Selective dissolution of late cretaceous and earliest tertiary calcareous nannofossils: Experimental evidence     

H.R. Thierstein 《Cretaceous Research》1980,1(2):165-176

The effects of carbonate dissolution on the taxonomic composition of ancient nannofossil assemblages were investigated by deploying them on a deep mooring at depths of 1039 m–5500 m for 117 days in the Sargasso Sea. The relative proportions of only a few taxa change significantly with increasing dissolution: Cruciplacolithus primus is by far the most susceptible and Micula staurophora by far the most resistant species. The average dissolution indices calculated for the deployed assemblages closely follow the gradients of other dissolution indicators in the North Atlantic.  相似文献   

利用磁团聚简化铁矿石磁选流程     

张予钊 《江苏地质》1998,22(4)

论述了含假象赤铁矿铁矿石磁选工艺流程的改进。利用磁团聚工艺省去了赤铁矿回收段单独的粗精矿再磨设备及后继的中磁场精选作业。节省了设备投资费用及生产成本,而且铁实收率较之传统工艺有所提高。对类似该矿石性质的氧化带混合铁矿石磁选流程的制定及现场流程改造有启迪意义。  相似文献   

商丹地区产铀伟晶岩成因讨论   总被引：2，自引：0，他引：2  

冯明月 《铀矿地质》1996,12(1):30-36

本文阐述了商丹地区产铀伟晶岩、片麻状花岗闪长岩、秦岭群变质岩的岩石化学成分、铷锶等微量元素含量和锶同位素初始比、副矿物组合类型等方面的特点，通过岩体内不产铀伟晶岩、岩体外产铀伟晶岩的对比和钐钕同位素示踪方法研究，提出产铀伟晶岩脉群不是片麻状花岗闪长岩体（Ｔ（Ｄｍ）为１０Ｍａ）晚期分异的残浆结晶产物，而是秦岭群变质岩选择性熔融产生的花岗质熔浆在相对封闭条件下缓慢结晶而成。  相似文献   

砂土液化中颗粒分析试验试剂用量标准的研究     

崔桂梅  朱建亚  王振强  康瑞清 《华北地震科学》2003,21(2):54-58

采用不同剂量的六偏磷酸钠试剂，对GB／T50123—1999《土工试验方法标准》中的密度计法(甲种密度计)做颗粒分析试验的结果进行对比分析^[1]，由此对4％六偏磷酸钠溶液用量与分析结果的关系以及10m1的标准用量进行验证与探讨。  相似文献   

Trends of grain sizes on gravel bars in the Rio Chagres, Panama     

Francis Rengers  Ellen Wohl 《Geomorphology》2007,83(3-4):282-293

We examined the trends of grain sizes along the upper 414 km² of the mountainous Rio Chagres drainage basin in Panama. Gravel bars were sampled along 40 km of the Rio Chagres and five major tributary streams using a transect pebble count of median diameter, lithology, and clast rounding. Although previous investigators have found that downstream fining can be obscured by inputs of colluvial sediment and other local controls in mountain drainages, we decided to examine the trends of grain sizes along a tropical mountain river where rapid weathering and high capability of transport might be capable of overriding the input effects of colluvium. Specifically, we tested the hypotheses that downstream fining would be present as a result of selective sorting, and that weak felsic particles would decrease in size preferentially to strong mafic particles because of abrasion. Statistical analyses reveal a weak downstream decrease of sediment size on gravel bars along the study reach of the Rio Chagres, with a Sternberg diminution coefficient (α) for felsic and mafic grains of − 0.013 and − 0.017, respectively. Felsic clasts have thicker weathering rinds and become rounded downstream faster than mafic particles, but tumbling-mill tests of abrasion show no significant differences in rate of mass loss in relation to lithology, and downstream decreases in grain size are similar between lithologies. Dividing the study reach into six sub-reaches bounded by major tributary junctions, we further tested the hypothesis that downstream trends in fining might be obscured at the basin scale by sediment input from tributaries, but that trends in grain sizes might be more visible at the reach scale between tributaries. We did not find any consistent trends in grain size between tributaries. Stream width appears to assert a local control on grain size; coarse particles are associated with narrow channel reaches, whereas smaller particles are associated with wide channel reaches.  相似文献   

Origin and formation pathways of kerogen-like organic matter in recent sediments off the Danube delta (northwestern Black Sea)   总被引：1，自引：0，他引：1  

Anouk Garcette-Lepecq  Sylvie Derenne  Claude Largeau  Ioanna Bouloubassi  Alain Saliot 《Organic Geochemistry》2000,31(12):204

