排序方式： 共有27条查询结果，搜索用时 15 毫秒
21.
We report a comparative study on the high pressure (HP) structural behaviour of a fibrous zeolite (with EDI topology) on the basis of rigid unit modes (RUM) modelling and previously published single-crystal X-ray diffraction. HP single-crystal diffraction data lead to a more precise determination of the elastic parameters (axial and volume compressibilities) useful to define the equation-of-state under isothermal conditions, and the structural refinements are useful to describe the main deformation mechanisms of the Si/Al framework and extra-framework content at high pressure. The RUM modelling is applied to simulate the compressive behaviour of the framework, under hydrostatic and non-hydrostatic conditions, using a minimum number of parameters, and to describe the deformation mechanism intuitively in terms of the rotations of the SiO4 polyhedra. The local and global P-induced deformation mechanisms of the Si/Al framework observed in experiment (channel ellipticity, SBU rotation) are well reproduced by RUM modelling. The simulation of uniaxial compression (non-hydrostatic conditions) shows an interesting result on the structural behaviour. This comparative study tests the reliability of the RUM modelling in open-framework silicates with a complicated crystal structure.Electronic Supplementary Material: Supplementary material to this paper is available in electronic form at 相似文献
22.
辽宁岫岩玉的特征及其质量研究 总被引：1，自引：0，他引：1
辽宁岫玉主要由叶蛇纹石组成,其叶片大小多为 300nm×440nm,沿a轴方向呈波状起伏.岫玉中的矿物生成次序为粗粒透闪石→细粒透闪石→滑石→叶蛇纹石.岫玉的颜色主要受TFeO含量及Fe2O3/FeO值制约,透明度也受其直接影响.绿色、油青色是岫玉的原生色;棕色、红棕色形成于氧化环境,是次生色.颜色和透明度是岫玉质量评价的两个主要指标. 相似文献
23.
岫岩玉是我国的主要玉种之一,属于蛇纹石玉。在X射线衍射、红外光谱、可见光吸收谱,及电子显微镜等项研究确切查明主体矿物为叶蛇纹石的基础上,选两个优质玉样进行~(57)Fe穆斯堡尔谱学研究。岫岩玉的穆斯堡尔谱由两组四级双峰构成,第一组双峰(δ=1.12,△=2.73与2.72mm/s)系由镁氧八面体中的Fe~(2+)形成,另组双峰(δ=0.35与0.36,△=0.63与0.55mm/s)反映的是镁氧八面体中的Fe~(3+),Fe~(3+)/Fe~(2+)分别为0.90与0.78。铁是参与叶蛇纹石晶格的组分;Fe~(3+)与Fe~(2+)均处镁氧八面体中;Fe~(3+)/Fe~(2+)近于与小于1是制约它呈绿色的主要因素。 相似文献
24.
本文通过一条剖面的重点解剖,研究了广泛分布于上扬子台地边缘相碳酸盐岩中的玛瑙纹构造的成因。研究表明,这是一种早期的成岩组构,组成成分为纤状方解石和粒状方解石。沉淀介质为溶解了部分地表藻类的淡水同孔隙和裂隙海水发生不同程度混合的混合水溶液。被玛瑙纹充填的围岩裂隙主要由岩溶坍塌作用造成,但也有牵引拉伸裂隙和暴露收缩裂隙的叠加。由于介质溶液以地下潜水方式侧向运动,因而随潜水面波动形成了间隔的多层状含玛瑙纹岩层。 相似文献
25.
Wang Miao Chen Yong Xu Xingyou Zhang Xuejun Han Yun Wang Chengjun Cao Mengchun 《地球科学进展》2015,30(10):1107-1118
The fibrous mineral veins are widespread in mudstones. According to the different microscopic morphology of the minerals, the fibres can be divided into stretched crystals, elongate-blocky crystals and the very fibrous crystals. Veins can also be classified according to the growth direction of these crystals into stretched veins, syntaxial veins and antitaxial veins. The resulting texture in the vein depends on the morphology of the fracture surface, the width of the fracture and the growth habit of the vein forming mineral. The crack-seal mechanism can only interpret the formation of the stretched crystal veins and the elongate-blocky crystal veins, and the antitaxial well-developped fibrous veins form without fracturing and the growth competition is inhibited during the rock deformation, which implies that the nutrient transport is by diffusional flow transport. Horizontal crack is the primary condition of the formation of the antitaxial bedding-parallel fibrous calcite veins in muddy hydrocarbon source rocks. The formation of the horizontal crack which caused by the abnormal high pressure can enhance the hydrocarbon generation efficiency and has a great effect on the rate and direction of hydrocarbon migration in the local. The presence of the veins indicates the hydrocarbon fluid can migrate laterally along the layers. The antitaxial bedding-parallel fibrous calcite veins in muddy hydrocarbon source rocks can be the sign of the generation and migration of hydrocarbon under the abnormal high pressure condition in petroleum-bearing basins. 相似文献
26.
The Zermatt‐Saas serpentinite complex is an integral member of the Penninic ophiolites of the Central Alps and represents the mantle part of the oceanic lithosphere of the Tethys. Metamorphic textures of the serpentinite preserve the complex mineralogical evolution from primary abyssal peridotite through ocean‐floor hydration, subduction‐related high‐pressure overprint, meso‐Alpine greenschist facies metamorphism, and late‐stage hydrothermal alteration. The early ocean floor hydration of the spinel harzburgites is still visible in relic pseudomorphic bastite and locally preserved mesh textures. The primary serpentine minerals were completely replaced by antigorite. The stable assemblage in subduction‐related mylonitic serpentinites is antigorite–olivine–magnetite ± diopside. The mid‐Tertiary greenschist facies overprint is characterized by minor antigorite recrystallization. Textural and mineral composition data of this study prove that the hydrated mineral assemblages remained stable during high‐pressure metamorphism of up to 2.5 GPa and 650 °C. The Zermatt‐Saas serpentinites thus provide a well documented example for the lack of dehydration of a mantle fragment during subduction to 75 km depth. 相似文献
27.
F. Burragato P. Comba V. Baiocchi D. M. Palladino S. Simei A. Gianfagna L. Paoletti R. Pasetto 《Environmental Geology》2005,47(6):855-868
The town of Biancavilla, located on the lower flanks of Mt. Etna volcano, eastern Sicily (Italy), showed high mortality rates owing to malignant pleural neoplasms, a cause of death specifically related to exposure to asbestos fibres. An environmental survey indicated the stone quarry site of Il Calvario as a possible source of asbestos fibre exposure, while a mineralogical study allowed to identify the new asbestiform mineral fluoro-edenite. A joint epidemiological and environmental study was conducted to assess the characteristics of the outbreak of malignant mesothelioma and to test the assumption of a causal relation with exposure to fluoro-edenite. Due to the lack of awareness of fluoro-edenite releases, Il Calvario may not be the only source of the fibre, but is probably the main one. The evolution of the volume of material quarried from Il Calvario was studied on the basis of maps printed from 1896 to 1995, by using a digital elevation model. The natural and anthropogenic causes of the territorial spread of the newly discovered amphibole fibres are discussed relatively to a geo-volcanological, territorial and environmental evolution of the area affected. 相似文献