Pan-African Tectonism in the Western Maud Belt: P-T-t Path for High-grade Gneisses in the H.U. Sverdrupfjella, East Antarctica

Extensive high-grade polydeformed metamorphic provinces surroundingArchaean cratonic nuclei in the East Antarctic Shield recordtwo tectono-thermal episodes in late Mesoproterozoic and lateNeoproterozoic–Cambrian times. In Western Dronning MaudLand, the high-grade Mesoproterozoic Maud Belt is juxtaposedagainst the Archaean Grunehogna Province and has traditionallybeen interpreted as a Grenvillian mobile belt that was thermallyoverprinted during the Early Palaeozoic. Integration of newU–Pb sensitive high-resolution ion microprobe and conventionalsingle zircon and monazite age data, and Ar–Ar data onhornblende and biotite, with thermobarometric calculations onrocks from the H.U. Sverdrupfjella, northern Maud Belt, resultedin a more complex P–T–t evolution than previouslyassumed. A c. 540 Ma monazite, hosted by an upper ampibolite-faciesmineral assemblage defining a regionally dominant top-to-NWshear fabric, provides strong evidence for the penetrative deformationin the area being of Pan-African age and not of Grenvillianage as previously reported. Relics of an eclogite-facies garnet–omphaciteassemblage within strain-protected mafic boudins indicate thatthe peak metamorphic conditions recorded by most rocks in thearea (T = 687–758°C, P = 9·4–11·3kbar) were attained subsequent to decompression from P >12·9 kbar. By analogy with limited U–Pb singlezircon age data and on circumstantial textural grounds, thisearlier eclogite-facies metamorphism is ascribed to subductionand accretion around 565 Ma. Post-peak metamorphic K-metasomatismunder amphibolite-facies conditions is ascribed to the intrusionof post-orogenic granite at c. 480 Ma. The recognition of extensivePan-African tectonism in the Maud Belt casts doubts on previousRodinia reconstructions, in which this belt takes a pivotalposition between East Antarctica, the Kalahari Craton and Laurentia.Evidence of late Mesoproterozoic high-grade metamorphism duringthe formation of the Maud Belt exists in the form of c. 1035Ma zircon overgrowths that are probably related to relics ofgranulite-facies metamorphism recorded from other parts of theMaud Belt. The polymetamorphic rocks are largely derived froma c. 1140 Ma volcanic arc and 1072 ± 10 Ma granite. KEY WORDS: Maud Belt; Pan-African orogeny; geochronology; P–T–t path, East Antarctica     

江苏省龙卷发生特征及其在年际尺度上与ENSO的关系研究

利用1976—2005年江苏省龙卷信息化资料和高分辨率再分析资料,对江苏省龙卷的发生特征以及ENSO事件对江苏省龙卷发生数的影响进行了分析。结果表明:(1)1976—2005年,江苏省龙卷发生数年际和年代际变化明显,空间分布不均匀:1990s龙卷发生数较多;盐城南部和南通沿海地区是龙卷较为多发的区域。(2)ENSO事件对江苏省龙卷的发生频率有重要影响:ENSO冷事件月份平均龙卷发生数多于暖事件月份;非ENSO事件月份平均龙卷发生数居中。(3)ENSO冷事件时西南低空急流发生频率明显增加,由于低空急流增强而引起的江苏省地区水汽供应、动力条件和不稳定能量的分布均有利于龙卷的发生,导致在ENSO冷事件情况下江苏省龙卷发生数偏多。     

宁德市东湖湿地鸟类资源调查与保护

2003年3月-2004年4月,在宁德三都湾东湖湿地及其周边地区进行了10次湿地鸟类资源连续调查。调查表明:宁德东湖湿地生物多样性丰富,特别是湿地水禽种类繁多,数量巨大,发现鸟类12目26科80种,计20119只。宁德东湖湿地是福建省鸟类资源的重要分布区,是各类水禽的理想栖息地、越冬地和迁徙地,但存在因开发建设湖面缩小、市区大量生活污水污染水质、湖体淤积、陆地化过快等问题。为此,保护和恢复东湖湿地、建立湿地公园已是势在必行。     

Post-depositional modification of NO-3 in snow layers at EastAntarctica and at the headwater of ürumqi River

Acidic species, such as Nitrate, in polar snow and firn layers are “reversibly” deposited, and are sufficiently volatile to undergo significant postdepositional exchange between snow/firn and the atmosphere. Through comparison of the snowpit and snowpack nitrate concentrations from central East Antarctica and the headwater of ürumqi River, we conclude that the nitrate peaks in the uppermost surface snow layers in central Antarctica are not related to an atmospheric signal and must account for post-depositional effects. Such effects, however, are not found in the surface snowpack nitrate profiles from the headwater of ürumqi River. Two reasons may account for the post-depositional difference. At first, nitrate in the polar snow and firn layers appears to be hydrated ion, which can be taken up by the atmosphere, while at the headwater of ürumqi River it seems mainly as mineral ion, which assembles the behavior of aerosol-derived species that are “irreversibly” deposited and do not undergo significant post-depositional exchange with the atmosphere. Secondly, the chemical features of the snow and ice on the Antarctica are mainly determined by wet deposition, to the contrary, dry deposition is more significant at the headwater of lUrumqi River than that on the East Antarctic Plateau.     

第二亚欧大陆桥的构成及其国际环境

本文将第二亚欧大陆桥描述为欧洲联盟网与中国东部网之间的连接,据此描绘了欧洲联盟网和中国东部网的构成,分析了亚洲、尤其是中亚地区围绕交通运输的国际合作形势和生态环境状况,阐述了泛欧洲交通与环境合作的内容和进程.     

东海区鲳鱼资源利用现状分析

通过对东海区鲳鱼近年群体组成变化及银鲳生物学特性变化来分析目前鲳鱼资源利用状况,结果表明：一方面,虽然近年鲳鱼产量大幅增加,但其平均体重、优势叉长组成及年龄组成均出现明显下降,资源状况日益恶化;另一方面,1龄鱼已占渔获的93．68％,目前捕捞现行点开捕年龄tc=1和捕捞死亡系数F＝2．51,单位补充量繁殖力相对百分比P＜1．9％,单位补充量渔获量(Yw／R)为70g／尾,均显示已处于严重的生物学型捕捞过度．建议渔业管理部门大力削减作业渔船约50％,严格控制捕捞强度,逐步推迟开捕年龄至3龄以上,使鲳鱼资源真正能够永续利用。     

两次区域性暴雨过程副高三维结构对比分析

为探讨夏季不同大气环流背景下区域性暴雨过程副高结构特征及其对降水的贡献,利用2005年6-7月降水量和NCEP／NCAR逐日再分析等资料,采用特征指数分析和物理量诊断方法,对比分析了2005年夏季两次区域性暴雨的副高三维结构特征。结果发现,夏季不同的大气环流背景下,两次区域性暴雨过程副高结构性质分别表现为热力性高压脊和动力性高压脊特征,从而导致两次暴雨过程的水汽供应条件和产生强烈上升运动的大尺度背景场存在差异。