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

大的火成岩省(嘴唇)代表着地球上最强烈的火山活动的表现。它们既出现在陆地上，也出现在海洋中，覆盖了数十万平方公里的面积，在数百公里长的玄武岩熔岩流下厚厚地堆积着。类似的现象构成了太阳系其他类地行星上火山活动的主体，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，但许多事件都与动植物物种的大规模灭绝有关。尽管嘴唇在地球的进化中很重要，但人们对嘴唇的物理喷发过程知之甚少。该项目旨在了解嘴唇侵位过程中喷发风格的变化，重点是从来自大型中央火山的复杂熔岩流过渡到来自拉长火山裂缝的大片状熔岩流。该项目将结合印度德干圈闭(白垩纪-古近纪大灭绝时期的嘴唇，65年前)的野外工作，以及使用有效模拟熔岩流动行为的模拟材料进行的实验室实验相结合。这种喷发式的转变似乎是大陆唇形的一个基本特征，部分控制了这些喷发的气体的释放，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-67Myr之前，是目前覆盖印度次大陆中西部约50万平方公里的大陆唇形构造，在侵位时可能是其两到三倍大。最近的研究表明，在德干地层的下部普遍存在复合熔岩流，而在上层熔岩建造中主要存在简单的熔岩流。类似的转变在其他嘴唇中也有记载(例如，Etendeka，北大西洋火成岩省，埃塞俄比亚圈闭)，这表明许多嘴唇结构的共同进化。从历史上看，复合流被解释为来自较低渗漏率的大型中央屏蔽状火山，而简单的片状流动被认为来自长期保持高渗漏率的单个、分散的裂缝和点状喷口。这些历史解释告诉我们最初的假设：(1)建筑物结构的转变发生在从复合到简单的流动转变(2)熔岩流动形态取决于喷发速率事件。建立岩浆从火山馈送系统输送到地球上有记录以来最长熔岩流动的远端部分的方式，对于了解熔岩流动的热收支、嘴唇的结构以及在此类喷发期间向大气中释放挥发性物质至关重要。野外工作的目的是量化不同地层中复合流动和简单流动的普遍程度，确定流动方式转变的时间尺度，并记录流动形态的横向变化。这项工作将得到模拟熔岩流动的模拟实验室实验的补充，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，如渗漏速度、通风口的空间分布和幕式流动模式。在实验期间，将使用两种新的方法来测量热条件和冷却：依赖温度的平面激光诱导荧光将测量流动中的温度分布，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.