Geochemical Exploration on the Stream Sediments of Gabal El Mueilha Area, Central Eastern Desert, Egypt: An Overview on the Rare Metals

Abstract: El Mueilha area consists of post-collision granitic rocks intruding Pan-African metasediments, metavolcanics and granodiorites. Tin mineralization in Gabal El Mueilha is either of vein type or disseminated in the greisenized and albitized parts of the granitic rocks. Cassiterite and wolframite-bearing quartz veins also characterize a small intrusion of muscovite granite at El Mueilha tin mine area. Detailed geochemical prospecting for the rare metals Sn, Nb, Be, Li, U, Th and some other trace elements was carried out at Gabal El Mueilha area using stream sediments survey. Sixty-seven stream sediment samples were collected from the main drainage patterns of the study area. Statistical parameters were calculated for the analyzed elements. The sought elements Sn, Nb, Be and Li have relatively high background values in the studied sediments. This may reflect the role of the pathfinder elements (Nb, Be and Li) during secondary dispersion survey for Sn mineralization.
Geochemical maps were constructed to delineate anomalous areas with abnormally high rare metal contents. The anomalous Sn, Nb and Be areas are mainly encountered in the main stream draining the mineralized zones of El Mueilha tin mine and near the SW albitized parts of the post-collision granite. Correlation coefficient matrices show significant positive relation between Sn and the rare metals group (Nb, Rb and Li) at 99 % significant level. R-mode factor analysis for the concerned elements yields five factor–model.     

An Analysis of Spatial and Temporal Dimension of Drought Vulnerability in Turkey Using the Standardized Precipitation Index

Drought has become a recurrent phenomenon in Turkey in the last few decades. Significant drought conditions were observed during years of late 1980s and the trend continued in the late 1990s. The countrys agricultural sector and water resources have been under severe constraints from the recurrent droughts. In this study, spatial and temporal dimensions of meteorological droughts in Turkey have been investigated from vulnerability concept. The Standardized Precipitation Index (SPI) method was used to detail geographical variations in the drought vulnerability based on frequency and severity of drought events at multiple time steps. Critical (threshold) rainfall values were derived for each station at multiple-time steps in varying drought categories to determine least amount of rainfall required to avoid from drought initiation. The study found that drought vulnerability portrays a very diverse but consistent picture with varying time steps. At regional scale, south-eastern and eastern Anatolia are characterized with moderate droughts at shorter time steps, while the occurrence of severe droughts at shorter time steps is observed at non-coastal parts of the country. A similar picture was observed with very severe droughts. The critical (threshold) values exhibited rising numbers during the growing season at 3-month step in the South-eastern Anatolia, which might have significant consequences considering presence of large irrigation projects under-development in the region. In general, rainfall amounts required for non-drought conditions decrease from the coastal parts toward the interiors with increasing time steps.     

Tectonic Imprints of the Hazara Kashmir Syntaxis on the Mesozoic Rocks Exposed in Munda,Mohmand Agency,Northwest Pakistan

Two well-developed mesoscopic folds, D_2 and D_3, which postdate the middle amphibolite metamorphism, were recognized in the western hinterland zone of Pakistan. NW–SE trending D_2 folds developed during NE–SW horizontal bulk shortening followed by NE–SW trending D_3 folds, which developed during SE–NW shortening. Micro- to mesoscopically the NW–SE trending S2 crenulation cleavage, boudins and mineral stretching lineations are overprinted by D_3. The newly established NW–SE trending micro- to mesoscopic structures in Munda termed D_2, which postdated F_1/F_2, is synchronously developed with F3 structures in the western hinterland zone of Pakistan. We interpret that D_2 and D_3 folds are counterclockwise rotated in the tectonic event that has evolved the Hazara Kashmir Syntaxis after the main phase Indian plate and Kohistan Island Arc collision. Chlorite replacement by biotite in the main matrix crenulation cleavages indicates prograde metamorphism related with D_2. The inclusion of muscovite and biotite in garnet porphyroblasts and the presence of staurolite in these rocks indicate that the Barrovian metamorphic conditions predate D_2 and D_3. We interpret that garnet, staurolite and calcite porphyroblasts grew before D_2 because the well developed S2 crenulation cleavage wraps around these porphyroblasts.     

Distribution of fluoride in groundwater of Maku area, northwest of Iran

High fluoride groundwater occurs in Maku area, in the north of West Azarbaijan province, northwest of Iran. Groundwater is the main source of drinking water for the area residents. Groundwater samples were collected from 72 selected points including 40 basaltic and 32 nonbasaltic springs and wells, in two stages, during June and August 2006. The areas with high fluoride concentrations have been identified, and the possible causes for its variation have been investigated. Regional hydrogeochemical investigation indicates that water-rock interaction is probably the main reason for the high concentration of ions in groundwater. The concentration of F⁻ in groundwater is positively correlated with that of HCO₃ ⁻ and Na⁺, indicating that groundwater with high HCO₃ ⁻ and Na⁺ concentrations help to dissolve some fluoride-rich minerals. All of the water samples, collected from the basaltic areas do not meet the water quality standards for fluoride concentration and some other parameters. Hence, it is not suitable for consumption without any prior treatment. Inhabitants of the area that obtain their drinking water supplies from basaltic springs and wells are suffering from dental fluorosis. The population of the study area is at a high risk due to excessive fluoride intake especially when they are unaware of the amount of fluoride being ingested due to lack of awareness.     

