蓟县早寒武-新元古不整合界面处风化壳碳酸盐碳、氧同位素组成特征

CHARACTERISTICS OF THE C-AND O-ISOTOPIC COMPOSITIONS OF CARBONATES IN THE WEATHERING PROFILE AT THE UNCONFORMABLE BOUNDARY BETWEEN THE EARLY CAMBRIAN AND LATE PROTEROZOIC IN JI COUNTY,NORTH CHINA

由于土壤中有机质降解产生的ＣＯ２ 和淡水成岩作用的影响，在蓟县早寒武世和晚元古代景儿峪组不整合界面处古风化壳中碳酸盐的δ１３Ｃ值和δ１８Ｏ 值明显偏负，从风化壳向下往原岩的方向，δ１３Ｃ和δ１８Ｏ 数值逐渐增加；此外，与风化壳上、下碳酸盐岩地层的δ１３Ｃ和δ１８Ｏ 数值具有明显的差别。上述同位素组成特征可以用于其它古风化壳剖面及地层不整合界面的判识。

Due to the influence of the CO 2 derived from the decay of organic matter in soil and the meteoric diagenesis, δ 13 C and δ 18 O values of the carbonates in the weathering profile at the unconformable boundary between the early Cambrian and the late Proterozoic Jingeryu Formation in Ji County, North China are markedly negative, and increase with the distance to the unaltered rocks downwards. In addition, the C- and O-isotopic composition of the carbonates in the strata above and below the weathering profile are different. The characteristics of the C- and O-isotiopic compositions described above can be applied to the recognition of other paleo-weathering crusts and the stratigraphic unconformable boundary associated with them.