Cenozoic Magmatism and Tectonic Framework of Western Yunnan, China: Constrained from Geochemistry, Sr–Nd–Pb Isotopes and Fission Track Dating     

YANG Xin  XU Xuhui  ZHANG Zhongpei  LIU Yifeng  ZHANG Jibiao  LIU Xingwang  XIONG Ping  ZHENG Jianjing 《《地质学报》英文版》2016,90(5):1679-1698

Western Yunnan is composed of several extruded continental microblocks that were generated by the oblique collision between the Indian and Asian continents during the Cenozoic. In this study, the magmatic and tectonic frameworks of western Yunnan in the Cenozoic were analyzed based on geochemistry, Sr–Nd–Pb isotopes, and apatite/zircon fission track dating. Magmatism during the Cenozoic in western Yunnan was then divided into three distinctive episodes: alkali granite rocks produced from 55 to 46 Ma were derived from the anatexis of crustal materials; bimodal igneous rocks formed between 37 and 24 Ma were possibly derived from an EMII mantle with a contribution from continental materials; and intermediate–basic volcanic rocks produced in the Tengchong microblocks since ~16 Ma are considered to be generated by the partial melting of the upper mantle that was induced by the pulling apart of the dextral Gaoligong strike–slip fault system. Moreover, fission track analysis of apatite and zircon indicates that the regional crustal uplift in western Yunnan possibly began at ~34 Ma, with accelerated annealing occurring at ~24 Ma, ~13 Ma, and ~4 Ma. During the past 24 Ma, the average denudation rate was ~0.32 mm/yr for the faulted block controlled by the Chongshan–Lancang River fault. However, crustal uplift has been relatively gentle in places lacking influence from strike–slip shear zones, with an average denudation rate of ~0.2 mm/yr. Combined with strike–slip shear and block rotation in the Cenozoic, the tectonic evolution of western Yunnan since ~45 Ma can thus be divided into four stages occurring at 45–37 Ma, 37–24 Ma, 24–13 Ma, and 13–0 Ma.  相似文献   

冬季北太平洋风暴轴垂直结构的变化特征及其与我国极端低温事件的关系   总被引：1，自引：0，他引：1  

王超  孙照渤  王娜 《大气科学》2016,40(2):401-410

采用NCEP/NCAR和ERA-40再分析资料,对比分析了冬季垂直尺度上北太平洋风暴轴的时空演变特征,揭示了北太平风暴轴垂直结构具有显著年际变化特征。冬季北太平洋风暴轴垂直结构主要呈现出全区一致、上下反相两种分布型,细分为全区一致增强型、全区一致减弱型、上层增强下层减弱型和上层减弱下层增强型。研究表明:冬季北太平洋风暴轴的垂直结构与我国极端低温事件的关系密切,风暴轴呈全区一致增强(全区一致减弱)型垂直结构时,我国整体区域极端低温频次偏少(多);风暴轴呈上层增强下层减弱(上层减弱下层增强)型垂直结构时,我国东北地区极端低温频次偏多(少),其余地区偏少(多)。  相似文献   

邵武地磁新台建设磁场梯度跟踪测量     

李华  陈俊峰  陈宝根  游永平 《福建地震》2006,(Z1)

根据“地震及前兆数字观测技术规范”电磁部分的要求,在地磁台站建筑施工过程中,需用质子旋进磁力仪在现场对建筑物及周围磁场背景进行监测。本文介绍了邵武地磁新台建设过程中的一次磁场梯度跟踪测量情况。  相似文献   

Impact of sea surface temperature in modulating movement and intensity of tropical cyclones     

