13:45 〜 14:00
[SGC37-01] Tracing crust-mantle interactions along the Yellowstone Hotspot Track
★Invited Papers
キーワード：Mantle , Noble Gas, Crust
The Yellowstone Caldera formed approximately 640,000 years ago, when the Yellowstone Volcano catastrophically erupted >1000 km3 of rhyolitic magma to the surface. A trail of progressively younger north-eastward trending volcanic centres that culminates at the current Yellowstone Caldera however, suggests that the Yellowstone Volcano erupted several times throughout geological history. This trail of volcanic centres, otherwise known as the Yellowstone Hotspot Track, formed as the North American plate moved across the stationary Yellowstone mantle plume. Volcanic gas emanating at the present-day caldera exhibits 3He/4He ratios up to 16 RA (where 1 RA = 3He/4He of air = 1.39 x 10-6), which is consistent with the Yellowstone Volcano being fed by a deep undegassed mantle reservoir [1]. However, the 3He/4He ratios within the caldera have also been shown to be highly variable, with 3He/4He ratios as low as 2 RA [1,2]. The low 3He/4He values in the Yellowstone Caldera are thought to originate from the incorporation of crustal volatiles from the overlying Archean crust into magmatic material rising from the Yellowstone mantle source [2]. Since, cratonic crust and lithosphere can be a significant long-term repository for volatiles, the remobilisation and release of these volatiles at the surface, during periods of magmatic upwelling, could potentially have an impact on the global environment [3], whilst potentially also creating new sources of economically important volatiles, such as helium [4].
Despite the lack of an active magmatic system beneath the Yellowstone Hotspot Track, there are multiple active hydrothermal degassing sites dotted along the track. The Yellowstone Hotspot Track therefore represents an ideal location to investigate crust-mantle interactions, as these hydrothermal sites provide a unique opportunity to investigate how the volatiles sources evolves as distance from the hot Yellowstone Plume increases. In this study, we will present a comprehensive overview of the major gas chemistry and noble gas isotope composition of gases collected from several hydrothermal degassing sites dotted along the Yellowstone Hotspot Track. Using a combination of traditional static noble gas mass spectrometry and a recently developed technique for the analysis of heavy noble gas isotopes using dynamic mass spectrometry [5], we are now able to identify the different crustal and mantle signals present in these gases better than ever before, whilst also providing new insights into the physical processes occurring in the subsurface as mantle and crustal volatiles migrate towards the surface.
[1] Broadley et al., 2020. PNAS, 117(25), pp.13997-14004. [2] Lowenstern et al., 2014. Nature, 506(7488), pp.355-358. [3] Broadley et al., 2018. Nature Geoscience, 11(9), pp.682-687. [4] Danabalan et al., (2022) Petroleum Geoscience, 28(2), pp.petgeo2021-029. [5] Seltzer and Bekaert, 2022. International Journal of Mass Spectrometry, 478, p.116873.
Despite the lack of an active magmatic system beneath the Yellowstone Hotspot Track, there are multiple active hydrothermal degassing sites dotted along the track. The Yellowstone Hotspot Track therefore represents an ideal location to investigate crust-mantle interactions, as these hydrothermal sites provide a unique opportunity to investigate how the volatiles sources evolves as distance from the hot Yellowstone Plume increases. In this study, we will present a comprehensive overview of the major gas chemistry and noble gas isotope composition of gases collected from several hydrothermal degassing sites dotted along the Yellowstone Hotspot Track. Using a combination of traditional static noble gas mass spectrometry and a recently developed technique for the analysis of heavy noble gas isotopes using dynamic mass spectrometry [5], we are now able to identify the different crustal and mantle signals present in these gases better than ever before, whilst also providing new insights into the physical processes occurring in the subsurface as mantle and crustal volatiles migrate towards the surface.
[1] Broadley et al., 2020. PNAS, 117(25), pp.13997-14004. [2] Lowenstern et al., 2014. Nature, 506(7488), pp.355-358. [3] Broadley et al., 2018. Nature Geoscience, 11(9), pp.682-687. [4] Danabalan et al., (2022) Petroleum Geoscience, 28(2), pp.petgeo2021-029. [5] Seltzer and Bekaert, 2022. International Journal of Mass Spectrometry, 478, p.116873.