大洋岩石圈拆沉与大陆下地壳拆沉：不同的机制及意义——兼评“下地壳＋岩石圈地幔拆沉模式”

拆沉作用(delamination)是地球科学中一个重要的科学问题。本文认为,大洋岩石圈拆沉和大陆下地壳拆沉是不一样的:(1)拆沉的物质不同。大洋岩石圈拆沉的物质包括大洋地壳、岩石圈地幔甚至一部分软流圈地幔,它们共同进入地幔深部;而大陆下地壳拆沉仅仅限制在下地壳,不包括岩石圈地幔。(2)拆沉的动力不同。大洋岩石圈拆沉是由板块俯冲引起的,是地幔对流的产物,因此是一种快速的主动的拆沉;而下地壳拆沉是由于下地壳加厚使下地壳密度增加引起的,还要求其下刚性的岩石圈地幔转变成塑性的软流圈地幔才有可能发生。因此下地壳拆沉要克服许多阻力才能实现,使拆沉成为一个漫长的过程,是慢速的和被动的拆沉。(3)拆沉的过程不同。大洋岩石圈拆沉是由板块俯冲触发的,俯冲导致碰撞,大洋岩石圈从根部断裂,拆沉进入地幔。大陆下地壳拆沉由地壳加厚开始,使下地壳转变为榴辉岩相;随后,岩石圈地幔减薄,直至全部转化为软流圈地幔;下地壳发生部分熔融,形成大规模的(埃达克质)岩浆,使下地壳榴辉岩的密度大于下伏的地幔,从而引发拆沉。大陆下地壳拆沉不大可能是整体进行的,可能是一块一块地被蚕食、被拆沉的。(4)拆沉后的效应不同。大洋岩石圈地幔拆沉,使热的软流圈地幔上涌,从而引发了一系列地质效应:如岩浆活动、地壳抬升、构造松弛以及随后的造山带垮塌等。而下地壳拆沉只引起地壳减薄,高原和山脉垮塌,并不伴有大规模的岩浆活动和地壳抬升等过程。(5)拆沉与岩浆活动的关系不同。主动拆沉导致大规模岩浆活动,而被动拆沉是在大规模岩浆活动的基础上开始的。此外,文中还对"下地壳 岩石圈地幔拆沉"模式提出了质疑,认为该模式有许多难以理解的问题和太多推测的成分,而且与现在保存的地质事实不符。     

关于瑞利散射在九寨沟、黄龙水体颜色形成中作用的讨论

分析了可见光在大气和水体中的瑞利散射效应和吸收、反射效应特征,提出了九寨沟、黄龙水体颜色主要源自水体对可见光的选择性吸收和反射,否定了广泛采用九寨沟、黄龙水体的“瑞利散射成因”说和“元素离子呈色”说。     

一种海面风场反演的快速风矢量搜索算法

本文以SeaWinds散射计为例，从最大似然估计的海面风场反演方法出发，根据其目标函数的一般分布特征，提出并实现了一种快速风矢量搜索算法。然后采用美国SeaWinds散射计的部分LA实测数据对该搜索算法进行了验证，并与常规算法对同一实验数据的反演偏差及运行时间进行了对比分析，结果表明该算法在能够保证反演精度的前提下，在较大程度上提高了运行效率。     

THE TEST OF APPLYING RADAR TREC WIND IN THREE-DIMENSIONAL VARIATIONAL ASSIMILATION

1 INTRODUCTIONThat the radar data are reasonably ingested into theassimilation analysis system to improve the analysisquality and prediction precision is one of the problemsmeteorologists currently try to resolve. Many scholarshave already obtained some r…     

IMPACT OF THE INITIALIZATION ON MESOSCALE MODEL PREDICTION IN SOUTH CHINA

1 INTRODUCTIONThe initial state of the atmosphere is one of the keyfactors that affect the result of NWP. With thedevelopment of increasingly finer NWP, the quality ofinitial atmospheric state has been drawing more andmore attention[1-7]. GRAPES 3D- Var(G…     

DVD技术在气象影视素材库建设中的应用

分析了如何将高品质DVD制作技术应用到省级气象影视素材库建设中的方法,以及充分利用DVD的高画质、多音轨、多字幕等相关制作技术为气象影视工作服务的技巧。     

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介绍了无线电子信息显示屏在气象服务中的应用及当前主流无线电子气象信息发布系统,分析了其市场前景。     

中国云南哀牢山含海蓝宝石伟晶岩的起源和成岩模拟实验研究

The Ailaoshan aquamarine-bearing pegmatites are associated with Proterozoic metamorphic rocks in the southern portion of the Ailaoshan fault-folded complex.The gem-bearing pegmatite mineralization zones of the region occur in areas generally consistent with the regional tectonic trend.The pegmatites are found in metamorphic rocks,migmatites and in the inner/outer contact zones of gneissoid granites. The Rb-Sr isochron drawn for the pegmatites is 26～31 Ma,(i.e.in Himalayan).The homogenization temperatures of melt and liquid inclusions in minerals vary from 185 to 920℃,which are comparable to the inclusions observed in banded migmatites and ptygmatic quartz veins in the surrounding metamorphic rocks. The mineralization fluids of the pegmatite were rich in HCO_3 and CO_2,and their compositional assemblages are comparable to metamorphic fluids.Results of H,O,C,Si etc.isotopic analyses and REE,and Be analyses indicates that the sources of mineralization components that formed the pegmatites are closely associated with metamorphic fluids and the enclosing metamorphic rocks. A pegmatite structure simulation experiment was conducted at high temperature and pressure(840℃and 1,500×105Pa.),with various metamorphic rock samples in a water-rich and volatile-rich environment.When the liquidus was reached,the temperature was gradually decreased at the rate of 5～10℃/day over a time period of three months.SEM energy-dispersive spectrum analyses were performed on the experimental products.A series of pegmatoid textures were observed including zonal texture,megacryst texture,drusy cavities,crystal druses,and vesicular texture along with more than ten types of minerals including plagioclase,microcline,quartz and biotite.Different metamorphic rock melts generated different mineral assemblages.Experiment results revealed that the partial melting of metamorphic rocks could form melts similar to pegmatite magmas. Based upon the geological characteristics,geochemistry,and pegmatite texture simulation experimental results,it is concluded that the mineralization components of Ailaoshan aquamarine-bearing pegmatites came from metamorphic rocks.The petrogenetic model for the origin of pegmatites is related to ultrametamorphism and metamorphic anatexis.     

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昆明机场残积红土既是区域内重要的土地资源,更是各类工程建设的建筑地基,由于机场及临近区域内小江地震活动断裂带和普渡河断裂带地震活动频繁,使研究区处于较不稳定状态。本文采用MIDAS GTS有限元数值分析软件,利用动三轴试验所得出的结果,分别对昆明长水国际机场玄武岩残积红土、砂页岩残积红土地层下典型的地下结构进行了抗震模拟研究。所获得的研究成果,对红土分布区城市及村镇房屋建筑地基和地下空间结构抗震安全稳定性评价具有一定的指导意义和实用价值。     

某住宅楼倾斜原因分析及纠偏方案探讨

分析了某住宅楼倾斜原因,简述了其加固处理过程,并对其纠偏加固方案进行探讨,从而总结了此类工程治理的经验教训。