甘肃北山地区460金矿床植物地球化学异常形成的地学机制

为探讨旱区荒漠植物地球化学异常形成的地学机制,选择甘肃北山地区460金矿床作为研究对象,进行了从基岩(矿)→覆盖层→植物的系统采样和多项目试验研究。结果表明:旱区荒漠覆盖条件下,金矿床地下水和土壤水携带的各种可溶性成分和成矿-伴生元素在外界潜在蒸发力、含水量及其变化梯度和植物吸收蒸腾等驱动力的作用下垂直向上运移;在垂向上,K、Na、Cl、Ca等元素淀积在上部,Au、Ag、Cu、Pb、Zn、As、Sb、Mo等成矿-伴生元素淀积在下部;在横向上,矿体及其上部覆盖层形成的相对氧化酸性环境形成了Au、Ag、Cu、Zn、As、Sb、Mo等元素相对高含量区,两侧基岩及其上部覆盖层形成的相对还原碱性环境形成了K、Na、Cl、Ca、Mg、Mn等元素相对高含量区;生长在矿体上部的植物吸收了较多的Au、Ag、Cu、As、Mo等元素,形成了植物地球化学异常;由于不同根深的植物吸取水分及元素的深度和基质类型不同,所以它们吸收的元素组合及含量也不相同;旱区荒漠覆盖条件下,植物地球化学异常的形成主要与地下水和土壤水将下部成矿-伴生元素搬运到上部植物根系所能达到的部位有关;不同根深的植物产生的地球化学异常元素组合、强度等特征具有一定的差异。

对2004年苏门答腊-安达曼岛地震的测地学机制讨论

采用GPS测地学观测资料,基于NUVEL-1A板块运动模型,分别估计和讨论了INDI板块与Burma微板块之间、AUST板块与Burma/SE EURA板块之间的聚敛率,以及INDI与AUST板块间的相对速率。结果显示,沿苏门答腊-尼科巴群岛和沿安达曼群岛两个阶段的地壳破裂分别与AUST板块和Burma板块间、INDI板块和Burma板块间的聚敛率密切相关,从板块运动学角度提供了解释整个苏门答腊-安达曼群岛地壳破裂带上板块间耦合由南向北递减观测结论的佐证;在NUVEL-1A板块运动模型的背景下,2004年苏门答腊-安达曼岛主震应当为AUST板块相对于Burma/SE EURA板块以近60 mm/a,方向NE 30°～35°的运动所致,而非INDI板块或印-澳(INDI-AUST)板块运动所致;根据2004年苏门答腊-安达曼岛地壳破裂特征并结合其余震的分布,进一步肯定了AUST板块西北边界带的地质位置分布。

印、澳板块边界分布与GPS资料用于对2004年Sumatra-Andaman岛地壳破裂测地学机制的再讨论

基于作者此前对印度尼西亚苏门答腊-安达曼岛地震测地学机制的讨论,进一步根据McClos- key等人应用的INDI板块与AUST板块之间大致呈SW(≈S5)～NE(≈N2)走向的板块边界划分模型,利用GPS站速度资料,估计了沿整个苏门答腊-尼科巴岛地壳破裂带INDI板块与Burma/ SE EURA板块之间的板块聚敛率,并与基于NUVEL-1A模型的INDI、AUST板块边界的分布所估计的AUST板块与Burma/SE EURA板块间聚敛率结果作了比较;根据2004年印尼苏门答腊-安达曼岛地壳破裂特征,对该地壳破裂的测地学机制作了进一步讨论,认为基于NUVEL-1A模型的IN- DI、AUST板块边界分布条件下地壳破裂的测地学机制讨论和2004年主震由AUST板块运动触发的结论可能更符合2004年地壳破裂事件的观测结论。目前的Burma微板块的欧拉旋转参数可能不适合用于对该次地壳破裂事件的测地学估计和机制的讨论;INDI、AUST板块间的相对运动是这两者板块间造山带的主要动力源。

