青藏高原热状况对南亚高压活动的影响   总被引：4，自引：1，他引：4  

任广成 《大气科学》1991,15(1):28-32

本文分析了青藏高原下垫面与高原上空热状况变化的异同及其二者与南亚高压的关系。指出青藏高原下垫面热状况与高原上空热状况年际变化的一致性及月际变化的差异——青藏高原下垫面从2月就开始大幅度增温,而高原上空5月才开始突发性增温。高原下垫面降温幅度最大的月份出现在11月,高原上空则出现在10月。分析还指出,青藏高原下垫面热状况与南亚高压南北振荡,青藏高原上空热状况与南亚高压东西振荡有密切关系。并且前期青藏高原上空热状况较高原下垫面热状况对南亚高压的预报更具有指示意义。  相似文献   

Petrochemistry,Age and Petrogenesis of the Shexian Pluton in Southern Anhui     

Xing Fengming  Xu Xiang  Ren Siming  Li Yingyun 《中国地球化学学报》1991,10(3):244-256

The Shexian gneissic granodiorite in southern Anhui trends NE 55° from Shexian in the west to Guitoujian in the east with a length of 22 km and an outcrop area of 32 km. It was considered formerly to be Caledonian on the basis of a biotite K-Ar age of 474 Ma (1982). However, new evidence indicates that it may be Early Jinning in age as shown by: (1) it is found intruding into the Mid-Proterozoic Shangxi Group and is unconformably overlain by the Sinian Xiuning Formation, and (2) a zircon U-Th-Pb age of 928 Ma is obtained for the pluton. The pluton is composed of plagioclase (An=27.37%), K-feldspar(14%), biotite(16%) and quartz(32%). Accessory minerals are ilmenite (150g/T), xenotime (15g/T). garnet(25g/T), monazite(10g/T), zircon (20g/T) and apatite (104g/T). Petrochemical characteristics of the intrusion are:(l) Al-enrichment (A/NKC=1.30); (2) H₂O enrichment (H₂O= 1.74%); and (3) low oxidation index (f ’=0.10). It belongs to the continental crust transformation type as evidenced by: (1) MF and Mg/Y values of biotite are 0.41 and 0.31 respectively; (2) (⁸⁷Sr/⁸⁶Sr)=0.71119; (3) δ Eu=0.52; and (4) A/NKC=130. The Shexian pluton is therefore considered as a product of melting of phyllite at depth in the light of similarities in trace element and REE contents with the phyllite of the Banxi Group. Calculations of REE batch partial melting indicate that it may have resulted from 75% melting of the Banxi phyllite.  相似文献   

Andesite and dacite genesis via contrasting processes: the geology and geochemistry of El Valle Volcano,Panama   总被引：3，自引：0，他引：3  

Mare J. Defant  Lee F. Clark  Robert H. Stewart  Mark S. Drummond  Jelle Z. de Boer  René C. Maury  Hervé Bellon  Thomas E. Jackson  Juan F. Restrepo 《Contributions to Mineralogy and Petrology》1991,106(3):309-324

The easternmost stratovolcano along the Central American arc is El Valle volcano, Panama. Several andesitic and dacitic lava flows, which range in age 5–10 Ma, are termed the old group. After a long period of quiescence (approximately 3.4 Ma), volcanic activity resumed approximately 1.55 Ma with the emplacement of dacitic domes and the deposition of dacitic pyroclastic flows 0.9–0.2 Ma. These are referred to as the young group. All of the samples analyzed are calc-alkaline andesites and dacites. The mineralogy of the two groups is distinct; two pyroxenes occur in the old-group rocks but are commonly absent in the young group. In contrast, amphibole has been found only in the young-group samples. Several disequilibrium features have been observed in the minerals (e.g., oscillatory zoning within clinopyroxenes). These disequilibrium textures appear to be more prevalent among the old- as compared with the young-group samples and are most likely the result of magma-mixing, assimilation, and/or polybaric crystallization. Mass-balance fractionation models for major and trace elements were successful in relating samples from the old group but failed to show a relationship among the young-group rocks or between the old- and young-group volcanics. We believe that the old-group volcanics were derived through differentiation processes from basaltic magmas generated within the mantlewedge. The young group, however, does not appear to be related to more primitive magmas by differentiation. The young-group samples cannot be related by fractionation including realistic amounts of amphibole. Distinctive geochemical features of the young group, including La/Yb ratios〉15, Yb〈1, Sr/Y〉150, and Y〈6, suggest that these rocks were derived from the partial melting of the subducted lithosphere. These characteristics can be explained by the partial melting of a source with residual garnet and amphibole. Dacitic material with the geochemical characteristics of subducted-lithosphere melting is generated apparently only where relatively hot crust is subducted, based on recent work. The young dacite-genesis at El Valle volcano is related to the subduction of relatively hot lithosphere.  相似文献   

亚欧500hPa旬平均形势预报的改进及检验     

任金声  李晓东  林玉成  吴金瑞 《气象》1994,20(9):34-37

利用数值预报产品，对原亚欧５００ｈＰａ旬平均形势预报方程作了改进。除对空间和时间尺度上作了改进外，在预报因子的选择上，由亚欧地区的单点相关，扩张至整个北半球的相关；并根据长波天气系统的气候地理分布和遥相关分析等方法，选择关键区作为候选因子，组建了新的形势预报方程。经检验比较，新的形势预报方程高度距平正确和长波系统位置正确率分别提高了０．１５－０．２０和０．１０。  相似文献   

