Abstract The eruptive products of continental arc volcanoes provide wide-ranging insights into the processes governing storage, differentiation, and final eruption (or emplacement) of magmas from trans-crustal magmatic systems. The important role and fractionation of amphibole in continental arc magmatic systems is well documented even if amphibole is generally absent as a prevalent phenocrystic phase in erupted, differentiated lavas. This study presents a comprehensive textural and geochemical investigation of rare plagioclase-bearing hornblendite cumulates entrained in c. 1.4 Ma (trachy-)andesites at the Quillacas monogenetic center on the Bolivian Altiplano, Central Andes. MicroXRF mapping and imaging via SEM-EDS clearly reveals their mesocumulate, idiomorphic nature characterized by cumulus hornblende (≥90%) with intercumulus sodic plagioclase (~8%), minor Fe-Ti oxides and accessory apatites. The trace element compositions of cumulus amphiboles are consistent with their crystallization from a silicate melt with (La/Yb)N

中文翻译：

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玻利维亚角闪石堆积：深入了解中安第斯弧岩浆系统

摘要 大陆弧火山的喷发产物为研究跨地壳岩浆系统岩浆的储存、分异和最终喷发（或侵位）过程提供了广泛的见解。角闪石在大陆弧岩浆系统中的重要作用和分馏得到了很好的记录，即使角闪石作为喷发的分化熔岩中普遍存在的斑晶相通常不存在。本研究对 c 中夹带的稀有含斜长石的角闪石堆积体进行了全面的结构和地球化学调查。1.4 Ma (trachy-)安山岩位于玻利维亚高原、安第斯山脉中部的 Quillacas 单发生中心。通过 SEM-EDS 进行的 MicroXRF 映射和成像清楚地揭示了它们的中间累积、以角闪石积云 (≥90%) 和积云间钠斜长石 (~8%)、少量 Fe-Ti 氧化物和辅助磷灰石为特征的自形性质。积云闪石的微量元素组成与其从含 (La/Yb)N 的硅酸盐熔体结晶一致