敦煌戈壁地表风蚀起沙量的计算

利用三种不同的计算方案,根据敦煌地区的观测资料,计算了2002年4月8日沙尘天气过程中戈壁地表的风蚀起沙量(垂直尘粒通量)。结果表明:三种方法的计算结果比较接近;在风蚀起沙较严重的时段内,顺风向沙粒通量和垂直尘粒通量平均值的量级分别为10-4kg·m-1·s-1和10-8kg·m-2·s-1。通过计算结果和观测结果的比较,在地面风蚀起沙物理机制的基础上,讨论了三种计算方案各自的优缺点。     

Geotourism,geoconservation, and geodiversity along the belt and road: A case study of Dunhuang UNESCO Global Geopark in China

Dunhuang UNESCO Global Geopark (DHGG) is rich in geoheritage and contains scientific value for studying the sedimentation environments and paleoclimates of Western China. The Geopark is also notable for its aesthetic, cultural, artistic, and recreational value for tourism development. Since geographer Sven Hedin’s discovery of a yardang landform around Lop Nur in 1903, the area has been heavily studied. After the site was designated a National Geopark, geoconservation and geotourism began to rapidly develop and problems associated with these changes emerged. This study characterizes some of DHGG’s typical geoheritage, existing geoconservation, launched geotourism, and also describes some of the area’s challenges. In addition, the opportunities and challenges of DHGG arising from the construction of the Silk Road Economic Belt and 21st-Century Maritime Silk Road (B&R) are discussed. To benefit the sustainable development of DHGG, it is prudent to continue promoting geodiversity, geoconservation, and geotourism by making use of the advantages brought by the B&R.     

莫高窟顶戈壁偏东风作用下输沙率变化的观测研究

通过一次沙尘暴天气过程对莫高窟顶不同观测点戈壁风沙流结构和输沙率的时空变化特征进行了系统同步观测。观测表明,偏东风条件下,当风速为10 m·s-1时,水平观测方向上存在一个各点输沙率平衡的阶段,即崖顶戈壁至鸣沙山边缘戈壁各观测点的输沙率相当;当风速大于10 m·s-1时,戈壁地表以风蚀搬运作用为主,出现了戈壁向鸣沙山的长距离风沙搬运;当风速小于10 m·s-1时,戈壁沙物质的长距离搬运作用不明显。不同风况及沙源条件下,风沙流结构和输沙特征会发生显著变化。借鉴Lattau输沙率方程,运用风速和输沙率推算各观测点输沙率的时空变化,计算结果表明,在风速为10 m·s-1左右时,窟顶戈壁带的输送效率约为60%。     

甘肃敦煌雅丹地质公园区风蚀气候侵蚀力特征

风蚀气候侵蚀力是潜在风力侵蚀强度的重要表征。基于2013年和2014年风速、降水和空气温度、湿度等气象要素的实地观测数据,对甘肃敦煌雅丹地质公园区的风蚀气候因子指数进行了逐月的计算和分析。结果表明：（1）研究区风蚀气候因子指数为151.98±0.13,是全国的三大极大值区之一;（2）研究区风蚀气候因子指数不同于全国干旱半干旱区基本季节变化特征,夏季最大,春夏季明显高于秋冬季,与新疆和田地区的季节变化特征相似;（3）研究区风蚀气候因子指数具有4—8月持续高值、9月至翌年3月持续低值的月变化特征;（4）风蚀气候因子指数的决定性气象因子是风速,而降水的减弱作用甚微;（5）一般来说,雅丹地貌分布区风蚀气候因子指数≥150。     

The impact of Dunhuang railway construction on land desertification

The area that the railway will cross is a region with the main physiognomies of desert and Gobi, with a most fragile ecological environment. It is also a region that is highly susceptible to man-made disturbance. The construction of railway will intensify soil erosion along the railway line to a certain degree. The map of soil erosion conditions in the section from Liugou to Dunhuang City in the range of 10 km each side along the line was compiled by using the techniques of remote sensing and geographic information system (GIS). Based on analysis of the status of desertification and the influence of the railway construction projects, the changes of the types, intensities and the total amount of the soil erosion caused by the construction were predicted.     

