Advances in our understanding of the gem corundum deposits of the West Pacific continental margins intraplate basaltic fields   总被引：2，自引：1，他引：1  

Ian Graham  Lin Sutherland  Khin Zaw  Victor Nechaev  Alexander Khanchuk 《Ore Geology Reviews》2008,34(1-2):200

Recent discoveries over the last decade of new gemfields, exploitation of new and existing deposits, and application of relatively new techniques have greatly increased our knowledge of the basalt-derived gem sapphire–ruby–zircon deposits. In this paper we focus on the Late Mesozoic to Cenozoic intraplate basaltic fields of the West Pacific continental margins. We review advances made in understanding the genesis of these deposits, based on the application of newer techniques. We also critically review existing data on the gem corundum deposits, in order to further refine a model for their origin.In some of the intraplate basaltic fields, corundum-bearing xenoliths have been found showing a range of PT formation conditions from 790 °C at 0.85 GPa to as much as 1100 to 1200 °C at 1.0 to 2.5 GPa. Although most magmatic sapphires contain syngenetic inclusions of columbite-group phases, zircon, spinel and rutile, some contain additional nepheline and K-feldspar, suggesting crystallization from more undersaturated alkaline magma while the Weldborough field of NE Tasmania also contains molybdenite and beryl, suggesting at least some interaction with more fractionated ‘granitic-type’ magmas. There is a large range in PT conditions calculated for the metamorphic rubies (from 780 to 940 °C, through 800 to 1150 °C up to 1000 to 1300 °C). Fluid/melt inclusion studies on magmatic corundums generally suggest that they formed in a CO₂-rich environment from a ‘syenitic’ melt under a range of T conditions from 720 to 880 °C up to 1000 to 1200 °C. Oxygen isotope studies reveal that typical magmatic corundums have values of + 4.4 to 6.9‰, whereas metamorphic corundums from the same basaltic host have lower values of + 1.3 to 4.2‰.Geochronological studies have shown that some fields produced a simple eruptive and zircon/corundum crystallization event while others had multiple eruptive events but only one or two zircon crystallization events. For a few fields, some corundums/zircons crystallized in storage regions and then remained relatively inert for periods of 200 to 400 Ma without significant change before transport to the surface in the Cenozoic. Tectonic studies of the Australian region suggest that many of the corundums crystallized from magmas related to episodic basaltic volcanism in a tectonic regime of extension, associated with the opening of the Tasman and Coral Seas. For the Asian region, the magmatic–polygenetic corundums within the basaltic fields largely crystallized in a tectonic regime of distributed E–W extension, whereas the metamorphic-metasomatic corundums crystallised in a transpressional regime associated with the collision of the Indian Plate with the Eurasian Plate (e.g., [Garnier, V., Giuliani, G., Maluski, H., Ohnenstetter, D., Deloule, E., 2003. Ar–Ar and U–Pb ages of marble-hosted ruby deposits from Central and South-east Asia. Geophysical Research Abstracts 5, 03751; Garnier, V., Giuliani, G., Ohnenstetter, D., and Schwarz, D., 2004. Les gisements de corindon: classification et genese. Les placers a corindon gemme. Le Regne Mineral 55, 7-47; Garnier, V., Ohnenstetter, D., Giuliani, G., Maluski, H., Deloule, E., Phan Trong, T., Pham Van, L., Hoang Quang, V., 2005a. Age and significance of ruby-bearing marble from the Red River Shear Zone, Northern Vietnam. Canadian Mineralogist 43, 1315–1329]).  相似文献   

水产饲料膨化机设计刍论     

徐钟良  陈启发 《台湾海峡》2001,20(Z1):207-211

据开发应用水产饲料膨化机实践，初步论述了膨化机生产能力与动力匹配，螺杆设计参数长径比，物料在腔内滞留时间，膨化腔设计及其温度调控，并提出改进设计的见解.  相似文献   

大型钢结构变形测试方法的研究与实践     

潘国荣 《测绘信息与工程》2005,30(3):45-47

介绍了精密全站仪进行结构测试的原理和方法,通过对某大型游泳跳水馆钢结构网架在张拉和加载试验中的变形测量实践,证明其具有作业简便、能够全面反映结构变形情况之优点,且精度较高,成果可靠。  相似文献   

