Abstract Processes of crystal-mush remobilization by mafic magma recharges are often related to the outpouring of large volumes of silicic melt during caldera-forming eruptions. This occurred for the Campanian Ignimbrite (CI) eruption (Campi Flegrei, Italy), which produced a voluminous trachy-phonolitic ignimbrite in southern-central Italy about 40 ka ago. We focussed on the proximal-CI deposits at San Martino that are composed of a main sequence of early-erupted, crystal-poor units and a late-erupted (post-caldera collapse) crystal-rich Upper Pumice Flow Unit (UPFU). Detailed micro-analytical geochemical data were performed on glasses and crystals of pyroclasts from these deposits and coupled with Sr-Nd isotopic measurements on glasses. Results show that the CI eruption was fed by two distinct melts for the early-erupted units and the late UPFU, respectively. The glasses of the early-erupted units have negative Eu anomalies and show more evolved compositions and higher Nd isotope ratios than those of the UPFU, which have positive Eu/Eu*. The magmas of the early units formed the main volume of eruptible melt of the CI reservoir, and are interpreted as having been extracted from cumulate crystal-mush without a vertical geochemical gradient within the magma reservoir. The data indicate that the generation of the distinctive UPFU melts involved the injection of a new batch of mafic magma into the base of the CI reservoir. The mafic magma allowed heating and reactivation of the CI crystal-mush by melting of low-Or sanidines (+/− low-An plagioclases), leaving high-An plagioclases and high-Mg# clinopyroxenes as residual phases and a crystal-mush melt, made of 20% of the initial mush interstitial melt (with a composition similar to the early-erupted units) and 80% of sanidine melt. When the mush crystallinity was sufficiently reduced, the mafic magma was able to penetrate into the reactivated crystal-mush, mixing with variable proportions of crystal-mush melt and generating cooler hybrid melts, which underwent further crystallization of high-Or sanidine at variable degrees (10–25%). Finally, possibly a short time before the eruption, the UPFU magmas were able to mix and mingle with the crystal-poor eruptible melts still persisting in the CI reservoir at the time of UPFU emission. We suggest that the complex mechanisms described for the magma evolution feeding the CI eruption may occur whenever a crystal-mush is reactivated by new mafic magma inputs

中文翻译：

---

岩浆补给引起的晶体糊状物重新激活：来自意大利坎皮弗莱格雷火山场的坎帕尼亚 Ignimbrite 活动的证据

摘要 镁铁质岩浆补给引起的结晶糊再活化过程通常与火山口形成喷发期间大量硅质熔体的喷出有关。这发生在坎帕尼亚 Ignimbrite (CI) 喷发 (Campi Flegrei，意大利) 中，大约 40 ka 前，该喷发在意大利中南部产生了大量粗长音质 ignimbrite。我们专注于圣马蒂诺的近端 CI 沉积物，它们由早期喷发、缺乏晶体的单元和晚期喷发（火山口坍塌后）富含晶体的上浮石流单元 (UPFU) 组成。对来自这些沉积物的玻璃和火山碎屑晶体进行了详细的微观分析地球化学数据，并结合了对玻璃的 Sr-Nd 同位素测量。结果表明，对于早期喷发单元和晚期 UPFU，CI 喷​​发由两种不同的熔体供给，分别。与具有正 Eu/Eu* 的 UPFU 相比，早期喷发单元的玻璃具有负的 Eu 异常，并显示出更多的演化成分和更高的 Nd 同位素比。早期单元的岩浆形成了CI储层可喷发熔体的主要体积，被解释为是从岩浆储层内没有垂直地球化学梯度的累积结晶糊中提取的。数据表明，独特的 UPFU 熔体的产生涉及将新一批基性岩浆注入 CI 储层底部。镁铁质岩浆允许通过熔化低-Or sanidines（+/- 低-An 斜长石）加热和重新激活 CI 结晶糊状物，留下高-An 斜长石和高 Mg# 单斜辉石作为残余相和结晶糊状物熔体, 由 20% 的初始糊状间隙熔体（成分与早期喷发单元相似）和 80% 的山尼丁熔体组成。当糊状物结晶度充分降低时，镁铁质岩浆能够渗透到重新活化的结晶糊状物中，与不同比例的结晶糊状物熔体混合并产生较冷的混合熔体，这些熔体在不同程度上进一步结晶高-Or sanidine。 10–25%）。最后，可能在喷发前不久，UPFU 岩浆能够与在 UPFU 喷发时仍然存在于 CI 储层中的晶体贫乏的可喷发熔体混合和混合。我们认为，每当晶体糊被新的基性岩浆输入重新激活时，就可能发生为 CI 喷发提供的岩浆演化所描述的复杂机制。