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南海北部边缘新生代玄武岩广泛分布，分布于海南岛北部的全新世早期石山组玄武岩，岩石组成为碱性橄榄玄武岩，其中可见较大颗粒的橄榄石斑晶，橄榄石斑晶具有较高的Fo值（82. 8～83. 5）和Ni含量（0. 14%～0. 20%）。橄榄玄武岩的微量元素及同位素组成与洋岛玄武岩（OIB）高度吻合，富集大离子亲石元素Rb、Ba和轻稀土元素，同时富集高场强元素Nb、Ta、Zr和Hf。矿物组成及主微量元素特征指示其源区为含石榴子石辉石岩源区，经历了较低程度的部分熔融（约5%）。此外，石山组橄榄玄武岩具有基本一致的Sr- Nd- Pb同位素组成，表明岩浆在上升过程中没有明显的地壳物质的混染，但是相比正常洋中脊玄武岩（MORB），石山组橄榄玄武岩具有较高的87 Sr/86 Sr比值，较低的ε Nd ( t )值，以及较高的207 Pb/204 Pb（15. 639～15. 643）和208 Pb/204 Pb（38. 977～38. 996）比值，说明其源区为亏损地幔（DM）和富集地幔端元（EMII）的混合。结合地球物理学证据，我们认为亏损地幔来源于软流圈，而EMII端元为含再循环古洋壳及俯冲沉积物的地幔柱，随着海南地幔柱上升，再循环物质熔融并与周围软流圈地幔橄榄岩反应形成含石榴子石辉石岩，随着地幔柱的不断上升，辉石岩首先发生部分熔融，形成的岩浆经历了橄榄石和微弱单斜辉石的分离结晶作用后形成了石山组橄榄玄武岩。华南新生代玄武岩同石山组橄榄玄武岩具有相似的地球化学特征，反映二者具有相同的物质端元组成，但两者岩浆演化上升的动力学机制不同，同时不同端元混合的比例及部分熔融程度也有差异。 相似文献
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山东地区新生代玄武岩主要分布在郯庐断裂带及其以东地区,在鲁西地区分布较少。本文报道了鲁西地区周村玄武岩的全岩主、微量元素组成、橄榄石斑晶及其熔体包裹体Pb同位素组成。结果表明,周村玄武岩为弱碱性玄武岩,其主量元素具有较高SiO_2和Al_2O_3,较低碱(Na_2O+K_2O)、CaO/Al_2O_3、Fe_2O_3~T(Fe_2O_3~T=Fe O/0.8998+Fe_2O_3)的特征;微量元素在原始地幔标准化蛛网图上与EMI洋岛玄武岩(OIB)相似,表现为明显的Ba、K和Sr正异常,Th和Pb负异常,无Nb、Ta和Ti异常;熔体包裹体~(207)Pb/~(206)Pb和~(208)Pb/~(206)Pb分别为0.894~0.921和2.166~2.213,略高于EMI-OIB。这些特征和鲁西地区无棣大山玄武岩有明显区别,但与山东其它地区的弱碱性-拉斑玄武岩相似。周村玄武岩的橄榄石斑晶Ni、Fe/Mn和Ca分别为1403~2611μg/g,70~93和824~2003μg/g。与橄榄岩熔体结晶的橄榄石成分相比,给定橄榄石Fo值,周村玄武岩橄榄石斑晶具有高Ni和Fe/Mn比值,低Ca的特征。结合全岩低CaO和高FeO/MnO比值,橄榄石成分指示周村玄武岩的源区岩性为辉石岩,其形成需要高比例的来自再循环地壳的英安质熔体交代地幔橄榄岩。高比例的英安质熔体和周村玄武岩的微量元素特征,进一步说明该再循环地壳为含辉长岩洋壳。本文的研究结果暗示山东地区弱碱性-拉斑玄武岩的源区辉石岩,主要与再循环洋壳有关。 相似文献
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广西涠洲岛晚新生代玄武岩地幔源区及岩浆成因 总被引：1，自引：0，他引：1
涠洲岛作为我国最年轻的第四纪火山岩岛,其火山活动表现出多期、多旋回和多喷发中心的特征,但其地幔源区特征和岩浆成因依然存在争议。本文对涠洲岛玄武岩开展了详细的矿物学和全岩主、微量元素及Sr-Nd-Pb同位素研究,以揭示其地幔源区特征和岩浆成因。涠洲岛玄武岩主要为碱性玄武岩,在岩浆上升过程,几乎未受到地壳物质的混染,经历了橄榄石和单斜辉石的分离结晶作用。轻稀土(LREE)富集、重稀土(HREE)亏损,轻、重稀土强烈分馏((La/Yb)N=14.42～28.64),Nb、Ta明显正异常,显示出与洋岛玄武岩(OIB)相似的微量元素和Sr-Nd-Pb同位素特征。Sr-Nd-Pb同位素比值变化较均一,且呈现出亏损地幔端元(DM)与富集地幔端元(EM2)的二元混合趋势。其中,EM2端元可能源于海南地幔柱。Sr/Sr*(1.21～2.36)和Eu/Eu*(1.01～1.11)正异常,指示源区存在再循环辉长岩洋壳组分。结合已有的地震层析成像结果和岩石地球化学数据,得出南海及周缘地区的晚新生代玄武岩的形成受控于海南地幔柱。伴随着海南地幔柱的上升,再循环的辉长岩洋壳经部分熔融与地幔橄榄岩反应生成石榴石辉石岩(贫硅辉石岩),石榴石辉石岩和未反应的地幔橄榄岩混合部分熔融形成涠洲岛玄武岩。 相似文献
