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<p>Silicic calderas exhibit cyclic magmatic progression, with some systems transitioning from homogeneous crystal-rich to subsequent zoned crystal-poor caldera-forming eruptions—yet mechanisms governing this shift remain elusive. Here we contrast two caldera-forming eruptions from the Furongshan caldera complex in Southeast China. Our integrated zircon oxygen-hafnium isotopes, trace elements and bulk-rock data revealing a distinct shift from homogeneous crystal-rich tuffs to compositionally zoned crystal-poor tuffs, accompanied by a decrease in water content and oxygen fugacity. We attribute this temporal shift to a tectonic transition from water-fluxed melting linked to slab dehydration, a hallmark of classical arc magmatism, to adiabatic decompression melting driven by asthenospheric upwelling associated with the progressively rollback subduction of the paleo-Pacific plate. Our findings reveal that large magmatic systems record plate-scale tectonic reorganization via marked shifts in magma water contents and the petrological traits of volcanic deposits.</p>

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Tectonic controls on the transition from homogeneous crystal-rich to zoned crystal-poor ignimbrites

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月22日

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  • Tian-Yu Lu,
  • Zhen-Yu He,
  • Olivier Bachmann,
  • Reiner Klemd,
  • Li-Li Yan,
  • Xi-Sheng Xu

摘要

Silicic calderas exhibit cyclic magmatic progression, with some systems transitioning from homogeneous crystal-rich to subsequent zoned crystal-poor caldera-forming eruptions—yet mechanisms governing this shift remain elusive. Here we contrast two caldera-forming eruptions from the Furongshan caldera complex in Southeast China. Our integrated zircon oxygen-hafnium isotopes, trace elements and bulk-rock data revealing a distinct shift from homogeneous crystal-rich tuffs to compositionally zoned crystal-poor tuffs, accompanied by a decrease in water content and oxygen fugacity. We attribute this temporal shift to a tectonic transition from water-fluxed melting linked to slab dehydration, a hallmark of classical arc magmatism, to adiabatic decompression melting driven by asthenospheric upwelling associated with the progressively rollback subduction of the paleo-Pacific plate. Our findings reveal that large magmatic systems record plate-scale tectonic reorganization via marked shifts in magma water contents and the petrological traits of volcanic deposits.