Crustal three-dimensional architecture of the Yarlung Zangbo magmatic belt: Insights from magnetic inversion

The formation of the Yarlung Zangbo magmatic belt is closely linked to key geological processes, including plates’ collision, continental crustal growth, and crustal extension. Unraveling its deep architecture is therefore crucial for understanding the formation and evolution of the Tibetan Plateau, associated magmatic activity, and resource potential. We employed a mixed Lp-norm regularization inversion technique on high-resolution aeromagnetic data, with deep seismic reflection profiles as the depth reference, to derive a high-resolution crustal three-dimensional susceptibility model beneath the Yarlung Zangbo magmatic belt, revealing its three-dimensional architectural characteristics. Our main findings include: (1) The southern high magnetic anomaly belt is concentrated in the central segment of the southern side of the Yarlung Zangbo suture zone, presenting as a continuous east-west trending anomaly corresponding to the Xigaze mafic-ultramafic ophiolite. The northern high magnetic anomaly belt, located north of the suture, forms a high-amplitude anomaly traversing its eastern and western ends, primarily generated by concealed intermediate-mafic magmatic rocks within the southern Gangdese belt. (2) The Yarlung Zangbo magmatic belt exhibits a clear “north-south zonation and east-west segmentation” architecture. The southern belt, represented by the Xigaze ophiolite, is confined to ~20 km depth in the upper crust and smaller in scale; whereas the northern belt, corresponding to the southern Gangdese magmatic belt, extends to ~30 km depth and is far more extensive. The northern belt exhibits a pronounced east-west segmentation due to along-strike variations in the Indian Plate’s subduction angle and cross-cutting by north-south trending rifts. (3) We therefore propose that the Yarlung Zangbo magmatic belt is a product of the northward subduction of the Neo-Tethys Ocean, with the leading edge of the Indian Plate having already underthrusted beneath the southern Gangdese belt.