Abstract The observational and semi-quantitative sedimentological analyses of the lithofacies assemblage contribute to describe at different scales the breccia matrix along the sheared and transformed contact between rock avalanche deposits and trailing debris flow deposits emplaced by a large landslide at Mt. Meager volcano in British Columbia in 2010. An inverted cataclastic gradient of crushed breccias in a fluidized and mixed matrix implies a structurally controlled flow regime and rapid deposition. The coating matrix changed the initial polymodal distribution of the debris-flow lithofacies. Clast shape evolution helps to characterize the cataclastic sorting during transport and fluidized disaggregation. A plot of matrix percent against matrix/gravels helps to distinguish primary hot fracturing of about 61% from initial dilation and sheared fracturing involving ~22% matrix. Extensional disaggregation between 73 and 79% matrix is related to hydromagmatic fragmentation within an epithermal system. Clayey mineral assemblages identified by XRD patterns are related to colloidal aluminium gel, cataclastic shear bands, and quartz microstructures in epithermal breccia zones (pH = 2–3, 200–350 °C, Microstructural analysis differentiates the inner rim of coated clasts from their border and the surrounding matrix in impact melt breccias. Sequential coating stages are inferred during the propagation of the shock wave with an oscillatory relative speed during the inter-seismic period. We differentiate: 1) shock faulting which contributes to the impacted quartz (10–35 GPa) in a devitrified matrix and pseudotachylite coating related to frictional melting at the margin of a conduit; 2) shock response (85 GPa) in epithermal vein with calcic spheroids, CO2 dissociation, and basaltic melt (70–101 GPa, >1500 °C); and 3) the secondary fracturing with flash heating and pressure pulse during cavitation (ΔP ~ 10 GPa, >1000–1500 °C), which generates pockets of partial melting, quartz spheroids, and a roll-over effect for the inner rim of coated clasts. The formation of impact melt breccias and the debris flow are related to the slowing elastic impact wave with an oscillatory relative speed during the inter-seismic period along a proximal strike-slip fault. This study helps identify how the proximal rock avalanche transformed into a highly mobile debris flow, larger examples of which pose a hazard to the town of Pemberton, at a distance of 65 km from Mt. Meager.

中文翻译：

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来自不列颠哥伦比亚省（加拿大）米格尔山火山群的岩崩碎屑流沉积物内的超热碎屑涂层

摘要 岩相组合的观测和半定量沉积学分析有助于在不同尺度上描述沿着岩石雪崩沉积物和尾随泥石流沉积物之间的剪切和转化接触的角砾岩基质。2010 年不列颠哥伦比亚省的贫瘠火山。流化和混合基质中破碎角砾岩的倒塌碎裂梯度意味着结构可控的流动状态和快速沉积。涂层基质改变了碎屑流岩相的初始多峰分布。碎屑形状演化有助于表征运输和流化分解过程中的碎裂分选。基质百分比与基质/砾石的关系图有助于区分约 61% 的初始热压裂与初始膨胀和剪切压裂，其中包含约 22% 的基质。73% 和 79% 基质之间的伸展解聚与超热液系统内的水岩浆破碎有关。通过 XRD 模式识别的粘土矿物组合与超热液角砾岩带中的胶体铝凝胶、碎裂剪切带和石英微结构有关（pH = 2-3，200-350 °C，微观结构分析将包覆碎屑的内缘与其边界区分开来以及冲击熔体角砾岩中的周围基质。在震间期期间，在具有振荡相对速度的冲击波传播期间推断出连续的涂层阶段。我们区分：1) 冲击断层导致失透基质中的冲击石英 (10-35 GPa) 和与导管边缘摩擦熔化相关的伪速晶石涂层；2) 具有钙质球体、CO2 解离和玄武岩熔体 (70–101 GPa, >1500 °C) 的超热液脉中的冲击响应 (85 GPa)；3) 空化过程中的闪加热和压力脉冲二次压裂 (ΔP ~ 10 GPa, >1000–1500 °C), 产生部分熔化的囊袋、石英球体和涂层内缘的翻滚效应碎屑。冲击熔体角砾岩和碎屑流的形成与沿近端走滑断层的地震间期具有振荡相对速度的缓慢弹性冲击波有关。这项研究有助于确定近端岩石雪崩如何转变为高度流动的泥石流，其中较大的例子对距离 Mt. 65 公里的彭伯顿镇构成危险。微薄。