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1.
通过对中祁连东段黑龙二长花岗岩开展详细的年代学、岩石地球化学的分析测试和研究工作。LA-ICP-MS锆石U-Pb测年表明,黑龙二长花岗岩(206)Pb/(206)Pb/(238)U的加权平均年龄为(481.3±3.7)Ma(MSWD=4.6),属于早奥陶世。岩石地球化学的特征表明,黑龙二长花岗岩属于高碱钙碱性的I型花岗岩,岩石为准铝质-过铝质类型(A/CNK=0.91~1.22)。该二长花岗岩相对富集Rb、Th、U等大离子亲石元素,而相对亏损Nb、Ta、Ti等高场强元素,并且明显亏损P,显示出岛弧岩浆岩的信息。结合区域构造特征,认为黑龙二长花岗岩形成于活动大陆边缘弧的构造环境,同时,也佐证了北祁连洋盆双向俯冲的地质事实。  相似文献   

2.
通过对中祁连东段黑龙二长花岗岩开展详细的年代学、岩石地球化学的分析测试和研究工作。LA-ICP-MS锆石U-Pb测年表明,黑龙二长花岗岩~(206)Pb/~(238)U的加权平均年龄为(481.3±3.7)Ma(MSWD=4.6),属于早奥陶世。岩石地球化学的特征表明,黑龙二长花岗岩属于高碱钙碱性的I型花岗岩,岩石为准铝质-过铝质类型(A/CNK=0.91~1.22)。该二长花岗岩相对富集Rb、Th、U等大离子亲石元素,而相对亏损Nb、Ta、Ti等高场强元素,并且明显亏损P,显示出岛弧岩浆岩的信息。结合区域构造特征,认为黑龙二长花岗岩形成于活动大陆边缘弧的构造环境,同时,也佐证了北祁连洋盆双向俯冲的地质事实。  相似文献   

3.
南祁连北缘东段刚察大寺花岗岩的形成时代和成因一直存在争议。本文对其进行了锆石LA-ICP-MS U-Pb年代学和岩石地球化学研究,进而约束其岩石成因和形成的构造背景。结果表明,刚察大寺花岗岩主要由花岗闪长岩和黑云母二长花岗岩组成;花岗闪长岩中锆石自形程度较好,阴极发光图像显示振荡生长环带,具有较高的Th/U比值(0.27~0.91),表明其为岩浆成因;最小一组岩浆锆石的206Pb/238U加权平均年龄为(435±4)Ma,即岩体形成于早志留世;花岗闪长岩和黑云母二长花岗岩具有类似的地球化学属性,主量元素具有高硅、富碱、富铝和贫镁的特征,其Si O2=65.52%~74.23%、(K2O+Na2O)=6.95%~8.24%、Al2O3=12.33%~15.26%、Mg O=0.31%~1.32%,A/CNK介于0.85~1.05之间,为准铝质-弱过铝质的亚碱性系列岩石;整体富集轻稀土元素和大离子亲石元素(Rb、Ba、K)、亏损重稀土元素和高场强元素(Nb、Ta),具有Eu的负异常(δEu=0.51~0.80)和Sr、P、Ti的明显亏损。南祁连北缘东段刚察大寺花岗岩为I型花岗岩,起源于高温低压条件下中、上地壳物质的部分熔融,结合区域构造演化暗示,刚察大寺早志留世花岗岩形成于活动大陆边缘的构造背景。  相似文献   

