共查询到19条相似文献，搜索用时 111 毫秒
1.
地幔流体作用——地幔捕虏体中流体包裹体的研究 总被引：8，自引：0，他引：8
被碱性玄武岩和金伯利岩带到地表的地幔捕虏体是认识地球深部信息的窗口 ,是人们能够直接观察到的一种上地幔样品 ,其矿物中流体包裹体的存在提供了上地幔流体活动的直接证据。流体 /地幔矿物之间元素的分配对约束地幔交代过程中流体相的作用和上地幔流体的组成 ,揭示俯冲带壳幔物质的再循环过程 ,解释岛弧玄武岩高场强元素亏损的原因有重要意义。文章对近年来有关地幔捕虏体中流体包裹体的研究进行了评述 ,并结合近年来流体 /地幔矿物之间元素分配的高温高压实验研究讨论了流体在地幔中的重要作用。 相似文献
2.
东南沿海地区古近纪大陆岩石圈地幔特征及成因 总被引：3，自引：0，他引：3
东南沿海地区新生代玄武岩中的橄榄岩包体来自岩石圈地幔 ,上地幔橄榄岩包体的岩石学及地球化学特征都记录了地幔演化的历史。普宁橄榄岩包体斜方辉石含量与太古宙克拉通地幔类似 ,但在矿物学、REE、痕量元素和Sr Nd同位素上又与太古宙岩石圈地幔不同。橄榄岩包体的岩相学、矿物学、REE、痕量元素特征都提供了含H2 O富Si流体交代橄榄岩的证据 ,这种流体可能主要是洋壳物质局部熔融而成。流体交代使橄榄岩富Si,同时富Sr、Pb和强不相容元素等大洋岩石圈物质。这表明普宁大陆岩石圈地幔既保留太古宙岩石圈地幔的特征 ,又具有大洋俯冲地幔的特征 ,它是古老岩石圈地幔向大洋岩石圈地幔转换的一部分 ,这种转换可能是大洋岩石圈与大陆岩石圈地幔相互作用的结果。 相似文献
3.
高温高压岩石粒间熔体（和流体）形态学及其研究进展 总被引：2，自引：0，他引：2
高温高压岩石粒间熔体（和流体）形态学是现代岩石学的前沿领域之一。它主要研究高温高压下低程度部分熔融（或含少量流体）岩石中,矿物颗粒之间熔体（或流体）形态特征、连通性,以及与周围矿物相互关系的科学。研究中较多地借鉴了材料科学的研究方法,与界面物理化学密切相关。高温高压下地幔岩石粒间熔体（和流体）形态学的研究为探讨地幔部分熔融作用、软流圈和地幔交代作用的成因提供了重要的实验依据,已成为地球深部研究的重要手段之一。目前该学科还没有为我国广大地学工作者所熟悉。为此,对高温高压岩石粒间熔体（和流体）形态学的基础理论、实验方法,以及某些实验研究结果进行简要介绍,从而为读者对该学科的了解提供一些便利。 相似文献
4.
地幔硫化物是地球亲硫、亲铁元素的重要载体,与硅酸盐矿物有很大的物理性质上差别,它在高温高压条件下的物理化学性质是认识地幔物质组成及其不均一性的重要内容。此外,早期地球、火星、水星和月球幔部来源的硫化物对认识行星演化具有重要意义。地幔硫化物的存在条件、赋存方式以及元素分配系数受到硫化物和硅酸盐体系的化学平衡控制;硫化物在流体介质和固体介质中的迁移可以分别用斯托克斯方程和表面张力模型进行解释。基于目前的天然样品和实验研究结果,本文提出了地幔硫化物物理化学性质研究中尚存在的问题,并作展望：高温高压实验制约分配系数适用的元素含量远高于天然样品,导致亨利定律并不一定适用,要求开展元素含量更低的实验并进行测试;现有的线性或自然对数的经验方程不能准确描述硫化物-硅酸盐体系,机器学习可能揭示其错综复杂的热力学关系;硫化物熔体在深部地幔硅酸盐矿物表面的分布尚不清楚,对极端条件下的静水压力实验提出了需求。 相似文献
5.
