A possible northward subduction in the southwestern Yangtze block during the Rodinia assembly: New constraints from three-dimensional magnetotelluric imaging

The Yangtze block is a crucial component of the Rodinia and Columbia supercontinents, providing insights into their evolutionary history. The newly identified Caiziyuan-Tongan accretionary complex (CAC), situated on the southwestern margin of the Yangtze block, serves as an ideal window for understanding its Precambrian evolution. The exposure of the CAC suggests the presence of an ancient ocean basin that divides the Yangtze block into northern and southern micro-blocks. During the convergence of the Rodinia supercontinent, this ocean basin underwent subduction and eventual closure; however, its associated subduction polarity remains ambiguous. To address this issue, this study employed magnetotelluric in the Caiziyuan-Tongan area. Through three-dimensional inversion, three distinct features were delineated: an upper crustal conductor in the southern CAC, a middle-upper crustal resistor trending stepwise north in the northern CAC, and a middle-lower crustal conductor encompassing the entire area. In conjunction with previously published geological and seismological observations, it is proposed that the first two features may be remnants associated with the northward subduction of the south Yangtze micro-block, while the third feature may indicate the existence of crustal flow related to the collision of the Indo-Asian plate. This finding enhances our understanding of the Precambrian evolution within the Yangtze block and contributes to the reconstruction of paleogeographic frameworks associated with the Rodinia supercontinent.