排序方式： 共有40条查询结果，搜索用时 15 毫秒
31.
秦岭泥盆系成矿带内很多矿床中都产硅质岩,这些硅质岩是泥盆纪沉积柱中的重要组成部分。他们的硅（δ３０Ｓｉ为－０．０５％～－０．０１％）、氧（δ１８Ｏ为１．８６％～２．０９％）同位素组成指示了其海底热液沉积成因方式;微晶石英沉淀的介质温度（８２．１～９４．８℃）高于正常海水温度;随热液沉积演化,硅、氧同位素均向重同位素方向产生动力学分馏;硅质岩层底盘硅化体是热液沉积时的同生蚀变产物,两者硅质同源,硅质岩中的石英脉或团块则是沉积期后硅质岩本身ＳｉＯ２活化产物。 相似文献
32.
Alexandre Grondeau 《GeoJournal》2007,68(1):31-40
Since the 1990s, information and communication technologies clusters (ICT clusters) have been created in developing countries,
especially in Asia, where India is one of the most dynamic countries. Bangalore and Hyderabad are two important examples of
Indian clusters. This article aims to analyze the characteristics of ICT clusters, Indian policies to develop IC technologies,
the formation and emergence of the Bangalore and Hyderabad clusters and their impacts on the population, as well as to show
that ICT development is a strategic issue for India but does not benefit all of its population. 相似文献
33.
The Earth’s core contains light elements and their identification is essential for our understanding of the thermal structure and convection in the core that drives the geodynamo and heat flow from the core to the mantle. Solubilities of Si and O in liquid iron coexisting with (Mg,Fe)SiO3-perovskite, a major constituent of the lower mantle, were investigated at temperatures between 2,320 and 3,040 K at 27 GPa. It was observed that Si dissolved in the liquid iron up to 1.70 wt% at 3,040 K and O dissolved in the liquid iron up to 7.5 wt% at 2,800 K. It was also clearly seen that liquid iron reacts with (Mg,Fe)SiO3-perovskite to form magnesiowüstite and it contains Si and O at 27 GPa and at 2,640 and 3,040 K. The amounts of Si and O in the liquid iron are 1.70 and 2.25 wt% at 3,040 K, respectively. The solubilities of Si and O in liquid iron coexisting with (Mg,Fe)SiO3-perovskite have strong positive temperature dependency. Hence, they can be plausible candidates for the light elements in the core. 相似文献
34.
基础原料铬酸钠的质量直接影响后续系列铬盐产品的品质。电化学氧化技术获得的铬酸钠电解液中可溶性硅在后期系列铬酸盐的制备过程中无法从自体系中去除,会残留在最终产品中进而影响后续铬盐产品的质量。为提高以铬酸钠电解液为原料制备的三氧化二铬产品品质,研究了以铬酸为酸化剂,调节铬酸钠电解液pH去除硅的方法。结果表明,优化反应条件:铬酸钠电解液pH=8,反应温度30℃,反应时间16 h,搅拌速度300 rpm。在此条件下,铬酸钠电解液中二氧化硅浓度降至200 mg/L以下。以除硅后的铬酸钠电解液为原料制备的三氧化二铬纯度达99.43%,满足颜料级三氧化二铬纯度要求(≥99.00%)。 相似文献
35.
The riverine dissolved silicon (DSi) brings environmental information on biogeochemical processes of terrestrial surface, of which the input, transferring, transformation and output are influenced by many factors. Among the weathering of global silicate rocks, 31.53%~64.87% of DSi are intercepted by terrestrial vegetation and only about 12.9% are transferred into rivers. During being transported into ocean, riverine DSi gets impacts from aquatic biological absorption, reverse weathering process and artificial lake effect. The quantity of output is further reduced, which weakens the effect of the oceanic biological pump. According to limited data, the DSi concentration of global rivers has a large variation, ranging from 138 μmol/L to 218μmol/L. It is necessary to quantify contribution rates of influencing factors and establish output models controlled by multiple factors. The δ30Si of riverine DSi ranges from -0.2‰ to 3.4‰. Comparing with the δ30Si of silicate rock, which is about -0.5‰, the fractionation factor is significantly partial to positive from 0.3‰ to 3.9‰. That is because of the occurrence of kinetic fractionation process in river basin including inorganic and organic fractionation. Thus, the key problems, sources and transformation mechanisms of riverine DSi during migration and being transported should be solved in future. 相似文献
36.
