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

智力优势。大量德干（印度）洪水玄武岩的大部分在K/T边界爆发，这是一个与主要动物灭绝有关的主要地层边界（例如，恐龙）。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产生了什么影响非常感兴趣。传统的测年技术（40 Ar/39 Ar，K/Ar法）的不确定度为+/- 0.5百万年，因此，我们不知道整个喷发持续了几年，10万年，还是50万年！根据晶体生长速率数据的初步计算表明，西高止山脉地区最大的熔岩包可能在短短5万年内喷发，相当于惊人的喷发速率。本项目是一个试点研究，旨在评估一种技术（随时间变化的松弛的元素扩散分布在巨型斜长石斑晶组成区），最终可能提供一个独立的方法，量化的活动持续时间的个人德干岩浆房。也将利用大型复杂分区斜长石晶体的成分剖面来评估其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，以研究岩浆房模型-也就是说，连续熔岩从经历了多次岩浆侵位，补给，补给和挤出的长寿命动态储层中喷发。这项工作将需要详细的岩相学和晶体粒度分布研究，以及高精度的微量元素（Mg、Fe、Sr）和87 Sr/86 Sr剖面图，这些剖面图是利用华盛顿州立大学的微钻和激光消融ICP-MS以及佛罗里达国际大学的电子微探针分析在单个斑晶的成分带上进行的。这项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达到的时间分辨率。金融情报室是一个少数机构。该项目将涉及一名博士生（Melroy Borges）的教育和培训，并可能涉及一名兼职本科生（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.