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21.
Scanning electron microscopy of quartz grains in supraglacial debris, Adishy Glacier, Caucasus Mountains, USSR 总被引:7,自引:0,他引:7
WILLIAM C. MAHANEY REIN VAIKMAE KAI VARES 《Boreas: An International Journal of Quaternary Research》1991,20(4):395-404
The surface microtopography of quartz grains in glacial depostis has often been attributed to mechanical release from source rocks during weathering and prior to entrainment by glaciers. Fractures on quartz particles, including subparallel and conchoidal features, often attributed to cryostatic pressure in ice and stick-slip processes at the base of glaciers, have been considered, in part, to result from mechanical weathering of source rocks. To test this hypothesis we studied 15 samples of supraglacial debris from the Adishy Glacier in the central Caucasus Mountains, USSR. Clasts in transport on the surface of the glacier originate primarily from the cirque headwall by weathering and mass wasting processes; a minor amount is presumed to have been derived from aeolian influx following reworking of older sediments down valley. The results show unequivocally that mechanical weathering is only likely to produce grains with pronounced fracture faces that lack subparallel and conchoidal fracture features. No fresh glacial-crushing type features were observed on these samples. Grains that had been glacially crushed, weathered and retransported, presumably by aeolian processes, were observed in four samples of the data set. 相似文献
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Within the Isortoq Complex of central West Greenland, doleritedykes have been metamorphosed in upper amphibolite to garnetgranulite facies. Detailed sampling and petrographic study ofthese dykes demonstrate that the entire sequence of assemblagesmay occur in individual dykes, with the amphibolite facies assemblagesnormally restricted to dyke margins, garnet granulite faciesrocks occurring in the dyke cores, and pyroxene granulite faciesrocks intervening between these two. Electron microprobe analysisof all coexisting phases demonstrates that the progression fromamphibolite facies to granulite facies assemblages results inthe extraction of edenite and tschermakite components from theamphibole in approximately a 2: 1 ratio. As amphibole breakdownproceeds, systematic changes in element abundance within amphiboleoccur when reactions are crossed, due to the development ofnew phases. The algebraic removal of small but systematic compositionalvariations within the dykes allows derivation of six equilibria,which provide a general model for metamorphism of basaltic rocksunder high grade metamorphic conditions. This model takes theform of the idealized assemblage sequences which will developalong (regional) gradients in XH2O, temperature and/or solidpressure. Analysis of these equilibria demonstrates that variablesilica activity and Fe2+Mg2+ exchange will modify reactionstoichiometry, will affect the ratio of edenite to tschermakitein amphibole breakdown reactions, and will modify the compositionof the product plagioclase. These variations together with variationsin water fugacity will locally modify the ideal assemblage sequences,and will explain the complex assemblage relationships observedin metabasic rocks of natural high grade terranes.
*Present address: Instituttet for Teknisk Geologi, Danish Technical University, Building 204, DK2800 Lyngby, Denmark 相似文献
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鄂尔多斯盆地西缘冲断带是我国南北构造带的重要组成部分,是阿拉善地块与鄂尔多斯地块之间陆内构造变形的产物,研究其地质结构与构造样式是探讨陆内构造变形机制的基础,同时也是剖析地震活动与开展油气勘探的重要依据。本文基于该区近年来新的钻井、高精度二维与三维地震资料,应用构造解析方法,研究构造变形样式及圈闭分布特点。研究表明,马家滩地区地处鄂尔多斯盆地西缘冲断带中段,经历长期的伸展—聚敛旋回演化,是贺兰山—六盘山陆内造山带变形系统的一部分。马家滩地区的地质结构具有"分带、分层、分段"特征,自西向东发育后缘伸展带(银川地堑)、逆冲推覆构造带(包括韦州—苋麻湾冲断席、石沟驿向斜)、前缘过渡带和天环凹陷;前缘过渡带以石炭—二叠系煤层或泥岩为区域滑脱层分为上、下构造变形系统,下构造变形系统向西缓倾,发育低幅度背斜;上构造变形系统发育三排断层相关褶皱背斜带,向南变窄,上构造变形系统因滑脱层发育差异而南、北分段,二者之间斜向过渡转换。马家滩地区及邻区主要发育伸展-聚敛旋回制约的反转构造系统、陆内造山变形制约的扩展式前陆变形系统和后陆造山后伸展变形系统等3种构造变形系统;前缘过渡带上部构造系统经历印支晚期、燕山期和喜马拉雅期三期变形,形成不同期次、不同方向的叠加构造。马家滩地区发育断层传播褶皱、双重构造、叠瓦构造、构造楔和反冲断裂组合(冲隆构造)等构造样式,形成断背斜、断鼻及断块等油气圈闭类型,圈闭分布受断层控制呈带展布。马家滩地区构造圈闭发育,为西缘油气勘探的有利远景目标区。 相似文献
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以皂石、高岭石、绿泥石和伊利石为原材料,分别与赖氨酸进行反应,研究赖氨酸在上述粘土矿物上的吸附行为,
并运用粉末X-射线衍射技术(XRD)、傅里叶变换红外吸收光谱术(FTIR)和热重(TG)等分析方法,表征反应前后粘土
矿物的变化。实验结果表明,不同粘土矿物对赖氨酸的吸附等温线均符合Freundlich等温方程,且不同粘土矿物对赖氨酸的
饱和吸附量大小顺序为:皂石>蒙脱石>绿泥石>高岭石>伊利石;XRD结果表明皂石对赖氨酸的吸附发生在矿物层间,而绿
泥石、高岭石和伊利石对赖氨酸的吸附主要在矿物表面进行;FTIR和TG结果表明赖氨酸主要取代粘土矿物层间吸附水,以
氢键的形式与Si-O-Si(IVAl)键合。实验结果将有助于进一步探明环境中粘土矿物对有机质的吸附机理。 相似文献
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船舶螺旋桨尾流场的数值分析 总被引:16,自引:1,他引:16
利用基于速度势的低阶面元法计算船舶螺旋桨的尾流场。采用计算较为简捷的关于扰动速度势的基本积分微分方程,并采用双曲面形状的面凶以消除面元间的缝隙。Newton-Raphson迭代过程被用来在桨叶随边满足压力Kutta条件,使桨叶面上表面的压力在随边有良好的一致性。在计算面元的影响系数时,应用了Morino导出的解析计算公式,加快了数值计算的速度。从解面元法的基本积分方程得到的偶极强度和源汇强度,直接求得尾流场的速度分布。 相似文献