中国土壤湿度的时空变化特征

基于中国155个农业气象观测站1981-2010年逐旬土壤湿度资料,分析了全国和12个气候区域0~50 cm逐层的土壤湿度时空分布规律,采用趋势分析和Cramér-von Mises（CVM）方法探究了土壤湿度的变化趋势及突变性。结果表明：西南、江淮、东北、江南、江汉、黄淮和华南地区各层土壤湿度均高于全国平均值,内蒙古地区最低;随着深度增加,西南地区土壤湿度增加最明显,仅青藏高原地区土壤湿度减小。不同区域0~50 cm各层土壤湿度年变化和季节变化差异明显,并具有阶段性特征,大部地区深层土壤湿度高于浅层;总体上,新疆、华南、华北、青藏高原、东北、黄淮地区1981-2010年土壤湿度减小趋势显著,其中新疆地区减小最为明显。除江淮地区外,各区域土壤湿度均存在较为明显的年际差异,突变时段主要集中在20世纪80年代后期至90年代初期、90年代后期两个时间段。     

利用CRLB的数字摄影测量人工标志定位不确定性评估

考虑影像形成的物理过程,针对叠加零均值高斯白噪声的标志定位模型,利用最大似然估计理论,推导出了基于标志定位不确定性理论的误差性能克拉美-罗下限(Cramér-Rao lower bound,CRLB),同时确定了CRLB在一定置信水平下的置信区间。以圆形标志实验为例,分析了噪声水平和标志大小两个因素对CRLB的影响。     

An Investigation of Digestion Methods for Trace Elements in Bauxite and Their Determination in Ten Bauxite Reference Materials Using Inductively Coupled Plasma‐Mass Spectrometry

Trace elements from samples of bauxite deposits can provide useful information relevant to the exploration of the ore‐forming process. Sample digestion is a fundamental and critical stage in the process of geochemical analysis, which enables the acquisition of accurate trace element data by ICP‐MS. However, the conventional bomb digestion method with HF/HNO₃ results in a significant loss of rare earth elements (REEs) due to the formation of insoluble AlF₃ precipitates during the digestion of bauxite samples. In this study, the digestion capability of the following methods was investigated: (a) ‘Mg‐addition’ bomb digestion, (b) NH₄HF₂ open vessel digestion and (c) NH₄F open vessel digestion. ‘Mg‐addition’ bomb digestion can effectively suppress the formation of AlF₃ and simultaneously ensure the complete decomposition of resistant minerals in bauxite samples. The addition of MgO to the bauxite samples resulted in (Mg + Ca)/Al ratios ≥ 1. However, adding a large amount of MgO leads to significant blank contamination for some transition elements (V, Cr, Ni and Zn). The NH₄HF₂ or NH₄F open vessel digestion methods can also completely digest resistant minerals in bauxite samples in a short period of time (5 hr). Unlike conventional bomb digestion with HF/HNO₃, the white precipitates and the semi‐transparent gels present in the NH₄HF₂ and NH₄F digestion methods could be efficiently dissolved by evaporation with HClO₄. Based on these three optimised digestion methods, thirty‐seven trace elements including REEs in ten bauxite reference materials (RMs) were determined by ICP‐MS. The data obtained showed excellent inter‐method reproducibility (agreement within 5% for REEs). The relative standard deviation (% RSD) for most elements was < 6%. The concentrations of trace elements in the ten bauxite RMs showed agreement with the limited certified (Li, V, Cr, Cu, Zn, Ga, Sr, Zr and Pb) and information values (Co, Ba, Ce and Hf) available. New trace element data for the ten RMs are provided, some of which for the first time.     

