A Mid‐Crustal Channel of Positive Radial Anisotropy Beneath the Eastern South China Block From F‐J Multimodal Ambient Noise Tomography

We investigated the crustal radial anisotropy in the eastern South China Block (ESCB) with the F‐J multimodal ambient noise tomography. Well corresponding to widespread mid‐crustal low‐velocity zones in the model, a pronounced mid‐crustal channel of positive radial anisotropy is revealed. In the Cathaysia Block, it may origin from sub‐horizontally aligned quartz induced by extension and correspond to the phase transition of to quartz. In other areas, while, it may be relevant to other well‐aligned minerals. This positive mid‐crustal radial anisotropy channel not only provides the solid evidence for dominative extensional deformation since late Mesozoic, but also may indicate an important detachment surface, contributing much to the early Mesozoic magmatism in the ESCB.