古尔班通古特沙漠风沙活动特征与线形工程安全研究

古尔班通古特沙漠是我国第二大沙漠，沙丘类型以固定和半固定纵向沙垄为主。垄间和坡中下部沙面较为稳定，仅在沙垄顶部存在10—40m宽度不等的流动带，风沙活动规律独特。近年来在沙漠腹地修筑的公路、引水渠等线形工程，不可避免地造成沙垄切剖和保护层破环，所引发的工程安全问题引起了人们的普遍关注。通过风况分析和实地观测，对沙漠腹地风沙活动特征进行了初步研究，同时对线形工程风沙危害进行监测，在此基础上提出现有防护体系存在的主要问题与对策。     

基于VOSviewer的塔克拉玛干沙漠沙尘暴研究文献分析

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...     

Laboratory simulation of salt weathering processes in arid environments

The equipment and techniques being used at Bedford College, London to simulate salt weathering processes in deserts are described in the context of a general discussion of the nature of salt weathering processes and approaches to studying them. An experiment based on the equipment and techniques is described: it is designed to test the durability of three building stones in the presence of several different saline solutions under conditions of surface temperature and relative humidity that are considered typical of hot deserts. The experiment, the first of a series, shows that Na₂SO₄ is the most effective of the salts used, and that susceptibility of the rocks to weathering is related to such rock properties as porosity, microporosity and water absorption capacity.     

萨拉乌苏河流域MGS1层段粒度与CaCO3记录的全新世千年尺度的气候变化

 毛乌素沙漠东南缘萨拉乌苏河流域米浪沟湾剖面MGS1层段含有11个由古沙丘砂与河湖相或古土壤构成的沉积旋回。通过对该层段粒度和CaCO3的分析,发现其河湖沼相和古土壤的平均粒径、分选系数、偏度和峰态的值明显高于古沙丘砂;CaCO3含量在古沙丘砂及其上覆的河湖相和古土壤中依次变化于0.07%~0.32%（平均值为0.16%）、0.05%~1.50%（0.27%）和0.06%~1.42%（0.64%）,并与平均粒径呈显著相关（相关系数0.8）;构成与沉积旋回波动韵律相同的11个峰谷交替的粒度和CaCO3旋回,指示了全新世气候冷、暖的变化过程和东亚冬夏季风千年尺度交替变化的气候旋回。这些旋回中的冬季风主导时期可与北大西洋8 200、5 000、4 000、2 700、1 400 a BP等寒冷事件进行对比,和中国若干地点的气候波动具有良好对应关系,可能表明全新世东亚季风在全球大气、海洋、陆地和全球冰量变化的共同作用下,表现为干冷冬季风和暖湿夏季风的相互交替的千年尺度的气候变化特征。     

Mineralogy,geochemistry and age dating of shear zone-hosted Nb-Ta-, Zr-Hf-, Th-, U-bearing granitic rocks in the Ghadir and El-Sella areas,South Eastern Desert,Egypt

