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1.
武当地块基性岩墙群与耀岭河群基性火山岩的 Sr、 Nd、 Pb 同位素特征反映它们具相同的混合地幔源区。前者的(87 Sr/86 Sr)i= 06905~07061, ε N d (t) = - 19~50, Δ208 Pb/204 Pb= 3549~19026, Δ207 Pb/204 Pb= 4~85, Th/ Ta 低, La/ Yb 变化大;后者的(87 Sr/86 Sr)i= 06487~07075,ε N d(t)= 011~394, Δ208 Pb/204 Pb= - 8158~21995, Δ207 Pb/204 Pb= 444~1668, Th/ Ta 和 La/ Yb 较高。这指示它们的源区以岩石圈亏损地幔和第2 类富集地幔为主要混合组分, 耀岭河群基性火山岩曾遭受地壳物质的混染。结合它们具大陆拉斑玄武岩地球化学特征, 代表同源异相裂谷环境的产物推断, 南秦岭基底陆块在新元古代时曾发生过一次重要裂解作用, 并向早古生代秦岭洋盆转变。  相似文献   

2.
安徽庐枞中生代火山岩系的特征及其形成的构造背景   总被引:15,自引:6,他引:15  
孙冶东  杨荣勇 《岩石学报》1994,10(1):94-103
庐枞地区中生代火山岩素是一套由粗面玄武岩-玄武粗安岩-粗安岩-粗面岩组成的岩石组合。岩石硅近饱和,全碱含量(尤其是K2O)高,K2O/Na2O、Fe2O3/FeO比值大,Al2O3含量高且变化大,TiO2含量低,富集Rb、Sr、Ba、Zr、Th、U和LREE等元素,稀土配分为轻稀土富集型,锶、铅、氧等同位素显示了岩浆的幔源特征。本文通过详细的岩石化学和地球化学的对比研究,认为庐枞中生代火山岩系属于橄榄玄粗岩系,它形成于活动大陆边缘由挤压作用向引张作用转变的过渡时期,是火山弧后拉张形成的前裂谷阶段的产物。  相似文献   

3.
银山火山岩次火山岩属于高钾钙碱性系列。化学成分以低Ti、Na,高K和相对富Al为特征。微量元素∑REE较低,K、Rb、Th、U、La、Ce富集和Ti、Ta、Sr、P、Yb相对贫化。从第一旋回到第三旋回,随着SiO2含量降低,Al2O3、FeO、MgO、CaO、Na2O含量以及∑REE、∑Ce/∑Y、(La/Yb)N逐渐升高,岩性由流纹岩流纹英安斑岩英安质熔岩和英安斑岩粗面安山斑岩,表现连续的反序演化。起源于下部地壳的英安质母岩浆同化混染了部分上地壳的硅铝层物质并演化形成以英安质岩浆为主、顶部有一层富SiO2、K的流纹质岩浆、底部有少量粗面安山质岩浆的带状岩浆房。断裂构造诱发岩浆房自上而下逐层抽取喷发—侵位形成反序的火山岩次火山岩。  相似文献   

4.
黔阳隘口基性超基性岩地球化学特征   总被引:4,自引:0,他引:4  
位于华南和扬子两大构造单元接合部位的隘口基性超基性岩及玄武岩,为LREE富集型,并富含Rb、Sr、K、Ti、Zr、U、Th、Ta等大离子亲石元素和不相容元素,具有高的氧同位素组成δ18O为9.58%~11.06%,Isr为0.706294,它们是在稳定的陆壳受到交代作用影响的上地幔经部分熔融形成的。  相似文献   

5.
海南岛中元古代花岗岩地球化学及成因研究   总被引:16,自引:3,他引:16  
海南岛中元古代花岗岩岩体主要由二长花岗岩、花岗冈长岩等岩石组成,构成一个明显的 自花岗岩向花岗闪长岩和英云闪长岩的岩浆演化系列及钙碱性演化趋势。该岩体为一套板块碰撞 后隆起期原地一半原地过铝质花岗岩。是板块碰撞引起的地壳增厚升温和随之的玄武岩浆底侵加 热联合作用下,主要由抱板群变质沉积岩及斜长角闪片麻岩部分融熔、并在幔源物质的参与下形 成的,所形成的花岗质岩浆在“走滑扩容泵吸”机制驱动下沿戈枕剪切带上升、固结就位,因而具壳 幔二元混合成因特点。化学成分以高 SiO2、K2O、Rb、Ba、Ta、Ce和贫P、Ti、Zr、Sr、Fe2O3+FeO、 MgO、CaO为特征;元素比值Zr/Nb、La/Nb、Ba/Nb、Rb/Nb、K/Nb、Ba/La及Cr、Co、Ni、V均接近 大陆中下地壳成分,Rb、Sr、Ba、Ta、Zr及比值K/Sr、Rb/Sr石r/Ba变化范围小,反映岩浆源区成分 或熔融方式上的一致性;轻重稀土较强分馏,负铕异常明显,稀土配分模式总体相似,呈左高右低 型,和抱板群变质沉积岩稀上元素组成基本一致;εNd(t)值普遍高于抱板群地层,(87Sr/86Sr)i值变化 大,暗示幔源参与信息。结合抱板群变基性火山岩的  相似文献   

