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71.
Seawater samples are collected in the spring of 2013 from the Taiwan Strait for the analysis of uranium(U)concentrations and isotopic compositions using MC-ICP-MS, and the geochemical behavior patterns of U in the Taiwan Strait are then investigated. Average concentrations of individual U isotopes are(3.23±0.14) μg/kg for 238 U,(2.34±0.09)×10~(–2) μg/kg for ~(235)U and(2.05±0.07)×10~(–4) μg/kg for 234 U. Correspondingly, the U isotopic compositions are 155±18 for δ234U and 138±2 for 238U:235U. The U concentrations and isotopic ratios in the Taiwan Strait are similar to those of open ocean seawater, suggesting the dominance of the open ocean input to the strait's U pool.However, river input, as suggested by the slightly lower salinity than that of the open ocean, also affected the U concentrations and isotopic compositions in the strait. From a compilation of U concentrations in the Taiwan Strait and adjacent areas, including the Jiulong Estuary and Zhujiang Estuary, the Xiamen Bay and the northern South China Sea, a strong and significant relationship between U concentration and salinity [U:S; U=(0.093 4±0.002 4)S+(0.092 0±0.061 5)] is revealed, suggesting conservative mixing of U in the Taiwan Strait. To better understand the U geochemistry in the Taiwan Strait, a multiple endmembers mixing model is applied to estimate the contributions of potential sources. The open ocean seawater contributed 69%–95% of U in the Taiwan Strait, with river water approximately 2%, and dust deposition only around 0.13%. Therefore, the model results supported the open ocean input source and the conservative mixing behavior of U derived from the observation of U concentrations and isotopic ratios and U:S ratios. The sediment interstitial water may be an important source of U to the Taiwan Strait with a possible contribution of 3%–29%, consistent with previous investigations based on radium isotopes.However, further investigations are warranted to examine the U concentration in the sediment interstitial water and its input to the overlying seawater in the Taiwan Strait. 相似文献
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Zoltán Zajacz Werner Halter Wim J. Malfait Olivier Bachmann Robert J. Bodnar Marc M. Hirschmann Charles W. Mandeville Yann Morizet Othmar Müntener Peter Ulmer James D. Webster 《Contributions to Mineralogy and Petrology》2005,150(6):631-642
A new approach was developed to measure the water content of silicate glasses using Raman spectroscopy, which is independent
of the glass matrix composition and structure. Contrary to previous studies, the compositional range of our studied silicate
glasses was not restricted to rhyolites, but included andesitic, basaltic and phonolitic glasses. We used 21 glasses with
known water contents for calibration. To reduce the uncertainties caused by the baseline removal and correct for the influence
of the glass composition on the spectra, we developed the following strategy: (1) application of a frequency-dependent intensity
correction of the Raman spectra; (2) normalization of the water peak using the broad T–O and T–O–T vibration band at 850–1250 cm−1 wavenumbers (instead of the low wavenumber T–O–T broad band, which appeared to be highly sensitive to the FeO content and
the degree of polymerization of the melt); (3) normalization of the integrated Si-O band area by the total number of tetrahedral
cations and the position of the band maximum. The calibration line shows a ±0.4 wt% uncertainty at one relative standard deviation
in the range of 0.8–9.5 wt% water and a wide range of natural melt compositions. This method provides a simple, quick, broadly
available and cost-effective way for a quantitative determination of the water content of silicate glasses. Application to
silicate melt inclusions yielded data in good agreement with SIMS data. 相似文献
74.
Settling velocity of diluted suspended aggregates is examined under steady-state conditions. It is shown that if the local settling velocity of the suspended mass of sediments at the bottom is gamma distributed, then, the vertical variation of the local mean settling velocity is proportional to a power of the local concentration C, where r is the gamma distribution parameter. That is a consequence of the suspended-sediment sorting produced by the vertical dynamics. The parameter r characterizes the range of settling velocity values for all the aggregates simultaneously in suspension. To cite this article: M. Sánchez et al., C. R. Geoscience 337 (2005). 相似文献
75.
