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首页> 外文期刊>Journal of Asian earth sciences >Plagioclase as recorder of magma chamber processes in the Deccan Traps: Sr-isotope zoning and implications for Deccan eruptive event
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Plagioclase as recorder of magma chamber processes in the Deccan Traps: Sr-isotope zoning and implications for Deccan eruptive event

机译：斜长石作为Deccan陷阱中岩浆室过程的记录器：Sr同位素分区及其对Deccan爆发事件的影响

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摘要

Deccan Trap flood basalt volcanism reached its peak 65.5 (±1) million years ago, giving rise to a 2.7 km thick lava pile that formed the Western Ghats range near Mumbai. The total duration of this activity cannot be constrained better than ±1 Ma by conventional Ar-dating techniques. It is also difficult to know whether there were short bursts of tremendous volcanic activity within that period which could have significantly impacted global climate. Here we employ diffusion relaxation modeling of ~(87)Sr/~(86)Sr zoning in plagioclase to obtain a better resolution on the life cycle of a magma chamber in order to provide a minimum constraint on the duration of the Western Ghats volcanic episode. The analyzed crystals are 2-5 cm long and occur in so-called Giant Plagioclase Basalt flows that mark the tops of the oldest formations of the Western Ghats. In the formation studied, such crystals may have recorded the life cycle of the magma chamber that fed the preceding flows. Our diffusion modeling yields 780 years for the maximum residence time for 5 cm long plagioclase crystals in the magma chamber and a mean growth rate of 2.03 × 10~(-10) cm s~(-1). Assuming continuous crystal growth while the underlying pile was being emplaced gives us a combined maximum rate of 0.13 m yr~(-1) for incubation and extrusion of the lava. Using this rate we estimate that the peak volcanic activity lasted a minimum of 21,100 years. A short duration for the Deccan would preclude AFC contamination processes during emplacement of the bulk of Deccan lavas.
机译：Deccan Trap洪水玄武岩火山活动在6百万（±1）百万年前达到顶峰，形成了2.7 km厚的熔岩堆，形成了孟买附近的Western Ghats山脉。常规Ar约会技术不能将这项活动的总持续时间约束在±1 Ma以下。也很难知道在此期间是否有短暂的巨大火山活动爆发，这可能对全球气候产生重大影响。在这里，我们采用斜长石中〜（87）Sr /〜（86）Sr分区的扩散松弛模型来获得岩浆室生命周期的更好分辨率，从而对西高止山脉火山爆发的持续时间提供最小的限制。分析的晶体长2-5厘米，出现在所谓的巨型斜长石玄武岩流中，标志着西高止山脉最古老地层的顶部。在所研究的地层中，此类晶体可能已记录了注入先前流的岩浆室的生命周期。我们的扩散模型可以得出780年的最长停留时间，即5 cm长斜长石晶体在岩浆室内的平均停留时间为2.03×10〜（-10）cm s〜（-1）。假设在放置下面的桩的同时晶体连续生长，则熔岩的孵化和挤出的最大综合速率为0.13 m yr〜（-1）。使用此速率，我们估计火山活动高峰持续了至少21,100年。 Deccan的持续时间很短，可以防止在放置大量Deccan熔岩的过程中AFC污染。

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  • 来源
    《Journal of Asian earth sciences》 |2014年第15期|95-101|共7页
  • 作者

    Melroy R. Borges; Gautam Sen; Garret L. Hart; John A. Wolff; D. Chandrasekharam;

  • 作者单位

    Department of Earth & Environment, Florida International University, Miami, FL 33199, USA,Corning Incorporated, One Museum Way, HP-ME-02-02, Corning, NY 14831, USA;

    Department of Earth & Environment, Florida International University, Miami, FL 33199, USA,American University of Sharjah, Sharjah 26666, UAE;

    School of Earth and Environmental Sciences, Washington State University, Pullman, WA 99164, USA,Pacific Northwest National Laboratory, Richland, WA 99352, USA;

    School of Earth and Environmental Sciences, Washington State University, Pullman, WA 99164, USA;

    Department of Earth Sciences, Indian Institute of Technology, Mumbai 400076, India;

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  • 正文语种 eng
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  • 关键词

    Deccan Traps; Plagioclase residence times; Flood basalts; Sr isotope zoning; Isotopic diffusion; Crystal growth rates; LA-ICPMS;

    机译：德干陷阱斜长石停留时间;洪水玄武岩;Sr同位素分区;同位素扩散;晶体生长速率;等离子体质谱仪;

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