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1.
洋岛和洋底高原玄武岩数据挖掘：地球化学特征及其与MORB的对比 总被引：6，自引：0，他引：6
本文集合了GEOROC和PetDB两个数据库的资料,对全球洋岛玄武岩(Ocean Island Basalt,OIB)和洋底高原玄武岩(Ocean Plateau Basalt,OPB)数据进行分析研究。OIB和OPB是板内岩浆活动的产物,其形成一般与地幔柱(热点)有关。OPB通常指示地幔柱的头部,温度相对较低;OIB代表地幔柱的尾部,温度较高。我们对OIB的数据研究表明,OIB中的不相容元素并非像先前认为的那么富集,在构造判别图中,OIB和洋中脊玄武岩(Mid Ocean Ridge Basalt,MORB)有很大一部分是重叠的,揭示OIB源区既有强烈富集不相容元素的,也有明显亏损的,甚至还有强烈亏损类似岛弧玄武岩(Island Arc Basalt,IAB)的。OPB是指发育在海洋和大陆边缘的来自地幔的巨量玄武岩,虽然与OIB同属于板内环境,但OPB的地球化学性质更接近富集型洋中脊玄武岩(Enrich Mid Ocean Ridge Basalt,E-MORB),可能具有OIB和MORB之间过渡的特征。研究表明,OIB和OPB的源区除了来自下地幔以外(地幔柱),部分可能来自上地幔,有些还可能与板块消减带物质的再循环作用有关。因此,OIB和OPB的成因不可能只用地幔柱一种模式予以解释,还应当考虑板块活动中其他因素(洋壳再循环、古老陆壳再循环、消减带物质以及水的加入,部分熔融程度、岩浆混合作用、不同地幔端元混合等)的影响。 相似文献
2.
中国南方新生代地幔柱活动的地球化学证据 总被引：7，自引：0，他引：7
中国南海海盆、海南岛、雷琼和龙海—明溪地区新生代玄武岩的总体相当于洋岛玄武岩（OIB）,富集高场强元素（HFSE）,尤其是富集Nb、Ta、U、Ti。南海海盆新生代玄武岩是玻利尼西亚型（Polynesian）、夏威夷型（Hawaii）和MORB型共存,可能是在扩张洋脊上面形成的OIB,下地幔成因的超地幔柱上升致使上地幔物质加入,海南岛和雷琼地区玄武岩具有与南海海盆玄武岩大致相似的成因。大陆板内同时代的龙海—明溪地区玄武岩具特别高的Nb/Zr和Nb/Y值,均表现为地幔柱成因的玻利尼西亚型玄武岩,其形成既可能有古老俯冲洋壳熔融后榴辉岩质残余下沉至下地幔成因,也可能有包括下地壳在内的岩石圈物质的贡献。 相似文献
3.
大陆板内玄武岩数据挖掘:成分多样性及在判别图中的表现 总被引：7，自引：4，他引：3
通常认为,大陆溢流玄武岩(CFB)、裂谷玄武岩(CRB)、板内玄武岩(WPB)均产于板内构造环境,其地球化学特征与OIB类似,源于富集的下地幔,与地幔柱的活动有关。本文利用GEOROC数据库对全球CFB、CRB和WPB数据进行挖掘,发现上述三类玄武岩判别图投图几乎落入了全部的构造环境域,有些甚至主要落入MORB和IAB区,而不是落入WPB区。结果表明原先的玄武岩判别图的判别功能值得商榷,尤其对大陆玄武岩来说,许多判别图都存在问题。全体CFB、CRB和WPB的地球化学成分变化巨大,暗示其源区具有强烈的不均一性:部分CFB、CRB和WPB来自富集的地幔柱,仍然具有经典的OIB的特征;部分来自MORB的源区,与MORB的再循环作用有关;部分来自岛弧岩石圈之下的亏损地幔源区,以强烈亏损Nb-Ta为特征,类似岛弧玄武岩的地球化学特征。许多地区的大陆玄武岩可分为低钛和高钛两类,低钛玄武岩大多是亏损或强烈亏损的,而高钛玄武岩通常是富集型的。本文的研究表明,富集型大陆玄武岩可能来自富集的下地幔,而亏损的和强烈亏损的玄武岩可能来自具有MORB或岛弧特征的软流圈地幔。进一步指出,源区性质可能是大陆玄武岩多样性的主控因素,其次为部分熔融程度、熔融深度、结晶分离、陆壳混染以及AFC过程。 相似文献
4.
