The formation, storage and chemical differentiation of magma in the Earth’s crust is of fundamental importance in igneous geology and volcanology. Recent data are challenging the high-melt-fraction ‘magma chamber’ paradigm that has underpinned models of crustal magmatism for over a century, suggesting instead that magma is normally stored in low-melt-fraction ‘mush reservoirs’1–9. A mush reservoir comprises a porous and permeable framework of closely packed crystals with melt present in the pore space1,10. However, many common features of crustal magmatism have not yet been explained by either the ‘chamber’ or ‘mush reservoir’ concepts1,11. Here we show that reactive melt flow is a critical, but hitherto neglected, process in crustal mush reservoirs, caused by buoyant melt percolating upwards through, and reacting with, the crystals10. Reactive melt flow in mush reservoirs produces the low-crystallinity, chemically differentiated (silicic) magmas that ascend to form shallower intrusions or erupt to the surface11–13. These magmas can host much older crystals, stored at low and even sub-solidus temperatures, consistent with crystal chemistry data6–9. Changes in local bulk composition caused by reactive melt flow, rather than large increases in temperature, produce the rapid increase in melt fraction that remobilizes these cool- or cold-stored crystals. Reactive flow can also produce bimodality in magma compositions sourced from mid- to lower-crustal reservoirs14,15. Trace-element profiles generated by reactive flow are similar to those observed in a well studied reservoir now exposed at the surface16. We propose that magma storage and differentiation primarily occurs by reactive melt flow in long-lived mush reservoirs, rather than by the commonly invoked process of fractional crystallization in magma chambers14.Magma storage and differentiation in the Earth’s crust mainly occurs by reactive melt flow in long-lived mush reservoirs, rather than by fractional crystallization in magma chambers, as previously thought.

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地壳中岩浆的化学分异、蓄冷和再活化

地壳中岩浆的形成、储存和化学分异在火成岩地质学和火山学中具有重要意义。最近的数据正在挑战一个多世纪以来一直支撑地壳岩浆活动模型的高熔体比例“岩浆房”范式，这表明岩浆通常储存在低熔体比例的“糊状储层”1-9 中。糊状储层包括一个多孔且可渗透的紧密堆积的晶体框架，在孔隙空间 1,10 中存在熔体。然而，地壳岩浆作用的许多共同特征还没有被“腔室”或“糊状储层”概念解释 1,11。在这里，我们表明反应性熔体流动是地壳糊状储层中一个关键但迄今为止被忽视的过程，这是由漂浮的熔体向上渗透并与晶体反应引起的。糊状储层中的反应性熔体流动产生低结晶度、化学分化（硅质）岩浆，这些岩浆上升形成较浅的侵入体或喷发到地表 11-13。这些岩浆可以容纳更古老的晶体，储存在低温甚至亚固相线温度下，与晶体化学数据一致 6-9。由反应性熔体流动引起的局部整体组成的变化，而不是温度的大幅升高，会导致熔体分数的快速增加，从而使这些冷却或冷藏的晶体重新流动。反应流还可以在源自中下地壳储层的岩浆成分中产生双峰性 14, 15。由反应流产生的微量元素剖面类似于在现在暴露在地表的经过充分研究的储层中观察到的那些。