A preventative approach to mitigating CW interference in GPS receivers

In the global positioning system (GPS), code division multiple access (CDMA) signals are used. Because of the known spectral characteristics of the CDMA signal, continuous wave (CW) interference has a predictable effect on the different pseudo random noise (PRN) spreading codes (unique to each satellite) depending on the Doppler frequency of the signal. The Doppler frequency for each signal is also predictable once the receiver position is known. As different satellite signals have different Doppler frequencies, the effect on the signal quality is also different. In this paper first the effect is studied analytically. The concept of an “exclusion zone” is defined and analyzed for each satellite. This exclusion zone, where that satellite should not be used due to interference degradation, is shown to be predictable for each satellite as a function of time. Using this prediction, the CW interference effect on the positioning quality of the receiver can be mitigated by ignoring the affected satellites within exclusion zones when performing position evaluation. The threshold beyond which a satellite should be excluded is then derived by studying the mutual effects of the geometry and the signal quality of that satellite on the positioning quality. Receiver autonomous integrity monitoring (RAIM) uses redundancy in measurements to perform an internal consistency check to see if all of the measurements are satisfactory. In this paper this technique is also used to mitigate the effect of CW interference on the positioning accuracy. Finally it is shown that the prediction of the exclusion zone for each satellite outperforms the RAIM algorithm in mitigation the effect of the interference when 5 satellites are visible. An erratum to this article can be found at     

乌鲁木齐市低层大气稳定度分布特征的统计分析

利用乌鲁木齐市4座100 m梯度气象塔2013年6月至2014年4月10 min气象资料,对比分析了温差法、温差-风速法、风速比法、理查森数法和总体理查森数法计算的A~F类大气稳定度的适用性,表明温差-风速法更适合乌鲁木齐市大气稳定度的分类,运用该方法计算出的A~F类稳定度进而统计分析乌鲁木齐市城区和郊区稳定度的频率分布特征。结果表明:郊区稳定类所占比例高于城区,城区中性类高于郊区,南郊和城区不稳定类高于北郊。中性类在冬季较大,春季和秋季较低;不稳定类在6月最高、9和1月最低;稳定类在10和1月最高、6和7月最低。白天以不稳定为主(占全天88.3%~96.3%)、夜间以稳定为主(占全天51.3%~60%),夏季最明显。不稳定与中性、稳定的日变化相反,郊区日出时和城区日出后2 h左右稳定类频率最大。中性(D类)在日出和日落后1~3 h分别出现两个峰值。寒潮天气稳定性比高温天气强,静风天气郊区稳定类比大风天气强,扬沙发生前以中性和稳定类稳定度为主、发生时和发生后以不稳定为主,降雨天气不稳定类比暴雪天气强。春季和夏季重污染天气B、C和F类为主,夏季南郊和近北郊C和F类约45%,秋季B和E类为主,约40%~50%;冬季城区D类频率最大,南郊、北郊和近北郊F类频率最大。     

塔克拉玛干沙漠不同区域土壤热通量变化比较

选取塔克拉玛干沙漠腹地塔中地区和北缘过渡带肖塘地区2013年土壤热通量观测资料,初步比较分析了塔克拉玛干沙漠两种下垫面的土壤热通量变化特征。结果表明：(1)在日变化尺度上,两个站点都有明显的日变化特征,1月份塔中站土壤热通量日平均变化幅度小于肖塘站,日较差分别为58.9 W.m2和72.4 W.m2,4月份两站土壤热通量变化幅度较为接近,日较差分别为88.1W.m2、100.1 W.m2。7、10月份塔中站土壤热通量变化幅度明显高于肖塘站,日较差分别为99.0 W.m2、53.7W.m2,100.3 W.m2、73.3W.m2。(2)不同天气条件下两个站点土壤热通量变化都有很大差异。晴天,塔中站和肖塘站土壤热通量变化都呈现出单峰型,变化幅度较一致,日较差分别为119.7 W.m2、119.1 W.m2。沙尘天和雨天受云层或降水的影响土壤热通量变化波动较大,沙尘天塔中站变化幅度小于肖塘站,日较差分别为83.6 W.m2、133.1 W.m2;雨天塔中站和肖塘站变化幅度都很剧烈,日较差分别为70.6 W.m2、66.6 W.m2。(3)年变化尺度上,塔中站土壤热通量在7月份达到最大值(7.7 W.m2),在11月出现最小值(-5.3 W.m2),肖塘站7月份出现最大值(4.2 W.m2),11月份出现最小值(-10.2 W.m2)。塔中站和肖塘站土壤热通量年总量差异很大,塔中站为16.8 W.m2,能量由大气向土壤传递,土壤为热汇,而肖塘站则为-34.9 W.m2,能量由土壤向大气传播,土壤表现为热源。     

肖塘地区夏季土壤CO2浓度日变化特征及影响因素

利用塔克拉玛干沙漠北缘流动沙漠—古河床过渡带肖糖地区2012年6—8月土壤40 cm深处CO_2 浓度和相关气象要素资料,对该区域的土壤CO_2 浓度变化特征及影响因子进行了分析。结果表明:(1)肖塘地区夏季土壤40 cm深处CO_2 浓度的日变化过程中呈现出夜间低、白天高的单峰型,日最高值出现在18:00左右,最低值出现在6:30左右,浓度平均值保持在506.97~518.14 ppm之间;(2)随着土壤温度和土壤湿度的变大,土壤CO_2 浓度增大,两者呈显著正相关;(3)风速和土壤CO_2 浓度之间存在一定的滞后性;(4)大气压力对土壤CO_2 浓度变化产生显著影响,两者呈负相关。