Analysis of seasonal variation of water masses in East China Sea

Seasonal variations of water masses in the East China Sea(ECS) and adjacent areas are investigated, based on historical data of temperature and salinity( T-S). Dynamic and thermodynamic mechanisms that affect seasonal variations of some dominant water masses are discussed, with reference to meteorological data. In the ECS above depth 600 m, there are eight water masses in summer but only five in winter. Among these, Kuroshio Surface Water(KSW), Kuroshio Intermediate Water(KIW), ECS Surface Water(ECSSW), Continental Coastal Water(CCW), and Yellow Sea Surface Water(YSSW) exist throughout the year. Kuroshio Subsurface Water(KSSW), ECS Deep Water(ECSDW), and Yellow Sea Bottom Water(YSBW) are all seasonal water masses, occurring from May through October. The CCW, ECSSW and KSW all have significant seasonal variations, both in their horizontal and vertical extents and their T-S properties. Wind stress, the Kuroshio and its branch currents, and coastal currents are dynamic factors for seasonal variation in spatial extent of the CCW, KSW, and ECSSW, whereas sea surface heat and freshwater fl uxes are thermodynamic factors for seasonal variations of T-S properties and thickness of these water masses. In addition, the CCW is affected by river runoff and ECSSW by the CCW and KSW.

Gastroesophageal reflux disease at the turn of millennium

Gastroesophageal reflux disease (GERD) has been an area of active research in the Asia-Pacific region in the recent years. This article outlines some of the interesting research findings. It comprises three parts. The first part dealt with recent data on the changing epidemiology of GERD in Asia.The second part summarized published studies on the relationship between GERD and Helicobacter pylori, relevant to the Asia-Pacific region. The last part discussed some of the recent advances in the treatment of GERD.

Centroid Depth Versus Hypocentral Depth: Their Distribution and Depth/Mechanism Dependence

The Harvard Global CMT catalogue from 1977 to 1998 is analyzed to investigate the relation between the centroid depth and the hypocentral depth. It is observed that for shallow earthquakes, the hypocentral depth is systematically larger than the centroid depth, while for deep_focus earthquakes there is no statistically significant difference between the distributions of centroid and hypocentral depth. A detailed look at the result reveals that such a systematic difference is mainly from the contribution of thrust and normal earthquakes, while strike_slip earthquakes have no such regularity. It turns out that for shallow thrust and normal earthquakes, seismic rupture tends to initiate from the deeper part.

Mechanism of slope failure in loess terrains during spring thawing

Slope failure in loess terrains of Northern China during spring thawing period is closely related to the freeze-thaw cycling that surface soils inevitably experienced. Field surveys were carried out on natural and artificial slopes in thirteen surveying sites located in the Northern Shaanxi, the center of Loess Plateau, covering five characteristic topographic features including tablelands, ridges, hills, gullies and valleys. Based on the scale that is involved in freeze-thaw cycling, the induced failures can be classified into three main modes, i.e., erosion, peeling and thaw collapse, depending on both high porosity and loose cementation of loess that is easily affected. Model tests on loess slopes with gradients of 53.1°, 45.0° and 33.7° were carried out to reveal the heat transfer, water migration and deformation during slope failure. The surface morphology of slopes was photographed, with flake shaped erosion and cracks noted. For three slope models, time histories for the thermal regime exhibit three obvious cycles of freeze and thaw andthe maximum frost depth develops downwards as freeze-thaw cycling proceeds. Soil water in the unfrozen domain beneath was migrated towards the slope surface, as can be noticed from the considerable change in the unfrozen water content, almost synchronous with the variation of temperature. The displacement in both vertical and horizontal directions varies over time and three obvious cycles can be traced. The residual displacement for each cycle tends to grow and the slopes with higher gradients are more sensitive to potentially sliding during freeze-thaw cycling.

Theoretical analysis on water-inrush mechanism of concealed collapse pillars in floor

In order to study the water-inrush mechanism of concealed collapse pillars from the mechanical view, a mechanical model for water-inrush of collapse pillars has been established based on thick plate theory of elastic mechanics in this paper.By solving this model the deformation of water-resistant rock strata under the action of water pressure and the expression of critical water pressure for collapse pillar waterinrush have been obtained The research results indicate that：the boundary conditions and strength of water-resistant strata play important roles in influencing water-inrush of collapse pillars.The critical water-inrush pressure is determined by both relative thickness and absolute thickness of water-resistant strata.

