青藏高原祖尔肯乌拉山地区火山岩Ar-Ar年代学初步研究     

李保华  伊海生  林金辉  黄继钧  赵兵 《四川地质学报》2004,24(2):73-76

对祖尔肯乌拉山地区 4个火山岩样品进行了Ar -Ar年龄测定 ,其坪年龄分别为 (40 91± 1 18)Ma、(41 0 7± 0 80 )Ma、(42 0 0± 1 31)Ma、(39 0 0± 2 0 6 )Ma。它们代表了这些火山岩的形成时代 ,表明本区在古近纪始新世中期发生过大规模的火山活动  相似文献   

广西环江县北山地区喷流沉积铅锌矿资源潜力及找矿方向   总被引：6，自引：2，他引：6  

谢世业  陈大经  辛厚勤  刘川宁 《矿产与地质》2004,18(3):217-219

环江县北山地区铅锌矿均富集在同一地层层位——中上泥盆统，五圩—川山—驯乐NNE向深断裂控制着成矿带，矿床存在大量沉积成岩成矿组构，喷流沉积特征明显。其成矿地质背景、沉积相、礁硅岩套建造、同生断裂活动、赋矿层位等与邻区丹池锡一铅锌多金属矿集区类似，有巨大找矿潜力。  相似文献   

论资源与环境的关系   总被引：4，自引：0，他引：4  

柯海玲  杜佩轩 《陕西地质》2004,22(1):83-87

资源与环境是人类赖以生存和发展的物质基础和条件，作为地球生态的两个方面，二者共同构成矛盾的统一体，相辅相成又相互制约。当与经济联系起来时，便具有确稀缺性和极限性。  相似文献   

自适应空间信息移动服务   总被引：4，自引：0，他引：4  

张海堂罗睿  张永生李波 《测绘学院学报》2004,21(1):34-37,41

空间信息移动服务系统是空间信息系统继由传统PC计算环境向有线Web分布式计算环境扩展后，向移动计算环境的新发展。文中在分析移动计算环境概念和特点的基础上，讨论了空间信息移动服务的若干特点及关键技术，研究了自适应空间信息移动服务方案。  相似文献   

航天GPS接收机设计   总被引：1，自引：0，他引：1  

杨春宝  张海云  邱宗德  尤政 《全球定位系统》2004,29(3):19-25

航天GPS接收机为航天器提供航迹、姿态、时问和相对距离等导航信息，提高航天嚣运行的自主性。文中介绍了清华宇航中。航天GPS接收的硬件和软件设计，给出测试结果和分析。  相似文献   

Wavelet analysis and interpretation of gravity data in Sichuan-Yunnan region, China   总被引：4，自引：0，他引：4  

楼海  王椿镛 《地震学报(英文版)》2005,18(5):552-561

Introduction Sichuan-Yunnan region, located in the east margin of Qinghai-Xizang (Tibetean) Plateau, is a transitional zone between the rapidly upheaving Tibetean Plateau and relatively steady Yangtze Platform. Under the pressure exerted by the northward movement of Indian Plate, Sichuan-Yunnan region has been undergone strong deformation and regmagenesis, becoming one of the regions with the most intensive seismicity in the world. The research on the tectonics and seismicity there is alw…  相似文献   

Sr/Sr and Sr/Ca in speleothems for paleoclimate reconstruction in Central China between 70 and 280 kyr ago     

Hong-Chun Li  Teh-Lung Ku  Hai Cheng  Zhi-Bang Ma  Mung-Dar Li 《Geochimica et cosmochimica acta》2005,69(16):3933-3947

Limestone cave deposits (speleothems) provide archives for past changes in regional climates over a range of timescales. While δ¹⁸O and δ¹³C in speleothem calcite have been commonly used for reconstruction of paleoclimates, we report here further efforts in the use of ⁸⁷Sr/⁸⁶Sr and Sr/Ca signals in speleothem calcite to deduce paleomonsoon variability near the Loess Plateau of central China. A two end-member mass-balance model of concentration and isotopic composition of strontium in a cave system is used to estimate variation of the ⁸⁷Sr/⁸⁶Sr ratio in sediments overlying a limestone cave. We show that this ratio reflects climate-driven variations in the provenance and the extent of chemical weathering of the epikarstic sediments. The measurements of ⁸⁷Sr/⁸⁶Sr made on a well-dated stalagmite, SFL, from Buddha Cave (33^o40N′ 109^o05′E) show ratios of 0.71092 to 0.71133 (±0.00001 as 2σ) during relatively cold periods (e.g., Marine Isotope Stage (MIS) 5b, 5d, and 8), lower than ratios of 0.71133 to 0.71194 during relatively warm periods (e.g., MIS 5a, 5c, 5e, and 7). As changes in the Sr/Ca ratio may affect speleothem ⁸⁷Sr/⁸⁶Sr, we show that the direct use of speleothem ⁸⁷Sr/⁸⁶Sr is less ideal than our modeled ⁸⁷Sr/⁸⁶Sr for the exogenic Sr source above the cave as a paleomonsoon proxy. Using the δ¹⁸O, δ¹³C, Sr/Ca, and ⁸⁷Sr/⁸⁶Sr records of the stalagmite, we reconstruct the variability of the East Asian monsoon for the time period between 70 and 280 kyr ago. The results show that summer monsoons were more intense during interglacial periods than during glacial periods.  相似文献   