实验地球化学研究进展 总被引：1，自引：0，他引：1
实验技术的完善与成熟，使实验地球化学渗透到许多研究领域，从而成为地球化学及相关学科研究不可缺少的手段之一。本文总结了近２０年来国内外实验地球化学在元素的分配行为（分配系数）、高压矿物相与岩石的形成与演化、超高压凝聚态物质性质、超临界条件下岩石－流体相互作用及开放体系下化学地球动力学方面的研究进展及存在的主要问题。 相似文献
6.
大陆俯冲带的深部流体及变质化学地球动力学
——以苏鲁超高压变质带为例 总被引：1，自引：0，他引：1
通过苏鲁超高压变质带的岩石学、矿物化学、地球化学和年代学研究,在大陆俯冲带深部流体与变质化学地球动力学方面取得了重要的创新性成果。研究证明大陆俯冲带的深部流体是高氧逸度、富硅酸盐的超临界流体,揭示出超高压变质极端条件下的流体－矿物(岩石)相互作用可以导致不活动元素发生溶解和迁移,可以导致金红石的Nb/Ta之间发生强烈的分异,提出俯冲到地幔深处的超高压榴辉岩是地球内部“隐藏”的超球粒陨石Nb/Ta比值的物质源区,与低球粒陨石Nb/Ta比值的物质源区大陆地壳和亏损地幔在化学成分上形成互补。 相似文献
7.
东南沿海地区第四纪大陆岩石圈地幔的特征 总被引：5，自引：0，他引：5
东南沿海地区新生代玄武岩中的橄榄岩包体来自年轻的大陆岩石圈地幔 ,该岩石圈地幔在岩石学、矿物组成、痕量元素以及Sr Nd同位素组成等各方面具有很大差异。这些差异反映了它们来自不同的地幔过程。南海张开与地幔热柱有关 ,南海扩张后第四纪形成的火山岩携至地表的包体更多保留了地幔热柱的信息。橄榄岩包体的矿物成分与深海橄榄岩类似 ,相对贫Opx而富Ol;在痕量元素上 ,表现为强不相容元素的富集 ,其配分模式类似于其寄主岩 ;Nd同位素强烈亏损 ,显示出比MORB源区更亏损的特征。大陆岩石圈地幔经历了来自地幔深处的贫SiO2 熔体的进一步改造。 相似文献
8.
水/岩反应实验与成矿作用 总被引：3，自引：0，他引：3
需要进行一系列从常温常压到高温高压地球化学实验,来揭示流体与岩石的化学反应与成矿元素活化、迁移和富集成矿。流体将岩石中的成矿元素活化,取决于成矿元素本身的物化性质、在岩石中的赋存状态以及与其它元素的关系。 相似文献
9.
胶辽半岛金伯利岩中地幔捕虏体岩石学特征：古生代岩石圈地幔及其不均一性 总被引：29，自引：5，他引：24
华北东部古生代岩石圈地幔经历过复杂的多旋回多阶段熔融岩浆、重结晶、变质和剪切变形历史,因而岩石组成、结构复杂.地幔橄榄岩的主元素、地幔矿物特别是金刚石中的包裹体的Mg#值及Cr#值等显示古生代岩石圈地幔高度难熔亏损玄武质的成分特征,而地幔橄榄岩的不相容元素、同位素显示高度富集的特点.这种高难熔和强富集两重性是克拉通岩石圈地幔的特征.Pb同位素反映华北东部古生代岩石圈地幔具冈瓦纳大陆地幔的特点.复县和蒙阴古生代岩石圈地幔尽管都表现为太古代克拉通地幔的特征,但存在着不均一性,前者受克拉通化后的深部作用影响强于后者.与新生代地幔Sr、Nd同位素对比表明富集的古生代岩石圈地幔向亏损新生代的地幔转变和减薄伴有新生地幔物质对古老岩石圈的置换和混合作用. 相似文献
10.
