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1.
中天山北缘干沟蛇绿混杂岩带的地质地球化学 总被引：7，自引：3，他引：7
中天山北缘干沟蛇绿混杂岩带主要由属于弧前火山-沉积岩系的混杂基质及其襄胁的构造岩块组成,后者主要包括蛇绿岩残块、岛弧火山岩残块,以及大理岩、花岗岩等外来构造岩块。并因蛇绿岩及岛弧火山岩的出露而成为古板块缝合带的标志。干沟蛇绿岩岩石组合出露较为齐全,包括变质橄榄岩(蛇纹岩)、辉长岩、辉绿岩、玄武岩等构造岩块,但几乎均呈零散的构造岩块,散布于混杂基质中。变质橄榄岩以相对低SiO_2、TiO_2、Al_2O_3和CaO、高MgO为特征,类似于大洋中脊二辉橄榄岩主元素化学组成；∑REE低,LREE亏损,富集Cr、Ni,与世界典型蛇绿岩的超镁铁单元岩石地球化学特征类似。玄武岩的地球化学研究表明其以中等TiO_2、高MgO,不具有Nb、Ta亏损和Th富集为特征；与MORB相比较,高场强元素(HSFE)丰度低且平坦不分异；与原始地幔相比较,具有类似于N-MORB的亏损地幔特征,主、微量元素的地球化学特征显示岩石应形成于洋中脊构造环境。岛弧型火山岩出露于混杂岩带南部,主要为橄榄粗安岩；主元素以高MgO、Al_2O_3、K_2O、Na_2O、K_2O/Na_2O≈1、低TiO_2和CaO含量,富含挥发份为特征。同时,富集大离子亲石元素Rb、Ba、zr、Th、U和LREE等,并以Nb、Ta亏损和Th富集显示其成因与消减作用有关,形成于板块俯冲过程中的活动大陆边缘火山弧环境。干沟区段的混杂岩因存在蛇绿岩和与俯冲作用有关的火山岩而厘定为蛇绿混杂岩带,并指示沿中天山北缘曾存在古洋盆及其俯冲消减作用。 相似文献
2.
东昆仑可支塔格蛇绿混杂岩的地质地球化学特征 总被引：1，自引：0，他引：1
东昆仑可支塔格蛇绿混杂岩属于木孜塔格-鲸鱼湖大断裂的西延部分,主要由辉橄岩、辉长岩、闪长岩、斜长花岗岩、辉绿岩、玄武岩及硅质岩等组成,形成时代为早石炭世。为构造强烈破坏的蛇绿混杂岩,形成于俯冲带环境,属SSZ型蛇绿岩。其中辉橄岩以相对低SiO2、TiO2、Al2O3和CaO、高MgO为特征,贫有色金属成矿元素,富集相容元素Cr、Ni、Co。稀土总量低,接近于球粒陨石稀土元素总量,以LREE略富集为特征。闪长岩SiO2、K2O含量较低,MgO、CaO、Na2O较高,稀土总量高,∑REE为90.95μg/g,LREE富集。斜长花岗岩SiO269.8%,Na2O>K2O,K2O/Na2O为0.78,A/CNK为1.68,具有大洋斜长花岗岩的岩石化学特征。闪长岩、斜长花岗岩的微量元素特征相似,表现为大离子亲石元素K、Sr、Rb、Ba相对富集,高场强元素Nb、Ta、Zr、Hf相对亏损。研究表明,辉橄岩来源于亏损的地幔岩,接近于强烈亏损的方辉橄榄岩,而明显不同于结晶分异作用成因的超镁铁质岩石。闪长岩、斜长花岗岩为蛇绿混杂岩的浅色岩组分,是地幔岩浆结晶分异的产物。 相似文献
3.