The chemical structure, source(s), and formation pathway(s) of kerogen-like organic matter (KL) were investigated in recent sediments from the northwestern Black Sea, off the Danube delta. Three sections from a sediment core collected at the mouth of the Sulina branch of the delta, under an oxic water column, were examined: S₀ (0–0.5 cm bsf), S₁₀ (10–13 cm bsf), and S₂₀ (20–25 cm bsf). The bulk geochemical features of these sediments (total organic carbon, organic C/N atomic ratio, δ¹³C_org) were determined. Thereafter, KL was isolated from the samples, as the insoluble residue obtained after HF/HCl treatment. KL chemical composition was investigated via spectroscopic (FTIR, solid state ¹³C and ¹⁵N NMR) and pyrolytic (Curie point pyrolysis–gas chromatography–mass spectrometry) methods, and the morphological features were examined by scanning and transmission electron microscopy. Similar morphological features and chemical composition were observed for the three KLs and they suggested that the selective preservation of land-plant derived material as well as of resistant aliphatic biomacromolecules (probably derived from cell walls of freshwater microalgae) was the main process involved in KL formation. Besides, some melanoidin-type macromolecules (formed via the degradation-recondensation of products mainly derived from proteinaceous material) and/or some encapsulated proteins also contributed to the KL chemical structure.  相似文献   

多功能高分子固沙剂流动沙丘固定试验研究   总被引：4，自引：1，他引：3  

张松林  田侠  赵首彩  董庆士  张锦春 《中国沙漠》2005,25(3):450-452

试验选择在甘肃省武威市民勤县绿洲外缘与沙漠交接地带,应用多功能高分子固沙剂进行流动沙丘固定试验研究。结果显示,在试验区斜坡下部,除草试验区比对照区结皮厚度增大81.25%,未除草试验区结皮比对照厚度增加32.25%,固沙结皮区比无结皮区抗风蚀,至今固沙结皮依然存在;未除草有结皮时固沙试验区0~80cm各层平均含水率均比对照区高,其中土层平均含水率比对照区高76.27%。实验证明施用试剂不仅固沙效果非常明显,而且在不除草时对土壤水分有很好的保持效果。  相似文献   

化学蒸气发生-无色散原子荧光光谱法测定地质样品中微量和痕量金   总被引：1，自引：1，他引：0  

马建学  路学东  许卓 《岩矿测试》2011,30(3):343-348

试样用王水分解,采用特定的金化学发生增敏试剂使金在硼氢化物-酸体系中产生挥发物质,将其导入原子荧光光谱检测系统,检测金的原子荧光信号。通过对仪器工作参数和化学蒸气发生参数的优化,使金的可检测信号同比提高20倍以上,同时降低共存离子对金的化学蒸气发生的干扰。对微量和痕量金的测定方法具有灵敏度高、检出限低、基体干扰少等优点。方法检出限为0.23 ng/g,准确度(ΔlgC,n=12)为-0.004~0.02,精密度(RSD,n=12)为2.62%~8.79%。经国家一级标准物质分析验证,测定值与标准值相符。  相似文献   

Phytopigments and fatty acids in the gut of the deposit-feeding heart urchin Echinocardium cordatum in the southern North Sea: Selective feeding and its contribution to the benthic carbon budget     

Arjen R. Boon  Gerard C.A. Duineveld 《Journal of Sea Research》2012,67(1):77-84

As part of a broader study on benthic-pelagic coupling in the southern North Sea, specimens of the common heart urchin Echinocardium cordatum were sampled for analyses on phytopigments and fatty acids in their guts. Results were interpreted in the context of feeding and ecological functioning of the heart urchins in the benthic system. Ingestion selection factors for both component groups were relatively high, 5 to 9 for chlorophyll a and 9 to 130 for total fatty acids. The data point to at least partially different sources of the pigments and of the fatty acids. Next to algal detritus, small infauna relatively rich in fatty acids might be preferentially co-ingested with the detritus. Due to digestive breakdown and absorption, the concentrations of pigments and fatty acids were importantly decreased, indicating a rather high digestion efficiency for this subsurface deposit feeder, up to 80%. The results indicate that E. cordatum increases its energy acquisition by strong selectivity and a high digestive efficiency. Optimal foraging is likely to apply on deposit-feeding invertebrates in relatively food-rich coastal environments as much as it does in the food-poor deep-sea environment. Using chlorophyll a as a proxy for carbon, the contribution of the urchin population to the momentary benthic carbon budget was calculated at 7% to 42%.  相似文献   

艾斯卡试剂熔矿、动态树脂交换——等离子体质谱法测定土壤样品中的痕量碘   总被引：1，自引：0，他引：1  

吴赫  王龙山  张艳  李雪莹 《陕西地质》2009,27(2):97-102

研究了电感耦合等离子体质谱法（ICP—MS）测定土壤样品中微量碘的可行性,对测定碘的条件作了部分改进及进一步优化。样品经艾斯卡试剂分解,热水提取,阳离子交换树脂动态分离溶液中大量的钠、铁、锌等阳离子,干过滤部分溶液,采用电感耦合等离体子质谱法（ICP—MS）直接测定溶液中的碘。本方法用国家标准物质进行验证,测定结果和标准值吻合。并用该法顺利完成了陕西省宝鸡地区多目标区域地球化学调查样品中碘的测定。  相似文献