Abstract The ascent and extrusion of crystal-rich magma is commonly facilitated by deformation partitioned within annular, conduit-parallel shear zones. The physical properties and textures of the shear zone materials, where exposed at surface, provide a record of ascent and eruption dynamics. We describe the shear zone developed in Dome C, part of Chaos Crags in the Lassen Volcanic Center (California, USA). The extruded shear zone comprises volcanic fault gouge and variably densified cataclasites. The competent cataclasites evidence deep-seated gouge production followed by gouge densification within the conduit on the timescale of lava dome ascent. Textural, geochemical and mineralogical data identify solid-state sintering as the densification mechanism. At the temperatures and pressures in the volcanic conduit, solid-state sintering causes rapid porosity and permeability loss within the gouge and concomitant material strengthening. Longer dwell times (i.e., slower ascent) allow for more sintering, producing stronger, denser and less permeable cataclasites. At Chaos Crags, we use the extent of sintering, quantified by residual porosity, to recover minimum in-conduit dwell times necessary to produce the observed cataclasites. Our analysis of the Dome C cataclasites suggests a maximum linear ascent rate of 10 m/day and a minimum ascent time of 100 days. We evaluate the consequences of shear zone lithification by solid-state sintering for the eruption of other crystal-rich, glass-poor magmas. Chaos Crags cataclasites preserve evidence of multiple cycles of fracturing, cataclasis and (re-)sintering suggesting a mechanism for transitions between effusive and explosive phases of dome-building eruptions.

中文翻译：

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熔岩穹顶挤压过程中的循环剪切带破裂和烧结：来自拉森火山中心（美国）Chaos Crags 的见解

摘要 富含晶体的岩浆的上升和挤压通常是由环形、平行管道的剪切带内的变形划分的。暴露在表面的剪切带材料的物理特性和纹理提供了上升和喷发动力学的记录。我们描述了在 Dome C 中开发的剪切带，它是 Lassen 火山中心（美国加利福尼亚州）的 Chaos Crags 的一部分。挤压剪切带包括火山断层泥和不同致密化的碎裂岩。合格的碎裂岩证明了深部凿岩产生，随后在熔岩穹顶上升的时间尺度上管道内凿岩致密化。结构、地球化学和矿物学数据表明固态烧结是致密化机制。在火山管道中的温度和压力下，固态烧结会导致凿孔内的孔隙率和渗透率迅速下降，并伴随材料强化。较长的停留时间（即较慢的上升）允许更多的烧结，产生更坚固、更致密且渗透性更低的碎裂石。在 Chaos Crags，我们使用由残余孔隙率量化的烧结程度来恢复生产观察到的碎裂岩所需的最短管道内停留时间。我们对 Dome C 碎裂岩的分析表明，最大线性上升速率为 10 m/天，最短上升时间为 100 天。我们通过固态烧结评估了剪切带岩化对其他富含晶体、缺乏玻璃的岩浆喷发的后果。Chaos Crags 碎裂岩保存了多次压裂循环的证据，