Telecommunication interactions between microplates and basal mantle LLSVPs.SCIEI北大核心CSCD

基于海洋地质地球物理观测建立的板块构造理论意味着板块和浅部地幔共同演化,然而地幔底部尤其是大型横波低速异常区(LLSVP)与板块(尤其微板块)运动和演化之间是否存在关联仍有争议。一些研究认为LLSVP长期保持稳定,而另一些模型则认为它与各级板块存在相互作用。为此,本文通过总结前人成果,并基于近期发表的板块重建和地幔对流模型进行进一步分析,探讨微板块运动和LLSVP的演化关系。模拟结果表明,微板块与大板块类似,俯冲后通常会下沉至核幔边界。微幔块会推动地幔底部热的物质聚集并形成大的热化学结构。该热化学结构与层析成像揭示的LLSVP基本吻合。下地幔径向流速场和温度场的二阶结构与地表速度场散度的二阶结构随时间的移动轨迹相似,表明深浅部圈层的耦合演化,但是下地幔结构演化一般会滞后于浅表。在微幔块推挤之下,地幔柱优先沿着地幔底部热化学结构的边缘形成,且有时会被推至热化学结构的内部。地幔柱上升至浅部后,能够导致岩石圈弱化甚至裂解或板块边界跃迁,形成微板块。因此,地幔底部LLSVP不是稳定或静止的,而是与微板块动态协同演化,并通过地幔柱与浅表板块边界发生遥相关,从而控制微板块生成场所。     

Morphotectonics and tectonic processes of the Southwest Indian OceanEI北大核心CSCD

The Southwest Indian mid-ocean ridge (SWIR) is an ultraslow spreading ridge. Based on the submarine bathymetric data, we develop a new division principle on submarine morphotectonics and subdivide the SWIR into the seven-order tectonic geomorphologic units. Taking its submarine morphotectonics in the middle segment and adjacent seafloors of the mid-ocean ridge between Discovery II and Gallieni transform faults as a sample, this paper systematically analyzes its tectonic evolution, segmentation, segmentation and propagation mechanism, the formation of the central rift valley, the ridge-plume interactions, and the ocean ridge jumping. The results showed that the mid-ocean ridges can be divided into four three-order morphotectonics units (i.e., one-order segments of mid-ocean ridge), from west to east, which are separated by the Andrew Bain, the Prince Edwards, the Discovery II, and the Gallieni transform faults, respectively, corresponding to ridge landforms associated with a strongly hotspot-affected ridge, a weakly hotspot-affected ridge, and a normal ultraslow spreading ridge. Each segment can be further subdivided into three or four secondary segments. This paper focuses only on the segmentation and division from fourth-order to seventh-order morphotectonics units between the Discovery II and the Gallieni transform faults (i.e., the fourth-order morphotectonics unit of mid-ocean ridges can be subdivided into other three secondary units). Here the seventh-order morphotectonics unit consists of segments of laterally-aligned rifts (shear zone), en echelon rifts, and other transverse-faulting structures. The mid-ocean ridge segment experienced three oceanic ridge jumping at about 80 Ma, 60 Ma and 40 Ma, respectively, which were affected by the Marion and Crozet hotspots, or the Madagascar Plateau, etc. The oceanic processes of the SWIR are related to the Gondwana breakup, and its tectonic processes has been analyzed in detail as the periodic pull-apart extension, domino-style half-graben, graben subsidence, oceanic core complex, etc. in axial mid-oceanic ridge since 20 Ma. ©, 2015, Science Press. All right reserved.     

Driving forces and management strategies for estuaries in northern China

Estuaries, which lie at the end of rivers, belong to the interlocking area between marine ecosystems and terrestrial ecosystems. In the estuary region, there are plenty of biological resources that carry many important ecosystem services. However, severe degradation of the estuary ecosystem in northern China has been caused by anthropogenic disturbances, including water pollution from upstream area, change of marine environmental dynamics, animal habitat loss, and unreasonable exploitation in the estuary region. In order to provide scientific evidence for restoration and conservation of the estuary ecosystem, we collected data from published literature to analyze the ecological problems in several main estuary regions in northern China, such as the Yellow River estuary, Liaohe River estuary, Haihe River estuary, Yalu River estuary, and some others. The main ecological problems in the estuary region of northern China include the input decrease of fresh water from rivers, the change of the sediment input from rivers, the destruction of the estuary wetland ecosystem, the environmental pollution in the estuary region, the erosion in the estuary region, seawater encroachment, the biodiversity decline of the estuary region, and the depletion of the fish resources in the estuary region. Meanwhile, the driving forces for these ecological problems in the estuary region were also assessed. Based on the analysis of these driving forces, we propose several pieces of advice for integrated estuary management in northern China, including the creation of a management system for estuary conservation, improvement of the means and strength of the environmental law execution, increased investment on scientific research in the estuary ecosystem, improvement of public participation on the conservation for the estuary environment and biodiversity, and construction of a monitoring system for the estuary environment.     

