THE ENIGMATIC YINSHAN FOLD-AND-THRUST BELT OF NORTHERN CHINA - NEW VIEWS ON ITS INTRAPLATE CONTRACTIONAL STYLES

The east-to east-northeast-trending Yinshan belt lies within North Chi na, extending westward at least 1100 km from China's eastern coast to Inner Mongolia. This intraplate Jurassic-Cretaceous belt underwent con tractional and normal faulting, folding, and contemporaneous terrestri al sedimentation and magmatism, Current views on its contractional def ormational style favor relatively limited ''thick-skinned'' faulting o f Archean basement and cover units, These views are challenged, howeve r, by recent discoveries in the eastern part of the belt of south-dire cted ductile nappe formation and large-displacement (>40-45 km) ''thin -skinned'' northward thrust faulting, both involving Archean and young er rock units. Collision of the Siberian and North China plates upon c losure of a Jurassic and Early Cretaceous Mongolo-Okhotsk ocean more t han 800-1100 km to the north may have been responsible for Yinshan nor th-south contraction, Some patterns of contraction, e.g., Jurassic-Cre taceous ductile nappe formation, appear to have been influenced by a s uperposed magmatic regime related to westward subduction of a Pacific basin plate beneath the North China plate.