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白乃庙群岛弧火山岩分布于兴蒙造山带南缘,是古亚洲洋与华北板块之间早古生代俯冲作用的岩浆记录,但以往工
作多集中在西段而较少关注其东延部分。本文对白乃庙岛弧带东段新识别出的早古生代火山岩进行了系统研究,以完善对
古亚洲洋早古生代演化的认识。白乃庙岛弧东段火山岩包括中-基性及酸性两种岩石类型,火山岩均富Cs,Rb,Th,U,
亏损Nb,Ta 等高场强元素,轻稀土富集,具有变化的Eu 异常。地球化学数据显示中-基性火山岩来源于俯冲板片熔体交
代的地幔熔融,并可能有大洋沉积物的加入,而酸性岩浆则来源于流体交代的下地壳。锆石LA-ICP-MS U-Pb 定年表明,
酸性及中-基性火山岩形成年代分别为430.5 Ma 和417.6 Ma,前者产出于俯冲岛弧环境,后者则可能为造山后环境下形成
的滞后型弧岩浆岩。年龄数据对比显示东段火山岩的形成年代晚于西段的白乃庙群地层,同时构造变质程度也更低,两者
的这种差异反映了东西两侧地质演化历史的不同,即早古生代古亚洲洋自西向东逐渐关闭。 相似文献
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内蒙古白乃庙逆冲推覆构造的组成及其构造特征 总被引：4，自引：0，他引：4
地层对比结果显示,白乃庙地区发育在古生界之上并与其呈构造接触的地层为中新元古界白云鄂博群哈拉霍圪特组和白音宝拉格组。经过详细的野外观察和构造剖面测量可知,自南向北的逆冲推覆作用将白云鄂博群由华北克拉通北缘推覆至兴蒙造山带南缘的白乃庙岛弧岩带内,进而形成白乃庙逆冲推覆构造。根据逆冲断层、飞来峰与下盘地层、岩体的时代及相互关系,推断该逆冲推覆构造向NNW方向推覆7～15 km,形成于晚二叠世至早三叠世,是古亚洲洋闭合后陆陆碰撞作用在陆缘的响应。该逆冲推覆构造的发现和研究对于进一步了解白乃庙地区陆陆碰撞的过程具有重要意义。 相似文献
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内蒙古白乃庙铜矿床的成矿时代—来自SHRIMP锆石U-Pb和辉钼矿Re-Os年龄的新证据 总被引：3，自引：0，他引：3
摘要：内蒙古白乃庙铜矿床位于兴蒙造山系满都拉-霍林郭勒弧盆系白乃庙早古生代岛弧内,该矿床包括南、北两个矿带,南矿带矿体产于白乃庙组绿片岩中,北矿带矿体产于花岗闪长斑岩内,对于该矿床及白乃庙组的形成时代争议较大。本文采用锆石SHRIMP U-Pb同位素定年获得了白乃庙组第三岩性段绿泥斜长片岩的形成年龄为439.8±6.7Ma,花岗闪长斑岩的形成年龄为433.9±2.2Ma、451.8±3.0Ma,采用辉钼矿Re-Os同位素分析获得辉钼矿的形成年龄为433.9±3.1Ma。结合前人成果,提出白乃庙组地层和花岗闪长斑岩的成岩时代与白乃庙铜矿的成矿时代均为晚奥陶-早志留世,它们同属加里东期构造-岩浆作用的产物。
关键词：绿泥斜长片岩;花岗闪长斑岩;锆石SHRIMP U-Pb年龄;辉钼矿Re-Os同位素年龄;白乃庙铜矿 相似文献
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内蒙古赤峰地区晚古生代A型花岗岩锆石U-Pb年龄及构造意义 总被引：6，自引：0，他引：6
内蒙古赤峰地区主体位于华北克拉通北缘的白乃庙岛弧带内。本文对赤峰北部的红庙子正长花岗岩和鸡冠山花岗斑岩进行研究,结果表明:两种岩体均显示出高硅、富钾、贫镁、低钙的特点,SiO2含量介于72.77%~76.80%之间,K2O含量为4.30%~5.38%,MgO和CaO的含量分别为0.09%~0.21%和0.21%~0.56%。样品Al2O3含量较高,变化于12.49%~13.54%之间,铝饱和指数A/CNK介于1.09~1.29之间,104×Ga/Al平均值为2.68(2.6),显示出红庙子正长花岗岩为I型向A型花岗岩过渡的岩石类型,更趋近于铝质A型花岗岩,鸡冠山花岗斑岩属于典型的铝质A型花岗岩;锆石LA-ICP-MS U-Pb年龄分别为392.0±2.5Ma(正长花岗岩)和377.4±1.6Ma(花岗斑岩),属于晚古生代。兴蒙造山带内目前存在大量的印支—燕山期花岗岩,此次晚古生代侵入体的发现揭示了兴蒙造山带是一个从晚古生代就存在的多期次、多阶段形成的复合造山带。结合区域地质和地球化学特征,岩体形成于白乃庙岛弧与华北克拉通北缘碰撞后的伸展环境。测试结果不仅是研究区白乃庙岛弧岩带内首个精确同位素年龄,也为白乃庙岛弧和华北克拉通的碰撞结束时间为早泥盆世提供证据。 相似文献
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白乃庙岛弧带位于华北克拉通北缘,其与华北克拉通北缘的拼贴时限,是理解华北克拉通北缘增生过程的关键.为了限定弧-陆碰撞的时限,对白乃庙岛弧与华北克拉通拼合带的早古生代沉积地层——查干哈布组开展了锆石U-Pb定年和锆石Lu-Hf同位素测试.结果显示,查干哈布组中3颗最年轻锆石的加权平均年龄为393.5±4.9Ma.综合锆石年龄和前人化石资料,限定查干哈布组最大沉积年龄为早泥盆世晚期.碎屑锆石U-Pb年龄谱和Hf同位素组成显示查干哈布组的物源为白乃庙岛弧带,基本没有来自华北克拉通的物源.研究结果结合区域资料表明,白乃庙岛弧带与华北克拉通北缘在早泥盆世可能仍未发生弧-陆碰撞. 相似文献