半无限空间中圆形孔洞周围SH波的散射   总被引：14，自引：5，他引：14  

林宏  刘殿魁 《地震工程与工程振动》2002,22(2):9-16

建立了求解在含有圆形孔洞的弹性半空间中SH波散射与圆形孔洞附近动应力集中问题的解析方法。利用SH波散射的对称性和多极坐标的方法，构造了一个可以预先满足半空间自由表面上应力自由边界条件的圆形孔洞对SH波散射的波函数。利用这一波函数，则可将该问题转化成对一个圆形孔洞散射的求解问题。该问题的解答最终又可归结为对一组无究代数方程组的求解问题，并可利用截断有限项的方法对其进行计算，最后给出了有关圆形也洞附近动应力集中问题的算例和数值结果，并讨论了波数与圆孔至自由边界距离变化对动应力集中的影响。  相似文献   

空腔结构复合填充墙-钢框架抗侧力性能试验研究   总被引：4，自引：0，他引：4  

管克俭  李捍无  彭少民 《世界地震工程》2003,19(3):73-77

通过空腔结构复合填充墙-钢框架和同尺寸纯钢框架的对比试验，分析了空腔结构复合填充墙-钢框架的抗侧力性能和滞回性能。研究结果证明空腔结构复合填充墙是一种理想的抗侧力体系，可用于多层或小高层钢结构住宅，作为结构的抗侧力构件。  相似文献   

基于统一强度理论的柱形孔扩张问题研究   总被引：5，自引：1，他引：5  

王延斌  范文  徐栓强 《岩土力学》2003,(Z2)

考虑了岩土材料的软化和剪胀特性,利用空间轴对称问题的统一强度理论分析了柱形孔扩张问题,求出了岩土材料在柱形孔扩张时的应力场、应变场、位移场和最终扩张压力的统一解表达式。对蒋明镜-沈珠江扩孔公式从不同的方面作了论述。通过算例分析了岩土材料的软化和剪胀特性以及统一强度理论参数对应力场、位移场和扩张压力的影响。已有的关于该问题的Tresca解和Mohr-Coulomb解均为本文的一个特例。  相似文献   

宜兴抽水蓄能电站试验洞的反分析研究   总被引：4，自引：2，他引：4  

杨林德  仇圣华  王悦照  丁文其  朱合华 《岩土力学》2003,(Z2)

结合江苏宜兴抽水蓄能电站地下厂房试验洞量测资料的分析,研究了成层各向异性岩体中洞室工程问题的反分析方法。采用分层均质模型进行反分析计算。计算区域的各层岩层均被分别视为均质各向同性体,初始地应力假设呈线性分布。有限元分析中,对倾斜成层的岩层、软弱夹层及断层节理等分别划分了单元,据以模拟成层岩体的各向异性特征。为使计算过程简化,对离洞室较远的岩层拟按地质资料对材料特性参数赋值,反分析计算的目标未知数为初始地应力和试验洞相邻围岩的弹性模量。结果表明,与工程实践符合较好。  相似文献   

Seismic moment tensor representations and radiation patterns in unbounded media with elipsoidal cavities driven by low frequency pressure     

靳平  徐果明  楼为涛 《地震学报(英文版)》1997,10(5):553-564

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Crater formation in soils by raindrop impact     

Hossein Ghadiri 《地球表面变化过程与地形》2004,29(1):77-89

The process of crater formation by the impact of water drops on soil, sand and various other target material was studied. Craters of various shapes and sizes were observed on different target materials or conditions, ranging from circumferential depression to completely hemispherical shape. Crater shape was dependent upon target material, its ?ow stress or shear strength and the presence and thickness of water on the surface. Between 5 and 22 per cent of impact energy was spent on cratering, but the relationship between crater volume and kinetic energy of a raindrop was curvilinear, indicating a lower ef?ciency of impact energy in removing target material as the energy increases. Impact impulse, on the other hand, showed a more linear relationship with crater volume, and the ratio of impulse over crater volume (I/V) remained constant for the entire range of drop sizes, impact velocities, and surface conditions used in this study. Surface shear strength, represented by the penetration depth of fall‐cone penetrometer, appeared to be a key factor involved in this process. An equation was developed which related crater volume to cone penetration depth and impact impulse. Crater volume, which appeared to be a better indicator of the total amount of material dislodged by a raindrop than splash amount, can thus be predicted using this equation. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Method of high-density seismic imaging ex-ploration and application samples     

熊章强  张学强  李修忠  谢尚平  张大洲 《地震学报(英文版)》2004,17(3):344-348

Introduction Now, shallow seismic reflection wave technique has been used extensively in geological ex-plorations of bridge, dam, high building and so on. Since shallow seismic reflection wave tech-nique is often implemented in industrial zone or city with dense population, the background dis-turbance including industrial noise, life noise, etc is very serious. Furthermore, the disturbance of seismic source is also serious due to short array length and offset of the method. In general, shal-lo…  相似文献