Episodic magmatic flare‐ups are documented in many continental arcs worldwide. Yet, the causes of such episodicity and the sources feeding the flare‐ups are not well‐understood. In this study, we use a 1‐D numerical model and scaling analysis to assess the mass balance and thermodynamic feasibility of generating arc magma as a result of partial melting of underthrusted retro‐arc lower crust. Results show the magma volumetric flux or magmatic thickening rate, is directly correlated with the crustal underthrusting rate and the relative timescales of heat transfer and underthrusting. For a continental arc with dimensions similar to the Sierra Nevada arc in California, we show with a constant underthrusting rate of 5 km/Myr, the magmatic thickening rate is 0.1–0.3 km/Myr. This is slightly below the baseline of arc magma thickening rate (∼0.3 km/Myr) from the mantle wedge and accounts for 10%–30% of the magmatic thickening rate during a flare‐up. The cumulative volume of magma generated from the partial melting of a 20‐km‐thick underthrusted lower crust is on the order of 10⁵ km³, about 10%–40% of the estimated magma volume generated during a flare‐up. Therefore, we argue partial melting of underthrusted lower crust plays a partial or subsidiary role in driving a magmatic flare‐up event. Additional melts from the mantle and/or other crustal sources are needed to achieve the observed magmatic output during flare‐ups. The arc root developed by partial melting of the underthrusted crust reduces the time needed to obtain the critical thickness for root foundering, thus influencing the tempo of arc magmatism.

中文翻译：

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俯冲的地壳是否会给大陆弧带来岩浆爆发？

在全球许多大陆弧中都记录了偶发的岩浆爆发。然而，这种流行病的起因和爆发的原因尚未得到很好的理解。在本研究中，我们使用一维数值模型和比例分析来评估由于逆冲下地壳下部地壳部分熔化而产生电弧岩浆的质量平衡和热力学可行性。结果表明，岩浆体积通量或岩浆增厚速率与地壳下冲速率和传热与下冲的相对时间尺度直接相关。对于大陆弧，其尺寸类似于加利福尼亚的内华达山脉弧，我们显示出恒定的下冲速率为5 km / Myr，岩浆增厚速率为0.1–0.3 km / Myr。这略低于弧岩浆增厚速率的基线（〜0。距地幔楔约3 km / Myr），占爆发期间岩浆增厚率的10％–30％。由厚度为20 km的深冲下地壳部分融化产生的岩浆累积量约为10⁵  km ³，大约是爆发过程中产生的估计岩浆量的10％–40％。因此，我们认为下冲的下地壳的部分融化在推动岩浆爆发事件中起着部分或辅助作用。为了在爆发期间获得观测到的岩浆产出，还需要来自地幔和/或其他地壳源的额外熔体。由未完全推进的地壳部分熔化而形成的弧形根部减少了获得用于根部铸造的临界厚度所需的时间，从而影响了弧形岩浆作用的速度。