The processes that result in arc magmas are critical to understanding element recycling in subduction zones, yet little is known about how these systems evolve with time. Nicaragua provides an opportunity to reconstruct the history of a volcanic arc since the Cretaceous. Here we present the stratigraphy of the Cretaceous–Eocene volcanic units in Nicaragua and their relationship to the different tectonic units where the arc developed. We discovered an evolution from an arc‐dominated by calc‐alkaline compositions in the Cretaceous–Eocene, to transitional compositions in the Oligocene–Miocene, to finally tholeiitic magmas common in the modern volcanic front. Our petrographic studies confirm that in the Cretaceous–Eocene the olivine + clinopyroxene cotectic was followed by clinopyroxene + plagioclase ± amphibole. Given the abundance of amphibole and the lack of this mineral in the modern volcanic front, the Cretaceous–Eocene Arc melts were likely more water‐rich than modern Nicaragua, suppressing the crystallization of plagioclase after olivine. We also found temporal changes in element ratios that are sensitive to variations in sediment input. The Cretaceous–Eocene Arc is characterized by a lower Ba/Th compared to the Oligocene–Miocene and modern volcanic front samples, suggesting that the sediment input was lower in Ba, possibly analogous to old deep siliceous sediment subducting in the western Pacific. Both U/Th and U/La are higher in the modern volcanics, reflecting higher U/Th in the subducting sediments following the 'Carbonate Crash'. Finally, we found that the orientation of the arc axis also changed, from northeast‐southwest in the Cretaceous–Eocene to northwest‐southeast after the Oligocene. This change probably records variations in the location of the subduction zone as this region shaped into its current geographic configuration.

中文翻译：

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100我的尼加拉瓜火山弧演化记录

产生弧形岩浆的过程对于理解俯冲带中元素的循环至关重要，但对于这些系统如何随时间演变知之甚少。尼加拉瓜为重建自白垩纪以来的火山弧历史提供了机会。在这里，我们介绍了尼加拉瓜的白垩纪-始新世火山岩单元的地层及其与弧形成所在的不同构造单元的关系。我们发现了从白垩纪-始新世以钙碱性成分为主的弧向渐新世-中新世的过渡成分演变为现代火山岩前缘普遍的胶质岩浆的演化过程。我们的岩相学研究证实，在白垩纪-始新世，橄榄石+斜辉石共晶，接着是斜辉石+斜长石±闪石。鉴于现代火山爆发前角闪石的丰度和这种矿物的缺乏，白垩纪-始新世弧熔体可能比现代尼加拉瓜更富水，从而抑制了橄榄石后斜长石的结晶。我们还发现元素比的时间变化对沉积物输入的变化敏感。与渐新世-中新世和现代火山锋样品相比，白垩纪-始新世弧的特征是Ba / Th较低，这表明Ba中的泥沙输入量较低，这可能类似于西太平洋中较老的深层硅质泥沙俯冲。在现代火山中，U / Th和U / La都较高，反映出“碳酸盐碰撞”之后俯冲沉积物中的U / Th较高。最后，我们发现弧轴的方向也发生了变化，从白垩纪-始新世的东北-西南到渐新世之后的西北-东南。该变化可能记录了俯冲带位置的变化，因为该区域成形为当前的地理构造。