4.
中祁连东段什川杂岩基的岩石化学特征及年代学研究   总被引:5,自引:4,他引:1  
祁连造山带被托菜南山-了高山构造带及宗务隆山-贵得构造带分为北祁连、中祁连及南祁连构造带。什川岩基位于中祁连构造带东部,由闪长岩、斜长花岗岩、二长花岗岩组成;对二长花岗岩进行U-Pb单颗粒锆石微区LA-ICP-MS同位素测定,获得444.6Ma及414.3Ma两组加权平均年龄,前者代表岩石的形成年龄,后者代表构造热事件年龄。二长花岗岩主量元素W(SiO_2)=68.66%~80.77%,w(K_2O)/w(Na_2O)>1和A/CNK介于0.95~1.21间,总体为钾质钙碱性过铝质花岗岩。岩石富集LILE元素(K、Th、Rb、Ba等),亏损HFSE元素(Ta、Nb、Y等);稀土元素总量较高(∑REE多介于109.05×10~(-6)~322.66×10~(-6)),轻重稀土强烈分馏(∑LREE/∑HREE介于7.92~31.68),稀土元素分配模式为轻稀土富集型,具中等-强Eu负异常(δEu=0.26~0.58)。岩石矿物组合及岩石地球化学特征共同表明,什川岩基为中上地壳泥砂质岩石部分熔融而成,形成温度较低,为加厚地壳拆沉熔融成因。这为祁连造山带构造演化及其深部动力学机制研究提供了新的资料。  相似文献   

5.
藏东纽多黑云母二长花岗岩锆石U-Pb年龄及成因   总被引:2,自引:2,他引:0  
通过对澜沧江北段卡贡地区出露的纽多黑云母二长花岗岩的岩石学、岩石地球化学及锆石U-Pb年龄的研究,分析了纽多黑云母二长花岗岩的地球化学和原岩特征。黑云母二长花岗岩中的锆石具有明显的振荡环带,较高的Th/U值(普遍大于0.4),属于典型的岩浆成因锆石,用LA-ICP-MS测得锆石~(206)Pb/~(238)U年龄为243.6±1.4Ma(MSWD=1.00,n=15),时代为中三叠世。岩石地球化学特征表明,该黑云母二长花岗岩具有较高的SiO_2、Al_2O_3及高钾富碱的特征,A/CNK值为1.05~1.08,为过铝质高钾钙碱性系列;稀土元素配分模式显示,配分曲线为右倾型,具有明显的负Eu异常和弱负Ce异常,表现为Nb、Ta、P、Zr、Ti等高场强元素相对亏损,相对富集Rb、K、Th、U等大离子亲石元素。岩石地球化学特征表明,纽多黑云母二长花岗岩为S型花岗岩,形成于地壳加厚增温环境下的深熔作用。  相似文献   

6.
野马山岩基位于中祁连地块西段,由早期岩体(花岗闪长岩、斑状二长花岗岩)和晚期岩体(二长花岗岩)组成,二者呈侵入接触。LA-ICPMS锆石U-Pb定年表明,早期岩体侵位时代为中奥陶世((469.0±1.3)Ma),晚期岩体侵位时代为晚奥陶世((450.0±1.0)Ma)。早期岩体Si O2=59.8%~64.2%,K2O/Na2O1,且A/NKC=0.8~1.0,为准铝质岩石;微量元素相对富集Rb、U、Th和亏损Ba、Nb、Ta、Sr、P、Ti;稀土总量为97.7×10-6~185×10-6,且(La/Yb)N=5.57~12.47,LREE/HREE=7.7~11.3,具轻重稀土分馏明显,轻稀土富集,弱Eu负异常(δEu=0.66~0.89)特征。晚期岩体Si O2=69.8%~76.5%、K2O/Na2O=1.2~1.7、A/NKC=1.0~1.1,属弱过铝质花岗岩;稀土总量为78.97×10-6~244.92×10-6,轻重稀土分馏不明显((La/Yb)N=1.90~5.72),强Eu负异常(δEu=0.11~0.24)。岩石地球化学特征表明,野马山岩基早期岩体为I型花岗岩,形成于俯冲环境,晚期岩体为高分异的I型花岗岩,形成于后碰撞环境。结合岩体产出的区域构造位置及区域地质演化,认为早古生代北祁连洋发生了双向俯冲,野马山岩基为其向南俯冲碰撞的产物。  相似文献   