The Geodynamic Mechanism of the M_S8.0 Wenchuan Earthquake

Located on the east boundary of Qinghai-Xizang （Tibet） Plateau, the Ms8.0 Wenchnan earthquake is the strongest event to hit the active block since the 2001 Kunlun Mountains Pass earthquake. In this study, a simplified source model of the Wenchnan earthquake is constructed based on the deep/shallow tectonic settings and crust/mantle structure features of the Longmenshan thrust fault zone. On the basis of dynamic model abstraction, we construct a system of dynamical equations for the seismogenic process and obtain the analytical expressions of stress and strain in the seismogenic process. A preliminary study of the seismogenic process of the Ms8.0 Wenchuan earthquake, based on the analytical solution of the model and observation of tectonic deformation in the Longmenshan region, indicates that the seismogenic process of the Wenchuan earthquake took place over a period of more than 3200 years. The slow process of seismogeny and the long recurrence period of strong earthquakes are attributed to the low deformation rate of the Longmenshan tectonic zone.

The research on the thermal destruction of environment and controlling techniques of the No.4 outcrops fire in Haibaoqing

The coal fire is one of very serious disasters in natural, not only amount of coal resources was burned and some ecological environment problems such as ground subsidence, acid rain, pollution and vegetation died were caused serious. The No.4 coal seam outcrops fire in Haibaoqing was take as research object, based on the existing theory of mechanism and characteristics of coal outcrop fires, a new fire-fighting composite gel is applicated which fits in with extinguishment of outcrop coal fires well. The technology has many advantages in extinguishing coal fires including isolating the coal from oxygen and lowering the temperature of the high-temperature coal and rock. The structure and chemical composition as well as fires-fighting properties of the composite gel is analyzed profoundly, as a result, reduce and stop the environment destruction caused by the coal fire.

Communicating Geologically-Underpinned Issues： Drivers and Mechanisms

Geologists can offer key insights in regard to several high profile environmental issues that are faced today. At the same time, like scientists in most other disciplines, many geologists are not naturally adept at communicating in an effective manner with non-geologists. This paper firstly identifies the more subtle facets of topical major issues （the drivers） where geologists can contribute important perspectives. Next, the detractions to effective communication are identified, along with the recommended means to overcome them （the mechanisms）. Many topical issues are in fact geologically-underpinned （e.g. obviously, geohazards）, so geologists ought to have something meaningful to say. By the same token, if geologists have difficulty communicating with other scientists, how can they possibly hope to communicate with journalists and with the public at large？ Proper scientific contextualization is an ideal starting point, but this fundamental framing step does not always suit protagonists who have non-scientific agendas. Thus, geologists not only have to convey their science （geology） in an understandable way, but to do so in a truly effective manner must recognize and take into account possible predispositions that their audience may have.

Effects of Microgravity on Human Physiology and Ground-Based Models for Space Physiological Studies

With the development of manned spaceflight, more and more researches are involved in the area of gravitation physiology. When astronauts are exposed to microgravity, a series of special physiological or pathological changes will occur, which will start self-regulation mechanisms to reduce abnormalities and help the organism to better adapt to microgravity. However, these adaptive changes may also induce degradation or damage to physiological functions. This paper summarizes the physiological effects of microgravity on the human body from the aspects of skeletal and mineral metabolism, muscle structure and function, vestibular functions, cardiovascular function and pulmonary function, as well as expounds some commonly used ground-based space analogies. The paper will provide a reference for further study on the physiological effects of microgravity.

