Using Portable Gamma-Ray Spectrometry for Testing Uranium Migration: A Case Study from the Wadi El Kareim Alkaline Volcanics, Central Eastern Desert, Egypt

The 300±20 Ma anomalously radioactive trachytes of Wadi El Kareim, central Eastern Desert, are a significant example of U-mineralization related to the alkaline volcanics in Egypt. Extensive portable gamma-ray spectrometric data has been utilized to identify geological factors controlling uranium mobility in the geological units along the three detailed study locations of Kab Al-Abyad, South Wadi (W) Al-Tarafawy and W. Al-Farkhah; their eTh/eU ratios averaging around 4.1, 3.7 and 5.6 respectively. Quantitative analysis with the integration of mobility maps and geological studies suggest two systems controlling U-migration within the geological units (confined system and unconfined system). In the confined system, the syngenetically formed U have experienced mobility after leaching and are redistributed in the presence of an incorporation carrier during transportation (probably as carbonate complexes). Then the retardant for uranium is achieved by sorption or by coprecipitation with the aid of Fe oxy-hydroxide, and finally the formation of immobile secondary U-bearing minerals takes place along a lithogeochemical trap. In contrast to the confined system, the unconfined one is basically lacking the lithogeochemical trap which in?uences the final accumulation of U-bearing minerals. The radioactivity of the trachyte rocks arises from the radioactive minerals uranophane and beta-uranophane with U- and/or Th-bearing minerals samarskite, Th-rich REE silicates, monazite and allanite.     

Characteristics of UV radiation at Tazhong of the Tarim Basin,west China

Tazhong station, located at the hinterland of the Taklimakan Desert in northwest China, experiences frequent dusty weather events during spring and summer seasons (its dusty season) caused by unstable stratified atmosphere, abundant sand source and strong low-level wind. On average, it has 246.2 dusty days each year, of which 16.2 days are classified as sand and dust storm days. To better understand the characteristic of solar ultraviolet (UV) radiation and factors influencing its variations under such an extreme environment, UV radiation data were collected continuously from 2007 to 2011 at Tazhong station using UVS-AB-T radiometer by Kipp and Zonen. This study documents observational characteristics of the UV radiation variations observed during the five-year period. Monthly UV radiation in this region varied in the range of 14.1–37.8 MJ m^?2 and the average annual amount was 320.7 MJ m^?2. The highest value of UV radiation occurred in June (62.5 W m^?2) while the lowest one in December (29.3 W m^?2). It showed a notable diurnal cycle, with peak value at 12:00–13:00 LST. Furthermore, its seasonal variation exhibited some unique features, with averaged UV magnitude showing an order of summer > spring > autumn > winter. The seasonal values were 37.0, 29.1, 24.9 and 15.9 MJ m^?2, respectively. In autumn and winter, its daily variations were relatively weak. However, significant daily variations were observed during spring and summer associated with frequent dust weather events occurring in the region. Further analysis showed that there was a significant correlation between the UV radiation and solar zenith angle under different weather conditions. Under the same solar zenith angle, UV radiation was higher during clear days while it was lower in sand and dust storm days. Our observations showed that there was a negative correlation between UV radiation and ozone, but such a relationship became absent in dusty days. The UV radiation was reduced by 6 % when cloud amount was 1–4 oktas, by 12 % when the cloud amount was 5–7 oktas, and by 24 % when the cloud amount was greater than 8 oktas. The relative reduction of UV radiation reached 26, 38, and 45 % in dust day, blowing sand day and sand and dust storm day, respectively. The results revealed that decrease in UV radiation can be attributed to cloud coverage and dust aerosols. Moreover, the reduction of UV radiation caused by dust aerosols was about 2–4 times greater than that caused by cloud coverage. These observational results are of value for improving our understanding of processes controlling UV radiation over sand desert and developing methods for its estimation and prediction.     

2009年8月－10月塔克拉玛干沙漠北缘地表能量收支特征?

利用塔克拉玛干沙漠北缘肖塘陆气相互作用观测站2009年8-10月探测的资料,对该地区能量收支状况进行了初步分析。结果表明：2009年8-10月的平均能量闭合率为78%,闭合差为22%。夏季白天,感热、潜热、土壤热通量各占净辐射的52%、6%、16%,夜间依次占净辐射的53%、3%、6%。夏季白天、夜间能量不平衡率分别为26%、38%。8月肖塘的总体输送系数CD平均值为4.5×10-3,CH为2.2×10-3。CD、CH季节变化和日变化显著,都是夏季大于秋季,白天大,夜间小。     

新疆沙尘暴研究进展

沙尘暴是风蚀荒漠化中的一种天气现象,既是加速土地荒漠化的重要过程,又是土地荒漠化发展到一定程度的具体体现.新疆地处我国西北干旱、半干旱区,是我国荒漠化土地最多的省区,也是风沙危害最严重的地区之一.重点论述了新疆地区沙尘暴的若干研究进展,从6个方面对沙尘暴的形成及研究现状进行综述,即新疆沙尘暴气候背景、长期变化趋势、分布...     

