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101.
102.
对东南极中山站附近麦氏贼鸥巢区和无巢贼鸥群栖地的贼鸥回吐渣团及其他食物残物进行收集、分析和鉴定 ,结果表明 ,本区麦氏贼鸥主要捕食雪 ,其残物在食物项中的平均出现率为 6 7~ 80 %;同时贼鸥从本区几个考察站觅取人类遗弃的垃圾食物作为其重要的食物补充 ,垃圾食物的平均出现率为 6 .8~ 1 1 .6 %。不同巢区贼鸥对雪 的捕杀量和垃圾的需求差异较大 ,其主要与营巢地域的雪 分布密度以及摄食区的占有与否有关。 相似文献
103.
Separation of electrostatic charge during the transport of particles by wind adds a force to the gravitational and fluid forces that determine trajectories of particles moving by saltation. Evaluating this electrostatic force requires the electric field strength very near the saltation surface, and charge-to-mass ratios for the moving particles. Field mill readings 4 cm above the surface in a moderate blizzard showed electric field strength as high as +30 kV m-1. Another experiment gave charge-to-mass ratios of individual saltation particles in low-level drifting that ranged between +72 C kg-1 and -208 C kg-1. From these measurements, we estimated electrostatic forces as large as the gravitational force on some saltating particles. Including forces of this magnitude in the equations of motion significantly alters predicted saltation trajectories from those for uncharged particles. Predictions appear reasonable that for some saltating particles, the electrostatic force prevents new surface impacts. These results should help improve models of energy transfer in the planetary boundary layer during blizzards and sandstorms. 相似文献
104.
Characteristics of melt inclusions in skarn minerals from Fe,Cu(Au) and Au(Cu) ore deposits in the region from Daye to Jiujiang 总被引:5,自引:0,他引:5
The skarns and skarn deposits are widely distributed at home and abroad. The skarn deposits include many kinds of ores and higher ore grade. Some of them are broad in scale. Scientists of ore deposits from different countries have paid and are paying grea… 相似文献
105.
2004年3月至2005年7月对古尔班通古特沙漠南部典型半固定沙垄土壤水分进行了系统监测,结合气象资料,特别是对冬季积雪和冻土资料的分析,认为该沙漠沙丘土壤水分时空变化规律在很大程度上受积雪融化和季节性冻土的影响.由于冬季稳定存在20~30 cm的积雪于春季融化,使得春季沙丘土壤含水率成为全年最高的季节,从而为早春植物的萌发生长创造了有利的条件.冬季1 m多深的冻土于早春时节由表及里开始消融,沙丘表面融化的雪水在坡面重力作用下,沿难以透水的冻土层上界自坡上向坡下发生迁移,在春夏季形成了垄间最高、坡部次之和垄顶最少的土壤水分空间格局.该研究具有生态学意义,可为古尔班通古特沙漠特殊环境条件下植被恢复与重建提供依据. 相似文献
106.
Mantle process beneath Philippine Sea back-arc spreading ridges: A synthesis of peridotite petrology and tectonics 总被引:2,自引:0,他引:2
Abstract In order to obtain a general view of the mantle process beneath a back‐arc basin spreading ridge, the diversity of peridotite petrology and tectonic occurrences in two back‐arc basin spreading ridges from the Philippine Sea were examined: the Parece Vela Rift and the Mariana Trough. The Parece Vela Basin spreading ridge (Parece Vela Rift) was a physically fast/intermediate‐spreading ridge, although many tectono‐magmatic features resemble those of slow‐ to ultraslow‐spreading ridges. Two unusual features of the Parece Vela Rift further demonstrate the uniqueness of the ridge: full‐axial development of oceanic core complexes and exposure of mantle peridotite at segment midpoints. The Parece Vela Rift yields a lithological assemblage of residual but still fertile lherzolite/harzburgite, plagioclase‐bearing harzburgite and dunite; similar assemblages are reported from the equatorial Mid‐Atlantic Ridge at the Romanche Fracture Zone and the ultraslow‐spreading ridges from the Indian and Arctic Oceans. The tectono‐magmatic characteristics of the Parece Vela Rift suggest that diffuse porous melt flow and pervasive melt–mantle interaction were the important mantle processes there. Globally, this ‘porous melt flow‐type’ mantle process is likely to occur beneath a segment midpoint of the ridge having a thick lithosphere, typically an ultraslow‐spreading ridge. In contrast, the Mariana Trough is a typical slow‐spreading ridge, exposing mantle peridotite at segment ends. The Mariana Trough yields a lithological assemblage of residual harzburgite and veined harzburgite, a common assemblage among the global abyssal peridotite suite. The tectono‐magmatic characteristics of the Mariana Trough suggest that channeled melt/fluid flow and limited melt–mantle interaction are the important mantle processes there, because of the colder wall‐rock peridotite in the segment end. This ‘channeled melt flow‐type’ mantle process is likely to occur in the shallow lithospheric mantle at the segment ends of any spreading ridges. 相似文献
107.
桃仙机场雷雨转雨夹雪天气的分析 总被引:3,自引:0,他引:3
通过对桃仙机场仅有的两次雷雨转雨夹雪天气过程的分析,总结出此类天气的形势特点,并初步得出此类天气预报的着眼点,为秋季飞行提供可靠的预报保障。 相似文献
108.
Melt inclusion and host glass compositions from the easternend of the Southwest Indian Ridge show a progressive depletionin light rare earth elements (LREE), Na8 and (La/Sm)n, but anincrease in Fe8, from the NE (64°E) towards the SW (49°E).These changes indicate an increase in the degree of mantle meltingtowards the SW and correlate with a shallowing of the ridgeaxial depth and increase in crustal thickness. In addition,LREE enrichment in both melt inclusions and host glasses fromthe NE end of the ridge are compatible with re-fertilizationof a depleted mantle source. The large compositional variations(e.g. P2O5 and K2O) of the melt inclusions from the NE end ofthe ridge (64°E), coupled with low Fe8 values, suggest thatmelts from the NE correspond to a variety of different batchesof melts generated at shallow levels in the mantle melting column.In contrast, the progressively more depleted compositions andhigher Fe8 values of the olivine- and plagioclase-hosted meltinclusions at the SW end of the studied region (49°E), suggestthat these melt inclusions represent batches of melt generatedby higher degrees of melting at greater mean depths in the mantlemelting column. Systematic differences in Fe8 values betweenthe plagioclase- and the olivine-hosted melt inclusions in theSW end (49°E) of the studied ridge area, suggest that theplagioclase-hosted melt inclusions represent final batches ofmelt generated at the top of the mantle melting column, whereasthe olivine-hosted melt inclusions correspond to melts generatedfrom less depleted, more fertile mantle at greater depths. KEY WORDS: basalt; melt inclusions; olivine; plagioclase; Southwest Indian Ridge 相似文献
109.
伊犁地区近35年冬季积雪变化特征分析 总被引:1,自引:0,他引:1
通过对伊犁地区8个气象地面观测站35a(1971—2005年)11—3月逐旬的冬季最大积雪深度、积雪日数、降水量和平均温度的统计分析,结果表明:伊犁地区冬季降雪的时间、空间分布不均,最大降雪发生在新源;平均雪深最大的是伊宁县,最小的是特克斯县;冬季积雪日数变化相对比较稳定;冬季降雪与平均温度存在着很好的响应关系。在SPSS中对冬季的平均温度与平均降水和平均雪深进行相关分析,发现平均雪深、平均温度和平均降水为显著正相关。 相似文献
110.