Paleoproterozoic juvenile magmatism within the northeastern sector of the São Francisco paleocontinent: Insights from the shoshonitic high Ba–Sr Montezuma granitoids     

《地学前缘(英文版)》2020,11(5):1821-1840

New,integrated petrographic,mineral chemistry,whole rock geochemical,zircon and titanite UPb geochronology,and zircon Hf isotopic data from the Montezuma granitoids,as well as new geochemical results for its host rocks represented by the Corrego Tingui Complex,provides new insights into the late-to post-collisional evolution of the northeastern Sao Francisco paleocontinent.U-Pb zircon dates from the Montezuma granitoids spread along the Concordia between ca.2.2 Ga to 1.8 Ga and comprise distinct groups.Group I have crystallization ages between ca.2.15 Ga and 2.05 Ga and are interpreted as inherited grains.Group II zircon dates vary from 2.04 Ga to1.9 Ga and corresponds to the crystallization of the Montezuma granitoids,which were constrained at ca.2.03 Ga by the titanite U-Pb age.Inverse age zoning is common within the ca.1.8 Ga Group III zircon ages,being related to fluid isotopic re-setting during the Espinhaco rifiting event.Zircon ε_(Hf)(t) analysis show dominantly positive values for both Group I(-4 to+9) and Ⅱ(-3 to+8) zircons and T_(DM2) model ages of 2.7-2.1 Ga and 2.5-1.95 Ga,respectively.Geochemically,the Montezuma granitoids are weakly peraluminous to metaluminous magnesian granitoids,enriched in LILES and LREE,with high to moderate Mg#and depleted in some of the HFSE.Their lithochemical signature,added to the juvenile signature of both inherited and crystallized zircons,allowed its classification as a shoshonitic high Ba-Sr granitoid related to a late-to post-collisional lithosphere delamination followed by asthenospheric upwelling.In this scenario,the partial melting of the lithospheric mantle interacted with the roots of an accreted juvenile intra-oceanic arc,being these hybrid magma interpreted as the source of the Montezuma granitoids.The Corrego Tingui Complex host rocks are akin to a syn-to late-collisional volcanic arc granitoids originated from the partial melting of ancient crustal rocks.The results presented in this study have revealed the occurrence of juvenile rocks,probably related to an island arc environment,that are exotic in relation to the Paleo-to Neoarchean crust from the Sao Francisco paleocontinent's core.  相似文献   

Post‐Great Oxidation Event Orosirian–Statherian iron formations on the São Francisco craton: Geotectonic implications     

Carlos A. Rosire  Andrey Bekker  Vassily K. Rolim  Joo Orestes S. Santos 《Island Arc》2019,28(4)

The protocratonic core of the São Francisco craton assembled during the 2.1–2.0 Ga Transamazonian orogeny. Orosirian Fe‐rich sequences that extend from the northwestern border of the São Francisco protocraton (Colomi Group) to the southeast under the Espinhaço Belt (the < 1.99 Ga Serra da Serpentina Group) record the opening of an intracratonic basin with the episodically developed ferruginous waters prior to the initiation of the Espinhaço rift at 1.8 Ga. Ferruginous conditions developed again during deposition of the Canjica Iron Formation of the < 1.7 Ga Serra de São José Group in the Espinhaço rift (contemporaneously with felsic magmatism; Conceição do Mato Dentro Rhyolite and Borrachudos Granitic Suite) and extensive sandstones of the < (1666 ±32) Ma Itapanhoacanga and < (1683 ±11) Ma São João da Chapada Formations. In the upper São João da Chapada Formation, banded hematitic phyllite also records input of Fe‐rich fluids. The young age of these iron formations with respect to the conventionally accepted 1.88 Ga age for the youngest shallow‐marine Paleoproterozoic iron formations, the apparent absence of granular facies (granular iron formations), and yet shallow‐water (above fair‐weather base) depositional environment indicate that an unusual setting developed in a large basin after the Great Oxidation Event, in the aftermath of the Transamazonian orogeny. We propose that mantle plumes led to the opening of a previously unrecognized rift system, that could have caused the magmatism, supplied hydrothermal Fe and led to the opening of the Espinhaço, Pirapora, and Paramirim rifts, later obliterated by the Araçuaí orogenic belt during the Neoproterozoic to Early Paleozoic Brasiliano orogeny. The rift system did not develop into an open continental margin but probably evolved into a broad sag basin, stretching across the São Francisco and Congo cratons.  相似文献   

