西藏普兰地区拉昂错蛇绿岩中辉绿岩的锆石SHRIMP U—Pb年龄及其地质意义     

李建峰  ;夏斌  ;刘立文  ;徐力峰  ;何观生  ;王洪  ;张玉泉  ;杨之青 《中国区域地质》2008,(10):1739-1743

蛇绿岩中的辉绿岩岩墙是洋脊扩张的产物．其形成年龄代表了扩张事件的时间,也代表了蛇绿岩的形成时代？对雅鲁藏布江缝合带西段拉昂错蛇绿岩中的辉绿岩岩墙进行锆石SHRIMPU—Pb定年,得出加权平均年龄为120．2Ma±2．3Ma,代表辉绿岩的结晶年龄。结合已有的关于雅鲁藏布江蛇绿岩的形成年龄（西段休古嘎布122．3Ma±2．4Ma,中段大竹卡126．0Ma±1．5Ma、吉定123．0Ma＋_1．8Ma,东段罗布莎162．9Ma±2．8Ma）的报道,表明拉昂错地区特提斯洋海底扩张的时代与体古嘎布地区一致．雅鲁藏布江西段与中段地区洋盆的形成时代一致,但晚于东段的发育时代。这意味着整个东提斯洋盆的发育时代存在东早西晚的特点。  相似文献   

Characteristics of dry-wet abrupt alternation events in the middle and lower reaches of the Yangtze River Basin and the relationship with ENSO   总被引：1，自引：0，他引：1  

Lijie Shan  Liping Zhang  Jiyun Song  Yanjun Zhang  Dunxian She  Jun Xia 《地理学报(英文版)》2018,28(8):1039-1058

During recent decades, more frequent flood-drought alternations have been seen in China as a result of global climate change and intensive human activities, which have significant implications on water and food security. To better identify the characteristics of flood-drought alternations, we proposed a modified dry-wet abrupt alternation index (DWAAI) and applied the new method in the middle and lower reaches of the Yangtze River Basin (YRB-ML) to analyze the long-term spatio-temporal characteristics of dry-wet abrupt alternation (DWAA) events based on the daily precipitation observations at 75 rainfall stations in summer from 1960 to 2015. We found that the DWAA events have been spreading in the study area with higher frequency and intensity since 1960. In particular, the DWAA events mainly occurred in May and June in the northwest of the YRB-ML, including Hanjiang River Basin, the middle reaches of the YRB, north of Dongting Lake and northwest of Poyang Lake. In addition, we also analyzed the impact of El Niño Southern Oscillation (ENSO) on DWAA events in the YRB-ML. The results showed that around 41.04% of DWAA events occurred during the declining stages of La Niña or within the subsequent 8 months after La Niña, which implies that La Niña events could be predictive signals of DWAA events. Besides, significant negative correlations have been found between the modified DWAAI values of all the rainfall stations and the sea surface temperature anomalies in the Nino3.4 region within the 6 months prior to the DWAA events, particularly for the Poyang Lake watershed and the middle reaches of the YRB. This study has significant implications on the flood and drought control and water resources management in the YRB-ML under the challenge of future climate change.  相似文献   

干旱区绿洲土壤共存重金属元素形态变化及生物有效性实验分析——以Cd、Zn、Ni元素为例   总被引：3，自引：0，他引：3  

赵转军  南忠仁  王胜利  刘晓文  陶燕 《地球科学进展》2008,23(11):1194-1200

采用盆栽试验,初步研究了干旱区绿洲土壤—胡萝卜系统中镉、锌、镍3种重金属的形态变化特征及其生物有效性问题。结果表明:供试绿洲土壤原状土中,Cd、Zn、Ni均以稳定的残渣态形式存在,而处理土壤中重金属被钝化的量有限,Cd的存在形式主要以碳酸盐态为主,Zn、Ni则主要以铁锰氧化态为主;3种元素的活性大小依次为Cd>Ni>Zn。根据回归分析,元素Zn对胡萝卜块茎和茎叶吸收Zn量贡献最大的分别是Zn的碳酸盐结合态和铁锰氧化态;元素Ni对胡萝卜各部位吸收贡献最大的均为Ni的铁锰氧化态。  相似文献   

锶掺杂的正铌酸镧超细粉体的合成与性能     

田莉玉  于德利  刘淑芹 《世界地质》2008,27(3)

