湖北恩施三岔口二叠系-三叠系界线附近黏土岩锆石U-Pb年龄及地质意义

通过对恩施地区二叠系-三叠系界线附近含凝灰质黏土岩的野外地质学特征调查,采用锆石U-Pb同位素测试分析,取得其206Pb/238 U加权平均年龄为251.6±1.2Ma,该年龄值为二叠系-三叠系界线附近的火山喷发事件的年龄。结合碳和氧同位素分析,二叠系-三叠系界线附近黏土层之上碳同位素明显负偏,这与该时期生物绝灭事件关系密切。通过区域对比,发现该套黏土岩在区域上可进行连续追踪,不同地区界线附近岩石组合差异性明显,二叠系顶部自西向东总体表现为碳酸盐岩比例逐渐减少、碳硅质岩逐渐增加的特征。     

牙形石SHRIMP微区原位氧同位素分析方法

氧同位素温度计已被用于古温度变化研究多年。生物化石磷酸盐中的氧同位素组成对古气候环境变化响应灵敏,牙形石在古生代到中生代的古海洋地层中广泛存在,并具有较为重要的地层学意义,是研究古温度变化的最佳样品之一。SHRIMP具备高分辨、高灵敏、高精度和微量及原位微区分析的特点,可以进行20μm范围内的原位(in-situ)同位素分析。本文介绍了作者利用SHRIMP IIe-MC建立的牙形石微区原位氧同位素分析方法,这是国内关于该方法的首次报导。本文对磷灰石标准样Durango进行了测定,连续七昼夜获得的253次测定结果,平均值为δ18 Oapatite=9.78‰±0.29‰,与该标准参考值δ18 Oapatite=9.81‰±0.25‰(Williams,未刊资料)一致。作者并以二叠系—三叠系界线上下海水温度变化研究为示范,对采自西藏文布当桑二叠系—三叠系剖面上的49个层位中的237件牙形石样品进行了914个氧同位素分析,为研究二叠系—三叠系界线上发生的生物灭绝事件前后的海水温度变化提供了可靠详实的数据。     

黔西滇东地区二叠纪-三叠纪之交有机碳同位素和生物地层对比

二叠纪-三叠纪之交海、陆相地层对比研究对陆相二叠系-三叠系界线的定义以及全面认识该全球性重大生物与环境突变事件具有重要意义,是当前国际古生物学与地层学研究的重点和难点.选择贵州六盘水仲河二叠系-三叠系界线剖面为研究对象,系统研究了该剖面的化石面貌和有机碳同位素演变特征.结合黔西滇东地区二叠纪-三叠纪之交良好的陆相、海陆过渡相和浅海碎屑岩相地层记录,初步搭建了海、陆相生物地层与有机碳同位素地层对比框架.值得关注的是,综合已有研究的陆相和海陆过渡相剖面植物有机碳同位素和海相剖面无机碳同位素数据,发现均存在相同的碳同位素演变特征,且与生物地层对比方案一致.据此,认为高分辨率的有机碳同位素化学地层是实现海-陆相地层对比的有效手段之一.      