积雪在El Niño影响东亚夏季气候异常中的作用          下载免费PDF全文

王妍凤  孙旭光  杨修群 《地球物理学报》2017,60(9):3325-3337

本文利用1948-2010年Global Land Data Assimilation System（GLDAS）NOAH陆面模式资料、GPCC月平均降水资料和NCAR/NCEP全球月平均再分析资料，采用滤波、距平合成和线性相关等方法，分析了El Niño成熟位相冬季欧亚大陆积雪异常的分布特征，研究了关键区积雪融化对后期春、夏季土壤湿度、土壤温度以及大气环流与降水的影响，揭示了El Niño事件通过关键区积雪储存其强迫信号并影响东亚夏季气候异常的机制和过程.主要结论如下：El Niño成熟阶段冬季伊朗高原、巴尔喀什湖东北部和青藏高原南麓区域是雪深异常的三个关键区，这些区域的雪深、雪融和土壤湿度有明显的正相关；这三个关键区雪深异常通过春季融雪将冬季El Niño信号传递给春、夏季局地土壤湿度，通过减少感热通量和增加潜热通量对大气环流产生影响；春末夏初伊朗高原土壤湿度异常对东亚夏季气候异常的影响最大，其引起的降水异常与El Niño次年夏季降水异常分布基本一致，春夏季青藏高原南麓和巴尔喀什湖附近土壤湿度也都明显增加，均会对中国华北降水增加有显著正贡献.总之，在利用El Niño事件研究和预测东亚夏季气候异常时，还应考虑关键区雪深异常对El Niño信号的存储和调制作用.  相似文献   

Global ENSO-streamflow teleconnection,streamflow forecasting and interannual variability     

FRANCIS H. S. CHIEW  THOMAS A. McMAHON 《水文科学杂志》2013,58(3):505-522

Abstract

El Niño Southern Oscillation (ENSO) has been linked to climate anomalies throughout the world. This paper presents an overview of global ENSO-streamflow teleconnection and identifies regions where the relationship may be exploited to forecast streamflow several months ahead. The teleconnection is investigated by fitting a first harmonic to 24-month El Niño streamflow composites from 581 catchments worldwide and the potential for forecasting is investigated by calculating the lag correlation between streamflow and two indicators of ENSO. The analyses indicate clear ENSO-streamflow teleconnections in many catchments, some of which are consistent across large geographical regions. Strong and regionally consistent ENSO-streamflow teleconnections are identified in Australia and New Zealand, South and Central America, and weaker signals are identified in some parts of Africa and North America. The results suggest that the ENSO-streamflow relationship and the serial correlation in streamflow can be used to successfully forecast streamflow. The streamflow forecasts can be used to help manage water resources, particularly in systems with high interannual variability in Australia, southern and drier parts of Africa and some areas of North America.  相似文献   

Connections Between Different Types of El Ni~no and Southern/Northern Oscillation          下载免费PDF全文

PENG Jingbei  ZHANG Qingyun  CHEN Lieting 《Acta Meteorologica Sinica》2011,25(4):506-516

