SOME PROBLEMS OF THE PRECAMBRIAN IN HENAN PROVINCE

The Precambrian, whether the Archean or the Proterozoic, is widey distributed in Henan province, particularly in the Eastern Qinling Mountains area of Western Henan and the Dabie Mountains area in southeastern Henan: it is also exposed sporadically at the southeastern margin of the Taihang Mountains in northern Henan. This paper discusses some problems of the stratigraphic subdivision and correlation, sedimentary formations and volcanic activity, metamorphism and reconstruction of original rocks of the Precambrian. As regards the Archean, the author has analysed the sedimentary formation types, regional metamorphic features and isotopic age data of the Taihua Group in the Xiao Qinhng-Wuyang area, the Dengfeng Group in the Songshan-Jishan area, the Linshan Group in the Jiyuan area and the Zanhuang Group in the Linxian area, and proposed the view that the Dengfeng Group etc. should be dismembered: the low-grade metamorphic （greenschist facies） portion in the upper part should be assigned to the lower Proterozoic, being correlated with the Wutai Group; the Songshan Group in the Songshan Mountains area and the Yinyugou and Tieshanhe Groups in the Jiyuan area should also belong to the lower Proterozoic, being correlated with the Hutuo Group. The middle and upper Proterozoic are comparatively complicated. The Kuanping Group etc. in the southern part are represented by geosynclinal sediments, with their stratigraphic position roughly corresponding to the Changcheng and Jixian Systems. The northern part is marked by platform-type sediments. The Xionger Group （Xiyanghe Group in the lower part） is a volcanic series, corresponding to the Changcheng System; the Gaoshanhe Group is dominated by clastic sediments, corresponding to the middle Proterozoic Nankou System. The Luonan Group and its equivalents in the middle part consist of clasticpelitic-carbonate sediments, rich in stromatolites and microfossil plants, which may be correlated with the Jixian System. The Hongling, Heyao, Luoyukou and Dazhuang Formations of the upper part and the Luanchuan Group of the Luanchuan-Lushi area contain elements of stromatolite assemblage V and microfossils such as red algae, so they should be assigned to the Qingbaikou System. The Taowan Group is tentatively placed at the lower part of the Sinian System, and the tillite of the Luoquan Formation may correlate with the Nantuo Formation.