四川盆地东部开江-梁平海槽东西两侧三叠系飞仙关组碳酸盐岩碳氧同位素组成对比及古海洋学意义

海相碳酸盐岩的碳氧同位素组成具有显著的古海洋学意义,其组成具有随时间变化的长期趋势,但不同沉积环境中古海水碳氧同位素组成的异同仍存在争议并需要进一步深入研究。本文测试了四川盆地东部开江-梁平海槽东侧孤立台地内的四川宣汉渡口剖面飞仙关组及相邻地层133件海相碳酸盐岩样品的碳氧同位素组成,对比研究了海槽西侧作为镶边陆棚沉积的华蓥/邻水仰天窝剖面对应地层样品的碳氧同位素组成。研究表明,孤立碳酸盐台地和镶边陆棚飞仙关组具有非常类似的碳同位素组成和演化趋势,并与对应时间全球海水碳同位素演化趋势一致,显示全球事件是海水碳同位素组成的主要控制因素。然而,开江-梁平海槽东侧孤立碳酸盐台地和西侧镶边陆棚飞仙关组的氧同位素组成并不完全一致,存在如下共性和个性:(1)两种台地类型飞仙关组的氧同位素组成都显示出类似的变化样式,即从二叠-三叠纪界线附近δ~(18)O的低值演化至其余时间相对稳定的氧同位素组成,曲线主体氧同位素组成也具有类似的变化幅度;(2)两种台地类型飞仙关组底部地层中都检测到氧同位素组成非常低的样品,它们可能不完全是成岩蚀变的结果,如可能与界线附近广泛的热事件有关,但仍需要数据的进一步积累以及更多剖面高分辨率年代框架内氧同位素的对比研究;(3)孤立台地内碳酸盐岩δ~(18)O显著低于镶边陆棚,差值达到1‰左右,由此换算的古海水温度差值大致在4℃左右,显示孤立台地内部具有更高的碳酸盐形成温度;(4)孤立台地存在一些氧同位素组成较正、且显著偏离演化曲线主体的样品,其高δ~(18)O值的原因除白云石-水和方解石-水具有不同的氧同位素分馏系数以外,同时还反映海槽东侧孤立台地内部飞仙关组沉积时海水具有较高的盐度。开江-梁平海槽东西两侧氧同位素组成的差别表明东侧孤立碳酸盐台地内海水比西侧镶边陆棚内具有更高的温度和盐度,海水循环更受限制,台内海水更具有白云石化作用的潜力,这不仅造成东侧台地内飞仙关组发育更多的与萨布哈模式有关的准同生白云岩,还会通过回流作用或台内热对流作用造成台地边缘滩相颗粒岩的白云石化,这使得开江-梁平海槽东侧的滩相颗粒岩更可能成为质量较好的颗粒白云岩储层。     

广西东攀P-T界线深水相剖面与煤山剖面地层学对比

从放射虫生物地层学、黏土矿物事件地层学和有机碳同位素地层学方面对广西柳桥地区东攀二叠系-三叠系深水相剖面进行了研究,并与浙江煤山剖面(GSSP)同期地层进行了对比.结果表明,东攀剖面上二叠系-三叠系界线处与煤山剖面具有较好的可比性:①东攀剖面放射虫A.yaoi带可以与煤山剖面的Clarkina changxingensis-C.postwangi-C.postsubcarinata-C.deflecta组合带对比;②两剖面都具有性质相似、延伸稳定的界线黏土岩;③在两剖面界线黏土岩中,有机碳同位素组成都发生了巨减.     

扬子地区典型剖面二叠系不同沉积相地球化学特征

对扬子地区2个典型剖面即四川广元上寺剖面和贵州罗甸纳水剖面二叠系系统采样,在沉积相研究的基础上,对华南二叠系碳酸盐岩地层不同沉积相地球化学特征进行了分析。研究表明:Co、Ba、V、Rb等具有指相意义的元素,在越靠近深水环境,Co、Ba、V、Rb平均丰度越高,而w(Sr)/w(Ba)值从开阔台地相到盆地相整体有降低趋势。贵州罗甸纳水剖面为斜坡沉积背景的典型剖面,从台地前斜坡相→陆棚相→斜坡相→盆地相,w(ΣREE)值逐渐增大,且各相带稀土元素配分模式存在明显的Ce异常。四川广元上寺剖面二叠系浅海陆棚相下部和盆地相地层中平均残余有机碳丰度大于1.5%,说明这2个沉积相带可能为该地区优质烃源岩发育相带,该剖面二叠系显示从开阔台地相到盆地相具有有机质逐渐富集的特点。     

