34000年以来南极汞沉降通量的估算          下载免费PDF全文

尹雪斌  孙立广  谢周清 《极地研究》2003,15(3):207-213

本文统计分析了南极DomeC冰芯中汞含量和降水指征参数δ1 8O值、1 0 Be浓度的关系 ,发现冰芯中Hg含量和δ1 8O值、1 0 Be浓度变化一致 ,表明DomeC冰芯汞含量受到冰雪积累率的影响 ,而且三者变化的高度同步性可能说明其原始驱动力也是一致的 ,从而冰芯中Hg含量可以和1 0 Be浓度一样作为冰雪积累率估算的替代性指标。此外 ,利用δ1 8O数据 ,系统估算了 340 0 0年以来南极汞沉降通量的变化。结果表明 ,DomeC冰芯汞沉降通量在末次冰盛期 (LGM)最高 ,为 3.80pgcm- 2 a- 1 ,约是全新世汞沉降通量 ( 1 .0 8pgcm- 2 a- 1 )的 3.5倍 ,该变化可能主要受到汞的自然排放量影响。  相似文献   

Dating a 109.9 m ice core from Dome A(East Antarctica) with volcanic records and a firn densification model     

LI ChuanJin  XIAO CunDe  HOU ShuGui  REN JiaWen  DING MingHu  & GUO Rui 《中国科学:地球科学(英文版)》2012,(8):1280-1288

A 109.9 m ice core was extracted at a location about 300 m away from the Dome A summit(80°00′S,77°21″E) by the Chinese team of the International Trans-Antarctic Science Expedition(ITASE) during the 21st Chinese National Antarctica Research Expedition(CHINARE) in January 2005.Two independent methods were used for dating the ice core,volcanic event markers shown by prominent non-sea-salt sulfate(nss-SO42) and the Herron and Langway(H-L) firn densification model.Six promi-nent volcanic events(Agung 1963 AD,Tambora 1815 AD,Kuwae 1453 AD,Unknown 1259 AD,Taupo 186 AD and Pinatubo 1050 BC) were identified by comparison with other Antarctic ice cores.Based on the mean accumulation rates be-tween adjacent events,we estimate the age at the firn pore close-off depth(102 m) was 3516±100 a BP.This is the oldest close-off age ever reported from the Antarctic and the Greenland ice sheets.Calculations using the H-L model show that the age at the same depth is 3581±100 a BP.The two dating techniques differ by 65 years,or～1.8% of the record.We calculated the bottom age of the ice core as 4009±150 a BP using the volcanic dating method and 4115±150 a BP using the H-L model method.  相似文献   

2007/2008年度中国南极冰穹A考察新进展   总被引：1，自引：0，他引：1       下载免费PDF全文

孙波  崔祥斌 《极地研究》2008,20(4):371-378

冰穹A(DomeA)是南极冰盖最高区域,其独特的地理位置和蕴藏的科学资源受到国际科学界的普遍关注,近年来成为国际南极科学考察研究的重要前沿区域。中国第24次南极考察(CHINARE24,2007/2008年度)继续开展DomeA地区考察活动,具体执行内陆建站选址任务和国际极地年中国行动计划--PANDA计划。本次内陆冰盖队在到达DomeA后,在DomeA核心区域以及中山站-DomeA断面上开展了多学科系统性的科考工作,取得了以"南极DomeA科学考察"、"内陆建站选址"和"中国南极内陆考察支撑能力建设"为代表的新进展,提升了我国南极内陆考察的支撑保障能力和科学认知水平。  相似文献   

Ore-structure relationships at Sishen Mine,Northern Cape,Republic of South Africa,based on fully-constrained implicit 3D modelling     

《Ore Geology Reviews》2017

A fully-constrained, implicit, 3D geological model of Sishen Mine reveals the original, pre-mining geometry of ore bodies, host rocks to mineralization and major structures. There are several overlapping controls, at a variety of scales, on the position, depth and geometry of laminated and conglomeratic ore. Most of these controls are structural or may be reconciled with the kinematic history of this part of the Maremane Dome. A series of near-horizontal sections, through the entire 3D model, demonstrates the manner in which these controls overlap and interact. First-order or large-scale controls comprise broad domes, which show preservation of laminated ore around their rims, outside of which conglomeratic ore occurs. Second-order controls comprise grabens and half-grabens, which are often bounded by strike-persistent normal faults, which show fault drag on their western flanks due to inversion, along with preservation of BIF-related supergene ore and conglomeratic ore. A type example is the thick, deep, linear ore to the west of the Sloep Fault. Third-order controls on the preservation of mineralization comprise downthrown blocks to the north of reactivated E-W, SE/ESE- or NE/ENE-trending conjugate faults. Upthrow to the south could be attributed to the 1.15–1.0 Ga NNW-directed Lomanian (Namaqua-Natal) Orogeny. Palaeosinkholes comprise fourth-order controls, which are superimposed on higher-order controls. Palaeosinkholes, which form the bulk of current mining, comprise deep, conical depressions with anomalous thicknesses of chert, chert breccia and haematite. Due to their limited size, the steepness of all units and the often chaotic nature of detached and slumped blocks in their centres, these volumes reflect longstanding models on palaeosinkhole development and very local ore control.  相似文献   

