Understanding felsic veins in gabbros drilled by IODP at Atlantis Bank (Southwest Indian Ridge): Formation, metamorphism, and their role as multifunctional pathways for fluid and mass transfer

了解 IODP 在亚特兰蒂斯浅滩(西南印度洋中脊)钻探的辉长岩中的长英质脉:形成、变质作用及其作为流体和质量传递多功能途径的作用

基本信息

  • 批准号:
    408055224
  • 负责人:
  • 金额:
    --
  • 依托单位:
  • 依托单位国家:
    德国
  • 项目类别:
    Infrastructure Priority Programmes
  • 财政年份:
    2018
  • 资助国家:
    德国
  • 起止时间:
    2017-12-31 至 2022-12-31
  • 项目状态:
    已结题

项目摘要

Typical lower crust from slow-spreading mid-ocean ridges, covering about one third of our planet, consists of gabbro which is cut by numerous cm- to dm-sized veins of evolved rocks, so-called "felsic veins". Their mode of formation and their role during hydrothermal alteration of the crust is only poorly investigated. An IODP Expedition drilled recently at Site 1473 on top of the Atlantis Bank (Southwest Indian Ridge, SWIR) into the lower crust, encountering ~ 790 m of massive gabbro, cut by nearly 400 felsic veins, comprising ~1.5% of the drill core, varying in composition from diorites to trondhjemites. The rocks from Hole U1473A offer the unique opportunity for a profound and comprehensive investigation of felsic veins cutting gabbros in slow-spread oceanic crust. The proposed project focusses on three main scientific targets:(1) The objective of theme 1 is to test the model of formation of the felsic veins in Hole U1473A. Do they represent the solidification of melts generated as very last step of MORB differentiation, or are they generated by partial melting of gabbros by percolating fluids, or by liquid immiscibility in an evolved MORB system? Our methodological approach to prove this is bulk rock geochemical analysis, geochemical modeling, and by an experimental simulation of partial melting. (2) Theme 2 focuses on the nature of the transition between latest magmatic processes and the first imprint of hydrothermal activity, which has also the potential to trigger magmatic processes. This theme includes the important question, how deep does water penetrate down oceanic detachment faults. This has broader implications also for the rheology of the just accreted "solid" crust. Key for unravelling these poorly investigated issues in the magmatic-to-metamorphic regime during accretion/uplifting of slow-spread oceanic crust lies in the careful investigation of high-temperature amphiboles, and their inherent information on formation temperature, as well as in the accurate estimation of the wet solidus temperature of the specific, often evolved gabbros from Hole U1473A.(3) Basis of theme 3 is the observation that the felsic veins are much more altered than the host gabbros and that the metamorphic assemblages in the felsic veins suggest varying metamorphic conditions from high temperatures (higher amphibolite facies) down to low temperatures (sub-greenschist facies).These observations raise the questions: what is the role of the felsic veins in the metamorphic development during the hydrothermal cooling of the crust and which are the amounts of fluids and masses transferred along these veins? Key approaches for this topic are the careful analysis of fluid bearing minerals (amphiboles, apatite), accurate temperature estimations by geothermometry in combination with the analysis of the local metamorphic equilibria, estimating the flux of seawater-derived fluids by Sr and oxygen isotope analysis, and thermodynamic computations.
典型的下地壳来自缓慢扩张的大洋中脊,覆盖了我们地球的大约三分之一,由辉长岩组成,它被许多厘米到dm大小的演化岩石矿脉切割,即所谓的长英质矿脉。它们的形成方式及其在地壳热液蚀变过程中的作用研究得很少。IODP探险队最近在亚特兰蒂斯岸(西南印度洋海脊,SWIR)顶部的1473号地点钻探下地壳,遇到了约790米的巨大辉长岩,被近400条长英质矿脉切割,占钻芯的约1.5%,成分从闪长岩到奥长花岗岩不等。来自U1473A孔的岩石为深入而全面地研究缓慢扩张的洋壳中的长英脉切割辉长岩提供了独特的机会。该项目的重点是三个主要的科学目标:(1)主题1的目标是测试U1473A孔中长英质矿脉的形成模式。它们代表了作为MORB分异的最后一步而产生的熔体的凝固,还是由渗流流体使辉长岩部分熔化产生的,还是由进化的MORB系统中的液体不混溶产生的?我们的方法论方法是通过大量岩石的地球化学分析、地化模拟和部分熔融的实验模拟来证明这一点。(2)主题2侧重于最新岩浆作用和第一次热液活动印记之间过渡的性质,这也有可能触发岩浆作用。这一主题包括一个重要的问题,水向下渗透到大洋滑脱断层有多深。这对刚吸积的“固体”地壳的流变学也有更广泛的影响。要解决这些在缓慢扩张洋壳吸积/抬升过程中岩浆-变质过程中研究不足的问题,关键在于仔细研究高温角闪石及其关于地层温度的固有信息,以及准确估计特定岩石的湿固相线温度。通常从U1473A孔演化出来的辉长岩。(3)主题3的基础是观察到长英脉的变化比寄主辉长岩大得多,长英脉中的变质组合表明从高温(高角闪岩相)到低温(亚绿片岩相)的变质条件不同。这些观察提出了这样的问题:在地壳热液冷却期间,长英脉在变质发展中起什么作用?沿着这些脉转移的流体和物质的数量是多少?解决这一问题的关键方法是仔细分析含流体矿物(角闪石、磷灰石),结合局部变质平衡分析,通过地温测量准确估计温度,通过锶和氧同位素分析估计海水来源流体的通量,以及热力学计算。