秦岭造山带根部地壳结构及流变学演化

在地质和地球物理资料基础上，运用物理学观点，研究和分析了秦岭造山带根部－大别前寒武纪变质地体的三维结构及流变学演化历史，通过现代及中－新元古代时期地壳流变学剖面的构筑，强调地壳流变学分层性及变质变形分解作用对中下地壳结构及地球动力学演化的控制作用，线状强应变带与透镜状弱应变域的规律组合，是秦岭造山带及其根部地壳结构的基本样式，并具尺度不变性，将古老中下地壳近３Ｇａ的流变学演化历史划分为７个阶段。它     

地球化学负异常及其找矿意义

地球化学负异常的存在具有普遍性。完整的地球化学异常场应包括正异常场和负异常场。负异常按其规模和找矿意义可分为区域、矿床和矿体３个不同层次。区域负异常，可以指明区域找矿方向，圈定找矿靶区；矿床负异常指出矿床可能存在的地段；矿体负异常具体圈定矿体存在的空间位置。负异常与正异常的综合研究，有助于深化对矿床成因的认识，扩大找矿信息，提高找矿效果。     

北京市经济增长与环境污染水平计量模型研究

选取北京市 1985～ 1999年经济与环境数据 ,通过分析经济因子与环境因子相互关系 ,探究北京市经济增长与环境质量演替轨迹 ,以建立北京市经济增长与环境污染水平计量模型 ,为评价北京市环境政策提供依据。实证研究表明 :北京市自 1985年以来随着经济增长其环境恶化程度在下降 ,且已进入经济与环境协调发展后期阶段。北京市各环境指标与人均GDP演替轨迹呈现显著的环境库兹涅茨曲线特征 ,但比发达国家较早实现了其环境库兹涅茨曲线转折点 ,且到达转折点的时间跨度小于发达国家。这主要归功于中国及北京市政府近 10年来 ,尤其 1995年以来有效环境政策和巨额环境投资以及科技后发优势。     

苏锡常地区地裂缝分形的初步研究

利用分形理论对苏锡常地区地裂缝的空间分布特征进行了初步探讨,计算出该区地裂缝的分维值在0987～0996之间。分析认为,该区地裂缝在地质作用过程中自组织程度一致性较强,并具局部与整体的自相似性,这种自相似性,对研究该区地裂缝的进一步发展可能有一定的预测意义     

胶东地区地震烈度衰减关系

使用胶东及邻区地震数据,对于发生在基岩出露区的18次地震的30条可靠等震线,利用最小二乘法,拟合胶东地区地震烈度衰减关系公式。与华北地区地震烈度衰减关系进行比较,发现胶东地区地震烈度衰减较慢。胶东地区地震烈度衰减关系的建立,可以辅助制定相关应急预案和震后快速评估。     

动态古地貌再造: Badlands软件在盆地分析中的应用*

近几年来的研究发现,当存在较强的构造活动时,古地理特征变化将会加快,而常规方法很难对这一构造活动过程中的古地理和古地貌进行有效的恢复和研究。Basin and Landscape Dynamics(Badlands)软件正是基于前人的研究工作而开发的一款数值模拟软件,用于模拟各种空间和时间尺度的地貌演化。它可用于研究地表演化过程、预测侵蚀和沉积速率并评估沉积物通量,从而实现对古地理和古地貌进行更为精细化的研究。笔者介绍了Badlands软件的基本原理和方法,并将此方法应用于东海陆架盆地南部中生代地貌及地质演化过程的研究: 首先利用研究区域内现有的地震剖面、测井、平衡剖面等资料获得中生代早期的古地形;再通过恢复的古地形构建数值模型,并加载降雨量、岩石侵蚀性、海平面变化、动力地形调整和地壳弹性层厚度等相关参数进行模拟研究,以分析强烈的构造运动对盆地地貌演化的影响;最后对比模拟结果与已知的中生代的地貌特征和沉积分布,并据此进一步分析中生代盆地演化过程中的沉积物分布规律以及三维古地理和古地貌演化特征。该方法可以为沉积盆地充填过程分析和能源矿产勘探提供有益的思路。