7.
位于南祁连化隆地区的鲁满山花岗岩体,岩石类型主体为黑云二长花岗岩。LA-ICP-MS锆石U-Pb定年测得其成岩年龄为(452.9±1.8)Ma,属于加里东期岩浆活动的产物。化学组成上,岩体具有高硅、富碱的特征,属于弱过铝质高钾钙碱性系列。微量和稀土元素组成上,岩体富集大离子亲石元素Rb、U、Th、K和Pb,亏损Ba、Sr、Ta、Nb、P、Ti,具明显轻稀土富集,重稀土亏损特征,显示较强烈的负Eu异常(δEu=0.06~0.55,平均0.31),综合地质地球化学资料指示该岩体应属于高分异的Ⅰ型花岗岩。锆石Hf同位素分析结果显示,岩体的εHf(t)为-7.4~0.1,二阶段模式年龄介于1425~1930 Ma,指示成岩过程中应有亏损地幔组分参与,其壳源源区很可能包括化隆岩群。结合区域构造演化,认为鲁满山花岗岩体形成于柴北缘洋壳与中南祁连陆壳俯冲碰撞的地球动力学背景下,由幔源岩浆与其诱发的地壳物质熔融产生的长英质岩浆在地壳深部混合后再经历分异演化形成。  相似文献   

8.
青海塔塔棱河中上游地区花岗岩类主要岩石类型为斑状二长花岗岩、二长花岗岩、花岗斑岩和斑状正长花岗岩,其次为正长花岗岩、环斑花岗岩、花岗闪长斑岩和石英闪长岩。岩石地球化学研究表明,该区花岗岩具有过铝质(A/CNK值为1.10~1.26)、高钾(K_2ONa_2O)特征,属于钙碱性系列(σ为1.22~2.22),具S型花岗岩特征。LA-MC-ICP-MS锆石U-Pb测定结果,显示该区花岗岩年龄为(440.4±1.4)Ma。构造环境判别形成于后碰撞构造环境。综合分析后认为,早志留世花岗岩应当是陆陆汇聚时,南祁连陆块发生俯冲,与全吉地块发生碰撞,南祁连地块遭受挤压导致陆壳部分熔融而形成的产物。  相似文献   

9.
对藏东地区浪拉山糜棱岩化二长花岗岩进行了LA-ICP-MS锆石U-Pb年龄测试,获得了该岩体的206Pb/238 U年龄加权平均值为470.5 Ma±3.7 Ma(MSWD=1.7,n=15),属于中奥陶世的产物。岩石地球化学特征表明,岩石具有高钾(Na2O/K2O=13.12~162.89)、铝(A/CNK值平均为1.30)、低钛的特征,岩石属于高钾钙碱性过铝质S型花岗岩。岩石具有明显Eu负异常,表现为Nb,Sr,P、Ti等高场强元素相对亏损,相对富集K,Rb,Th,U等大离子亲石元素,具有岛弧型花岗岩的特征。结合区域地质资料分析,该岩体与区内原特提斯洋的俯冲存在成因联系,藏东地区浪拉山糜棱岩化二长花岗岩的发现有助于进一步探索原特提斯洋演化过程。  相似文献   

