Rhyolitic volcanism can provide important information about the mechanisms by which highly-evolved crystal-poor melts can be extracted from silicic crystal-mush reservoirs. In the Altiplano-Puna plateau (Central Andes), rhyolites are volumetrically less abundant than the high-volume, crystal-rich intermediate products emitted during the ignimbritic flare-up (ca. 10–1 Ma), and their geological and temporal relation with the widespread, upper crustal, dacitic mush systems is not well constrained. We studied the isotopic (UPb ages), trace (U, Th, Hf, Y, Ti, P) and rare earth element compositions of zircon contained in the rhyolitic products of the Ramadas Volcanic Centre (late Miocene), which erupted extremely-aphyric, garnet-bearing tubular pumice during a single Plinian event (Corte Blanco Tuff; northern Puna plateau). Results reveal a complex pre-eruptive magmatic history characterized by variable crystallization conditions existing at different times within an upper-crustal crystal-mush reservoir. The unmixing model applied to magmatic zircon sharing textural and geochemical features (oscillatory texture, Th/U = 0.2–0.6; Eu/Eu* = 0.1–0.7) indicates the existence of at least two mush-related crystallization events, which are separated by a protracted hiatus (ca. 2 Ma), and are supported by independent isotopic ages. An episode of zircon crystallization (average disequilibrium-corrected ²⁰⁶Pb/²³⁸U age of 9.06 ± 0.19 Ma) coincides with the ages determined for accessory phases associated with garnet in pumice samples (9.163 ± 0.037 Ma, UPb age determination on zircon; 8.70 ± 0.23 Ma, U-Th-Pb age determination on monazite). A further zircon crystallization event is recorded at ca. 6.64 ± 0.12 Ma, which is concordant with published radiometric ages dating the eruption at 6.3 ± 0.3 Ma (average ⁴⁰Ar/³⁹Ar age of glass shards from distal locations) and at 6.63 ± 0.28 Ma (fission track age of proximal obsidian). The existence of a late-stage to hydrothermal crystallization event is evident from another zircon population with low Th/U ratios (< 0.1) and a ²⁰⁶Pb/²³⁸U age of 6.514 ± 0.058 Ma, which crystallized in cold and highly-evolved parts of the reservoir resulting in negative Eu/Eu* and Ti depletion in zircon before these crystals were recycled into the erupting magma. The extreme aphyric character of the rhyolitic products and the nearly-complete lack of phenocrysts and glomerocrysts despite their evolved composition indicate that the Plinian eruption was preceded by effective extraction of crystal-poor melts from the mush zone, during which only micrometric antecrystic minerals (≤ 200 μm) were incorporated. Gas filter-pressing, combined with a compressional local stress field, likely contributed to melt-crystal separation, which was favoured by high volatile contents (H₂O^melt 3–5 wt%) and shallow emplacement levels (< 10 km). Finally, the distribution of the U-Pb ages of zircon antecrysts suggests a correlation between the evolution of the Ramadas magmatic system and the fluctuating pattern characterizing the Altiplano-Puna Volcanic Complex flare-up activity, highlighting a possible geological and temporal connection between rhyolitic volcanism and the widespread dacitic mush systems in this sector of the Puna plateau.

流纹岩火山作用可以提供有关机理的重要信息，通过这些机理可以从硅质结晶糊状储层中提取出高度演化的贫结晶熔体。在高原高原-普纳高原（安第斯中部），流纹岩的体积少于火成岩爆发（大约10-1 Ma）期间散发的高含量，富含晶体的中间产物，并且它们的地质和时间关系分布广泛的上地壳洋浆状灌浆系统并没有受到很好的限制。我们研究了同位素（U铅年龄），痕量（U，Th，Hf，Y，Ti，P）和Ramadas火山中心（晚中新世）流纹岩产品中所含的锆石的稀土元素组成，这喷发了非常生的，石榴石状的管状物在一次普林尼事件中浮石（Corte Blanco Tuff；北普纳高原）。结果揭示了一个复杂的喷发前岩浆历史，其特征是在上地壳晶体-浆液储层中在不同时间存在不同的结晶条件。应用于岩浆锆石的具有纹理和地球化学特征（振荡质地，Th / U = 0.2-0.6； Eu / Eu * = 0.1-0.7）的解混模型表明存在至少两个与糊状相关的结晶事件，这些事件由长时间的裂孔（约2 Ma），并受独立同位素年龄的支持。²⁰⁶ Pb / ²³⁸ U的年龄为9.06±0.19 Ma）与浮石样品中与石榴石有关的副相所确定的年龄相吻合（9.163±0.037 Ma，在锆石上确定的U Pb年龄; 8.70±0.23 Ma，U-Th-Pb的年龄测定独居石）。在约200℃下记录了另一锆石结晶事件。6.64±0.12 Ma，与已公布的辐射年龄相一致，即喷发的末期为6.3±0.3 Ma（末梢玻璃碎片的平均年龄为⁴⁰ Ar / ³⁹ Ar）和6.63±0.28 Ma（近端黑曜石的裂变径迹年龄）。从另一个低Th / U比（<0.1）和²⁰⁶ Pb / ^238的锆石种群中可以明显看出，存在一个晚期至水热结晶事件。U年龄为6.514±0.058 Ma，它在储层的寒冷和高度演化的部分中结晶，导致锆石中的Eu / Eu *和Ti消耗为负，然后这些晶体被再循环到喷出的岩浆中。流变产物的极端生水特性，以及尽管演化出的成分几乎没有表晶和肾小球，这表明在普利尼山喷发之前，是从糊状区有效地提取了晶体贫乏的熔体，在此期间只有微米级的前生矿物（≤ 200μm）被并入。气体压滤结合局部压缩应力场，可能有助于熔体晶体分离，这是由高挥发物含量（H ₂ O^熔体）促成的。3-5 wt％）和较浅的位置（<10 km）。最后，锆石前驱体的U-Pb年龄分布表明Ramadas岩浆系统的演化与表征Altiplano-Puna火山复合体爆发活动的波动模式之间的相关性，突显了流纹质火山活动之间可能存在的地质和时间联系以及在Puna高原这一地区广泛的胶泥糊状系统。