A mixed finite element method for Hele-Shaw cell equations

A new numerical method to solve the system of equations describing two phase flow in a Hele-Shaw cell is presented. It combines a mixed finite element method, the method of subtraction of the singularity and a front tracking grid in a single computational strategy. This choice of discretization techniques is well motivated by the difficulties present in the system of equations and the physics of the problem. The new method was tested against analytical solutions and also by solving the Saffman–Taylor viscous fingering problem for finite and infinite mobility ratios. In both cases convergence under mesh refinement is achieved for the fingers developed from an initial sinusoidal interface. Finger splitting is observed for low values of the surface tension and high mobility ratio. Different explanations, based in our results, are provided for this phenomenon. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analysis of DNAPL infiltration in a medium with a low-permeable lens

In this paper we study the infiltration of DNAPL in a porous medium containing a single low-permeable lens. Our aim is to determine whether or not DNAPL infiltrates into the lens. A key role is played by the capillary pressure: DNAPL cannot infiltrate into the lens unless the capillary pressure exceeds the entry pressure of the lens. In the model this is reflected by an interface condition, the extended capillary pressure condition. To derive analytical approximations we first consider a steady-state DNAPL plume in a homogeneous medium. This results in an estimate of the DNAPL plume width as a function of depth, and an asymptotic solution for small saturations. Assuming that the extent of the lens is much larger than the width of the unperturbed DNAPL plume in the homogeneous medium, we derive an explicit criterion for DNAPL infiltration into the lens in terms of a critical inflow rate. A numerical algorithm is presented in which the extended capillary pressure condition is incorporated. The numerical and analytical results show good qualitative agreement. This revised version was published online in August 2006 with corrections to the Cover Date.     

黑龙江省东部跃进山群中绿片岩的地球化学特征及地质意义

跃进山群出露位于佳木斯地块和那丹哈达地体之间，是完达山造山带的组成部分。它由大陆斜坡相沉积物、大洋中脊型玄武岩和洋岛型玄武岩组成，其中有镁铁－超镁铁质岩块体。它不是一个地层单位，而是与活动大陆边缘板块俯冲作用有关的蛇绿混杂岩     

安徽省大别山南部宿松杂岩变质作用研究

宿松杂岩的变质作用可分为３个阶段：早期、主期和晚期阶段。主期阶段的矿物组合在云母片岩中为石榴石＋多硅白云母＋石英＋磁铁矿±钠云母±绿帘石／黝帘石；在白云母钠长（二长）片岩和片麻岩中为石榴石＋多硅白云母＋钠长石＋石英＋绿帘石／黝帘石±冻蓝闪石；在石榴石钠长角闪岩中为石榴石＋冻蓝闪石＋钠长石＋黝帘石＋石英±钠云母±金红石／磁铁矿。根据多种地质温压计和变质反应可以推测主期变质条件为：Ｔ＝５２０℃～５８０℃，Ｐ＝１．２～１．４ＧＰａ，地热梯度为１２℃／ｋｍ，相当于高压过渡型。晚期阶段变质条件为：Ｔ＝４６０℃～４８０℃，Ｐ＝０．６～０．７ＧＰａ，为中压绿帘角闪岩相。宿松杂岩的变质条件介于其南部的蓝闪绿片岩相和北部的榴辉岩相之间，三者是扬子板块向华北板块之下俯冲到不同深度的产物。     

利用磷灰石裂变径迹计算隆升速率的一些问题

主要讨论了利用磷灰石理解变径迹年龄－－地形高差法计算隆升速率存在的一些问题，介绍了近年来国外在磷灰石裂变径迹退火方面取得的新进展及其在研究隆升速率问题上的应用，并分析了利用磷灰石裂变径迹研究隆升速率应当注意的问题，强调了加强径迹长度分析的研究。     

On the Limnology of Deep and Saline Lake Burdur in Turkey

Limnological characteristics of Lake Burdur in Lake District in south‐western Turkey are presented. It is a deep, tectonic (estimated max. depth 100 m), athalassic, highly alkaline, and saline lake. A set of physical and chemical variables was monitored, phyto‐ and zooplankton was sampled from surface layer of the lake during 1997. Physico‐chemical variables indicated that the lake is hyposaline and composed of some hydrochemically different water layers formed by groundwater sources located on the bottom of the lake. The phytoplankton composition of Lake Burdur consisted of Cyanophyta, Chlorophyta, Bacillariophyta, Dinophyta, and Chrysophyta. The abundance and number of species of Chlorophyta and Cyanophyta were higher than the other taxa. The zooplankton composition of the Lake consisted of Rhizopoda, Rotifera, and Crustacea. Number of species of Rotifera was higher than the other taxa. The diversities of the phyto‐ and zooplankton were calculated according to the Shannon‐Weaver diversity index. The diversity of each group was found to be low in the lake.     