5.
《矿物岩石地球化学通报》2017,(1)
<正>洋岛玄武岩(OIB)的地球化学不均一性通常都被解释为地幔柱中存在再循环的地壳物质,但是再循环物质的性质和形成时代很难限定。比如说,对于富集1型地幔端元(EM1)的来源,就有深海沉积物、大陆下地壳、大陆岩石圈地幔等多种推测。法国和德国的科学家们对具有典型EM1型地球化学信号的Pitcairn玄 相似文献
6.
洋岛玄武岩的元素和同位素地球化学特征可以示踪深部地幔的化学结构和化学演化过程。HIMU(Highμ,μ=238U/204Pbt=0)
型玄武岩是一类元素和同位素组成特殊的洋岛玄武岩,被认为与地幔柱中再循环的洋壳物质直接相关,因此,HIMU型玄
武岩的成因是地幔柱（热点） 研究中长期关注的话题。本文概述了HIMU型玄武岩的地球化学定义,对HIMU洋岛的分布、
火山演化阶段以及岩性变化做了综合阐述,并在对比经典HIMU型玄武岩与其他板内玄武岩元素地球化学特征、放射成因
同位素组成以及惰性气体同位素组成特征的基础上,简要探讨其源区组成和成因上的不同。 相似文献
7.
地壳再循环与大陆碱性玄武岩的成因：以山东新生代碱性玄武岩为例 总被引：6，自引：0，他引：6
大陆碱性玄武岩在地球化学特征上与洋岛玄武岩高度相似,被看做是板内玄武岩在大陆上的典型代表。本文以山东
新生代碱性玄武岩为例,探讨大陆碱性玄武岩的成因。山东新生代碱性玄武岩按时空分布特征可以分为两类：早期定向分
布、相互平行的三个火山群（包括鲁西的潍坊火山群、沂水火山群和胶东的蓬莱火山群）和晚期杂乱分布的孤立小火山。
早期火山群碱性较弱,以碱性橄榄玄武岩和碧玄岩为主,微量元素特征和同位素组成变化大;晚期孤立小火山碱性强,以
碧玄岩和霞石岩为主,微量元素特征和同位素组成较均一。因此,从岩性组成和时空分布特征看,山东的火山群相当于洋
岛/海山的造盾期玄武岩,而孤立小火山接近于洋岛/海山上的复苏期玄武岩。潍坊火山群和沂水火山群在Sr-Nd,Nd-Hf同位
素相关图上都存在从亏损到富集的两端元混合排列趋势,但两者的排列趋势有一点区别。其中同位素富集的端元相对于原
始地幔具有偏低的Ce/Pb比和偏高的Ba/Th比,指示其为大陆下地壳物质。同时,这种富集端元的Th/La比值明显低于大陆下
地壳的平均值,其放射成因Hf相对于放射成因Nd过剩（即Nd-Hf同位素解耦）,说明这种富集端元不是岩浆上升过程中混染
的下地壳物质,而是经历过早期熔融的再循环大陆下地壳（榴辉岩或者石榴辉石岩）。鲁西两个平行火山群在同位素排列上
的区别类似于夏威夷玄武岩中的KEA链和LOA链,因此,山东的平行火山群的深部动力学背景可能是地幔柱,再循环大陆
下地壳物质可能是这种地幔柱的重要组成物质。晚期的孤立小火山在地球化学特征上与火成碳酸岩非常相似,如在原始地
幔标准化图上都具有K,Pb,Zr,Hf,Ti的负异常等特征,因此我们认为其地幔源区为碳酸盐化的橄榄岩。孤立小火山中等亏损
的Sr,Nd,Hf同位素特征支持碳酸岩熔体来自年轻的（中生代？）再循环洋壳。 相似文献
8.