M. Mandal  U. C. Mohanty  P. Sinha  M. M. Ali 《Natural Hazards》2007,41(3):413-427

It is well recognized that sea surface temperature (SST) plays a dominant role in the formation and intensification of tropical cyclones. A number of observational/empirical studies were conducted at different basins to investigate the influence of SST on the intensification of tropical cyclones and in turn, modification in SST by the cyclone itself. Although a few modeling studies confirmed the sensitivity of model simulation/forecast to SST, it is not well quantified, particularly for Bay of Bengal cyclones. The present study is designed to quantify the sensitivity of SST on mesoscale simulation of an explosively deepening storm over the Bay of Bengal, i.e., Orissa super cyclone (1999). Three numerical experiments are conducted with climatological SST, NCEP (National Center for Environmental Prediction) skin temperature as SST, and observed SST (satellite derived) toward 5-day simulation of the storm using mesoscale model MM5. At model initial state, NCEP skin temperature and observed SST over the Bay of Bengal are 1–2°C warmer than climatological SST, but cooler by nearly 1°C along the coastline. Observed SST shows a number of warm patches in the Bay of Bengal compared with NCEP skin temperature. The simulation results indicate that the sea surface temperature has a significant impact on model-simulated track and intensity of the cyclonic storm. The track and intensity of the storm is better simulated with the use of satellite-observed SST.  相似文献   

Consolidation and Break-up of the South American Platform in Southeastern Brazil: Tectonothermal and Denudation Histories   总被引：1，自引：0，他引：1  

P.C. Hackspacher  L.F.B. Ribeiro  M.C.S. Ribeiro  A.H. Fetter  J.C. Hadler Neto  C.E.S. Tello  E.L. Dantas 《Gondwana Research》2004,7(1):91-101

The different tectonic stages that occurred at the end of the Proterozoic and during the Phanerozoic have an important bearing on the tectonothermal history of the South American Platform and its consolidation. Geochronological data (U/Pb monazite, ⁴⁰Ar/³⁹Ar whole rock) and apatite fission-track analysis, from Precambrian rocks of the southeastern Brazilian coastline, permit the modeling of a long-term thermal history of the crust and constrain variable denudation rates.Using these data, a temperature-time diagram reflects a period of accelerated exhumation during the end of the Brasiliano Orogeny, followed by long stability and reactivation of the platform during the Rifting Phase of the South Atlantic Ocean.U/Pb zircon and monazite (blocking temperature of ca. 650° C) data from a series of igneous bodies suggest that a tangential and transpressional tectonic regime occurred between 625 and 610 Ma. During the following escape tectonics, between 610 and 590 Ma the exhumation process indicates cooling rates of ca. 12°C/Ma. ⁴⁰Ar/³⁹Ar biotite ages between 540 and 510 Ma (ca. 300°C) and a corrected fission-track age on apatites (100°C) of 480 Ma indicate an exhumation event related to block tectonics with huge vertical displacement along shear zones.A long stabilization phase, with low exhumation, and cooling rate around 0.25°C/Ma was recorded from the Cambro/Ordovician to the Mesozoic. At 65 Ma an acceleration of the exhumation through denudation and reworking of the South American surface with cooling rate of 1.5°C/Ma is observed.The uplift of the Mantiqueira and Serra do Mar mountain ranges along the southeast Brazilian coastline works as a climatic barrier provoking lateral erosional processes causing long-term scarp retreat, combined with intense, but progressive denudation towards the continent. A denudation of 2.5 to 4 km was calculated for such processes. This lateral retreat of escarpments and flexural response can provide important insights regarding marginal isostatic uplift and the evolution of offshore sedimentary basins of southeast Brazil.  相似文献   

涡旋强度调整半径对2016年第18号热带气旋路径预报的影响     

麻素红 《气象学报》2019,77(4):662-673

2016年中国国家气象中心区域台风模式（GRAPES_TYM）对第18号热带气旋（记为TC 1618）的路径预报出现了较大的误差:其平均路径误差显著大于全年的平均误差。分析了涡旋初始化方案（包括涡旋重定位以及涡旋强度调整）对其路径预报的影响。结果显示,涡旋强度调整是造成TC1618预报路径平均误差偏大的主要原因。不同的强度调整半径（r₀=12°,9°,6°,3°）对TC1618路径影响的敏感性试验结果显示,强度调整半径越大,其平均路径预报误差越大。500 hPa副热带高压以及平均海平面涡旋尺度分析发现:较大的强度调整半径（r₀=12°,9°）其初始时刻的涡旋尺度较大,涡旋北侧邻近区域副热带高压等值线相对偏北,副热带高压相对偏弱。尺度大的涡旋其北移速度较大,并且在积分过程中其环流邻近区域副热带高压进一步减弱,导致涡旋环流会更早与其西北侧东移的西风槽结合,移速偏快。   相似文献   

