quot;MARGIN: 0cm 0cm 0pt" class=MsoNormal>The late Yanshanian magmatite in the Youjiang Fold Belt of West China is represented by basic-ultrabasic dyke swarms and ultra-acid rock veins. The new data support that the Yanshanian magmatic activity concentrated on 80~100 Ma in the Youjiang Fold Belt and the surrounding area, indicating large scale extension and lithospheric thinning in western quot;urn:schemas-microsoft-com:office:smarttags" />