The influence of coupled physical swelling and chemical reactions on deformable geomaterials     

Yue Ma  Xiao‐Hui Chen  Lee J. Hosking  Hai‐Sui Yu  Hywel R. Thomas  Simon Norris 《国际地质力学数值与分析法杂志》2021,45(1):64-82

Coupled thermo‐hydro‐mechanical‐chemical modelling has attracted attention in past decades due to many contemporary geotechnical engineering applications (e.g., waste disposal, carbon capture and storage). However, molecular‐scale interactions within geomaterials (e.g., swelling and dissolution/precipitation) have a significant influence on the mechanical behaviour, yet are rarely incorporated into existing Thermal‐Hydro‐Mechanical‐Chemical (THMC) frameworks. This paper presents a new coupled hydro‐mechanical‐chemical constitutive model to bridge molecular‐scale interactions with macro‐physical deformation by combining the swelling and dissolution/precipitation through an extension of the new mixture‐coupling theory. Entropy analysis of the geomaterial system provides dissipation energy, and Helmholtz free energy gives the relationship between solids and fluids. Numerical simulation is used to compare with the selected recognized models, which demonstrates that the swelling and dissolution/precipitation processes may have a significant influence on the mechanical deformation of the geomaterials.  相似文献   

Three‐dimensional shakedown solutions for anisotropic cohesive‐frictional materials under moving surface loads     

Juan Wang  Hai‐Sui Yu 《国际地质力学数值与分析法杂志》2014,38(4):331-348

Previous work on three‐dimensional shakedown analysis of cohesive‐frictional materials under moving surface loads has been entirely for isotropic materials. As a result, the effects of anisotropy, both elastic and plastic, of soil and pavement materials are ignored. This paper will, for the first time, develop three‐dimensional shakedown solutions to allow for the variation of elastic and plastic material properties with direction. Melan's lower‐bound shakedown theorem is used to derive shakedown solutions. In particular, a generalised, anisotropic Mohr–Coulomb yield criterion and cross‐anisotropic elastic stress fields are utilised to develop anisotropic shakedown solutions. It is found that shakedown solutions for anisotropic materials are dominated by Young's modulus ratio for the cases of subsurface failure and by shear modulus ratio for the cases of surface failure. Plastic anisotropy is mainly controlled by material cohesion ratio, the rise of which increases the shakedown limit until a maximum value is reached. The anisotropic shakedown limit varies with frictional coefficient, and the peak value may not occur for the case of normal loading only. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Varying water utilization of Haloxylon ammodendron plantations in a desert‐oasis ecotone          下载免费PDF全文

Hai Zhou  Wenzhi Zhao  Gefei Zhang 《水文研究》2017,31(4):825-835

Haloxylon ammodendron is a desert shrub used extensively in China for restoring degraded dry lands. An understanding of the water source used by H. ammodendron plantations is critical achieving sustainable vegetation restoration. We measured mortality, shoot size, and rooting depth in 5‐, 10‐, 20‐, and 40‐year‐old H. ammodendron plantations. We examined stable isotopic ratios of oxygen (δ¹⁸O) in precipitation, groundwater, and soil water in different soil layers and seasons, and in plant stem water to determine water sources at different shrub ages. We found that water acquisition patterns in H. ammodendron plantations differed with plantation age and season. Thus, the main water source for 5‐year‐old shrubs was shallow soil water. Water sources of 10‐year‐old shrubs shifted depending on the soil water conditions during the season. Although their tap roots could absorb deep soil water, the plantation main water sources were from soil water, and about 50% of water originated from shallow and mid soil. This pattern might occur because main water sources in these plantations were changeable over time. The 20‐ and 40‐year‐old shrubs acquired water mainly from permanent groundwater. We conclude that the main water source of a young H. ammodendron plantation was soil water recharged by precipitation. However, when roots reached sufficient depth, water originated mainly from the deep soil water, especially in the dry season. The deeply rooted 20‐ and 40‐year‐old shrubs have the ability to exploit a deep and reliable water source. To achieve sustainability in these plantations, we recommend a reduction in the initial density of H. ammodendron in the desert‐oasis ecotone to decelerate the consumption of shallow soil water during plantation establishment.  相似文献