The geology and magmatism of the northern Mariana Trough (NMT) represent a type example for the development of a back-arc basin (BAB). It is a mature spreading center in the south and propagating northward via rifting of arc and rear arc lithosphere in response to trench retreat and overriding plate extension in space and time. It is thus essential to fully characterize its tectonomagmatic processes that are potentially of global significance. For this reason, we carried out a comprehensive geochemical study on basaltic samples (glasses) from the NMT axis from 17 to 23°N by analyzing a full suite of major and trace elements, Sr–Nd–Pb–Hf radiogenic isotopes and stable Fe isotopes. The Fe isotopes, in particular, have the potential to offer novel perspectives beyond the aforementioned geochemical variables. From south to north, the ${\delta }^{56}$Fe of the NMT basalts (NMTB) decrease systematically, varying from a MOR-like value of +0.12‰ to an arc-like value of 0.00‰. Importantly, incompatible element abundances and Sr–Nd–Pb–Hf isotope compositions of the NMTB also show systematic along-latitude variations. Positively correlated with ${\delta }^{56}$Fe, the abundances of fluid-insoluble elements (e.g., Nb, Ta, Zr, Hf, Ti and heavy rare earth elements) show the south-to-north decrease, suggesting that the NMTB ${\delta }^{56}$Fe systematics are inherited from the magma source variation. The source variation is most consistent with an asthenosphere source in the south and progressively more depleted harzburgitic lithosphere source of prior melt depletion towards north. On the other hand, there are scattered but significant enrichment trends towards north in terms of Sr–Nd–Pb–Hf radiogenic isotopes and fluid-soluble incompatible elements (e.g., Ba, Rb, Cs, Th, U, K, Pb, Sr and light rare earth elements), which is consistent with south-to-north increase in slab material (e.g., slab fluids, sediments etc.) contribution. These north-to-south magma source systematics defined by the NMTB can be readily understood as a tectonic response to the back-arc basin development with time from initial arc-magmatism dominated by sub-arc lithospheric mantle melting with significant slab material contributions to back-arc rifting and to back-arc spreading center magmatism characterized by increasing asthenospheric mantle melting, decreasing slab material contribution and diminishing sub-arc lithospheric mantle participation. This tectonic-magma source evolution in space and time is manifested by the snapshot of the NMTB magmatism in terms of the geology, petrology and geochemistry.

The NMTB ${\delta }^{56}$Fe values and fluid-insoluble incompatible element abundances are unaffected by slab materials, but controlled by the harzburgitic residues of previous melt extraction depleted in these elements with low ${\delta }^{56}$Fe at the early arc-magmatism stage in the north and by the asthenosphere of MORB mantle characteristics in the south with well-developed back-arc spreading system. Importantly, these observations affirm the understanding that compositionally depleted and physically buoyant lithosphere is prerequisite as the overriding plate for subduction initiation at its edges.

北马里亚纳海槽 (NMT) 的地质和岩浆作用是弧后盆地 (BAB) 发育的典型例子。它是一个成熟的南部扩张中心，通过弧裂和弧后岩石圈的裂谷向北传播，以响应海沟退缩和超越板块在空间和时间上的伸展。因此，必须充分表征其具有潜在全球意义的构造岩浆过程。出于这个原因，我们通过分析一整套主要和微量元素、Sr-Nd-Pb-Hf 放射性同位素和稳定的 Fe，对 NMT 轴从 17 到 23°N 的玄武岩样品（玻璃）进行了全面的地球化学研究。同位素。特别是 Fe 同位素有可能提供超越上述地球化学变量的新视角。从南到北，${\delta }^{56}$NMT 玄武岩 (NMTB) 的 Fe 有系统地减少，从类似 MOR 的值 +0.12‰ 变化到类似弧形的值 0.00‰。重要的是，NMTB 的不相容元素丰度和 Sr-Nd-Pb-Hf 同位素组成也显示出系统的沿纬度变化。正相关${\delta }^{56}$Fe、流体不溶性元素（如 Nb、Ta、Zr、Hf、Ti 和重稀土元素）的丰度呈南向北下降，表明 NMTB ${\delta }^{56}$Fe 系统学继承自岩浆源变异。源变化与南部的软流圈源和向北逐渐耗尽的哈茨伯里质岩石圈源最一致。另一方面，在 Sr-Nd-Pb-Hf 放射性同位素和流体可溶性不相容元素（例如 Ba、Rb、Cs、Th、U、K、Pb、Sr和轻稀土元素），这与板坯材料（例如板坯流体、沉积物等）贡献的南向北增加一致。这些由 NMTB 定义的从北到南的岩浆源系统可以很容易地理解为对弧后盆地发展的构造响应，随着时间的推移，从以亚弧岩石圈地幔熔融为主的初始弧岩浆活动以及显着的板片材料贡献到背部-弧裂隙和弧后扩张中心岩浆活动，其特征是软流圈地幔熔化增加，板片材料贡献减少和亚弧岩石圈地幔参与减少。NMTB 岩浆活动在地质、岩石学和地球化学方面的快照体现了这种构造-岩浆源在空间和时间上的演化。板片材料贡献减少和亚弧岩石圈地幔参与减少。NMTB 岩浆活动在地质、岩石学和地球化学方面的快照体现了这种构造-岩浆源在空间和时间上的演化。板片材料贡献减少和亚弧岩石圈地幔参与减少。NMTB 岩浆活动在地质、岩石学和地球化学方面的快照体现了这种构造-岩浆源在空间和时间上的演化。

国家交通局 ${\delta }^{56}$Fe 值和流体不溶性不相容元素丰度不受板坯材料的影响，但受先前熔体提取的 harzburgitic 残留物的控制，这些元素在这些元素中含量较低 ${\delta }^{56}$Fe在北部弧岩浆早期和南部MORB地幔特征软流圈发育，弧后扩张系统发育。重要的是，这些观察证实了这样一种理解，即成分耗尽且物理上有浮力的岩石圈是其边缘俯冲开始的压倒性板块的先决条件。