的线性范围为0．001～0．500μg／10mL。本法用于含铀岩石中微量铀钍的同时测定,结果令人满意。  相似文献   

近2ka以来东海内陆架泥质区高分辨率的生物硅记录及其古生产力意义   总被引：2，自引：1，他引：1  

刘升发  石学法  刘焱光  翟滨  吴永华 《沉积学报》2011,29(2):321-327

通过对位于东海内陆架泥质区中部的MZ02孔进行粒度和生物硅分析,AMS14C测年,获得了粒度和生物硅随时间变化的高分辨率曲线.结果表明,近2 ka以来研究区沉积环境稳定,以沿岸流控制的浅海沉积为主;沉积物中生物硅含量<1.5%,属于低含量海区,主要受低硅质骨骼供给量、高溶解作用以及陆源物质冲淡作用的影响.生物硅含量及其...  相似文献   

春季长江口及邻近海域悬浮颗粒态硅的研究   总被引：2，自引：0，他引：2       下载免费PDF全文

曹璐  刘素美  李瑞香 《海洋学报》2011,33(1):83-90

对春季长江口及邻近海域悬浮颗粒态生物硅(PBSi)、成岩硅(LSj)进行了大面调查和围隔培养实验研究,讨论了悬浮颗粒物中PBSi的分布情况及其影响因素.分析表明,PBSi与LSi的含量分别为0.22～4.25和1.75～184μmol/dm<'3>,与世界其他海域相比LSi的含量偏高,PBSi含量则处于中等水平.由于陆...  相似文献   

Particle fluxes in San Pedro Basin, California: A four-year record of sedimentation and physical forcing     

Lisa E. Collins  William BerelsonDouglas E. Hammond  Angela Knapp  Richard SchwartzDoug Capone 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(8):898-914

Moored sediment traps were deployed from January 2004 through December 2007 at depths of 550 and 800 m in San Pedro Basin (SPB), CA (33°33.0′N, 118°26.5′W). Additionally, floating sediment traps were deployed at 100 and 200 m for periods of 12-24 h during spring 2005, fall 2007, and spring 2008. Average annual fluxes of mass, particulate organic carbon (POC), ??¹³C_org, particulate organic nitrogen (PON), ??¹⁵N-PON, biogenic silica (bSiO₂), calcium carbonate (CaCO₃), and detrital material (non-biogenic) were coupled with climate records and used to examine sedimentation patterns, vertical flux variability, and organic matter sources to this coastal region. Annual average flux values were determined by binning data by month and averaging the monthly averages. The average annual fluxes to 550 m were 516±42 mg/m² d for mass (sdom of the monthly averages, n=117), 3.18±0.26 mmol C/m² d for POC (n=111), 0.70±0.05 mmol/m² d for CaCO₃ (n=110), 1.31±0.21 mmol/m² d for bSiO₂ (n=115), and 0.35±0.03 mmol/m² d for PON (n=111). Fluxes to 800 and to 550 m were similar, within 10%. Annual average values of ??¹³C_org at 550 m were −21.8±0.2‰ (n=108), and ??¹⁵N averages were 8.9±0.2‰ (n=95). The timing of both high and low flux particle collection was synchronous between the two traps. Given the frequency of trap cup rotation (4-11 days), this argues for particle settling rates ≥83 m/d for both high and low flux periods. The moored traps were deployed over one of the wettest (2004-2005, 74.6 cm rainfall) and driest (2006-2007, 6.6 cm) rain years on record. There was poor correlation (Pearson's correlation coefficient, 95% confidence interval) of detrital mass flux with: C_org/N ratio (r=0.10, p=0.16); ??¹⁵N (r=−0.19, p=0.02); and rainfall (r=0.5, p=0.43), suggesting that runoff does not immediately cause increases in particle fluxes 15 km offshore. ??¹³C_org values suggest that most POC falling to the basin floor is marine derived. Coherence between satellite-derived chlorophyll a records from the trap location (±9 km² resolution) and SST data indicates that productivity and export occurs within a few days of upwelling and both of these parameters are reasonable predictors of POC export, with a time lag of a few days to 2 weeks (with no time lag—SeaWiFS chlorophyll a and POC flux, r=0.25, p=0.0014; chlorophyll a and bSiO₂ flux, r=0.28, p=0.0002).  相似文献   

