河北中关矽卡岩铁矿床钴元素分布规律与沉淀机制研究及意义

河北中关铁矿是“邯邢式”矽卡岩铁矿的代表矿床,本文将中关铁矿床成矿过程划分为5个阶段：干矽卡岩阶段、湿矽卡岩阶段、氧化物阶段、铁铜硫化物阶段和铅锌硫化物阶段。对湿矽卡岩阶段、氧化物阶段和铁铜硫化物阶段的金属矿物（包括黄铁矿、磁铁矿、赤铁矿等）开展电子探针测试,并且对这三个成矿阶段的代表性磁铁矿进行LA-ICP-MS微量元素测试,旨在查明中关铁矿床中Co的赋存状态以及在矿床不同成矿阶段的分布规律,探讨Co元素迁移演化-沉淀机制。研究结果表明,Co主要以类质同象的形式存在于黄铁矿中。不同成矿阶段的Co元素分布不均匀,氧化物阶段黄铁矿和磁铁矿中的Co含量最高,分别为0.12%~1.39%、41×10-6~76×10-6;铁铜硫化物阶段黄铁矿大量出现,且Co含量相对较高,为BDL~0.45%,同时期条带状磁铁矿为32×10-6~71×10-6,故此阶段为Co元素最主要的富集阶段。湿矽卡岩阶段为较高温、弱氧化条件,氧化物阶段温度逐渐降低,氧逸度增加,Co可能主要以CoCl42?形式络合迁移;铁铜硫化物阶段温度进一步降低,但还原性增加,Co可能主要以CoCl42?和Co(HS)+形式络合迁移。温度降低以及氧化还原条件的变化可能是控制Co沉淀的重要因素。     

深反射地震成像揭示的班公湖 怒江缝合带中段Moho断阶及其大地构造意义

揭示班公湖- 怒江(班怒)缝合带Moho(莫霍面)结构对于认识中特提斯洋壳俯冲和南羌塘坳陷成因具有重要地球动力学意义。基于横跨班怒缝合带的深反射地震数据(88°30′E),本文采用了中长波长静校正、噪声压制、优化叠加和叠前深度偏移(PSDM)等地震处理技术,获得了深度域地震反射偏移剖面、层速度场和高分辨率Moho结构。由深度域剖面显示,班怒缝合带Moho位于地表以下65～80 km,呈不连续北向抬升趋势,指示在拉萨地块与南羌塘地块之间存在岩石圈上地幔断阶,最大阶步可达15 km。综合分析缝合带两侧的Moho形态认为,这些断阶受南侧拉萨地体的岩石圈上地幔以19. 5°北倾俯冲与北侧南羌塘地块的上地壳抬升驱动,可能与深部存在局部熔融相关。班怒缝合带下的Moho结构表明,随着晚侏罗世—早白垩世中特提斯洋闭合,南羌塘地体由边缘海沉积向前陆盆地转换,形成南羌塘坳陷。     

莺歌海盆地超压体系的成因及与油气的关系

莺歌海盆地独特的地质进程形成多套泥源层,泥源岩的压实与排液不均衡导致盆地内存在大规模的超压体系,大量的生烃及水热增压使盆地内超压进一步加剧。底辟作用将超压传递至浅层,使超压体系的分布在不同深度和不同构造带中的差异均较大。在中央底辟带,由于泥-流体底辟活动极强,突破的地层多,超压顶面埋深很浅;超压的释放不仅仅是孔隙流体的逸散,更重要的是烃源(主要是泥源层)所生成的油和气作为热流体的一部分,伴随热流体向上突破、运移到浅部分异、逸散和聚集形成气藏。     

3. Solar System Formation and Early Evolution: the First 100 Million Years

The solar system, as we know it today, is about 4.5 billion years old. It is widely believed that it was essentially completed 100 million years after the formation of the Sun, which itself took less than 1 million years, although the exact chronology remains highly uncertain. For instance: which, of the giant planets or the terrestrial planets, formed first, and how? How did they acquire their mass? What was the early evolution of the “primitive solar nebula” (solar nebula for short)? What is its relation with the circumstellar disks that are ubiquitous around young low-mass stars today? Is it possible to define a “time zero” (t ₀), the epoch of the formation of the solar system? Is the solar system exceptional or common? This astronomical chapter focuses on the early stages, which determine in large part the subsequent evolution of the proto-solar system. This evolution is logarithmic, being very fast initially, then gradually slowing down. The chapter is thus divided in three parts: (1) The first million years: the stellar era. The dominant phase is the formation of the Sun in a stellar cluster, via accretion of material from a circumstellar disk, itself fed by a progressively vanishing circumstellar envelope. (2) The first 10 million years: the disk era. The dominant phase is the evolution and progressive disappearance of circumstellar disks around evolved young stars; planets will start to form at this stage. Important constraints on the solar nebula and on planet formation are drawn from the most primitive objects in the solar system, i.e., meteorites. (3) The first 100 million years: the “telluric” era. This phase is dominated by terrestrial (rocky) planet formation and differentiation, and the appearance of oceans and atmospheres.     

