共查询到19条相似文献，搜索用时 218 毫秒
1.
地幔中存在着大量的“水”(存在形式:H2O、H+和(HO)?)已是不争的事实,这些“水”既可以以流体或熔体的形式存在,又可以存在于含水矿物、名义上的无水矿物和致密含水镁硅酸盐中。在本文中,“流体”是指以水为主体包括溶解于水中或随水迁移的元素和化合物。在俯冲带的地震作用、地幔部分熔融、岩浆作用以及海底热液活动等重大地质作用过程中,流体都发挥着重要的作用。俯冲带是水化了的大洋岩石圈板块俯冲进入地球深处的关键部位,也是壳幔相互作用的重要地带。在俯冲带,流体随俯冲的岩石圈板块进入地球深部,部分在挤压和摩擦热的作用下脱逸俯冲的岩石圈板块,连同岩石矿物变质所产生的水进入上覆地幔楔,从而降低上覆地幔物质的熔点,产生岩浆;岩浆上升一方面加热了沿裂隙或物质间隙下渗的海水,另一方面也会因岩浆冷却产生岩浆作用后期热液流体,这些加热的下渗海水和岩浆作用后期流体构成了现代海底热液活动的物质基础;海底热液活动不仅将大量地下元素或物质输入大洋水体从而影响了大洋海水的物质组成及生态环境,而且在海底形成了具有重要经济价值的热液多金属矿体。因此,流体是贯穿板块俯冲及其所产生的各种重要地质作用过程的介质,从而成为研究这些重要地质作用的示踪剂。本文在分析了大洋岩石圈板块俯冲构造背景下流体的主要地质作用过程的基础上,探讨了流体在俯冲带地震发生机制、岩浆作用过程、现代海底热液活动模式及俯冲带流体成矿作用等方面的作用,并进一步提出近期研究工作应主要集中在4个方面:(1)进一步准确地定量评估通过板块俯冲作用进入地球深部的“流体”通量,为最终解决全球地球化学或物质循环问题作出贡献;(2)全面、准确地描述俯冲作用中流体的物理和化学行为,建立俯冲带流体地质作用的理论模型;(3)充分利用现代化的测试分析手段,重点获取矿物原位微区分析、矿物流体包裹体物理化学指标测试、稳定和放射性同位素分析等方面的精细准确数据,用于查明当前取样观测手段无法触及的地下深处物质状态和作用过程;(4)发展数值模拟技术,建立俯冲带流体地质作用的理论模型。 相似文献
2.
青岛C类榴辉岩的岩石学矿物学及其地质意义 总被引：2，自引：0，他引：2
本文利用X荧光光谱定量分析、电子探针分析和X衍射分析对青岛C类榴辉岩作了岩石学、岩石化学和矿物化学研究,计算了青岛C类榴辉岩的成岩温度、压力条件及古地温梯度,最后提出了其成因是早元古代早期华南陆块向华北陆块俯冲时,大洋碱性橄榄玄武岩在低温高压环境发生变质作用形成C类榴辉岩和蓝闪石片岩。早元古代的变质作用使C类榴辉岩平衡温度升高,蓝闪石片岩消失。 相似文献
3.
马里亚纳弧前蛇纹岩泥火山被认为是认识俯冲作用的直接窗口，其发育的角砾状蛇纹岩富含的流体流动性元素（FMEs）记录了引起蛇纹石化作用的流体和俯冲带的流体-岩石相互作用及元素循环等信息。本文整理了马里亚纳弧前物源深度逐渐增加的5座蛇纹岩泥火山（Yinazao、Fantangis?a、Asùt Tesoru、South Chamorro和Conical）发育角砾蛇纹岩的FMEs数据，通过不同泥火山、同一泥火山不同深度样品及同一块状样微区子样品间的FMEs特征对比，分析了蛇纹岩泥火山引起的蛇纹石化作用的流体性质、来源和形成机制。5座蛇纹岩泥火山角砾蛇纹岩的FMEs均较亏损地幔（DM）显示富集特征：B、Cs、As强烈富集（常>100×DM）,Li、Rb、Sb中等富集（>10×DM）,Ba、Sr、Pb弱富集（<10×DM）。浅源泥火山角砾蛇纹岩中B、Sr、Ba、Pb含量最高，且由浅源至深源泥火山其含量呈逐渐减少的趋势。而Li、Rb、Cs、As、Sb含量显示相反特征，浅源泥火山的角砾蛇纹岩中含量最低，且从浅源到深源泥火山其含量逐渐增加。不同泥火山角砾蛇纹岩FMEs具有系统性变化特征... 相似文献
4.