采用溶胶低温燃烧法和高温固相反应法制备了锶掺杂的正铌酸镧（La0.95Sr0.05NbO4）超细陶瓷粉体。应用XRD、SEM和激光粒度分析仪等对陶瓷粉体的物相、粒度和粒度分布进行了表征,同时考察了两种方法制备的粉体的烧结性能。结果表明：采用溶胶低温燃烧法制备的La0.95Sr0.05NbO4（LSNb）为粒径〈100 nm、粒度分布范围窄的超细粉体;高温固相反应法制备的粒径为0.5-1.0μm、呈球形的LSNb超细陶瓷粉体。溶胶低温燃烧法制备的粉体在1 250℃烧结10 h形成致密的陶瓷片;高温固相反应法制备的粉体在1 400℃以上烧结10 h致密。两种LSNb致密膜均具有一定的透氢作用,900℃氢渗速率分别为1.96×10^-3mL·cm^-2·min^-1和1.67×10^-3mL·cm^-2·min^-1。  相似文献   

Contrasting Regional Responses of Indian Summer Monsoon Rainfall to Exhausted Spring and Concurrently Emerging Summer El Ni?o Events     

E.K.KRISHNA KUMAR  S.ABHILASH  SANKAR SYAM  P.VIJAYKUMAR  K.R.SANTOSH  A.V.SREENATH 《大气科学进展》2023,40(4):697-710

The inverse relationship between the warm phase of the El Ni?o Southern Oscillation(ENSO) and the Indian Summer Monsoon Rainfall(ISMR) is well established. Yet, some El Ni?o events that occur in the early months of the year(boreal spring) transform into a neutral phase before the start of summer, whereas others begin in the boreal summer and persist in a positive phase throughout the summer monsoon season. This study investigates the distinct influences of an exhausted spring El Ni?o(springtime)...  相似文献   

2021年山东夏季降水异常特征及成因分析     

商林  孟祥新 《沙漠与绿洲气象(新疆气象)》2024,18(2):61-67

基于NCEP再分析资料和山东省122个国家地面观测站数据,对2021年山东夏季降水异常特征及成因进行研究。2021年夏季山东平均降水量较常年偏多25.3%,降雨过程较多,其中,6月降水偏多主要是由于西太平洋副热带高压（以下简称:副高）北抬造成;7月中旬降水偏多主要是由于副高强度偏强,副高边缘暖湿气流为山东降水提供了充足水汽,下旬降水偏多是由于台风“烟花”带来强降水;8月降水偏多主要是下旬副高强度偏强,水汽输送充沛造成的。此外,2021年夏季山东降水空间分布不均匀,呈西多东少的空间分布。进一步分析了近3次拉尼娜事件发现,夏季副高强度偏强是造成近3个拉尼娜衰减年夏季山东降水空间分布异常的主要原因。夏季副高强度是拉尼娜次年山东夏季降水的重要预测因子。  相似文献   

基于Markov链的金川铜镍矿床超基性岩体侵位过程模拟及找矿启示     

邓浩  刘晓霞  赵莹 《江苏地质》2016,40(3):395-402

金川铜镍矿床是世界第三大铜镍硫化物岩浆矿床,现有研究表明其成矿模式为岩浆通道成矿,但是对于金川超基性岩体的侵位过程存在较大争议。为探索岩体的侵位过程,将岩浆侵位描述为马尔可夫(Markov)过程,提出一种基于Markov链的岩体侵位模拟算法,实现对金川超基性岩体侵位过程的模拟。以金川Ⅱ矿区为例,探讨了侵位过程与矿化的关联及岩浆通道骨架,为在矿床深部寻找第二成矿空间提供方向和线索。  相似文献   

