Determination of Major/ Minor and Trace Elements in Silicate Samples by ICP-QMS and ICP-SFMS Applying Isotope Dilution-Internal Standardisation (ID-IS) and Multi-Stage Internal Standardisation

A method for the determination of major, minor and trace elements in silicate samples by ICP‐QMS and ICP‐SFMS applying isotope dilution‐internal standardisation (ID‐IS) and multi‐stage internal standardisation has been developed. Samples with an enriched isotope of ¹⁴⁹Sm (spike) were decomposed by a HF/HCIO₄ mixture and stepwise drying and finally diluted. In ID‐IS for trace element analyses by Q‐pole type ICP‐MS (ICP‐QMS), the Sm concentration was determined by ID, while other trace elements (Li, Be, Rb, Sr, Y, In, Cs, Ba, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Tl, Pb, Bi, Th and U) were determined using the ¹⁴⁹Sm intensity as an internal standard. Major and minor elements were determined by multi‐stage internal standardisation, with Na, Mg, Al, P, Ca, V, Mn, Fe and Co measured by sector magnetic field type ICP‐MS (ICP‐SFMS) at middle resolution (MR; M/AM =～ 3000) using Sr determined by ICP‐QMS in the sample as the internal standard. Potassium, Sc, Ni, Cu, Zn and Ga were measured at high resolution (HR; M/ΔM ～ 7500) using the Sr concentration obtained by ICP‐QMS or the Mn concentration obtained by ICP‐SFMS at MR as internal standard. The merit of ID‐IS is that accurate dilution of the sample is not required. Matrix effects on elemental ratios down to a dilution factor (DF) of 600 were not observed in either types of mass spectrometry. Pseudo‐flow injection (FI), where transient signals were integrated, was used in ICP‐QMS, while conventional continuous sample introduction was used in ICP‐SFMS, resulting in total required sample solutions of 0.026 ml and 0.08 ml, respectively. Detection limits were low enough to determine these elements in depleted ultramafic rocks, and typical reproducibilities for basalts were 3% (Li‐Be), 1% (Rb‐U), 5% (In, Tl and Bi), 7% (Sc‐Ga) and 3% (major elements). Carbonaceous chondrites including Orgueil (Cll), Murchison (CM2) and Allende (CV3), as well as reference materials, JB‐1, ‐2, ‐3, JA‐1, ‐2, ‐3 and JP‐1 (GSJ), BHVO‐1, AGV‐1, PCC‐1 and DTS‐1 (USGS), were analysed to show the applicability of this method. Une méthode permettant la détermination des éléments majeurs, mineurs et en trace dans les echantillons silicates par ICP‐QMS et ICP‐SFMS a été développée. Elle combine la standardisation interne par dilution isotopique (ID‐IS) et la standardisation interne en deux étapes. Les échantillons, auxquels est ajouté un spike enrichi en ¹⁴⁹ Sm, sont décomposés par une mixture HF/HCIO_4′ séchés progressivement puis dilués. Dans la phase de standardisation interne par dilution isotopique avec un ICP‐MS à quadrupôle (ICP‐QMS), la concentration en Sm est déterminée par dilution isotopique tandis que les autres éléments en trace (Li, Be, Rb, Sr, Y, In, Cs, Ba, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Tl, Pb, Bi, Th et U) sont déterminés en utilisant le signal de ¹⁴⁹ Sm comme standard interne. Les éléments majeurs et mineurs sont déterminés par standardisation interne par étapes, avec Na, Mg, Al, P, Ca, V, Mn, Fe et Co mesurés par ICP‐MS à secteur magnétique (ICP‐SFMS) en résolution intermédiaire (MR; M/ΔM =～ 3000 en utilisant Sr, mesuré par ICP‐QMS comme standard interne. Les éléments K, Sc, Ni, Cu, Zn et Ga sont mesurés en Haute Résolution (M/ΔM ～ 7500) en utilisant comme standard interne, soit la concentration en Sr obtenue par ICP‐QMS soit la concentration en Mn obtenue par ICP‐SFMS en résolution moyenne. La technique de ID‐IS a l'avantage de ne pas nécessiter la connaissance exacte du facteur de dilution de l'Schantillon. Aucun effet de matrice sur la mesure de rapports élémentaires n'a été observé sur l'un ou l'autre des spectromètres de masse, ceci jusqu'à un facteur de dilution (DF) de 600. Les analyses par ICP‐QMS ont été effectuées par pseudo injection de flux (Fl) et intégration d'un signal transitoire tandis que les analyses par ICP‐SFMS l'ont été avec un système conventionnel d'introduction. Le volume total de solution d'échantillon nécessaire etait de 0.026 ml et 0.08 ml respectivement. Les limites de détection étaient suffisamment basses pour permettre la détermination de ces éléments dans des roches ultrabasiques et les reproductibilités pour les basaltes étaient de l'ordre de 3% (Li‐Be), 1 % (Rb‐U), 5% (In, Tl et Bi), 7% (Sc‐Ga) et 3% (tous les éléments majeurs). Des chondrites carbonées dont Orgueil (Cll), Murchison (CM2) et Allende (CV3) ainsi que des matériaux de référence JB‐1, ‐2, ‐3, JA‐1, ‐2, ‐3 et JP‐1 (GSJ), BHVO‐1, AGV‐1, PCC‐1 et DTS (USGS) ont été analysés pour démontrer l'applicabilité de la méthode.     