岛弧形成于大洋岩石圈被向下拖曳至仰冲板块之下的地方。人们认为俯冲岩石圈的脱水作用引起地幔熔化 ,造成岛弧上发生火山活动。了解俯冲带下面的物质通量对于研究新大陆壳的形成以及地壳物质返回到对流地幔的再循环的形成极为重要。在流体增量和部分熔融转换过程中表示这些俯冲物质通量特征的主要概念是元素之间的化学分馏。然而 ,需要假定熔融之前大多数地球化学示踪剂在地幔楔中的丰度。相反 ,可以假定Ｕ系衰变链的母子体核素最初处在长期平衡状态 ,从而记录了脱水作用期间和部分熔融过程中产生的分馏净效应和它们的时标。现今研究的 ２… 相似文献
5.
本文报道了胶东—苏北古碰撞带附近存在的高温低压变质的麻粒岩相、高温高压变质的A—B类榴辉岩相和高压低温变质的C类榴辉岩相三种变质相系,以及与高温低压麻粒岩相有关的Ⅰ型花岗岩带,它们在空间上相协调,在时间上相一致。其经历了早元古代早期的华南—华北陆块碰撞事件、早元古代角闪岩相变质事件和早元古代末期大陆推覆构造事件,使得高温低压麻粒岩相岩石发生退变质作用,低温高压C类榴辉岩相岩石发生进变质作用,蓝闪石片岩消失,并导致高温高压的A—B类榴辉岩相和高压低温的C类榴辉岩相在空间上相叠置。 相似文献
6.
利用电子探针等方法研究了青岛榴辉岩相变质古洋壳(蛇纹岩、C类榴辉岩和基性糜棱岩)的岩石学和地球化学特征。确定了它们为华南陆块与华北陆块拼合前的古洋壳,当其俯冲于华北陆块之下时在深部发生碱质交代及低温高压变质作用(C类榴辉岩相)。 相似文献
7.
黄河、辽河和鸭绿江沉积角闪石矿物化学特征对比及物源识别 总被引：4，自引：1，他引：3
通过提取黄河、辽河和鸭绿江表层沉积物中的碎屑矿物角闪石,对单矿物采用电子探针,对群体角闪石采用ICP-MS和ICP-AES分析其常量元素及微量元素组成。结果表明:角闪石单矿物主成分在一定范围内有较大变化,都具有高Si、Ca、Mg和低Na、K的特征;3条河流的角闪石晶体化学都归属钙角闪石组,半数以上矿物种为镁角闪石;角闪石群体矿物化学显示黄河角闪石的稀土元素浓度明显高于黄土和黄河全岩沉积物,而且重稀土比轻稀土更富集,说明角闪石是黄河和黄土沉积物稀土元素的主要载体之一,角闪石含量变化会对全岩样品稀土元素含量造成重要影响。微量元素特征显示新旧黄河样品间差别很小,与其同一来源物质的事实相符。虽然黄河、辽河和鸭绿江河流样品角闪石主成分相近,但微量元素方面(元素含量、元素含量对比值及特征值)显示较明显不同,样品间多种数值指标相对偏差在20%以上,可作为物源识别的判别标志,如微量元素Ba、Li、Rb、Cs、Ta、Tl、Pb、La、Ce、Pr、Nd等含量的差异,元素对比值c(La)/c(Y)、c(Sr)/c(Rb)、c(Zn)/c(Cu)、c(Gd)/c(Cd)、c(Li)/c(Be)、c(Rb)/c(Cs)、c(Sr)/c(Ba)、c(Hf)/c(Ta)、c(Pb)/c(Bi)等的差异;特征值∑c(REE)、Σc(LREE)、∑c(HREE)、∑c(LREE)/∑c(HREE)、[c(La)/c(Lu)]N、[c(La)/c(Yb)]N、[c(La)/c(Sm)]N等的差异。 相似文献
8.