地幔流体与地球的放气作用 总被引：7，自引：0，他引：7
地幔流体的形成、聚集和渗透是引起地幔交代作用的主要营力。地幔交代作用发育的强弱决定着所生成岩浆的碱性程度。地幔流体和部分熔融体高度富集不相容元素,它们与亏损地幔的相互作用可以使后者发生ＬＲＥＥ和不相容元素的局部富集。通过板块俯冲作用使地球表层的ＣＯ２进入地幔,参加地球的碳循环。热点岩浆来源的ＣＯ２中含有部分循环的ＣＯ２,而大洋中脊玄武岩中的ＣＯ２主要是原始地球的ＣＯ２。携带ＣＨ４和Ｈ２Ｏ的流体渗透至被俯冲带带入地幔的物质,使碳酸盐化的榴辉岩还原而形成含金刚石的榴辉岩和富水流体,并诱发局部熔融,所形成的熔体以火山喷发的形式上升到地表。地幔岩石中含有大量的流体,它们主要以流体包裹体的形式存在于地幔矿物中。几乎在所有的上地幔环境下形成的矿物中均找到了流体包裹体。包裹体内流体的成分主要是ＣＯ２,ＣＨ４,Ｈ２Ｏ及少量Ｈ２,Ｎ２等。 相似文献
11.
微量元素在幔源矿物与热液之间分配系数的差异是造成地幔不均一的一个重要因素，对于认识地球演化、元素的分异和板块构造具有重要的意义。热液的组成、矿物的结构、温度、压力以及氧逸度都与分配系数密切相关。不同微量元素在相同矿物或热液中的分配系数存在差别，而相同的元素在不同矿物中的分配系数也可能出现很大的变化，这是研究微量元素分异和不同地幔端员形成的理论基础。在较低的温度和压力下，热液的组成对分配系数的影响很大，随着温度和压力的升高，热液组成的影响逐渐减弱，而矿物的组成与结构的影响逐渐增大。由于分配系数影响因素的复杂性，因此在考虑地球深部微量元素的迁移和分异时需慎重对待。 相似文献
12.
Deep fluids in subduction zones 总被引：31，自引：0，他引：31
The fluid inclusions preserved in high and ultrahigh pressure rocks provide direct information on the compositions of fluid phases evolved during subduction zone metamorphism, and on fluid–rock interactions occurring in such deep environments. Recent experiments and petrologic studies of eclogite–facies rocks demonstrate that stability of a number of hydrous phases in all rock systems allows fluid transport into the mantle sources of arc magmas, as well as into much deeper levels of the Earth's mantle. In eclogite–facies rocks, the presence of large ion lithophile elements (LILE) and light rare earths (LREE)-bearing hydrous phases such as epidote and lawsonite, together with HFSE repositories as rutile and other Ti-rich minerals, controls the trace element budget of evolved fluids and fluid-mediated cycling of slab components into the overlying mantle.
Studies of fluid inclusions in eclogite–facies terrains suggest that subduction mainly evolves aqueous solutions, melts being produced only locally. Eclogite-facies rocks diffusely record processes of fluid–melt–rock interactions that exerted considerable control on the element and volatile budget of subduction fluids. Trace element fractionation during such interactions needs to be tested and quantified in more detail to achieve the ultimate compositions actually attained by fluids leaving off the slab. Variably saline inclusions with minor CO2 and N2 are trapped in rock-forming high pressure minerals; brines with up to 50% by weight dissolved solute are diffusely found in veins. The latter inclusions are residues after fluid–rock interactions and deposition of complex vein mineralogies: this evidence suggests increased mineral solubility into the fluid and formation, at a certain stage, of silicate-rich aqueous solutions whose geochemical behaviour and transport capacity can approach that of a melt phase. This is supported by experimental work showing high solubility of silicate components in fluids at high pressures. However, natural examples of inclusions trapping such a fluid and quantitative analyses of its major and trace element composition are not yet available.