SQL Server数据库中数据的安全监控     

张晖  李雅静  赵颖 《震灾防御技术》2012,7(2):208-213

本文主要阐述了作者在工中遇到的SQL Server数据库中一些重要数据泄漏或是异常变动现象,随后通过各种技术手段追踪数据异常变更的根源的学习研究过程.从而达到了对日常工作中的重要数据进行安全监控、跟踪相关操作的目的,同时,也为各类数据的安全性、准确性提供了坚实的保障.  相似文献   

青藏高原高空流型对西太平洋台风路径影响的诊断分析   总被引：8，自引：0，他引：8  

徐晶  陈联寿 《应用气象学报》1999,10(4):410-420

利用观测研究,动力诊断分析等手段,从上下游效应、中低纬相互作用的角度来探讨青藏高原高空天气系统的变化与西太平洋台风运动两者之间的关系。1970~1995年25年间的统计结果表明,青藏高原高空流型与台风路径有如下关系:高原高空500 hPa为低值系统控制时,有利于台风西行;反之,高原高空500 hPa为高压时,近海台风往往转向。动力诊断分析的结果揭示了高原上空系统影响下游系统的物理机制,即高原上游扰动动能的传递使得下游的槽发展,并进一步影响台风的引导气流。高原脊的存在,使得涡动动能的输送通道偏北;高原上为槽时,涡动动能的输送通道偏南。高原槽前的南风和台风东侧南风将低纬度的低位涡输入副热带高压,有利于副热带高压的发展,影响台风运动,体现了中低纬相互作用对天气系统的影响。  相似文献   

台风“风神”路径、强度及引发江西降水诊断分析   总被引：2，自引：2，他引：0  

朱星球  应冬梅 《气象与减灾研究》2008,31(3):22-27

利用NCEP 1°×1°再分析资料、T213分析资料和常规观测资料,从水汽条件、热力条件、动力条件等方面,对2008年第6号台风“风神”路径、强度变化的原因,及其对江西的影响进行分析。结果表明,台风路径与副高的强度和位置变化密切相关,台风移动方向与风场结构中强风速的风向一致。台风在海上强度减弱主要与水汽来源不足有关,登陆后还与冷空气侵入暖中心有关。由于强度减弱且西南季风不强,造成水汽来源不足,从而导致“风神”没有给江西造成大范围暴雨天气。其中的局地强降水天气发生在台风环流高能梯度锋区,这主要是由于干侵入引发对流性不稳定造成的。  相似文献   

Erosion of Access Tracks in Kalamunda National Park,Western Australia: Causes and management implications     

Paul Gager  Arthur Conacher 《The Australian geographer》2001,32(3):343-357

Construction of access tracks in national parks and other reserves in the south-west of Western Australia is an essential feature of park management. However, their construction was often carried out with little or no appreciation of soil and slope characteristics and potential erodibility, or the effect of slope and stream sedimentation on terrestrial and aquatic flora and fauna. This paper reports on the findings of a study carried out in Kalamunda National Park, a small reserve in the Darling Ranges east of Perth. Tracks were surveyed and the extent of erosion and sedimentation measured. Erosion-indicating and erosion-influencing variables were measured. Track alignment angle (to the contour) and track gradient were the two site variables most significantly correlated with measures of erosion severity. The most important upslope (on-track) factor was track length, and the most important upslope (off-track) factor was the abundance of granite outcrops. Seasonal conditions were important, particularly in relation to soils with relatively high clay contents. When wet, these soils were more likely to suffer from surface drainage problems and increased runoff, associated with decreased cohesion. On the other hand, the more common sand-textured soils are generally more erodible when wet. Several management measures are recommended. These fall into three categories: those relating to track closure or realignment (to avoid the most erosion-susceptible sites); those relating to actual track design and maintenance, or site management; and those relating to modification of visitor behaviour .  相似文献