当深度大于５０ｋｍ时 ,高压和高温将抑制脆裂作用的进行 ,然而俯冲带的地震却能在深达６７０ｋｍ处发生。越来越多的证据表明是变质反应触发了这些深部地震的发生。深源地震（＞３００ｋｍ）可能是由与橄榄石转变成尖晶石的亚稳态反应相关的断裂活动引起的 ,中源地震（５０～３００ｋｍ）可能是由俯冲洋壳中与变玄武岩和变辉长岩转变成榴辉岩相关的脱水脆化作用引起的 ,或由俯冲地幔表层中的蛇纹石脱水而引起。即使在俯冲带较浅的范围（＜５０ｋｍ） ,变质反应可能也控制着大的板内地震的震源深度。本文认为蛇纹石脱水作用引发了发生在俯冲… 相似文献
9.
对东马努斯盆地高镁安山岩做了全岩主微量和Sr-Nd-Pb同位素分析,并结合前人测试数据,探究了岩浆物质来源及演化过程。由主量元素[MgO、CaO、FeOT(全铁)、Al_2O_3、TiO_2和P_2O_5]含量随着硅含量的升高而降低和La/Sm随着La含量的升高而保持不变可知,岩浆在演化过程中只发生了矿物的分离结晶,分离的矿物可能为橄榄石、辉石、斜长石、钛铁矿和磷灰石。东马努斯盆地高镁安山岩的Pb和大离子亲石元素(K,Rb,Sr,Ba和U)的富集、高场强元素(Nb,Th,Ta和Ti)的亏损说明岩浆受到了俯冲板块脱水作用的影响。推测该区高镁安山岩是流体交代的地幔楔部分熔融形成的。由Sr-Nd同位素混合模拟结果可知东马努斯盆地高镁安山岩主要来源于马努斯MORB(洋中脊玄武岩),少量来自于太平洋蚀变洋壳和海底沉积物。根据Sr-Nd-Pb同位素特征推测岩浆混合作用发生在地幔源区,属于源区混染,岩浆在喷发的过程中没有发生同化混染作用,也没有加入其他体系的物质。 相似文献
10.
华北东部青岛地区煌斑岩广泛发育,其岩石成因、构造环境等方面研究程度较低。本文通过研究其岩石学和地球化学特征,讨论岩浆的源区性质、形成的构造环境,进而推断研究区的地质演化过程。研究区内煌斑岩的SiO2含量(W(SiO2))为39.13%~51.26%,属于钾玄质碱性岩。样品的稀土元素整体表现出轻稀土元素富集、重稀土元素亏损的特征,Ce和Eu异常(分别用δCe和δEu表示)不显著。样品微量元素总体表现出大离子亲石元素(Ba、K、Pb)和轻稀土元素富集(LREE),而高场强元素(Nb、Ta和Ti)亏损的特征,具有典型的俯冲特征。源区为三叠纪时北向俯冲的扬子板块析出的熔体,交代上覆华北板块地幔橄榄岩而形成的地幔交代岩。白垩纪时,俯冲带岩石圈大范围坍塌,软流圈上涌形成伸展环境,地幔源区发生部分熔融,岩浆上升侵位形成煌斑岩。 相似文献
11.