Fluids in high and very high pressure rocks do not move over large scales and the channelways of fluid escape from the slab are not yet identified. This suggests that only part of the slab fluid is lost and returned to the surface via magmatism; the remaining trapped fraction being subducted into deeper levels of the upper mantle, to renew its budget of substances initially stored in the exosphere. 相似文献
13.
Trace element abundances in megacrysts and their host basalts: Constraints on partition coefficients and megacryst genesis 总被引：1，自引：0，他引：1
In an effort to obtain information about mineral/melt trace element partitioning during the high pressure petrogenesis of basic rocks, we determined rare earth and other trace element abundances in megacrysts of clinopyroxene, orthopyroxene, amphibole, mica, anorthoclase, apatite and zircon, and in their host basalts. In general, the ranges of mineral/melt partition coefficients established from experimental partitioning studies and phenocryst/matrix measurements overlap with the ranges of megacryst/host abundance ratios. Our data for Hf, Sc, Ta and Th partitioning represent some of the only estimates available. Consideration of phase equilibria, major element partitioning and isotopic ratios indicate that most of the pyroxene and amphibole megacrysts may have been in equilibrium with their host magmas at high pressures (mostly 10–25 kb). In contrast, it is unlikely that mica, anorthoclase, apatite and zircon megacrysts formed in equilibrium with their host basalts; instead, we conclude that they were precipitated from more evolved magmas and have been mixed into their present host magmas. Consequently, the trace element abundance ratios for megacryst/host should not be interpreted as partition coefficients, but only as guides for understanding trace element partitioning during high pressure petrogenesis. With this caveat, we conclude that the megacryst/ host trace element abundance data indicate that mineral/melt partition coefficients in basaltic systems during high pressure fractionation are not drastically different from partition coefficients valid for low pressure fractionation. 相似文献
14.
Roger G. Burns 《Geochimica et cosmochimica acta》1973,37(11):2395-2403
Interrelationships between chemical compositions and crystal structures of minerals pioneered by Goldschmidt have been overlooked by modern geochemists. While analytical techniques and data for trace elements have become more sophisticated, progress has been slow in relating abundance data of individual elements to their relative enrichments in specific sites in mineral structures. The concept of diadochy has degenerated into an analytical relationship between major and trace elements, instead of its original crystallographic basis of replacement of one atom by another at a specific site in a crystal structure. Future interpretations of trace element data must consider the partitioning of atoms between different coordination sites in multisite mineral structures.The well-known partitioning of nickel and chromium into the earliest minerals during magmatic crystallization is extended to magma evolution in the mantle. The strong preference of Ni2+ and Cr3+ for octahedral sites in minerals leads to their enrichment in certain Iherzolites which are refractory residua during partial fusion of the mantle. 相似文献
15.
造山带橄榄岩记录了板块俯冲、碰撞、折返等复杂过程信息,可分为壳源和幔源两种类型.造山带橄榄岩（特别是幔源类型）中锆石极为罕见,锆石内部具有橄榄岩的特征矿物或组合包裹体说明这些锆石可以生长于地幔中.造山带橄榄岩在经历板块汇聚（例如超高压变质等）复杂作用过程中,经历了不同时期的熔/流体的交代作用,对橄榄岩的矿物组合和元素组成都能产生重要影响.橄榄岩中锆石作为典型的交代作用产物,它的形成受控于熔/流体的化学组成、来源属性以及形成物理化学环境等.幔源型造山带橄榄岩中锆石的形成过程可能包括:（1）锆石结晶能力强,在地幔环境变化中Zr优先与其他地幔硅酸盐矿物中的Si结合,形成锆石;（2）原始锆石的溶解和含Zr矿物相（如石榴石等）的破坏或晶间熔体析出,在亚固相线条件下形成锆石;（3）再循环地壳物质来源的熔/流体,交代地幔楔并结晶形成锆石.因此利用锆石可以揭示特定岩石圈域的演化历史,有助于深刻理解大陆克拉通及其边缘过程. 相似文献
16.