雅鲁藏布江缝合带西段东波蛇绿岩OIB型玄武岩的厘定及其形成环境 总被引：9，自引：8，他引：1
雅鲁藏布江缝合带(YZSZ)西段分为两支,南带蛇绿岩的成因对整个缝合带的性质和构造背景的探讨起到十分关键作用,但由于地区偏远、交通不便,研究程度一直十分薄弱.本文报道了南带的东波蛇绿岩中洋岛型玄武岩及有关沉积岩的发现和成因探讨.东波蛇绿岩主要由地幔橄榄岩(方辉橄榄岩、含单辉方辉橄榄岩和透镜状纯橄岩)和上覆火山-沉积岩组成,未见堆晶岩和枕状熔岩等典型洋壳端元.火山-沉积岩盖层为一套稳定的海相层序,主要由硅质灰岩、红色硅质岩等沉积岩和玄武岩和玄武火山碎屑岩组成.OIB型玄武岩的特征表现为低SiO2和MgO,高TiO2、P2O5和(K2O+Na2O),富集Nb、Ta,亏损Th、K、Pb、Sr.微量元素和Sr、Nd、Pb同位素数据显示,该玄武质源区来自石榴石尖晶石二辉橄榄岩2％ ～ 5％的部分熔融.成分研究显示,硅质岩形成于大陆边缘环境,为洋岛或海山和大陆边缘物质在生物作用下形成的.以上证据表明,东波火山-沉积岩层序具有典型海山特征,与世界上典型的地幔柱型蛇绿岩可对比,属于地幔柱热点活动的产物.因此,可以认为,地幔柱热点在与冈瓦纳大陆北缘岩石圈地幔相互作用过程中,不但促使YZSZ西段南带(达巴-休古嘎布)特提斯洋盆打开,还可能与YZSZ蛇绿岩中普遍包含金刚石等异常地幔矿物群有直接的动力学关系. 相似文献
9.
MORB 是玄武岩中研究得最详细的玄武岩类,可分为N-MORB 和E-MORB 两类。通常认为,N-MORB 和OIB 都是独立的端元,分别来自亏损和富集的地幔源岩,而E-MORB 则是N-MORB 与OIB 混合的结果。本文研究表明,E-MORB 具复杂的成因,洋脊深度、洋脊扩张速率及源区部分熔融程度及压力不是造成E-MORB 富集的主要原因。压力及部分熔融程度对玄武岩成分的影响远小于地幔不均一性的影响。推测E-MORB 可能有两个主要的形成方式：1） 由较深处略富集的地幔发生部分熔融而成;2） 由N-MORB 与OIB 混合形成。玄武岩微量元素频率直方图表明,N-MORB 基本上保持了来自亏损地幔源区的特征;OIB 则多多少少受到外来物质加入或与N-MORB 混合的影响; E-MORB 则是N-MORB 受OIB 影响的产物。OIB 与E-MORB 似乎没有本质上的区别, 仅仅是受影响和混合程度的不同而已。OIB 富集LILE,可能既有继承了来自源区的特征（深部富集地幔、循环的古洋壳、循环的陆壳、大陆岩石圈地幔、LVZ 熔体层或早期交代岩脉等）,也可能有外来物质加入的影响（与N-MORB 发生不同程度的混合作用）。3 类玄武岩的87Sr/86Sr 和143Nd/144Nd 同位素频率分布与早先的结论一致,但206Pb/204Pb、207Pb/204Pb和208Pb/204Pb同位素频率分布显示OIB 具有更加复杂的特征。 相似文献
10.
