Evolution of permafrost in China during the last 20 ka

The formation and evolution of permafrost in China during the last 20 ka were reconstructed on the basis of large amount of paleo-permafrost remains and paleo-periglacial evidence, as well as paleo-glacial landforms, paleo-flora and paleofauna records. The results indicate that, during the local Last Glacial Maximum(LLGM) or local Last Permafrost Maximum(LLPMax), the extent of permafrost of China reached 5.3×106-5.4×106 km2, or thrice that of today, but permafrost shrank to only0.80×106-0.85×106 km2, or 50% that of present, during the local Holocene Megathermal Period(LHMP), or the local Last Permafrost Minimum(LLPMin). On the basis of the dating of periglacial remains and their distributive features, the extent of permafrost in China was delineated for the two periods of LLGM(LLPMax) and LHMP(LLPMin), and the evolution of permafrost in China was divided into seven periods as follows:(1) LLGM in Late Pleistocene(ca. 20000 to 13000-10800 a BP)with extensive evidence for the presence of intensive ice-wedge expansion for outlining its LLPMax extent;(2) A period of dramatically changing climate during the early Holocene(10800 to 8500-7000 a BP) when permafrost remained relatively stable but with a general trend of shrinking areal extent;(3) The LHMP in the Mid-Holocene(8500-7000 to 4000-3000 a BP)when permafrost degraded intensively and extensively, and shrank to the LLPMin;(4) Neoglaciation during the late Holocene(4000-3000 to 1000 a BP, when permafrost again expanded;(5) Medieval Warming Period(MWP) in the late Holocene(1000-500 a BP) when permafrost was in a relative decline;(6) Little Ice Age(LIA) in the late Holocene(500-100 a BP), when permafrost relatively expanded, and;(7) Recent warming(during the 20 th century), when permafrost continuously degraded and still is degrading. The paleo-climate, geography and paleopermafrost extents and other features were reconstructed for each of these seven periods.     

层间隔震偏心结构双向地震耦合响应研究

建立双向地震作用下层间隔震双向偏心结构侧扭耦联分析模型;考虑上部结构及下部结构的弹塑性模型,隔震支座采用双向耦合非线性Bouc-wen模型模拟;分析偏心参数对层间隔震双向偏心结构的影响规律;评价双向地震作用下我国抗震规范给出的扭转影响系数静力预测值的准确性。结果表明,双向地震作用下设置中间柔性隔震层可以减小上\,下部结构扭转的耦连效应;下部结构存在双向偏心会对隔震层和下部结构扭转反应带来不利影响;LRB耦合效应对层间隔震地震响应影响较小;当下部结构偏心率较大时现行规范计算扭转系数偏于不安全。     

Subduction-zone peridotites and their records of crust-mantle interaction

Subduction is the core process of plate tectonics. The mantle wedge in subduction-zone systems represents a key tectonic unit, playing a significant role in material cycling and energy exchange between Earth's layers. This study summarizes research progresses in terms of subduction-related peridotite massifs, including supra-subduction zone(SSZ) ophiolites and mantle-wedge-type(MWT) orogenic peridotites. We also provide the relevant key scientific questions that need be solved in the future. The mantle sections of SSZ ophiolites and MWT orogenic peridotites represent the mantle fragments from oceanic and continental lithosphere in subduction zones, respectively. They are essential targets to study the crust-mantle interaction in subduction zones. The nature of this interaction is the complex chemical exchanges between the subducting slab and the mantle wedge under the major control of physical processes. The SSZ ophiolites can record melt/fluid-rock interaction, metamorphism,deformation, concentration of metallogenic elements and material exchange between crust and mantle, during the stages from the generation of oceanic lithosphere at spreading centers to the initiation, development, maturation and ending of oceanic subduction at continental margins. The MWT orogenic peridotites reveal the history of strong metamorphism and deformation during subduction, the multiple melt/fluid metasomatism(including silicatic melts, carbonatitic melts and silicate-bearing C-HO fluids/supercritical fluids), and the complex cycling of crust-mantle materials, during the subduction/collision and exhumation of continental plates. In order to further reveal the crust-mantle interaction using subduction-zone peridotites, it is necessary to utilize high-spatial-resolution and high-precision techniques to constrain the complex chemical metasomatism, metamorphism,deformation at micro scales, and to reveal their connections with spatial-temporal evolution in macro-scale tectonics.     

Modeling the westward transversal current in the southern Yellow Sea entrance: a case study in winter 2007

Ocean Dynamics - The westward transversal current (TC) in the southern Yellow Sea entrance was investigated during winter 2007 using a numerical ocean model. The three-dimensional structures and...     