It has long been acknowledged that there are two types of El Ni(n)o events,i.e.,the eastern Pacific El Ni(n)o (EE) and the central Pacific El Ni(n)o (CE),according to the initial position of the anomalous warm water and its propagation direction.In this paper,the oceanic and atmospheric evolutions and the possible mechanisms of the two types of El Ni(n)o events were examined.It is found that all the El Ni(n)o events,CE or EE,could be attributed to the joint impacts of the eastward advection of warm water from the western Pacific warm pool (WPWP) and the local warming in the equatorial eastern Pacific.Before the occurrence of CE events,WPWP had long been in a state of being anomalous warm,so the strength of eastward advection of warm water was much stronger than that of EE,which played a major role in the formation of CE.While for the EE events,most contribution came from the local warming of the equatorial eastern Pacific.It is further identified that the immediate cause leading to the difference of the two types of El Ni(n)o events was the asynchronous variations of the Southern Oscillation (SO) and the Northern Oscillation (NO) as defined by Chen in 1984.When the transition from the positive phase of the NO (NO+) to NO- was prior to that from SO+ to SO-,there would be eastward propagation of westerly anomalies from the tropical western Pacific induced by NO and hence the growth of warm sea surface temperature anomalies in WPWP and its eastward propagation.This was followed by lagged SO-induced weakening of southeast trade winds and local warming in the equatorial eastern Pacific.These were conducive to the occurrence of the CE.On the contrary,the transition from SO+ to SO- leading the transition of NO would favor the occurrence of EE type events.  相似文献   

What Drives the Decadal Variability of Global Tropical Storm Days from 1965 to 2019?     

Yifei DAI  Bin WANG  Weiyi SUN 《大气科学进展》2022,39(2):344-353

The tropical storm day(TSD)is a combined measure of genesis and lifespan.It reflects tropical cyclone(TC)overall activity,yet its variability has rarely been studied,especially globally.Here we show that the global total TSDs exhibit pronounced interannual(3-6 years)and decadal(10 years)variations over the past five-to-six decades without a significant trend.The leading modes of the interannual and decadal variability of global TSD feature similar patterns in the western Pacific and Atlantic,but different patterns in the Eastern Pacific and the Southern Indian Ocean.The interannual and decadal leading modes are primarily linked to El Ni?o-Southern Oscillation(ENSO)and Pacific Decadal Oscillation(PDO),respectively.The TSDs-ENSO relationship has been steady during the entire 55-year period,but the TSDs-PDO relationship has experienced a breakdown in the 1980 s.We find that the decadal variation of TSD in the Pacific is associated with the PDO sea surface temperature(SST)anomalies in the tropical eastern Pacific(PDO-E),while that in the Atlantic and the Indian Ocean is associated with the PDO SST anomalies in the western Pacific(PDO-W).However,the PDO-E and PDO-W SST anomalies are poorly coupled in the 1980 s,and this"destructive PDO"pattern results in a breakdown of the TSDs-PDO relationship.The results here have an important implication for seasonal to decadal predictions of global TSD.  相似文献   

用于厄尔尼诺-南方涛动(ENSO)研究的海气耦合模式综述：中间型和混合型模式     

张荣华 《海洋与湖沼》2024,55(1):1-23

厄尔尼诺-南方涛动(El Niño-Southern Oscillation, ENSO)是地球气候系统中最强的年际变率信号, 起源于热带太平洋海气相互作用过程, 并对全球的天气和气候等产生显著的影响。过去几十年来, 广泛、深入而细致的海气相互作用研究致力于发展和改进海气耦合模式以用于ENSO模拟和预测, 各种类型的海气耦合模式应运而生。经过半个多世纪的努力, ENSO数值模式及其应用已经取得了巨大进展, 包括已发展了一些高度理想化的概念(concept)模型来解释ENSO准周期性循环(包括正负反馈机制等); 同时也已发展了几类复杂程度不同的海气耦合模式并用于对ENSO的真实模拟和实时预测等研究, 尤其是已能提前6个月或更长时间对ENSO事件的发生和发展等进行有效的实时预测。其中最为复杂的模式是基于原始方程组的大气环流模式(Atmospheric General Circulation Models, AGCMs)与海洋环流模式(Oceanic General Circulation Models, OGCMs)等所组成的环流型耦合模式(Coupled General Circulation Models, CGCMs), 这类模式变量取为完全变量的形式(如总的海表温度场, 其可以分解为气候态部分和年际异常部分), 还考虑了尽可能详尽的物理过程及其参数化方案。中间型耦合模式(Intermediate Coupled Models, ICMs)是一类介于高度理想化概念模型与复杂的环流型耦合模式之间的简化模式, 其对应的控制方程组采用距平形式, 直接取大气和海洋年际异常场作为预报变量(如海表温度年际异常), 而相应的气候平均态部分则由对应的观测资料来给定; 大气与海洋模式间的耦合采用异常耦合(anomaly coupling)。混合型耦合模式(Hybrid Coupled Models, HCMs)是另一类简化的海气耦合模式, 其中海洋或大气模式有一个分量模式采用了简化的距平类模式(类似于ICMs),而另一个分量模式则采用环流型模式(General Circulation Models, GCMs); 如可采用统计的大气风应力年际异常模式与OGCM间的耦合而构建一种HCM_OGCM,也可采用简化的海洋距平类模式(如ICM中的海洋分量模式)与AGCM间的耦合而构建另一种HCM^AGCM。历史上, ICMs、HCMs和CGCMs等这几类耦合模式都在ENSO理论体系的发展、数值模拟和实时预测等方面都起到了重要作用。本文主要回顾作者与合作者所研发的ICMs和HCMs的构建、特点和应用例子等。  相似文献   

