Serial Folding of Partially Molten Crust in the Chinese Altai Driven by Mechanical Anisotropy and Migrating Melt

Abstract The timescales and mechanisms controlling deformation of partially molten, anisotropic crust during continental indentation remain poorly understood. To address this, we present a case study of the southern Chinese Altai fold belts, through an integration of geological observations, geochronological constraints and analog modeling. The region features a series of antiforms formed in response to northward indentation of the East Junggar domain. Vertical felsic dikes transecting the antiform hinges record a progressive south‐to‐north younging in emplacement age (∼300 Ma in the south to ∼270 Ma in the north), mirroring the spatiotemporal pattern observed in host rock 40 Ar/ 39 Ar cooling ages (from ∼285 Ma in the south to ∼220 Ma in the north). Scaled analog experiments employing paraffin wax reproduce this pattern, generating serial folds of decreasing ages and amplitudes away from the indenter, accompanied by development of tensile fractures analogous to the field‐observed felsic dikes. The experiments reveal that pressure gradients associated with serial folds development drove lateral melt transfer toward distal fold regions and maintained elevated thermal gradients over extended timescales. This mechanism explains observed increase in cooling durations—from ∼15 Ma in the southernmost antiforms to ∼50 Ma in the northernmost. We propose an indentation model that reconciles spatiotemporal variations in deformation intensity, melt migration, and thermal evolution in the region. This model provides a robust framework for understanding role of melt and stratified crust in indentation‐dominated orogens in general.