The Yumuquan granitoid complex, located in the south margin of Altyn Tagh, northwestern oft-com:office:smarttags" />China, contain a large number of melanocratic magmatic enclaves (MME). Petrographic and geochemical study indicates that MME is the product of heterogenetic mixing of contemporaneous mantle-derived basic magma and felsic magma under the liquid phase or crystal mesh. The research suggests that large-scale acid magmatic activity took place at ~500 Ma as a result of melting of thickening crust in the southern Altyn Tagh area, accompanied by underplating of mantle-derived mafic magma. The explanation for that is likely related to rising of deep hot mantle, which was triggered by contemporaneous continent subduction.