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CSEDI: Constraining the mechanisms of melt transport, storage, and crustal contamination from temporal geochemical variations in monogenetic vents

CSEDI：限制单源喷口时间地球化学变化造成的熔体传输、储存和地壳污染机制

基本信息

批准号：
1301621
负责人：
John Lassiter
金额：
$ 33.55万
依托单位：
University of Texas at Austin
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2013
资助国家：
美国
起止时间：
2013-05-01 至 2016-04-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1301621&HistoricalAwards=false
关键词：
CSEDI Constraining mechanisms melt transport

项目摘要

Monogenetic vents are relatively small volcanoes that are active for a single eruption over a period of a few months to a few years, in contrast to more typical volcanoes that are gradually built up over many different eruptions and which are typically intermittently active for 10s of thousands of years or longer. Monogenetic vents often occur in clusters, and are a common type of volcanism in many tectonic settings. Several monogenetic vent fields occur in or near high-population-density areas, including Auckland, New Zealand and Mexico City, Mexico. Therefore, monogenetic vents represent a significant volcanic hazard. Previous studies have shown that the compositions of the ash and lava erupted from a monogenetic vent during the course of an eruption often varies systematically over time. The cause of this variability is not clear, but it most likely reflects either processes involved in melt generation and extraction from the mantle, or melt storage in the continental crust and melt/crust interaction prior to eruption. A better understanding of the cause(s) of the chemical variations observed in monogenetic vent eruptions would provide scientists with a better understanding of the plumbing system that feeds these volcanoes. This in turn will allow better prediction of the precursor signals that may signal an impending eruption.This study will combine numerical modeling of melt transport and storage processes with detailed geochemical analyses of material erupted from selected monogenetic vent eruptive sequences to better constrain the processes of melt generation, ascent, and storage that precede the eruption of monogenetic vents. Different hypothesized mechanisms for generating chemical variations in monogenetic vent sequences (e.g., reactive melt transport in the mantle or progressive draining of magma sills that are emplaced in the shallow crust prior to eruption) will produce different temporal chemical variations. We will compare model predictions with observations to constrain the likely origin of these variations, and then use the observed variations to extract information on important variables related to melt generation, transport, and storage such as the size of chemical heterogeneities in the mantle source region, the volume and geometry of magma storage chambers in the crust, and the time interval between melt injection into the crust and subsequent eruption of this stored magma. This information can be used in future studies to predict the most likely signals that may indicate an impending eruption (e.g., upward ground deformation due to magma injection) as well as the likely time lag between these signals and an actual eruption. The proposed study with therefore both improve our overall understanding of a geologically important and widespread style of continental volcanism, and improve our ability to evaluate and plan for the risks inherent in possible future monogenetic vent eruptions.

单成因喷口是相对较小的火山，在几个月到几年的时间内进行一次喷发，而更典型的火山则是在许多不同的喷发中逐渐建立起来的，并且通常间歇性地活跃数十万年或更长时间。单成因喷口经常成群出现，是许多构造环境中常见的火山作用类型。几个单成因喷口区位于人口密度高的地区或附近，包括新西兰的奥克兰和墨西哥的墨西哥城。因此，单成因喷口是一个重大的火山危险。以前的研究表明，在喷发过程中，从单成因喷口喷出的火山灰和熔岩的成分往往随着时间的推移而系统地变化。这种变化的原因尚不清楚，但它很可能反映了熔体生成和从地幔中提取的过程，或熔体在大陆地壳中的储存和喷发前熔体/地壳的相互作用。更好地了解在单成因喷口喷发中观察到的化学变化的原因将使科学家更好地了解为这些火山提供燃料的管道系统。这反过来又将使更好地预测的前兆信号，可能预示着即将爆发。这项研究将结合联合收割机的熔体运输和存储过程的数值模拟，详细的地球化学分析的材料从选定的单成因喷口喷发序列，以更好地约束熔体生成，上升和存储的过程之前的单成因喷口喷发。在单成因喷口序列中产生化学变化的不同假设机制（例如，地幔中的反应性熔体迁移或喷发前位于地壳浅部的岩浆岩床的逐渐排出）将产生不同的时间化学变化。我们将比较模型预测与观测结果，以限制这些变化的可能来源，然后使用观测到的变化来提取与熔体生成，运输和储存有关的重要变量的信息，例如地幔源区化学不均匀性的大小，地壳中岩浆储存室的体积和几何形状，以及熔体注入地壳和随后这些储存的岩浆喷发之间的时间间隔。这些信息可用于未来的研究，以预测最可能的信号，可能表明即将爆发（例如，由于岩浆注入导致的地面向上变形）以及这些信号与实际喷发之间可能的时间滞后。因此，拟议的研究既提高了我们对地质上重要的和广泛的大陆火山作用的全面了解，也提高了我们评估和规划未来可能的单成因喷口喷发所固有的风险的能力。