阿尔金山北缘冰沟蛇绿混杂岩中辉长岩锆石SHRIMP U-Pb定年及其地质意义

冰沟蛇绿混杂岩是阿尔金山红柳沟蛇绿混杂岩带的东段部分,岩石组合包括蛇纹岩、方辉橄榄岩、辉石岩和辉长岩等。蛇纹岩具高Mg,Mg/Fe值大于9,低Al、Ca、Na、K为特征,从稀土元素和微量元素特征来看,基性辉长岩和洋壳以及洋中脊玄武岩极为相似,而超基性岩与原始地幔较为接近。辉长岩获得锆石SHRIMP年龄为449.5±10.9Ma。蛇绿混杂岩的围岩为一套巨厚的碎屑岩、火山碎屑岩、火山岩,以及部分碳酸盐岩构成,其中含有具有洋中脊特征的枕状构造玄武岩,以及放射虫硅质岩,放射虫时代为奥陶纪中晚期,与辉长岩的SHRIMP年龄一致。这些证据进一步证实了红柳沟一带存在早古生代洋盆的地质事实。     

Precise and Accurate Doping of Nanoporous Silica Gel for the Synthesis of Trace Element Microanalytical Reference Materials

This study presents an experimental procedure to fabricate high‐purity silica glass containing a selected element at a specified mass fraction. The procedure was used to prepare glasses doped with trace‐level mass fractions of Ti with the goal of improving analytical confidence when measuring trace elements in quartz. Systematic tests were performed to determine the ideal conditions and procedures for doping nanoporous silica gel with the highest efficiency of dopant recovery. Silica gel was cleaned in concentrated HCl, immersed in a non‐polar doping medium at a controlled pH and doped with precise quantities of ICP‐MS standard solution. Using liquids composed of longer chain molecules as the doping medium diminishes recovery, suggesting that large molecules could obstruct nanopores to inhibit capillary uptake of the dopant. A control experiment using crystalline quartz reinforced the effectiveness of nanoporous silica gel for doping with trace‐level precision. Layered aggregates of silica gel doped with different Ti mass fractions were hot‐pressed to create multi‐layered reference materials that were analysed with multiple techniques at a variety of spatial scales. Analyses at the intra‐grain scale (cathodoluminescence scanning electron microscopy, electron probe microanalysis), at the single grain scale (SIMS), at the sample layer scale (EPMA, laser ablation‐ICP‐MS) and at the bulk scale (ICP‐OES) demonstrated acceptable homogeneity at sample volumes characteristic of most microanalysis techniques and show that nanoporous silica gel holds promise as a highly retentive doping substrate for preparing reference materials for laser‐, electron‐ and ion‐beam microanalysis.     

西南三江甘孜-理塘洋晚古生代构造演化：来自理塘蛇绿混杂岩堆晶辉长岩U-Pb年龄的约束

理塘县高城镇西北的擦岗隆洼岩组是一套以玄武岩为基质的蛇绿混杂岩,通过该蛇绿混杂岩中堆晶辉长岩的LA-ICP-MS 锆石U-Pb定年,显示其年龄范围介于349 ~ 274 Ma之间,形成2个年龄组：第一组斜锆石206Pb/238U年龄加权平均值为346±17 Ma,代表堆晶辉长岩早期岩浆活动的时代;第二组斜锆石206Pb/238U年龄加权平均值为286.2±5.1 Ma,代表了堆晶辉长岩晚期岩浆活动的结晶年龄。擦岗隆洼岩组的超基性—基性岩具有N-MORB（正常洋中脊玄武岩）和E-MORB（富集型洋中脊玄武岩）组合特征,指示这些岩石可能形成于洋中脊环境,岩浆物质源自N-MORB所代表的亏损上地幔源区受地幔柱交代混染后而形成的混合源区。研究认为,甘孜−理塘洋最早可能在中泥盆世,受区域地幔柱活动影响开始拉张,导致中咱地块从扬子陆块西缘裂离,并在早石炭世发育形成洋盆。在中晚三叠世甘孜−理塘洋壳开始向西俯冲,并于晚三叠世末闭合,区域进入弧陆碰撞造山阶段。     

Sodic Pyroxene and Sodic Amphibole as Potential Reference Materials for In Situ Lithium Isotope Determinations by SIMS

