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1.
岩浆混合作用:来自岩石包体的证据 总被引：20，自引：1，他引：19
镁铁质岩浆与长英质岩浆之间的混合作用是导致壳幔混源花岗岩类形成的主要机制。暗色、细粒且具火成结构的岩石包体是指示岩浆混合作用存在的可靠证据。这些岩石包体具有下列特征:(1)包体常呈等轴状,表明包体岩浆曾以液态球滴状存在于寄主岩浆中;(2)由于基性岩浆温度恒高于酸性岩浆(温度超出约300℃),这类包体常具有淬冷边;(3)包体有时含有反向脉;(4)包体中能见到自寄主岩浆捕获的长石捕虏晶。进一步分析了三个典型的含暗色微粒包体的花岗质杂岩(平潭、普陀山、花山—姑婆山)研究实例,认为暗色微粒包体的形成,可用来自深部岩浆房的玄武质岩浆向浅部酸性岩浆房的注入作用来解释。 相似文献
2.
南岭中西段燕山早期北东向含锡钨A型花岗岩带 总被引：23，自引：0，他引：23
南岭中西段,发育着一条北东向的燕山早期含钨锡A 型花岗岩带,该带主要由花山、姑婆山、九嶷山、骑田岭等花岗质岩基和周边岩株群所组成,延伸在250 km 以上,出露总面积超过3 000 km2,含有丰富的钨锡等金属矿产资源。这些花岗质岩体多为多阶段复式岩体,主侵入期花岗岩的侵位年龄多在165~153 Ma 范围内,常常与同时代的偏中性（闪长岩、花岗闪长岩、石英二长岩等）岩株或酸性火山侵入杂岩相伴生,具有岩浆混合特征的暗色包体十分常见。主侵入体多为斑状黑云母花岗岩,有时含角闪石,酸性至超酸性,弱准铝至弱过铝,富含K2O 和总碱,富含大离子亲石元素和高场强元素如Rb, Cs, U, Th, LREE, Y, Nb, Ta, Zr, Hf, Ga 等,Sn, W 等成矿元素及F, Cl 等挥发性组分亦十分丰富。在Whalen 等 (1987) 判别A型花岗岩和未分异M,I,S 型花岗岩的图解上,绝大多数落在A 型花岗岩区。他们的ISr 值变化较大（0.7063 ~ 0.7182）,εNd
（t）值偏高（-1.7 ~ -8.0）,t2DM 值偏低（1.1 ~ 1.6 Ga）,表明花岗岩成分中有不同程度新生地幔物质的参与,尤其以花山和姑婆山花岗岩更为明显。花岗岩体往往强烈分异,晚期（或称补充侵入期）强分异细粒花岗岩的侵位年龄大多在146 ~151Ma 范围内。与主体相花岗岩相比,他们更偏酸性, 过铝, 更富含Rb, Cs, U, Y, Sn, W 等微量元素,但Σ REE (尤其是LREE), Zr等HFSE 含量明显贫化,在岩石化学成分上与S 型花岗岩十分接近。成矿作用贯穿花岗岩侵位和演化的全过程,从主侵入期经补充侵入期到后来的热液期,都能形成Sn,W 等金属矿床。矿化类型多样,包括云英岩型、石英脉型、矽卡岩型、Li-F花岗岩型、锡石硫化物型和绿泥石化构造蚀变带型等,规模可达大型乃至超大型。过去一般认为,Sn/W 矿床主要与S型花岗岩有关,南岭地区富含Sn/W 矿化的A 型花岗岩带的厘定,证明了A 型花岗岩与Sn/W成矿作用密切相关,为在华南乃至
世界其他地区寻找新的锡钨矿床提供了新的理论依据和实际范例。南岭地区在燕山早期的后造山拉张减薄的构造环境,软流圈地幔的上涌和地幔基性岩浆的底侵,壳幔的相互作用和下地壳的高温熔融,花岗质岩浆的分离结晶和分异演化,以及热液的充填和蚀变交代等,是控制本区成岩成矿作用的关键因素。 相似文献
3.
新疆准噶尔地区花岗岩中微粒闪长质包体特征及后碰撞花岗质岩浆起源和演化 总被引：20，自引：0，他引：20
新疆准噶尔地区也布山、庙儿沟两个晚古生代后碰撞准铝一过铝质花岗岩体中，广泛发育大量的暗色微粒闪长质包体。岩石学、矿物学、主量元素和微量元素地球化学研究表明，包体与其寄主岩存在明显的亲缘关系。东准噶尔也布山黑云母花岗岩体中的暗色微粒包体与寄主岩有相似的地球化学成分，表明它是与寄主花岗岩相同成因的同源包体，是来自上地幔的基性岩浆经过高度演化、结晶分异的产物；西准噶尔庙儿沟二长花岗岩体中含钾长石斑晶的微粒包体则主要是由幔源的下地壳基性岩部分熔融形成的残余体，被酸性岩浆携带并发生成分上的同化和混染，最后在上地壳侵位的产物。同准噶尔碱性花岗岩一样，载荷包体的准铝一过铝质花岗岩是晚古生代后碰撞阶段构造一岩浆活动的岩石类型之一，其形成和演化标志了准噶尔地区后碰撞幔源岩浆底侵作用导致大陆地壳垂向生长的过程。 相似文献
4.
