Seawater-like trace element signatures (REE + Y) of Eoarchaean chemical sedimentary rocks from southern West Greenland,and their corruption during high-grade metamorphism   总被引：2，自引：0，他引：2  

C. R. L. Friend  A. P. Nutman  V. C. Bennett  M. D. Norman 《Contributions to Mineralogy and Petrology》2008,155(2):229-246

Modern chemical sediments display a distinctive rare earth element + yttrium (REE + Y) pattern involving depleted LREE, positive La/La*_SN, Eu/Eu*_SN, and Y_SN anomalies (SN = shale normalised) that is related to precipitation from circumneutral to high pH waters with solution complexation of the REEs dominated by carbonate ions. This is often interpreted as reflecting precipitation from surface waters (usually marine). The oldest broadly accepted chemical sediments are c. 3,700 Ma amphibolite facies banded iron-formation (BIF) units in the Isua supracrustal belt, Greenland. Isua BIFs, including the BIF international reference material IF-G are generally considered to be seawater precipitates, and display these REE + Y patterns (Bolhar et al. in Earth Planet Sci Lett 222:43–60, 2004). Greenland Eoarchaean BIF metamorphosed up to granulite facies from several localities in the vicinity of Akilia (island), display REE + Y patterns identical to Isua BIF, consistent with an origin by chemical sedimentation from seawater and a paucity of clastic input. Furthermore, the much-debated magnetite-bearing siliceous unit of “earliest life” rocks (sample G91/26) from Akilia has the same REE + Y pattern. This suggests that sample G91/26 is also a chemical sediment, contrary to previous assertions (Bolhar et al. in Earth Planet Sci Lett 222:43–60, 2004), and including suggestions that the Akilia unit containing G91/26 consists entirely of silica-penetrated, metasomatised, mafic rock (Fedo and Whitehouse 2002a). Integration of our trace element data with those of Bolhar et al. (Earth Planet Sci Lett 222:43–60, 2004) demonstrates that Eoarchaean siliceous rocks in Greenland, with ages from 3.6 to 3.85 Ga, have diverse trace element signatures. There are now geographically-dispersed, widespread examples with Isua BIF-like REE + Y signatures, that are interpreted as chemically unaltered, albeit metamorphosed, chemical sediments. Other samples retain remnants of LREE depletion but are beginning to lose the distinct La, Eu and Y positive anomalies and are interpreted as metasomatised chemical sediments. Finally there are some siliceous samples with completely different trace element patterns that are interpreted as rocks of non-sedimentary origin, and include metasomatised mafic rocks. The positive La/La*_SN, Eu/Eu*_SN and Y_SN anomalies found in Isua BIFs and other Eoarchaean Greenland samples, such as G91/26 from Akilia, suggests that the processes of carbonate ion complexation controlling the REE − Y patterns were already established in the hydrosphere at the start of the sedimentary record 3,600–3,850 Ma ago. This is in accord with the presence of Eoarchaean siderite-bearing marbles of sedimentary origin, and suggests that CO₂ may have been a significant greenhouse gas at that time.  相似文献   

Evolution of groundwater salinity in the unconfined aquifer of Bou-Areg, Northeastern Mediterranean coast, Morocco     

A. El Mandour  F. El Yaouti  Y. Fakir  Y. Zarhloule  J. Benavente 《Environmental Geology》2008,54(3):491-503

The Bou-Areg plain in the Mediterranean coast at the North-eastern of Morocco is characterized by a semi-arid climate. The aquifer consists of two sedimentary formations of Plio-quaternary age: the upper formation of fine silts and the lower one of coarse silts with sand and gravels. The aquifer is underlain by marly bedrock of Miocene age that dips toward the coastal lagoon of Bou-Areg. The hydrodynamic characteristics vary between 10⁻⁴ and 10⁻³ m/s; and transmissivities range between 10⁻⁴ and 10⁻¹ m²/s. The general direction of flow is SW to NE, toward the lagoon. The aquifer is crossed by the river Selouane, which also ends in the lagoon. The groundwater is characterized by a high salinity that can reach 7.5 g/l. The highest values are observed in the upstream and in the downstream sectors of the aquifer. The temporal evolution of the physico-chemical parameters depends on the climatic conditions and piezometric variations. The analysis of the spatio-temporal distribution of the physico-chemical parameters suggests different sources of groundwater salinization: the seawater intrusion, the influence of marly gypsum-bearing terrains, and the influence of anthropogenic products as the agricultural fertilizers, which cause great nitrate concentrations that vary between 80 and 140 mg/l.  相似文献   

正己烷/海水微乳液形成的相图研究   总被引：3，自引：0，他引：3  

陈国华  江澎  陈颖  纪红 《海洋与湖沼》1995,26(6):619-624

用相图方法研究正己烷／海水微乳液的形成。体系相图由水（或人工海水，盐度分别为０，１３．６９６，３０．０７０和４１．１１８）／油（正己烷）／表面活性剂（ＡＳ，ＣＴＡＢ及ＢＲＩＪ３５）／助表面活性剂（正丁醇）在４０℃时构成。分别研究表面活性剂类型，油及醇含量和海水盐度对微乳液形成的影响。结果表明：醇与表面活性剂的摩尔浓度比值大于１时，最适宜于形成微乳液；形成微乳液区的面积随正己烷含量增加而减少；含离子  相似文献   

