学术动态

中国西部大陆深俯冲作用的探究”取得重要进展近日 ,科技部组织专家组对“国家重点基础研究发展规划”(“973计划”)项目“大陆深俯冲作用”及其二级课题进行了中期评估。由我校牵头的“中国西部大陆深俯冲作用的探究”课题受到专家组的一致好评。“国家重点基础研究发展规划”“大陆深俯冲作用”项目由 1 1个二级子课题组成 ,“中国西部大陆深俯冲作用的探究”是其中第 8个子课题。该课题由我校牵头与北京大学共同承担 ,课题负责人由我校孙勇教授和北京大学张立飞教授担任。该课题也是我校历史上承担的级别最高的“973计划”课题。经过课题组两年来的不懈努力 ,研究工作取得了重大进展 ,首次在中国西部的阿尔金和西天山等地发现了不同类型的超高压变质岩石 ,确定了柴北缘超高压变质岩石的存在 ,明确指出中国西部的阿尔金 -柴北缘和西南天山为继大别 -苏鲁之后又一个高压 -超高压变质地体。依据岩石学、矿物学和地球化学研究 ,指出阿尔金造山带的 3类超高压变质岩是大陆地壳深俯冲作用的产物 ,尤其是超高压中基性片麻岩的石榴石中单斜辉石和金红石出溶叶片的发现 ,表明大陆岩石俯冲到大于 1 50 km的地幔深度。建立了阿尔金 -柴北缘代表性超高压变质...     

柴北缘野马滩超高压地体的成因——年代学研究结果的约束

目的 探讨柴北缘野马滩超高压地体的成因.方法 利用锆石LA-ICP-MS原位微区分析技术,对超高压榴辉岩中两种类型的副片麻岩夹层进行年代学研究.结果 得到榴辉岩中两类副片麻岩夹层的变质年龄介于421～458 Ma之间,与超高压榴辉岩的变质年龄一致.结论 柴北缘野马滩超高压榴辉岩和围岩片麻岩是同一期变质事件的产物,其形成可能不应属于典型洋壳深俯冲成因,而很可能是陆壳深俯冲的结果.     

超高压变质作用及大陆深俯冲--地球科学前沿述评

目的总结和评述超高压变质及大陆深俯冲作用研究进展。方法文献阅读及专题研究。结果总结分析了超高压变质及大陆深俯冲作用的时空分布、俯冲深度极限、俯冲过程中流体的性状及作用,以及中国西部北秦岭、柴北缘和阿尔金超高压变质岩带的研究现状及特点。结论超高压变质岩石均形成于碰撞造山带中,时代以显生宙为主;大陆俯冲的深度有可能达到200 km以上的地幔深处;超高压变质过程中有流体的参与,但流体的活动局限在很小的范围内。     

2013-24 科技期刊亮点

花岗岩浆指示北秦岭早古生代大陆碰撞过程西北大学地质学系张成立等研究发现,北秦岭构造带存在与500Ma高压-超高压变质、450Ma中压麻粒岩相和420Ma角闪岩相退变质作用分别对应的3期花岗岩浆作用,指示北秦岭在早古生代期间经历了由大陆碰撞到碰撞后再造的演化历史。     

北秦岭罗汉寺岩群锆石年龄及地质意义

目的准确测定北秦岭罗汉寺岩群辉长岩脉的形成时代,探讨其地质意义。方法采用激光剥蚀等离子质谱法,对辉长岩中锆石进行U-Pb同位素定年。结果辉长岩形成年龄为475 Ma±4 Ma。结论罗汉寺辉长岩脉的形成时代与北秦岭两条高压—超高压变质带和富水杂岩成岩时代接近或一致,它的形成很可能与北秦岭早古生代岛弧体系碰撞有关。     

太行山-恒山太古代古老陆块: 年代学和地球化学制约

太行山-恒山-五台山变质地块的构造热演化和地质年代学研究,以及前寒武纪高压麻粒岩带、五台群金刚库组高压变质泥质岩的发现表明,可能存在太古代末到古元古代初东部陆块、西部陆块之间的碰撞造山带.太行山变质地块北段与恒山变质地块的地质学、地质年代学、构造热演化和地球化学资料对比反映这两个变质地块在华北地台形成演化早期应为同一构造单元,相当于东部陆块的西部活动陆缘.经历了东部、西部陆块碰撞作用而发生构造岩浆活动和变质作用的强烈改造.     

大别造山带北缘古生代构造-地层岩片的构造归属——岩石铅同位素组成提供的信息

大别造山带北缘(北淮阳)古生代各构造-地层岩片变火山岩、变沉积岩显示了具有高放射性和低放射性成因的两类铅同位素组成特征,块体效应明显,且具有一定的规律性.与秦岭造山带主要构造单元特征的铅同位素组成对比表明,定远组构造岩片可能是南秦岭构造单元或扬子陆块北缘的成分;龟山组、南湾组-佛子岭群、石炭系岩片则属于北秦岭构造单元,它们是北秦岭构造带的东延部分.结合地质体之间的分布关系判断,在大别造山带,扬子陆块与华北陆块在古生代的俯冲消减带应当位于南湾组-佛子岭群岩片的的北界或它们所覆盖地段之下的某个位置.     