南岭西段花山-姑婆山侵入岩带锆石U-Pb年龄格架及其地质意义 总被引：17，自引：2，他引：17
花山-姑婆山侵入岩带位于南岭西段,由牛庙、同安、花山、金子岭、乌羊山和姑婆山等岩体所组成,10个锆石样品的 SHRIMP U-Pb 法、LA-ICP-MS 法和熔融法定年结果显示,该带中主要的闪长质和花岗质岩体侵位于160～163Ma 这一狭窄的时间范围内,表明中—晚侏罗世之交是本区岩浆活动的高峰时期,它们在时间上、空间上、物质来源上、构造背景上和成因机制上有着十分密切的联系。姑婆山里松花岗岩与其中暗色包体结晶年龄的一致性,从一个重要的方面否定了暗色包体是浅部围岩捕虏体或深部熔融残留体的可能性,并为它们的岩浆混合成因提供了一个重要依据。具有充分分异演化特征的新路晚阶段细粒花岗岩小岩体中锆石的 U-Pb 年龄值为151Ma,比主体花岗岩大约晚10Ma,它可能反映了本区主体花岗岩岩浆房分离结晶和演化的时间跨度。桂岭和大宁岩体侵位于加里东晚期。 相似文献
5.
赣南营前岩体的年代学、地球化学、Sr-Nd-Hf同位素组成及其地质意义 总被引：6，自引：1，他引：5
赣南营前岩体由早期似斑状花岗闪长岩和晚期细粒黑云母花岗岩组成,在前者中普遍发育暗色基性包体。SHRIMP锆石U-Pb测年显示似斑状花岗闪长岩为172.2±3.1Ma,细粒黑云母花岗岩为168±3Ma,包体为167.6±3.3Ma。所有的岩石均为钙碱性系列,稀土元素显示LREE富集,HREE亏损,Eu负异常并不明显的特征,Nb-Ta负异常显示壳源物质的特征。晚期细粒黑云母花岗岩、早期似斑状花岗闪长岩、暗色包体的(87Sr/86Sr)i和εNd(t)值分别为0.70885～0.70965、0.71058～1.46393、0.70788～0.70923和-6.38～-5.31、-6.51～-5.17、-5.47～-4.31;锆石εHf(t)值分别为-12.4～-5.7、-9.2～-4.2、-9.4～+0.1。结合岩相学、地球化学研究,初步认为营前岩体的两期花岗质岩石源于地壳重熔,地幔底侵导致地壳熔融形成营前岩体,基性岩浆加入到未冷却的酸性岩浆中形成了目前所见到的暗色包体。结合区域上的研究资料,认为中侏罗世期间,沿"十杭"断裂带及与其相平行的一些深断裂发生了板块的撕裂,这些缝合带是岩石圈相对薄弱的地带,有利于幔源物质底侵上升以及壳幔相互作用。 相似文献
6.
本文研究了花山花岗岩的岩石学、地球化学和同位素地质学特征,确定了花山岩体是一个由三期独立的、不同时代、不同成因和不同物质来源的花岗质岩浆岩所组成的复式岩体。第一期印支期牛庙石英二长岩和同安石英二长岩,属以幔源物质为主的壳幔混合来源,由上地幔分异岩浆上侵并同化混染了地壳物质而形成;第二期燕山早期花山主体花岗岩亦属壳幔混合来源,但其壳幔物质比值有所增高。上地幔沿东西向区域性深断裂的上拱和地壳物质(包括沉积组分和火成组分)受热重熔,是该期花岗岩的可能成因;第三期燕山晚期细粒花岗岩小岩体是由以沉积组分为主的地壳物质经部分熔融、重熔或深熔而成。 相似文献
7.