为了解三亚近岸海域沉积物地球化学特征,测定了331个站位的表层沉积物23种微量元素含量;利用多元统计法进行相关性及R型因子分析,探讨研究区元素的来源、分布特征及其控制因素。微量元素含量测定结果表明,Sr、Ba、Zr、Rb元素平均值比其他元素高;Be、Cr、Co、Ni、Cu、Zn、Cd、Sb、Pb、U、Zr、Ba、Sc、V、Ga等15种元素含量与海南岛水系沉积物、表层土壤、深层土壤接近,推测沉积物主要来自海南岛。各元素在研究区的空间分布比较复杂,在中部和东部,以Li为代表的15种微量元素随离岸距离增加含量增大;Cd、Sb、Zr、Ba、Rb、Sr、As、Hg的分布特征与其他微量元素相比差异明显。Li等15种元素来源与分布主要受陆源黏土矿物吸附作用控制,Sr主要受海洋生源沉积作用的控制,Zr主要受重矿物的控制,Ba和Rb主要受研究区地质背景控制,而Cd和As的来源与分布则与人类活动有关。 相似文献
12.
Fluctuations in lacustrine sedimentary environments significantly affect distributions of organic matter (OM), uranium, and other elements in shales. In this study a high-resolution geochemical record of fluctuations in the paleo-depositional environment of a terrestrial lake basin is provided on the basis of extensive samples collected from the Member 3 of the Paleogene Shahejie Formation (Es3) of the Niu-38 well in the Dongying Depression, Eastern China. These samples were tested for total organic carbon (TOC), element concentrations, and biomarkers to study the evolution and fluctuation in the depositional environments of an ancient lake basin and associated geochemical response. The evolution and fluctuation of the sedimentary environment from a deep lake to a semi-deep lake and then to a shallow lake delta were indicated by geochemical response. During this evolution, the values of TOC, S1, S2, Sr, and Ts/(Ts + Tm) remarkably decreased, whereas those of Co, Ni, Rb, Na, Fe/Mn, Fe/(Ca + Mg), and C29 mortane/C29 hopane significantly increased. The deep lake basin shows depositional fluctuations, as indicated by rock lithofacies and their geochemical parameters. A close interrelationship was observed among U concentration, TOC content, and inorganic element content. Uranium concentrations are positively correlated with TOC contents, Ca and Sr concentrations, and Sr/Ba and Ca/Mg ratios but negatively with K, Na, Ba, and Rb contents and Fe/(Ca + Mg) and Fe/Mn ratios. The observed increase in U concentration in the lower Es3 section is closely related to surface adsorption by clay minerals and OM, together with some replacements of Ca and Sr by U in the shales. 相似文献
13.
FuYongtao LiAnehun 《海洋通报(英文版)》2003,5(2):29-39
The major elements, trace elements, K-Ar age and Sr-Nd-Pb isotopic systems of the Cenozoic volcanic rocks in Daheishan Island and Cishan, Penglai, Shandong Province are measured. The volcanic rocks ( olivine-nephelinite and nepheline-basanite ) in DaheishanIsland erupted periodically in an interval of 0.32 Ma, from 8.72 Mm 8.39 Ma, 8.08 Ma to 7.73Ma. The volcanic rocks are all rich in light REEs. They are similar to the OIB-type alkali basalt in the trace elements normalized model by primordial mantle: rich in high field elements such as Nb and Ta, and imcompatible elements such as Cs, Rb, Ba, Th, U. The volcanic rocks show a depletion of K and Rb elements. It is suggested by the trace elements that the olivine-nephelinite in Daheishan Island is originated fi‘om deep resources under the continental mantle, ε Nd (0) values of the volcanic rocks in Daheishan Island and Cishan are 5.31 - 8.51 and 7.33 respectively, suggesting that the volcanic rocks are from the depleted mantle resources, which have higher Sm/Nd ratios than the CHUR. ^143Nd /^144Nd ratios of Daheishan Island olivine-nephelinite and Cishan alkali basalts are 0.512 910 - 0.513 074 and 0.513 014 resoeetivelv. The ^87Sr /^86Sr of Daheishan lsland volcanic rocks are lower than that of Cishan, 0.703 427 - 0.703 482 and 0.703 895 respectively. The Daheishan Island olivinenephelinite has the Pb isotopic values as follows: ^206Pb /^204pb= 18.028 9 ～17.972 8,^207Pb /^204Pb= 15,435 8 - 15.402 2 and ^208Pb /^204Pb=38.087 6 - 37.997 5, lower than those of Cishan basanite. The Cishan basanite has ^206Pb / ^204Pb = 18.240 1, ^208Pb /^204Pb = 15.564 5 and ^208Pb /^204Pb=38.535. The authors suggest that the olivine-nephelinite in Daheishan Island is similar to the E-type MORB or Hawaii OIB, and the alkali basalts in Cishan similar to the Kerguelen OIB. The dominant mantle components of DM PREMA and perhaps DM( Dupal type ) are the dominant mantle components for volcanic rocks in Daheishan Island and Cishan. The PREMA component plays an important role. 相似文献
14.