Historical change in lake sedimentation in Lake Takkobu, Kushiro Mire, northern Japan over the last 300 years

Environmental degradation, including shallowing, deterioration of aquatic habitat and water pollution, has arisen from the inflow of fine sediment to Lake Takkobu in northern Japan. The lake has experienced gradual environmental degradation due to agricultural development, which has introduced both fine sediment and sediment-associated nutrients into the lake. We have reconstructed the history of sediment yield to Lake Takkobu in Kushiro Mire over the last 300 years and have examined trends with reference to land-use development. Fifteen lake sediment core samples were obtained, and various physical variables of lake sediments were analyzed and dated using ¹³⁷Cs and tephrochronology. The physical variables showed that all points contained mainly silt, except for two points close to the river mouths, where the mean diameter was < 35 μm. The peaks were defined as a “signal” when the physical variables were synchronous in a profile. These were created by floods and engineering works constructing drainage systems. The signal of canal construction in 1898 was detected in all core points. Lake Takkobu core samples contained two tephra layers. From the refractive indices of dehydrated glasses, the lower tephra layer was identified as Ko-c2 (1694) and the upper tephra layer as Ta-a (1739). A clear peak in the ¹³⁷Cs concentration was detected at all the sampling points, except for the site close to the Takkobu River. This site showed two peaks in the ¹³⁷Cs concentration, which was attributed to perturbation from flood events and a drainage project. The maximum ¹³⁷Cs concentration was identified as the sediment surface from 1963, enveloped by the 1962 and 1964 signals. The sediment yield averaged over the last 300 years for Lake Takkobu was reconstructed for four periods using the signal, tephra and ¹³⁷Cs as marker layers. The sediment yield under the natural erosion condition for the first two periods was 226 tons/year from 1694 to 1739 and 196 tons/year from 1739 to 1898. The development of the Takkobu watershed started in 1880s with partial deforestation and channelization in 1898, 1959, and 1962 leading to an increased sedimentation yield of 1016 tons/year from 1898 to 1963. Continued deforestation, channelization works in 1964, road construction in 1980–1990s, as well as agriculture development caused a further increase to 1354 tons/year from 1963 to 2004. Compared to the averaged natural sedimentation yield of 206 tons/year until 1898, initial land-use development in a catchment accelerated lake sedimentation, indicated by the 5-fold sediment yield. With increasing agricultural development since 1960s, sedimentation yields were highest for 1963–2004; a 7-fold increase compared with pre-impact conditions. To reduce sediment yield, riparian buffers along the rivers should be preserved or rebuilt, and sluices may function effectively during short-term periods of flooding. Environmental management policy and laws restricting uncontrolled and inappropriate land-use might help in addition to ensure longer-term environmental health by reducing the sedimentation rate.     

