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221.
Linkage between permafrost distribution and river runoff changes across the Arctic and the Tibetan Plateau 总被引:1,自引:0,他引:1
River runoff in the Arctic and the Tibetan Plateau(TP) change significantly in recent decades. However, the mechanisms of the physical processes of permafrost river runoff change remain uncertain across large scale. This study investigated the mainstreams and tributaries of main Arctic and TP rivers dominated by permafrost and assessed the linkage between hydrological regime change and permafrost. The results show that the effects of permafrost on river runoff are highly dependent on the permafrost coverage of a watershed. For the past decades, the majority of the Arctic and TP basins showed increased discharge, while all of the studied basins showed increased baseflow, with faster increasing speed than total discharge.Both total discharge and baseflow annual change rate(ΔQ and ΔBF) increased with permafrost coverage, indicating the increments of streamflow are enhanced with high permafrost coverage. Meanwhile, the annual change of precipitation showed weak connection with total discharge and baseflow change. The high permafrost coverage basins showed high annual maximum/minimum discharge ratio(Qmax/Qmin), while the Qmax/Qminchanged slightly in low permafrost cover basins. Our results highlight the importance of permafrost coverage on streamflow regime change for permafrost basins across the northern hemisphere. Due to these linkage between permafrost extent and runoff regime change and the increasing changes of permafrost, more attention should be paid to the change of hydrological processes in permafrost-underlain basins. 相似文献
222.
驾鹿金矿钾长石的结构态与平衡温度及其成矿意义 总被引:2,自引:0,他引:2
笔者对小秦岭驾鹿构造蚀变岩型金矿的钾长石用红外光谱和X射线粉晶衍射法测定其结构态与平衡温度 ,结果如下 :钾长石为微斜长石 -最大微斜长石 ,Al的占位率t1(o) =0 .73~ 1.0 0 ,t1(m) =0 .2 6~ 0 ;t2 (o) =t2 (m) =0 .0 3~ 0 ;晶胞参数a0 =0 .8388~ 0 .86 11nm ,b0 =1.2 837~ 1.2 96 8nm ,c0 =0 .7156~ 0 .72 4 8nm ,α =89.90 6~ 91.0 93° ,β =115.6 50~ 116 .2 30° ,γ=87.50 0~ 89.994° ;三斜度Δ =0 .6 86~ 1.115;平衡温度t =50 3.51~ 578.35℃。因此 ,认为驾鹿钾长石是热液蚀变的产物 ,它调整结构所释放的热量对早期高温阶段的含金热液有影响 ,起着一种活化金络合物的作用 ,不利于金沉淀就位。随着钾长石平衡温度的降低和三斜度的升高 ,这种作用相对更加明显。 相似文献
223.
Jiahao Wang Xiong Pang Daqing Tang Baojun Liu Donghao Xu 《Marine Geophysical Researches》2013,34(3-4):195-207
The Baiyun Sag, situated at the north continental slope of the South China Sea, is a main sub-unit in the Southern Depression Belt of the Pearl River Mouth Basin. In this Sag, the middle Eocene Wenchang and upper Eocene–lower Oligocene Enping Formations had developed in the evolution stage of continental faulted basin. Seismic stratigraphic sequences and fault structures revealed that the Baiyun Sag was short of long-reaching boundary faults, and that it was a rifted basin greatly influenced by basement faults rather than a typical half-graben. Different from the sags in Northern Depression Belt of the Pearl River Mouth Basin which controlled by large-scale NEE-strike faults, the Baiyun Sag had been controlled by two groups of NWW-strike en echelon fault belts with approximate opposite dips, which developed in the southwest and northeast of this Sag respectively and had played the roles of boundary faults. These en echelon faults, together with narrow synclines, partial flower structures and fluid diapirs, indicated the left-lateral transtensional activities, which had resulted in subsidence center departing to main faults and stretching S-shaped. Moreover, the en echelon faults had constructed many composite transfer zones of relay ramps, and controlled the distribution of sandbodies. The en echelon fault belts are located in accordance with Nw-striking Mesozoic basement faults. Hence the left-lateral transtensional activities were responsible for the Western Pacific Plate subducting and strike slip reactivation of the basement faults. Significantly, NW-striking basement faults had forcefully determined the development of not only the Baiyun Sag but also the Xingning Sag. 相似文献
224.
大尺度环境中中尺度对流系统生成的数值模拟试验 总被引:1,自引:0,他引:1
对1983年6月11日20时(北京时)实测资料进行低通滤波处理,取其大尺度部分作为初值,用七层原始方程模式对江淮气旋内中尺度对流系统的生成过程进行数值模拟试验.结果表明,从大尺度背景场出发,可以模拟出中尺度对流系统的生成.在西南低空急流十分潮湿的情况下,中尺度对流系统可以在江淮气旋暖区、低空急流大风速中心的前部、位势稳定度倾向维持负值的地区生成和发展.它的动力、热力结构,降水分布,以及发生、发展过程等,都与暖季(3—9月)在美国中部频繁出现的中尺度对流复合体(MCC)十分相似. 相似文献
225.
Wu Daqing 《中国地球化学学报》1987,6(3):216-224
Phase relations in the ternary systems Ag2S-Cu2S-PbS and Ag2S-Cu2S-Bi2S3 were studied using the silica vacuum technique.
In the system Ag2S-Cu2S-Bi2S3 the phase relations are dominated by join-lines from galena to f.c.c. (Agx Cu2−xS) and b.c.c. (Cux Ag2−xS) at 500°C. With decreasing temperature, galena can coexist with all the phases on the Ag2S-Cu2S join.
There are six solid solutions, and one new phase, i.e., “C” whose composition is Ag1.1 Cu4.8Bi5.8S12 in the system Ag2S-Cu2S-Bi2S3 at 500°C. The pavonite (AgBi3S5) contains 14 mole% Cu2S in solid solution, but only 3.0 mole% Ag2S in CuBi3S5 solid solution. The Cu3Bi5S9 ss and wittichenite (Cu3BiS3) ss can form join-lines with pavonite as and have the maximum contents of 9.0 and 18 mole% Ag2S. The most striking feature is the presence of bejaminite as a stable phase with a chemical formula of Ag2Bi4S7 on the Ag2S-Bi2S3 join. AgBiS2 of the PbS type occupies a fairly large field with a maximum of 23 mole% Cu2S. 相似文献
226.
长程关联存在于许多的自然现象和过程中,分数ARIMA模型很好地反映了这种特性。本结合地震活动,探索了分数ARIMA模型的建模预报方法,所得结果在很小的误差范围内跟实际情况一致,表明了本方法的实用价值。 相似文献
227.
本文提出了异常前兆信息量的直接计算法,实现了各种观测资料前兆异常的无量纲前兆信息量转换。用该方法对甘、宁,青地区5种观测手段共92个测项的5日均值一阶差分相关异常进行了前兆信息量计算,通过24次5级以上相关地震的回顾性分析研究,求得了92个测项的有效单位异常平均信息量,为前兆标志体系的进一步研究打下了良好的基础,又通过7次7级以上相关地震前兆信息量变化特征的统计,给出了一组预报地震三要素参考指标。 相似文献
228.
分析了2005年7月25日林甸5.1级地震和2005年2月23日富裕3.7级地震前,林甸1井大地微电流、林甸04井的氦气和大庆地震台的地温异常变化。大地微电流在这2次地震前具有明显的异常变化,其异常幅度达正常背景值的10-20倍。氦气在林甸5.1级地震前具有明显前兆异常变化。 相似文献
229.
230.