在莱州湾南岸的07孔岩心进行高分辨率采样的基础上,采用X荧光光谱法(XRF)、离子质谱法(ICP-MS)以及原子荧光光谱法(AF)等方法测试了研究区07孔的48种常微量元素以及稀土元素的含量,并对元素相对含量、随深度变化规律、特征比值以及稀土元素配分模式进行了研究。结果表明,07孔主要元素及特征比值在海陆地层分界处有明显变化,可以作为地层划分的指标之一。其中,Mn、Mg、Ca、Fe、Mg/Ca及K/Na等对沉积环境响应比较明显,Ba、Zr、Rb、Si/A1、Ti/A1和Rb/Sr对源区的母岩类型、风化程度及搬运距离的变化敏感;07孔常微量元素垂向变化较大,在3次海侵地层中呈明显变化,并对应多个峰值。化学元素的变化规律所反映的地层特征与晚更新世以来的气候和海平面的变化有较好的对应关系。07孔不同深度沉积物的稀土元素球粒陨石标准化配分模式与黄河沉积物的相似,呈轻稀土元素富集的右倾型。说明黄河是莱州湾南岸弥河-潍河多源河流三角洲沉积体系的物源之一,且对莱州湾南岸一定深度范围内的沉积地层有部分贡献。 相似文献
15.
Elemental mass-balance of material carried by major world rivers 总被引：3，自引：0，他引：3
An estimate of average river particulate matter (RPM) composition was bàsed on analyses of more than 40 elements in the Amazon, Congo, Ganges, Magdalena, Mekong, Parana and Orinoco rivers, to which were added literature data for 13 other major world rivers, covering the whole spectrum of morphoclimatic features. Geographic variations of major elements in RPM are mostly linked to weathering types and to the balance between weathering rate and river transport. As a result of chemical erosion, Al, Fe and Ti are enriched in RPM with respect to the average parent rock, while Na, Ca, Mg and Sr are strongly depleted. These figures are directly related to the relative importance of dissolved and particulate transport in rivers; this has been computed for each of 40 elements. In order to study weathering on a global scale, the total observed elemental fluxes (dissolved + particulate) have been computed and compared to theoretical ones. The latter were derived from the elemental content in the average parent rock and the total quantity of weathered material, computed from the Al ratio in RPM and in parent rock. Observed and theoretical fluxes are balanced for the less mobilized elements (rare earths, Co, Cr, Cs, Fe, Mn, Rb, Si, Th, Ti, U and V) for which no enrichment relative to Al is noted in RPM, and for B, Ba, Ca, K, Mg, Na, Sr which are relatively depleted in RPM due to their high dissolved transport. Additional fluxes have been found for Br, Sb, Pb, Cu, Mo, Zn and are possible also for Ni and P. This is reflected by marked enrichments in RPM relative to Al for the poorly or moderately dissolved transports (Pb, Cu, Zn). Several hypotheses involving either the natural origin (volcanic dust, marine aerosols, geochemical fractionation) or the artificial origin (worldwide pollution) are discussed to explain these discrepancies, assuming river transport and weathering either to be in a steady state on a global scale or not. However, none of them can fully account for these additional fluxes. It is most likely that these excesses have multiple origins, anthropogenic or natural or both. The comparison between RPM and deep-sea clay compositions emphasizes the prime influence of river input on oceanic sedimentation of Si, Al, Fe, Ti, lanthanides, Sc, Rb, V, etc. A few elements such as Zn, Sb, occur in excess in RPM as compared to deep-sea clays; in order to balance this excess, a remobilization of these elements out of the sediment can be considered. Finally, the enrichment of Co, Cu, Mn and Ni in deep-sea clays compared to RPM is discussed and attributed to several sources and processes. 相似文献
16.
