Barium Isotopic Compositions in Thirty‐Four Geological Reference Materials Analysed by MC‐ICP‐MS     

Ya‐Jun An  Xin Li  Zhao‐Feng Zhang 《Geostandards and Geoanalytical Research》2020,44(1):183-199

Measurement of Ba isotope ratios of widely available reference materials is required for interlaboratory comparison of data. Here, we present new Ba isotope data for thirty‐four geological reference materials, including silicates, carbonates, river/marine sediments and soils. These reference materials (RMs) cover a wide range of compositions, with Ba mass fractions ranging from 6.4 to 1900 µg g^?1, SiO₂ from 0.62% to 90.36% m/m and MgO from 0.08% to 41.03% m/m. Accuracy and precision of our data were assessed by the analyses of duplicate samples and USGS rock RMs. Barium isotopic compositions for all RMs were in agreement with each other within uncertainty. The variation of δ^138/134Ba in these RMs was up to 0.7‰. The shale reference sample, affected by a high degree of chemical weathering, had the highest δ^138/134Ba (0.37 ± 0.03‰), while the stream sediment obtained from a tributary draining carbonate rocks was characterised by the lowest δ^138/134Ba (?0.30 ± 0.05‰). Geochemical RMs play a fundamental role in the high‐precision and accurate determination of Ba isotopic compositions for natural samples with similar matrices. Analyses of these RMs could provide universal comparability for Ba isotope data and enable assessment of accuracy for interlaboratory data.  相似文献   

内蒙古贺斯格乌拉牧场白音高老组火山岩U-Pb年龄及地球化学特征     

胡振华 《地质与勘探》2020,56(2):359-371

白音高老组火山岩在大兴安岭地区广泛分布,本文对大兴安岭中南部贺斯格乌拉牧场白音高老组酸性火山岩进行了锆石U-Pb年代学、岩石地球化学和Sr-Nd同位素分析,探讨其岩石成因及构造背景。位于大兴安岭中南段东乌旗地区的白音高老组火山岩,主要岩性为流纹岩、流纹质凝灰岩等,LA-ICP-MS锆石U-Pb年龄分别为129. 8±0. 8 Ma、128. 2±2. 8 Ma,属早白垩世早期;从岩石地球化学特征上看,其主量元素SiO_2含量68. 76%～76. 18%、Al_2O_3含量11. 84%～13. 38%,属高钾钙碱性岩石;稀土总量较高,(La/Yb)N 6,(La/Sm)_N 3,显示为轻稀土富集型,δEu显示负铕异常(0. 4～0. 6),微量元素以富集大离子亲石元素K、Rb、Ba,贫高场强元素Nb、P、Ti为特征; Sr-Nd同位素组成上具有低I_(Sr)、高ε_(Nd)(t)和低t_(DM)的特征(I_(Sr)=0. 7039～0. 7045,ε_(Nd)(t)=2. 65～4. 39)。火山岩浆来源于下地壳基性物质的部分熔融,综合研究并结合前人资料认为,白音高老组流纹岩形成于滨太平洋板块俯冲后伸展及蒙古-鄂霍次克洋闭合后的综合效应下。  相似文献   

钾稳定同位素研究综述     

王昆  李伟强  李石磊 《地学前缘》2020,27(3):104-122

钾稳定同位素是重要的非传统稳定同位素体系,也是近年来迅速发展的热门研究课题。对钾同位素研究历史和现状进行综述,具体包括以下内容:(1)总结了钾元素的地球化学和宇宙化学性质,包括钾在主要地质储库(地幔、地壳、海洋)中的丰度及其分配,钾在岩浆演化中的不相容大离子亲石性,常见含钾火成岩/沉积岩矿物以及钾在表生过程中的循环,也包括主要行星物质(球粒陨石、非球粒陨石、火星和灶神星陨石以及月球样品)中钾的含量、赋存状态、主要矿物,钾在太阳星云冷凝、行星积聚以及岩浆海过程中的中等挥发性质;(2)介绍了钾同位素的研究历史,从1922年Dempster利用最早的质谱仪测量钾同位素在自然界的丰度,到Taylor和Urey在1938发表的经典的钾同位素分馏实验,再到Humayun和Clayton在1995年发表的钾同位素领域的经典研究,最后到近几年的进展;(3)介绍了对钾的前处理(离子交换柱法)以及钾同位素的主要测量方法,包括早期热电离质谱仪法(TIMS),二次离子质谱仪法(SIMS)和近十几年以来高速发展的多接收电感耦合等离子体质谱仪法(MC-ICP-MS)及其不同的技术路线;(4)介绍了高精度钾同位素比值在低温地球化学和生物地球化学中的应用,包括钾同位素在地表的风化过程中、海水洋壳的反向风化作用中的分馏及其在示踪全球钾元素循环和洋壳俯冲等过程中的应用;(5)介绍了高精度钾同位素比值在高温地球化学中的应用,包括钾同位素在岩浆分异和矿物结晶过程中的分馏;(6)介绍了高精度钾同位素比值在宇宙化学中的应用,包括在太阳星云冷凝、行星凝聚、月球形成大碰撞、岩浆海、火山喷发去气过程中的分馏作用。  相似文献   

