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

大火成岩省（LIPs）代表了地球上最强烈的火山活动。 它们出现在陆地和海洋中，覆盖面积达数十万平方公里，覆盖在数百公里长的玄武岩熔岩流的厚厚堆积下。类似的现象构成了太阳系其他类地行星上的大部分火山活动，在地球上，它们被认为会破坏气候和海洋的化学平衡。虽然这些事件在我们星球的历史上是罕见的，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LIPs的物理喷发过程知之甚少。该项目旨在了解LIP就位过程中喷发方式的变化，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片流的转变。该项目将结合印度德干圈闭（6500万年前古近纪大规模灭绝期间的LIP）的野外工作和使用模拟材料的实验室实验，这些材料有效地模拟了熔岩流的行为。这种喷发方式的转变似乎是大陆LIP的一个基本特征，并部分控制了这些喷发的气体释放，因此也控制了它们潜在的气候和环境影响。德干圈闭形成于6400 - 6700万年前，是一个大陆LIP，目前覆盖印度次大陆中部和西部约50万平方公里，在安放时可能比现在大两到三倍。最近的研究表明，在德干地层的下部普遍存在复合熔岩流，而在上部熔岩地层中则主要是简单熔岩流。在其他LIP中也记录了类似的转变（例如，Etendeka，北大西洋火成岩省，埃塞俄比亚圈闭），这表明了许多LIP的建筑共同演变。从历史上看，复合流被解释为来源于大中央盾状火山在相对较低的渗出率，而简单的片流被认为是源于个人，分散的裂缝和点喷口维持高渗出率的延长时间。这些历史的解释告知我们的假设：（1）在建筑物的结构发生转变，在化合物到简单的流动过渡（2）熔岩流的形态是依赖于渗出率epidicityEstablishing的方式，岩浆从火山馈线系统提供的最长的熔岩流在地球上记录的远端部分是必不可少的了解熔岩流的热预算，建筑LIPs，并释放到大气中的挥发性物质在这样的喷发。野外工作的目的是量化不同地层中复合流和简单流的普遍性，确定流态过渡的时间尺度，并记录流态的横向变化。这项工作将得到模拟熔岩流的模拟实验室实验的补充，这些实验旨在隔离控制复合简单流动转变和流动形态的因素，例如渗出率、喷口的空间分布和情景流动模式。两种新的方法将用于测量实验过程中的热条件和冷却：温度相关的平面激光诱导荧光将测量流内的温度分布，红外相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.