渤东凹陷东营组烃源岩评价

渤东凹陷是渤海海域下一步油气勘探的重点地区之一。本文通过对渤东凹陷单井烃源岩的有机地球化学分析和与渤中凹陷烃源岩的对比研究,结合渤东凹陷盆地模拟成果,得出以下认识：渤东凹陷南部东营组半深湖深湖相泥岩的有机质丰度高,有机质类型好,有机质演化已处于成熟阶段,因而东营组暗色泥岩具有较高的生烃潜力,是一套良好的烃源岩层。     

On the mechanism of resorption zoning in metamorphic garnet

Abstract An analytical electron microscope study of almandine garnet from a metamorphosed Al–Fe‐rich rock revealed detailed composition profiles and defect microstructures of resorption zoning along fluid‐infiltrated veins and even into the garnet/ilmenite (inclusion) interface. This indicates a limited volume diffusion for the cations in substitution (mainly Ca and Fe) and an interface‐controlled partition for the extension of a composition‐invariant margin. A corrugated interface between the Ca‐rich margin/zone and the almandine garnet core is characterized by dislocation arrays and recovery texture further suggesting a resorption process facilitated by diffusion‐induced recrystallization, diffusion‐induced dislocation migration and diffusion–induced grain boundary migration. Integrated microstructural and chemical studies are essential for understanding the underlying mechanisms of processes such as garnet zoning and its modification. Without this understanding, it will not be possible to reliably use garnet compositions for thermobarometry and other applications that rely on garnet chemical information.     

灰色误差理论在岩矿测试数据处理中的应用

介绍了灰色误差理论,并应用于岩矿测试数据基本处理。结果表明,在误差变化范围小的岩矿化学分析中,测量数据的累加曲线为线性关系,在元素不均匀性分布的岩矿化学分析(例如不均匀性金的测试)和岩石强度试验等分散性大的测试中,测量数据的累加曲线为曲线关系,但灰色标准偏差和传统统计学的标准偏差非常接近。该方法简单易行,具有相当的精度和较强的实用性,对测量数据少或难于寻求统计规律的测量过程尤为实用,是一种新的尝试。     

气候系统模式对于北极海冰模拟分析

利用全球耦合模式对比计划第五阶段(CMIP5)模拟试验的结果,并与观测资料对比分析,评估了CMIP5模式对北极海冰的模拟效果。结果表明:多数模式可以较好地模拟出北极海冰的空间分布以及季节变化特征。1979—2005年北极海冰迅速减少,所有模式均模拟出北极海冰减少的趋势,但减少趋势大小与观测差别较大。在全球变化的背景下,全球地表气温升高1℃,北极海冰的面积减少1.02×106km2,而在模式中减少的北极海冰面积在0.62×106—1.68×106km2之间,说明模式对于北极海冰的模拟仍然存在很多不确定性。     

太湖地区河网水体石油类浓度预测

利用完全混合系统水文动力学模型,对太湖地区河道改造后,由于船型及船流量发生变化而导致的水体石油类浓度的变化进行了预测。通过类比分析得出：预测结果基本符合实际。     

Magnetic minerals in Mid-Pleistocene sediments on the Caiwei Guyot,Northwest Pacific and their response to the Mid-Brunhes climate event

Seamounts are ubiquitous topographic units in global oceans, and their influences on local oceanic circulation have attracted great attention in physical oceanography; however, previous efforts were less made in paleoclimatology and paleoceanography. The Caiwei Guyot in the Magellan Seamounts of the western Pacific is a typical seamount, and in this study, we investigate a well-dated sediment core by magnetic properties to reveal the relationship between deep-sea sedimentary processes and global climate changes. The principal results are as follows: (1) the dominant magnetic minerals in the sediments are low-coercivity magnetite in pseudo-single domain range, probably including a biogenic contribution; (2) the variabilities of magnetic parameters can be clustered into two sections at ～500 ka, and the differences between the two units are evident in amplitudes and means; (3) changes in the grainsize-dependent magnetic parameters can be well correlated to records of global ice volume and atmospheric CO2 in the middle Pleistocene. Based on these results, a close linkage was proposed between deep-sea sedimentary processes in the Caiwei Guyot and global climate changes. This linkage likely involves different roles of biogenic magnetite in the sediments between interglacial and glacial intervals, responding to changes in marine productivity and deep-sea circulation and displaying a major change in the Mid-Brunhes climate event. Therefore, we proposed that the sedimentary archives at the bottom of the Caiwei Guyot record some key signals of global climate changes, providing a unique window to observe interactions between various environmental systems on glacial-interglacial timescales.