吉林中部地区小绥河组变质粉砂岩碎屑锆石U-Pb年代学研究及其地质意义

对吉林省中部地区小绥河组变质粉砂岩进行了LA-ICP-MS碎屑锆石U-Pb年代学、地球化学及锆石Hf同位素的研究,探讨了变质粉砂岩的形成时代、物源及构造背景。通过U-Pb定年分析,获得小绥河组变质粉砂岩碎屑锆石3组U-Pb年龄:459～474Ma、441～446Ma和417～426Ma,其形成时代应为晚志留世—早泥盆世。通过全岩地球化学和锆石Hf同位素分析,认为小绥河组变质粉砂岩原岩物源主要来自于兴蒙造山带东段中奥陶世至早泥盆世的火成岩。小绥河组变质粉砂岩可能形成于弧陆碰撞的造山环境。     

柴北缘构造带泥盆纪构造属性研究

根据露头及钻井资料,依据沉积学理论,对柴达木盆地东北部泥盆系地层厚度、碎屑颗粒组成、锆石年龄、超覆关系和沉积体系展布等进行研究。结果表明:柴北缘地区(包括柴北缘构造带与欧龙布鲁克微板块)泥盆纪发育自南向北展布的沉积体系,碎屑物质来源于由多个前泥盆纪构造岩片组成的造山带;该阶段柴北缘构造带构造属性既不是前陆盆地也不是裂陷槽,而是由多个前泥盆纪构造岩片组成的造山带;该造山带隆升开始于距今约465 Ma,遭受剥蚀开始于距今约430 Ma,其隆升可能持续到晚石炭世甚至二叠纪早期,初步推断该造山带至少存在了190 Ma,包括距今465~430 Ma的山体隆升与距今430~275 Ma的山体剥蚀阶段。     

秦岭杂岩残存高压不纯大理岩的确定及其意义

陕西商南试马寨秦岭杂岩中不纯大理岩的岩相学和矿物化学研究表明,该岩石的变质矿物组合可明显分为两期Ⅰ.方解石+白云石+多硅白云母+石英+镁电气石+金红石+金云母;Ⅱ.方解石+低铁白云石+多硅白云母+石英+高岭石,另有少量斜长石.通过特征矿物组合和矿物成分对比,并利用方解石-白云石地质温压计及多硅白云母压力计,获得该岩石早期变质温压条件为700℃±和》1.0GPa,属高压变质岩石.它的确定,为进一步阐明秦岭造山带核部新元古代高压变质岩带的存在及其演化提供了新的资料.     

相互依赖、全球化与南北关系

在经济全球化条件下，南北国家之间的相互依赖，尤其是经济上的相互依赖日益加深，但两之间的相互依赖又是不对称，不平衡的，更多地表现为南方国家对北方国家单方面的依赖，随着冷战的结束以及全球化的深入发展，南北差距进一步扩大，南北之间的等级结构进一步凸显，南北矛盾也随着南方国家的日益贫困化和边缘化而有所激化，南北关系不容乐观。     

魏晋南北朝时期的比丘尼

魏晋南北朝时期，中国历史上第一批比丘尼诞生，当时出家为尼成为由子一种新的归宿。此时的比丘尼在政治、经济上享有许多特权，同时她们作为佛门弟子中的重要群体，对弘扬佛教外采文化、推动佛学的发展做出了突出的贡献。     

Progress in the stratigraphy and geochronology of the Shuidonggou site, Ningxia, North China

In the past years we carried out further stratigraphy division in field and it is found that rich stone artifacts can be found in fluvial-shallow lake-alluvial sediments on the terrace Ⅱ of Biangou River, inShuidonggou site, Ningxia and they are SDG1, 2 and 7. More luminescence and AMS ^14C dating in laboratory show that Paleolithic culture develops during the Upper Paleolithic period with ages of 35--20 ka. The Paleolithic culture of SDG 1 is a little earlier than that of SDG 2 similar to SDG 7. The sandy sediments on terrace Ⅱ of Biangou River deposits in the past 72--18 ka, corresponding to Last Glacial. SDG2 has a stable sedimentary environment, resulting in the continuous stratigraphy, thickest deposits and rich environment and culture information, which can be regarded as the important and classic paleoanthropological section of Late Pleistocene in this region.     