脉冲星参数统计和演化

统计分析了目前发现的几种脉冲星的自转周期和表面磁场以及空间的分布情况,揭示出毫秒脉冲星比普通射电脉冲星、LMXB(低质量X射线双星)比HMXB(高质量X射线双星)的空间分布要更加弥散;孤立毫秒脉冲星自转周期分布的峰值为4.7 ms,而普通脉冲星的相应值为0.6 s,双星中毫秒脉冲星这一值为3.5 ms; FERMI脉冲...     

Exploring Placer Gold Deposits through Integrated Geophysical and Geochemical Techniques at the Confluence of the Indus and Kabul Rivers, NW Pakistan

Analysis of the anomalous magnetic mineral intensities and geochemistry for placer gold deposits are presented for those of the Attock area at the confluence of the Indus and Kabul rivers in northwestern Pakistan. Two grids covering an area of 10x18 m2 and 8x10 m2 were analyzed using a G-858 Cesium Vapor Magnetometer. The anomalous zones obtained were plotted on contour maps, 2D and 3D magnetic intensity maps. Based on the magnetic anomalies, grid-1 of the study area was sampled at three different anomalous zones for geochemical analysis. These zones contain gold concentrations, ranging from 2.11 ppm to 6.109 ppm with an average of 4.01 ppm. Increase in gold concentration in the subsurface within the anomalous zones indicates that magnetometer survey followed by a geochemical analysis can potentially narrow down the gold-bearing anomalous zones.     

Three-Dimensional Structural Modelling and Source Rock Evaluation of the Quseir Formation in the Komombo Basin, Egypt

The Quseir Formation consists mainly of dark gray mudstones with a high organic matter content and excellent hydrocarbon-generating potential. The main objectives of this study are to highlight the dominant structural elements in the Komombo Basin, Egypt, and evaluate the geochemical characteristics of the Quseir Formation. Depth maps and a 3D structural model indicate two normal fault trends NW–SE and ENE–WSW. The NW–SE trend is the dominant one that created the primary half-graben system. The depth to the top of the Quseir Formation gradually decreases from the eastern and central parts towards the corners of the basin. The thickness of the Quseir Formation ranges from about 300 to 1000 ft. The 3D facies model shows that the shale has a large probability distribution in the study area, compared with the sandstone and siltstone. The source rock potential varies between good in the western part to very good in the eastern part of the basin. The organic-rich interval is dominated by gas-prone kerogen type III based on TOC and Rock-Eval. The pyrolysis data vitrinite reflectance (%Ro) (0.5–0.74%) and Tmax values (406–454C°) suggest a maturity level that ranges from immature to early maturity stage for hydrocarbon generation.     

基于VOSviewer的塔克拉玛干沙漠沙尘暴研究进展分析

作为中国最大和世界第二大流动沙漠，塔克拉玛干沙漠是我国主要的沙尘暴中心之一，其沙尘天气对当地及周边地区的生产生活会造成巨大影响。利用VOSviewer可视化分析工具，以中国知网（CNKI）数据库和Web of Science核心数据库中塔克拉玛干沙漠沙尘暴相关355篇文献为对象，从发文时间、作者、关键词、期刊来源与学科分布、发文机构（国家）等方面进行可视化与计量分析，进而综述了塔克拉玛干沙漠沙尘暴研究的现状及发展趋势和未来展望。结果表明：塔克拉玛干沙漠沙尘暴研究的中英文文献产出分为2个阶段，即1996—2005年为起步阶段，2006—2020年为稳步发展阶段；塔克拉玛干沙漠沙尘暴的成因、传输特征及发展规律、沙尘暴过程数值模拟预报研究、沙尘天气及沙漠气象等问题受到了国内外众多学者的高度关注；相关论文主要发表在《沙漠与绿洲气象》、《中国沙漠》及Journal of Geophysical Research Atmospheres等期刊，其中《沙漠与绿洲气象》为中文发文量最多的核心期刊，Journal of Geophysical Research Atmospheres为SCI发文量最高的...     

新疆东部黑戈壁地表辐射及能量收支演变特征

新疆东部黑戈壁作为气候恶劣、人迹罕至的生态脆弱区，具有丰富的太阳能资源。利用红柳河陆气相互作用观测站2019年4、7、9月观测资料，分析东疆黑戈壁地表辐射及能量收支演变特征。结果表明：（1）地表辐射及能量收支各分量日变化均为单峰型。就不同季节而言，太阳总辐射和净辐射为夏季>春季>秋季，反射短波辐射为春季>夏季>秋季，地表和大气长波辐射为夏季>秋季>春季。（2）能量收支各分量季节变化明显，感热通量为春季>夏季>秋季，潜热通量为夏季>秋季>春季，地表土壤热通量为秋季>夏季>春季；能量分配在不同季节均以感热为主，地表土壤热通量次之，潜热通量极其微弱。（3）地表反照率日变化均为“U”型，在不同季节表现为春季>秋季>夏季，依次为0.29、0.27、0.26。东疆黑戈壁地表反照率整体较高，这是下垫面为黑色砾石所致。