Longitudinal variations of phytoplankton compositions in lake-to-river systems     

《Limnologica》2017

To test the hypothesis of longitudinal variations in phytoplankton compositions from a eutrophic lake to its river downstream and determine the length of the transition zone, we applied functional groups as well as taxonomical methods to this coupled aquatic system, which is composed of the Dianchi Lake upstream and the Tanglang River downstream, by sampling at 9 stations during Microcystis blooms in the Dianchi Lake in 2013. The longitudinal variations in phytoplankton compositions from lacustrine species to fluvial species were reflected by: (1) the shift from Microcystis to Chlorococcales green algae and centric diatoms; (2) the shift from the dominance of codon M to the coexistence of a variety of coda without one outstanding codon; and (3) except for codon M, the shift from lacustrine coda (H1, L_O, T) towards coda that are adapted to both lacustrine and fluvial circumstances (MP, X1, X2). The prominent difference of phytoplankton compositions between the Dianchi Lake and the lower reaches of the Tanglang River revealed that there was a transition zone in between. The upper and middle reaches of the Tanglang River with a length of approximately 26.4 km were considered the transition zone because: (1) the dominant lentic codon M in the Dianchi Lake disappeared at the lower reaches of the river; (2) the amount of codon P that is sensitive to stratification rose at the beginning of the river; and (3) the codon T, which is well adapted to the persistently mixed layer or epilimnia of lakes, lost a large number of biomass at the upper and middle reaches of the Tanglang River. In this study, we found that the eutrophic lake had a significant influence on the river downstream. In addition, we found that functional groups were sensitive to the changes of external aquatic conditions and helpful in determining the length of the transition zone.  相似文献   

Molecular and isotopic compositions of bitumens in Silurian tar sands from the Tarim Basin,NW China: Characterizing biodegradation and hydrocarbon charging in an old composite basin   总被引：1，自引：0，他引：1  

Wanglu Jia  Zhongyao Xiao  Chiling Yu  Ping'an Peng 《Marine and Petroleum Geology》2010

Biodegradation and oil mixing in Silurian sandstone reservoirs of the Tarim Basin, one of the largest composite basins in China, were investigated by analyzing the molecular characteristics and stable carbon isotopic signatures of low-molecular-weight (LMW) saturated hydrocarbons and high-molecular-weight (HMW) asphaltenes. Detection of 25-norhopanes and 17-nortricyclic terpanes in most Silurian tar sands from the Tabei Uplift in the Tarim Basin suggests a much greater degree of biodegradation here than in the Tazhong Uplift. This explains the relatively more abundant tricyclic terpanes, gammacerane, pregnane and diasteranes in tar sands from the Tabei Uplift than in those from the Tazhong Uplift. Hence, care must be taken when assigning oil source correlations using biomarkers in tar sands because of the biodegradation and mixing of oils derived from multiple sources in such an old composite basin. Asphaltenes in the tar sands seem to be part of the oil charge before biodegradation, depending on the relative anti-biodegradation characteristics of asphaltenes, the similarity in carbon isotopic signatures for asphaltenes and their pyrolysates, and the consistent product distribution for flash pyrolysis and for regular steranes in asphaltene pyrolysates, regardless of whether the tar sands were charged with fresh oil. According to the relative distributions of regular steranes and the relatively abundant 1,2,3,4-tetramethylbenzene significantly enriched in ¹³C, the oil sources for asphaltenes in the tar sands might be related to lower Paleozoic marine source rocks formed in euxinic conditions. Nevertheless, the relatively low abundance of gammacerane and C₂₈ regular steranes observed in asphaltene pyrolysates and residual hydrocarbons, within limited samples investigated in this work, made a direct correlation of oils originally charged into Silurian tar sands with those Cambrian source rocks, reported so far, seem not to be possible. Comparison of carbon isotopic signatures of n-alkanes in asphaltene pyrolysates with those of LMW saturated hydrocarbons is helpful in determining if the abundant n-alkanes in tar sands are derived from fresh oil charges after biodegradation. The limited carbon isotopic data for n-alkanes in LMW saturated hydrocarbons from the tar sands can be used to classify oils charged after biodegradation in the composite basin into four distinct groups.  相似文献   

鲁苏榴辉岩的地球化学     

韩宗珠 《中国海洋大学学报(自然科学版)》1994,(1)

