Study on the characteristics of crust－mantle transition zone in Western Yunnan Province

In this paper the fine structure of crust mantle transition zone in Western Yunnan Province is analysed and discussed based on the reflection phases from Moho discontinuity in Project Western Yunnan 86～87. It shows that in two points: in the north 27.64 km from shot point Jinggu and south 58.74 km from shot point Zhiti, there are transition zones of group of thin layers with inverse velocity.These two reflection points are both situated in the lower velocity anomaly zone in the top of upper mantle. The crust of this region is more seismicity. Maybe the unusual structure of this transition zone is related with the characteristics of this region. This paper discusses the possible geological interpretation model for this transition zone, and also makes suggestion about its application in earthquake prediction.

Ferrite features in simulated transition zone of EH36 shipbuilding steel submerged arc welded by CaF_(2)-SiO_(2)-MnO fluxes

Ferrite features in the simulated transition zone welded with CaF_(2)-SiO_(2)-MnO fluxes containing various MnO contents have been investigated.Confocal laser scanning microscopy has been applied to simulate the thermal cycling of the transition zone and the phase transformations during cooling have been in-situ observed.It has been found that the appearance temperature for ferrite side plate decreases with increasing Mn content in the weld metals caused by MnO content increasing.Meanwhile,growth rates for both ferrite side plate and acicular ferrite are significantly enhanced with a higher Mn content of weld metal.Furthermore,from the statistical fractions of salient microstructures,for all samples,the acicular ferrite,grain boundary ferrite,and polygonal ferrite take over more than 90%.It has also been demonstrated that with the increase in Mn content,the ferrite side plate fraction increases slightly from 5%to 10%and the acicular ferrite fraction shows a tendency of first increasing and then decreasing,which experiences the maximum with the flux containing 30 wt.%MnO.This phenomenon is believed to be controlled by the O and Mn contents in weld metals synergistically.

An experimental study of phase transformations in olivine under pressure and temperature conditions corresponding to the mantle transition zone

High-pressure polymorphs of olivine (wadsleyite and ringwoodite) are major minerals in the mantle transition zone (MTZ).Phase transformations in olivine are important for a series of geodynamic problems such as the mineralogical and evolutionary history of the mantle,mantle convection patterns,and deep focus earthquakes in subduction zones.In this study,we examine phase transformations in olivine with two compositions,namely Mg 2 SiO 4 (Fo 100) and (Mg 0.9 Fe 0.1) 2 SiO 4 (Fo 90),at pressures between 14.1 and 20 GPa and a constant temperature of 1400°C,using the newly installed multi-anvil system at the Laboratory for Studies of the Earth's Deep Interior (SEDI),China University of Geosciences (Wuhan).At 14.1 GPa,Fo 90 transformed completely into the wadsleyite structure (β),while Fo 100 remained as olivine (α).Between 14.8 and 15.6 GPa,both Fo 100 and Fo 90 transformed into the wadsleyite structure.Wadsleyite crystals were identified by two characteristic Raman peaks between 722 and 723 and 917 and 919 cm 1.They exhibit a bimodal grain size distribution:large-crystals with average grain sizes greater than 100 μm and microcrystals less than 10 μm.The population of microcrystals increased with pressure,apparently due to the increase in over-pressure (the difference between the experimental pressure condition and the equilibrium transformation pressure at 1400°C),which promotes nucleation and retards grain growth.All run charges contained large numbers of wadsleyite microcrystals,because of the low activation energy of the nucleation process.The experimentally observed microstructure may shed light on the morphology of wadsleyite observed in shocked meteorites.At 19.5 GPa,wadsleyite coexisted with ringwoodite (γ) in Fo 100,but was absent in Fo 90.At 20 GPa,both samples transformed completely into ringwoodite,which was characterized by the 798 and 840 cm 1 Raman lines.Ringwoodite crystals are euhedral grains (average grain size 10-20 μm),with well-developed triple junctions.The complex upper mantle structure in eastern China determined from seismological studies cannot be explained by the simple transformation sequence of the olivine system alone.Phase transformations in other pyroxene-normative components (including pyroxenes and garnets) and the interaction of these components with olivine may be responsible for the complex structure.High-pressure and high-temperature experimental studies on complex systems (e.g.olivine-pyroxene),combined with data from geophysical exploration,may help in establishing a more realistic geological-petrological model for eastern China and further our understanding of the possible physical mechanisms that are responsible for the complex structure.Such studies will have profound implications for understanding the dynamic processes in the deep Earth interior.