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我国华北北部新近纪喷发的汉诺坝玄武岩,岩层出露比较完整,普遍含有超镁铁岩包体和各种高压巨晶。大麻坪代黄沟剖面出露较好,主要岩性为玄武岩,从上到下可分为上三、二、一层和底层。岩相学观察显示这些玄武岩含有1%~5%的捕虏晶且斑晶数量很少。橄榄岩包体为尖晶石二辉橄榄岩,轻稀土略微亏损,轻重稀土无分馏,显示这是只经过少量部分熔融后的原始地幔包体。通过对代黄沟碱性玄武岩中橄榄石、辉石和斜长石等斑晶或捕虏晶的矿物学分析,得出它们的成分变化是玄武岩混合了分解的地幔橄榄岩快速上升造成的。玄武岩的主量元素与二辉橄榄岩相平衡的原生熔体相比,Mg#(52.0~62.7)以及CaO(7.3%~8.5%)、Ni((82~192)×10-6)和Cr((65~192)×10-6)含量都较低。玄武岩的稀土分配模式为轻稀土富集的右倾型,δEu=1.01~1.05,δCe=0.95~1.02,富集高场强元素Nb、Ta、Zr及大离子亲石元素Ba、Sr。玄武岩痕量元素Ba/Rb和Rb/Sr的比值显示源区可能遭受过流体的交代作用。同时,痕量元素显示这一系列玄武岩主要受到部分熔融的控制,大量的结晶分异并未发生,且源区残留石榴子石。分析认为玄武岩岩浆应该是原生岩浆,而不是演化岩浆,影响整个岩浆的形成的过程可能是部分熔融而不是分离结晶。基于目前已发表的实验岩石学结果和理论分析认为汉诺坝玄武岩与辉石岩类相平衡,源区主要矿物相为单斜辉石和石榴子石,可能存在少量的橄榄石。 相似文献
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《地球化学》2016,(1)
报道了山东昌乐地区新生代王家大山玄武岩的全岩主元素、微量元素,橄榄石斑晶及被其捕获的熔体包裹体主元素和铅同位素组成。王家大山玄武岩为弱碱性-拉斑玄武岩。全岩主元素成分和熔体包裹体的SiO_2、TiO_2、Al_2O_3、CaO、Na_2O、K_2O和P_2O_5含量均与MgO含量呈负相关关系,CaO/Al_2O_3值基本不变;在微量元素原始地幔标准化蛛网图上与EMI洋岛玄武岩(OIB)相似,表现为明显的Ba、K和Sr正异常,Th和Pb负异常,无Nb-Ta和Ti异常。熔体包裹体铅同位素组成为208Pb/206Pb=2.091~2.166和207Pb/206Pb=0.846~0.899,其变化范围覆盖了山东地区新生代强碱性玄武岩到弱碱性-拉斑玄武岩的铅同位素范围;根据铅同位素组成,熔体包裹体可以分为低铅同位素组(207Pb/206Pb0.86)和高Pb同位素组(207Pb/206Pb0.87)。橄榄石斑晶Ni、Fe/Mn和Ca分别为1312~2417μg/g、71~92和745~2068μg/g,与典型辉石岩熔体结晶的橄榄石斑晶成分相当,但是,比橄榄岩熔体结晶的橄榄石成分高Ni和Fe/Mn,低Ca。全岩和熔体包裹体主元素的成分变化,结合岩相学和MELTS软件模拟结果,指示王家大山玄武岩主要经历了橄榄石结晶分离作用。橄榄石斑晶高Ni和Fe/Mn,低Ca,结合全岩高Fe/MnO值和低CaO,说明其源区岩石为辉石岩。全岩微量元素和熔体包裹体铅同位素指示源区有EMI组分,可能和再循环洋壳辉长岩有关。熔体包裹体两组铅同位素组成指示王家大山玄武岩源区是不均一的,暗示山东地区新生代玄武岩的源区是高度不均一的。 相似文献
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新疆东天山黄山岩体岩石地球化学特征与岩石成因 总被引：1，自引：0，他引：1
黄山岩体位于东天山北部的土墩-黄山-图拉尔根镁铁-超镁铁质岩带中段,受康古尔塔格-黄山韧性剪切带控制,主要由橄榄岩、橄榄二辉岩、辉石岩、辉长苏长岩、辉长岩以及辉长闪长岩组成.岩石化学组成属拉斑玄武岩系列,普遍富集大离子亲石元素(Rb,Ba,Sr),亏损高场强元素(Nb,Ta,Ti).岩体εNd(t)=+4.1～+9.2,除3件样品εSr(t)为+2.2,+12.5和+15.4,大部分εSr(t)=(-22.5～-4.5),Nd,Sr同位素组成基本属亏损型地幔特征;Pb同住素初始值(206Pb/204Pb)i=18.081～18.413,(207Pb/204Pb)i=15.441～15.513,(208Pb/204Pb)i=37.461 6～37.899,具有MORB亲和性.岩相学及岩石地球化学特征显示岩浆演化过程中主要发生了橄榄石、斜方辉石、单斜辉石和斜长石的分离结晶作用.岩浆演化晚期阶段发生了一定程度的同化混染作用,元素地球化学和Nd,Sr,Pb同位素体系证明,岩浆源区主体由软流圈地幔物质组成,同时也有一定量富集型岩石圈地幔组份加入.黄山岩体是岩石圈根部拆沉加热熔融和软流圈地幔上涌减压熔融的产物,这种地幔动力学机制应该对应于后碰撞伸展环境. 相似文献