Two large pegmatitic crystals of sodic pyroxene (aegirine) and sodic amphibole (arfvedsonite) from the agpaitic igneous Ilímaussaq Complex, south Greenland were found to be suitable as reference materials for in situ Li isotope determinations. Lithium concentrations determined by SIMS and micro‐drilled material analysed by MC‐ICP‐MS generally agreed within analytical uncertainty. The arfvedsonite crystal was homogeneous with [Li] = 639 ± 51 μg g^?1 (2s, n = 69, MC‐ICP‐MS and SIMS results). The aegirine crystal shows strongly developed sector zoning, which is a common feature of aegirines. Using qualitative element mapping techniques (EPMA), the homogeneous core of the crystal was easily distinguished from the outermost sectors of the crystals. The core had a mean [Li] of 47.6 ± 3.6 μg g^?1 (2s, n = 33) as determined by SIMS. The seven micro‐drilled regions measured by solution MC‐ICP‐MS returned slightly lower concentrations (41–46 μg g^?1), but still overlap with the SIMS data within uncertainty. Based on MC‐ICP‐MS and SIMS analyses, the variation in δ⁷Li was about 1‰ in each of the two crystals, which is smaller than that in widely used glass reference materials, making these two samples suitable to serve as reference materials. There was, however, a significant offset between the results of MC‐ICP‐MS and SIMS. The latter deviated from the MC‐ICP‐MS results by ?6.0 ± 1.9‰ (2s) for the amphibole and by ?3.9 ± 1.9‰ (2s) for the aegirine. This indicates the presence of a significant matrix effect in SIMS determinations of Li isotopes for amphibole and pyroxene relative to the basalt glasses used for calibration. Based on the MC‐ICP‐MS results, mean δ⁷Li values of +0.7 ± 1.2‰ (2s, n = 10) for the arfvedsonite crystal and of ?3.7 ± 1.2‰ (2s, n = 7) for the core of the aegirine crystal were calculated. Adopting these values, SIMS users can correct for the specific IMF (instrumental mass fractionation) of the ion probe used. We propose that these two crystals serve as reference materials for in situ Li isotope determinations by SIMS and pieces of these two crystals are available from the first author upon request.     

PRELIMINARY STUDY ON THE OPHIOLITIC MELANGE IN THE YALU TSANGPU GRAND CANYON AREA

PRELIMINARY STUDY ON THE OPHIOLITIC MELANGE IN THE YALU TSANGPU GRAND CANYON AREA     

Iron Isotopic Compositions of Geological Reference Materials and Chondrites

High‐precision iron isotopic compositions for Fe‐bearing geological reference materials and chondrites with a wide range of matrices (e.g., silicates, oxides, organic‐bearing materials) are reported. This comprehensive data set should serve as a reference for iron isotopic studies across a range of geological and biological disciplines for both quality assurance and inter‐laboratory calibration. Where comparison is available, the iron isotopic compositions of most geological reference materials measured in this study were in agreement with previously published data within quoted uncertainties. Recommendations for the reporting of future iron isotopic data and associated uncertainties are also presented. Long‐term repeat analyses of all samples indicate that highly reproducible iron isotopic measurements are now obtainable (± 0.03‰ and ± 0.05‰ for δ⁵⁶Fe and δ⁵⁷Fe, respectively).     

西天山特克斯一带双变质带特征

特克斯一带双变质带是西天山双变质带重要组成部分.对特克斯一带双变质带特征的详细观察和讨论,可能对整个西天山双变质带深入研究起到解剖麻雀的作用.低压相系变质岩是以堇青石片岩类为代表;高压相系变质岩是以蓝闪石片岩类为代表.在后继的收缩体制下,由于陆-陆碰撞作用,使能干性不同的层状变质岩叠置到一起,经过强烈纵向构造置换作用,使能干性较强的蓝闪石片岩类(包括大理岩)变成透镜状、似层状岩石,嵌在数量较多、能干性较弱的堇青片岩类里,构成双变质带混杂体.变质作用的时间约为晚志留世末.堇青石片岩类为低压相系角闪岩相岛弧型变质作用;蓝闪石片岩类属于高压相系低绿片岩相俯冲带型变质作用.