Experimental investigation of phase transformations of olivine and enstatite at the lower part of the mantle transition zone:Implications for structure of the 660 km seismic discontinuity

High-pressure polymorphs of olivine and enstatite are major constituent minerals in the mantle transition zone （MTZ）. The phase transformations of olivine and enstatite at pressure and temperature conditions corresponding to the lower part of the MTZ are import for understanding the nature of the 660 km seismic discontinuity. In this study, we determine phase transfor- mations of olivine （MgSi204） and enstatite （MgSiO3） systematiclly at pressures between 21.3 and 24.4 GPa and at a constant temperature of 1600~C. The most profound discrepancy between olivine and enstatite phase transformation is the occurency of perovskite. In the olivine system, the post-spinel transformation occures at 23.8 GPa, corresponding to a depth of 660 km. In contrast, perovskite appears at 〈23 GPa （640 km） in the enstatite splitting of the 660 km seismic discountinuity under eastern China. system. The -1 GPa gap could explain the uplifting and/orsplitting of the 660 km seismic discountinuity under eastern China.

New hydrous phases in the Al_(2)O_(3)-SiO_(2)-H_(2)O system under the mantle transition zone conditions

Hydrous minerals in the subducting slabs are potential water carriers into the deep mantle,and thus the synthesis of new hydrous phases is significant in our understanding of water circulation throughout the Earth’s interior.In this study,we report the two new hydrous phases,Al_(2)SiO_(6)H_(2)and Al_(5.5)Si_(4)O_(18)H_(3.5)(hereafter referred to simply as phases Psi and Phi,respectively),which are synthesized in the Al_(2)O_(3)-SiO_(2)-H_(2)O system at 15.5 GPa,1400℃and 17.5 GPa,1600℃ by using Sakura2500-ton multi-anvil apparatus.The luminescence spectra of Cr3+show the phase Psi has characteristic peaks at 687,693 and705 nm,while phase Phi has characteristic peaks at 691,696 and 708 nm.Single-crystal X-ray diffraction (SCXRD) refinements yield a monoclinic structure of both phases (space group P2_(1)) with ideal chemical formulae of Al_(2)SiO6H2and Al5.5Si4O18H3.5respectively.The determined lattice parameters for phase Psi are a=9.4168±0.0016Å,b=4.3441±0.0007Å,c=9.4360±0.002Åand β=119.726±0.005°at ambient pressure and 300 K,while the phase Phi has a=7.2549±0.0018Å,b=4.3144±0.001Å,c=8.0520±0.002Å,and β=101.740±0.009°at ambient pressure and 250 K.Electron microprobe analyses (EPMA) show the chemical compositions of phases Psi and Phi to be Al_(1.99)Si_(0.85)O_(6)H_(2.62)and Al_(5.58)Si_(2.81)O_(18)H_(8.03),respectively,which slightly deviate from the ideal formulae inferred from SCXRD measurements.This may result from the disorder or substitution of Al and Si by H in the crystal structures under our synthesis conditions.Our study suggests that phases Psi and Phi are the two potential water carriers at the upper part of the mantle transitions zone,providing new insights into how deep water is stored in this region.