10.
中南祁连西缘三个洼塘附近花岗质岩石由花岗岩、石英闪长岩和花岗闪长岩构成。LA-ICP-MS锆石U-Pb年龄测定结果表明,花岗岩、石英闪长岩和花岗闪长岩侵位年龄分别为416.7±4.3Ma(MSWD=0.52)、442.5±4.7Ma(MSWD=0.46)和443.9±1.3Ma(MSWD=0.17),指示本区发生了两期岩浆活动事件。花岗质岩石均表现为过铝质,花岗岩高钾、K/Na,低Mg、Fe、Ca的主量元素特征,富集高场强元素,亏损大离子亲石元素,∑REE为122.0×10-6,δEu为0.05,具明显负铕异常。花岗闪长岩和石英闪长岩多数富钠,高场强元素含量相对花岗岩较低,而大离子亲石元素含量相对花岗岩略高,∑REE为133.3×10-6~247.6×10-6,δEu为0.73~1.09,铕异常特征不明显。综合研究表明,本区花岗岩可能属于造山活动结束后伸展环境下地壳物质部分熔融形成的A型花岗岩,花岗闪长岩和石英闪长岩则可能属于洋壳俯冲环境下引起岛弧岩浆活动而形成的I型花岗岩,这一成果对于研究中南祁连的构造演化有着重要意义。  相似文献   

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南秦岭下地壳组成及岩石圈的拆离俯冲作用   总被引:3,自引:3,他引:3       下载免费PDF全文
根据新提供的Pb同位素组成及岩石地球化学研究成果,本文进一步证实了位于北秦岭北界的明港地区发育的早中生代安山玄武质火山角砾岩岩筒所携带的下地壳捕虏体属于南秦岭。所恢复的南秦岭下地壳剖面自下而上为:底侵成因的变辉长岩-基性麻粒岩(其中含有榴辉岩及辉石岩的透镜体)-酸性麻粒岩。秦岭造山带总体的岩石因模型为:南秦岭(扬子块体)向北拆离俯冲,北秦岭地壳向华北仰冲,华北岩石因呈楔状插入秦岭造山带,拆离面约在中、下地壳之间。南秦岭俯冲岩片延伸的范围在平面上有可能达到400km。  相似文献   

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青藏高原综合观测研究站的回顾与展望   总被引:1,自引:1,他引:0  
赵林  郭东信 《冰川冻土》1998,20(3):287-292
中国科学院青藏高原综合观测研究站从1988年建站到1998年以来,在各个方面均取得了长足的发展,横向生产性项目的开展和完成不仅解决了部队和地方的实际问题,而且缓和了观测研究站在运行过程中所面临的经费严重不足的问题,同时也为我所冻土专业研究人员提供了在生产中实践的机会,在基础理论研究方面,承担了国家攀登计划项目,国家基金项目,中国科学院重点项目和中国科学院冰冻圈专项项目等的研究工作,在多年冻土变化,  相似文献   

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In his last lifetime essay, “A Few Words about the Noosphere”, Academician V.I. Vernadsky (1944) wrote that all living organisms on the planet, including man, are integral to the biosphere of the Earth, its material and energy structure and cannot be physically independent of it even for a minute. However, the substrate that generates all living beings and is no less tightly bound to the biosphere has always been characterized by a significant geochemical heterogeneity, traced both in the vertical and in the lateral structure of all geospheres.
The present work is devoted to three most important aspects of modern geochemistry and biogeochemistry:
  • — evolution of the ecological and geochemical state of the environment under conditions of a virgin (anthropogenically untouched) biosphere;
  • — structural features of the geochemical organization of the modern noosphere;
  • — specificity of the interaction of living matter with the environment under increasing anthropogenic load.
On the basis of theoretical concepts of biogeochemistry and geochemical ecology, formulated in the works of V.I. Vernadsky, A.P. Vinogradov, A.E. Fersman, B.B. Polynov, A.I. Perel’man, M.A. Glazovskaya, V.V. Kovalsky, E. Odum, B. Commoner, E.I. Kolchinskii and others, the author puts forward a hypothesis that there exist two qualitatively different stages in the evolution of the biosphere.The first stage is recognized as the period of natural evolution of the biosphere during which it evolves successively into a more complex and more biogeochemically specialized object. In the course of the geological time, this constantly results, on the one hand, in an increase in species diversity and the perfection of individual species, and, on the other hand, to directed improvement and a greater differentiation of the geochemical conditions of the environment. At this stage, the evolution of all systems of the biosphere that were controlled by the mechanisms of self-organization and self-regulation resulted in the establishment of a dynamic equilibrium, which was responsible for the cycling of all essential chemical elements and therefore providing ecologically optimal geochemical conditions in all ecological niches and for all species and biocenoses inhabiting the biosphere at any given moment.The beginning of the second stage is related to the appearance of reason and qualitative changes in the biosphere caused by the goal-directed activity of the human mind, as an entirely new geological force that appeared to be able not only to disrupt the functioning of natural mechanisms of self-regulation and selforganization, but also to transform the environment in the intersts of a single biological species, Homo sapiens. A direct consequence of this change was the uncontrolled transformation of the natural environment, during which the primary structure (geochemical background) created in the course of billions of years was eventually superimposed by a qualitatively new layer of anthropogenically-derived chemical elements and compounds, thus building an interference pattern of a new geochemical field with which practically all modern living organisms are now forced to interact.An outstanding feature of the new evolutionary stage of the natural environment, called by Vernadsky the noosphere, is that biogeochemical changes at this stage proceed at a rate which exceeds that required for the living matter to adapt to these changes. The result is the disruption of the existing parameters of the biological cycle, leading to the emergence of a significant number of endemic diseases of geochemical nature.The proposed approach was used to prove the anthropogenic genesis of existing geochemical endemic diseases and explain the mechanisms of their appearance. In addition, this approach allowed us to develop a new methodology for mapping zones of ecological and geochemical risk and noticeably simplify the procedure of monitoring distribution and prevention of all diseases of geochemical nature.  相似文献   

