华北克拉通南缘中条山-嵩山地区1.78Ga基性岩墙群的地球化学特征及构造环境

幔源岩浆侵位产生的基性岩墙群是地壳伸展裂解的重要标志。华北克拉通南缘中条山-嵩山地区出露有大量的中元古代基性岩墙群,对其研究将有助于深入了解华北克拉通中元古代构造演化特征。其岩石类型以辉绿岩为主,少量辉长辉绿岩和辉绿玢岩;主要造岩矿物为斜长石和单斜辉石,其它矿物包括角闪石、Fe-Ti氧化物、磷灰石、黑云母、碱性长石和石英。锆石SHRIMPU-Pb年龄为1785±18Ma,代表岩墙的结晶年龄。岩石K2O+Na2O含量为3.63%～6.18%,K2O/Na2O比值为0.73～1.38,FeOT含量较高(10.03%～13.59%),属于拉斑玄武岩系列。岩石的稀土元素含量高(142×10-6～381×10-6),亏损Nb、Ta、Zr、Hf等高场强元素,富集Rb、Ba、La等大离子亲石元素,全岩εNd(t)值为-6.2～-8.1。岩墙的固结指数(SI)和MgO含量呈明显的正相关关系,说明幔源岩浆发生过明显的结晶分异作用。地球化学分析表明,研究区基性岩墙属于板内拉斑玄武岩系列,与熊耳群火山岩有相似的地球化学特征;基于两者紧密的产出关系,我们认为该区岩墙可能是熊耳群火山岩的通道岩墙,共同代表了华北克拉通东、西陆块碰撞后伸展事件。     

辽宁盖县梁屯—矿洞沟碱性正长岩杂岩体的U—Pb和Sm—Nd年龄及其地质意义

辽宁梁屯 -矿洞沟杂岩体主要由辉石正长岩、霓辉正长岩和霓辉角闪正长岩等碱性岩石组成 ,具有全岩 Rb- Sr等时线年龄 186 6± 115 Ma和 ISr=0 .70 4 9的同位素特征 ,是我国目前报道的最古老的碱性正长岩类。本文报道了该岩体的锆石U- Pb和全岩 Sm- Nd同位素测试资料 ,获得了锆石 U- Pb同位素年龄为 185 7± 2 0 Ma、Sm- Nd等时年龄为 1787± 180 Ma、εNd(t) =- 4 .8～ - 5 .0的数据。它们反映出该杂岩体形成年龄的上限为 185 7± 2 0 Ma、下限不小于 1787± 180 Ma,来源于富集地幔物质。基于这些数据并结合区域地质资料分析 ,作者提出了华北地台北缘古元古宙存在有富集地幔储库 ,以及辽河群主体形成于 190 0 Ma以前的认识     

Geochemical characterization of surface water and spring water in SE Kashmir Valley,western Himalaya: Implications to water–rock interaction

Water samples from precipitation, glacier melt, snow melt, glacial lake, streams and karst springs were collected across SE of Kashmir Valley, to understand the hydrogeochemical processes governing the evolution of the water in a natural and non-industrial area of western Himalayas. The time series data on solute chemistry suggest that the hydrochemical processes controlling the chemistry of spring waters is more complex than the surface water. This is attributed to more time available for infiltrating water to interact with the diverse host lithology. Total dissolved solids (TDS), in general, increases with decrease in altitude. However, high TDS of some streams at higher altitudes and low TDS of some springs at lower altitudes indicated contribution of high TDS waters from glacial lakes and low TDS waters from streams, respectively. The results show that some karst springs are recharged by surface water; Achabalnag by the Bringi stream and Andernag and Martandnag by the Liddar stream. Calcite dissolution, dedolomitization and silicate weathering were found to be the main processes controlling the chemistry of the spring waters and calcite dissolution as the dominant process in controlling the chemistry of the surface waters. The spring waters were undersaturated with respect to calcite and dolomite in most of the seasons except in November, which is attributed to the replenishment of the CO₂ by recharging waters during most of the seasons.     