暗色微粒包体常见于钙碱性花岗岩中,已普遍被认为是幔源基性岩浆与壳源酸性岩浆在地壳深部发生混合作用的产物。本文通过大量资料的分析研究,发现暗色微粒包体可以具有很大负值的全岩εNd（t）值和锆石εHf（t）值,及大于0710的全岩\[n（87Sr）/n（86Sr）\]i值,不存在幔源岩浆混合的痕迹;而且,大多数暗色微粒包体与寄主花岗岩在晶体化学、形成年龄、全岩和锆石同位素成分等方面显示出完全相似的特征,反映出两者在时空与物质上都具有紧密的成因联系。本文认为,暗色微粒包体不应该是壳幔岩浆混合作用的产物。基于包体岩浆极小的体量和稍晚的侵位（相对于寄主花岗岩）,本文提出一种新的暗色微粒包体的形成方式：同造山花岗岩浆的主动上侵造成岩浆房内的 “负压力” 而导致岩浆房下部呈晶粥状态的闪长质层发生等温减压熔融作用,从而形成体量极小的包体岩浆;并即时 “注入” 地壳上部尚未固结的寄主花岗岩中,快速冷凝形成暗色微粒包体。因此,暗色微粒包体不能被视作为 “壳幔岩浆混合作用” 的证据。 相似文献
8.
暗色微粒包体常见于钙碱性花岗岩中,已普遍被认为是幔源基性岩浆与壳源酸性岩浆在地壳深部发生混合作用的产物。本文通过大量资料的分析研究,发现暗色微粒包体可以具有很大负值的全岩εNd(t)值和锆石εHf(t)值,及大于0.710的全岩[n(87Sr)/n(86Sr)]i值,不存在幔源岩浆混合的痕迹;而且,大多数暗色微粒包体与寄主花岗岩在晶体化学、形成年龄、全岩和锆石同位素成分等方面显示出完全相似的特征,反映出两者在时空与物质上都具有紧密的成因联系。笔者认为,暗色微粒包体不应该是壳幔岩浆混合作用的产物。基于包体岩浆极小的体量和稍晚的侵位(相对于寄主花岗岩),笔者提出一种新的暗色微粒包体的形成方式：同造山花岗岩浆的主动上侵造成岩浆房内的“负压力”而导致岩浆房下部呈晶粥状态的闪长质层发生等温减压熔融作用,从而形成体量极小的包体岩浆;并即时“注入”地壳上部尚未固结的寄主花岗岩中,快速冷凝形成暗色微粒包体。因此,暗色微粒包体不能被视作为“壳幔岩浆混合作用”的证据。 相似文献
9.
东准噶尔库布苏南岩体中闪长质包体特征及地质意义 总被引：1，自引：0，他引：1
新疆东准噶尔卡拉麦里地区库布苏南晚古生代后碰撞准铝质过铝质花岗闪长岩体中广泛发育大量的暗色微粒闪长质包体.岩石学、矿物学、主量元素和微量元素地球化学研究表明,包体在地球化学特征上表现为与寄主花岗岩既相互联系又受其制约.库布苏南花岗闪长岩体具有低锶初始比值I(Sr)和正εNd(t)值,表明花岗岩的来源有地幔物质参与,而大量发育的暗色微粒闪长质包体是壳幔岩浆混合作用最直接的证据,微粒包体是基性源岩部分熔融作用形成的残余体.与准噶尔碱性花岗岩一样,载荷包体的准铝质过铝质花岗岩是晚古生代后碰撞阶段构造岩浆活动的岩石类型之一,其形成和演化标志了准噶尔地区后碰撞幔源岩浆底侵作用导致大陆地壳垂向生长的过程. 相似文献
10.
义敦岛弧措交玛岩体岩浆混合成因:镁铁质微粒包体的证据 总被引：2，自引：0，他引：2
义敦岛弧北部的措交玛岩基岩体主要由黑云母二长花岗岩和边部的花岗闪长岩组成。在黑云母二长花岗岩中存在有少量镁铁质微粒包体,其成分为闪长质,与寄主岩石接触关系从渐变到截然。在包体周围的寄主岩石中存在黑云母、角闪石自身的包含结构,角闪石包含黑云母,斜长石发育明显的溶蚀结构,核部斜长石被溶蚀成筛状,边部环带状斜长石溶蚀不明显,是基性岩浆注入到酸性岩浆中导致岩浆混合的结果。黑云母二长花岗岩具有更高的轻重稀土分异系数,闪长质包体轻重稀土分异系数较低,黑云母二长花岗岩和暗色闪长质微粒包体具有明显相似性的微量元素特征。寄主岩黑云母二长花岗岩锆石U-Pb年龄为236±1.9Ma,闪长质包体为235±3.9Ma,二者形成年代在误差范围内基本一致,可能为甘孜-理塘洋向西俯冲过程中,俯冲洋壳部分熔融形成的玄武质岩浆上涌底侵于壳-幔边界导致地壳的部分熔融形成酸性的黑云母二长花岗岩岩基。 相似文献
11.
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
12.
13.
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
14.
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
15.
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 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.
Michel Westphal Mikhail L. Bazhenov Jean Paul Lauer Diamar M. Pechersky Jean-Claude Sibuet 《Tectonophysics》1986,123(1-4)
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