P-SV反射转换波的倾角时差校正（DMO）方法研究

倾角时差校正（ＤＭＯ）方法对于复杂地质构造条件下的纵波反射波（Ｐ－Ｐ）的多次覆盖地震数据的叠加具有显著的提高信噪比的效果．对于转换反射波（Ｐ－ＳＶ）来说,进行倾角时差校正（ＤＭＯ）处理就更需要．本文首先对Ｐ－ＳＶ波的倾角时差校正（ＤＭＯ）的几何原理进行了分析,然后重点研究用波动方程进行ＤＭＯ的方法,即Ｐ－ＳＶ转换反射波的叠前部分偏移的波动方程法．这种方法也适用于Ｐ－Ｐ反射波的叠前部分偏移处理．研究结果表明,波动方程ＤＭＯ方法在振幅保真方面比几何原理的ＤＭＯ方法有显著改善．     

三维高阶深度偏移方程及其数值求解方法

从三维非均匀介质中的波动方程出发,利用拟微分算子理论,Ｐａｄｅ逼近方法及因式分解技巧,获得了非均匀介质的三维高阶深度偏移方程,相应地提出了逐次低阶方程方法、低阶方程组方法及分裂方法等３种求解方法．与二维情形不同,以上每一种方法在数值求解时均存在由测线坐标ｙ的出现而带来的困难．为了克服这一困难,我们提出了差分算子分解方法,避免了近年来人们竞相研究的ｘ－ｙ方向微分算子分裂带来的分裂误差,保持了应有的相容性,解决了这一令人烦恼的问题．     

Groundwater monitoring strategies for variable contaminant migration boundaries

Abstract

Detection efficiencies of alternative groundwater monitoring networks were evaluated in relation to distance to a buffer zone (contaminant migration) boundary. This boundary establishes a distance limit within which contaminant plumes should pass through monitoring wells, located on curvilinear segments (monitoring loci) near a waste storage facility. Alternative strategies allocated monitoring wells to loci at specified distances, measured parallel to groundwater flow, from the downgradient boundaries of a landfill. One approach constrained wells to equal spacing, measured perpendicular to groundwater flow. Compressing well locations 10% closer to the downgradient corner of the landfill rendered alternative monitoring configurations. Computations by a monitoring efficiency model indicated: (a) networks largely maintained detection efficiency for different contaminant migration boundaries; (b) one network most efficiently attained a target detection capability for all contaminant migration boundaries; and (c) compressed networks slightly outperformed equal-spaced counterparts. Compressed networks with more wells along closer monitoring loci best maintained the detection efficiency when shifting the contaminant migration boundary closer to the landfill. Procedures described in this paper may be useful for examining trade-offs between monitoring efficiency and distance limits of contaminant travel at landfills posing potential hazards to underlying groundwater.     

共接收点倾斜叠加波动方程偏移

共接收点倾斜叠加波动方程偏移,本质上是一种叠前偏移方法.每给定一个斜率P,对经过叠前（动校正前）常规处理的地震记录中的各共接收点道集,沿直线t=τ+px进行倾斜叠加,就形成一个共接收点倾斜叠加剖面.对之进行波动方程偏移,该偏移剖面将代表地下真实构造.对一系列的p,我们可以得到一系列这样的偏移剖面.对它们作共接收点叠加,偏移叠加剖面的信噪比将超过水平叠加剖面.本文导出了在均匀、水平层状及非均匀介质条件下的共接收点倾斜叠加波动方程偏移算法.     

Epicenter and magnitude of large earthquake determined from high-rate GPS observations: A case study of the 2008 M8.0 Wenchuan earthquake

For earthquake and tsunami early warning and emergency response,the earthquake epicenter and magnitude should be determined rapidly and correctly.Using high-rate GPS observations,we can readily obtain precise and high resolution displacement time series and the seismic waveforms during the earthquake.In this paper,a new algorithm is proposed for estimating the earthquake epicenter and magnitude with the seismic waveforms derived from high-rate GPS data during the earthquake.A case study of the 2008 Wenchuan earthquake is conducted from 1 Hz GPS data and the epicenter and magnitude are determined.Compared with the results issued by the China Seismological Bureau,the estimation error of the epicenter and the magnitude is about 12 km and 0.1 magnitude unit,respectively.It has shown that high-rate GPS could be a new tool feasible for estimating the earthquake epicenter and magnitude,independent of or combined with seismometers.     

Spatial-temporal patterns of China’s interprovincial migration, 1985-2010

Migration plays an increasing role in China's economy since mobility rose and economic restructuring has proceeded during the last three decades. Given the background of most studies focusing on migration in a particular period, there is a critical need to analyze the spatial-temporal patterns of migration. Using bicomponent trend mapping technique and interprovincial migration data during the periods 1985-1990, 1990-1995, 1995-2000, 2000-2005, and 2005-2010 we analyze net-, in-, out-migration intensity, and their changes over time in this study. Strong spatial variations in migration intensity were found in China's interprovincial migration, and substantial increase in migration intensity was also detected in eastern China during 1985-2010. Eight key destinations are mostly located within the three rapidly growing economic zones of eastern China (Pearl River Delta, Yangtze River Delta and Beijing-Tianjin-Hebei Metropolitan Region), and they are classified into three types: mature, emerging, and fluctuant origins, while most key origins are relatively undeveloped central and western provinces, which are exactly in accordance with China's economic development patterns. The results of bicomponent trend mapping indicate that, in a sense, the migration in the south was more active than the north over the last three decades. The result shows the new changing features of spatial-temporal patterns of China's interprovincial migration that Fan and Chen did not find out in their research. A series of social-economic changes including rural transformation, balanced regional development, and labor market changes should be paid more attention to explore China's future interprovincial migration.