Long-term trends of seasonal dusty day characteristics—West Iran

In order to examine the seasonal characteristics of the dust events over western parts of Iran, surface observations from 27 meteorological stations for the period 1951–2014 were analyzed to obtain spatial distributions and temporal variations and trend of dusty day frequency (DDF). Trends of DDF were analyzed by Mann–Kendall and Sen’s estimator of slope nonparametric statistics. Three meteorological stations were selected in north (Tabriz), middle (Kermanshah), and south of the study area (Ahwaz) as reference stations for detecting the regional differences of DDFs. The results showed that DDF is a variable season by season but in general, DDF increases from north to south and from east to west of Iran. The maximum of DDF is monitored in May, June, and July. There are tangible seasonal increasing–decreasing periods in which these changes are logically related with seasonal changes. Regardless of the existence of the maximum DDF in south and southwest of study area, the most intensive increasing DDF trend is calculated in west middle areas. The most widespread and intensive increasing DDF pattern in west of Iran is observed when it is spring. In this case, the dust storms replaced the rainfalls. Distance from dust sources, major movement ways of dust transporting synoptic systems, regional effective wind activity (such as Shamal wind), and arrangement of high mountains are the known factors affecting frequency variation, distribution, and rate of the trend of all the dust phenomena in west of Iran.     

Boron isotopic fractionation during seawater evaporation

Laboratory experiments were undertaken to investigate the behaviour of boron at the seawater–air interface during seawater evaporation. Seawaters adjusted to different pH values were heated to 27, 33 and 40 °C inside a quartz evaporator. The vapor was collected with a quartz condenser using a cold trap. A natural seawater–vapor process in quiet air conditions and excluding the sea-spray component was realized using this arrangement. The results indicate an enrichment of ¹¹B in the condensate. This implies that in the natural environment, rainfall with δ¹¹B values lower than that of seawater has been affected either by continental boron sources or by the boron extracted from seawater under airflow conditions. While the net flux of boron carried away from the ocean by air masses due to seawater evaporation is significant compared to other fractionation-associated processes removing boron from the ocean, the effect of isotopic fractionation as boron enters the vapor phase on the isotopic composition of boron in the ocean over time is small.     

Assessing variability of water quality in a groundwater-fed perennial lake of Kashmir Himalayas using linear geostatistics

This paper presents a study on Manasbal lake, which is one of the high altitude lakes in the Kashmir Valley, India. Eighteen water samples were analysed for major ions and trace elements to assess the variability of water quality of the lake for various purposes. Geostatistics, the theory of regionalized variables, was then used to enhance the dataset and estimate some missing spatial values. Results indicated that the concentration of major ions in the water samples in winter was higher than in summer. The scatter diagrams suggested the dominance of alkaline earths over the alkali elements. Three types of water were identified in the lake that are referred to as Ca–HCO₃, Mg–HCO₃ and hybrid types. The lake water was found to be controlled by rock–water interaction with carbonate lithology as a dominant source of the solutes. The major (Ca^2 +, Mg^2 +, Na⁺, K⁺, NO₃ and HCO₃^-{\rm{HCO}}_{3}^{-}, CO₃ and Cl) and trace elements of the lake water were within the World Health Organization standards, therefore the lake water was considered chemically safe for drinking purposes. Although NO₃ concentration (ranging from 1.72 to 2 mg/L), is within the permissible limit and not very alarming, the gradually increasing trend is not acceptable. It is however, important to guard its spatio-temporal variability as the water is used for domestic as well as agricultural purposes. This study is significant as hydrogeological information on such high altitude lakes in India is scanty.     

Deterministic Approach for the Seismic Microzonation of Bucharest

— The mapping of the seismic ground motion in Bucharest, due to the strong Vrancea earthquakes is carried out using a complex hybrid waveform modeling method which combines the modal summation technique, valid for laterally homogeneous anelastic media, with finite-differences technique, and optimizes the advantages of both methods. For recent earthquakes, it is possible to validate the modeling by comparing the synthetic seismograms with the records. We consider for our computations the frequency range from 0.05 to 1.0 Hz and control the synthetic signals against the accelerograms of the Magurele station, low-pass filtered with a cut-off frequency of 1.0 Hz of the 3 last major strong (M_w > 6) Vrancea earthquakes. Using the hybrid method with a double-couple seismic source approximation, scaled for the source dimensions and relatively simple regional (bedrock) and local structure models, we succeeded in reproducing the recorded ground motion in Bucharest at a satisfactory level for seismic engineering. Extending the modeling to the entire territory of the Bucharest area, we construct a new seismic microzonation map, where five different zones are identified by their characteristic response spectra.     

