Chert in southern Tibet, China: its field geological fea-tures and related scientific problems

As a prominent type of paleoceanic sediment, cherts occur widely in southern Tibet. According to the spatial and temporal distributions, three chert belts are identified in the Yarlung Zangbo suture and Himalaya sedimentation zone: the Early Cretaceous chert belt in the north of ophiolite of the suture (here referred to as the N-chert belt for short), the Triassic-Cretaceous chert belt in the south of ophiolite (here referred to as the S-chert belt for short) and the Cretaceous chert belt in the Himalaya sedimentation zone (here referred to as the H-chert belt for short). In these chert belts, various petrological characteristics are discriminated, but four types of chert are more reprehensive: massive chert, bedded chert, breccia chert and nodular chert. In the N-chert belt, ophiolite-chert formations are dominant; the volcanic-chert formation and reworked chert formations predominate in the S-chert belt; the H-chert belt is characterized by turbidite-chert formations. The chert in southern Tibet has great scientific value but weak points and problems as well, such as the petrogenesis and microfabric features of chert, information of paleo-oceanic sedimentary events in chert and facies implications of chert for the sedimentary environment.