A comparative study of the Rare Earth Element (REE) distributions within the Lower Cretaceous dolomites and limestones of Central Tunisia     

SA&#;MD TLIG  ALI M'RABET 《Sedimentology》1985,32(6):897-907

REE distribution, strontium content and oxygen isotopic composition have been studied in the Lower Cretaceous dolomites and their interbedded and/or parental limestones of Central Tunisia. Dolomites, as indicated by previous sedimentologic, geochemical and isotopic study, are different in origin. Environments of dolomite formation include: evaporitic sabkha, deep phreatic, karst and lacustrine. With the exception of the sabkha environment, dolomitizing fluids presumably have been essentially meteoric. The comparison between REE distributions in dolomites and limestones clearly suggests that the general shapes of the REE patterns are preserved during dolomitization. Nevertheless, the total REE amounts are somewhat lowered in dolomites comparatively to parental limestones. Moreover, within the dolomites, the total REE contents are positively correlated to the Sr and δ¹⁸O contents; thus indicating that the decrease in REE, Sr, and δ¹⁸O contents is related to a decrease in the salinity of dolomitizing fluids. In addition, dolomites associated with emergence surfaces (karst) are the most impoverished in REE. Furthermore, they are relatively enriched in light REE, indicating a more or less important fractionation with the REE distributions. This enrichment has been related to the influence of the inorganic complexes which favours the greatest solubility of the heavy REE in basic solution with respect to the lightest members of the REE group.  相似文献   

AN ANALYTICAL RAYPATH APPROACH TO THE REFRACTION WAVEFRONT METHOD1     

M. ALI AK 《Geophysical Prospecting》1990,38(8):971-982

Seismic refraction surveying is still an important tool for determining the geometries and elastic wave propagation velocities of near-surface layers. Many analytical and graphical methods have been developed over the years for refraction interpretation, and these can be classified into two basic groups. The first group visualizes critically refracted rays converging on a common surface position, while the second group, which includes the wavefront methods, makes use of the critical rays emerging from a common point on the refractor. The method described in this paper is an analytical approach to the wavefront methods. The reverse refracted ray received by a geophone is intersected by the forward refracted rays received by subsequent geophones and a common critical refraction point on the refractor is estimated after a series of comparisons. This process is repeated for each geophone to yield the geometry and the velocity of the refractor. Several interpolations are performed to achieve a better accuracy. Palmer's models are used to test the efficiency of the algorithm. The results are presented together with those of other methods applied to the same models.  相似文献   

RESOLUTION OF STRONGLY OVERLAPPING TWO-WAY MULTICOMPONENT DATA BY MEANS OF HEURISTIC EVOLVING LATENT PROJECTIONS   总被引：3，自引：0，他引：3  

OLAV M.KVALHEIM  ALI RAHMANI  RICHARD G.BRERETON 《地理学报(英文版)》1993,(1)

High-performance liquid chromatography with diode array detection(HPLC-DAD)is used tocharacterize mixtures from chlorophyll α degradation experiments.Overlapping chromatographic peaksare resolved by means of the heuristic evolving latent projections(HELP)method.The HELP methodis a self-modelling curve resolution method.No assumptions are made about spectral and/orchromatographic peak shape.In the first step the method establishes the real noise level in the data byuse of the so-called zero-component regions.This information is used to reveal selective chromatographicinformation and the number of chemical species at every retention time in unresolved chromatographicpeaks.Utilising the selective chromatographic regions in combination with the zero-concentrationwindows,unique resolution into concentration profiles and spectra of the pure chemical species isaccomplished.HPLC-DAD data from six chlorophyll a degradation experiments were analysed.Consistent results were obtained even with very similar spectra for six or seven overlapping chemicalcomponents.  相似文献   

塔克拉玛干沙漠腹地散射辐射特征     

买买提艾力·买买提依明  缪启龙  金莉莉  何清  李振杰 《中国沙漠》2013,33(5):1492-1500

本文利用塔克拉玛干沙漠大气环境观测试验站2010年总辐射、散射辐射、直接辐射观测资料分析了塔克拉玛干沙漠腹地的散射辐射变化特征和散射辐射与晴空指数、大气质量的关系。结果表明:散射辐射年曝辐量为3 628.5 MJ·m-2,占年总辐射曝辐量的59.5%,高于全国平均值;散射辐射夏季大（468.3 MJ·m-2）、冬季小（120 MJ·m-2）,日最高值基本出现在正午,夏季最高辐照度达719.2 W·m-2。与晴空指数大于0.7时相比,晴空指数小于0.7时,秋、冬季散射辐射增加。晴空指数>0.3时,散射辐射与总辐射的比值随晴空指数的增加而呈线性递减;晴空指数<0.3时,散射辐射与天文辐射的比值随晴空指数的增加基本呈直线增加。散射辐射随太阳高度角的增大呈指数递增。散射辐射的变化主要集中在大气质量小于5的范围内且随大气质量的增加而迅速降低。  相似文献   

