DataSheet1_The factors controlling along-arc and across-arc variations of primitive arc magma compositions: A global perspective.xlsx

Arc volcanism is a key process influencing Earth’s climate, continental growth, and the formation of mineral deposits. Therefore in this contribution, we have compiled whole-rock geochemistry of frontal arc and rear-/back-arc basalts, crustal thickness, and slab parameters (e.g., slab age, slab dip, and convergence velocity) from global convergent margins to investigate the factors controlling along-arc and across-arc variations. Crustal thickness or lithosphere thickness plays a dominant role in elements immobile in aqueous fluids (e.g., Zr/Yb and Nb/Yb). The effect is imposed through mantle partial melting for both frontal arc and rear-/back-arc rocks. Slab thermal structure also affects these immobile elements and gives rise to along-arc variations. Both slab sediment and altered oceanic crust can melt especially in hot subduction zones which yield across-arc variations (e.g., Nd isotope). Aqueous fluids (represented by element ratios such as Ba/Nb and Sr/Nd) also show across-arc variations as they decrease toward rear-/back-arc. This meanwhile decreases mantle wedge melting as rear-/back-arcs show higher Zr/Yb and Nb/Yb. However, no correlations between aqueous fluids and slab parameters suggest aqueous fluids in arc rocks are controlled by complex processes. We summarize factors such as slab alteration, slab dehydration, and mantle metasomatism might impose an effect on the content of fluid mobile elements in arc rocks.

弧火山作用是影响地球气候、大陆生长以及矿物沉积形成的关键过程。因此，在本项研究中，我们收集了来自全球汇聚边缘的前弧和后弧/后弧玄武岩的全岩地球化学、地壳厚度以及板块参数（例如，板块年龄、板块倾角和汇聚速度），以探究控制弧内和弧间变化的因素。地壳厚度或岩石圈厚度在流体中不活动的元素（例如，Zr/Yb和Nb/Yb）中发挥着主导作用。这种影响是通过板块前弧和后弧岩石的岩浆部分熔融而产生的。板块的热结构也会影响这些不活动的元素，并导致弧内变化。特别是在热俯冲带，板块沉积物和改造过的洋壳可以熔融，从而产生弧间变化（例如，Nd同位素）。以元素比（如Ba/Nb和Sr/Nd）为代表的水流体也表现出弧间变化，因为它们在向后弧/后弧方向递减，这同时减少了地幔楔熔融，因为后弧/后弧显示出更高的Zr/Yb和Nb/Yb。然而，水流体与板块参数之间没有相关性，这表明弧岩中的水流体受复杂过程控制。我们总结，如板块改造、板块脱水以及地幔混染等因素可能对弧岩中流体可动元素的含量产生影响。