Geomorphic investigations in the Medves Area, North Hungary

The Medves Area lies close to the Hungarian-Slovak boundary in North Hungary. Having "horst-graben-type" geological structure it can be characterised by steeply emerging horst-like hills and between them narrow trenches and deeply dissected erosional valleys. The recent morphology of the Medves Area is determined by four main elements: the structure, the petrographic setting, the exo-genic processes and the anthropogenic effects. In spite of the domination of the Oligocene-Miocene sedimentary rocks great part of the area is covered by Pliocene basalts having either stratovolcanic structure or consisting of only lavas, forming lavaplateaus, small cones, dykes or necks. In spite of the strong denudation their original form dominates yet. The decrease of the sheet of the Medves Plateau was considerable only on the rims by parallel retreat. In the southern part of the Medves Area the evolution of the landscape was determined mainly by exogenic processes. The great density of the valleys is very significant, but it is interesting that many tributary valleys are dry valleys, which can be explained by neotectonic movements and young captures. Anthropogenic forms are very frequent in the Medves Area, where the change of the natural environment caused by human activity is above average. Especially the landscape forming effects of the mining of basalt and browncoal and that of the related industry and infrastructure changed the surface. Very interesting are the depressions on the surface caused by collapse of underground galleries, moreover sometimes trench-like deep fissures came into being.     

藏北火车头山新生代火山岩的岩石特征与时代

火车头山地区的新生代火山岩位于藏北火山岩带的中段,火山岩主要以熔岩被、平顶山、火山锥的形式产出,熔岩厚约20 ～300 m.对其矿物组合、矿物化学和岩石化学的研究表明,为一套强碱性的碱玄岩-响岩组合.根据火山岩的接触关系、K-Ar和40Ar/39Ar同位素年龄测定结果,可分为三期.第Ⅰ期(年龄为34～32 Ma)火山喷发较弱,形成小范围分布的白榴碧玄岩;第Ⅱ期(年龄为29～26 Ma)火山喷溢最为强烈,形成大面积厚层白榴石响岩、响岩质碱玄岩和粗斑状霞石响岩;第Ⅲ期(年龄为24～19 Ma)火山喷发较弱,岩性为白榴碱玄岩和白榴碱玄质响岩.     

楚辞、汉赋与北南文化交流

中华民族有着悠久的历史、灿烂的文化,中华文化有着多种源头、多层蕴涵,栖息于中华大地上的各民族先民,在各自具有独特规律的进程中,又在相互交流、吸收中,共同建构了中华民族博大精深的古老文化,共同创造了五彩缤纷的古典文学。特别引人注目的是,黄河流域中原文明领先发展,一旦与周边少数民族富于活力的文化发生碰撞、结合,往往会产生巨大的能量,推动中国文学出现崭新的景观。文章仅以黄河流域华夏文化与南方民族文化交流现象突出的楚辞、汉赋为例来谈一谈。     

Petrology, geochemistry and geodynamics of basic granulite from the Altay area, North Xinjiang, China

The basic granulite of the Altay orogenic belt occurs as tectonic lens in the Devonian medium- to lower-grade metamorphic beds through fault contact. The Altay granulite (AG) is an amphibole plagioclase two-pyroxene granulite and is mainly composed of two pyroxenes, plagioclase, amphibole and biotite. Its melano-minerals are rich in Mg/(Mg Fe^2 ),and its amphibole and biotite are rich in TiO2. The AG is rich in Mg/(Mg Fe^2 ), Al2O3 and depletion of U, Th and Rbcontents. The AG has moderate ∑REE and LREE-enriched with weak positive Eu anomaly. The AG shows island-arc pattern with negative Nb, P and Ti anomalies, reflecting that formation of the AG may be associated with subduction. Geochemical and mineral composition data reflect that the protolith of the AG is calc-alkaline basalt and formed by granulite facies metamorphism having peak P-T conditions of 750℃-780℃ and 0.6-0.7 Gpa. The AG formation underwent two stages was suggested. In the early stage of oceanic crustal subduction, calc-alkaline basalt with island-arc environment underwent granulite facies metamorphism to form the AG in deep crust, and in the late stage, the AG was thrust into the upper crust.     

山西省的鞘藻属植物

对山西省的鞘藻属植物进行了鉴定,共得该属植物１４种２变种,其中８种２变种为山西省新记录。     

Mid-Holocene climate change in North China, and the effect on cultural development

In this study, to reconstruct the paleoclimatic history, pollen and oxygen isotope were analyzed on the 160 samples of a 2.7 m peat core from Taishizhuang, Huailai County, Hebei Province. Combining our data with other information of climate history and archaeology from this area, we found that there is a close linkage between cultural development and the mid-Holocene (6000-3000 cal. aBP) environment changes. The main results and conclusions are presented as the following: The climate during 5678-5400 cal. aBP was unstable and in general colder and drier than today. From 5400 to 4800 cal. aBP the climate was much warmer and wetter than before. The climate during 4800-4300 cal. aBP was persistently cold, with an exceptional cold event occurring at 4600-4300 cal. aBP. This cold event was recorded at several other localities in Northern China even the Northern Hemisphere and played an important role in the cultural development. After the cold event, there was a return to warmer conditions between 4200 and 3300 cal.aBP.