Abstract Large quartz pebbles erupted with the Escorial ignimbrite provide insight into the late-magmatic evolution of the shallow, cooling magmatic-hydrothermal system below the Cerro Escorial volcano of the Southern Central Volcanic Zone in the Argentine Andes. The ignimbrite is of relatively small volume, crystal-rich, dacitic in composition, and not particularly water-rich, as amphibole is absent. Eruption temperature was estimated to be close to 850 °C. The quartz pebbles provide insight into the magmatic-hydrothermal transition beneath the volcano. Based on textures, trace element composition (analyzed by laser-ablation inductively-coupled plasma mass spectrometry), and inclusion content, the pebbles can be separated into pegmatite-like megacrysts and lower-temperature, epithermal microcrystalline quartz. Both types are distinct from magmatic phenocrysts present in porphyritic clasts ejected by the ignimbrite. The megacrysts show a wide range of trace element concentrations, with elevated Al concentrations and Al/Ti and Ge/Ti ratios compared to quartz phenocrysts. Although some contamination by submicroscopic inclusions and cooling to near-solidus temperatures may perturb the signal in some cases, the range of trace element concentrations in quartz crystals from this system may reflect a change in crystallization conditions from initial precipitation from typical evolved silicate melt to fast growth from residual melt and/or fluid in pegmatitic pockets or coarse-grained hydrothermal “veins” at locally variable precipitation conditions. Abundant primary and secondary silicate melt inclusions and a variety of secondary fluid inclusions are present within the megacrysts. In particular, brine inclusions are densely packed with salt crystals, sometimes anhydrite and/or a silicate crystal, but no visible liquid at room temperature, and co-existing vapor inclusions are of very low density. Heating experiments of brine inclusions reveal last salt and vapor bubble dissolution temperatures around 600–700 °C, but an immiscible silicate melt surrounding the homogenized salt globule remains even at unreasonably high temperature. The co-existence of silicate melt and fluid inclusions reinforces the magmatic nature of the fluids, while boiling trails of brine (with Cu concentrations of several percent) and vapor point to relatively low pressures (

中文翻译：

---

通过喷发的石英和卤水采样，埃斯科里亚尔火山（阿根廷西北部）下从岩浆活动到热液活动的演化

摘要 带有埃斯科里亚火山熔岩喷发的大型石英卵石提供了对阿根廷安第斯山脉南部中央火山带埃斯科里亚火山下方浅层冷却岩浆-热液系统的晚期岩浆演化的深入了解。凝灰岩体积相对较小，富含晶体，成分为英安岩，并且由于没有角闪石而特别富含水。喷发温度估计接近850°C。石英卵石提供了对火山下方岩浆-热液转变的深入了解。根据质地、微量元素组成（通过激光烧蚀电感耦合等离子体质谱法分析）和包裹体含量，鹅卵石可分为伟晶岩类巨晶和低温超热微晶石英。这两种类型都与熔凝灰岩喷出的斑状碎屑中存在的岩浆斑晶不同。巨晶显示出广泛的痕量元素浓度，与石英斑晶相比，Al 浓度和 Al/Ti 和 Ge/Ti 比率升高。尽管在某些情况下，亚微观包裹体造成的污染和冷却至接近固相线的温度可能会干扰信号，但该系统石英晶体中微量元素浓度的范围可能反映了结晶条件的变化，从典型的演化硅酸盐熔体的初始沉淀到快速在局部变化的降水条件下，伟晶岩袋或粗粒热液“脉”中的残余熔体和/或流体生长。巨晶内存在丰富的原生和次生硅酸盐熔体包裹体以及多种次生流体包裹体。特别是卤水包裹体中密布着盐晶体，有时是硬石膏和/或硅酸盐晶体，但在室温下看不到液体，共存的蒸汽包裹体密度非常低。盐水包裹体的加热实验表明，最后的盐和蒸汽泡溶解温度约为 600-700 °C，但即使在不合理的高温下，围绕均质盐球的不混溶硅酸盐熔体仍然存在。硅酸盐熔体和流体包裹体的共存增强了流体的岩浆性质，而卤水（铜浓度为几个百分点）和蒸汽的沸腾轨迹指向相对较低的压力（盐水包裹体密密麻麻地堆积着盐晶体，有时是硬石膏和/或硅酸盐晶体，但在室温下没有可见的液体，并且共存的蒸汽包裹体的密度非常低。盐水包裹体的加热实验表明，最后的盐和蒸汽泡溶解温度约为 600-700 °C，但即使在不合理的高温下，围绕均质盐球的不混溶硅酸盐熔体仍然存在。硅酸盐熔体和流体包裹体的共存增强了流体的岩浆性质，而卤水（铜浓度为几个百分点）和蒸汽的沸腾轨迹指向相对较低的压力（盐水包裹体密密麻麻地堆积着盐晶体，有时是硬石膏和/或硅酸盐晶体，但在室温下没有可见的液体，并且共存的蒸汽包裹体的密度非常低。盐水包裹体的加热实验表明，最后的盐和蒸汽泡溶解温度约为 600-700 °C，但即使在不合理的高温下，围绕均质盐球的不混溶硅酸盐熔体仍然存在。硅酸盐熔体和流体包裹体的共存增强了流体的岩浆性质，而卤水（铜浓度为几个百分点）和蒸汽的沸腾轨迹指向相对较低的压力（盐水包裹体的加热实验表明，最后的盐和蒸汽泡溶解温度约为 600-700 °C，但即使在不合理的高温下，围绕均质盐球的不混溶硅酸盐熔体仍然存在。硅酸盐熔体和流体包裹体的共存增强了流体的岩浆性质，而卤水（铜浓度为几个百分点）和蒸汽的沸腾轨迹指向相对较低的压力（盐水包裹体的加热实验表明，最后的盐和蒸汽泡溶解温度约为 600-700 °C，但即使在不合理的高温下，围绕均质盐球的不混溶硅酸盐熔体仍然存在。硅酸盐熔体和流体包裹体的共存增强了流体的岩浆性质，而卤水（铜浓度为几个百分点）和蒸汽的沸腾轨迹指向相对较低的压力（