The rare metal minerals of mineralized altered granites within the Ghadir and El-Sella shear zones, are represented by betafite, U-minerals (uraninite and uranophane), zircon, monazite, xenotime, and rutile in the Ghadir shear zone. While they are columbite-tantalite minerals as ferrocolumbite, pyrochlore, and fergusonite, Th-minerals (cheralite, uranothorite, and huttonite monazite), Hf-zircon, monazite and xenotime in the El-Sella shear zone. Hf-zircon in the El-Sella and Ghadir shear zones (increasing from the core to the rim) contains high inclusions of U-Th, and REE minerals such as cheralite, uranothorite, huttonite monazite and xenotime especially in the El Sella shear zone. The rare-metal minerals, identified from peralkminous granites of the shear zones are associated with muscovite, quartz, chlorite, fluorite, magnetite, and biotite that are restricted to the two shear zones. Uraninite (low Th content) occurring in the Ghadir shear zone indicates the hydrothermal origin, but there are thorite, uranothorite, cheralite, and Hf-zircon in the El Sella shear zone, also indicating the hyrothermal proccess after magmatic origin. Compositional variations of Ta/(Ta+Nb) and Mn/(Mn+Fe) in columbite from 0.07-0.42 and 0.04-0.33, respectively, and Hf contents in zircon are so high as to be 12%, especially in the rim in the El Sella shear zone. This feature re-flects the extreme degree of magmatic fractionation. Four samples from the altered granites of the Ghadir shear zone also are very low in TiO2 (0.04 wt%-0.17 wt%), Sr [(82-121)×10-6], and Ba [(36-380)×10-6], but high in Fe2O3T (0.46 wt%-0.68 wt%), CaO (0.64 wt%-1.23 wt%), alkalis (8.59 wt%-8.88 wt%), Rb [(11-203)×10-6], Zr [(98-121)×10-6], Nb [(9-276)×10-6], Ta [(2-139)×10-6], U [(14-63)×10-6], Th [(16-105)×10-6], Pb [(13-32)×10-6], Zn [(7-8)×10-6], Y [(15-138)×10-6], Hf [(3-9)×10-6], and ∑REE [(81-395)×10-6, especially LREE [(70-322)×10-6]. They are very high in Zr/Hf (15.07-85.96) and Nb/Ta (7.17-21.48), and low in Rb/Sr (2.56-3.36) and Th/U (0.096-3.36). Four samples of the altered granites from the El Sella shear zone are very low in TiO2 (0.23 wt%-0.38 wt%), Sr [(47-933)×10-6], and Ba [(82-175)×10-6] , with high Fe2O3T (1.96 wt%-2.87 wt%), CaO (0.43 wt%-0.6 wt%), alkalis (4.46 wt%-10.7 wt%), Rb [(109-313)×10-6], Zr [(178-1871)×10-6], Nb [(11-404)×10-6], U [(56-182)×10-6], Th [(7-188)×10-6], Ta [(0.5-57)×10-6], Pb [(12-28)×10-6], Zn [(1-13)×10-6], Y [(62-156)×10-6], Hf [(3-124)×10-6], and ∑REE [(101-184)×10-6], especially HREE [(7-139)×10-6]. This is consistent with the very fractionated, fluorine-bearing granitic rocks that were altered and sheared in the El Sella shear zone. Zr/Hf (14.23-39.79) and Nb/Ta (1.98-7.01) are very high, and Rb/Sr (0.14-1.7) and Th/U (0.25-2.5) are low in the Ghadir shear zone. Field evidence, textural relations, and the composi-tion of ore minerals suggest that the main mineralizing event was magmatic (615+/-7 Ma, and 644+/-7 Ma CHIME monazite), especially in the El Sella shear zone, with later hydrothermal alteration and local remobilization of the high-field-strength elements.     

腾格里沙漠东南缘生物土壤结皮对土壤理化性质的影响

生物土壤结皮是荒漠生态系统地表景观的重要组成部分,在沙化土地恢复和流沙固定中起着重要作用。研究了腾格里沙漠东南缘固沙植被区不同类型生物土壤结皮理化性质及结皮发育对下层土壤性质的影响。结果表明：结皮层厚度、孔隙度、黏粉粒和田间持水量以及有机碳、无机碳、全氮、碱解氮、速效磷、速效钾含量和电导率均表现为藓类结皮 > 混生结皮 > 地衣结皮 > 藻类结皮;砂粒含量和容重表现为藻类结皮 > 地衣结皮> 混生结皮 > 藓类结皮。结皮下0~2 cm和2~5 cm土层理化性质表现出与结皮层相同的变化规律。总体上,生物土壤结皮对下层土壤理化性质的影响表现为藓类结皮和混生结皮大于地衣结皮和藻类结皮;而结皮对下层土壤理化性质的影响随土壤深度的增加而减小。生物土壤结皮的拓殖和发育是荒漠生态系统成土过程和土壤质量的关键影响因素。     

腾格里沙漠沙坡头地区固沙植被对生物多样性恢复的长期影响

地处腾格里沙漠东南缘的沙坡头人工固沙植被始建于1956年,46 a来不仅确保了包兰铁路沙漠地段的畅通无阻,而且对区域生态环境的恢复产生了巨大的影响,成为我国干旱沙漠地区交通干线荒漠化防治与生态恢复的成功模式。长期定位监测结果表明:人工固沙植被建立4~5 a后,沙丘表面物理结构初步得到稳定,并由大气降尘形成的无机土壤结皮逐渐演变形成土壤微生物结皮。荒漠藻类、苔藓和地衣等隐花植物在结皮层中得到了大量的繁衍:固沙植被建立46 a后出现藻类24种;苔藓仅有5 种,少于天然固定沙丘结皮上的种类,此外,地衣也在植被区发现,这说明固定沙丘景观逐渐趋于稳定的状态;相对于流沙区,固沙植被区近地面风速降低了 40%,土壤有机质含量增加了60%,其中氮、磷、钾等荒漠生态系统主要限制养分因子及土壤理化性质得到了改善,沙丘表层成土过程明显;土壤水分循环的时空变异驱动了植被的演变,为大量的草本的侵入和定居创造了条件;此外,对鸟类、昆虫和土壤动物及荒漠动物的生存产生了积极的影响。46 a后,固沙植被区共有鸟类 28 种,昆虫 50 种,动物 23种。生物多样性的恢复使原有的相对单一的固沙植被演变成一个结构、组成和功能相对复杂的荒漠生态系统。沙坡头地区生态环境在人为促进下的恢复为我国西部生态建设提供了科学依据。     

