Statistical analysis of granophyric intergrowths in the Main Hill Arkasani Granophyre Pluton, eastern India     

B. Chattopadhyay 《Mathematical Geology》1990,22(5):589-598

The Main Hill Arkasani Granophyre Pluton (MAG), a product of Proterozoic intraplate acid magmatic activity, represents an anatectic melt of the enveloping rocks of dominantly pelitic composition with subordinate trondhjemitic gneiss and basic rocks. Petrography, chemistry, correlation between compositional attributes, areal variation of volume percent granophyric intergrowth, and varimax rotated factor analysis of compositional attributes of these rocks suggest that in the MAG pluton, plagioclase phenocrysts and biotite crystallized first, followed by change of level of emplacement of the magma when the groundmass started crystallizing at a rapid rate. The rapid growth of quartz and alkali feldspar crystallizing from the residual melt gave rise to the ubiquitous granophyric intergrowth in the late stage of crystallization. The alkali-rich residual liquid tended to concentrate toward the margin of the pluton where there is a profusion of granophyric intergrowths.  相似文献   

NUMERICAL EXPERIMENTS ON THE EFFECT OF QINGHAIXIZANG PLATEAU SNOW COVER ON SUMMER MONSOON FORMATION          下载免费PDF全文

Zhang Zhengqiu  Li Weiliang  Chen Longxun 《Acta Meteorologica Sinica》1991,5(4):442-455

The calculating schemes of underlying surface processes in the model described by Li et al.(1989)are modified with inclusion of simple land surface processes and oceanic mixed layer processes,then a simulation on the zonal wind along 90°E from the Northern to the Southern Hemisphere with moun-tains is performed.Comparisons of the results and the observations show that the modified model not onlyhas an excellent stability in calculation but also can better display the seasonal change of the wind field,theability of the present model is improved as compared with that of the previous one.Based on the simulations,the authors investigate the effects of Qinghai-Xizang Plateau snow cover on theformation of South Asian monsoon by thickcning the snow depth and by increasing the snow albedo.Themain results arc as follows:The summer meridional circulation over the south of the Plateau and its vicinityis weakeued,and the precipitation reduced.However,over the northern tropics,the circulation is enhanced,and the ecipitation is increased,and the land and the air above it become warmer,the tropical easterly jetis weakened.  相似文献   

The impact of high altitude aircraft on the ozone layer in the stratosphere     

Xue Xi Tie  Guy Brasseur  Xing Lin  Pierre Friedlingstein  Claire Granier  Philip Rasch 《Journal of Atmospheric Chemistry》1994,18(2):103-128

The paper discusses the potential effects on the ozone layer of gases released by the engines of proposed high altitude supersonic aircraft. The major problem arises from the emissions of nitrogen oxides which have the potential to destroy significant quantities of ozone in the stratosphere. The magnitude of the perturbation is highly dependent on the cruise altitude of the aircraft. Furthermore, the depletion of ozone is substantially reduced when heterogeneous conversion of nitrogen oxides into nitric acid on sulfate aerosol particles is taken into account in the calculation. The sensitivity of the aerosol load on stratospheric ozone is investigated. First, the model indicates that the aerosol load induced by the SO₂ released by aircraft is increased by about 10–20% above the background aerosols at mid-high latitude of the Northern Hemisphere at 15 km for the NASA emission scenario A (the NASA emission scenarios are explained in Tables I to III). This increase in aerosol has small effects on stratospheric ozone. Second, when the aerosol load is increased following a volcanic eruption similar to the eruption of El Chichon (Mexico, April 1982), the ozone column in spring increases by as much as 9% in response to the injection of NO _x from the aircraft with the NASA emission scenario A. Finally, the modeled suggests that significant ozone depletion could result from the formation of additional polar stratospheric clouds produced by the injection of H₂O and HNO₃ by the aircraft engines.  相似文献   

南方大到暴雪的一种预报方法   总被引：3，自引：1，他引：3  

高智松  魏柏温 《气象》1994,20(4):41-43

对构成南方大到暴雪的两个特征量：降水量和积雪深度用多种预报方法从晴雨、降水性质、降水量级、冰冻及积雪厚度等不同角度分别进行预报，然后通过推理组合，最终建立暴雪预报方法。该方法除了可以得出有无大到暴雪的预报结果外，还可以得到多种中间预报结果，从而适应预报服务的多种需要。在近３年的实际使用中获得了很好的效果。  相似文献   