四川盆地碳酸盐岩中硅质特征及其对储层的影响   总被引：1，自引：0，他引：1       下载免费PDF全文

莫静  王兴志  谢林  何施雨  梁静  李加利  敖梅  何川 《地质找矿论丛》2013,28(3):419-423

四川盆地碳酸盐岩储层为我国主要海相储层之一。通过分析四川盆地碳酸盐岩中硅质的宏观、微观特征,提出硅质以互层、混积、充填、交代的形式存在于碳酸盐岩中。互层硅质、充填硅质和交代硅质中二氧化硅来源以火山喷发为主,但后期沉积机制不同;混积硅质中二氧化硅来源于陆源碎屑,对物源方向具有一定的指向意义,沉积机制为陆源混积。互层硅质、充填硅质、交代硅质对储层形成具有双重意义,混积硅质对储层形成起严重破坏性作用。  相似文献   

Estimating the contribution of the authigenic mineral component to the long-term reactive silica accumulation on the western shelf of the Mississippi River Delta     

Massimo Presti  Panagiotis Michalopoulos 《Continental Shelf Research》2008

Previous studies have shown how biogenic silica particles undergo conversion to aluminosilicate phases in large tropical deltaic systems, thus affecting the world ocean budget of major seawater cations. This study tackles the important question of the silica budget in the coastal zone of the Mississippi River Delta, providing evidence for the role of biogenic silica diagenesis in this subtropical system from direct examination of individual diatom particles, sediment leachates and pore-water composition. The estimated reactive silica stored in the study area (5990 km²) is based on operational leaches that account for altered biogenic silica particles and other authigenic aluminosilicate phases in addition to fresh biogenic silica. Early diagenesis of silica in the delta front occurs mainly where more siliceous material is deposited. An inner-shelf area, where hypoxic conditions are found, significantly contributes to the formation of authigenic products of Si alteration. Data suggest that the limiting factor of silica alteration processes is the availability of detrital phases such as Al and Fe. The estimated total reactive silica accumulation in the study area is 1.45×10¹⁰ mol Si year⁻¹, representing ∼2.2% of the long-term bulk sediment accumulation. On the basis of a conservative appraisal, the authigenic mineral components account for ∼40% of the long-term reactive silica storage. This study shows that non-tropical deltaic systems are significantly more important sinks of silica than previously thought and that, where conditions are favourable, a consistent portion of reactive silica not leaving the shelf is stored within the delta in the form of authigenic components.  相似文献   

Paleolimnological evidence of the response of the central Canadian treeline zone to radiative forcing and hemispheric patterns of temperature change over the past 2000 years     

Glen M. MacDonald  David F. Porinchu  Nicolas Rolland  Konstantine V. Kremenetsky  Darrell S. Kaufman 《Journal of Paleolimnology》2009,41(1):129-141

Instrumental climate records from the central Canadian treeline zone display a pattern of variation similar to general Northern Hemisphere temperature trends. To examine whether this general correspondence extends back beyond the instrumental record, we obtained a sediment core from Lake S41, a small lake in the Northwest Territories of Canada at 63°43.11′ N, 109°19.07′ W. A radiocarbon-based chronology was developed for the core. The sediments were analyzed for organic-matter content by loss-on-ignition (LOI), biogenic-silica content (BSi), and chironomid community composition to reconstruct July air temperature and summer water temperature. The paleolimnological records were compared with records of atmospheric CO₂ concentration, solar variability, and hemispheric temperature variations over the past 2000 years. The results of the analyses suggest that widely-documented long-term variations in Northern Hemisphere temperature associated with radiative forcing, namely the cooling following the medieval period during the Little Ice Age (LIA), and twentieth century warming, are represented in the central Canadian treeline zone. There is also evidence of a brief episode of warming during the eighteenth century. As evidenced by LOI and BSi, the twentieth century warming is typified by increased lake productivity relative to the LIA. Depending upon the measure, the increased productivity of the twentieth century nearly equals or exceeds that of any other period in the past 2000 years. In contrast, the rate of chironomid head capsule accumulation decreased and remained low during the twentieth century. Although the chironomid-inferred temperature reconstructions indicate cooling during the LIA, they present no evidence of greatly increased temperatures during the twentieth century. Warming during the twentieth century might have enhanced lake stratification, and the response of the chironomid fauna to warming was attenuated by decreased oxygen and lower temperatures in the hypolimnion of the more stratification-prone lake.