大陆玄武岩通常具有与洋岛玄武岩相似的地球化学成分,其中含有显著的壳源组分.对于洋岛玄武岩来说,虽然其中的壳源组分归咎于深俯冲大洋板片的再循环,但是对板片俯冲过程中的壳幔相互作用缺乏研究.对于大陆玄武岩来说,由于其形成与特定大洋板片在大陆边缘之下的俯冲有关,可以用来确定古大洋板片俯冲的地壳物质再循环.本文总结了我们对中国东部新生代玄武岩所进行的一系列地球化学研究,结果记录了古太平洋板片俯冲析出流体对地幔楔的化学交代作用.这些大陆玄武岩普遍具有与洋岛玄武岩类似的地球化学成分,在微量元素组成上表现为富集LILE和LREE、亏损HREE,但是不亏损HFSE的分布特点,在放射成因同位素组成上表现为亏损至弱富集的Sr-Nd同位素组成.在排除地壳混染效应之后,这些玄武岩的地球化学特征可以由其地幔源区中壳源组分的性质来解释.俯冲大洋地壳部分熔融产生的熔体提供了地幔源区中的壳源组分,其中包括洋壳镁铁质火成岩、海底沉积物和大陆下地壳三种组分.华北和华南新生代大陆玄武岩在Pb同位素组成上存在显著差异,反映它们地幔源区中的壳源组分有所区别.中国东部新生代玄武岩的地幔源区是古太平洋板片于中生代俯冲至亚欧大陆东部之下时,在>200 km的俯冲带深度发生壳幔相互作用的产物.在新生代期间,随着俯冲太平洋板片的回卷引起的中国东部大陆岩石圈拉张和软流圈地幔上涌,那些交代成因的地幔源区发生部分熔融,形成了现今所见的新生代玄武岩. 相似文献
11.
Lateral flow of African mantle below the nearby Tyrrhenian plate: geochemical evidence 总被引：1，自引：0，他引：1
The Quaternary magmatism of the Southern Tyrrhenian basin represents a rare example of an active volcanic arc system where ocean island basalt (OIB) and island arc basalt (IAB) magmas coexist. Although there is general agreement on the importance of the Ionian oceanic lithosphere subduction in the genesis of the IAB magmatism, the tectono‐magmatic processes producing the coexisting OIB magmas are still poorly understood. Here we show that the geochemistry of the Quaternary Southern Tyrrhenian OIB‐type magmatism (i.e. Ustica island and Prometeo, a previously unknown submarine lava field) is very similar to that of OIB‐type volcanoes situated on the nearby African plate (i.e. Etna and Hyblean Plateau). Among the possible geodynamic scenarios proposed to explain the coexistence of OIB and IAB magmas in arc settings, we consider the development of a tear at the edge of the Ionian plate as the more likely mechanism to favour the flow of African asthenospheric mantle below the Tyrrhenian plate. 相似文献
12.
蛇绿岩记录了大洋岩石圈形成、演化、消亡的全过程,是刻画区域板块构造和洋 陆格局演化的关键证据。本文通过系统梳理前人相关研究,总结西准噶尔蛇绿岩最新研究成果,探讨大陆地壳增生方式、恢复古大洋演化历史,从而对西准噶尔构造体制转化提供新制约。西准噶尔地区发育多条震旦纪—石炭纪被构造肢解的蛇绿岩带,具有典型的岩块 基质结构,绝大多数蛇绿岩包括正常洋壳组分和海山/大洋高原残片,其中基性岩具有MORB和OIB的地球化学特征。基于前人研究,本文认为在西准噶尔古大洋发育过程中,发育不同时代与地幔柱有关的海山/大洋高原,同时存在增生型和侵蚀型两类汇聚板块边界。另外,大洋高原增生不仅是大陆地壳增生的有效途径之一,还可能诱发俯冲极性反转和传递。而在大洋高原形成初期,还可能存在地幔柱诱发俯冲起始机制。 相似文献
13.
俯冲工厂和大陆物质的俯冲再循环研究 总被引：3，自引：3，他引：3
板块的俯冲系统可以比拟为一个工厂。再循环研究强调对俯冲物质各种组分的行为、去向的追踪和定量分析。沉积物俯冲和俯冲侵蚀作用导致陆壳物质返回地幔,初步估算表明,大陆物质返回地幔的速率与岩浆活动导致陆壳生长的速率在数量上大体相当,晚近时期陆壳的净增长速率可能近于零。大洋岛玄武岩地化特征上的多样性提示,沉入下地幔的板片可能从深部卷入地幔柱的源区。俯冲再循环过程对地壳、地幔的动力学和演化产生深刻影响。 相似文献
14.