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内蒙古白乃庙铜矿床辉钼矿铼锇同位素定年及其地质意义 总被引：2，自引：0，他引：2
内蒙古白乃庙铜矿床位于兴蒙造山带温都尔庙加里东增生带铜多金属成矿带。矿床包括南北两个矿带,南矿带矿体产于白乃庙组绿片岩中;北矿带矿体主要产于花岗闪长斑岩体内,其成矿作用复杂,矿床成因争议较大。采用铼锇同位素定年法对矿区的7件辉钼矿单矿物样品进行分析,所获铼锇同位素模式年龄变化范围为(439.6±6.4)~(450.0±6.6) Ma,加权平均值为(446.5±3.5) Ma,获得等时线年龄为(451.2±3.5) Ma,MSWD值为1.3。结合矿床地质特征分析,认为白乃庙铜矿床是在原始喷流沉积作用形成矿源层基础上,经加里东期岛弧花岗闪长斑岩成矿作用形成,矿床成因应属多期叠加成矿。 相似文献
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内蒙古白乃庙逆冲推覆构造特征及其地质意义 总被引：1，自引：0，他引：1
白乃庙逆冲推覆构造自四子王旗北东的十二台向东经白乃庙、博日和延至化德地区,大致沿北纬42°线东西向延伸超过190 km。它发育于华北克拉通与其北侧的奥陶纪白乃庙岛弧带之间,成为华北克拉通与北缘增生带的构造界线,是一套较为典型的陆缘褶冲带。它表现为华北克拉通北缘的中-新元古界白云鄂博群向北逆冲于白乃庙群及其弧后盆地的上志留统徐尼乌苏组和顶志留统西别河组之上。根据构造变形解析并结合音频大地电磁测深资料(CSAMT),得出白乃庙逆冲推覆构造由一系列分支逆断层组成,并向深部于120~800 m处交汇成主底板断层,构成一套叠瓦式逆冲推覆构造,并发育规模不同的构造窗和飞来峰。根据构造窗与飞来峰之间的距离,提出逆冲位移量大于14 km。通过线理及褶皱枢纽统计,指出白乃庙逆冲推覆构造的逆冲方向为自南向北。依据逆冲岩席中发育的断夹块的叠置关系及构造岩的特征,认为其经历了两个期次的活动。对断裂带内同构造形成的包裹石英透镜体的白云母分别进行了Rb-Sr和Ar-Ar同位素测年,认为白乃庙逆冲推覆构造早期活动于450~410 Ma,是白乃庙岛弧带与华北板块碰撞的构造反映。白乃庙逆冲断层晚期活动于晚二叠世至早三叠世,是古亚洲洋最终闭合的构造表现,亦印证研究区经历了印支期构造运动。 相似文献
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措勤盆地林子宗群火山岩地球化学特征 总被引：7，自引：0，他引：7
青藏高原措勤盆地新生代火山活动十分强烈,以古近纪林子宗群火山岩为代表,主要分布在盆地中央隆起带的冈底斯构造岩浆岩带中,在北部坳陷带中仅有零星分布。林子宗群火山岩主要由安山岩、流纹岩、中酸性熔岩和火山碎屑岩组成。岩石化学研究表明属钙碱－高钾钙碱系列;岩石地球化学研究表明,木子宗群火山岩具岛弧火山岩特点,为喜马拉雅板片与冈底斯－念青唐古拉板片碰撞作用的产物。 相似文献
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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
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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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
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The experimental variogram computed in the usual way by the method of moments and the Haar wavelet transform are similar in that they filter data and yield informative summaries that may be interpreted. The variogram filters out constant values; wavelets can filter variation at several spatial scales and thereby provide a richer repertoire for analysis and demand no assumptions other than that of finite variance. This paper compares the two functions, identifying that part of the Haar wavelet transform