以微量元素、稀土元素、Ｓｒ和Ｎｄ同位素变异特征为依据，确定鲁苏榴辉岩为多成因、多来源和多阶段，指出主要是在印支期扬子陆块与华北陆块碰撞造山作用过程中，挤入的上地幔碎片以及不同原岩类型的壳内高压变质岩碎块。燕山晚期的区域构造热事件使得某些榴辉岩的同位素体系再平衡。  相似文献   

Isotopic and Elemental Variations of Carbon and Nitrogen in a Mangrove Estuary   总被引：6，自引：0，他引：6  

L.A. Cifuentes  R.B. Coffin  L. Solorzano  W. Cardenas  J. Espinoza  R.R. Twilley 《Estuarine, Coastal and Shelf Science》1996,43(6):781-800

Variations in elemental and isotopic ratios of suspended particulate matter (SPM) were investigated in the Guayas River Estuary Ecosystem (GREE) that empties into the Gulf of Guayaquil, Ecuador. Detritus in the system was identified on the basis of extremely high carbon:chlorophyll aratios (>1000). This material had mean δ¹³C of −26·4±0·3, δ¹⁵N of +4·8±0·2, and (C:N)_atomicof 14·1±0·9. The isotopic data were comparable to measurements reported for fresh and degrading mangrove leaves, whereas the elemental ratio was comparatively enriched in nitrogen. Isotope measurements of SPM throughout the GREE were more similar to values for riverine material and detritus compared with that for the coastal end-member. Values indicative ofin situproduced algae, sewage and shrimp pond effluent were only found at selected sites. Bacterial bioassays, which were used to document potential sources of dissolved organic matter in the GREE, were isotopically similar to SPM. This correspondence coupled with the relatively low (C:N)_aof SPM could be explained by bacterial immobolization of nitrogen onto detritus. Finally, tidal variations of (C:N)_aand δ¹³C at a brackish mangrove site were similar in magnitude to spatial variations encountered throughout the GREE. Based on these results, the authors caution that care must be taken when samples are taken for food-web studies in these systems.  相似文献   

环境演变研究时间序列的建立方法评述   总被引：3，自引：0，他引：3  

王晓燕  田均良 《海洋地质前沿》2002,18(12):22-27

对环境演变时间序列建立的几种主要方法的纪年原理、应用状况及应用的优点、范围、局限性进行了阐述和比较，包括长寿命宇宙成因核素在内的同位素纪年方法主要判别第四纪以来大时间尺主的沉积物的地质年龄，且能很好地应用于全球变化的研究，但百余年来沉积物的年龄及侵蚀历史变化的研究只能通过^210Pbex、^137Cs等半衰期相对较短的核素来进行；指出^210Pbex可望在现代流域侵蚀环境演变以及其效应评价的研究中获得新的突破。  相似文献   

大西洋牙鲆幼鱼肌肉组成与营养需求的探讨     

王波  孙丕喜  荆世锡  褚广志 《海洋科学进展》2006,24(3):336-341

测定了养殖大西洋牙鲆幼鱼肌肉中的蛋白质、脂类、灰分等生化组织,并计算了其比能值,分析了肌肉蛋白质中17种常见氨基酸的含量、脂肪酸组成及含量。结果表明:大西洋牙鲆属高蛋白、低脂肪、低比能值鱼类,肌肉氨基酸含量同其它鲆鲽鱼类相比,属中等水平,必需氨基酸和呈味氨基酸的含量较高;肌肉蛋白中氨基酸的支/芳值为2.794;脂肪酸含量中棕榈酸(16∶0)的含量最高,其次为油酸(18∶1 n)和DHA(22∶6 n-3);其EPA(20∶5 n-3)和DHA(22∶6 n-3)的含量较高,营养丰富且平衡良好,是值得推荐的优良养殖品种和食用鱼类。  相似文献   

不同氮源对海洋微藻氮同位素分馏作用的影响     

俞志 明  Waser N A D  Harrison P J 《海洋与湖沼》2004,35(6):524-529

以海链藻(Thalassiosira pseudonana)为研究对象，分别考察了以硝酸盐、铵盐和尿素为氮源的氮同位素分馏作用。在建立相应理论模型基础上，分别计算出各个实验体系的ε值。结果表明，在藻类生长初期，δ^15N均较低，其δ^15N的积累主要发生在指数增长期，在稳定期达到最高，与氮源的初始δ^15N相同；不同氮源的氮同位素分馏作用也不相同，其中以铵盐最强，硝酸盐次之，尿素最弱。考虑到实际情况下氮化合物并非单一存在，作者还进一步考察了上述3种氮源混合后对其同位素分馏作用的影响，发现混合氮源体系的表观ε值介于单一氮源时的最大与最小ε值之间，该结果较好地解释了Montoya等(1991)在Chesapeak湾的现场实验结果。  相似文献