活动陆缘玄武岩（CAB）主要出现在安第斯,早先大多认为CAB 大体相当于IAB,在许多判别图中, CAB 基本上与IAB 在一起, 只是LILE 富集和HFSE 亏损的程度略有差别而已。本文的研究表明,尽管CAB 富集LILE,但是,Nb-Ta 亏损不是非常明显。在最新的采用大数据方法厘定的判别图中,CAB 不同于IAB,不是落在IAB 区,而是位于IAB 与OIB 的过渡区域。CAB 中保留了很多OIB 的印记,说明板块俯冲时伴随有来自地幔深部的岩浆的加入,故CAB 中保留了OIB 的印记。我们的研究还发现, 在安第斯弧后盆地玄武岩具有OIB 的印记,而非MORB 的特征。本文按照大数据的思路,讨论了CAB 的特征,并与IAB、BAB 进行了初步的对比。研究表明,CAB 明显不同于IAB,CAB 兼具IAB 和OIB 的特征,但对其深度的认识还有待于今后进一步的研究。 相似文献
15.
The Blovice accretionary complex, Bohemian Massif, hosts well-preserved basaltic blocks derived from an oceanic plate subducted beneath the northern active margin of Gondwana during late Neoproterozoic to early Cambrian. The major and trace element and Hf–Nd isotope systematics revealed two different suites, tholeiitic and alkaline, whose composition reflects different sources of melts within a back-arc basin setting. The former suite has composition similar to mid-ocean ridge basalts (MORB), yet with striking enrichment in large-ion lithophile elements (LILE) and Pb paralleled by depletion in Nb, in agreement with its derivation from depleted mantle fluxed by subduction-related fluids. In contrast, the latter suite has composition similar to ocean island basalts (OIB) with variable contribution of ancient, recycled crustal material. We argue that both suites represent volcanic members of Ocean Plate Stratigraphy (OPS) and indicate that the oceanic realm consumed by the Cadomian subduction was a complex mosaic of intra-oceanic subduction zones, volcanic island arcs, and back-arc basins with mantle plume impinging the spreading centre. Hence, the basalt geochemistry implies that two distinct domains of oceanic lithosphere may have existed off the Gondwana’s continental edge: an outboard domain, made up of old and less buoyant oceanic lithosphere (remnants of the Mirovoi Ocean surrounding former Rodinia?) that was steeply subducted and generated the back-arcs, and young, hot, and more buoyant oceanic lithosphere generated in the back-arcs and later involved in accretionary complexes as dismembered OPS. Perhaps the best recent analogy of this setting is the Izu Bonin–Mariana arc–Philippine Sea in the western Pacific. 相似文献
16.
We present the first comprehensive major, trace element and Hf, Nd and Sr isotope investigation of clinopyroxene and garnet mineral separates from a set of garnet clinopyroxenite xenoliths from the Salt Lake Crater, Oahu, Hawaii. These xenoliths occur in the posterosional Honolulu Volcanics Series lavas and represent some of the deepest samples from the oceanic mantle lithosphere. Our study shows that the Salt Lake Crater pyroxenites represent high pressure (>20 kb) accumulates from melts similar (but not identical) to the erupted Honolulu Volcanics, and unlike MORB or E-MORB-type melts. All clinopyroxene-garnet mineral pairs in these xenoliths show, within error, zero-age Lu-Hf and Sm-Nd isotope systematics. These pyroxenites have relatively radiogenic Hf isotope compositions (for a given Nd) and define a distinct steep slope (3.3) in εHf-εNd isotope space, similar to the Honolulu Volcanics but unlike other ocean island basalts (OIB). These compositions require an end-member component that falls above the OIB array in Nd-Hf space. This component is different than present-day MORB-mantle and it is best explained by an old depleted oceanic lithosphere. We suggest that this depleted component most likely represents a recycled depleted lithosphere that is intrinsic to the Hawaiian plume. In this respect, the Hawaiian plume is sampling both the enriched portion of a subducted oceanic crust (basalt and sediments) as well as the depleted lithospheric portion of it. This suggests that, at least for Hawaii, the whole subducted oceanic slab package has retained its integrity during subduction and subsequent mixing and storage in the mantle, probably in the order of a billion years, and that the plume is sampling the full range of these compositions. 相似文献
17.