东台吉乃尔盐湖卤水的相化学研究（Ⅱ）—冬夏季卤水蒸发实验   总被引：1，自引：0，他引：1       下载免费PDF全文

张宝全  刘铸唐 《盐湖研究》1994,2(3):27-34

为了研究东台吉乃尔盐湖卤水蒸发时的相化学，确定钾、镁和锂盐的结晶特性，在实验室内２５℃等温蒸发实验基础上和自然条件下进行了冬夏季日晒蒸发试验．东台吉乃尔盐湖卤水是由氯化钠饱和的多组分复杂体系构成的．卤水中存在的离子是Ｎａ＋、Ｋ＋、Ｍｇ２＋、Ｌｉ＋、Ｃａ２＋、Ｂ３＋、ＳＯ４２－和Ｃｌ－．试验数据与Ｎａ＋、Ｋ＋、Ｍｇ２＋Ｃｌ－、ＳＯ４２－ＫＨ２Ｏ五元体系介稳平衡数据进行了讨论和比较．Ａｕｔｅｎｒｉｅｔｈ相图被用来表示各数据间的关系和证明冬夏季蒸发时结晶行为的差别．  相似文献   

Crystal structure refinement of hendricksite,A Zn- and Mn-rich trioctahedral potassium mica: A contribution to the crystal chemistry of zinc-bearing minerals     

Dr. J. -L. Robert  Dr. M. Gaspérin 《Mineralogy and Petrology》1985,34(1):1-14

Summary The crystal structure of hendricksite, a trioctahedral mica of biotite type, characterized by high Zn²⁺ and Mn²⁺ contents has been refined by least square methods. The structural formula is: (K_0.89Na_0.10Ba_0.04)(Mg_1.57Zn_0.54Mn _0.40 ²⁺ Fe _0.25 ²⁺ Al_0.07Ti_0.07Cr_0.01)(Si_2.92Al_1.08)O₁₀ (OH)₂. The space group isC2/m and the cell parameters are:a=5.340(2) Å,b=9.524(2) Å,c=10.235(3) Å, =100.07(2)^o, the cell volume isV=497.98 ų. The final unweightedR=0.072. Average cation-anion distances in polyhedra are: T–O=1.659 Å, M(1)–O=2.093 Å, M(2)–O=2.088 Å, A–O_long=3.316 Å and A–O_short=3.004 Å; A is the alkaline cation. The rotation angle of tetrahedra is =6.7°. The analysis of electron densities, of the dimensions and distorsions of polyhedra shows that Zn²⁺ is exclusively in octahedral sites; there is no order between six-fold coordinated cations. A comparison between the structural features of hendricksite and those of the two main end-members of biotites, phlogopite and annite, is presented.The effect of the strong covalence of Zn–O bonds is particularly visible on the dimensions and orientations of the thermal ellipsoids of octahedral sites M(1) and M(2) which contain zinc. In all the published structures of trioctahedral micas, the ellipsoids of cationic sites are uniaxial positive, elongated parallel toc ^*. In hendricksite, this is observed only for the two zinc-free sites (T and A; in the octahedra M(1) and M(2), which contain zinc, the ellipsoids are approximately uniaxial negative, flattened parallel toa, which is a unique situation.Zinc which habitually favours the tetrahedral coordinations with oxygen, enters the octahedra only, i.e. the chemically anisotropic sites, in hendricksite. The strong polarizability of Zn²⁺ is proposed to explain this behaviour.An examination of the behaviour of Zn²⁺ in other compounds shows that this situation is general, zinc favours chemically anisotropic sites and specially those adjacent to OH or H₂O.

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Affinement de la structure cristalline de la hendricksite, mica trioctaédrique potassique riche en Zn et Mn; une contribution à la connaissance cristallochimique des minéraux zincifères

