Recognition method for mid‐ to long‐term runoff forecasting factors based on global sensitivity analysis in the Nenjiang River Basin

Mid‐ to long‐term runoff forecasting is important to China. Forecasting based on physical causes has become the trend of this field, and recognition of key factors is central to recent development. Here, global sensitivity analysis based on back‐propagation arithmetic was used to calculate the sensitivity of up to 24 factors that affect runoff in the Nenjiang River Basin. The following five indices were found to be key factors for mid‐ to long‐term runoff forecasting during flood season: Tibetan Plateau B, index of the strength of the East Asian trough, index of the area of the northern hemisphere polar vortex, zonal circulation index over the Eurasian continent and index of the strength of the subtropical high over the western Pacific. The hydrological climate of the study area and the rainfall–runoff laws were then analysed in conjunction with its geographical position and topographic condition. The rationality of the results can be demonstrated from the positive analysis point of view. The results of this study provide a general method for selection of mid‐ to long‐term runoff forecasting factors based on physical causes. Copyright © 2012 John Wiley & Sons, Ltd.     

Interpretation of Mineral Zoning in Submarine Hydrothermal Ore Deposits in Terms of Coupled Fluid Flow‐Precipitation Kinetics Model

Major minerals (sulfates, sulfides, quartz) are distributed in different parts of submarine hydrothermal ore deposits. For instance, the abundance of barite increases stratigraphically upwards in the massive orebodies of the Kuroko deposits (black and yellow ores), while quartz is abundant in the lower parts (siliceous ore). The different distribution of barite and quartz in the Kuroko deposits can not be accounted for by thermochemical equilibrium calculations based on the precipitation due to mixing of ascending hydrothermal solutions with ambient cold seawater. In the present study, a coupled fluid flow‐precipitation kinetics model was used to calculate the amounts of quartz, barite, and anhydrite precipitated from a hydrothermal solution mixed with seawater, assuming reasonable values for temperature, precipitation rate, fluid flow velocity, mineral surface area/fluid mass ratio (A/M), and initial concentrations of hydrothermal solution and seawater before mixing occurred. The results indicate that barite precipitates more efficiently than quartz from discharging fluids with relatively higher flow velocity, lower temperatures and under the condition of lower A/M ratios on the seafloor (black ore), whereas quartz precipitates more effectively from solutions with lower flow velocity, higher temperatures and higher A/M ratios beneath the seafloor (siliceous ore) and in the orebody (barite ore, ferruginous chert ore). Anhydrite precipitates in shallow sub‐seafloor environments with lower precipitation rates and higher A/M ratios than barite and higher precipitation rates and lower A/M ratios than quartz. These results explain the observed occurrences of barite, anhydrite, and quartz in the Kuroko deposits. Namely, barite is abundant in black ore and barite ore which formed above the seafloor, anhydrite formed in high‐permeability tuff breccias, and quartz formed in low permeability dacite intrusive bodies in the sub‐seafloor environment.     

Geological observations in high‐grade mid‐Proterozoic rocks from Else Platform,northern Prince Charles mountains region,east Antarctica