藏南错那洞淡色花岗岩年代学研究及其对藏南拆离系活动时间的限定   总被引：6，自引：3，他引：3  

董汉文  许志琴  孟元库  易治宇 《岩石学报》2017,33(12):3741-3752

北喜马拉雅片麻岩穹窿带(NHGD)内保存了大陆碰撞后青藏高原中下地壳的构造变形、高级变质、陆壳深熔作用等重要信息,是研究喜马拉雅造山带的深部岩浆作用和构造变形之间的耦合关系、深部岩浆活动乃至青藏高原隆升历史等大陆动力学过程的关键部位。本文对藏南错那洞穹窿内淡色花岗岩进行锆石LA MC-ICP-MS U-Pb、白云母~(40)Ar/~(39)Ar年代学和岩石地球化学分析。锆石U-Pb定年和白云母~(40)Ar/~(39)Ar测年结果表明错那洞淡色花岗岩形成于19.5±0.3Ma~19.7±0.7Ma,冷却年龄为15Ma。岩石地球化学特征显示该花岗岩具有明显的Eu负异常,稀土配分模式和微量元素蛛网图与以Manaslu为代表的高喜马拉雅淡色花岗岩一致,而不同于具有加厚地壳的埃达克岩的特征的北喜马拉雅淡色花岗岩,其形成于与南北向拆离相关的伸展环境。  相似文献   

斯里兰卡穹顶区的形成和演变机制分析     

K. B. S. S. J EKANAYAKA  王卫强 《南京气象学院学报》2019,11(2):198-207

通过SODA再分析资料和AVISO观测资料研究了斯里兰卡穹顶区（SLD）的迁移和消散机制.斯里兰卡穹顶区是孟加拉湾西南部的一个气旋涡旋,主要出现在西南季风（5-9月）期间,与西南季风海流侵入孟加拉湾同时存在.正风应力旋度引起的Ekman抽吸是形成SLD的主要原因.回归分析结果表明SLD区域的风应力旋度与Ekman抽吸存在较强的正相关（r²=0.93,p>0.5）.此外,结果表明SLD在发展过程中的移动主要受正风应力旋度移动的影响,SLD的消减与该正风应力旋度减弱和西传的暖Rossby波有关,而冷Rossby波的传播有益于SLD的发展.在SLD消减时期,孟加拉湾涡旋（BBD）独立发展并进一步与SLD融合,回归分析发现BBD区域的Ekman抽吸与当地风应力旋度的关系密切（r²=0.76,p>0.5）,这表明了BBD在形成阶段由局地的风应力主导.9月之后,风应力旋度减弱,BBD和SLD开始了合并过程.动力方面,EKE分析显示SLD衰退的同时,BBD的EKE大幅增加;热力方面,10-11月时,由Ekman抽吸引起的SLD和BBD次表层冷水汇合,清晰地表明了二者之间的热动力学联系.  相似文献   

Variation of the North Equatorial Current,Mindanao Current,and Kuroshio Current in a High-Resolution Data Assimilation during 2008–2012     

