The Chemistry of Niobium Mineralisation at Bayan Obo, Inner Mongolia, China: Constraints on the Hydrothermal Precipitation and Alteration of Nb-Minerals   总被引：1，自引：0，他引：1  

Martin SMITH  John SPRATT 《地质学报》2012,86(5):700-722

As well as world class Fe and REE resources the Bayan Obo mineral deposits also hosts significant niobium resources(estimated as 2.2 Mt Nb with an average grade of 0.13 wt% Nb).Niobium in this study is primarily hosted in aeschynite-(Ce) and(Nd),but with subsidiary amounts of pyrochlore,fergusonite-(Ce),fersmite and columbite.Here we report on the paragenetic and textural setting of aeschynite,pyrochlore and fergusonite in the main ore bodies and in a carbonatite dyke.Niobium in a carbonatite sample is hosted in a phase tentatively(due to significant Ca,Mn and Ti contents) identified as fergusonite-(Ce).Aeschynite occurs overgrowing foliation in banded ores,in fractures and vugs in aegirine-rich rocks and in calcite veins.The composition in all settings is similar,but some examples in banded ores develop significant zonation in Y,Th and the REE,inferred to relate to buffering of halogen acid species to low levels by dissolution and fluoritisation of calcite,and the preferential precipitation of LREE from solution due to lower mineral solubility products compared to the HREE.Although lower in total concentration the ratios of REE in pyrochlore are similar to those of aeschynite and suggest the same metal source.The crystallisation of pyrochlore probably relates to growth in paragenetic settings where carbonates had already been eliminated and hence the buffering of F-species activities in the hydrothermal fluid was reduced.Both aeschynite and pyrochlore show evidence of alteration.Primary alteration of aeschynite resulted in leaching of A-site cations(Ca,REE,Th) and Nb,addition of Fe,and ultimately replacement by Ba-Ti phases(baotite and bafertisite).Secondary,metamictisation enhanced,possibly supergene alteration of pyrochlore resulted in hydration,leaching of A-site cations leading to the development of lattice vacancies and increases in Si.The presence of hydrothermal Nb resources at Bayan Obo suggests there may be potential for further Nb discoveries in the area,whilst the trends in element mobility during alteration have significant implications for the utility of A-B oxides as components of materials for immobilisation of radionuclides.  相似文献   

浙江秀山海泥营养物质对环境生物抗氧化性能的影响   总被引：1，自引：0，他引：1       下载免费PDF全文

罗红宇  吴辉辉  解延海  桑卫国  张骏 《海洋与湖沼》2008,39(1):8-13

将浙江秀山海泥样品通过水浸提、离心沉降处理得到水溶相体系海泥提取液,按照20%(体积分数)加入到抗氧化性能评价体系中,采用BCS-Trolox法测定体系的总抗氧化性能,研究了温度、pH和时间对水溶相体系抗氧化性能的影响;分析了含水量为50%的浙江秀山海泥的营养成分,测定了生长于秀山滩涂海泥的菲律宾蛤仔和泥螺肌肉的SOD和GSH-Px的活力。结果表明,与已经开发成保健或泥疗产品的对照泥样相比,秀山海泥富含抗氧化活性营养成分V_A、V_E、V_C、Ge、Fe、Mg、Zn、Sr、Ca,总蛋白酶活性较强;该水溶相体系的抗氧化性能显著,20%的海泥提取液的抗氧化性能与(3.68±0.25)μmol/L的Trolox相当;温度对水溶相体系的抗氧化性能影响显著,pH、时间没有显著影响,因此确定最佳的水溶相体系制备条件为温度60℃、pH 5.6、时间10min;与对照组相比,秀山滩涂海泥能够激活菲律宾蛤仔和泥螺肌肉的SOD、GSH-Px的活性,提高机体的抗氧化性能。  相似文献   

普洱二台坡超大型化探异常找矿前景     

谢岿锐  李开全  余乔富 《云南地质》2008,27(4):469-476

测区共分析15个元素,除Au外,其余14个元素都产生异常。对异常作因子分析、R型聚类分析,结合物探、遥感、地质、1：20万区域化探资料综合研究,提出了在此异常区寻找大型矿床的可能性。  相似文献   

Submarine groundwater discharge enhances primary productivity in the Yellow Sea,China:Insight from the separation of fresh and recirculated components     