江西东岭剖面P-T界线碳同位素变化与沉积物输入的关系

二叠纪末期发生了显生宙以来规模最大的生物灭绝事件,利用江西修水东岭剖面二叠-三叠系界线的碳同位素、主量元素及微量元素分别研究全球碳循环的变化及其相对应的物源的变化进而分析环境变化与生物灭绝的关系。研究结果表明,东岭剖面二叠-三叠系界线存在阶梯式碳同位素负偏,第一阶段阶梯式负偏幅度为2‰,第二阶段阶梯式负偏幅度为2.5‰,总的负偏幅度高达4.5‰。在阶段阶梯式碳同位素负偏过程,碳酸盐岩中的硅酸盐组分物源由基性火成岩转变为岛弧性质的酸性火成岩。后者可能与我国华南周围岛弧火山喷发有关。这些碳同位素负偏在时间上与物源的转变及火山灰层基本一致,推测其与我国华南岛弧火山及西伯利亚大火成岩省喷发有关。大规模火山作用喷出或诱发出的二氧化碳及甲烷温室气体有可能是造成二叠-三叠系阶梯式碳同位素负偏的主要原因。火山喷发造成的环境恶化如全球变暖、海洋缺氧、海洋酸化、植被破坏形成的大量沉积物输入海洋致使生物生存压力增大,从而造成二叠末期生物的大灭绝。     

徐州地区下古生界碳酸盐岩的碳、氧同位素研究

在已有的对徐州地区下古生界碳酸盐岩详细岩石学研究基础上，系统测试了碳酸盐岩方解石和白云石的碳、氧同位素组成特征；地球化学和岩石学研究相结合，综合提取了碳酸盐岩碳、氧同位素组成的沉积、成岩地质信息；初步探讨了同位素组成的地层变化及其意义。研究结果表明：碳酸盐岩碳同位素组成特征可以指示沉积环境及其演化，开阔陆表海、灰质障壁砂坝、局限陆表海、潮下带、潮渠、藻坪诸沉积相间碳酸盐岩的δ^13C值表现出规律性变化，碳同位素组成变化曲线上的显著正偏移与海侵有关；碳酸盐岩氧同位素组成对成岩环境及其演化有明显响应，淡水成岩环境、潮上成岩环境、潮间成岩环境、潮下成岩环境和埋藏成岩环境具有不同的碳酸盐岩氧同位素组成特征；徐州地区大北望寒武系剖面地层界线附近都有碳、氧同位素组成变化的特征显示，研究工作证实了徐州地区下古生界同位素地层划分的可行性。     

北京西山地区下苇甸剖面寒武系碳酸盐岩碳氧同位素研究

北京西山下苇甸剖面寒武系的碳酸盐岩发育良好且连续,在岩石学和地层学研究基础上,通过实测剖面和碳酸盐岩碳氧同位素,探讨了下苇甸地区寒武纪海洋环境及沉积相演变。研究表明,下苇甸寒武系发育碳酸盐岩镶边台地相沉积,自底部昌平组至顶部凤山组依次发育潮坪、潟湖、障壁岛礁滩、滩外斜坡沉积相。碳酸盐岩氧同位素表明该区域寒武纪为温暖至炎热的亚热带气候,同时对古沉积环境也有明显响应,沉积环境的盐度自潮上带至滩外斜坡逐渐减低至正常海水的水平,碳同位素与下苇甸沉积相及沉积旋回的变化契合度良好,表明寒武系整体为一个大的海侵过程,晚期凤山组沉积期海平面略下降。     

陕西岐山蓟县系碳氧同位素特征及其古环境意义

陕西岐山二郎沟蓟县系剖面位于华北克拉通南缘,发育一套浅海相碳酸盐岩,自下而上出露龙家园组和巡检司组。两个岩组共采集、测试了碳、氧同位素样品184件,结果显示δ13 C值落在-1.747‰～1.144‰之间,总体上较稳定,平均值为-0.523‰;δ~(18)O值整体在-8.662‰～-2.540‰之间,大部分落在-5.5‰至-3‰,平均值为-4.469‰,低幅高频振荡。碳同位素旋回性较明显,可以进一步划分出4个旋回。碳、氧同位素曲线与燕山地区蓟县系已有研究结果相似性较高,其中,巡检司组近顶部出现的约为2‰的负偏事件,可大致对应于蓟县剖面雾迷山组顶部至洪水庄组的负偏事件。碳同位素的升降趋势及藻类数量(叠层石)丰度变化表明当时海平面在不断变化。此外,二郎沟剖面研究结果还与俄罗斯南乌拉尔阿孜瓦尔组以及加拿大霍恩比湾群的碳、氧同位素曲线也颇为相近,符合全球中元古代碳同位素组成特别稳定的特征,是对全球统一的古海洋背景的响应。     

