Abstract Understanding the links between the magma differentiation processes, the magma plumbing system and the magma composition at arc volcanoes is of paramount importance for volcanic hazard assessment. In this work we focus on the post-glacial, Holocene, historical, and recent eruption products of Ubinas volcano (Peru), which display an overall decrease in silica content from the older, plinian (VEI 3–5), rhyolitic eruptions (69–71 wt% SiO2) to the historical and recent (2006–2009, 2013–2017), vulcanian (VEI 1–2) basaltic andesitic eruptions (55–57 wt% SiO2). Based on a comprehensive study of the major and trace elements and the Sr-Nd-Pb isotopes, we conclude that this temporal pattern reflects the evolution of the Ubinas magmas in the middle-to-upper crust by a coupled Assimilation-Fractional Crystallization (AFC) process involving a cumulate composed of plagioclase, amphibole, clinopyroxene, orthopyroxene and Fe Ti oxides, with minor amounts of olivine and biotite at the mafic and felsic end-members, respectively. Upper crustal assimilation is limited to 5–8 vol%, but the overall radiogenic Sr-Nd-Pb signature of the Ubinas magmas requires a larger crustal component, which must therefore occur at middle to lower crustal depths. The petrology of the Ubinas magmas also points to an overall increase in P-T conditions: the large Holocene dacitic and rhyolitic eruptions record temperatures ranging from 800 to 850 °C and pressures in the range of 200–400 MPa, whereas the historical and recent (2006–2009, 2013–2017) basaltic andesitic eruptions provide higher temperatures and pressures (1000 °C, >300–400 MPa). Overall, the thermo-barometry, phase equilibrium and geochemical constraints allow us to propose the existence of a middle-to-upper crust magma column composed of a highly crystalline magma mush containing batches of liquid magma, which seems to be continually recharged from deeper levels. On the basis of the petrological nature of the historical basaltic andesitic eruptions (1667 CE, 2006–2009, 2013–2017), we postulate that during the last centuries, Ubinas experienced a recharge-dominated process, with no evidence for a rejuvenation of the silica-rich reservoir that fed the large Holocene dacitic to rhyolitic eruptions. This study highlights the importance of detailed petrological studies of Holocene sequences at explosive arc volcanoes in order to constrain the magmatic processes and conditions that control large explosive eruptions.

中文翻译：

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将冰后时期的岩浆过程和岩浆化学与乌比纳斯火山（秘鲁南部）最近的爆发性喷发联系起来

摘要 了解弧形火山岩浆分异过程、岩浆管道系统和岩浆成分之间的联系对于火山灾害评估至关重要。在这项工作中，我们关注 Ubinas 火山（秘鲁）的后冰河期、全新世、历史和近期喷发产物，这些产物显示出较旧的普林期 (VEI 3-5) 流纹岩喷发 (69 –71 wt% SiO2) 到历史和近期 (2006–2009, 2013–2017) 火山 (VEI 1–2) 玄武质安山岩喷发 (55–57 wt% SiO2)。基于对主要和微量元素以及 Sr-Nd-Pb 同位素的综合研究，我们得出的结论是，这种时间模式反映了中上地壳 Ubinas 岩浆的演化过程，该过程涉及由斜长石、角闪石、斜辉石、斜方辉石和 Fe Ti 氧化物组成的累积物，其中包括同化-分数结晶 (AFC) 过程。分别在镁铁质和长英质端元中含有少量橄榄石和黑云母。上地壳同化仅限于 5-8 vol%，但 Ubinas 岩浆的整体放射成因 Sr-Nd-Pb 特征需要更大的地壳成分，因此必须发生在中到下地壳深度。Ubinas 岩浆的岩石学也表明 PT 条件的整体增加：全新世英安岩和流纹岩大喷发记录的温度范围为 800 至 850 °C，压力范围为 200-400 MPa，而历史和近期（2006-2009、2013-2017）玄武质安山岩喷发提供了更高的温度和压力（1000°C，>300-400 MPa）。总体而言，热气压测量、相平衡和地球化学约束使我们能够提出中上地壳岩浆柱的存在，该岩浆柱由高度结晶的岩浆糊组成，其中含有一批批液态岩浆，似乎不断从更深层次补充. 根据历史上玄武质安山岩喷发（公元 1667 年、2006-2009 年、2013-2017 年）的岩石学性质，我们假设在过去的几个世纪中，乌比纳斯经历了一个以补给为主的过程，没有证据表明富含二氧化硅的储层，为大型全新世英安岩提供了流纹岩喷发。