Jianan Liu  Jinzhou Du  Xueqing Yu 《地学前缘(英文版)》2021,12(6):76-89

Submarine groundwater discharge(SGD)is being increasingly recognized as a significant source of nutri-ent into coastal waters,and generally comprises two components:submarine fresh groundwater dis-charge(SFGD)and recirculated saline groundwater discharge(RSGD).The separate evaluation of SFGD and RSGD is extremely limited as compared to the conventional estimation of total SGD and associated nutrient fluxes,especially in marginal-scale regions.In this study,new high-resolution radium isotopes data in seawater and coastal groundwater enabled an estimation of SGD flux in a typical marginal sea of the Yellow Sea.By establishing 226Ra and 228Ra mass balance models,we obtained the SGD-derived radium fluxes,and then estimated the SFGD and RSGD fluxes through a two end-member model.The results showed that the total SGD flux into the Yellow Sea was equivalent to approximately 6.6 times the total freshwater discharge of surrounding rivers,and the SFGD flux accounted for only 5.2％-8.8％of the total SGD.Considering the nutrient concentrations in coastal fresh and saline groundwater,we obtained the dissolved inorganic nutrient fluxes(mmol m-2 yr-1)to be 52-353 for nitrogen(DIN),0.21-1.4 for phosphorus(DIP),34-226 for silicon(DSi)via SFGD,and 69-262 for DIN,1.0-3.9 for DIP,70-368 for DSi via RSGD,with the sum of nutrient fluxes equaling to(1.8-9.3)-fold,(1.3-5.6)-fold and(2.0-9.5)-fold of the riverine inputs.Compared to the conventional estimation of the total SGD flux,the nutrient fluxes derived from the separation of SFGD and RSGD were(1.6-2.1),(1.6-1.8)and(4.0-4.9)times lower for DIN,DIP and DSi,respectively,indicating that the estimates by separating SFGD and RSGD could be conservative and representative results of the Yellow Sea.Furthermore,we suggested that SGD played an important role in nutrient sources among all the traditional nutrient inputs sources,providing 15％-48％,33％-68％and 14％-43％of the total DIN,DIP and DSi input fluxes into the Yellow Sea,and the high nutrient stoichiometric ratios(i.e.,DIN/DIP)in SGD probably contributed to the increasing ratios in the Yellow Sea.In addition delivering large amounts of nutrient into the Yellow Sea,SGD would create primary productivity of 10-49,1.6-6.8 and 8.8-42 g C m-2 yr-1 based on N,P and Si,which were equivalent to 5.2％-27％,0.9％-3.7％and 4.7％-23％of the total primary productivity,respectively.In par-ticular,the SFGD-derived DIN flux can be converted to primary productivity of 4.2-28 g C m-2 yr-1 thus demonstrating the disproportionately large role of SFGD in ecological environment of the Yellow Sea rel-ative to its flux.Therefore,we conclude that SGD,particularly SFGD,plays an important role as a nutrient source for the Yellow Sea,and not only affects nutrient budgets and structures but also enhances the pri-mary productivity.  相似文献   

Characterization of nutrients in the atmospheric wet and dry deposition observed at the two monitoring sites over Yellow Sea and East China Sea   总被引：5，自引：0，他引：5  

Guosen Zhang  Jing Zhang  Sumei Liu 《Journal of Atmospheric Chemistry》2007,57(1):41-57

To investigate the atmospheric deposition of nutrients into the coastal and shelf regions of the northwest Pacific Ocean, observation sites were established upon Qianliyan Island (within the Yellow Sea) and the Shengsi Archipelago (within the East China Sea), respectively. Nutrient concentrations, including , were determined in both aerosols and rainwater samples. The analytical results contain clear seasonal signatures, with high values during the dry season and low values during the rainy season. Similar trends are observed for deposition fluxes. The amount of wet deposition is greater than that of dry deposition for the studied nutrient species. The influence of meteorological factors such as rainfall means that samples from Qianliyan Island record higher nutrient values than those from Shengsi. Along with riverine inputs, atmospheric deposition plays an important role in determining the biogeochemistry of nutrient species in coastal and shelf oceans. An erratum to this article can be found at  相似文献   

Significant variations in the productivity of green macroalgae in a mesotidal estuary: implications to the nutrient loading of the system and the adjacent coastal area     

Martins I  Lopes RJ  Lillebø AI  Neto JM  Pardal MA  Ferreira JG  Marques JC 《Marine pollution bulletin》2007,54(6):678-690

A spatially dynamic model for the productivity of spores and adults of green macroalgae (Enteromorpha sp.) was developed for a mesotidal estuary (Mondego estuary, Portugal). Many of the algal processes and parameters included in the model were experimentally obtained. Model predictions were compared to a real time series (1993-1997) of macroalgal biomass variation and the two sets show a good agreement (ANOVA, P<0.001). Results suggest that algal growth is highly sensitive to small changes in depth and exhibits different patterns of variation in different seasons. On a yearly basis, global calculations for the south channel of the estuary (137 ha) suggest that during bloom years, macroalgal biomass may reach about 21,205 ton DW compared to 240 ton DW in regular years. On a seasonal basis, the difference may be even more significant. The consequences of such variations on the nitrogen and phosphorus loading of the system and the adjacent coastal area are discussed.  相似文献   

Evaluation of anthropogenic carbon in the Nordic Seas using observed relationships of N, P and C versus CFCs     

Sara Jutterström  Emil Jeansson  Leif G. Anderson  E. Peter Jones  James H. Swift 《Progress in Oceanography》2008,78(1):78-84