塔克拉玛干沙漠北缘辐射分量特征     

王延慧  史玉光  买买提艾力  买买提依明  何清  李帅 《中国沙漠》2013,33(6):1824-1831

利用塔克拉玛干沙漠北缘肖塘自动站2011年直接探测的辐射资料,对该地区辐射状况进行了初步分析。结果表明:短波辐射各个分量的月总量最大值均出现在7月,总辐射瞬时最大值为1 329.6 W·m-2,出现在6月。晴天天气下,辐射分量均为夏季最大,冬季最小,除大气长波辐射外,其他分量均呈现出标准的倒“U”型。大气长波辐射浮尘、扬沙天气时的日总量,均与晴天时一致;而地面长波辐射日总量则是晴天时最大,浮尘天气次之,阴天最小。肖塘地区地表反照率冬季较大,夏季较小,年均值为0.27,比塔克拉玛干沙漠腹地（0.3）低10%,但远高于绿洲和高原。  相似文献   

塔克拉玛干沙漠肖塘地区空气动力学粗糙度分析   总被引：8，自引：2，他引：6  

何清  缪启龙  张瑞军  艾力·买买提明  刘新春  霍文 《中国沙漠》2008,28(6):1011-1016

利用塔克拉玛干沙漠北部肖塘地区梯度自动站2007年1月1日至2007年5月31日的观测数据,计算出该区域中性条件下粗糙度范围是1.00×10-11~1.65×10-3 m,平均粗糙度为6.05×10-5 m,接近沙粒粒径的1/30,与平坦沙面粗糙度相似。摩擦速度的范围是0.14~2.33 m·s-1,平均值1.24 m·s-1。粗糙度随下垫面性质变化明显,与稳定度呈正相关,与风速呈负相关,摩擦速度随粗糙度增大而减小。  相似文献   

塔里木盆地TSP时空分布特征及影响因素分析   总被引：3，自引：2，他引：1  

刘新春  艾力·买买提明  霍文  何清  梁云  黄向春 《中国沙漠》2008,28(5):962-967

利用2004—2008年沙尘暴观测站网哈密、塔中与和田的TSP观测资料,同时结合铁干里克、民丰和喀什2007年4月开始的TSP、沙尘天气等相关资料,给出了塔里木盆地TSP时空分布特征及变化特征,同时分析了影响TSP质量浓度变化的主要因素。结果表明：①塔里木盆地东部TSP质量浓度最低,南缘最高,往盆地的西缘逐渐降低,塔中一直处于较高值。影响TSP质量浓度高低分布的主要因素是沙尘天气,沙尘天气日数越多,则浓度越高。②2004—2008年TSP年平均质量浓度哈密最低,其次为塔中,最高为和田。③2004—2007年哈密、塔中与和田TSP平均质量浓度春季最高,其次是夏季和秋季,冬季最低。④哈密、塔中与和田2005—2008年TSP质量浓度每年不同时间段各不相同。  相似文献   

东疆黑戈壁陆面过程参数及陆面模式离线模拟     

买买提艾力·买买提依明  王豫  阿吉古丽·沙依提  高佳程 《沙漠与绿洲气象(新疆气象)》2024,18(1):20-27

新疆东部黑戈壁气候恶劣、人迹罕至,是具有黑色砾石下垫面的生态脆弱区。利用东疆哈密戈壁陆气相互作用站2018年全年观测资料,给出该戈壁地表动力学与热力学粗糙度、比辐射率和地表反照率等陆面过程特征参数,并将这些参数代入Noah模式对该戈壁热通量、地表温度及土壤温湿度进行模拟。结果表明：（1）东疆黑戈壁下垫面动力学粗糙度为1.13×10-3 m,热力学粗糙度为0.32×10-3 m,比辐射率为0.905。（2）地表反照率日变化呈早晚高,中午低的“U”型曲线。12月因地面积雪,反照率最高,年内极大值出现在12月8日,为0.79,年均反照率为0.29。地表反照率关于太阳高度角的参数化方案为：α=0.78-0.47×(1-e^((-h)/1.12)),地表反照率关于5 cm土壤湿度的参数化方案为α=0.28-0.136w_s。（3）将改进后的陆面过程参数带入Noah模式,大大提高了模式在戈壁区域的模拟能力。  相似文献   

阿克苏地区雷暴时空变化特征     

艾力·买买提明  阿吉古丽·沙依提  何清  霍文  杨兴华  刘新春 《中国沙漠》2012,32(4):1110-1118

 利用阿克苏地区1960—2010年雷暴资料,采用气候倾向率、保证率等气候诊断方法,探讨了阿克苏地区雷暴的时空分布规律、气候变化趋势等。结果表明,阿克苏地区雷暴空间分布表现为西多东少、北多南少,位于该地区西部的乌什县为雷暴多发中心;全区年平均雷暴日数为18.7~52.0 d;阿克苏地区每10 a雷暴日数减少2.8 d;雷暴主要集中在3—11月,7月达到最大值,11月下旬至翌年2月基本无雷暴;80%的保证率下雷暴初日出现在5月中旬至下旬之间,雷暴终日出现在9月下旬至10月中旬之间;阿克苏地区一日当中雷暴主要发生在午后至前半夜,雷暴高峰值出现在16—19时,雷暴平均持续时间在35~47 min,雷暴出现最多的方位是W和N。  相似文献   

星基多光谱分析的降水估算     

马雷凯  邢文渊 《沙漠与绿洲气象(新疆气象)》2010,4(3):59-61

<正>对从已广泛应用的全球气候模型到局地降水和洪灾的预报而言,准确估算降水的数量、时间和空间分布是至关重要的。降水作为地球水循环的一个关键组成部分,对于人类的生命财产安全有着重要的影响。从区域到全球尺度,现存的地基降水观测网络是不足的;因此,卫星提供了一种可行和吸引人的选择。很显然,  相似文献