高速公路沉降计算中e-lg p法修正探讨

利用已有的高速公路土工试验资料，通过大量的非线性有限元计算得出一个与路堤填筑高度及路基土体压缩系数相关的沉降综合修正式，使得单向 e-lgp 法的计算结果修正后能够考虑土体侧向变形。实例验证表明：经此式修正后的沉降值误差较小，不但比规范法更合理，而且与实测值以及有限元法结果很接近，具有一定的工程参考价值和借鉴意义。     

与时俱进,发展中国大地构造学

论述了黄汲清经典著作《中国主要地质构造单位》的深远影响。它是中国大地构造研究的奠基之作和经典著作 ,其基本内容和主要论点已为实践所证实 ,并为国内外地质界所认同。这部著作不仅全面系统地总结了过去 ,而且对一些重大地质问题进行了科学预测 ,为后人指出了研究的方向。它是一部你什么时候读都有味道 ,都会受到新的启发的著作。黄汲清的学术思想是民主的、开放的 ,与时俱进的。在《中国主要地质构造单位》中 ,他运用阿尔冈活动论的思想 ,阐述了中国大地构造的动力演化过程。之后 ,他又吸收了裴伟深断裂的思想 ,深入研究了中国的深断裂。 2 0世纪 70年代 ,他指导他的学生将多旋回思想与板块构造结合 ,在中国大地构造图上首次详细标绘了中国境内的板块缝合带 ,从全球动力学角度 ,将他 1 94 5年提出的亚洲三种构造型式发展为古亚洲、特提斯和滨太平洋三大构造域。黄汲清的研究始终是从东亚地质的实际情况出发 ,他曾多次指出 :中国是全球构造研究中的一块宝地 ,中国人应该为世界地质科学的发展做出贡献     

Crustal Growth by Magmatic Accretion Constrained by Metamorphic P-T Paths and Thermal Models of the Kohistan Arc, NW Himalayas

Magmatic accretion is potentially an important mechanism inthe growth of the continental crust and the formation of granulites.In this study, the thermal evolution of a magmatic arc in responseto magmatic accretion is modeled using numerical solutions ofthe one-dimensional heat conduction equation. The initial andboundary conditions used in the model are constrained by geologicalobservations made in the Kohistan area, NW Himalayas. Takingconsideration of the preferred intrusion locations for basalticmagmas, we consider two plausible modes of magmatic accretion:the first involves the repeated intrusion of basalt at mid-crustaldepths (‘intraplate model’), and the second evaluatesthe simultaneous intrusion of basalt and picrite at mid-crustaldepths and the base of the crust respectively (‘double-platemodel’). The results of the double-plate model accountfor both the inferred metamorphic P–T paths of the Kohistanmafic granulites and the continental geotherm determined frompeak P–T conditions observed for granulite terranes. Thedouble-plate model may be applicable as a key growth processfor the production of thick mafic lower crust in magmatic arcs. KEY WORDS: thermal model; magmatic underplating; P–T path; granulite; lower crust     

Polymetamorphism in the NE Shackleton Range, Antarctica: Constraints from Petrology and U-Pb, Sm-Nd, Rb-Sr TIMS and in situ U-Pb LA-PIMMS Dating

Metapelitic rock samples from the NE Shackleton Range, Antarctica,include garnet with contrasting zonation patterns and two agespectra. Garnet porphyroblasts in K-rich kyanite–sillimanite–staurolite–garnet–muscovite–biotite schistsfrom Lord Nunatak show prograde growth zonation, and give Sm–Ndgarnet, U–Pb monazite and Rb–Sr muscovite ages of518 ± 5, 514 ± 1 and 499 ± 12 Ma, respectively.Geothermobarometry and P–T pseudo-section calculationsin the model system CaO–Na₂O–K₂O– TiO₂–MnO–FeO–MgO–Al₂O₃–SiO₂–H₂Oare consistent with garnet growth during prograde heating from540°C/7 kbar to 650°C/7·5 kbar, and partial resorptionduring a subsequent P–T decrease to <650°C at <6kbar. All data indicate that rocks from Lord Nunatak were affectedby a single orogenic cycle. In contrast, garnet porphyroblastsin K-poor kyanite–sillimanite– staurolite–garnet–cordierite–biotite-schistsfrom Meade Nunatak show two growth stages and diffusion-controlledzonation. Two distinct age groups were obtained. Laser ablationplasma ionization multicollector mass spectrometry in situ analysesof monazite, completely enclosed by a first garnet generation,yield ages of c. 1700 Ma, whereas monazite grains in open garnetfractures and in most matrix domains give c. 500 Ma. Both agegroups are also obtained by U–Pb thermal ionization massspectrometry analyses of matrix monazite and zircon, which fallon a discordia with lower and upper intercepts at 502 ±1 and 1686 ± 2 Ma, respectively. Sm–Nd garnet datingyields an age of 1571 ± 40 Ma and Rb–Sr biotiteanalyses give an age of 504 ± 1 Ma. Integrated geochronologicaland petrological data provide evidence that rocks from MeadeNunatak underwent a polymetamorphic Barrovian-type metamorphism:(1) garnet 1 growth and subsequent diffusive garnet annealingbetween 1700 and 1570 Ma; (2) garnet 2 growth during the RossOrogeny at c. 500 Ma. During the final orogenic event the rocksexperienced peak P–T conditions of about 650°C/7·0kbar and a retrograde stage at c. 575°C/4·0 kbar. KEY WORDS: garnet microtexture; P–T pseudosection; geochronology; polymetamorphism; Shackleton Range; Antarctica