NEW GEOLOGICAL EVIDENCES FOR THE FORMING AGE OF WUSINIHEI OPHIOLITIC MÉLANGE IN INNER MONGOLIA

Arguments remain on the structure environment and forming age of the Hegenshan-Wusinihei ophiolitic mélange. It used to be considered the ultramafic intrusive rock into the Permian Gegenaobao formation, covered unconformably by Zhesi formation. Since 1980s, with the discovery of radiolarian fossils in associated silicalite, the ophiolitic mélange was dated Early-Middle Devonian or earlier. During field survey, the authors found paleo-weathering crust on the top of the rock series and disconformity between the ophiolitic mélanges and Gegenaobao formation of Late Carboniferous-Early Permian. Therefore the ophiolitic mélange should be formed before Late Carboniferous.