Shallow Drainage Flows

Two-dimensional sonic anemometers and slowresponse thermistors were deployedacross a shallow gully during CASES99. Weak gully flow of a few tenths of m s^-1 anda depth of a few metres develops in the earlyevening on most nights with clear skies.Flow down the gully developed sometimes evenwhen the opposing ambient wind exceeded10 m s^-1 at the top of the60–m tower. Cold air drainage fromlarger-scale slopes flows over the top ofthe colder gully flow. The gully flowand other drainage flows are generally eliminated in the middle of the night in conjunctionwith flow acceleration abovethe surface inversion layer and downwardmixing of warmer air and highermomentum. As the flow decelerates later inthe night, the gully flow may re-form.The thin drainage flows decouple standard observational levels of3–10 m from the surface.Under such common conditions, eddy correlationflux measurements cannot be used toestimate surface fluxes nor even detect thethin gully and drainage flows. The gentlegully system in this field program is typical ofmuch of the Earths land surface.     

Optimum design and earthquake-response constrained design of elastic shear buildings

The necessary and sufficient conditions for global optimality and the closed form solution are derived for a problem of minimizing a weighted sum of storey stiffnesses of a shear building subject to a fundamental frequency constraint. A set of higher frequency formulae is derived for optimally designed shear buildings with equal masses. It is shown that, if the weight coefficients are regarded as parameters for adjustment, the distribution of the SRSS estimates of the maximum interstorey drifts can be adjusted so as to coincide with a specified one. The base shear–fundamental period formulae and the base shear–design drift formulae are derived semi-analytically for shear buildings with equal masses on the basis of the optimum design formulae and the SRSS estimates of the maximum interstorey drifts. Some numerical examples are presented in order to illustrate the validity of the proposed method of earthquake-response constrained design.     

Deep-sea submersible survey in the Suruga, Sagami and Japan Trenches: preliminary results of the 1985 Kaiko cruise, Leg 2

Nine submersible dives were made in three trenches off central Japan, between 2990 and 5900 m of water depth. Our observations confirm the interpretation that Daiichi-Kashima Seamount is a Cretaceous guyot formed on the Pacific plate that has traveled into the Japan Trench. We also confirmed the previous interpretation of a large normal fault that splits the seamount in two halves, the lower one being now subducting beneath the Japan margin. Compressional deformation was identified within the lower part of the inner slope in front of the seamount. The pattern of deformation that affects Quaternary sediments is in agreement with the present kinematics of the convergence between the Pacific plate and Japan. Deep-water (5700 m) clam colonies are associated with advection of fluids, driven by the subduction-related overpressures. In the northern slope of the Boso Canyon, along the Sagami Trough system (Philippine Sea plate-Japan boundary), the deformation affecting a thick upper Miocene to lower Pliocene sequence indicates two directions of shortening: a N175°E direction which is consistent with the present relative motion along the Sagami Trough (N285–N300°E) and a N30°E direction which could be related to a more northerly direction of convergence that occured during the early Quaternary and earlier.     

Precise temperature measurement of groundwater for earthquake-prediction study

Precise measurements of groundwater temperature, with a resolution of 0.0001°C, have been made for the purpose of earthquake prediction at four water wells in the Tokai district in Japan. The characteristics of temporal variations in groundwater temperature differ from well to well. From records of a well located in an area where use of groundwater is heavy, movement of groundwater was sensed by temperature variations. By contrast, water temperatures in a 500 m well far from cultural areas were extremely steady, with fluctuations of less than 0.0005°C. This well appears to be suitable for monitoring possible temperature changes related to the occurrence of an impending large earthquake.     

Origin and evolution of the Nakhla meteorite inferred from the Sm-Nd and U-Pb systematics and REE,Ba, Sr,Rb and K abundances