that gives it its advantages. It goes on to show that the generalized variogram of order k=1, 2, and 3 filters linear, quadratic, and cubic polynomials from the data, respectively, which correspond with more complex wavelets in Daubechies's family. The additional filter coefficients of the latter can reveal features of the data that are not evident in its usual form. Three examples in which data recorded at regular intervals on transects are analyzed illustrate the extended form of the variogram. The apparent periodicity of gilgais in Australia seems to be accentuated as filter coefficients are added, but otherwise the analysis provides no new insight. Analysis of hyerpsectral data with a strong linear trend showed that the wavelet-based variograms filtered it out. Adding filter coefficients in the analysis of the topsoil across the Jurassic scarplands of England changed the upper bound of the variogram; it then resembled the within-class variogram computed by the method of moments. To elucidate these results, we simulated several series of data to represent a random process with values fluctuating about a mean, data with long-range linear trend, data with local trend, and data with stepped transitions. The results suggest that the wavelet variogram can filter out the effects of long-range trend, but not local trend, and of transitions from one class to another, as across boundaries. 相似文献
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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
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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
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南海位于印度板块、欧亚板块和太平洋板块之间,是世界上最大的边缘海,其构造位置处于太平洋构造域和特提斯构造域,地质构造复杂.关于南海形成演化的动力学机制存在有多种不同观点,其中最重要的一个观点是印度板块与欧亚板块的碰撞致使华南地块和印支地块地幔物质沿东南方向蠕动,从而导致南海的海底扩张.从特提斯的演化规律,以及新特提斯的闭合过程来看,南海并不是特提斯洋的残留海,而是新特提斯在闭合过程中配合印度板块与欧亚板块碰撞导致华南地块和印支地块地幔物质东南方向蠕动的动力学机制下,在南海重新活化的结果. 相似文献
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E. M. Korobova 《Geochemistry International》2017,55(13):1205-1282
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:
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
- — 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.