东准噶尔卡拉麦里SSZ型蛇绿岩地球化学及其构造意义 总被引：2，自引：0，他引：2
卡拉麦里蛇绿岩带受控于卡拉麦里深大断裂,主要由超镁铁质岩体、镁铁质岩脉和火山熔岩组成.超镁铁质岩体主要由地幔方辉橄榄岩组成,并有纯橄岩和铬铁矿矿石产出.超镁铁质岩石具有低SiO2、高MgO、LREE富集的"V"字形和LREE略富集型稀土元素分布模式,具有SSZ(supra subduction zone)型的地幔橄榄岩特征.玄武岩、堆晶辉长岩以及辉长闪长岩岩脉具有低Al2O3、TiO2、K2O+Na2O含量,且K2O＜Na2O,具相对高的MgO和极低的P2O5含量,具低Ti/V比值(10～20)、低的稀土元素丰度和LREE弱亏损型稀土元素配分模式,显示与洋内板块俯冲作用有关的SSZ型蛇绿岩地球化学特征.碱性玄武岩则具有洋岛玄武岩特征,具有高Al2O3、TiO2(2.50%～3.43%,平均3.16%)、K2O+Na2O(7.36%～9.40%)、P2O5(0.509%～1.579%,平均0.80%)和Ti/V(＞50),相对低MgO(1.84%～2.81%,平均2.60%)的特征,富集不相容元素并具高的稀土元素总量和轻稀土元素明显富集的稀土元素配分模式,显示洋岛玄武岩特征,代表了洋盆早期洋内热点作用.卡拉麦里蛇绿岩带反映了哈萨克斯坦-准噶尔联合陆块与西伯利亚板块的古洋盆经历了洋内热点作用和大洋板块洋内俯冲消减的演化过程. 相似文献
4.
中天山南缘乌瓦门地区发现蛇绿混杂岩 总被引：9，自引：1，他引：9
新发现的乌瓦门蛇绿混杂岩出露于中天山南缘断裂带中,主要表现为以变质粉砂岩为主的基质中混杂着大小不一、性质各异的块体。基质主要为泥盆纪绢云石英片岩、绢云绿泥石英片岩、二云石英片岩、千枚岩和变质粉砂岩,块体有肢解的蛇绿岩岩块、片麻岩岩块和大理岩岩块。肢解蛇绿岩岩块主要有含辉纯橄岩岩块、辉长岩岩块、基性火山岩岩块和硅质岩岩块。 相似文献
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多彩蛇绿岩是通天河蛇绿混杂岩的组成部分,区域上隶属西金乌兰—金沙江缝合带北延部分。多彩蛇绿岩各岩石组分呈构造岩块、岩片产出,出露零星,面积小,但岩石组分较齐全,主要由异剥橄榄岩、单斜辉石岩、辉长岩、玄武岩、辉绿岩及硅质岩等组成,缺乏地幔橄榄岩,蛇绿岩组分均与围岩呈构造接触关系。异剥橄榄岩以富MgO、贫TiO2、贫P2O5为特征,Eu不显异常或显弱负异常,是具有SSZ型蛇绿岩的重要岩石组分;辉长岩具高TiO2、Al2O3;玄武岩与辉绿岩具相似的特性,玄武岩Th/Ta平均为1.78,Ta/Hf0.15,而Ta/Hf=0.15～0.2,与大洋板内玄武岩相似;硅质岩Al2O3/(Al2O3+Fe2O3)比值为0.9,(La/Ce)N值为1.81,可能具有陆源海特性。由上述特征并结合蛇绿岩形成时代及构造环境判别图解,推测多彩蛇绿岩形成于俯冲带构造环境。 相似文献
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新疆南天山北缘白土塘出露一部分蛇绿混杂岩,为了解其中超基性一基性岩的形成环境,笔者主要利用地球化学的研究方法对该区的9个样品进行了测试。通过地球化学研究分析,认为本区的蛇纹岩以低SiO2、TiO2、CaO、K2O、Na2O,高MgO、Al2O3为特征,富集相容元素Cr、Co、Ni,贫不相容元素,同时大离子亲石元素含量较低,整体特征类似于大洋二辉橄榄岩,具有地幔残留物的特征。对玄武岩的地球化学研究表明,其以富TiO2、MgO,贫Al2O3、K2O,且Na2O〉K2O为特征;与MORB相比较,明显亏损Nb、Ta;与原始地幔相比较,具有类似于N-MORB的亏损地慢特征;主、微量元素的地球化学特征显示岩石应形成于类似洋中脊的构造环境,岩浆源于亏损地幔区。 相似文献
