Sedimentary diapirs can be relaminated to the base of the lithosphere during slab subduction, where they can interact with the ambient lithospheric mantle to form variably metasomatized zones. Here, high-pressure experiments in sediment-harzburgite systems were conducted at 1.5–2.5 GPa and 800–1300 °C to investigate the interaction between relaminated sediment diapirs and lithospheric mantle. Two end-member processes of mixed experiments and layered (reaction) experiments were explored. In the first end-member, sediment and harzburgite powders were mixed to a homogeneous proportion (1:3), whereas in the second, the two powders were juxtaposed as separate layers. In the first series of experiments, the run products were mainly composed of olivine + orthopyroxene + clinopyroxene + phlogopite in subsolidus experiments, while the phase assemblages were then replaced by olivine + orthopyroxene + melt (or trace phlogopite) in supersolidus experiments. Basaltic and foiditic melts were observed in all supersolidus mixed experiments (~44–52 wt% SiO2 at 1.5 GPa, ~35–43 wt% SiO2 at 2.5 GPa). In the phlogopite-rich experiment (PC431, 1.5 GPa and 1100 °C), the formed melts had low alkali contents (~<2 wt%) and K2O/Na2O ratios (~0.4–1.1). In contrast, the quenched melt in phlogopite-free/poor experiments showed relatively higher alkali contents (~4–8 wt%) and K2O/Na2O ratios (~2–5). Therefore, the stability of phlogopite could control the bulk K2O and K2O/Na2O ratios of magmas derived from the sediment-metasomatized lithospheric mantle. In layered experiments, a reaction zone dominated by clinopyroxene + amphibole (or orthopyroxene) was formed because of the reaction between harzburgite and bottom sediment-derived melts (~62.5–67 wt% SiO2). The total alkali contents and K2O/Na2O ratios of the formed melts were about 6–8 wt% and 1.5–3, respectively. Experimentally formed melts from both mixed and reaction experiments were rich in large ion lithosphile elements and displayed similar patterns with natural potassium-rich arc lavas from oceanic subduction zones (i.e., Mexican, Sunda, Central American, and Aleutian). The experimental results demonstrated that bulk sediment diapirs, in addition to sediment melt, may be another possible mechanism to transfer material from a subducting slab to an upper mantle wedge or lithospheric mantle. On the other hand, the breakdown of phlogopite may play an important role in the mantle source that produces potassiumrich arc lavas in subduction zones.

中文翻译：

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俯冲带沉积物交代岩石圈地幔部分熔融的实验约束

沉积底辟可以在板块俯冲过程中重新堆积到岩石圈底部，在那里它们可以与周围的岩石圈地幔相互作用，形成不同程度的交代带。在这里，在 1.5-2.5 GPa 和 800-1300 °C 的条件下，在沉积物-菱镁矿系统中进行了高压实验，以研究分层沉积物底辟与岩石圈地幔之间的相互作用。探索了混合实验和分层（反应）实验的两个端元过程。在第一个端元中，沉积物和菱镁矿粉末以均匀的比例 (1:3) 混合，而在第二个端元中，两种粉末并置为单独的层。在第一系列实验中，亚固相实验中运行产物主要由橄榄石+斜辉石+斜辉石+金云母组成，而在超固相线实验中，相组合随后被橄榄石 + 斜方辉石 + 熔体（或微量金云母）取代。在所有超固体混合实验中都观察到玄武岩和镁质熔体（1.5 GPa 下约 44–52 wt% SiO2，2.5 GPa 下约 35–43 wt% SiO2）。在富含金云母的实验中（PC431，1.5 GPa 和 1100 °C），形成的熔体具有低碱含量（~<2 wt%）和 K2O/Na2O 比率（~0.4-1.1）。相比之下，在无金云母/贫矿实验中淬火的熔体显示出相对较高的碱含量（~4-8 wt%）和 K2O/Na2O 比（~2-5）。因此，金云母的稳定性可以控制沉积物交代岩石圈地幔岩浆的体积 K2O 和 K2O/Na2O 比。在分层实验中，由于方辉石和底部沉积物衍生熔体（~62.5-67 wt% SiO2）之间的反应，形成了以斜辉石+角闪石（或斜方辉石）为主的反应区。形成的熔体的总碱含量和 K2O/Na2O 比率分别约为 6-8 wt% 和 1.5-3。从混合和反应实验中实验形成的熔体富含大离子亲岩元素，并显示出与来自大洋俯冲带（即墨西哥、巽他、中美洲和阿留申）的天然富钾弧形熔岩相似的模式。实验结果表明，除了沉积物熔化外，大量沉积物底辟可能是将物质从俯冲板片转移到上地幔楔或岩石圈地幔的另一种可能机制。另一方面，