厄尔尼诺的发生与行星运动     

施平 《热带海洋学报》1993,(3)

厄尔尼诺(El Ni(?)o)现象是海-气耦合系统异常变化的表现,其起因可能不是唯一的,行星运动对地球运动的影响可能会导致El Ni(?)o的发生。根据4个半世纪内El Ni(?)o发生的历史资料,分析其发生和行星运动的关系,得出的结论是:木星赤纬的变化和火星大冲与El Ni(?)o。的发生有显著的关系,表明这2颗行星的运动可能影响El Ni(?)o的发生。文中还根据分析结桌和El Ni(?)o混沌机制的观点,探讨了行星运动对海-气系统变化的影响机制。  相似文献   

Variational iteration solving method for El Nio phenomenon atmospheric physics of nonlinear model     

MO Jiaqi  *  WANG Hui  LIN Wantao  LIN Yihua. Anhui Normal University  Wuhu  China. Division of Computional Science  E-Institute of Shanghai Universities  Shanghai Jiaotong University Shanghai  China. Chinese Academy of Meteorological Sciences  Beijing  China. State Laboratory of Numerical Modeling for Atmospheric Sciences  Geophysical Fluid Dynamics  Institute of Atmosheric Physics  Chinese Academy of Sciences  Beijing  China 《海洋学报(英文版)》2005,(5)

1 IntroductionThe El Ni’o atmospheric physics oscillation is anabnormal phenomenon involved in the tropical Pacificocean- atmosphere interactions. Studies on the El Ni(ophenomenon are very attractive (Lin et al., 2000; Linet al., 2001, 2002; Wang, 2001; Feng et al., 2001;Feng et al., 2002; Liu et al., 2002; Wei and Chen,2003; Xie et al., 2002; Zhu et al., 2002; Pu et al.,2003; Gu et al., 2004; Yu and Liu, 2004). Lin and Mo(2004), Mo and Lin (2004) and Mo et al. (2004) alsostudied a s…  相似文献   

厄尔尼诺/拉尼娜信号循环回路及其传播特性研究   总被引：4，自引：0，他引：4  

乔方利  于卫东  袁业立 《海洋学报》2004,26(4):1-8

基于1992～2001年卫星高度计资料分析了海面高度距平在厄尔尼诺/拉尼娜(El Niño/La Niña)现象中的演变过程,发现:(1)在El Niño过程中,海面高度正距平信号从西太平洋沿赤道海域向东传播至东海岸,然后分成南北两支,北支在10°N附近从东太平洋传回西太平洋的信号最强,到达西太沿岸海域再传回赤道,表明El Niño信号传播在北半球存在一明显循环回路.赤道以南循环圈不及赤道以北环路清晰.东太平洋的季节变化信号主要通过6°N,10°N和8°S附近的3个通道向西太平洋传播.La Niña信号主要从5°N和7°S向西传播;(2)在大洋海盆尺度快速传播信号背景下,存在波长700～800km的慢速传播信号,两类信号将信息在太平洋内传送.传播速度分析表明,慢速传播信号的相速与Rossby波相速相符,而快速传播信号应该是海洋对大气变异的响应.  相似文献