Numerical investigation on the geodynamical mechanism of the first major shock of 2006 Pingtung M_w7.0 earthquake

A strong Mw7.0 earthquake struck Pingtung offshore of Talwan on December 26, 2006. It consisted of two major events with an 8-minute interval. The first major shock occurred at 12：26 UTC. Focal mechanism results from Harvard, USGS, and BATS all indicated that the first major shock was a normal fault earthquake and the second one was dominated by strike-slip offsets. The location of the epicenter varied greatly in depth in different analyses. The latest results showed that the focal depth of the first shock was most probably around 40-44 km, placing the epicenter in the lithospheric mantle. However, this is not a location where earthquakes usually occur. To explore the geodynamical mechanism of this event, we carded out 2D finite element method （FEM） numerical experiments. Our primary results indicate that the geodynamical background, as well as the formation of Pingtung earthquake, is a consequence of the collision between Luzon arc and Chinese continental margin. Although Taiwan Island is in the shadow of NW-SE trending compressive collision zone, the existence of ductile lower crust leads to the decoupling between upper crust and lithospheric mantle. As lithospheric mantle subducts to the depth of around 250 km, the upper part of the bending subduction slab puts itself in an extensional state. The extensional stress from bending induced the occurrence of this normal fault earthquake at the critical point.

Emplacement mechanism of Linglong granitoid complex, Shandong Peninsula, China

The Linglong granitoid complex (LGC) is composed of four major plutonic units that intruded and cooled in the Middle Jurassic (170-155 Ma). Gravity-anomaly modeling indicates that the LGC is a sheet-like laccolith, less than 10 km thick, that dips shallowly below the surface toward the Tancheng-Lujiang (Tan-Lu) fault, a major lithospheric structure in Eastern China. Measurements of foliation in the field and measurements of planar and linear magnetic fabrics from the study of anisotropy of magnetic susceptibility in the LGC indicate that foliation is dominantly shallowly dipping and magnetic lineation is mainly parallel to the dip direction of the laccolith toward the Tan-Lu fault zone. The trend of lineations is consistent with flow of magma up the thrust to reach shallower levels. The magma of the LGC probably originated by crustal melting within the Tan-Lu fault zone and the emplacement of magma occurred along a shallowly-dipping thrust that drained the Tan-Lu fault zone, the mechanism of which is mainly dike-fed model.

Interactions between invasive plants and heavy metal stresses:a review

Global changes have altered the distribution pattern of the plant communities,including invasive species.Anthropogenic contamination may reduce native plant resistance to the invasive species.Thus,the focus of the current review is on the contaminant biogeochemical behavior among native plants,invasive species and the soil within the plant-soil ecosystem to improve our understanding of the interactions between invasive plants and environmental stressors.Our studies together with synthesis of the literature showed that(i)the impacts of invasive species on environmental stress were heterogeneous,(ii)the size of the impact was variable and(iii)the influence types were multidirectional even within the same impact type.However,invasive plants showed self-protective mechanisms when exposed to heavy metals(HMs)and provided either positive or negative influence on the bioavailability and toxicity of HMs.On the other hand,HMs may favor plant invasion due to the widespread higher tolerance of invasive plants to HMs together with the‘escape behavior’of native plants when exposed to toxic HM pollution.However,there has been no consensus on whether elemental compositions of invasive plants are different from the natives in the polluted regions.A quantitative research comparing plant,litter and soil contaminant contents between native plants and the invaders in a global context is an indispensable research focus in the future.

Summer circulation structure and formation mechanism in the Beibu Gulf

Due to limited in situ data and diagnostic numerical models, the summer circulation structure and formation mechanism in the Beibu Gulf have always been in controversy in the past 50 years. Therefore, a new three-dimensional hindcast model was built within the northwestern South China Sea(SCS), forced with the daily averaged wind, heat flux, lateral flux, as well as tidal harmonic and eight major rivers discharges. And the east boundary was set up far away off the Qiongzhou Strait(QS). Lastly, the model results were consistent with not only the synchronous observation data from the project 908 but also the historical observed data. As a result, the summer circulation structure was revealed that the southern Gulf was occupied by an anticyclonic eddy whereas the northern Gulf was dominated by a cyclonic gyre. Although the circulation major structure was stable, its area and strength had yearly and monthly oscillation. The other three sensitive experiments indicated that the circulations in the southern and northern Gulf were driven by the SCS circulation and monsoon wind, respectively. After the theoretical analysis of the potential vorticity budget, it was further revealed the circulation in the northern Gulf was driven by the positive wind stress curl in summer. Besides, the river discharge was also significant as the vertical circulation had two layer structures outside the mouth of the Red River. Generally, this work calls for the further research on other subjects, such as ocean biogeochemical or marine fisheries.