ZHAI Fangguo  WANG Qingye  WANG Fujun  Hu Dunxin 《大气科学进展》2014,31(6):1445-1459

Outputs from a high-resolution data assimilation system,the global Hybrid Coordinate Ocean Model and Navy Coupled Ocean Data Assimilation （HYCOM＋NCODA） 1/12° analysis,were analyzed for the period September 2008 to February 2012.The objectives were to evaluate the performance of the system in simulating ocean circulation in the tropical northwestern Pacific and to examine the seasonal to interannual variations of the western boundary currents.The HYCOM assimilation compares well with altimetry observations and mooring current measurements.The mean structures and standard deviations of velocities of the North Equatorial Current （NEC）,Mindanao Current （MC） and Kuroshio Current （KC） also compare well with previous observations.Seasonal to interannual variations of the NEC transport volume are closely correlated with the MC transport volume,instead of that of the KC.The NEC and MC transport volumes mainly show well-defined annual cycles,with their maxima in spring and minima in fall,and are closely related to the circulation changes in the Mindanao Dome （MD） region.In seasons of transport maxima,the MD region experiences negative SSH anomalies and a cyclonic gyre anomaly,and in seasons of transport minima the situation is reversed.The sea surface NEC bifurcation latitude （NBL） in the HYCOM assimilation also agrees well with altimetry observations.In 2009,the NBL shows an annual cycle similar to previous studies,reaching its southernmost position in summer and its northernmost position in winter.In 2010 and 2011,the NBL variations are dominantly influenced by La Ni（n）a events.The dynamics responsible for the seasonal to interannual variations of the NEC-MC-KC current system are also discussed.  相似文献   

南极中山站-昆仑站间地壳厚度分布          下载免费PDF全文

冯梅  安美建  安春雷  史贵涛  赵越  李院生  Douglas Wiens 《极地研究》2014,26(2):177-185

自第4个国际极地年2007/2008开始至2013年,中国南极内陆冰盖科考队相继在自南极大陆边缘的中山站至东南极地形最高点昆仑站(Dome A)一线进行了低温甚宽频地震观测。本文对7个天然地震台站数据进行了分析,提取了这些台站的S波接收函数,据此反演获得了这些台站下的地壳厚度分布。结果显示:随着纬度的升高,地壳厚度由大陆边缘的中山站下的约38 km逐渐增加至CHNB台下的58 km,随后又于CHNA台站下方减薄至47 km,然后快速增大到南极地形最高点昆仑站(Dome A)下的62 km。昆仑站或Dome A是南极大陆地壳最厚的地方。从中山站至昆仑站之间地壳厚度的变化与冰下地貌变化存在明显的相关性,它们都说明了从中山站至CHNB之间地壳构造相对均匀。在距昆仑站约200 km的CHNA台下的地壳厚度(约47 km)明显比临近台站地壳偏薄,这可能说明了甘伯采夫山脉地壳侧向变化较大,即其形成时所遭受的构造作用较复杂。  相似文献   

Thermal pulse induced by emplacement of Ramba leucogranites in southern Tibet     

Xu Chu  Ozan Akça  Fred Gaidies  Ivano Gennaro  Weiqiang Ji 《Journal of Metamorphic Geology》2023,41(1):121-141

The thermal histories of Himalayan leucogranites provide critical information for unravelling the post-collisional geodynamics of the Himalayas. The Ramba Dome is located at the intersection of the Tethyan Himalayan leucogranite belt with the Yadong–Gulu Rift and hosts several generations of granitic intrusions. Of these intrusions, the 8-Ma two-mica granites and garnet leucogranite dykes are the youngest of Himalayan leucogranites. In this study, we focus on the carbonaceous staurolite schist located ~1.3 km from the intrusion to constrain the thermal history of the aureole that marked the cessation of leucogranite magmatism. The schist contains euhedral garnet and staurolite porphyroblasts in a foliated matrix of muscovite + biotite + chlorite + plagioclase + quartz + graphite. The staurolite shows minor compositional variations from the inclusion-free core to the inclusion-rich rim. By contrast, the garnet features a distinctive bell-shaped Mn profile and increasing Mg# from the garnet core to rims. In a graphite-bearing equilibrium phase diagram for a modified bulk composition with garnet cores removed, the garnet rim composition suggests a peak temperature of ~550°C, consistent with an independent thermometer based on the Raman spectra of carbonaceous materials (RSCM; 548 ± 9°C). The P–T condition lies within the narrow low-variance field bracketed by the staurolite-in and chlorite-out boundaries, indicating minimal overstepping of staurolite nucleation and growth. On the other hand, the garnet core composition indicates 520°C at 2.5 kbar, about 40°C higher than the predicted garnet-in boundary (~480°C). This apparent temperature overstep corresponds to a small chemical affinity (<5 kJ/mol 12 O) for garnet nucleation, comparable to previous estimates. The sharp boundaries of the high-Ca sector zoning in the core indicate limited diffusion modification (~1.5 Ma if at the peak temperature). The short thermal pulse involves advective heat transfer by leucogranite emplacement, followed by rapid cooling toward the end of Himalayan magmatism and rapid exhumation likely facilitated by the Yadong–Gulu Rift.  相似文献