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新疆库米什北超基性岩发现及大地构造意义 总被引：1，自引：0，他引：1
新疆库米什北超基性岩的发现,为中天山南缘长阿吾子-古洛沟-吾瓦门蛇绿混杂岩带东延提供了重要地质依据。该超基性岩主要为变质橄榄岩,呈构造岩块出露于韧性剪切带中。原岩以蚀变单辉橄榄岩、二辉橄榄岩、辉橄岩为主,属钙碱性岩系。岩石普遍蛇纹石化、片理化,与围岩呈构造接触关系。M/F比值平均15.1,大于7,MgO/(MgO+FeO)平均比值0.85,TiO2含量为0.03%～0.14%,小于0.22%。轻重稀土元素分异明显,具Eu正异常特征。表明出露于中天山南缘最北部古洛沟-吾瓦门-拱拜子蛇绿混杂岩带与库米什以南地区榆树沟-铜华山-硫磺山蛇绿混杂岩带并非同一条蛇绿岩带。 相似文献
8.
西藏东巧蛇绿岩的地球化学特征及其形成的构造环境 总被引：7，自引：3，他引：4
西藏东巧蛇绿岩主要由变质橄榄岩、辉长岩及玄武岩等组成。变质橄榄岩以富Mg、Fe、Cr,贫Ti、ΣREE为特征。辉长岩和玄武岩的主量元素、微量元素特征显示其具有扩张洋脊拉斑玄武岩的地球化学特征,其中高场强元素Nb、Ta、zr、Hf等亏损,大离子亲石元素Rb、sr、Ba等相对富集;在球粒陨石标准化稀土元素配分模式图上为LREE亏损的平坦型,无负Eu异常,与洋中脊玄武岩的特征类似。根据其地球化学属性,推测该区蛇绿岩形成于大洋盆地扩张的构造环境。 相似文献
9.
西藏永珠——果芒错蛇绿岩的地球化学特征及其构造意义 总被引：8，自引：1，他引：7
永珠-果芒错蛇绿岩位于西藏永珠藏布-纳木错蛇绿岩带西段,主要由变质橄榄岩、辉长辉绿岩及玄武岩等组成。变质橄榄岩以富Mg,贫Ti、∑REE为特征。辉绿岩和玄武岩的主量元素、微量元素分析显示其含有洋脊拉斑玄武岩和岛弧拉斑玄武岩的双重成分特征,其中高场强元素（Nb、Ta、Zr、Hf等）亏损,大离子亲石元素（Rb、Sr、Ba等）相对富集,具有岛弧玄武岩的特点;在球粒陨石标准化稀土元素配分模式图上显示稀土元素特征为LREE亏损的平坦型,无负Eu异常,与洋中脊玄武岩的特征类似。通过与典型地区作对比和应用构造环境判别图解,推断永珠-果芒错蛇绿岩形成于弧后盆地的构造环境。 相似文献
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西藏纳木错西岸蛇绿岩的地球化学特征及其形成环境 总被引：14，自引：4，他引：10
西藏纳木错西岸蛇绿岩主要由变质橄榄岩、辉长辉绿岩及玄武岩等组成。变质橄榄岩以富Mg、贫Ti、贫REE元素为特征。辉绿岩和玄武岩的主量元素、微量元素特征显示其含有洋脊拉斑玄武岩和岛弧拉斑玄武岩的双重成分,其中高场强元素Nb、Ta、Zr、Hf等亏损．大离子亲石元素Rb、Sr、Ba等相对富集,具岛弧玄武岩的特点;在球粒陨石标准化稀土元素配分模式图上为LREE亏损的平坦型,无负Eu异常,与洋中脊玄武岩的特征类似。通过与典型地区作对比并应用构造环境判别图解,推测该区蛇绿岩形成于弧后盆地的构造环境。 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.