Ling Chen Limei Tang Jichao Yang Xiaohu Li Wei Wang Fengyou Chu Jie Zhang 《海洋学报(英文版)》2021,40(11):147-161
We present major and trace element data of lava recovered from the northern Yap Trench in the western Pacific and discuss their petrogenesis and tectonic implications within the framework of interactions between the Caroline Ridge and Yap Trench. Rocks were collected from both landward and seaward trench slopes and exhibited geochemical characteristics similar to backarc basin basalt (BABB) and mid-ocean ridge basalt (MORB), including high Fe content, tholeiitic affinity, high TiO2 value at a given FeOT/MgO ratio, Ti/V ratio between 20 and 50, low Ba/Nb ratio and Th/Nb ratio, and trace element patterns commonly displayed by BABB and MORB, which are distinct from arc lava. These rocks seem to have been generated during mantle upwelling and decompression melting at a spreading center. However, compared with typical forearc lava produced by seafloor spreading in the Mariana forearc region, such as the early Eocene forearc basalts and late Neogene forearc lava in the southernmost Mariana Trench, the Yap Trench lava is derived from a more fertile mantle and feature a more minor subduction component; thus, they cannot be the products of forearc mantle decompression melting. We suggest that the landward slope lava represents backarc basin crust that was overthrust onto the forearc lithosphere during the collision of the Caroline Ridge with the Yap Trench (20–25 Ma), which played a key role in the evolution of the Yap subduction system. Moreover, the seaward slope lava represents the subduction plate crust that accreted onto the deep trench during the collision. This collision event resulted in the cessation of Yap Arc magmatism; thus, the Yap Trench volcanic rocks (<25 Ma) previously suggested to be arc magma products may actually represent the nascent island arc lava with a lower subduction component than in the mature Mariana Arc lava. 相似文献
17.
A. I. Ryabinin S. A. Bobrova L. V. Saltykova E. A. Danilova 《Physical Oceanography》2012,21(5):320-328
We study the space-and-time variations of the delivery of fluxes of 26 elements (Na, K, Rb, Cs, Cu, Ag, Au, Ca, Sr, Ba, Zn,
Cd, Hg, Hf, Ta, As, Sb, Cr, Se, Mo, W, Mn, Br, Fe, Co and Ni) with atmospheric precipitations to the sea surface in the regions
of Sevastopol and the South Coast of Crimea. It is established A series of general regularities of the delivery of the sum
of these elements and their soluble and insoluble forms. We also give the characteristics of their space-time variability. 相似文献
18.
Subducted sediments play an important role in the magmatism at subduction zones and the formation of mantle heterogeneity, making them an important tracer for shallow crustal processes and deep mantle processes.Therefore, ascertaining the chemical compositions of different subduction end-members is a prerequisite for using subducted sediments to trace key geological processes. We reports here the comprehensive major and trace element analyses of 52 samples from two holes（U1414 A and U1381 C） dri... 相似文献
19.
桂北摩天岭和元宝山地区广泛发育花岗岩类岩石.岩石地球化学研究表明,该区花岗岩类岩石具有相对富硅、钾,贫钠、钙,富集轻稀土以及Ba、Sr、Eu亏损的特征.岩石属于碱性-钙碱性高钾花岗岩,其分离结晶作用强烈,是岩浆演化至晚阶段的产物.对岩石的成因分析表明,该区花岗岩类岩石是在扬子板块与华夏板块以及个别小型岛弧地体的碰撞造山作用下形成的后造山花岗岩类. 相似文献