不同气介质-原油热辅助混相实验

利用“界面消失法”开展高温高压可视化PVT(压力-容积-温度)筒实验,研究不同气介质-原油热混相规律。实验表明:恒压升温过程中CO_(2)-原油混相存在两个混相温度域,实验压力为15 MPa时,温度低于140℃,混相带呈液相特征,温度对混相过程起抑制作用;温度高于230℃,混相带趋向气相特征,提高温度有利于形成混相。恒压条件下,温度足够高时,烟道气、N_(2)与原油可以实现混相;温度较低时,CO_(2)促混效果明显,混相温度以N_(2)最高,烟道气居中,CO_(2)最低;温度较高时,CO_(2)促混效果逐渐下降,N_(2)、烟道气与原油混相温度值逐渐接近,混相过程以原油轻组分蒸馏挥发混相为主,相平衡时气相中存在大量轻烃组分,混相带呈气相特征。

包含过渡区的可自动变模数字锁相环

针对传统的数字锁相环频带窄,速度慢,只能锁定中心频率附近频率的缺点,提出了一种具有快捕区、中捕区、过渡区和慢捕区的可变模可监测频率改变的全数字锁相环。该数字锁相环具有自动变模功能,可在锁定过程中自动改变数字滤波器模的值。针对传统数字锁相环在锁定快结束阶段容易进入慢捕区的缺点,在原有的捕捉区域中增加了过渡区,进一步加快了锁定速度。当输入的参考信号频率较高时,环路锁定速度更快。当参考信号在41.67~500 kHz时,系统最快可以在7.64μs内完成锁定。在锁定过程的后阶段,参考信号与输出信号的相位差个数在1~5个系统时钟中均匀分布,相位差系统时钟个数为5、3、2时的锁定速度快于相位差系统时钟个数为4、1。

Experimental study of spinel-garnet phase transition in upper mantle and its significance

Experimental study of spinel-garnet phase transition was carried out using natural mineral and rock specimens from xenolith of mantle rocks in Cenozoic basalt as starting materials. From the result it was found that the condition of spinel lherzolite-garnet lherzolite phase transition ( T = 1100℃ and P = 1.8-2.0 GPa) is consistent with the P-T equilibrium condition of the five-phase assemblage spinel/garnet Iherzolite in eastern China, suggesting that there may exist a spinel-garnet Iherzolite phase transition zone with the thickness of a few km to several ten km at the depth of 55-70 km in the continental upper mantle of eastern China. The depth of phase transition from spinel pyrox-enite to garnet pyroxenite is found to be less than 55 km. Experiment results also show that water promotes metasomatism on one hand but suppresses phase transition on the other. Zoning of mineral composition was also discussed.

变速机械搅拌耦合蒸汽喷吹强化多相流混合特性数值模拟

针对湿法冶金过程中传统线性搅拌工艺导致的多相介质混合不均,混合过程能耗高等问题,提出了变速机械搅拌耦合蒸汽喷吹强化混合工艺,增加了搅拌釜内部的混沌流区域,打破原有的混合隔离区,从而提高搅拌反应釜内部的整体混合效率。通过数值模拟的方法,构建volume of fraction(VOF)多相流模型和Lee蒸汽冷凝相变模型,对多相混合过程进行量化。结果表明,变速机械搅拌耦合蒸汽喷吹条件下搅拌流场合速度提高了38.04%,湍动能强度提升了40.01%。

地幔转换带:地球深部研究的重要方向

地幔转换带是联系上下地幔的纽带,对于认识整个地幔的组成和演化、地幔对流、岩石圈深俯冲及深源地震等地球深部动力学问题具有重要意义。一般认为,转换带地震不连续面主要与橄榄石的高压相变密切相关。最新的高温高压实验研究表明,地幔中非橄榄石组分的相变,如辉石和石榴子石的相变,对不连续面的深度和宽度以及转换带内的波速和密度梯度也起到很大的影响。另外地幔全岩成分、端员组分、温度和水也对相变和不连续面具有重要影响,这些精细的实验研究成果更好地解释了转换带地震不连续面一些相对局部的性质和变化,促进了我们对地球深部性质和动力学过程的了解。因为缺少直接来自地球深部的样品,而地球物理和地球化学研究也有它们的相对局限性,所以高温高压实验仍然是我们了解地球深部成分和性质的重要手段之一。

