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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Evolution of shield-building and rejuvenescent volcanism of Mauritius
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Evolution of shield-building and rejuvenescent volcanism of Mauritius

机译：毛里求斯建立盾构和复兴火山的演变

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摘要

We report chemical and isotopic analyses of 68 samples and ~(40)Ar/~(39)Ar ages of 47 samples from Mauritius undertaken to understand the compositional evolution of the volcano and its causes through time. New ~(40)Ar/~(39)Ar ages show that construction of the Mauritius shield was well underway by 8.9 Ma, 1.1 m.y. earlier than previously thought and that the hiatus between the Intermediate and Younger Series was shorter than previously thought, as eruption of the rejuvenescent Intermediate Series continued through at least 1.66 Ma and Younger Series volcanism began by at least 1.0 Ma. Eruption frequency over the last 50 ka has been rather typical of Younger Series volcanism over the last 400 ka and future eruptions are possible. Although outcrops of the Intermediate Series lavas are confined to the Southwest, Intermediate Series are present beneath Younger Series flows in drill cores throughout the island. We estimate the total volume of rejuvenescent lavas at -35 km3 or about 0.05% of the volume of the volcano, similar to rejuvenescent volume fractions on Hawaiian volcanoes. As earlier studies found, Older Series lavas, which on average are slightly normatively silica-saturated, are somewhat more incompatible-element enriched than are the Intermediate and Younger Series, which are both slightly silica-undersaturated on average. Mean Sr and Nd isotope ratios of the Intermediate and Younger Series are nearly identical, but mean Pb isotope ratios, La/Sm, Nb/Y, and Nb/Zr of the Intermediate Series are higher than in the Younger Series. New high precision Pb isotope data, which shows considerably less scatter than previously published data, plot between the Older Series and basalts of the Central Indian Ridge, allowing the possibility that the source of the rejuvenescent lavas is a mixture of this plume and depleted mantle. We propose two possible explanations for the composition of rejuvenescent lavas. The first is that plume-derived melts reacted with deep lithosphere to form pyroxenite veins during the early shield-building stage. Later, these veins melted as a consequence of conductive heating of the lithosphere by the plume to produce the rejuvenescent lavas. Alternatively, rejuvenescent lavas may be derived from a sheath of thermally entrained mantle that surrounds the plume and is a mixture of plume material and depleted upper mantle.
机译：我们报告了来自毛里求斯的68个样品和〜（40）Ar /〜（39）Ar年龄的68个样品的化学和同位素分析，旨在了解火山的组成演变及其随时间的原因。新的〜（40）Ar /〜（39）Ar年龄表明，到8.9 Ma，1.1 m.y时，毛里求斯盾构的施工正在进行中。早于先前的想法，中级和雅戈尔系列之间的裂隙比先前所想的要短，因为复兴的中级系列的爆发持续了至少1.66 Ma，而雅戈尔系列的火山活动开始了至少1.0 Ma。最近50 ka的喷发频率是Younger系列火山在最近400 ka的典型喷发，将来可能会喷发。尽管中级系列熔岩的露头仅限于西南地区，但中级系列仍存在于整个岛屿的岩心中的年轻系列下。我们估计复兴火山岩的总体积为-35 km3，约占火山体积的0.05％，与夏威夷火山的复兴火山岩体积分数相似。正如较早的研究发现，平均而言，较老系列的熔岩的二氧化硅含量稍为规范性饱和，比中级和较年轻的熔岩（它们的平均含量均略低于二氧化硅）富集了一些不相容元素。中级和年轻系列的平均Sr和Nd同位素比几乎相同，但中级系列的平均Pb同位素比La / Sm，Nb / Y和Nb / Zr高于Younger系列。在较旧的系列和中印度洋脊玄武岩之间绘制了新的高精度铅同位素数据，该数据显示的散布比以前发布的数据要小得多，这使复兴的熔岩来源可能是这种羽流和地幔的混合物。我们提出了关于复兴熔岩的两种可能的解释。首先是烟羽衍生的熔体在盾构建立初期就与深层岩石层反应形成了辉石岩脉。后来，由于羽流对岩石圈的传导加热，这些静脉融化，产生了年轻的熔岩。替代地，复兴的熔岩可以源自热夹带的地幔的鞘，该热夹带的地幔围绕着羽流并且是羽流材料和贫化的上地幔的混合物。

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  • 来源
    《Journal of Volcanology and Geothermal Research》 |2011年第2期|p.47-66|共20页
  • 作者

    Jacob Moore; William M. White; Debajyoti Paul; Robert A. Duncan; Wafa Abouchami; Stephen J.G. Galer;

  • 作者单位

    Department of Earth and Atmospheric Sciences. Cornell University, Snee Hall, Ithaca, NY 14583, USA,Now at Ellington & Associates, Inc., 1414 Lumpkin Road, Houston, TX 77043, USA;

    Department of Earth and Atmospheric Sciences. Cornell University, Snee Hall, Ithaca, NY 14583, USA;

    Department of Earth and Environmental Science, The University of Texas San Antonio, One UTSA Circle, San Antonio, TX 78249, USA,Now at Department of Civil Engineering (Geosciences), Indian Institute of Technology Kanpur, 208016 (UP), Kanpur, India;

    College of Oceanic and Atmospheric Sciences, Oregon State University, Ocean Administration Building 104, Corvallis, OR 97331, USA;

    Max-Planck-Institut fuer Chemie, Abteilung Biogeochemie, Postfach 3060, D-55020 Mainz, Germany;

    Max-Planck-Institut fuer Chemie, Abteilung Biogeochemie, Postfach 3060, D-55020 Mainz, Germany;

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