Microfabrics of chert from Yarlung Zangbo Suture Zone and southern Tibet and its geological implications.
雅鲁藏布江缝合带及藏南地区硅质岩微组构特征及其地质意义

There exist cherts with red, green, black and brown colors in the Yarlung Zangbo Suture Zone and to its south. Quartz is their predominant mineral component, but differs in crystallinity and micro-texture as well as the XRD and FTIR characteristics, depending on samples from different occurrences. The Xialu chert and the Pengcuolin chert are considered of biogenic origin and hydrothermal origin individually. They are different in the evolution of mineral, and microfabrics, which provides possibility to identify the origin of chert. The existence of cristobalite and chalcedony in fossils of the Xialu profile are significant evidence to reconstruct the mineral evolution in biogenic chert. It is shown that the change of microfabric is well associated with the geochemical migration of elements in diagenesis of chert. That the recrystalization process expels the impurity components from SiO2 crystals may be an effective mechanism to enrich trace elements. The microfabrics of chert is a new direction worthy of paying more attention. Based on advanced testing techniques, such as the XRD, FTIR, RAMAN, SEM and EPMA, it provides with rich microfabric information, helping in revealing the diagenesis and orgin of chert as well as the metallogenesis of the Au-Sb-Cs mineralization belt in southern Tibet.