《International Geology Review》2012,54(8):879-893
Plate subduction and mantle plumes are two of the most important material transport processes of the silicate Earth. Currently, a debate exists over whether the subducted oceanic crust is recycled back to the Earth's surface through mantle plumes, and can explain their derivation and major characteristics. It is also puzzling as to why plume heads have huge melting capacities and differ dramatically from plume tails both in size and chemical composition. We present data showing that both ocean island basalt and mid-ocean ridge basalt have identical supra-primitive mantle mean Nb/U values of ～46.7, significantly larger than that of the primitive mantle value. From a mass balance calculation based on Nb/U?we have determined that nearly the whole mantle has evolved by plate subduction-induced crustal recycling during formation of the continental crust. This mixing back of subducted oceanic crust, however, is not straightforward, because it generally would be denser than the surrounding mantle, both in solid and liquid states. A mineral segregation model is proposed here to reconcile different lines of observation. First of all, subducted oceanic crustal sections are denser than the surrounding mantle, such that they can stay in the lower mantle, for billions of years as implied by isotopic data. Parts of subducted oceanic crust may eventually lose a large proportion of their heavy minerals, magnesian-silicate-perovskite and calcium-silicate-perovskite, through density segregation in ultra-low-velocity zones as well as in very-low-velocity provinces at the core-mantle boundary due to low viscosity. The remaining minerals would thus become lighter than the surrounding mantle, and could rise, trapping mantle materials, and forming mantle plumes. Mineral segregation progressively increases the SiO2 content of the ascending oceanic crust, which enhances flux melting, and results in giant Si-enriched plume heads followed by dramatically abridged plume tails. Therefore, ancient mineral-segregated subducted oceanic crust is likely to be a major trigger and driving force for the formation of mantle plumes. 相似文献
18.
Jianghong Deng Lipeng Zhang He Liu Haiyang Liu Renqiang Liao Abdul Shakoor Mastoi Xiaoyong Yang Weidong Sun 《地学前缘(英文版)》2021,12(3):101117
Seamounts on the drifting oceanic crust are inevitably carried by plate motions and eventually accreted or subducted. However, the geochemical signatures of the subducted seamounts and the significance of seamount subduction are not well constrained. Hundreds of seamounts have subducted beneath the Philippine Sea Plate following the westward subduction of the Pacific Plate since the Eocene (~52 Ma). The subducted oceanic crust and seamount materials can be exhumed from the mantle depth to the seafloor in the Mariana forearc region by serpentinite mud volcanoes, providing exceptional opportunities to directly study the subducted oceanic crust and seamounts. The International Ocean Discovery Program (IODP) expedition 366 has recovered a few metamorphosed mafic clasts exhumed from the Mariana forearc serpentinite mud volcanoes, e.g., the Fantangisña and Asùt Tesoru seamounts. These mafic clasts have tholeiitic to alkaline affinities with distinct trace elements and Nd-Hf isotopes characteristics, suggesting different provenances and mantle sources. The tholeiites from the Fantangisña Seamount have trace element characteristics typical of mid-ocean ridge basalt. The Pacific-type Hf-Nd isotopic compositions, combined with the greenschist metamorphism of these tholeiites further suggest that they came from the subducted Pacific oceanic crust. The alkali basalts-dolerites from the Fantangisña and Asùt Tesoru seamounts show ocean island basalt (OIB)-like geochemical characteristics. The OIB-like geochemical signatures and the low-grade metamorphism of these alkali basalts-dolerites suggest they came from subducted seamounts that originally formed in an intraplate setting on the Pacific Plate. The Pacific Plate origin of these metabasites suggests they were formed in the Early Cretaceous or earlier.Two types of OIBs have been recognized from alkali metabasites, one of which is geochemically similar to the HIMU-EMI-type OIBs from the West Pacific Seamount Province, and another is similar to the EMII-type OIBs from the Samoa Island in southern Pacific, with negative Nb-Ta-Ti anomalies and enriched Nd-Hf isotopes. Generally, these alkali metabasites are sourced from the heterogeneous mantle sources that are similar to the present South Pacific Isotopic and Thermal Anomaly. This study provides direct evidence for seamount subduction in the Mariana convergent margins. We suggest seamount subduction is significant to element cycling, mantle heterogeneity, and mantle oxidation in subduction zones. 相似文献