Abstract Arclogites are eclogite-like rocks formed magmatically as ultramafic residues and cumulates in the roots of thick arcs ( Ducea et al., 2020a , Ducea et al., 2020b companion paper). They are inferred to be volumetrically important assemblages to complement subduction-related magmatic rocks at depth, in areas where the upper plate crust is thick. At the surface and in the shallow crust, these arcs form stratovolcanoes found at many sites around the Pacific and batholiths, which are exposed in extinct arcs, such as the western North American Cordillera. Arclogites complement these shallower manifestations of magmatism in subduction zones in that they represent the ultramafic residues left behind following the extraction of intermediate melts. Mass balance calculations constrained by the low silica contents of garnet, amphibole, and iron‑titanium oxides dictate that the silica content of a given arc tracks with the volume of arclogitic residues beneath it. We show that melt extraction takes place in punctuated events of hot-zone evacuation of the lower crust which effectively make up the magmatic flare-ups documented in the mid- to upper-crust. These cyclic events lead to the densification of arclogitic residues and trigger their foundering. We show that in addition to garnet, Fe Ti oxides play an important role in the densification of roots and can trigger foundering even in garnet-free arcs. Recent models show that foundering may be small scale and lateral shearing may have an important role in removing sub arc residues. Consequently, previously postulated large magnitude uplift and large-scale mantle-derived magmatism may not accompany foundering episodes. Partial melting of descending arclogitic bodies is expected to produce small amounts of nepheline (and/or leucite) normative magmas similar in composition to alkaline massifs found in continental interiors, not basaltic or intermediate melts. The foundering rates of arclogites are calculated to be around 20–40 km3/km/Myr in Phanerozoic arcs. The fate of foundered arclogite may include stalling at the 660 km discontinuity, accumulation and mixing with subducted oceanic material at “slab graveyards” along the core-mantle boundary, and/or disaggregation via ductile flow in the mantle. Regardless, there has to be a reservoir in the mantle representing these lower crustal recycled bodies over time. We show that the most likely such reservoir is EM1, one of the well-known and commonly identified recycled material in ocean island basalts, and that 1–3% of the volume of the mantle may be made of this reservoir.

中文翻译：

---

Arclogites 及其在大陆演化中的作用；第 2 部分：与地幔和火山、密度和沉没、重熔和长期储存在地幔中的关系

摘要 弧辉岩是岩浆形成的榴辉岩类岩石，以超镁铁质残渣形式堆积在厚弧根部（Ducea et al., 2020a , Ducea et al., 2020b配套论文）。在上板块地壳较厚的地区，它们被推断为在深度上补充与俯冲相关的岩浆岩的体积上重要的组合。在地表和浅地壳中，这些弧形成了在太平洋和基岩的许多地点发现的层状火山，这些火山暴露在已灭绝的弧中，例如北美西部山脉。Arclogites 补充了俯冲带中这些较浅的岩浆作用表现，因为它们代表了提取中间熔体后留下的超镁铁质残留物。质量平衡计算受石榴石、角闪石、铁钛氧化物决定了给定电弧的二氧化硅含量与其下方的弧长残渣量有关。我们表明，熔体提取发生在下地壳热区疏散的间断事件中，这有效地弥补了中地壳到上地壳中记录的岩浆爆发。这些循环事件导致弧光残基致密化并引发其沉没。我们表明，除了石榴石外，Fe Ti 氧化物在根系致密化方面也起着重要作用，即使在无石榴石的电弧中也能引发沉没。最近的模型表明沉没可能是小规模的，横向剪切可能在去除亚弧残留方面发挥重要作用。因此，先前假设的大规模隆升和大规模地幔衍生的岩浆活动可能不会伴随沉没事件。下降弧长岩体的部分熔融预计会产生少量霞石（和/或白榴石）标准岩浆，其成分类似于大陆内部发现的碱性地块，而不是玄武岩或中间熔体。在显生宙弧中，弧长岩的沉没率经计算约为 20-40 km3/km/Myr。沉没弧光岩的命运可能包括在 660 公里的不连续性处停滞，在沿地核-地幔边界的“板坯墓地”堆积和与俯冲海洋物质混合，和/或通过地幔中的韧性流动分解。无论如何，随着时间的推移，地幔中必须有一个代表这些下地壳循环体的储层。我们表明，最有可能的此类储层是 EM1，它是海岛玄武岩中众所周知且常见的回收材料之一，