Glen M. MacDonaldEmail:

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SiO₂ precipitation in olivine: ATEM investigation of two dunites annealed at 300 MPa in hydrous conditions     

Paul Raterron  Prame Chopra  Jean-Claude Doukhan 《Earth and Planetary Science Letters》2000,180(3-4):415-423

Two natural dunites were annealed at pressure P=300 MPa, temperature T=1373, 1473 and 1573 K, and fO₂ within the stability field of olivine. The starting materials contained small amounts of hydroxyls in the form of minor phases of hydrated minerals, which released an aqueous phase during the experiments. A detailed analytical transmission electron microscopy (ATEM) investigation of these materials revealed that small quantities of two types of silica-rich glass formed during heat treatment. The first type of glass, found at triple junctions as rare partially crystallized glass pockets, results from melting dehydration reactions involving the hydrous phases. The second type of glass is found as pure silica precipitates (0.1–0.5 μm in size, for a total of a few 0.1 vol%) within the olivine grains of specimens heated to ≥1473 K. From considerations of the kinetics of the precipitation at 1473 K, we interpret this silica precipitation as resulting from the condensation of olivine metallic vacancies promoted by increasing fluid fugacities during the runs. Our observations, thus, demonstrate that metastable silica can precipitate in olivine from dunites experiencing rapid changes in their thermodynamical environment.  相似文献   

海洋沉积物32 Si测年方法研究     

詹晓青  李超  贾磊  张金鹏  刘广山 《海洋学报》2019,41(2):63-74

天然32Si是宇宙射线成因的，随着降水进入湖泊或海洋，被硅质生物摄取后最终存在于生物硅中。32Si来源单一，生产速率相对恒定，半衰期为150 a，可测年的时间尺度为100~1 000 a，是该时间尺度最合适的测年核素，填补了百年到千年时间尺度测年方法的空白。本文建立了海洋沉积物32Si的测量方法，主要步骤为:（1）样品前处理；（2）生物硅的分离与纯化；（3）生物硅样品中磷的分离与纯化；（4）32P的制样与β计数测量。全程通过硅钼蓝和磷钼蓝分光光度法监测实验过程硅和磷的损失情况，对南沙海域采集的沉积物岩心进行研究，得到南沙海域沉积物岩心32Si的平均活度为16.60 mBq/kg，范围值为8.39~33.34 mBq/kg；32Si在SiO₂中的平均比活度为0.356 Bq/kg，32Si的核素丰度平均值为1.29×10-16（32Si/SiO₂）；根据岩心32Si活度估算得深水区（水深1 335~1 537 m）和浅水区（121~141 m）岩心的沉积速率分别为0.106 cm/a、0.191 cm/a；根据32Si活度计算32Si的平均沉降通量为2.14×10-6 Bq/（cm2·a），与参考文献的结果较为吻合。  相似文献   

Precise and Accurate Doping of Nanoporous Silica Gel for the Synthesis of Trace Element Microanalytical Reference Materials          下载免费PDF全文

William O. Nachlas 《Geostandards and Geoanalytical Research》2016,40(4):505-516

This study presents an experimental procedure to fabricate high‐purity silica glass containing a selected element at a specified mass fraction. The procedure was used to prepare glasses doped with trace‐level mass fractions of Ti with the goal of improving analytical confidence when measuring trace elements in quartz. Systematic tests were performed to determine the ideal conditions and procedures for doping nanoporous silica gel with the highest efficiency of dopant recovery. Silica gel was cleaned in concentrated HCl, immersed in a non‐polar doping medium at a controlled pH and doped with precise quantities of ICP‐MS standard solution. Using liquids composed of longer chain molecules as the doping medium diminishes recovery, suggesting that large molecules could obstruct nanopores to inhibit capillary uptake of the dopant. A control experiment using crystalline quartz reinforced the effectiveness of nanoporous silica gel for doping with trace‐level precision. Layered aggregates of silica gel doped with different Ti mass fractions were hot‐pressed to create multi‐layered reference materials that were analysed with multiple techniques at a variety of spatial scales. Analyses at the intra‐grain scale (cathodoluminescence scanning electron microscopy, electron probe microanalysis), at the single grain scale (SIMS), at the sample layer scale (EPMA, laser ablation‐ICP‐MS) and at the bulk scale (ICP‐OES) demonstrated acceptable homogeneity at sample volumes characteristic of most microanalysis techniques and show that nanoporous silica gel holds promise as a highly retentive doping substrate for preparing reference materials for laser‐, electron‐ and ion‐beam microanalysis.  相似文献