Collaborative Research: Storage Duration of Giant Plagioclase Basalts, Deccan Traps, India

知识价值。大量的德干（印度）洪水玄武岩在K/T边界喷发，这是一个与主要动物灭绝（如恐龙）有关的主要地层边界。因此，人们对了解德干火山爆发持续了多长时间以及它对生物进化的影响非常感兴趣。传统的年代测定技术（40Ar/39Ar， K/Ar法）的不确定度为+/- 0.5微米，因此我们不知道整个喷发是持续了几年，100千哩，还是500千哩！根据晶体生长速率数据进行的初步计算表明，西高止山脉地区最大的熔岩包可能在短短50年的时间内喷发出来，这与惊人的喷发速度相对应。目前的项目是一项初步研究，旨在评估一种技术（巨型斜长石斑晶中元素在组成带间的扩散曲线随时间的弛豫），该技术最终可能为量化德干各个岩浆房的活动持续时间提供一种独立的方法。大型复杂带斜长石晶体的成分剖面也将被用来评估它们作为连续熔岩流中携带的晶体之间的“微地层”相关性的潜力，以研究岩浆室模型——也就是说，连续的熔岩是否从经历了多次岩浆侵位、补给、补给和挤压的长期动态储层中喷发出来。这项工作将包括详细的岩石学和晶体尺寸分布研究，以及在华盛顿州立大学工作的微钻和激光烧蚀ICP-MS和佛罗里达国际大学（FIU）的电子探针分析中，在单个现象晶体的组成区域中高精度的微量元素（Mg, Fe, Sr）和87Sr/86Sr剖面。更广泛的影响。这项拟议研究的一个吸引人的方面是，它有可能提供当前同位素和古地磁方法无法实现的时间分辨率。FIU是一个小众机构。该项目将包括一名博士生（Melroy Borges）的教育和培训，也可能包括一名兼职本科生（Kevin Chau）。拟议的工作将促进美国和印度几个机构的研究人员之间的合作。

Intellectual Merit. The bulk of the voluminous Deccan (India) flood basalts erupted at the K/T boundary, a major stratigraphic boundary associated with a major faunal extinction (e.g., the dinosaurs). Hence, there is a great deal of interest in understanding how long the Deccan eruption lasted and what impact it had on biotic evolution. Conventional dating techniques (40Ar/39Ar, K/Ar methods) have an uncertainty of +/- 0.5 m.y., and thus we do not know whether the whole eruption lasted a few years, 100 kyr, or 500 kyr! Preliminary calculations based on crystal growth rate data suggest that the most voluminous lava package from the Western Ghats region could have been erupted in as little as 50 kyr, corresponding to a phenomenal eruption rate. The present project is a pilot study aimed at evaluating a technique (time-dependent relaxation of diffusion profiles of elements across compositional zones in giant plagioclase phenocrysts) that may eventually provide an independent method for quantifying the duration of activities of individual Deccan magma chambers. Compositional profiles across large complexly zoned plagioclase crystals will also be utilized to evaluate their potential as 'micro-stratigraphic' correlations between crystals carried in successive lava flows to investigate magma chamber models - that is, do successive lavas erupt from long-lived dynamic reservoirs that underwent multiple episodes of magma emplacement, recharge, recharge, and extrusion. This work will entail detailed petrographic and crystal-size distribution studies coupled with high precision trace element (Mg, Fe, Sr) and 87Sr/86Sr profiles across compositional zones in individual phenocrysts using microdrill and Laser-ablation ICP-MS at work at Washington State University and electron microprobe analysis at Florida International University (FIU).Broader impacts. An appealing aspect of the proposed study is its potential to deliver time-resolution that is not attainable with current isotopic and paleomagnetic methods. FIU is a minority institution. The project will involve the education and training of a doctoral student (Melroy Borges) and likely will involve one part-time undergraduate (Kevin Chau). The proposed work will promote collaborations between investigators at several institutions in the US and India.