Investigating the relationship between flood basalt volcanism, climate change and mass extinction using novel proxies for volcanism in marine sediments ('MagmaTrace')

四个最大的质量灭绝的中生代（结束瓜达卢佩，二叠纪-三叠纪，三叠纪末，白垩纪末），以及几个二级灭绝事件，同时发生大陆洪水玄武岩事件。人们普遍认为，大规模的火山活动会导致环境变化，通常包括迅速和显着的全球变暖和海洋缺氧，这可能会引发大规模的灭绝。然而，改变气候的气体（CO2、SO2、CH 4、卤素）的确切性质及其来源（岩浆脱气、变质地壳沉积物、地幔中再循环的地壳物质）仍不清楚。这些问题可以通过确定洪水、玄武岩火山活动以及环境和生物变化的相对持续时间和时间来解决。然而，这些过程的时间尺度小于10^6年，可能是10^4-10^5年（与目前人为温室气体释放的速度相当），因此超出了放射性测年技术的时间分辨率。我们将开发沉积物中火山活动的新的微量元素替代物，使我们能够通过分析沉积剖面来确定火山活动、气候变暖和灭绝的相对时间。通过直接测量活火山的火山气体和火山升华物，确定了火山气体中高浓度的挥发性微量元素，包括Hg、Tl、In、Pb、Bi、Cd、Te、Se、Sn、Cs、Sb和As。在火山活动中，这些元素被释放到大气中，后来被结合到沉积物中。它们在沉积物中的相对浓度代表了火山活动强度的一个替代指标。迄今为止，只有汞被探索作为火山活动的替代物，但汞的浓度也受到沉积物有机含量的影响，其他元素以前没有详细研究过。我们将测量Changhsingian-Indian（二叠纪-三叠纪）和Pliensbachian-Toarcian边界沉积物中的挥发性火山成因微量元素，以便将这些沉积物中的古气候和化石记录与西伯利亚和Karoo洪水玄武岩岩浆活动的时间联系起来，可能分辨率超过10，000年。这些结果将揭示溢流玄武岩火山作用影响气候和生命的时间尺度，以及导致环境变化的气体的起源和性质。

Four of the largest mass extinctions of the Phanerozoic (end Guadalupian, Permian-Triassic, end Triassic, and end Cretaceous) as well as several second-order extinction episodes, occurred simultaneously with continental flood basalt events. It is widely accepted that massive volcanism causes environmental change, often including rapid and significant global warming and marine anoxia, which may trigger mass extinctions. However, the exact nature of the climate altering gases (CO2, SO2, CH4, halogens), as well as their source (degassing of magma, metamorphosed crustal sediments, recycled crustal material in the mantle) remain unclear. These questions could be addressed by determining the relative duration and timing of flood basalt volcanism and environmental and biological change. However, these processes act over timescales of <10^6 years, and possibly 10^4-10^5 years (comparable to current rates of anthropogenic greenhouse gas release), and thus outside the temporal resolution of radiometric dating techniques. We will develop new trace element proxies for volcanism in sediments, allowing us to determine the relative timing of volcanism, climate warming and extinction from analysis of sedimentary sections. Volatile trace elements present at high concentrations in volcanic gases, as determined by direct measurements of volcanic gas and volcanic sublimates at active volcanoes, include Hg, Tl, In, Pb, Bi, Cd, Te, Se, Sn, Cs, Sb and As. During volcanism, these elements are released into the atmosphere and later incorporated into sediments. Their relative concentration in sediments then represents a proxy for the intensity of volcanic activity. To date, only Hg has been explored as a proxy for volcanism, but concentrations of Hg are also affected by the organic content of sediments, and other elements have not been studied in detail before. We will measure volatile volcanogenic trace elements in sediments spanning the Changhsingian-Induan (Permo-Triassic) and Pliensbachian-Toarcian boundaries, in order to link the paleoclimate and fossil records in those sediments with the timing of Siberian and Karoo flood basalt magmatism, potentially at a resolution of better than 10,000 years. These results will reveal the timescales over which flood basalt volcanism affects climate and life, and the origin and nature of gases responsible for environmental change.