A Merchantek LUV266 TM petrographic ultraviolet (UV) laser microprobe has been used in conjunction with a Finnigan MAT ELEMENT TM high resolution ICP double-focusing mass spectrometer (HR-ICP-MS) for solid microsampling and geochemical analysis. This new configuration for laser ablation has the advantage of coupling the high sensitivity and fast scanning technology applied in the ELEMENT with the ablation efficiency of a UV laser. Optimisation of the configuration on the synthetic NIST SRM 612 glass standard reference material using Q-switched UV laser energy of 2 mJ and a 5 Hz repetition rate demonstrates: (1) a linear element response factor throughout the mass spectrum, suggesting limited fractionation during laser ablation; (2) a high sensitivity and very low background noise for most elements of interest; (3) limits of detection ranging from 3 ng g-1 for Sc to 300 pg g-1 for U; (4) a flat topped peak shape suitable for precise isotopic measurements; and (5) a flat bottomed crater geometry which permits progressive ablation for the analysis of thin sections. Average precision and accuracy estimates based on replicate analyses of synthetic NIST standard reference material and USGS BCR-2G glasses are below 10% for most elements. 相似文献
76.
Spring frosts are feared by farmers, fruit growers, and wine growers as they can cause significant damage to crops when they occur during the development of the plants. In the second half of April 2017, following a very warm period that had caused premature vegetation growth, a cold air mass from the Arctic penetrated central and western Europe, causing severe damage to natural and cultivated vegetation over broad areas. Here, we analyze how exceptional this event was in Switzerland and Germany in relation to the accumulated growing degree days (GDD), used as a proxy for plant phenology advancement. Although this damaging frost was not the latest on record in terms of calendar days, our results show that it was, in some regions, unprecedented in relation to the accumulated warmth during the preceding period, at least since the beginning of instrumental temperature records (1864). Our results also highlight how global warming has considerably increased the number of days with mean temperature above 5 °C in late winter and early spring, especially since 1970 (+?16.8?±?4.7 °C days decade?1). However, in spite of earlier spring phenology due to climate warming, our results suggest that the risk of damaging frost events to vegetation has remained unchanged over the last 150 years in lowlands of Switzerland and Germany, due to the concurring earlier occurrence of the last potentially damaging frosts (about ??20 days since 1864). Our analyses reveal therefore that the April 2017 damaging frost was a true outlier in terms of risk of frost damage to plants. 相似文献
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秦岭翠华山水湫池地区分布的黑云母花岗岩是陕西翠华山国家山崩地质公园的崩塌母岩,目前还未见对其系统地开展年代学、地球化学研究。本文在野外调查的基础上,对翠华山水湫池地区分布的黑云母花岗岩首次进行了LA-ICP-MS锆石U-Pb测年、Lu-Hf同位素及全岩地球化学分析,获得锆石U-Pb加权平均年龄为149.4Ma±1.1 Ma,时代属于晚侏罗世;结合前人的研究成果资料,翠华山复式岩体可能存在~227 Ma、~150 Ma、~119 Ma三期岩浆侵位活动;全岩地球化学分析具有高硅(w(SiO2)=69.83%~75.31%)、富钾(w(K2O)=2.71%~5.23%)、弱过铝质(A/CNK=1.00~1.07)特征,属于高钾钙碱性-钾玄岩Ⅰ型花岗岩;其轻、重稀土分馏明显(w(LREE)/w(HREE)=10.09~67.50),富集LILE(K、La、Pb、Sr)、亏损HFSE(Ta、Nb、P、Ti),Eu呈弱负异常—轻微正异常,且显示高Sr低Y花岗岩特征;锆石Hf同位素分析得出εHf(t)=-4.6~-1.4,T... 相似文献
80.
In this paper we present a workflow for microseismic feasibility studies that allows a thorough assessment of the probability of success of the monitoring project to be made. The workflow includes the following elements: assessment of the value of information to establish the business case; identification of hardware options to investigate deployment options; survey of analogue cases to confirm the do‐ability of the project; modelling of event location errors and detectability to establish the most favourable array geometry; generation of full waveform synthetics to anticipate undesired seismic features. A study comprising all these elements provides the reference frame for discussions with service companies, limiting misunderstandings and avoiding missed opportunities. 相似文献