Several methods to compute the anthropogenic component of total dissolved inorganic carbon () in the ocean have been reported, all in some way deducing (a) the effect by the natural processes, and (b) the background concentration in the pre-industrial scenario. In this work we present a method of calculating using nutrient and CFC data, which takes advantage of the linear relationships found between nitrate (N), phosphate (P) and CFC-11 in the Nordic Seas sub-surface waters. The basis of the method is that older water has lower CFC-11 concentration and also has been exposed to more sinking organic matter that has decayed, resulting in the slopes of P versus CFC-11 and N versus CFC-11 being close to the classic Redfield ratio of 1:16. Combining this with the slope in total alkalinity (A_T) versus CFC-11 to correct for the dissolution of metal carbonates gives us the possibility to deduce the concentration of anthropogenic C_T in the Nordic Seas. This further allowed us to compute the inventory of anthropogenic C_T below 250 m in the Nordic Seas in spring 2002, to ∼1.2 Gt C.  相似文献   

Converting tropical rainforest to forest plantation in sabah,malaysia. Part II. Effects on nutrient dynamics and net losses in streamwater     

A. Malmer  H. Grip 《水文研究》1994,8(3):195-209

Streamwater chemistry was monitored for five years in six streams in a paired catchment experiment in Mendolong, Sabah, Malaysia, comparing the effects of different ways to establish forest plantations with Acacia mangium. At the start of the monitoring in 1985 three catchments were covered with selectively logged rain forest (W4-W6) and three with secondary vegetation after forest fire (W1-W3). The treatments were: (1) clearing of secondary vegetation, burning and planting (W1 and W2); (2) clear-felling, crawler tractor extraction, burning and planting (W5); and (3) clear-felling, manual extraction, no burning and planting (W4). W3 and W6, with no treatment, were monitored as control catchments. Reference monitoring at all streams was for two years and was followed by treatments which lasted for nine months before the full establishment of a new vegetation cover. This paper covers monitoring for a further 2.5 years. The soil types of the catchments were Orthic Acrisol in W3, Gleyic Podsol in W6 and a mix of both soil types in the other catchments. The effect of treatments on streamwater chemistry was clear at both base- and stormflows. Concentrations of major plant nutrients (N, P and K.) became positively correlated to streamflow during treatments. The response of leaching from slash at clear-felling was fast and larger from the clear-felling residues (W4 and W5) than the cleared secondary vegetation (W1 and W2). The intense response to burning was more marked. The stormflow period mean nutrient concentrations were approximately 10-fold for N and K and 10-100 fold for P after burning compared with baseflow mean concentrations over the same period. Significant differences in baseflow concentrations in treated streams generally lasted one year for most elements, but elevated concentrations were still detectable after three years. The first large pulse of leaching was related to mineralization after tree-felling and particularly burning. The longer lasting elevated concentrations in baseflow were associated with the loss of weathering products. The amounts of nutrients lost, calculated by regression analysis as the effect of treatment compared with control, were found to be higher with the degree of vegetation killed and with increased soil disturbance. Consequently, normal forestry practices, with crawler tractor extraction and burning before planting, created the largest leaching losses. The total calculated effect of losses in total N, P and K were (i) W1 + W2 0.5, 1.8, 83.9; (ii) W4 0.8, 0.8, 105.6; and (iii) W5 1.3, 1.3, 189.4 kg ha^?1 for the period of 33 months during and after treatment. With normal forestry practice using crawler tractors and with burning before planting (W5), the treatment-induced loss of K was equivalent to 86% of the content of easily decomposed parts of the biomass (leaves, twigs, fine roots and ground vegetation) of the old forest, or larger than K removed by harvest. Exhaustion effects of lowered leaching after repeated burning (forest fire and pre-planting fire) was observed for several elements, indicating possible nutrient deficiencies.  相似文献   

云南哀牢山常绿阔叶林土壤渗漏水养分研究   总被引：4，自引：0，他引：4  

甘健民  薛敬意  谢寿昌 《地理科学》1997,(3)

在云南哀牢山生态站对中山湿性常绿阔叶林进行定位研究，根据１９９１～１９９３年的观测资料，对土层１０，２５，４５，６５ｃｍ土壤渗漏水养分浓度、养分迁移及养分滞留的变化进行了分析和讨论。  相似文献   

条纹斑竹鲨肌肉的营养成分   总被引：9，自引：1，他引：9  

杨萍  章超桦 《海洋科学》2002,26(2):65-68

对条纹斑竹鲨肌肉营养成分进行分析 ,结果表明 :条纹斑竹鲨肌肉的粗蛋白含量为21.7% (干基为70.8% ) ;蛋白质营养价高 ,第一限制氨基酸为色氨酸 ,氨基酸价为88 ;无机质含量丰富 ,特别是Mg,Fe,Zn ,Se等微量元素 ,尤其是Se含量达1.44×10-6 (干基为6.89×10-6) ,是含Se很高的水产品  相似文献