Jiayu Rong Michael Melchin S. Henry Williams Tatyana N. Koren Jacques Verniers 《《幕》》2008,31(3):315-318
The Global Stratotype Section and Point （GSSP） for the base of the Silurian System was defined in 1985. Since that time, a number of researchers have suggested that this section has serious deficiencies for use as a GSSP. As a result, in 2000, the Subcommission on Silurian Stratigraphy （SSS） proposed undertaking a formal restu@ of this GSSP, which was subsequently approved by the International Commission of Stratigraphy （ICS）. The result of this restudy was the formal proposal that the current GSSP, at 1.6 m above the base of the Birkhill Shale, at Dob＇s Linn, Scotland, should be maintained as the same locality and stratigraphic level, but the bios- tratigraphical definition of the boundary should be revised. The previously defined, basal Silurian grapto- lite zone, the Parakidograptus acuminatus Zone, should be subdivided into a lower Akidograptus ascensus Zone and a higher E acuminatus Zone. The base of the A. ascensus Zone, marked by the first appearance of A. ascensus, should be regarded as the biostratigraphic mark for the base of the Silurian. This proposal has now been formally approved by the SSS and ICS, and ratified by International Union of Geological Sciences. This is the first GSSP to undergo formal restudy and redefini- tion, and the proposal also included a recommended procedure for restudy of GSSPs. 相似文献
13.
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
14.
Important tendencies in development of the world mineral-resources sector at the beginning of the 21st century were an increase in production and consumption of mineral materials differentiated by types of metals and nonmetallic mineral raw materials, by countries and regions, as well as the concentration of the production of mineral raw materials in a small number of countries, and a reduction in industrial reserves of minerals in the world economy, even at the current stage of their extraction. These tendencies should be taken into account in working out a strategy for development of the Russian mineral raw-material base. 相似文献
15.
Fouad N. Ibrahim Dr. 《GeoJournal》1988,17(1):133-141
Taking the example of W Sudan, an analysis of the climatic incidents leading to the two recent famine disasters is made. On this natural background, the human side is investigated. Focus is directed towards the fragile economic structure of the famine-prone population groups. An early-warning system for famine in the Sahelian Zone is proposed taking grain production and storage, livestock development and the relationship between the prices of livestock and grain as major indicators. 相似文献
16.
东濮凹陷北部沙三中亚段广泛发育盐岩和烃源岩,这两个看似不能共存的物质却在这里互层共生。该时期研究区沉积特征为多盐韵律与多层烃源岩互层共生、连续沉积,单个盐韵律厚度从几米到十几米,烃源岩有机质丰度高、类型好。平面上,两者在湖盆沉积沉降中心共生;垂向上,高有机质丰度、好干酪根类型与高盐度地层具有较好的对应关系。因而成为恢复古气候和古环境的重要研究对象。通过岩石学、古生物学以及Sr/Ba、B/Ga、(V+Ni+Mn)、Fe/Mn、Sr/Cu、Mg/Ca、V/(V+Ni)、稀土元素含量和氯同位素等方法对凹陷北部沙三中亚段的沉积环境进行研究。结果表明,凹陷北部沙三中亚段为深水沉积的还原环境,古盐度较高,达到半咸水-咸水沉积;微量元素和孢粉化石特征表明研究区沙三中亚段为温暖潮湿的环境。 相似文献
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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.
郯庐断裂南段研究进展与断裂性质讨论 总被引：13，自引：3，他引：13
据1：5万区域地质调查和专题研究资料，就郯庐断裂带是否南延与消失的原因，其与大别—苏鲁造山带交截形成的假位错效应，以及与中新生代沉积盆地形成演化的关系等作了新的阐述。在此基础上，讨论了郯庐断裂带是否为巨大的左行平移断层或转换断层。认为郯庐断裂带可能是在“古郯庐带”的基础上于早侏罗世重新活动、白垩纪强烈活动的地堑型枢纽断裂带。 相似文献