PROGRESSES OF DISTRIBUTION PATTERN, DYNAMICS EVOLUTION AND EXPLORATION RESEARCH ON MESO-NEOPROTEROZIC RIFTS IN THE OLD CRATONS, CHINA

By combining geologic, geophysical and well data, we recognize the Meso-Neoproterozic extensional structures, and composed the isopach maps of the Changchengian, Jixian and Nanhuan systems, based on which the distribution pattern of Meso-Neoproterozic rifting in the Chinese old cratons are analyzed tentatively. The rifting centers are characterized by the filling sequence changing from coarse to fine quickly, especially in the early Mesoproterozic Changcheng period in the North China Craton(NCC), and in the early Neoproterozoic Nanhuan period in the South China Craton(SCC). Isochronal comparisons of filling sequences in rifting stage indicate that Meso-Neoproterozic source rocks in Sichuan basin in the SCC and Ordos basin in the NCC are not well developed for far away from the rifting centers. The distribution pattern, formation time and genetic evolution of the Neoproterozoic rifts are apparent different in the southern and northern Tarim Craton(TC). The rifting in the southern TC were related to the mantle plume originating and radiating from the SCC at about 820Ma, and its initial time was about 20Ma later than that in the SCC, but at least 40Ma earlier than that in the northern TC, where the rifting was mainly related to back-arc expanding by the subduction of Panthalassa around Rodinia supercontinent during the middle Nanhuan period. Moreover, the evolution of Meso-Neoproterozic rift systems controlled the location and sedimentary pattern of the early Cambrian basin. In the TC, the early Cambrian basin apparently inherited the pattern of Nanhuan rift basins. In the NCC, the apparent relocation of rifting centers during Meso-Neoproterozoic controlled the location and transgressive direction of the early Cambrian basin. But for the actualities of these researches, the location, initial time, scale and distribution pattern of the Meso-Neoproterozoic rift systems in these old cratons still have a variety of dynamic interpretation, leading to the different views and conclusions toward the exploration value. The forthcoming studies should focus on the prototype restoration of rift basins which are most related to the formations of Meso-Neoproterozoic source rocks by establishing the sedimentary filling models and comparing their dynamics evolution.