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1.
皖苏鲁新生代玄武岩的Sr-Nd 同位素组成及其含义   总被引:2,自引:0,他引:2  
皖苏鲁新生代碱性玄武岩34个样品的Sr、Nd同位素组成,总的变化范围为ε°CHUR(Nd)=-4.5-6.9,ε°CHUR(Sr)=-20.4-33.1。分布在大洋玄武岩的Sr-Nd同位素组成范围内。其中江苏省六合一仪征、山东省蓬莱、栖霞和临朐等地区玄武岩同位素组成与PREMA型地幔端元相似,皖东嘉山-来安地区玄武岩具有EMI型地幔端元特征。前者来源于软流圈或更深部的地幔部分,后者来源于不均一的岩石圈地幔部分。来源于较流圈和岩石圈地幔的熔体互相作用决定了皖苏鲁新生代玄武岩 Sr-Nd 同位素地球化学特征。  相似文献   

2.
所研究的玄武岩包括拉斑玄武岩、碱性玄武岩、苦橄粗玄岩和钾质玄武岩。主元素和微量元素的组成变化表明,中国东部玄武岩既是不同深度地幔部分熔融的产物,又经历了岩浆结晶分层作用。强不相容元素比值的变化特征显然与岩石圈地幔交代作用有关。软流圈地幔的上涌并导致上覆不均一的岩石圈地幔的部分熔融是形成中国东部新生代玄武岩的主要机制。  相似文献   

3.
所研究的玄武岩包括拉斑玄武岩、碱性玄武岩、苦橄粗玄岩和钾质玄武岩。主元素和微量元素的组成变化表明,中国东部玄武岩既是不同深度地幔部分熔融的产物,又经历了岩浆结晶分异作用。强不相容元素比值的变化特征显然与岩石圈地幔交代作用有关。软流圈地幔的上涌并导致上覆不均一的岩石圈地幔的部分熔融是形成中国东部新生代玄武岩的主要机制。  相似文献   

4.
阿哲格尔火山湖玄武岩是位于卡帕多利亚火成岩省(CVP)东部的第四纪火山岩之一。与CVP中其他火山岩相比,玄武岩具有演化程度较低,成分上更接近原始岩浆的特征。玄武岩记录了两期深部岩浆活动:橄榄石捕掳晶Fo值高达89,尖晶石包裹体具有低Cr~#、高Al的特征,表明了早期岩浆源区可能为受俯冲板片流体交代的岩石圈地幔;除样品TCA02外,玄武岩ΣCe/ΣY比值为1.39~2.11,~(143)Nd/~(144)Nd比值为0.51287~0.51288,Th/Nb比值为0.15~0.16,具有大陆裂谷玄武岩的特征,反应了晚期的碱性岩浆起源于软流圈地幔。与CVP早-中更新世钙碱性岩浆相对比,晚期碱性岩浆的高场强元素(如Nb、Ta)具有弱的负异常,K、Ba等大离子亲石元素富集程度较低,揭示了岩浆在上升演化过程中存在富集交代的岩石圈地幔物质的加入。  相似文献   

5.
报道了大兴安岭-太行山重力梯度带以西河北阳原和山西大同新生代玄武岩的元素和 Sr- Nd同位素地球化学数据.含幔源包体的阳原早第三纪碱性玄武岩具有均一的 Sr- Nd同位素组成(ε Nd≈ 5.7)和相似于 OIB的微量元素特征,玄武岩主要来自软流圈地幔,岩浆起源较深.大同地区第四纪时期同时产出碱性和拉斑玄武岩 , 碱性玄武岩也主要来自软流圈地幔,岩浆起源深度小于阳原样品 ; 拉斑玄武岩具有较低的ε Nd( 1~ 4),可能是软流圈和岩石圈地幔相互作用的产物,岩浆起源较浅.大同两类玄武岩在空间上分野明显,可能与桑干河断裂对软流圈地幔上涌的控制以及区域上岩石圈-软流圈作用程度的变化有关.  相似文献   

6.
内蒙古集宁玄武岩区位于华北克拉通北缘,东邻汉诺坝玄武岩区。由亚碱性的拉斑玄武岩及碱性的橄榄玄武岩、碧玄岩和碱玄岩组成。玄武岩的SiO2与TiO2含量分别为44.10~52.27wt.%和1.57~2.95wt.%,Mg^#(43—63)及Ni含量(27~210ppm)变化范围较大。集宁玄武岩的微量元素原始地幔标准化曲线及REE球粒陨石标准化曲线与OIB相似,Sr、Nd同位素比值显示了较汉诺坝玄武岩富集的特征。研究表明,虽然集宁玄武岩浆经历了一定程度的橄榄石、单斜辉石的分离结晶作用,但微量元素及Sr、Nd、Ph同位素特征排除了幔源岩浆在喷发到地表过程中受到地壳物质显著混染的可能性。^143Nd/^144 Nd ^87Sr/^86Sr vs.^206Ph/^204Pb的线性相关性表明,集宁玄武岩至少来自两个地幔端元组分:EMI和PREMA,且端元组分与汉诺坝玄武岩相似。尖晶石二辉橄榄岩的低程度部分熔融(2~5%)熔体与石榴石二辉橄榄岩更低程度部分熔融(〈2%)熔体的混合,可以解释集宁玄武岩稀土元素的变化特征。推测EMI位于岩石圈地幔之内且源区深度〈70km,PREMA则来自软流圈地幔。集宁碱性玄武岩与亚碱性玄武岩之间的地球化学差异,可能只是来自岩石圈地幔的EMI型熔体和来自软流圈地幔的PREMA型熔体在形成玄武岩浆时参与混合的比例不同,暗示该地区的岩石圈地幔与软流圈地幔之间经历了强烈的相互作用。集宁玄武岩与汉诺坝玄武岩相似的Sr、Nd、Pb同位素比值及相关性,说明它们具有相似的地幔源区,汉诺坝玄武岩的地球化学差异同样可以用EMI与PREMA组分对岩浆贡献程度的不同来解释。  相似文献   