中国东部及西秦岭地区新生代岩石圈地幔中的相转变带及其温压条件

五相(橄榄石+斜方辉石+单斜辉石+石榴石+尖晶石)共存的地幔橄榄岩捕虏体是来自岩石圈地幔相转变带的直接样品。中国东部及西秦岭地区晚第三至第四纪碱性火山岩携带的少量五相共存的地幔橄榄岩捕虏体为探讨这些地区新生代岩石圈地幔中相转变带提供了宝贵的样品。本文根据地幔橄榄岩捕虏体中石榴石和尖晶石的产出状况,将这些橄榄岩捕虏体分为三类:第一类橄榄岩中尖晶石为粒状残核,尖晶石外缘被石榴石的反应边包围。这种橄榄岩捕虏体代表尖晶石一石榴石相转变带的上限,故称为尖晶石带橄榄岩;第二类橄榄岩中尖晶石和石榴石以单颗粒零散分布为特征,二者共存但未见明显的相转变关系。这类橄榄岩多位于相转变带中部,拟称为尖晶石-石榴石过渡带橄榄岩;第三类橄榄岩中以石榴石为主,尖晶石和辉石等微晶构成石榴石反应边。这类橄榄岩代表尖晶石-石榴石相转变带的下限,故称为石榴石带橄榄岩。因此,根据不同类型橄榄岩捕虏体中矿物的组成,结合温度压力估算即可确定岩石圈地幔中相转变带的深度和厚度。本文通过对中国东部及西秦岭地区晚第三至第四纪碱性火山岩携带的尖晶石-石榴石二辉橄榄岩捕虏体的温度压力估算来进一步厘定中国东部新生代岩石圈地幔中的相转变带深度和厚度。

应用烃类分段捕获原理研究油气运移聚集过程

根据烃类生成、构造活动和圈闭形成的阶段性,以及油气运移聚集存在分段捕获的原理,对川中—川南过渡带安岳—包界地区上三叠统须家河组须二段油气成藏过程进行了研究。结果认为,该区北部的安岳—通贤地区主要捕获了须家河组低演化系列煤成烃类,由于构造运动改变了油气运聚方向,未能进一步捕获后期较高演化阶段的烃类,具有分段捕获的特点;而该区南部的包界地区不仅捕获了低演化阶段的烃类,同时还捕获了成熟—高熟早期须家河组煤成烃类,具有连续累积捕获的特点。

1420铝锂合金回归再回火析出δ′相行为

采用小角 X射线散射技术研究了回归再回火处理 1 42 0铝锂合金 δ′相的形成和粗化 .结果表明 ,再回火 5h析出的 δ′相与基体之间存在过渡区 ,该过渡区经再回火 48h处理后消失 ;之后

地下水饱和区中油—水两相流饱和度的试验研究

本文介绍了在一维砂槽模型中模拟柴油—水两相流在不同粒径玻璃砂多孔介质中运动的试验研究 .研究结果表明 ,柴油—水两相流中 ,残余油饱和度与介质粒径成正比 ,而残余水饱和度与介质粒径成反比 ;由于界面张力的存在 ,油—水界面间存在过渡区 ,对于粒径大于 0 5mm的多孔介质 ,在过渡区上边缘呈现明显的突变界面特征 .研究中尝试对柴油—水两相流动用CCD摄像机摄像 ,并通过图像分析的方法得到了油—水两相流的饱和度分布 ,从而使多相流中饱和度的量化分析成为可能 .

基于车载数据的城市道路交叉口自适应控制研究

在总结现有交叉口交通控制弊端的基础上,通过对控制目标和任务的分析,基于车路协同系统的全时空车载数据,以单车道的车队和多车道的车队簇为控制对象,利用车头时距和间距研究车队和车队簇的形成和动态变化规律,建立了基于车载数据的交叉口自适应控制模型,同时在相位切换逻辑中考虑了两难区.最后基于二次开发的仿真平台,对研究成果进行了测试和验证,相关的案例分析表明,模型应用对于交叉口平峰和低峰情况下的运行效率和安全性有显著改善.