6.
大兴安岭中生代伸展造山过程中的岩浆作用   总被引:110,自引:6,他引:104  
概括地介绍了大兴安岭中生代伸展造山过程,重点讨论了晚中生代火山岩、深成岩的岩石学及同位素地球化学特征:存在一套板内拉张环境下的A 型花岗岩,火山岩为一套钾质粗面质岩石,大多数花岗岩和火山岩具有低的N(87Sr)/ N(86Sr) 值(0704 ~0708) 和正的ε(Nd ,t) (1 ~4) 值,据此认为这是底侵作用形成的一套壳 幔混熔岩浆的产物,结合岩浆喷发与侵位过程中的伸展构造分析,认为这是大陆内部伸展造山的重要证据。此外,笔者还在该区发现早中生代的一套幔源镁铁质堆晶岩和侵入岩、早 中侏罗世及早白垩世的基性岩墙群、早白垩世(130 ~120 Ma) 超基性的角闪岩、玻基橄辉岩和碱性橄榄玄武岩。由此可以证明,大兴安岭晚中生代的花岗岩 火山岩活动只是伸展背景下的岩浆演化的一个阶段。  相似文献   

7.
陆壳垂向增生的两种方式:以大兴安岭为例   总被引:35,自引:13,他引:22  
邵济安  韩庆军 《岩石学报》1999,15(4):600-606
本文讨论了大兴安岭由于中生代底侵作用形成的两种类型的陆壳增生方式: 1) 来自地壳底部壳幔混源岩浆房的花岗岩和火山岩对上部陆壳的增生, 岩浆的侵位和喷发集中在145~115 Ma, 它们具明显的幔源岩石同位素特征, 如正的εNd (t)值(0~4),低的87Sr/86 Sr 初始比值(0.704~0.708)等; 2)早中生代形成的镁铁-超镁铁质堆晶岩(241~214 Ma)对下部陆壳的增生。  相似文献   

8.
大兴安岭北部中生代火山岩特征及岩浆演化   总被引:12,自引:0,他引:12  
据火山岩岩石组合、地球化学特征、喷发旋回特征及岩浆来源,将大兴安岭北部中生代火山岩划分为三个岩浆演化旋回。晚侏罗世塔木兰沟—吉祥峰旋回火山岩为碱性系列亚碱性系列,岩浆来源于上地幔并有陆壳物质的混染;早白垩世的上库力旋回火山岩为高钾钙碱性系列,岩浆来源于地壳的部分熔融;早白垩世伊列克得旋回火山岩为碱性到亚碱性过渡系列,岩浆来自于地幔并受地壳的混染。综合研究表明,大兴安岭北部中生代火山岩形成于板内环境,早白垩世火山岩可能形成于大陆裂谷环境。  相似文献   

9.
李水龙  王灿 《福建地质》1994,13(1):37-43
近年来的最新调研成果表明,闽北酉部原划为上侏罗统南园组的火山岩为一套中性—偏碱性—酸性—偏碱性火山岩组合,形成于大陆边缘拉张构造环境,岩浆来源于地壳,与萤石、叶蜡石、铌钽、放射性矿产关系密切。全岩Rb-Sr等时线年龄112—142Ma,87Sr/86Sr为0.70661-0.71941,时代为早白垩世。具有一定的区域范围及独特的构造环境,与江西广丰鹅湖岭组相连,而与福建东部的火山岩有很大差异,建议单独建立一个岩石地层单位──中墩组(K1z)。这对研究福建西部乃至我国东部中生代火山岩地层都有重要意义。  相似文献   

10.
张宏飞  骆庭川 《地球科学》1994,19(2):219-226
对扬子克拉通北缘新古代岛弧花岗岩类成分极性的地球化学研究表明,在SiO2含量相近的条件下,由北向南岩石中K2O、K2O+Na2O,K2O/Na2O逐渐增加,而CaO逐渐降低;从北向南,微量元素Rb,Ba,Th,Zr,Nb,Ta,ΣREE及Rb/Th,Rb/Nb,ΣLREE/ΣHREE(La/Yb)N等逐渐增加或具增加趋势,而Sr,Co,Ni和Sr/Ba具逐渐降低或具降低趋势;同位素组成成由北向南δ  相似文献   

11.
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   

12.
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   

13.
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   

14.
塘口水电站大坝基础座落在断层和裂隙较发育的龟裂纹灰岩上,岩体完整性差、透水性强,多年运行后,大坝灌浆廊道和排水廊道出现多处集中性漏水,为确保大坝安全和电站正常发电,根据渗漏性质和成因,采用对灌浆廊道补充帷幕灌浆,对排水廊道进行固结+帷幕+回填灌浆。通过灌浆处理后,效果良好,表明灌浆工程有效的将导致坝基渗漏的上下游的裂隙通道封闭,并顺利的经受了随后的汛期洪水考验,大坝安全得到保障。  相似文献   

15.
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   

16.
In reservoir characterization, the covariance is often used to describe the spatial correlation and variation in rock properties or the uncertainty in rock properties. The inverse of the covariance, on the other hand, is seldom discussed in geostatistics. In this paper, I show that the inverse is required for simulation and estimation of Gaussian random fields, and that it can be identified with the differential operator in regularized inverse theory. Unfortunately, because the covariance matrix for parameters in reservoir models can be extremely large, calculation of the inverse can be a problem. In this paper, I discuss four methods of calculating the inverse of the covariance, two of which are analytical, and two of which are purely numerical. By taking advantage of the assumed stationarity of the covariance, none of the methods require inversion of the full covariance matrix.  相似文献   

17.
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   

18.
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   

19.
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   

20.
正Artemia cysts are an extremely important component of aquaculture diets.It is well established that the cultivation of fish and shellfish derive substantial health and growth advantages when Artemia are included in the diets of the  相似文献   

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