海水蒸发时的硼同位素分馏

采用立式亚沸石英蒸馏器，在非流动条件下进行了海水蒸发实验，以研究海水一空气界面硼同位素的行为。将具有不同pH值的天然海水在不同温度下平静地蒸发，采用冷水收集海水蒸汽，实现了无流动空气的真实的蒸发过程，共进行了3种类型的实验。 实验1 将不同pH值（(7.71-8.49)的海水在27℃，33℃和40℃下蒸发，蒸发时连续地补充高纯水以维持蒸发液体的体积恒定。收集海水蒸汽，进行蒸汽的硼同位素组成、硼和氯浓度的测定。 实验2将天然海水在33℃下蒸发，蒸发时不补加高纯水．搏派承药蒸干。分捌收集海水蒸汽和蒸干后的固体盐，进行蒸汽和固体盐的硼同位素组成测定。并同时测定不同蒸发阶段海水的pH值。 实验3 将加人不同硼量的天然海水在40℃下蒸发.蒸发时连续地补充高纯水以维持蒸发液体的体积恒定，收集海水蒸汽，进行硼同位素和硼浓度的测定。 硼浓度的结果表明：①在实验1中，蒸汽的硼浓度变化范围是1.51-10.7 μg/L，平均值为5.16 μg/L，随海水pH值升高而降低，但与蒸发温度无关；②在实验2和3中蒸汽硼的浓度要远远高于实验1，而且蒸汽硼浓度与海水硼浓度具有线性的正相关关系；③蒸汽相的Cl/B比（摩尔比值：平均23.4)远远低于海水的Cl/B比（摩尔比值：1485)，这表明蒸发时没有将海水喷雾的细珠引人蒸汽中。 硼同位素结果表明： (1)在实验1中，蒸汽的δ11B值除一个以外均低于海水B(OH)3的δ11B值，而高于海水B(OH)4-的δ11B值，而且都比海水的δ11B值高，蒸汽与海水间的平均硼同位素分馏系数为1.0019，这表明在海水蒸发时，11B富集在蒸汽相中。此结果与以前所进行的硼溶液蒸发实验结果一致，但与以前所进行的海水蒸发实验结果完全相反。以前的海水蒸发实验结果表明，10B在蒸汽相富集。这种截然相反的结果要归结于蒸发条件的差异，以前蒸发的海水蒸汽是由流动空气带出，此时非平衡的动力因素将起到重要作用，造成质量轻的10B优先进人蒸汽相。而本次实验在非空气流动条件下进行，B(OH)3和B(OH)-4间的同位素平衡将起主导作用。显然，燕汽的δ11B值与海水的pH值没有明显的关系。 (2)在实验2中，蒸汽与海水间的硼同位素分馏系数要远远高于实验1，特别当海水蒸干前的500 mL蒸汽，分馏系数高达1.0182。而蒸干后的固体盐的δ11B值明显低于原始海水，分馏系数为0.9973。这充分表明，在海水蒸发时，11B优先被蒸发而进人燕汽相。海水蒸发时蒸汽相的δ11B值随蒸发程度呈平方指数形式增加，这与蒸发时残留海水的δ11B值急剧升高有关。 (3）实验3中，蒸汽的δ11B值随海水硼浓度的增加而升高，当硼浓度为19.7 μg/mL和63.5 μg/mL时，硼同位素分馏系数分别为1.0072和1.0107。 海水蒸发时的硼同位素分馏可用于对大气降雨硼来源的研究。在不同时期采集的西宁雨水的δ11B值为12.1‰和9.0‰，受风向的影响甚微，表明西宁地区的大气环境受海洋影响较小，大气中的硼主要来源于陆地。但南海西江石油平台大气降雨的δ11B值明显受风向所控制，高δ11B值（33.2‰）表明其海洋来源，而低δ11B值（8.4‰）表明其陆地来源。以往文献所报道的陆地及其沿海大气降雨的δ11B值变化范围很宽(0.8‰~35‰)，但是它们都低于海水的δ11B值，这表明陆地及其沿海大气中的硼主要来源于陆地。 海水中的硼将因洋壳低温蚀变、沉积物吸附以及生物碳酸盐共沉淀从海洋中迁出，这些过程均造成海水10B的贫化。惟独海水蒸发时会造成海水10B的富集，但由于此时硼同位素分馏小，而且与其他因素相比，被海水蒸汽迁出的硼量低，根据计算，海水燕发对古海洋硼同位素组成的影响完全可以忽略不计。     

硼特效树脂离子交换法分离B的研究

本文对Amberlite IRA 743 硼特效树脂交换分离B的特征及其影响因素进行了研究。它适用于各种地质样品中B的分离提取，特别是在B同位素地球化学研究时必须进行B纯化的场合。