Unity of the national and the international in the socio-cultural development of the peoples of the USSR

International unity is becoming ever stronger in this country owing to an increasing similarity in the development of the cultural environment. This comprises the provision of all the country's republics with a sufficient number of schools, theatres, and other institutions and cultural information media in accordance with the needs of the population. An important part is played by the rise in ‘the general educational level, as well as the level of professional qualifications and skills. Among all the Soviet nations and nationalities, this rise being more rapid among formerly backward peoples. Prominent among the factors of internationalization is the progressive development of the nationalities’ cultural resources, while professional culture is being increasingly brought within the reach of the masses.The implementation of the nationalities policy promotes the all-round development of all Soviet nations and nationalities, their drawing together, the upsurge of the individual capabilities of every Soviet citizen.     

Global repeating events in the history of the Earth and the motion of the Sun in the Galaxy

Chronological analyses of correlations between certain global repeating events (mass extinctions of marine organisms, meteorite impacts, and flashes in the frequency of geomagnetic reversals) during the Phanerozoic Eon and the motion of the solar system in the Galaxy are presented for five rotationally symmetrical models for the regular Galactic gravitational field. Thirteen of sixteen mass-extinction events can be described by a repetition interval of 183±3 million years. This is in agreement with the anomalistic period (interval between two subsequent passages of the Sun through the apocenter of its Galactic orbit) in the model of Allen and Martos. The positions of the minima and maxima in Gaussian functions approximating the frequency distribution for geomagnetic reversals also agree with the times of passage of the Sun through the apocenter and pericenter, respectively, of its Galactic orbit in this model. The maximum in the distribution of the deviations of the dates of mass extinctions from the nearest dates of impacts of large, crater-forming bodies is close to zero, providing evidence that many such events are correlated. As a rule, extinctions follow impact events. The impacts of large bodies have occurred most often when the solar system passes through the Galactic plane, while mass extinctions occur more often at some distance from the Galactic plane (about 40 pc). As a rule, intervals of increases in the frequency of geomagnetic reversals coincide with dates of impacts of large bodies. At the same time, these intervals do not show a clear correlation with the dates of mass extinctions. The intensity of mass extinctions, like the energy released by impacts, is consistently higher in periods when the Sun is moving from the apocenter toward the pericenter of its orbit, than when it is moving from the pericenter toward the apocenter. Thus, there is evidence for a variety of relationships between repeating global events in the Phanerozoic and the motion of the Sun in the Galaxy. Long-period variations in the frequency of geomagnetic reversals are correlated with the orbital motion of the Sun, and increases in the frequency of geomagnetic reversals are correlated with impacts. Mass extinctions are correlated with the impacts of large bodies, whose motions may have been perturbed by clouds of interstellar material concentrated toward the Galactic plane and by the shock front associated with the Perseus spiral arm, through which the solar system passes. The velocity of the Sun relative to the spiral pattern is estimated.     

Deviation of the major axis of the inertia ellipsoid of the Moon from the direction toward the Earth

It is known from observations that the center of mass of the Moon does not coincide with the geometric center of its figure, and the line connecting these two centers is not aligned with the direction toward the center of the Earth, instead deviating toward the Southeast. This stationary deviation of the axis of the inertia ellipsoid of the Moon to the South of the direction toward the Earth is analyzed. A system of five linear differential equations describing the physical libration of the Moon in latitude is considered, and these equations are derived using a new vector method taking into account perturbations from the Earth and partly from the Sun. The characteristic equation of this system is obtained, and all five oscillation frequencies are found. Special attention is paid to the fifth (zero) frequency, for which the solution of the latitude libration equations are stationary and represents a previously unknown additional motion of the rotational axis of theMoon in a cone with a small opening angle. In contrast to the astronomical precession of the Earth, the rotation of the angular-velocity vector is in the positive direction (counter-clockwise), with the period T ₃ = 27.32 days. On this basis, this phenomenon has been named “quasi-precession.” This quasi-precession leads to a stationary inclination of the major axis of the inertia ellipsoid of theMoon to the South (for an observer on Earth), making it possible to explain one component of the observed deviation of the center of mass of the Moon from the direction toward the Earth. The opening angle of the quasiprecession cone is approximately 0.834″.     