浙江杭嘉湖平原区土壤中营养元素丰缺状况的评价   总被引：5，自引：2，他引：5  

朱立新  周国华  任天祥  张连生  王徽  顾金秋  杜雄进  王成  蒋永平  周子泉 《物探与化探》1994,18(4):251-262

根据杭嘉湖平原区区域地球化学调查的结果,对本区土壤中农作物营养元素含量及有效量特征进行了评价研究。研究结果表明,本区土壤中营养元素除Mo、S含量表现缺乏外,其它元素为足量和丰富水平。不同土壤中营养元素有效量水平存在明显差异。在区域分布规律上,营养元素的含量及有效量随成土母质、成土过程和人类耕作等因素的不同而显示其差异特征。评价研究结果为本区农业生产中的合理区划、科学施肥、合理种植、土壤改良等提供了重要的地球化学依据。  相似文献   

用石灰桩加固软弱地基   总被引：7，自引：1，他引：7  

汪稔  陈善雄 《岩土力学》1994,15(3):19-25

石灰桩作为一种技术可靠、经济快速的软弱地基加固方法已得到了广泛应用。本文介绍了武汉岩土力学研究所近一年来利用石灰桩处理软弱地基的成功经验。现场检测表明，对于单层和多层工业与民用建筑而言，采用石灰桩可以使软弱地基获得良好加固且满足设计要求。文中还对石灰桩的加固机理进行了简要分析。  相似文献   

大气气溶胶的粒度谱分布函数及其随高度的变化   总被引：10，自引：2，他引：10  

王明星  任丽新  吕位秀 《大气科学》1984,8(4):435-442

本文对用光学粒子计数器在飞机上测量的大气气溶胶数密度-粒度谱分布进行了分析研究.根据对气溶胶谱形成过程的分析,指出大气气溶胶是四种气溶胶体系的混合物,需要用四个正态分布函数的和来描述大气气溶胶的体积-粒度谱分布.用非线性最小二乘法计算了谱分布函数的经验参数;研究了粒子浓度、体积、及粒度谱分布函数随高度的变化.观测资料表明,在大气温度和湿度水平均匀、层结稳定的情况下,气溶胶粒子浓度水平分布不均匀,而且垂直方向上也并不随高度单调递减.  相似文献   

Geochemical characteristics of tin-bearing magnetite-skarns     

Zhiji Ren 《中国地球化学学报》1984,3(2):115-127

Geological and geochemical characteristics of tin-bearing magnetite-skarns are reviewed in this paper, together with the author’s opinion with respect to the mechanism of transport of tin in this environment. In addition to cassiterite, the most common form of occurrence of tin in nature, three other forms of occurrence are also of interest in tin-bearing magnetite-skarns: (1) tin present in the form of fine exsolution colloidal grains of cassiterite; (2) tin found as independent tin-bearing minerals, such as malayaite, stokesite, nordenskiöldine, Sn-paigeite, Sn-ludwigite and hulsite in a variety of skarns; (3) tin occurring in the lattice of some skarn minerals, such as garnet, pyroxene, spinel, amphibole, epidote, wollastonite and axinite in the manner of ionic replacement. When Mg²⁺ and Fe²⁺ bearing minerals, in some cases even Sulfides or other mineralizer-containing minerals, replace tin-bearing Fe³⁺ and Ti⁴⁺ skarn minerals during the late stage of skarn alteration, tin in the pre-existing silicates maybe extracted and remobilized, thus contributing to the formation of associated tin deposits.  相似文献   

The abnormal periods of climate in china over the past 5000 years and their causes     

Ren Zhenqiu 《大气科学进展》1987,4(2):210-217

This paper points out that (1) there were 5 abnormal periods of climate in China over the last 1000 years, in which the frequency, the severity and the influenced area of such calamities as low temperature, drought and flood increased greatly; (2) there were 3 or 4 worse periods of climate over the past 5000 years which were more severe than the above-mentioned climate; (3) the momental effect of the geocentric synods of nine plan-ets is one of the important causes for the formation of the abnormal and worse periods of climate; and (4) from the 1960s to about 2000 A.D. China and the entire Northern Hemisphere would probably undergo another ab-normal period of climate.  相似文献   

江西某地钨、碲、铋石英脉型矿床地质及碲的赋存状态          下载免费PDF全文

任英忱  程敏清  王存昌 《地质找矿论丛》1986,(1):57-69

碲是很有价值的分散元素,在国外已得到了广泛的应用.碲主要应用在钢铁工业上,其次才是有色金属工业和化工上.过去,认为碲的主要矿床是超基性岩铜镍矿床和火山岩中的块状硫化矿床,而对钨、铋石英脉中含碲则了解甚少.经过研究,认为钨、铋石英脉型矿床中碲的品位高、碲呈独立矿物存在,规模可达大中型,是独立的钨、碲、铋矿床.  相似文献