镀锡银钎料扩散过渡区的物相和形成机制

采用温度梯度法对镀锡银钎料进行热扩散处理,形成了扩散过渡区。为了揭示镀锡银钎料扩散过渡区的形成机制和主要物相的形成过程,借助金相显微镜、扫描电镜(SEM)、能谱分析仪(EDS)、X射线衍射分析仪(XRD)对扩散过渡区的显微组织、Sn元素的面扫描分布、物相组成及形貌进行分析。研究表明,Sn元素在镀锡银钎料中分布均匀、无偏析,在扩散过渡区主要以棒状Ag_3Sn相和块状Cu_3Sn相存在。随着热扩散温度升高,Ag_3Sn相和Cu_3Sn相的相对衍射强度逐渐增大。Ag_3Sn相的形成过程分为三个阶段:Ag_3Sn颗粒相弥散分布、Ag_3Sn颗粒相互相接触合并、生成大块棒状化合物相。Cu_3Sn相主要是锡晶须生长冲破镀层的氧化膜,在张应力和压应力协同作用下形成。镀锡银钎料扩散过渡区的形成机制为"钎接、互扩散、亚稳态、合金化"。

相变-扩散钎焊工艺焊接接头缺陷分析

相变 -扩散钎焊是作者提出的一种将相变超塑性扩散焊与扩散钎焊结合起来的新型复合工艺 ,它具有所需温度循环次数少 (与相变超塑性扩散焊相比 )、高温停留时间短但扩散效率高 (与扩散钎焊相比 )、改善热影响区组织 (与弧焊和扩散钎焊相比 )等优点。针对其典型接头的界面接合形貌及缺陷 ,采用扫描电镜及能谱仪进行了分析。结果表明 ,界面接合良好 ,未观察到片状夹杂物、气孔及未焊合。而缺陷具有如下主要特点 :存在于距离界面内部有一定距离的残留中间层内 ,并不在界面上 ;并非夹杂而是孔洞 ;尺寸远小于晶粒尺寸 ;稀疏且错落排列。

NiCrMoV耐热钢汽轮机转子焊缝韧性薄弱区的成因

采用热模拟的方法研究了30Cr2Ni4MoV汽轮机转子用钢多层多道焊焊缝韧性薄弱区的成因.采用光学显微镜、扫描电镜和透射电镜研究了层间局部富碳区域组织对韧性的影响规律.结果表明,焊缝层间局部富碳区域的M-A组元是造成层间韧性薄弱的主要原因之一.M-A组元对韧性的影响与M-A组元的分布、形态、尺寸等因素有关.热模拟二次峰值温度为680℃时,层间回火区M-A组元发生了部分分解;二次峰值温度为820℃时,层间不完全相变区原奥氏体晶界处M-A组元体积增大,晶内M-A组元呈平行的大颗粒链状分布,二次峰值温度为1 050℃时,原奥氏体晶界部分消失,晶内M-A组元部分呈弥散分布.

用数字地震资料探测上地幔深部间断面的研究

对利用数字地震波形资料探测上地幔深部间断面的研究进行了综述，并特别对利用宽频带资料的研究结果进行了介绍。在对８０年代以来的研究状况进行概述的基础上，对目前存在的困难进行了分析。

一种定量地消除波速横向变化影响的三叉震相一维波速结构反演计算方案

通过数值模拟分析,定量讨论震源区附近高速异常、接收区附近低速异常以及目标区浅部局地波速异常对三叉震相反演一维波速结构的影响,结果说明波速横向变化在传统的一维波速结构反演中会产生与异常体相同量级的波速异常假象。提出一种借助区域或全球层析成像结果定量地消除波速横向变化对利用三叉震相走时进行一维波速结构反演影响的解决方案。利用射线追踪法进行的测试计算表明,提出的计算方法能有效地消除波速横向变化对计算结果的影响,使得反演结果更接近于真实结构。