17.
共和盆地层状地貌系统与青藏高原隆升及黄河发育   总被引:1,自引:0,他引:1       下载免费PDF全文
利用卫星遥感影像,结合实地调查和测年结果,对共和盆地层状地貌系统进行了解译、分析。研究表明,共和盆地层状地貌系统由山麓剥蚀面、洪积扇面、盆地面以及黄河阶地面构成,其空间结构、物质组成对发生于早更新世早期的青藏运动C幕和中更新世末期的共和运动反映清晰。青藏运动C幕使青藏高原主夷平面在高原差异性隆升中彻底解体,垂直变形量高达1700m。共和运动使黄河在0.11Ma进入共和盆地,其后黄河平均以3.5mm/a的侵蚀速率下切盆地,同时在盆地边部的山前古冲洪积扇以大致相近的速率被抬升,最终导致高差在2000m左右的层状地貌系统的出现。  相似文献   

18.
铀钍的地球化学及对地壳演化和生物进化的影响   总被引:10,自引:2,他引:8  
本文论述了在含挥发份和贫挥发份条件下U、Th的迁移行为及其对地球和行星演化的影响,并阐述了造成地球独特地质演化历史的原因。提出了U、Th在地球中的迁移模式以及该模式对地壳形成、演化的控制作用和对生物发展演化的可能影响。  相似文献   

19.
B. K. Maloney 《GeoJournal》1993,31(4):355-362
While botanists, archaeologists, historians and linguists have contributed to the debate on the origin of the coconut pollen analysts have been silent. This article attempts to integrate the results of recent palaeoecological research with findings from the other disciplines.  相似文献   

20.
The possibility to use some widely known standard discrimination diagrams such as the K2O/Na2O-SiO2/Al2O3, SiO2-K2O/Na2O, (Fe2O3* + MgO)-TiO2, F1-F2, Th-La-Sc, Sc-Th-Zr/10, and Sc/Cr-La/Y for deciphering the paleogeodynamic settings of sedimentary sequences is considered with reference to the Lower and Middle Riphean (Mesoproterozoic) deposits of the Uchur-Maya region (Far East) and the Bashkir meganticlinorium (South Urals). It was shown that only some of them can be used with a certain degree of confidence for reconstructing the settings of the platform sedimentary sequences made up of both sandstones and fine-grained terrigenous rocks.  相似文献   

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