Nature and origin of eclogite xenoliths from kimberlites 总被引：16，自引：0，他引：16
Eclogites from the Earth's mantle found in kimberlites provide important information on craton formation and ancient geodynamic processes because such eclogites are mostly Archean in age. They have equilibrated over a range of temperatures and pressures throughout the subcratonic mantle and some are diamond-bearing. Most mantle eclogites are bimineralic (omphacite and garnet) rarely with accessory rutiles. Contrary to their overall mineralogical simplicity, their broadly basaltic-picritic bulk compositions cover a large range and overlap with (but are not identical to) much younger lower grade eclogites from orogenic massifs. The majority of mantle eclogites have trace element geochemical features that require an origin from plagioclase-bearing protoliths and oxygen isotopic characteristics consistent with seawater alteration of oceanic crust. Therefore, most suites of eclogite xenoliths from kimberlites can be satisfactorily explained as samples of subducted oceanic crust. In contrast, eclogite xenoliths from Kuruman, South Africa and Koidu, Sierra Leone stem from protoliths that were picritic cumulates from intermediate pressures (1–2 Ga) and were subsequently transposed to higher pressures within the subcratonic mantle, consistent with craton growth via island arc collisions. None of the eclogite suites can be satisfactorily explained by an origin as high pressure cumulates from primary melts from garnet peridotite. 相似文献
17.
地幔转换带是联系上下地幔的纽带,对于认识整个地幔的组成和演化、地幔对流、岩石圈深俯冲及深源地震等地球深部动力学问题具有重要意义。一般认为,转换带地震不连续面主要与橄榄石的高压相变密切相关。最新的高温高压实验研究表明,地幔中非橄榄石组分的相变,如辉石和石榴子石的相变,对不连续面的深度和宽度以及转换带内的波速和密度梯度也起到很大的影响。另外地幔全岩成分、端员组分、温度和水也对相变和不连续面具有重要影响,这些精细的实验研究成果更好地解释了转换带地震不连续面一些相对局部的性质和变化,促进了我们对地球深部性质和动力学过程的了解。因为缺少直接来自地球深部的样品,而地球物理和地球化学研究也有它们的相对局限性,所以高温高压实验仍然是我们了解地球深部成分和性质的重要手段之一。 相似文献
18.
A. Günter Herrmann Douglas P. Blanchard Larry A. Haskin Jeffrey W. Jacobs Doris Knake Randy L. Korotev Joyce C. Brannon 《Contributions to Mineralogy and Petrology》1976,59(1):1-12
Major and trace element compositional data are reported for nine mafic and ultramafic rock samples from the Barberton greenstone belt. Rocks from this province are among the oldest fragments of the Earth's crust (3.5 b.y.). The data are consistent with an oceanic crust related origin for these rocks. The high abundances of Ni in these samples make their origin by fractional crystallization of a primitive magma unlikely but are consistent with their generation by partial melting of an upper mantle source. The basaltic samples from the Komati formation can be related by small degrees of partial melting of a primitive upper mantle source to the peridotitic komatiite which probably derived from much more extensive partial melting of a similar source. REE and especially Ni abundances limit the proportion of olivine that is permitted in the residue. 相似文献
19.
用质子探针和电子探针分别测定盘石山幔源橄揽岩包体中透辉石、橄榄石的微量元素和主量元素丰度;用X-射线荧光光谱法测定包体全岩的主量和微量元素丰度。定量讨论微量元素的分布和分配。其中绝大部分Sr、Zr、Ti、Na赋存在透辉石中,绝大部分Mn、Zn、Ni赋存在橄揽石中,在T=1194-1435K范围,分配系数变化如下:InDOl/CpxZn=1.44-2.19;InDOl/CpxMn=0.21-0.40,InDOl/CpxTi=4.76-5.61,InDOl/CpxNi(平均值)=2.20.透辉石中Ti/Zr=42-103,低于原始地幔值,由地幔隐性交代作用造成。 相似文献