塔克拉玛干沙漠地表潜热时空特征分析

利用1979年3月至2004年2月月平均的NCEP/DOE再分析地表潜热资料,在分析塔克拉玛干沙漠四季潜热基本气候特征的基础上,通过EOF方法,对沙漠地表潜热异常变化的空间结构和时间演变趋势作了诊断研究。结果表明：①沙漠地区夏季潜热最大,春季和秋季次之,冬季最小;靠近山区的沙漠西部、西北部地区四季明显大于中、东部地区。②根据四季地表潜热距平场的EOF分析,该区潜热异常主要有全区一致型、南北差异型以及西北—东南差异型三种常见的分布模态。③25 a期间,塔克拉玛干沙漠地表潜热在第一空间尺度上四季都有不同程度增强的趋势;在第二空间尺度上,春季沙漠北部、西北部有减弱的趋势,南部、东南部有增强的趋势,而冬、夏、秋季变化趋势不是很大。     

库布齐沙漠南缘抛物线形沙丘表面风沙流结构变异

对库布齐沙漠南缘抛物线形沙丘表面气流和输沙率的野外观测和分析结果表明,沙丘表面约90%的风沙输移集中在距沙面0.10 m高度范围内,输沙率随高度递减的形式在沙丘各部位因风速、下垫面状况和坡面形态不同而发生变异。沙丘迎风坡坡脚因出露坚硬、含砾石地表,颗粒跃移高度大,风沙流上层相对输沙率大;迎风坡沙粒沿坡向上运动,颗粒跃移高度减小,风沙流中近地表相对输沙率大;沙丘背风坡沙粒沿坡向下运动,加之来自丘顶变型跃移物质的影响,风沙流上层相对输沙率较大;脊线受迎风坡各个断面地形差异的影响,各观测点间风沙流结构差异显著。风沙流结构在迎风坡和丘顶均遵循指数递减规律(Q=aexp(-z/b)),其中,指数函数拟合中系数a与输沙率具有良好的幂函数关系,随风速增加而增加,但二者关系较弱;b与二者无相关性。背风坡风沙流结构具有明显的分段现象,以0.10 m高度为界,下层符合指数函数,上层符合幂函数。     

Cryogenian ophiolite tectonics and metallogeny of the Central Eastern Desert of Egypt

The Central Eastern Desert (CED) is characterized by the widespread distribution of Neoproterozoic intra-oceanic island arc ophiolitic assemblages. The ophiolitic units have both back-arc and forearc geochemical signatures. The forearc ophiolitic units lie to the west of the back-arc related ones, indicating formation of an intra-oceanic island arc system above an east-dipping subducted slab (present coordinates). Following final accretion of the Neoproterozoic island arc into the western Saharan Metacraton, cordilleran margin magmatism started above a new W-dipping subduction zone due to a plate polarity reversal. We identify two belts in the CED representing ancient arc–forearc and arc–back-arc assemblages. The western arc–forearc belt is delineated by major serpentinite bodies running ～NNW–SSE, marking a suture zone. Ophiolitic units in the back-arc belt to the east show an increase in the subduction geochemical signature from north to south, culminating in the occurrence of bimodal volcanic rocks farther south. This progression in subduction magmatism resulted from diachronous opening of a back-arc basin from north to south, with a bimodal volcanic arc evolving farther to the south. The intra-oceanic island arc units in the CED include coeval Algoma-type banded iron formations (BIFs) and volcanogenic massive sulphide (VMS) deposits. Formation of the BIFs was related to opening of an ocean basin to the north, whereas development of the VMS was related to rifting of the island arc in the south. Gold occurs as vein-type mineral deposits, concentrated along the NNW–SSE arc–forearc belt. The formation of these vein-type gold ore bodies was controlled by the circulation of hydrothermal fluids through serpentinites that resulted in Au mobilization, as constrained by the close spatial association of auriferous quartz veins with serpentinites along the western arc–forearc belt.