从榴辉岩与围岩的关系论苏鲁榴辉岩的形成与折返

位于华北和扬子两板块碰撞带中的苏鲁榴辉岩形成的温压条件不但是超高压，而且是高温。榴辉岩的PTt轨迹表明其为陆-陆磁撞俯冲带的产物。榴辉岩的区域性围岩花岗质片麻岩为新元古代同碰撞期花岗岩，榴辉岩及其他直接围岩皆呈包体存在于其中，并见新元古代花岗岩呈脉状侵入榴辉岩包体中。区域性围岩新元古代花岗岩的锆石中发现有柯石英、绿辉石等包裹体，表明新元古代花岗岩的组成物质也经受过超高压变质作用，且榴辉岩与围岩新元古代花岗岩的锆石U-Pb体系同位素年龄基本相同。但新元古代花岗岩所记录的变质作用和变形作用期次（或阶段）却少于榴辉岩。椐上述可得如下推断：超高压榴辉岩与新元古代花岗岩岩浆是同时在碰撞带底部（俯冲板块前部）形成的；榴辉岩的第一折返阶段是由新元古代花岗岩岩浆携带上升的，其第二折返阶段是和新元古代花岗岩一起由逆冲及区域性隆起而上升，遭受剥蚀。     

某高速公路下伏煤矿采空区稳定性分析

在论述某高速公路下伏砦脖煤矿采空区地质、采矿和工程地质特征的基础上, 进行了稳定性数值模拟分析, 定性与定量地分析与评价了该煤矿采空区的地表变形特征及稳定性。研究结果表明: 该煤矿采空区的变形尚未完成, 对拟建的高速公路将产生很大的危害, 必须采取相应的工程治理措施。      

摩擦桩基桩土间极限摩阻力取值问题探讨

通过对广珠东线高速公路横沥大桥的试桩及土体的工程地质条件分析,总结出影响摩擦桩基桩土间极限摩阻力取值的一般问题以及解决问题的方法和措施。     

Paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic

We first re-examined the apparent polar wander curves for stable Eurasia and Africa since the Triassic. These curves were then combined together with curves of North and South America according to the kinematics of the Atlantic ocean and a synthetic polar wander curve was given. Then, most of the paleomagnetic results from the Tethys mobile belt, from the Atlantic to the Pamirs, were analysed.Several groups of plates, microplates and blocks can be seen. First, relatively stable regions like Maghreb and Sicily, which have not moved much. Then we have a group formed by Iberia, Sardinia, Italy and, to a lesser extent, Corsica and the Western and Central Alps. For these blocks, movements are anticlockwise rotations chiefly driven by the anticlockwise rotation of Africa, but they are sometimes stronger.To the east, a major change takes place. The north of the Aegean Sea and the Ionian zone are clockwise rotated and these rotations are recent: Oligocene-Miocene for the first part, Pliocene to the present for the second part.A major problem arises in Turkey, Caucasus and Iran. Paleomagnetic results indicate a position far to the south of Eurasia, and, at the same time, geological evidence is in favour of a position close to Eurasia. We discuss these discrepancies.     

On the consistency of proposed models for the Pyrenees with the structure of the eastern parts of the belt

The structure of the eastern Pyrenees consists mainly of south-directed thrusts involving basement and cover rocks. An antiformal stack developed by the piling up of basement thrust sheets which outcrop in the Axial zone. These structures account for a thin-skinned thrust model rather than a vertical fault model in which the Axial zone would be essentially autochthonous, and the North-Pyrenean fault the axial plane of a fan thrust system. New data from the Eastern Pyrenees and the thin-skinned model suggest that(1) the structure east of the Pedraforca nappe is similar to that of the Central Pyrenees; (2) the cover rocks of the South-Pyrenean units and of the Axial zone-after restoration—built up a northwards-thickening prism consistent with the existence of a unique Pyrenean sedimentary basin during Mesozoic time; (3) the Axial zone is only a complex antiformal stack developed as a part of South-Pyrenean system related to the Paleogene thrusting-tectonics. The Axial zone palaeogeographic area had no special meaning during Mesozoic time.