E. K. Peinerud 《Environmental Geology》2000,40(1-2):64-72
The biogenic Si concentration in a sediment can be determined as the non-detrital Si concentration by normalization of the
total Si concentration with Al. This procedure is based upon the assumptions that (1) that Al exists predominantly in detrital,
i.e. minerogenic, particles and (2) that biogenic Si (mainly diatom frustules) is the dominating non-detrital Si phase. This
paper focuses on the reasons for the variations of the non-detrital Si concentration in these lake sediments. Data from three
lakes are presented, representing three principally different cases regarding the Si concentration. The processes controlling
the concentrations of detrital and non-detrital Si are discussed.
Received: 10 June 2000 · Accepted: 25 November 2000 相似文献
37.
冷浸-氟硅酸钾法测定矿石中的二氧化硅 总被引：1，自引：0，他引：1
以氢氟酸、硝酸、过氧化氢混合溶剂冷浸过夜的方式分解样品 ,然后在 3mol/ L硝酸溶液加入氯化钾生成氟硅酸钾沉淀 ,经过滤、洗涤后以沸水水解 ,所生成的氢氟酸用氢氧化钠标准溶液滴定 ,来测定二氧化硅的含量。方法操作简便 ,易于掌握。经标样验证 ,结果吻合 相似文献
38.
Si stable isotopes in the Earth's surface: A review 总被引：2，自引：0，他引：2
Silicon (Si) is the second most abundant element on Earth after oxygen. Only few studies have attempted to use stable isotopes of Si as proxies for understanding the Si cycle and its variations in the past. By using three different methods (IRMS, MC–ICP–MS and SIMS), the overall measurements show that the isotopic composition (δ30Si) of terrestrial samples ranges from − 5.7‰ to + 3.4‰. Dissolved Si in rivers and seawater is 30Si-enriched (− 0.8‰ < δ30Si < + 3.4‰) compared to Si in endogeneous rocks (− 1.1‰ < δ30Si < + 0.7‰). This global enrichment is counterbalanced by the Si-bearing phases (biogenic silica, clays, quartz) where Si is, in average, 30Si-depleted (− 5.7‰ < δ30Si < + 2.6‰). These values are the result of fractionation which have been measured or estimated from − 0.3‰ to − 3.8‰. The fractionation is modeled by two types of approaches: the Rayleigh distillation model (closed system) and the steady-state model (open system). These models have been used in the most recent studies to explain the observed δ30Si variations in continental environments and in the sub-Antarctic Ocean. 相似文献
39.
S. Opfergelt D. Cardinal C. Henriet L. Andr B. Delvaux 《Journal of Geochemical Exploration》2006,88(1-3):224
We recently showed that silicon isotopic fractionation in banana (Musa acuminata Colla, cv Grande Naine) was related to phytolith production, and therefore to silica content in plant. The present study focuses on isotopic fractionation between the different plant parts. Silicon isotopic compositions were measured using a Nu plasma multicollector plasma source mass spectrometer (MC–ICP–MS) operating in dry plasma mode. The results are expressed as δ29Si relatively to the NBS28 standard, with an average precision and accuracy of ± 0.08‰ (± 2σ). On mature banana (Musa acuminata Colla, cv Grande Naine) from Cameroon, δ29Si ranged from + 0.13‰ in the petiole to + 0.49‰ in the lamina, yielding to a 0.36‰ change towards heavier isotopic composition in the upper parts of the plant. This strongly accords with results obtained on in vitro banana plantlets cultivated in hydroponics, where the δ29Si increase from pseudostems to lamina is 0.26‰. These preliminary results on in situ banana show a trend of intra-plant fractionation comparable with that of in vitro hydroponics banana plantlets and with previous data obtained on bamboo. 相似文献
40.