项目成果

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Professor Dr. Jürgen Koepke其他文献

Professor Dr. Jürgen Koepke的其他文献

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{{ truncateString('Professor Dr. Jürgen Koepke', 18)}}的其他基金

A profile of multiple sulfur, oxygen, strontium isotopes and related chalcophile elements through lower slow-spreading crust (IODP Expedition 360, Atlantis Bank, Southwest Indian Ridge)
低速扩张地壳中多种硫、氧、锶同位素和相关亲铜元素的分布图(IODP Expedition 360,亚特兰蒂斯浅滩,西南印度洋中脊)
  • 批准号:
    319774021
  • 财政年份:
    2016
  • 资助金额:
    --
  • 项目类别:
    Infrastructure Priority Programmes
Silicate liquid immiscibility and the formation of Fe (±Ti ±P ±F ±REE) ore deposits
硅酸盐液体不混溶性与Fe(±Ti±P±F±REE)矿床的形成
  • 批准号:
    268008671
  • 财政年份:
    2015
  • 资助金额:
    --
  • 项目类别:
    Research Grants
Melt/rock interaction and fractional crystallization in the lower crust at Hess Deep Rift, East Pacific Rise: A combined analytical and experimental study
东太平洋海隆赫斯深裂谷下地壳熔体/岩石相互作用和分异结晶:分析与实验相结合的研究
  • 批准号:
    279047586
  • 财政年份:
    2015
  • 资助金额:
    --
  • 项目类别:
    Infrastructure Priority Programmes
Assimilation, contamination and felsic melt generation at the top of the axial melt lens at fast-spreading oceanic crust: Combined geochemical and experimental investigations at the dike/gabbro transition from IODP Site 1256 (East Pacific Rise)
快速扩张的洋壳轴向熔体透镜体顶部的同化、污染和长英质熔体生成:对 IODP 站点 1256(东太平洋海隆)的岩脉/辉长岩转变进行地球化学和实验联合研究
  • 批准号:
    224563012
  • 财政年份:
    2012
  • 资助金额:
    --
  • 项目类别:
    Infrastructure Priority Programmes
The Gabbro/Dike transition in oceanic crust generated at slow- and ultraslow-spreading ocean ridge systems
慢速和超慢速扩张的洋脊系统产生的洋壳中的辉长岩/岩脉转变
  • 批准号:
    227716517
  • 财政年份:
    2012
  • 资助金额:
    --
  • 项目类别:
    Research Grants
Additional pre-survey for the project "Establishing a reference profile for fast-spreading oceanic crust: Petrology and geochemistry of the Wadi Gideah cross section in the Oman ophiolite"
“为快速扩张的洋壳建立参考剖面:阿曼蛇绿岩中 Wadi Gideah 横截面的岩石学和地球化学”项目的额外预调查
  • 批准号:
    214445455
  • 财政年份:
    2011
  • 资助金额:
    --
  • 项目类别:
    Infrastructure Priority Programmes
Pre-survey: Magmatic evolution of the Tiger gabbroic complex (Northern Victoria Land, Antarctica): insights into the lower crust of a Cambrian immature Island Arc
预调查:虎辉长岩杂岩体的岩浆演化(南极洲北维多利亚地):深入了解寒武纪未成熟岛弧的下地壳
  • 批准号:
    130419963
  • 财政年份:
    2009
  • 资助金额:
    --
  • 项目类别:
    Infrastructure Priority Programmes
Time scales for vertically moving axial magma chambers at fast-spreading ocean ridges and involved magmatic reactions: Insights from IODP Site 1256
快速扩张的洋脊上垂直移动的轴向岩浆室的时间尺度以及涉及的岩浆反应:来自 IODP Site 1256 的见解
  • 批准号:
    143034347
  • 财政年份:
    2009
  • 资助金额:
    --
  • 项目类别:
    Infrastructure Priority Programmes
High temperature hydrothermal activity in the deep oceanic crust: Experiments and investigations on natural rocks in the Oman ophiolite
深洋地壳的高温热液活动:阿曼蛇绿岩天然岩石的实验和研究
  • 批准号:
    116858737
  • 财政年份:
    2009
  • 资助金额:
    --
  • 项目类别:
    Research Grants
A combined petrological, geochemical and geochronological study of the magmatic rocks surrounding the Logatchev hydrothermal field.
对洛加切夫热液田周围岩浆岩进行岩石学、地球化学和地质年代学的综合研究。
  • 批准号:
    54904092
  • 财政年份:
    2007
  • 资助金额:
    --
  • 项目类别:
    Priority Programmes

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    2019
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    RGPIN-2014-06063
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  • 批准号:
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