敦煌莫高窟窟顶沙丘移动的初步研究

通过窟顶风沙资料的理论计算和沙丘动态监测，首次提出了窟顶沙丘移动方向为ＳＷ→ＮＥ向，移动方式为盘旋式－慢速稳定型。窟顶沙丘年平均移动量０．４２ｍ／ａ，入窟沙量４２９１ｍ￣３。在近百年内，沙丘不会埋没洞窟，但风沙流的危害仍十分严重。因此防止窟顶风沙流的危害是目前石窟保护中急待解决的重要问题。     

Paleozoic subduction of the southern Dunhuang Orogenic Belt,northwest China: metamorphism and geochronology of the Shuixiakou area

Amphibolites in the Shuixiakou area of the southern Dunhuang Orogenic Belt, southernmost Central Asian Orogenic Belt (CAOB), occur as lenses within hornblende-biotite-plagioclase gneiss or pelitic schist, exhibiting block-in-matrix feature of tectonic mélange. Three generations of metamorphic mineral assemblages (M1, M2, and M3) have been recognized in the garnet-bearing amphibolite lenses. The metamorphic prograde assemblage (M1) is documented with inclusion trails (hornblende + plagioclase + quartz) within garnet porphyroblasts, and are estimated to be formed under 610–690 °C and 6.5–10.2 kbar. The metamorphic peak assemblage (M2) consists of garnet + hornblende + clinopyroxene + plagioclase + quartz in the matrix and records metamorphic peak P-T conditions of 720–750 °C and 13.4–14.7 kbar. The retrograde assemblage (M3) is represented by the symplectic assemblage (hornblende + plagioclase + quartz ± biotite ± magnetite) rimming the garnet porphyroblast, formed in the decompression stage under P-T conditions of 630–730 °C and 3.8–7.2 kbar. The derived metamorphic P-T paths show similar tight clockwise loops including nearly isothermal decompression processes, typical of orogenic metamorphism. SIMS dating of metamorphic zircons from the amphibolites confirm that the high-pressure metamorphism (M2) occurred at ca. 438–398 Ma.     

甘肃敦煌地块基于岩浆岩(氧化物)信息的金找矿靶区定量优选

借用计算机强大的计算处理能力,以判别分析方法构建起甘肃敦煌地块基于化探资料的金找矿定量预测模型和基于岩浆岩(氧化物)信息的金找矿靶区定量优选模型,鉴别出18个与现有金矿床(点)相关关系高度密切的侵入岩体和123个由化探资料确定的金找矿靶区。优选出分布在上述18个岩体5km范围内的金找矿靶区,与化探资料确定的金矿找矿靶区进行综合优选,共选出27个金找矿靶区并分为三级,Ⅰ级靶区5个(其中3个靶区有已知金矿分布,见矿率58.2%),Ⅱ级靶区9个(见矿率33.3%),Ⅲ级靶区13个(见矿率14.8%)。综合信息定量优选的找矿靶区有极高的见矿率,为进一步地质找矿工作提供依据。     

敦煌地块南缘小红山埃达克岩的年代学、地球化学特征及地球动力学意义

敦煌地块南缘小红山花岗岩体侵位于敦煌岩群中,岩性主要为黑云二长花岗岩和黑云花岗闪长岩。通过LA- ICP- MS锆石U- Pb同位素定年,获得小红山黑云母二长花岗岩的206Pb/238U的加权平均年龄为289.6±3.9Ma,表明侵位时代为早二叠世。岩石地球化学分析显示其具有高硅、高铝、富碱和低镁的特征,稀土元素在球粒陨石标准化稀土配分模式图上呈轻稀土富集的右倾型稀土配分模式,弱负Eu异常,富集大离子亲石元素(如Rb、Cs、Th、K、Pb),亏损Nb、Ta、P、Ti等高场强元素,岩石强烈富集Sr、亏损Yb和Y,具有较高的Sr/Y比值,岩石具有与埃达克岩石一致的地球化学特征,是加厚下地壳部分熔融的产物。小红山花岗岩全岩Sr- Nd同位素的87Sr/86Sr值介于0.706622~0.707778之间,143Nd/144Nd介于0.51212~0.512264之间,εNd(t)=-4.093~-6.887,显示出壳源特征;Nd模式年龄TDM2=1.39~1.62Ga,平均为1.49Ga,表明其源区可能与敦煌岩群相关。结合成岩年龄和区域构造演化特征,推测敦煌地块南缘在石炭纪到早二叠世处于碰撞造山作用向陆内伸展环境转换的构造背景,可能强烈卷入了一系列与古亚洲洋闭合相关的古生代造山活动中。