7.
采用全岩K-Ar法获得山东省胶莱盆地诸城玄武岩的形成年龄为76M,胶州玄武岩的形成年龄为72Ma,代表了发生在晚白垩世的地幔岩浆事件,但两地岩浆产物具有不同的地球化学性质。诸城玄武岩主要为粗面玄武岩,富集轻稀土元素(LREE),微量元素组成类似于洋岛玄武岩(OIB),(^87Sr/^86Sr)t=0.7060-0.7080,εNd(t)=-3.0--5.1,介于洋岛玄武岩和中生代富集的岩石圈地幔之间,表明软流圈来源的岩浆中混入了富集岩石圈地幔来源的岩浆,是软流圈地幔与岩石圈地幔相互作用的结果。胶州玄武岩主要为碱性玄武岩,比诸城玄武岩更富集轻稀土元素,微量元素组成类似于诸城玄武岩,但Nb、Ta、Ti等高场强元素不显示亏损,Sr-Nd同位素组成也存在明显差别,(^87Sr/^86Sr)t=0、70350-0.70355,εNd(t)=5.4-5.8,与山东省新生代火山岩的地球化学特征类似,类似于洋岛玄武岩(OIB),表明岩浆起源于亏损的软流圈地幔。研究显示出晚白垩世以来胶莱盆地软流圈地幔不均匀上涌和逐渐成为玄武岩浆主要源区的趋势。  相似文献   

8.
吉林省伊通火山群位于郯庐断裂带北部的伊舒地锈内,根据前人的研究工作,该火山群岩石为中新世时来源于软流圈的碱性系列玄武岩[1,2].同时,该火山群含有大量的橄榄岩捕虏体,为深入研究东北地区新生代岩石圈地幔的性质、成凶与演化提供了难得的机会.  相似文献   

9.
湘东北中生代基性岩脉微量元素地球化学特征及岩石成因   总被引:7,自引:0,他引:7  
湘东北中生代基性岩脉可以分为煌斑岩和辉绿岩两类,前者形成于136.61Ma,后者形成于86.18Ma,与华南中生代主要拉张时期相对应。岩石富集LREE,Eu负异常不明显,其形成主要受地幔部分熔融作用制约。早期煌斑岩类微量元素和Sr、Nd同位素总体上具有富集地幔(EMⅡ型)洋岛玄武岩(OIB)特征,富集Nd、P、Cs,而K、Rb、Sr、U、Th等富集程度不明显,Ta、Nb略有富集,具有软流圈地幔上涌地幔热柱玄武岩岩浆源区性质,表现出软流圈地幔上涌部分熔融的成岩特点。晚期辉绿岩类表现出Ta、Nb、Ti亏损,但LILE并不富集,反映地壳混染程度的增强,具有大陆拉张带(裂谷初期)形成的玄武岩岩浆源区性质,为岩石圈地幔部分熔融形成。二者具有不同的岩浆源区性质,从早期到晚期岩浆源区向上迁移并致使部分陆 物质混入,反映由热点式拉张到岩石圈伸展-减薄的作用过程。  相似文献   

10.
樊祺诚  孙谦  隋建立  李霓 《岩石学报》2008,24(6):1323-1332
本文在北部湾内一对姊妹火山岛即涠洲岛及斜阳岛火山地质研究基础上,进一步开展火山岩微量元素和Sr-Nd-Pb同位素,以及地幔橄榄岩Re-Os同位素地球化学研究.岛上早晚两期火山岩均为碱性玄武岩,分别属于碱性橄榄玄武岩和碧玄岩.碧玄岩为玻基斑状结构,舍地幔橄榄岩碎块(一般<1cm),表明为地幔岩浆快速喷出地表冷凝而成,岩浆上升过程中极少演化.火山岩微量元素和Sr-Nd-Pb同位素资料表明,涠洲岛及斜阳岛玄武岩与雷琼及北部湾周边、南海海盆玄武岩类似,具有亏损地幔的Sr、Nd同位素组成与Pb同位素显示的EMII富集地幔特征的Dupal异常,表明岩浆并非来自单一地幔源区,不可与OIB或MORB源区简单类比,也非地幔柱成因,而是由两个不同的地球化学组分混合而成.Re-OS同位素特征也指示地幔橄榄岩捕虏体来源于亏损的岩石圈地幔,而非核幔边界.推测涠洲岛及斜阳岛与雷琼及北部湾周边的岩浆可能是由于南海扩张后大陆裂解-软流圈地幔热物质上涌,与上覆薄而年轻的岩石圈地幔相互作用的产物.  相似文献   

11.
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.  相似文献   

12.
13.
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″.  相似文献   

14.
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.  相似文献   

15.
从榴辉岩与围岩的关系论苏鲁榴辉岩的形成与折返   总被引:4,自引:1,他引:4       下载免费PDF全文
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。  相似文献   

16.
某高速公路下伏煤矿采空区稳定性分析   总被引:10,自引:0,他引:10  
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。   相似文献   

17.
18.
摩擦桩基桩土间极限摩阻力取值问题探讨   总被引:1,自引:0,他引:1  
陈银生 《世界地质》1999,18(1):54-59
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。  相似文献   

19.
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.  相似文献   

20.
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.  相似文献   

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