Building the Deccan Traps: What Can We Learn from Lava Flow Morphology in Large Igneous Provinces?

大火成岩省（lip）是地球上火山活动最强烈的表现形式。它们既发生在陆地上，也发生在海洋中，覆盖了数十万平方公里的区域，覆盖着数百公里长的玄武岩熔岩流。类似的现象构成了太阳系中其他类地行星上的大部分火山活动，而在地球上，它们被认为会破坏气候和海洋的化学平衡。虽然这些事件在地球历史上很罕见，但许多都与动植物物种的大规模灭绝有关。尽管它们在我们星球的进化中很重要，但人们对lip的物理喷发过程知之甚少。该项目旨在了解LIP就位过程中喷发风格的变化，重点关注从大型中央火山喷出的复杂熔岩流到源自细长火山裂缝的广泛板流的转变。该项目将结合在印度德干圈闭（白垩纪-古近纪大灭绝期间形成的一个LIP， 65万年前）的实地考察和实验室实验，使用模拟材料有效地模拟熔岩流的行为。这种喷发方式的转变似乎是大陆lip的一个基本特征，并在一定程度上控制了这些喷发产生的气体的释放，因此也控制了它们对气候和环境的潜在影响。德干圈闭形成于64-67亿年前，是目前覆盖印度次大陆中部和西部约50万平方公里的大陆性圈闭，在其形成时可能要大两到三倍。最近的研究表明，复合熔岩流普遍存在于德干地层的下部，而简单的熔岩流则主导着上部的熔岩地层。类似的转变在其他lip中也有记录（例如，Etendeka，北大西洋火成岩省，埃塞俄比亚陷阱），这表明许多lip的建筑都有共同的演变。从历史上看，复合流被解释为来自相对低渗出率的大型中央盾状火山，而简单的片状流被认为起源于个体，分散的裂缝和点喷口，在很长一段时间内保持高渗出率。这些历史解释为我们的初始假设提供了信息：(1)大厦结构的转变发生在复合流向简单流转变的过程中(2)熔岩流形态依赖于渗出速率的片段。建立岩浆从火山补给系统输送到地球上有记录的最长熔岩流的远端部分的方式，对于理解熔岩流的热预算、LIPs的结构、以及火山喷发时挥发性物质释放到大气中。实地工作的目的是量化不同地层中复合和简单流动的普遍性，确定流动风格转变的时间尺度，并记录流动形态的横向变化。这项工作将辅以模拟熔岩流动的模拟实验室实验，这些实验旨在分离控制复合-简单流动转变和流动形态的因素，如渗出率、喷口的空间分布和幕式流动模式。两种新方法将用于测量实验中的热条件和冷却：温度相关的平面激光诱导荧光将测量流动中的温度分布，红外摄像机将测量表面温度的变化。

Large igneous provinces (LIPs) represent the most intense manifestation of volcanism on Earth. They occur both on land and in the oceans and cover areas of hundreds of thousands of square kilometers under thick stacks of basaltic lava flows hundreds of kilometers in length. Similar phenomena constitute the bulk of volcanism on other terrestrial planets in the solar system, and on Earth they are known to disrupt climate as well as the chemical balance of the oceans. Though these events are rare in our planet's history, many are linked with mass extinctions of animal and plant species. Despite their importance in our planet's evolution, the physical eruption processes of LIPs are poorly understood. This project aims to understand the changes in eruptive style during the course of LIP emplacement, focusing on the transition from complex lava flows fed from large central volcanoes to extensive sheet flows sourced from elongate volcanic cracks. The project will use a combination of fieldwork in the Deccan Traps of India (a LIP emplaced during the Cretaceous-Paleogene mass extinction, 65 Myr ago) and laboratory experiments using analog materials that effectively mimic the behavior of lava flows. This transition in eruptive style appears to be a fundamental feature of continental LIPs and partly controls the release of gases from these eruptions, and therefore also controls their potential climatic and environmental impact.The Deccan Traps, formed 64-67 Myr ago, are a continental LIP presently covering ~500,000 km2 of the central and western Indian subcontinent, and likely were two to three times larger at the time of emplacement. Recent work has shown the prevalence of compound lava flows in the lower part of the Deccan stratigraphy, whereas simple flows dominate the upper lava formations. Similar transitions have been documented in other LIPs (e.g., Etendeka, North Atlantic Igneous Province, Ethiopian Traps), suggesting a common evolution of architecture for many LIPs. Historically, compound flows have been interpreted to be sourced from large central shield-like volcanoes at relatively low effusion rates, whereas simple sheet flows are thought to originate from individual, scattered fissure and point vents sustaining high effusion rates for prolonged periods of time. These historical interpretations inform our starting hypotheses:(1) A shift in edifice architecture occurs at the compound-to-simple flow transition(2) Lava flow morphology is dependent on effusion rate episodicityEstablishing the manner in which magma is delivered from the volcanic feeder system to the distal parts of the longest lava flows documented on Earth is essential to understanding the thermal budget of lava flows, the architecture of LIPs, and the release of volatile species into the atmosphere during such eruptions. Fieldwork will aim to quantify the prevalence of compound and simple flows in different formations, determine the timescale of the transition in flow style, and document lateral changes in flow morphology. This work will be complemented by analog laboratory experiments that simulate lava flows and have been designed to isolate the factors that control the compound-simple flow transition and flow morphology, such as effusion rate, spatial distribution of vents, and episodic flow patterns. Two novel approaches will be used to measure thermal conditions and cooling during the experiments: temperature-dependent planar laser-induced fluorescence will measure the temperature distribution within the flows, and an infrared camera will measure changes in surface temperatures.