Résumé On a affiné par moindres carrés la structure de la hendricksite, mica trioctaédrique de type biotite, caractérisé par une teneur élevée en Zn²⁺ et Mn²⁺. La formule structurale de ce mica est: (K_0m89Na_0,10Ba_0,04)(Mg_1,57Zn_0,54Mn _0,40 ²⁺ Fe _0,25 ²⁺ Al_0,07Ti_0,07Cr_0,01)(Si_2,92Al_1,08)O₁₀(OH)₂. Le groupe spatial estC2/m et les paramètres de la maille:a=5,340(2) Å,b=9,254(2) Å,c=10,235(3) Å, =100,07(2)°; le volume de la maille estV=497,98 ų. Le résidu final non-pondéré estR=0,072. Les distances cation-anion moyennes dans les polyèdres sont les suivantes: T–O=1,659 Å, M(1)–O=2,093 Å, M(2)–O=2,088 Å, A–O_long=3,316 Å et A–O_court=3,004 Å où A désigne le cation alcalin. L'angle de rotation tétraédrique, =6,7°, est très semblable à celui de la phlogopite. L'analyse des densités électroniques, des dimensions et distorsions des polyèdres montre que Zn²⁺ est exclusivement en coordinance octaédrique et qu'il n'y a pas d'ordre entre les cations hexacoordonnés. On présente une comparaison des caractères structuraux de la hendricksite avec ceux des deux principaux pôles des biotites, la phlogopite et l'annite.L'effet de la forte covalence de la liaison Zn–O est particulièrement visible sur les dimensions et orientations des ellipsoides d'agitation thermique des deux sites octaédriques, sites zincifères. Dans toutes les structures de micas trioctaédriques publiées, les ellipsoides des sites cationiques sont uniaxes positifs, allongés parallèlement àc ^*, ce qui s' observe effectivement dans les deux sites non-zincifères (T et A) de la hendricksite, par contre, dans les octaèdres M(1) et M(2), qui contiennent le zinc, les ellipsoides sont approximativement uniaxes négatifs, applatis parallèlement àa, ce qui est une situation unique.Le zinc, qui se fixe généralement en sites tétraédriques dans les structures de type oxyde, occupe les sites octaédriques, c'est-à-dire les sites chimiquement anisotropes dans la hendricksite. La forte polarisabilité de Zn²⁺ est proposée pour expliquer ce comportement.Un examen du comportement de Zn²⁺ dans d'autres phases montre que cette situation est tout à fait générale, le zinc privilégiant les sites chimiquement anisotropes et en particulier ceux adjacents à OH où H₂O.

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Human influence upon sedimentation in Llangorse Lake,Wales     

R Jones  K. Benson-Evans  F. M. Chambers 《地球表面变化过程与地形》1985,10(3):227-235

Palaeolimnological studies at Llangorse Lake, Wales, constitute part of the British contribution to IGCP Project 158 (The Palaeohydrology of the Temperate Zone in the Last 15000 Years). The lake has been adopted as the Reference Site for the South Wales region under Subproject 158B (Lake and Mire Environments) and is located in the Reference Area for Britain: the Severn Basin. Results of biological, physical, and multielement chemical analyses on a 12.35 m Livingstone core are presented and compared with previous analyses on short Mackereth cores taken from two troughs in the lake basin. Human impact upon post-glacial sedimentation is assessed with reference to sediment chemistry, physical properties, and sedimentation rates, based on relative pollen, ¹⁴C, and ²¹⁰Pb dating. Vegetational history of the catchment is inferred from a pollen diagram for a section of the core from c. 8 to 6.75 m depth in which evidence for human impact is first apparent. Water content, loss on ignition, and carbonate content are presented for the whole core; density, water content, loss on ignition, carbonates, and elemental analyses of P, Ca, Mg, K, Ti, Al, Fe, and Mn for the interval 6 75 and 8.25 m depth. Sedimentation rates were low during Boreal and Atlantic times (c. 9000- 5000 BP), rose significantly from the time of the elm decline (estimated at 5000 BP) and increased further at c. 1800 BP when nekron muds were succeeded by deposition of silty clay. Inferred rates of erosion of soils from the catchment are discussed and related to sediment chemistry.  相似文献   

A world model of soil carbon dioxide: A reply     

George A. Brook  Elgene O. Box 《地球表面变化过程与地形》1984,9(1):85-87

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陕西略阳煎茶岭镍矿床成矿及矿石变质过程的地球化学研究     

Zhang Benren Chen Dexing Hu Yikeng 《地球科学》1986,(4)

矿床中存在着岩浆离熔成因的磁黄铁矿-镍黄铁矿矿石和热液改造成因的黄铁矿-针镍矿-辉镍矿矿石。研究证明现在矿石中存在的硫化物均为较低温度条件下的变质产物,并且矿物组合的更替不仅同温度变化有关,同时还受体系中氧逸度和硫离子活度的控制。矿物组合的地球化学分析表明,现有Fe-Ni-S体系低温（<300℃）相平衡图解之间存在着矛盾的原因可能是忽略了氧化-还原条件的影响。  相似文献   

金矿床石英中负价氮的发现及赋存状态探讨     

许虹  田丽华 《吉林大学学报(地球科学版)》1995,(1)

利用ｘ光电子能谱测试，发现金矿床石英中有负价氮的存在。这种氮的结合能为３９８ｅＶ士，该结合能氮的化合物有多种，氦均为负价态，其中有Ｓｉ＿３Ｎ＿４Ｓｉ的ｘ光电子能谱有二个谱峰值：１０３．４ｅＶ和１０１．９ｅＶ，前者为ｓｉＯ＿２的结合能，后者为Ｓｉ＿３Ｎ＿４的结合能。Ｎ和Ｓｉ的结合能均表明石英中有Ｓｉ＿３Ｎ＿４为负三价态。石英中负价Ｎ可能为替代氧的类质同象成分。  相似文献