近年来厄尔尼诺期间北赤道流输运的年际变化   总被引：1，自引：0，他引：1       下载免费PDF全文

吴国丽  王庆业  翟方国  胡敦欣 《海洋科学》2016,40(2):118-127

为了研究近年来厄尔尼诺期间北赤道流输运的年际变化,本文利用海洋客观分析数据MOAA GPV(Grid Point Value of the Monthly Objective Analysis)以及P-vector方法计算了北太平洋绝对地转流,探讨了2001~2013年期间厄尔尼诺与北赤道流输运之间的关系。在此期间发生的4次厄尔尼诺事件中,北赤道流输运在2002~2003、2006~2007、2009~2010年的厄尔尼诺成熟期都出现了明显的增强,但是在2004~2005年的厄尔尼诺成熟期并没有明显的增强。进一步分析发现,在2002~2003年、2006~2007年、2009~2010年的厄尔尼诺成熟期,10°N以南的热带西北太平洋区域出现了负的海面高度异常和气旋式环流异常,这主要是由热带环流区域出现的西风异常和正的Ekman抽吸通过Rossby波西传到热带西太平洋区域所致;但是在2004~2005年厄尔尼诺成熟期,海面温度异常的分布明显不同,西风异常和正的Ekman抽吸异常明显北移,导致负的海面高度异常和气旋式环流异常出现在了10°N以北的西北太平洋区域,使得北赤道流输运在2004~2005年的厄尔尼诺成熟期没有明显的增强。  相似文献   

Granitoid emplacement by multiple sheeting during Variscan dextral transpression: The Saint-Laurent – La Jonquera pluton (Eastern Pyrenees)     

《Journal of Structural Geology》2016

The structural study of the Saint-Laurent – La Jonquera pluton (Eastern Pyrenees), a Variscan composite laccolithic intrusion emplaced in metasedimentary and gneissic rocks of the Roc de Frausa dome, by means of the anisotropy of magnetic susceptibility (AMS) technique has allowed the determination of the nature and orientation of its magmatic fabrics. The magmatic foliation has a predominant NE–SW strike and the mean lineation is also NE–SW trending with a shallow plunge. A strain gradient is measured so that the tonalites to granodiorites that form the basal parts of the pluton, and are intruded into amphibolite-facies metamorphic rocks, recorded the highest anisotropies, whereas the monzogranites and leucogranites, emplaced into upper crustal, low-grade metamorphic rocks, are weakly deformed. These results point to the synkinematic sequential emplacement of multiple granitoid sheets, from less to more differentiated magmatic stages, during the Late Carboniferous D₂ event characterized by an E–W-trending dextral transpression. The magmatic foliation appears locally disturbed by the effects of two tectonic events. The first of them (D₃) produced mylonitization of granitoids along NW–SE retrograding shear zones and open folds in the host Ediacaran metasediments of the Roc de Frausa massif, likely during late Variscan times. Interference between D₂ and D₃ structures was responsible for the dome geometry of the whole Roc de Frausa massif. The second and last perturbation consisted of local southward tilting of the granitoids coupled to the Mesozoic–Cenozoic cover during the Alpine.  相似文献   

LINKAGE BETWEEN INDIAN OCEAN DIPOLE AND TWO TYPES OF El NI?O AND ITS POSSIBLE MECHANISMS     

董笛  何金海  李建平 《热带气象学报(英文版)》2016,22(2):172-181

After compositing three representative ENSO indices,El Nio events have been divided into an eastern pattern(EP) and a central pattern(CP).By using EOF,correlation and composite analysis,the relationship and possible mechanisms between Indian Ocean Dipole(IOD) and two types of El Nio were investigated.IOD events,originating from Indo-Pacific scale air-sea interaction,are composed of two modes,which are associated with EP and CP El Ni o respectively.The IOD mode related to EP El Nio events(named as IOD1) is strongest at the depth of 50 to 150 m along the equatorial Indian Ocean.Besides,it shows a quasi-symmetric distribution,stronger in the south of the Equator.The IOD mode associated with CP El Nio(named as IOD2) has strongest signal in tropical southern Indian Ocean surface.In terms of mechanisms,before EP El Nio peaks,anomalous Walker circulation produces strong anomalous easterlies in equatorial Indian Ocean,resulting in upwelling in the east,decreasing sea temperature there;a couple of anomalous anticyclones(stronger in the south) form off the Equator where warm water accumulates,and thus the IOD1 occurs.When CP El Nio develops,anomalous Walker circulation is weaker and shifts its center to the west,therefore anomalous easterlies in equatorial Indian Ocean is less strong.Besides,the anticyclone south of Sumatra strengthens,and the southerlies east of it bring cold water from higher latitudes and northerlies west of it bring warm water from lower latitudes to the 15° to 25°S zone.Meanwhile,there exists strong divergence in the east and convergence in the west part of tropical southern Indian Ocean,making sea temperature fall and rise separately.Therefore,IOD2 lies farther south.  相似文献