Granulite facies rocks on Else Platform in the northern Prince Charles Mountains, east Antarctica, consist of metasedimentary gneiss extensively intruded by granitic rocks. The dominant rock type is a layered garnetbiotite‐bearing gneiss intercalated with minor garnet‐cordierite‐sillimanite gneiss and calc‐silicate. Voluminous megacrystic granite intruded early during a mid‐Proterozoic (ca 1000 Ma) granulite event, M₁, widely recognized in east Antarctica. Peak metamorphic conditions for M₁ are in the range of 650–750 MPa at ～800°C and were associated with the development of a gneissic foliation, S₁ and steep east‐plunging lineation, L₁. Strain partitioning during progressive non‐coaxial deformation formed large D₂ granulite facies south‐dipping thrusts, with a steep, east‐plunging lineation. In areas of lower D₂ strain, large‐scale upright, steep east‐plunging fold structures formed synchronously with the D₂ high‐strain zones. Voluminous garnet‐bearing leucogneiss intruded at 940 ±20 Ma and was deformed in the D₂ high‐strain zones. Textural relationships in pelitic rocks show that peak‐M2 assemblages formed during increasing temperatures via reactions such as biotite + sillimanite + quartz ± plagioclase = spinel + cordierite + ilmenite + K‐feldspar + melt. In biotite‐absent rocks, re‐equilibration of deformed M₁ garnet‐sillimanite‐ilmenite assemblages occurred through decompressive reactions of the form, garnet + sillimanite + ilmenite = cordierite + spinel + quartz. Pressure/temperature estimates indicate that peak‐M₂ conditions were 500–600 MPa and 700±50°C. At about 500 Ma, north‐trending granitic dykes intruded and were deformed during D₃‐M₃ at probable upper amphibolite facies conditions. Cooling from peak D₃‐M₃ conditions was associated with the formation of narrow greenschist facies shear zones, and the intrusion of pegmatite. Cross‐cutting all features are abundant north‐south trending alkaline mafic dykes that were emplaced over the interval ca 310–145 Ma, reflecting prolonged intrusive activity. Some of the dykes are associated with steeply dipping faults that may be related to basin formation during Permian times and later extension, synchronous with the formation of the Lambert Graben in the Cretaceous.     

福建数字地震台网测定中国台湾中深源地震研究

对比福建数字地震台网测定的中国台湾中深源地震目录与中国台湾中央气象局公布的相应中深源地震目录,分析震源位置和发震时刻的差别情况,基本认为:福建台网测定中国台湾中深源地震的结果,在震中位置上,纬度偏大,即偏北;经度偏小,即偏向台网方向;采用单纯型方法定位的结果,发震时刻略偏小,震源深度偏小较多;用Locsat方法定位的结...     

天山中东段地震层析成像的初步研究

以中国境内天山中东段为研究区域,选定新疆地震台网自2001年以来近10年的P波和S波震相,对研究区域网格化,反演了地壳P波速度结构。结果表明：地壳中成像分辨率较高,高低速分布明显,天山中东段莫霍面埋深在48～60 km内变化,其中,中天山莫霍面最深,北天山莫霍面最浅;莫霍面起伏最大的地方往往位于盆山交汇处。     

大白菜收获期的环流分析及中期预报

根据生产实际，规定了大白菜受冻害的气象条件，利用５００ｈＰａ候平均高度资料，分析大白菜产生冻害的同期环流和前期环流形势，找出关键区指标，建立了１１月第３候，４候大白菜有无冻害的预报方程。     

人工神经网络方法在降水量级中期预报中的应用

将人工神经网络方法与统计方法相结合，采用分步预报的方法，首先用经验统计方法进行晴雨预测，再用BP人工经网络建立降水量级预报模型，探讨神经网络方法在中期降水预报的应用，试验表明，神经网络方法能提高中到大雨降水量级的中期预报能力，但对暴雨的预报不理想。     

黑龙江省逊克县东安金矿床地质特征及成因探讨

东安金矿床是黑龙江省境内新近发现的一个具有大型远景的金矿床。矿床受库尔滨壳断裂的次级断裂所控制 ,产于印支晚期碱长花岗岩和早白垩世中酸性火山 -侵入杂岩的强硅化蚀变带中。矿床成因类型属浅成中 -低温热液蚀变岩型     

EOF和CCA方法在台风路径预报试验中的比较

利用气候持续性因子，并分别考虑了５００ｈＰａ高度场的ＥＯＦ因子和ＣＣＡ因子，分别建立了基于ＥＯＦ因子和基于ＣＣＡ因子的南海台风２４－１２０小时路径预报模式。经过非独立样本和独立样本的预报检验，比较。将两种方法运用于５００ｈＰａ高度场的分析表明，ＣＣＡ方法得出的典型变量权重系数分布虽不能象ＥＯＦ方法的特征向量一样表示出明显的而且平滑的空间场形式，但ＣＣＡ方法浓缩了更多的与台风路径整体相关性最好的原变