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华北龙岗第四纪玄武岩：岩石成因和源区性质 总被引：1，自引：1，他引：1
华北克拉通东北缘龙岗第四纪玄武岩的地球化学研究为大陆碱性玄武岩的成因以及源区的性质提供了重要的依据。龙岗第四纪玄武岩为碱性玄武岩,具有类似 OIB 的 REE 和微量元素分配特征。岩石的 Sr-Nd 同位素轻度亏损(~(87)Sr/~(86)Sr=0.7044～0.7048,ε_(Nd)=0.6～2.1),具有 Dupal 异常的高放射性成因 Pb 同位素组成(~(206)Pb/~(204)Pb:17.734～18.194,~(207)Pb/~(204)Pb=15.553～15.594,~(208)Pb/~(204)Pb=38.322～38.707)。这种地球化学特征指示了原始岩浆起源于<70km 深度的地幔,并经历了一定程度的橄榄岩、单斜辉石和钛-铁氧化物的结晶分异。岩浆源区中以来类似 MORB 软流圈物质的熔体为主,另外有少量来自 EM Ⅰ性质的富集岩石圈地幔以及俯冲流体/熔体的物质贡献,显示了深部岩石圈-软流圈一定程度的相互作用以及太平洋板块俯冲的影响。岩浆源区多种端元组分的存在表明该地区岩石圈的减薄/置换受到多种因素的影响。 相似文献
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幔源玄武岩及地幔捕虏体中所含的地幔流体挥发分对于认识岩浆源区特征及岩石圈地幔演化具有重要意义。本文对东北地区双辽新生代玄武岩及其携带的地幔捕虏体中流体挥发分进行研究,探究地幔流体特征与来源。双辽玄武岩橄榄石斑晶和地幔捕虏体内发育早期、晚期两类流体包裹体,早期流体包裹体中的挥发分代表矿物形成时捕获的岩浆原始流体挥发分,主要在高温段(600~1200℃)释出,晚期流体包裹体中的挥发分代表矿物形成后捕获的交代或蚀变流体挥发分,主要在低温段(200~600℃)释出。地幔捕虏体原始流体挥发分主要为H_2O、CO和H_2,其次为CO_2,并含有少量CH_4等烃类。地幔捕虏体交代流体挥发分与双辽玄武岩橄榄石斑晶原始流体挥发分相似,主要为CO_2和H_2O,其次为CO和H_2,含有少量烃类。地幔捕虏体原始流体挥发分、交代流体挥发分及玄武岩橄榄石斑晶原始流体挥发分中,CO_2和烃类碳同位素均具有有机成因特征,表明岩石圈地幔及玄武岩岩浆源区内均存在有机质热解产物的混入,玄武岩岩浆源区及岩石圈地幔交代流体中的有机成因挥发分主要来自于俯冲太平洋板片之上的沉积有机质。双辽玄武岩斜长石斑晶和基质流体挥发分含量较高,主要为H_2O和CO_2,相对于橄榄石原始流体挥发分具有较轻的CO_2碳同位素组成,这种现象表明岩浆上升过程中发生了明显的脱气作用。 相似文献
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Guboglo M. N. 《GeoJournal》1980,4(1):53-58
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
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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
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Deviation of the major axis of the inertia ellipsoid of the Moon from the direction toward the Earth
B. P. Kondratyev 《Astronomy Reports》2017,61(8):709-714
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
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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.
