Abstract—

A radical transformation of the liquidus structure of the MgO–FeO–CaO–SiO₂ system of thermochemical superplumes formed in the Mg–Fe postperovskite-bearing layer D” at the boundary with the Earth’s core during its ascent in the host material of the Mg–Fe bridgmanite-bearing lower mantle to the Mg–Fe ringwoodite-bearing transition zone crossing the 670-km seismic boundary was studied experimentally at 26 and 20 GPa and theoretically. The peritectic reactions of both lower mantle Mg–Fe-bridgmanite with the formation of wüstite and stishovite, and the reactions of Mg–Fe ringwoodite and Mg–Fe akimotoite coupled under the conditions of the transition zone and resulting in the formation of wüstite and stishovite, control the fractional ultramafic–mafic evolution of melts of superplumes in thermobarogradient fields at the corresponding depths of the mantle. The article also discusses the evolutionary physicogeochemical transformations of magmatic systems of superplumes at the depths of the upper mantle and the Earth’s crust with their transformation into “hot fields” with chambers of olivine–basaltic melts transported by “small plumes” into the lithosphere. It is shown that the physicochemical mechanisms and regularities of the ultramafic–mafic evolution of the superplume matter, as well as the Earth’s mantle, are provided by the liquidus structure of the MgO–FeO–CaO–Na₂O–Al₂O₃–SiO₂ system. In this case, the role of the boundary system MgO–FeO–CaO–SiO₂ is important for the conditions of the lower mantle and transition zone,. The fractional crystallization mode promotes an increase in the concentrations of Na₂O and Al₂O₃ in residual melts and their physicochemical significance at shallower depths. The same systems and mechanisms are applicable to the evolution of the global magma ocean and local mantle chambers of magmatism and diamond formation.

中文翻译：

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从下地幔到过渡带的超羽隆起熔体的物理地球化学演化：26 和 20 GPa 的实验

摘要-

MgO-FeO-CaO-SiO ₂液相线结构的彻底转变在地核边界处的含 Mg-Fe 后钙钛矿层 D" 中形成的热化学超级羽流系统在其上升到含 Mg-Fe 桥锰矿下地幔的主体材料至含 Mg-Fe 菱镁矿过渡带期间在 26 和 20 GPa 下通过​​实验和理论研究了穿越 670 公里地震边界。下地幔Mg-Fe-bridgmanite的包晶反应与方铁矿和stishovite的形成，以及Mg-Fe菱镁矿和Mg-Fe akimotoite在过渡带条件下的反应耦合形成方铁矿和stishovite ，控制地幔相应深度的热气压梯度场中超羽流熔体的超基性-基性演化分数。文章还讨论了上地幔和地壳深处超羽岩浆系统的演化物理地球化学转变，以及它们转变为“热场”，橄榄石-玄武岩熔体室由“小羽柱”输送到岩石圈。结果表明, MgO-FeO-CaO-Na 的液相线结构提供了超羽物质以及地幔的超镁铁质-镁铁质演化的物理化学机制和规律。₂ O-Al ₂ O ₃ -SiO ₂系统。在这种情况下，边界系统MgO-FeO-CaO-SiO ₂的作用对于下地幔和过渡带的条件很重要。分级结晶模式促进了残留熔体中 Na ₂ O 和 Al ₂ O ₃浓度的增加及其在较浅深度的物理化学意义。相同的系统和机制适用于全球岩浆海洋的演化以及岩浆作用和钻石形成的局部地幔室。