Detrital Zircon U?Pb Age Distribution and Hf Isotopic Constraints From the Terrigenous Sediments of the Song Chay Suture Zone (NE Vietnam) and Their Paleogeographic Implications on the Eastern Paleo?Tethys Evolution

The location of the suture zone between South China Block (SCB) and Indochina (IB) is disputed. Recently, along Song Chay (Chay river) belt, a mélange was proposed as potential SCB IB. However, provenance age poorly known. In order to better constrain elements forming mélange, nine samples detrital material, one orthogneiss were subjected zircon U-Pb Hf isotope analysis. Detrital zircons from silty matrix record three major Neoproterozoic clusters at 580–650, 700–800, 900–1,000 Ma, which correspond well substratum SCB. Two minor Late Early Paleozoic groups 270–330, 420–500 with mainly negative ?Hf(t) values also recovered. We consider that in derived subducting plate, namely This interpretation supported by occurrence lensoid sandstone blocks, representing SCB, included into mélange. deposition 310 250 Ma. Our results demonstrate an ophiolitic material does not invariably come overriding but onset collision, continental plate may supply terrigenous material.