<p>The Ordovician-Silurian transition was marked by extensive volcanic activity globally. In South China, intensive volcanism was documented by abundant ash layers in strata, but the origins and tectonic settings of these ashes remain controversial. This study presents the stratigraphic distribution of volcanic ash layers, zircon trace element and Hf isotope data from the Wanhe Section in the southwestern Yangtze Shelf, providing insights into the tectonic setting and the origin of the parent magmas. The results suggest that volcanic ashes in the southwestern Yangtze Shelf primarily originated from arc magmatism in the Wuyi-Yunkai Orogen, with a mixed source from mantle and crust. The findings corroborate the hypothesis that the Late Ordovician–Silurian Wuyi-Yunkai Orogen in South China represents a collisional orogenic belt.</p>