电渣重熔过程的数值模拟

以电渣重熔电极、渣池和铸锭为研究对象,建立了电渣重熔体系三维准稳态数学模型.利用商业软件ANSYS得到了电渣重熔过程的电磁场、流场与温度场.计算结果表明,在电极和钢锭内,电流主要集中在外表面,在渣池内主要集中在电极角部;由于电流密度分布不同导致的电磁力和焦耳热及冷却条件共同影响渣池内流场和温度场;随着熔速的增加,熔池深度和两相区最大宽度增加;本工况下,700~800kg/h的熔速将对应一个最短的局部凝固时间.     

GPS监测地壳形变漂移速度的计算

根据动态卡尔曼滤波理论,结合GPS监测地壳形变数据处理的特点,构建了动态卡尔曼滤波计算地壳运动漂移速度的数学模型.结合IGS的GPS连续观测网络部分站点的多期数据,使用精密定位定轨软件GAMIT进行定位计算,获得高精度的站点坐标.将坐标作为具有先验方差信息的准观测值,设置站点漂移速度为未知数,进行卡尔曼滤波漂移速度的估计.计算结果与已有结果的比较表明,卡尔曼滤波漂移速度估计可以达到mm级的精度,可用于GPS监测地壳形变进行漂移速度的估计.     

Study on characteristics of long-term gravity changes at Wuhan station

We consider the characteristics of long-term changes in non-tidal gravity and their implication to the local perturbations in barometric pressure and water storage and to the local vertical crustal movement using the long-term continuous gravity observations from a superconducting gravimeter （SG） at Wuhan station, together with the co-site measurements from a Global Positioning System （GPS） receiver and an absolute gravimeter FG5. The observation results indicate that there are obvious seasonal variations in the long-term gravity changes measured with the SG. About 70 percent of the whole seasonal changes come from the contribution of the local disturbances in air pressure and water storage, while over 95 percent of the annual changes are attributed to the loading effects of these environmental perturbations. Due to the absence of direct measurements of the local water storage, especially those of the underground water, the global assimilating models of land water LaD （Land Dynamics） and GLDAS （Global Land Data Assimilation System） cannot virtually describe the real hydrologic disturbances around the station. The resulting gravity changes, which are simulated theoretically by means of convolution integration of the loading Green＇s functions and water models LaD and GLDAS, show significantly time delay of about 55 days from those measured with the SG. Compared with the measurements of the absolute gravity with the FG5, the long-term drift rate of the SG is determined as about 17.13 nms^-2/a. From the co-site GPS measurements, it is found that the local crust is slowly subsiding at a rate of 3.71±0.16 mm/a, and the related gravity variation is estimated as 13.88±0.22 nms^-2/a. In other words, the ratio of the changes in gravity and altitude related to the local vertical crustal movement is about -37.41 nms^-2/cm. It implies that a considerable mass adjustment may be associated with the local vertical crustal movement, and its dynamic mechanism should be investigated further.     

三维现今地应力场有限元数值计算

研究现今地应力场的分布规律对油气藏的勘探、开发有重要的指导意义.依据Petrel地质模型网格节点数据,建立有限元三维精细几何模型,并对岩体和断层进行不同尺寸的网格剖分.综合利用地球物理测井与岩芯资料,采用VB.net编程求得三维岩石力学参数,根据单元中心坐标分别赋予相应的参数.运用大型有限元软件ANSYS建立了塔里木盆地##2地区三维有限元模型,以测井应力解释剖面为井点应力约束条件,经过多次反演试算得到模型的合理边界条件.与现场资料数据比较发现:数值模拟结果吻合性较好.可为三维现今地应力场的模拟提供数值计算方法.     

川滇地区地壳结构的虚拟地表震源 反射测深法研究

基于中国地震局地质研究所在中国四川西部布设的流动地震观测台阵数据,用近年发展起来的虚拟地表震源反射测深方法研究川滇地区的地壳结构。结果表明,川滇地块、松潘-甘孜地块和杨子地块3个地块虚拟地表震源反射测深的莫霍面深度存在明显差异:1)四川盆地为40 km左右;2)川滇地块为45~50 km;3)松潘-甘孜地块为30~40 km。四川盆地虚拟地表震源反射测深的莫霍面深度与艾里重力均衡模型所预测的结果基本上一致,而川滇地块和松潘-甘孜地块虚拟地表震源反射测深的莫霍面深度明显小于前人得到的接收函数莫霍面深度和艾里重力均衡模型预测的结果。可能与四川盆地地壳结构简单,而川滇地块及松潘-甘孜地块地壳结构复杂有关。同时,结果显示,在鲜水河断裂和安宁河断裂处虚拟地表震源反射测深的莫霍面深度明显变浅,可能与这些深大断裂处地幔物质的上涌有关。研究结果可为认识青藏高原东南缘的构造变形模式提供新的约束。     

蒙古及邻区内源磁场基本特征

利用第11代国际参考地磁场(IGRF)模型和NGDC-EMM-720-V3地壳磁场模型,分析蒙古及邻区垂直分量的主磁场、非偶极子场、长期变化、长期加速度,地壳磁异常在地表及地表以上不同高度分布特征,讨论了地壳磁异常与地质构造的关系.结果显示,蒙古及邻区主磁场各成分的空间变化较小,地壳磁异常呈团状、条带状、弧形状分布,分布形态相对复杂;乌兰乌德、乌兰巴托片区的异常中心位置较为稳定;杭爱山、阿尔泰山呈负磁异常,异常分布与山脉构造走向基本一致.正负磁异常过渡区与山脉和盆地分界基本吻合.     

