Generation of continental crust in collision zones reflect the interplay between oceanic subduction and continental collision. The Gangdese continental crust in southern Tibet developed during subduction of the Neo-Tethyan oceanic slab in the Mesozoic prior to reworking during the India-Asia collision in the Cenozoic. Here we show that continental arc magmatism started with fractional crystallization to form cumulates and associated medium-K calc-alkaline suites. This was followed by a period commencing at ~70 Ma dominated by remelting of pre-existing lower crust, producing more potassic compositions. The increased importance of remelting coincides with an acceleration in the convergence rate between India and Asia leading to higher basaltic flow into the Asian lithosphere, followed by convergence deceleration due to slab breakoff, enabling high heat flow and melting of the base of the arc. This two-stage process of accumulation and remelting leads to the chemical maturation of juvenile continental crust in collision zones, strengthening crustal stratification.

碰撞带中大陆地壳的生成反映了大洋俯冲和大陆碰撞之间的相互作用。藏南冈底斯陆壳发育于中生代新特提斯洋板俯冲过程中，在新生代印亚碰撞改造之前。在这里，我们表明大陆弧岩浆作用开始于分级结晶，形成堆积物和相关的中钾钙碱性岩层。随后是一个从 70 Ma 开始的时期，主要是先前存在的下地壳的重熔，产生更多的钾成分。重熔的重要性增加恰逢印度和亚洲之间的收敛速度加快，导致更多的玄武岩流入亚洲岩石圈，随后由于板块断裂导致收敛减速，实现高热流和电弧底部的熔化。这种积累和重熔的两阶段过程导致碰撞带中的幼年大陆地壳化学成熟，加强了地壳分层。