燕山地区冀北坳陷雾迷山组角砾云岩的成因

燕山地区冀北坳陷雾迷山组为一套碳酸盐岩潮坪沉积,区内角砾云岩分布较广泛。角砾云岩以棱角—次棱角状为主,大小相差悬殊,自数厘米至数十厘米不等;角砾岩体与围岩的接触界限十分清楚,呈港湾形。结合区域地质背景、岩石学特征,通过镜下鉴定和微量元素分析,对研究区角砾云岩的成因进行了探讨,研究表明:该区角砾岩是早期形成的白云岩在水体相对较深的潮间带,经构造运动的切割及淡水溶蚀改造,再经充填、沉淀和成岩作用而形成的。     

地表水中总有机碳含量测定的优化研究与应用

利用multi N/C3100型总有机碳/总氮分析仪直接测定环境水样中的总有机碳(total organic carbon,TOC)含量,简便快捷,但是能否完全去除无机碳,这对结果的准确性有一定影响。文章研究了不同吹扫时间对环境水样中TOC测定值的影响,对南京市湖泊水TOC含量进行连续6天测定。结果表明:吹扫时间为4 min时,无机碳去除完全,方法的检出限为0.05 mg/L,准确度及精密度均可满足日常生产需要。总有机碳分析仪直接测定环境水样中的总有机碳含量,简便快捷,灵敏度高,重复性好,准确可靠,适用于环境水样中总有机碳的日常测定。     

地理国情监测水面数据时空一致性优化方法

地理国情监测利用遥感、地理信息等技术,动态获取地表覆盖等多样化的地理要素,经统计、分析、评价和应用,服务于政治、经济、文化、资源、环境等多个领域,为政府提供全面、准确、基础的地理信息情报。针对地理国情监测在全国范围基于多时相遥感影像采集水面信息存在时空不一致性的现状,提出一种基于精细DEM的水面数据时空一致性优化方法。利用栅格图形区域生长算法,采用8邻域算子,对水面种子点进行迭代生长计算,得出基于精细DEM的区域生长结果;通过与地理国情监测水面数据对比分析,实现空间化结果的修正,从而达到时空一致性优化的目的。分析了典型研究区水面数据特征,利用该方法进行了优化处理,结果显示：研究区水面数据空间范围相对于时点监测修正了7.99%,满足了地理国情监测时点一致性需求。研究表明：该方法的应用,能够使得在全国尺度上统计的水面数据反映同一季节或可接受时段内的状况,避免或缩小了由于影像数据源的差异造成的时间和空间上的不一致性带来的误差,满足了地理国情监测时点一致性需求,能够在地理国情监测等地表覆盖水面信息提取、优化中推广应用,为政府有效决策提供客观、准确和基础的水面信息。     

Analysis of Slope Stability and Software Development Based on Single-Grid and Two-Grid Finite Element Methods

Slope stability has been a long-standing problem in geotechnical practice. The difficulty in analyzing slope stability may be attributed to geological complexity and versatile environments, but the limitations of analysis methods should not be ignored. In this work, the conventional limit equilibrium methods and the FE stress-based limit equilibrium methods with special emphasis on their limitations are reviewed, and the advantages of the finite element method with the capability of strength reduction are pointed out and illustrated by using some slope examples. Particularly, a flowchart of decision tree on selecting single-grid or two-grid search scheme is proposed for the shear strength reduction finite element method of slope stability analysis. Based on some slope examples, it is demonstrated that the automatic selection or switch between the single-grid scheme and the two-grid scheme can be remarkably superior to the single mesh scheme from the perspectives of computational cost and software development.     

广西融水县孟公山铅锌矿区地质特征及成矿条件

孟公山铅锌矿位于桂北台隆(九万大山穹褶带)西南缘,属于九万大山―元宝山铜铅锌多金属成矿区。矿体分布于元古界四堡群九小组板岩层间断裂硅化破碎带中,含矿岩浆热液沿板岩夹层发生交代作用形成似层状矿体,矿化受断层、岩性双重控制,并与蚀变强度密切相关;矿床成因类型初步定为热液充填型。     

岩盐用作路基填料的力学性质试验

通过试验,研究了察尔汗岩盐用作路基填料的压实特性、抗压强度以及循环荷载下的变形性状。主要探讨了岩盐试样中细粒含量比例对试样压实特性的影响规律;天然岩盐抗压强度的大小分布,以及岩盐抗压强度与粒径、干密度、含水量的关系;交通循环荷载作用下,岩盐的动应变发展情况等。这些结论对盐湖公路建设具有一定的指导意义。     