Effect of scanning speed during PTA remelting treatment on the microstructure and wear resistance of nodular cast iron

The surface of nodular cast iron (NCI) with a ferrite substrate was rapidly remelted and solidified by plasma transferred arc (PTA) to induce a chilled structure with high hardness and favorable wear resistance. The effect of scanning speed on the microstructure, microhardness distribution, and wear properties of PTA-remelted specimens was systematically investigated. Microstructural characterization indicated that the PTA remelting treatment could dissolve most graphite nodules and that the crystallized primary austenite dendrites were transformed into cementite, martensite, an interdendritic network of ledeburite eutectic, and certain residual austenite during rapid solidification. The dimensions of the remelted zone and its dendrites increase with decreased scanning speed. The microhardness of the remelted zone varied in the range of 650 HV_0.2 to 820 HV_0.2, which is approximately 2.3–3.1 times higher than the hardness of the substrate. The wear resistance of NCI was also significantly improved after the PTA remelting treatment.     

Paleoproterozoic reworking of ancient crust in the Cathaysia Block, South China: Evidence from zircon trace elements, U-Pb and Lu-Hf isotopes

A combined study of zircon LA-ICP-MS U-Pb dating, trace elements and Hf isotope was carried out for gneissic granite from the Sanzhishu area in Jingning, SW Zhejiang Province. Nearly all the zircons separated from the granite exhibited oscillatory zoning and high Th/U ratios (>0.1). The REE profile showed a pronounced positive Ce anomaly, negative Eu anomaly and an enrichment of HREE, which are typical characteristics of magmatic zircon. Thirteen concordant or nearly concordant analytical data yielded a weighted mean ²⁰⁷Pb/²⁰⁶Pb age of 1860±13 Ma (MSWD=0.084), representing the formation age of the granite. The magmatic zircons had negative εHf(t) values of −15.6 to −10.0 and two-stage Hf model ages of 3.1 to 3.4 Ga, indicating that the granites were formed by reworking of ancient crust. The major- and trace-element data indicate that the gneissic granites are metaluminous high-K calc-alkaline rocks and exhibit the same geochemical characteristics as aluminous A-type granites, implying the emplacement of the granite in a post-orogenic extensional tectonic setting. We conclude that the Paleoproterozoic crustal reworking event in the Cathaysia Block of South China marked the transition from assembly to break-up of the Columbia supercontinent. Supported by National Natural Science Foundation of China (Grant No. 40873004), Special Funds for National Scientific Research of Commonweal Industries, the Ministry of Land and Resources of China (Grant No. 2008110015), Opening Foundation of State Key Laboratory of Continental Dynamics, Northwest University (Grant No. 06LCD12) and the Project of Land and Resources Bureau of Zhejiang Province (Grant No. 2004005)     

五台山古元古代晚期的动力学背景:王家会花岗岩地球化学的制约

五台山西段王家会古元古代花岗岩侵入体主要由石英二长闪长岩、花岗闪长岩和二长花岗岩组成.岩石地球化学分析表明这些岩石具有亚铝钙碱性特征(A/CNK<1.1),在原始地幔标准化的蜘蛛网图上表现Nb、Ta、Sr、P和Ti的亏损,大离子亲石元素富集.εNd(2.1Ga)在-3.82～-2.80范围,表明王家会古元古代花岗岩最有可能形成于大约2.6Ga五台山大洋岛弧火山岩物质和更老的陆壳物质在<1.2GPa条件下的部分熔融.岩石学和地球化学研究表明王家会花岗岩属于后碰撞花岗岩,结合区域上古元古代地质特征,表明华北克拉通中部带南段古元古代晚期的花岗岩构成了与正常造山过程花岗岩浆演化相反的序列.这个花岗岩演化序列说明古元古代晚期可能发生了从伸展到挤压的构造环境的转换.     

Origin of ore-forming fluid in the Piaotang tungsten deposit in Jiangxi Province: Evidence from helium and argon isotopes

The Piaotang tungsten deposit in Jiangxi Province is one of the most important tungsten deposits in the South China Tungsten Metallogenic Province.In this study,we selected wolframite and chalcopyrite from the main mineralizing stage of the Piaotang tungsten deposit,and analyzed the helium and argon isotopic compositions in fluid inclusions of these minerals.The results show a 3He/4He ratio of 0.17 to 0.86 R/Ra,which fall within the range between continental crust(0.01―0.05 R/Ra) and air-saturated water(1 R...