Quantifying Accretion of Intra‐Oceanic Arcs to Continent: Numerical Modeling of Their Crustal Composition and Rheological Property

Abstract Two primary mechanisms responsible for continental crustal growth at convergent margins have been acknowledged, including continental arc magmatism and allochthonous terrane accretion. As such, intra‐oceanic arcs (IOAs), which represent potential accretion terranes, have been regarded as one of the fundamental contributors. It is noted that current IOAs, mainly outcropping in the western Pacific, show remarkable diversity in their crustal composition and rheological properties. However, it remains unclear how the diversity affects the accretion processes of IOAs and further determines their accretion efficiencies. Here, we conducted 2‐D geodynamic modeling to explore these issues. Our models reveal the accretion process and efficiency relying on compositional differentiation and rheological stratification. Specifically, nascent IOAs characterized by a partially molten zone at the level of Moho, where buoyant crust can be separated from dense mantle, result in accretion efficiencies as high as ∼76.4% when slab break‐off took place concurrently. In contrast, mature arcs with cold thermal gradients show a coherent crust‐mantle transition and complete subduction, giving rise to the lowest accretion efficiency. Some of these modeling results align with geophysical observations from modern IOAs, such as the Izu‐Bonin arc and Kyushu‐Palau ridge, which display different accretion processes and efficiencies. The others are likely plausible mirrors of ancient orogenic belts, including the Cenozoic Kohistan arc and the Paleozoic Central Asian Orogenic Belt.