Mayon is a basaltic andesitic, open-vent volcano characterized by persistent passive degassing from the summit at 2463 m above sea level. Mid-size (< 0.1 km³) and mildly explosive eruptions and occasional phreatic eruptions have occurred approximately every 10 years for over a hundred years. Mayon’s plumbing system structure, processes, and time scales driving its eruptions are still not well-known, despite being the most active volcano in the Philippines. We investigated the petrology and geochemistry of its crystal-rich lavas (~ 50 vol% phenocrysts) from nine historical eruptions between 1928 and 2009 and propose a conceptual model of the processes and magmatic architecture that led to the eruptions. The whole-rock geochemistry and mineral assemblage (plagioclase + orthopyroxene + clinopyroxene + Fe-Ti oxide ± olivine) of the lavas have remained remarkably homogenous (54 wt% SiO₂, ~ 4 wt% MgO) from 1928 to 2009. However, electron microscope images and microprobe analyses of the phenocrysts and the existence of three types of glomerocrysts testify to a range of magmatic processes, including long-term magma residence, magma mixing, crystallization, volatile fluxing, and degassing. Multiple mineral-melt geothermobarometers suggest a relatively thermally buffered system at 1050 ± 25 °C, with several magma residence zones, ranging from close to the surface, through reservoirs at ~ 4–5 km, and as deep as ~ 20 km. Diffusion chronometry on > 200 orthopyroxene crystals reveal magma mixing timescales that range from a few days to about 65 years, but the majority are shorter than the decadal inter-eruptive repose period. This implies that magma intrusion at Mayon has been nearly continuous over the studied time period, with limited crystal recycling from one eruption to the next. The variety of plagioclase textures and zoning patterns reflect fluxing of volatiles from depth to shallower melts through which they eventually reach the atmosphere through an open conduit. The crystal-rich nature of the erupted magmas may have developed during each inter-eruptive period. We propose that Mayon has behaved over almost 100 years as a steady state system, with limited variations in eruption frequency, degassing flux, magma composition, and crystal content that are mainly determined by the amount and composition of deep magma and volatile input in the system. We explore how Mayon volcano’s processes and working model can be related to other open-vent mafic and water-rich systems such as Etna, Stromboli, Villarrica, or Llaima. Finally, our understanding of open-vent, persistently active volcanoes is rooted in historical observations, but volcano behavior can evolve over longer time frames. We speculate that these volcanoes produce specific plagioclase textures that can be used to identify similar volcanic behavior in the geologic record.

马荣火山是一座玄武质安山质开放式火山，其特征是从海拔 2463 m 的山顶持续被动脱气。中型（< 0.1 km ³) 并且在一百多年的时间里，大约每 10 年发生一次轻度爆炸性喷发和偶尔的潜水喷发。尽管马荣火山是菲律宾最活跃的火山，但它的管道系统结构、过程和推动其喷发的时间尺度仍然不为人所知。我们研究了 1928 年至 2009 年间九次历史喷发的富含晶体的熔岩（约 50 vol% 斑晶）的岩石学和地球化学，并提出了导致喷发的过程和岩浆结构的概念模型。熔岩的全岩地球化学和矿物组合（斜长石 + 斜辉石 + 单斜辉石 + Fe-Ti 氧化物 ± 橄榄石）保持非常均匀（54 wt% SiO ₂, ~ 4 wt% MgO) 从 1928 年到 2009 年。 然而，斑晶的电子显微镜图像和显微探针分析以及三种类型球晶的存在证明了一系列岩浆过程，包括岩浆长期滞留、岩浆混合、结晶、挥发性助熔剂和脱气。多个矿物熔体地温气压计表明在 1050 ± 25 °C 有一个相对热缓冲系统，有几个岩浆滞留区，范围从接近地表，穿过约 4-5 公里的储层，深达约 20 公里。对 > 200 个斜方辉石晶体的扩散计时显示，岩浆混合时间尺度从几天到大约 65 年不等，但大多数都比十年间的喷发间休期短。这意味着在研究的时间段内，马荣的岩浆侵入几乎是连续的，从一次喷发到下一次喷发的晶体回收有限。斜长石纹理和分区模式的多样性反映了挥发物从深处到浅层熔体的流动，最终通过开放的管道到达大气。喷发岩浆的富含晶体的性质可能在每次喷发间期形成。我们认为，马荣已经作为一个稳态系统运行了近 100 年，喷发频率、脱气通量、岩浆成分和晶体含量的变化有限，这主要取决于系统中深部岩浆和挥发物输入的数量和成分. 我们探讨了马荣火山的过程和工作模型如何与其他开放式基性和富水系统（如埃特纳火山、斯特龙博利、比亚里卡或拉马）相关联。最后，我们对open-vent的理解，持续活跃的火山植根于历史观察，但火山行为可以在更长的时间范围内演变。我们推测这些火山会产生特定的斜长石纹理，可用于在地质记录中识别类似的火山行为。