17.
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
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
18.
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
19.
The Importance of the Precipitation and the Susceptibility of the Slopes for the Triggering of Landslides Along the Roads 总被引：3，自引：1，他引：2
Clemente Irigaray Francisco Lamas Rachid El Hamdouni Tomás Fernández José Chacón 《Natural Hazards》2000,21(1):65-81
In order to characterise the influence of the heavyrains on the observed landslides during the 1996–1997hydrological cycle, rainfall records for the last 100years are analysed from 104 stations in easternAndalusia. Regarding the amounts of rain recordedbetween October 1996 and March 1997 in the 104stations studied, 31 presented new all-time records;15 presented values that were 80–100% of thepre-1995 record; 49 stations, 80–50%; and 9stations, < 50%. A map has been devised of thesusceptibility of the materials through which thesouth-eastern Andalusian road network crosses,together with an inventory of the damage caused byinstability phenomena on banks and cuttings of theroad network during the winter of 1996–1997. Therelationships between the rainfall during the studyperiod, the damage caused to the road network and thesusceptibility of the materials affected are analysed.The results indicate that there is a clearcorrespondence between the rainfall recorded and thesusceptibility of the materials with the inventorieddamage. It is concluded that the widespread seriousdamage caused in early 1997 to the roads andsurrounding areas in the Alpujarra region and thecoast of the Province of Granada was mainly caused bythe extraordinarily heavy rains. However, considerablyless damage was observed where the susceptibility ofthe terrain is low, thus highlighting the extremeusefulness of terrain-susceptibility maps for riskprevention and territorial planning. 相似文献
20.
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