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

智力上的功绩。大量的德干(印度)洪水玄武岩在K/T边界喷发，这是一条与大型动物群灭绝(例如恐龙)有关的主要地层边界。因此，人们非常有兴趣了解德干火山喷发持续了多久，以及它对生物进化产生了什么影响。传统的测年技术(40Ar/39Ar，K/Ar法)的不确定度为+/-0.5m.Y.因此，我们不知道整个喷发持续了几年，100KYR，还是500KYR！根据晶体生长速度数据进行的初步计算表明，来自西高止地区的最大体积的熔岩包可能在短短50KYR内喷发，对应于惊人的喷发速度。本项目是一项试验性研究，旨在评估一项技术(元素在巨型斜长石斑晶成分带上的扩散曲线随时间变化的松弛)，该技术可能最终提供一种独立的方法来量化各个德干岩浆室的活动持续时间。还将利用大型、复杂分带的斜长石晶体的成分剖面来评估它们作为连续熔岩流中携带的晶体之间的微观地层对比的潜力，以研究岩浆室模型-即连续的熔岩是否从经历了多次岩浆侵位、补给、补给和挤出的长期动态储集层喷发。这项工作将需要详细的岩相学和晶体粒度分布研究，以及高精度的痕量元素(镁、铁、锶)和在单个斑晶成分带上的87Sr/86Sr剖面，使用在华盛顿州立大学工作的微钻和激光烧蚀电感耦合等离子体质谱，以及在佛罗里达国际大学(FIU)的电子探针分析。这项拟议研究的一个吸引人的方面是，它有可能提供目前的同位素和古地磁方法无法达到的时间分辨率。金融情报室是一家少数族裔机构。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)。这项拟议的工作将促进美国和印度几个机构的调查人员之间的合作。

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.