Analyses of Sm-Nd and U-Th-Pb systematics, REE, Ba, Sr, Rb and K concentrations were carried out for whole rock and mineral separates from the Nakhla meteorite. The 1.26 ±.07 b.y. Sm-Nd age obtained in this work is in good agreement with those previously obtained by the Rb-Sr and Ar-Ar methods. The high initial ?_Nd value of +16 suggests that Nakhla was derived from a light REE-depleted, old planetary mantle source. U-Th-Pb data, after correction for pre-analytical terrestrial Pb contamination assuming an age of 1.26 b.y., suggest that the age of the Nakhla source is ?4.33 b.y. The agreement in the age determined by three independent radiometric methods and the high initial ?_Nd value strongly suggest that the 1.3 b.y. age dates one thorough igneous event in the parent body which not only reset these isotopic systems but also established the chemical and petrologic characteristics observed for the Nakhla meteorite.Using a three-stage Sm-Nd evolution model in combination with LIL element data and estimated partition coefficients, we have tested partial melting and fractional crystallization models to estimate LIL element abundances in a possible Nakhla source. Our model calculations suggest that partial melting of the light REE-depleted source followed by extensive fractional crystallization (?50%) of the partial melt could account for the REE abundances in the Nakhla constituent minerals. The estimated source is depleted in the light REE, Ba, Rb and K and therefore may resemble the MORB source in the earth's upper mantle or the upper 60–300 km of the moon.The significantly younger age of Nakhla than the youngest lunar rock; the young differentiation age inferred from the U-Th-Pb data, and the estimated LIL element abundances (including those of K, U and Th) in the source suggest that the Nakhla meteorite may have been derived from a relatively large, well-differentiated planetary body such as Mars.     

Dynamical seasonal prediction of Southern African summer precipitation

Prediction skill for southern African (16°–33°E, 22°–35°S) summer precipitation in the Scale Interaction Experiment-Frontier coupled model is assessed for the period of 1982–2008. Using three different observation datasets, deterministic forecasts are evaluated by anomaly correlation coefficients, whereas scores of relative operating characteristic and relative operating level are used to evaluate probabilistic forecasts. We have found that these scores for December–February precipitation forecasts initialized on October 1st are significant at 95 % confidence level. On a local scale, the level of prediction skill in the northwestern and central parts of southern Africa is higher than that in northeastern South Africa. El Niño/Southern Oscillation (ENSO) provides the major source of predictability, but the relationship with ENSO is too strong in the model. The Benguela Niño, the basin mode in the tropical Indian Ocean, the subtropical dipole modes in the South Atlantic and the southern Indian Oceans and ENSO Modoki may provide additional sources of predictability. Within the wet season from October to the following April, the precipitation anomalies in December-February are the most predictable. This study presents promising results for seasonal prediction of precipitation anomaly in the extratropics, where seasonal prediction has been considered a difficult task.     

Anomalously large seismic amplifications in the seafloor area off the Kii peninsula

Seismic wave amplifications were investigated using strong-motion data obtained from the ground’s surface (K-net) on the Kii peninsula (southwestern Japan) and from the network of twenty seismic stations on the seafloor (DONET) located off the peninsula near the Nankai trough. Observed seismograms show that seismic signals at DONET stations are significantly larger than those at K-net stations, independent of epicentral distances. In order to investigate the cause of such amplifications, seismic wavefields for local events were simulated using the finite-difference method, in which a realistic 3D velocity structure in and around the peninsula was incorporated. Our simulation results demonstrate that seismic waves are significantly amplified at DONET stations in relation to the presence of underlying low-velocity sediment layers with a total thickness of up to 10 km. Our simulations also show considerable variations in the degree of amplification among DONET stations, which is attributed to differences in the thickness of the sediment layers. The degree of amplification is relatively low at stations above thin sediment layers near the trough axis, but seismic signals are much more amplified at stations closer to the Kii peninsula, where sediment layers are thicker than those at the trough axis. Simulation results are consistent with observations. This study, based on seafloor observations and simulations, indicates that because seismic signals are amplified due to the ocean-specific structures, the magnitude of earthquakes would be overestimated if procedures applied to data observed at land stations are used without corrections.     

Chemical evidence for the origin of the cold water belt along the northeastern coast of Hokkaido

In the southwestern Okhotsk Sea, the cold water belt (CWB) is frequently observed on satellite images offshore of the Soya Warm Current flowing along the northeastern coast of Hokkaido, Japan, during summertime. It has been speculated that the CWB is upwelling cold water that originates from either subsurface water of the Japan Sea off Sakhalin or bottom water of the Okhotsk Sea. Hydrographic and chemical observations (nutrients, humic-type fluorescence intensity, and iron) were conducted in the northern Japan Sea and southwestern Okhotsk Sea in early summer 2011 to clarify the origin of the CWB. Temperature–salinity relationships, vertical distributions of chemical components, profiles of chemical components against density, and the (NO₃ + NO₂)/PO₄ relationship confirm that water in the CWB predominantly originates from Japan Sea subsurface water.