Time constraints on igneous processes related to eruption triggering, e.g., magma mixing or ascent in the conduit, are needed in any risk mitigation attempt. In this context, magma ascent rate and kinetics are key parameters as they may correspond to the response time available to civil protection during volcanic unrest. Several tools available to quantify such durations include diffusion chronometry, isotopic geochemistry, and hydrous mineral destabilization related to magma degassing during ascent through the conduit. Here I discuss the possible limitations of the widely used hydrous mineral destabilization chronometry applied to minerals within large lava bodies that cool relatively slowly (over days or weeks) such as thick lava flows and lava domes. Based on the type case of the Sarcoui dome (Chaîne des Puys, France) and its associated phreatomagmatic outbreak deposits, I suggest that hydrous mineral destabilization rims may, in some cases, develop at the surface during dome emplacement. From this perspective, preeruptive timescales calculated based on disequilibrium kinetics will be greatly underestimated, leading to a serious issue in the reconstruction of the eruption dynamics and its possible applications to emergency management for future eruptions. More generally, hydrous mineral destabilization chronometry should be used with great caution. Nevertheless, it remains a choice tool to quantify magma ascent rates for eruptions during which magmas quench upon arrival at the surface (e.g., Plinian, Vulcanian, or phreatomagmatic eruptions), with pumiceous textures being a good indicator of quenching. In the case of lava dome emplacement, I suggest that the minerals embedded in pumiceous clasts emitted during explosive phases are more reliable candidates for chronometry studies than crystals within the dome itself as those clasts might represent the fresh magma that triggered the explosion.

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含水矿物的不稳定边缘可以用来限制熔岩穹顶火山的岩浆上升动力学吗？

任何降低风险的尝试都需要对与喷发触发相关的火成岩过程进行时间限制，例如岩浆混合或管道中的上升。在这种情况下，岩浆上升速率和动力学是关键参数，因为它们可能对应于火山动荡期间民防可用的响应时间。可用于量化此类持续时间的几种工具包括扩​​散计时法、同位素地球化学以及与通过管道上升期间岩浆脱气相关的含水矿物不稳定。在这里，我讨论了广泛使用的含水矿物失稳计时法的可能局限性，该方法适用于冷却相对缓慢（数天或数周）的大型熔岩体内的矿物，例如厚熔岩流和熔岩穹顶。基于 Sarcoui 圆顶 (Chaîne des Puys, France) 及其相关的岩浆爆发沉积物，我认为在某些情况下，含水矿物不稳定边缘可能会在圆顶就位期间在地表形成。从这个角度来看，基于不平衡动力学计算的喷发前时间尺度将被大大低估，导致喷发动力学重建及其在未来喷发应急管理中的可能应用方面存在严重问题。更一般地说，应非常谨慎地使用含水矿物失稳计时法。尽管如此，它仍然是量化喷发的岩浆上升速率的一种选择工具，在这些喷发期间，岩浆在到达地表时骤冷（例如，普林期、火神期或岩浆喷发），其中浮石质地是一个很好的淬火指标。在熔岩穹顶安置的情况下，