Mechanical relation between crustal rheology,effective fault friction,and strike-slip partitioning among the Xiaojiang fault system,southeastern Tibet

The north–south trending Xiaojiang fault system accommodates ～10–12 mm/yr sinistral motions between southeastern Tibet and south China. In the south segment, the fault system composes mainly of four parallel strike-slip faults, namely from west to east, the Luzhijiang fault, the Yimen fault, the Puduhe fault, and the Xiaojiang fault. Geological and Seismological observations have shown that these strike-slip faults are all of active, while the slip rates of the Luzhijiang, the Yimen, and the Puduhe faults are much less than that of the Xiaojiang fault. We use finite element modeling to explore the mechanical relation between crustal rheology, effective fault friction and long-term slip rate partitioning among the four parallel faults. The individual faults are simplified as vertical discontinuities embedded in the crust as geophysical explorations have predicted. A large number of models are tested, associating with variations of the crustal rheolohy and the effective fault friction of individual faults. Result shows that if crust bounding the faults trends to behave like rigid blocks and decoupled mechanically from underlying layer, the modeled result is hard to approximate slip rates of the individual faults. To better fit slip rates of the individual faults, viscous deformation of the lower crust should be included. With a heterogeneously viscous lower-crust model that is built upon thermal structure of the heat flow data, associating with relatively low effective friction of the Xiaojiang fault, the modeled results fit the geological slip rates well, with ～1–1.5 mm/yr for the Luzhijiang, the Yimen and the Puduhe faults, and ～6–6.5 mm/yr for the Xiaojiang fault. Thus, in the southward movement of the Tibetan plateau around the eastern Himalayan syntaxis, slip partitioning among the Xiaojiang fault system should be related to viscous deformation of the lower crust associated with different strength of the individual faults, highlighting that deformation of this fault system is coupled mechanically between the frictional upper crust and the viscous lower crust.     

俯冲板片形貌特征和活动大陆边缘演化体制的关系

当大洋板块向大陆板块下俯冲时,上覆板块的边缘可以以沟—弧—盆体制发育,也可以不发育弧后拉伸盆地．为什么同属上覆板块边缘但可以这二种完全不同的体制演化是现代地球科学研究的一个热点．本文在查阅大量最新文献的基础上认为造成这二种不同演化体制除了与俯冲作用的年代学特征有关外还可能主要与俯冲板片的形貌不同所导致局部地幔对流方式不一有关．由于俯冲的倾角,俯冲达到的最大深度以及俯冲板片在６７０ｋｍ上下地幔过渡带处保存的形态等因素不同,造成仰冲板块边缘之下软流圈对流方式不一．从而,造成弧体近陆一侧是否将发生岩石圈拉伸的动力学过程．     

气候变化国家评估报告(Ⅲ):中国应对气候变化对策的综合评价

Climate change is increasingly becoming the hotspot issue of global attention. On the basis of review of the process responding to climate change of international community, this paper introduces the status of carbon emissions of the world and China, and the technology potential for China to mitigate carbon emissions. At the same time, this paper explores the macro-impacts of China's mitigation of carbon emissions, the equity of global mitigation of climate change, and the impacts of international cooperation in the field of climate change. Furthermore, this paper puts forward the ideas and countermeasures of mitigating climate change in China, indicating that China should positively adapt to the trends of international politics, economy and trade pattern changes and bring the strategies of mitigating climate change into national social and economic development strategy, planning to promote comprehensive, coordinated and sustainable development of national economy and society under the situation of global response to climate change.     

Lower friction of the Xianshuihe–Xiaojiang fault system and its effect on active deformation around the south‐eastern Tibetan margin

We use three‐dimensional mechanical modelling with fault as Coulomb‐type frictional surface to explore the active deformation of the Xianshuihe–Xiaojiang fault system in south‐eastern Tibet. Crustal rheology is simplified as an elastoplastic upper crust and a viscoelastic lower crust. Far‐field GPS velocities and Quaternary fault slip rates are used to constrain the model results. Numerical experiments show that effective fault friction lower than ∼0.1–0.08 leads to a high slip rate that fits well with geological estimates of the slip rate on the fault system. Associating with the modelled fault slip rate, strain in the surrounding crust distributes broadly, and is partitioned into strike–slip and thrust senses. This means that in the Indian‐Eurasia convergence, accommodation of the large fraction of sinistral motion on the fault system is achieved mainly due to its lower fault friction. This in turn affects crustal deformation around the south‐eastern Tibetan margin, resulting in negligible compression across the Longmen Shan.