Voluminous Silurian-Devonian granitoids intruded a greywacke-dominated Ordovician accre-tionary wedge in the Chinese Altai.These granitoids are characterized by significant Nd-Hf isotopic decou-pling,the underlying mechanism of which,so far,has been poorly understood.This issue is addressed in this study by the integration of our new and regional published geological and geochemical data.Geological stud-ies indicated a close spatial relationship between the regional anatexis of the Ordovician wedge and the for-mation of the granitoids,which is characterized by a gradual textural evolution from the partial molten Or-dovician wedge sedimentary rocks(the Habahe Group)to the granitoid bodies.Compositionally,these gran-itoids and the Ordovician Habahe Group rocks displayed close geochemical similarities,in the form of arc-like trace elemental signatures as well as comparable Nd isotopic characteristics.Combined with regional available data,we suggest that the Silurian-Devonian granitoids originated from the immature and chemi-cally primitive Habahe Group rocks.Since Nd and Hf isotopic data for the Habahe Group rocks show signif-icant Nd-Hf isotopic decoupling,we propose that the Silurian-Devonian granitoids inherited the Nd and Hf isotopic signatures from their sources,i.e.,the Habahe Group rocks.In other words,the Nd-Hf decoupling in the Habahe Group rocks is the primary causative factor leading to the prevailing Nd-Hf isotopic decoupling of the Silurian-Devonian granitoids in the Chinese Altai.