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<p>Magma reservoir organization is hidden from view but important to systematic understanding of active volcanoes and intrusive igneous rocks. Seismic anisotropy in active silicic reservoirs suggests horizontally elongated melt sheets or sills, but it remains unclear if shallow silicic reservoirs in low strain rate settings without recent recharge maintain similar organization. Here we present new 3-D seismic tomography of the upper crustal reservoir beneath the tectonically quiescent Valles Caldera using dense nodal arrays. Results reveal &gt;15% radial anisotropy consistent with up to 17-24% melt in horizontally elongated volumes interspersed with melt-poor layers, despite net crystallization since about 0.5 Ma and little contemporary strain. Structural similarity of Valles Caldera to more dynamic modern systems indicates that intrinsic reservoir processes like iterative magma injection, crystal settling, and melt compaction organize long-lived horizontally-layered structure, largely independent of tectonic setting and recharge rate.</p>

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Silicic magma reservoir anisotropy persists through protracted crystallization and low strain rates

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月21日

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  • Wenkai Song,
  • Brandon Schmandt,
  • Justin Wilgus,
  • Fan-Chi Lin,
  • Ross Maguire,
  • Julien Chaput

摘要

Magma reservoir organization is hidden from view but important to systematic understanding of active volcanoes and intrusive igneous rocks. Seismic anisotropy in active silicic reservoirs suggests horizontally elongated melt sheets or sills, but it remains unclear if shallow silicic reservoirs in low strain rate settings without recent recharge maintain similar organization. Here we present new 3-D seismic tomography of the upper crustal reservoir beneath the tectonically quiescent Valles Caldera using dense nodal arrays. Results reveal >15% radial anisotropy consistent with up to 17-24% melt in horizontally elongated volumes interspersed with melt-poor layers, despite net crystallization since about 0.5 Ma and little contemporary strain. Structural similarity of Valles Caldera to more dynamic modern systems indicates that intrinsic reservoir processes like iterative magma injection, crystal settling, and melt compaction organize long-lived horizontally-layered structure, largely independent of tectonic setting and recharge rate.