综合治水,开发青岛的新水源     

刘洪滨 《海岸工程》1996,15(1):39-45

扼要论述了青岛市水资源面临短缺的严重形势，认为解决青岛地区水危机仅靠传统开发水资源方式已很困难，必需积极利用青岛的科技、资源优势，开发新水源。  相似文献   

海水中溴离子气相色谱测定法的研究          下载免费PDF全文

崔仙舟  王中柱  徐格  贾烨 《海洋与湖沼》1993,24(4):414-419

研究了用气相色谱测定海水及天然水中溴离子含量的方法,确定了最佳条件。天然海水,稀释200倍后;取10ml稀释水样,用氯胺T为氧化剂,将Br-氧化为溴,在六次甲基四胺催化的条件下,溴与丁酮反应生成溴代丁酮;用环已烷萃取后,用ECD检测器测定。此方法简便快速,对溴离子含量较低的天然水尤为适用。方法与碘量法相对照,取得满意结果。  相似文献   

Water surface resonance in the L-shaped channel of seawater exchange breakwater     

Changhoon Lee  Dal Soo Lee 《Ocean Engineering》2003,30(18):2423-2436

The resonance period of the L-shaped channel in the caisson is predicted analytically for the seawater exchange breakwater of “Applicability Study of the Seawater Exchange Breakwater (1). Korea Ministry of Maritime Affairs and Fisheries (in Korean) (1999a)”. Hydraulic experiments are conducted for a composite breakwater with a rear reservoir that is one of the seawater exchange breakwaters developed by them. For regular waves, the water surface elevation in the channel and the flow rate through the breakwater are measured. For irregular waves, the flow rate through the breakwater and the reflection coefficient on the breakwater are measured. The resonant maximum values in both the surface elevation and the flow rate, and the resonant minimum values in the reflection coefficient are all at wave periods slightly longer than analytically predicted ones. The measured resonance period for irregular waves is closer to the predicted one than for regular waves. If the resonance period of the L-shaped channel is fitted to the dominant period of incident waves, there would be high efficiency of seawater exchange between inside and outside the harbor.  相似文献   

Wave forces on a seawater intake caisson     

S. Neelamani  N. Uday Bhaskar  K. Vijayalakshmi 《Ocean Engineering》2002,29(10):1247-1263

The wave force on a seawater intake structure consisting of a perforated square caisson of 400 mm×400 mm size encircling a vertical suction pipe of 160-mm diameter is investigated using physical model studies. The porosity of caisson was varied from 1.6 to 16.9%. Regular and random waves of wide range of heights and periods were used. It is found that the force ratio (ratio of the force on perforated caisson to the force on caisson with zero percent porosity) reduces to an extent of up to 60% with increase in porosity of the caisson from 1.6 to 16.9%. The force ratio was found to increase with increase in relative wave height and reduces with increase in relative width. Multiple regression analysis of the measured data points was carried out and predictive equations for wave force ratios are obtained both for regular and random waves. The results of this investigation can be used in the hydrodynamic design of perforated caissons, which are widely used as seawater intake structures.  相似文献   

A high sensitivity, low volume HPLC method to determine soluble reactive phosphate in freshwater and saltwater   总被引：1，自引：0，他引：1  

Jaime L. Haberer  Jay A. Brandes   《Marine Chemistry》2003,82(3-4):185-196

A reverse phase High Performance Liquid Chromatography (HPLC) method was developed to detect soluble reactive phosphate (SRP) in marine and freshwater samples. This technique is scalable over a range of sample volumes from 10 μl to 10 ml, requires minimal sample preparation, and responds linearly from 1 nM to 100 μM (R²>0.964). Standard Murphy–Riley molybdenum blue reagents were used to react with phosphate in samples for analysis. Solid phase extraction tubes were used to clean the mixed complexing reagent prior to combining the reagent with samples. The method was applied to freshwater samples collected in July 2001 along an Andean mountain stream located in the Eastern Cordillera (2400 m) of Peru and marine samples collected in January 2002 within the low marsh of the estuarine Nueces Delta System, Texas Coastal Bend. For method comparison, field samples were analyzed using a standard manual spectrophotometric method. Field sample phosphate concentrations produced from each method were nearly identical. This method offers the advantages of low sample volume (1 ml or less) with high sensitivity, precision, and potential automation.  相似文献   

Analysis of seawater and different highly saline natural waters by capillary zone electrophoresis     

Andrei R. Timerbaev  Keiichi Fukushi 《Marine Chemistry》2003,82(3-4):221-238

Innovative applications of capillary zone electrophoresis (CZE) to the determination of inorganic ions in environmental aquatic samples of high salinity and, particularly, in seawater are reviewed. Emphasis is placed on advanced approaches utilized for securing separation performance from being degraded by the presence of matrix salts and for simultaneous separation of ions different in natural abundance. Also covered are methodologies of present or possible use to evolve the method's practical utility to trace-level ions. Surveyed procedures are tabulated for the purpose of facilitating the method selection or further development. In addition, brief background information on basic methodological principles of CZE in inorganic ion analysis is given for a better orientation of those intending or just beginning to put CZE to work. Finally, possible future research trends and developments of CZE in the area are briefly discussed.  相似文献   

海水中微量无机离子的气相色谱测定的研究     

崔仙舟  尹相淳 《海洋湖沼通报》1995,(3):32-38

本文讨论了介绍了用气相色谱法测定海水中无机离子Ｓｅ（－Ⅱ，Ｏ，Ⅳ，Ⅵ）；Ｂｅ（Ⅱ）；Ｃｒ（Ⅲ，Ⅳ）；ＣＨ３Ｈｇ＾＋，ＮＯ３，ＮＯ２，Ｂｒ，Ｉ，ＣＮ的测定方法和色谱条件。  相似文献